STS Thesis by Hall 2015

Advanced Modular Testing Methods for Integrated Circuits
by
Benjamin Hall, B.S.E.E.
A Thesis
In
Electrical Engineering
Submitted to the Graduate Faculty
of Texas Tech University in
Partial Fulfillment of
the Requirements for
the Degree of
MASTER OF SCIENCE
IN
ELECTRICAL ENGINEERING
Approved
Richard Gale, PhD
Chair of Committee
Brian Nutter, PhD
Mark Sheridan
Dean of the Graduate School
May, 2015

Texas Tech University, Benjamin Hall, May 2015
ii
ACKNOWLEDGMENTS
This thesis may have a single author, but it took an entire team to accomplish
everything I have been able to do. First, I would thank my family. No matter how
difficult life or school got, they always were there to support me and lift me up, not to
mention paying for school. Through my undergrad to my graduate work, my mother,
Hamide Hall, father, Andrew Hall, and Sister Rachel Hall have continued to inspire
me and encourage me to do my best. Without them I do not know where I would be.
Next I would like to thank my committee, Dr. Richard Gale and Dr. Brian
Nutter, for giving me the opportunity to teach this class as my thesis. The advisement
and teachings from Dr. Gale have been invaluable in my studies as a test engineer. I
also appreciate the incredible chance Dr. Nutter took on me by giving me the reins to
my own class.
I would also like to thank the incredible members at National Instruments that
have donated not only equipment, but also their time to helping me in everything
related to the STS. I would especially like to thank Corby Bryan for all the time and
effort he put into training and supporting me ever since I showed any interest in the
semiconductor field.
Finally, I would like to thank the amazing faculty at the Texas Tech University
Department of Electrical and Computer Engineering. Richard Woodcock has been
instrumental in providing me with the equipment needed and lending me his wisdom
from his years in the semiconductor field. Jackie Charlebois and Janet McKelvey have
provided me with the resources needed for my class and have consistently supported
and encouraged me. Not to mention they have been a source of entertainment on
difficult days.
No one person is worth more than the other. All I have accomplished requires
each and every person that I have mentioned, and so many more I did not. Without
any one of them, I could not be where I am and do what I do. Thank you all so much.

iii
TABLE OF CONTENTS
ACKNOWLEDGMENTS....................................................................................................ii
ABSTRACT..................................................................................................................... iv
LIST OF FIGURES ........................................................................................................... v
LIST OF ABBREVIATIONS .............................................................................................. vi
INTRODUCTION OF SEMICONDUCTOR TEST SYSTEM..................................................... 1
1.1 Background of Semiconductor Testing at Texas Tech ................................... 1
1.2 The Semiconductor Testing System................................................................ 1
I. COURSE DEVELOPMENT ............................................................................................. 4
2.1 Motivation....................................................................................................... 4
2.2 Expected Learning Outcomes ......................................................................... 4
II. COURSE CURRICULUM ............................................................................................. 6
3.1 Probability and Statics .................................................................................... 6
3.1.1 Central Limit Theorem............................................................................................6
3.1.2 Process Capability..................................................................................................7
3.1.2 Repeatability and Reproducibility...........................................................................9
3.2 Solid State Physics........................................................................................ 11
3.3 Testing Strategies.......................................................................................... 12
3.3.1 Continuity..............................................................................................................13
3.3.2 Leakage Current...................................................................................................14
3.3.3 Power Consumption .............................................................................................15
3.3.4 Voltage Output High/Voltage Output Low ............................................................15
3.3.5 Functionality .........................................................................................................17
3.3.6 Test Plan Development ........................................................................................17
3.4 Pin Map and Pin Map Application Program Interface.................................. 18
3.4.1 Pin Map Creation..................................................................................................19
3.4.2 Pin Map API Definitions........................................................................................21
3.4.3 Using the Pin Map ................................................................................................25
3.5 TestStand and Semiconductor Multi Test Step............................................. 25
3.5.1 Semiconductor Multi Test.....................................................................................26
IV. COURSE EVAUATION ............................................................................................. 29
4.1 Assessment.................................................................................................... 29
4.1.1 Fall Semester Assessment...................................................................................29
4.1.2 Spring Semester Assessment..............................................................................29
4.2 Instructor Evaluation..................................................................................... 30
4.3 Future Work .................................................................................................. 32
V. CONCLUSION ........................................................................................................... 33
BIBLIOGRAPHY............................................................................................................ 34
A SYLLABUS ................................................................................................................. 35

iv
ABSTRACT
The Program for Semiconductor and Product Engineering (PSPE) at Texas
Tech University strives to prepare students for a job in the semiconductor field. One
crucial partner with PSPE is National Instruments (NI), who has donated a state of the
art Automated Test Equipment (ATE) called the Semiconductor Test System (STS).
This thesis discusses the development of curriculum for ECE 5332: Advanced
Modular Testing Methods for Integrated Circuits, which focuses on training students
on how to properly utilize the STS for their own projects. With the STS becoming an
industry standard, students from Texas Tech will be on the forefront of the advances
being made in the semiconductor field.

v
LIST OF FIGURES
1 Semiconductor Test System [1] .................................................................................. 2
2 Different STS Sizes [1]............................................................................................... 3
3 Ideal Process Capability [2] ........................................................................................ 7
4 Gaussian Distribution with Spec Limits [2]................................................................ 8
5 Guarbanding Test Limits [2]..................................................................................... 10
6 Forward Biased P-N Junction [3].............................................................................. 11
7 Forward Biased P-N Junction [3].............................................................................. 12
8 Continuity on a Single Pin [5]................................................................................... 13
9 Leakage Current Test on SMU [5]............................................................................ 14
10 Power Consumption Test [5] .................................................................................. 15
11 VOH/VOL Test [6] ................................................................................................. 16
12 Overall Pin Map Schema [5]................................................................................... 19
13 DUT Pin Schema [5]............................................................................................... 20
14 Instrument Definition Schema [5]........................................................................... 20
15 Site Definition Schema [5]...................................................................................... 20
16 Pin Connection Schema [5]..................................................................................... 21
17 Pin Map API Location [5]....................................................................................... 22
18 Get All NI-HSDIO Instrument Names VI [5]......................................................... 23
19 Correlation Between Get All NI-HSDIO Instrument Names VI and
Pin Map [5] .......................................................................................... 23
20 Get Pin Names VI [5].............................................................................................. 24
21 Pins To NI-HSDIO Sessions VI [5]........................................................................ 24
22 Publish Data VI [5] ................................................................................................. 24
23 Using the Pin Map API [4] ..................................................................................... 25
24 TestStand Sequence [5]........................................................................................... 26
25 Semiconductor Multi Test Setup [5]....................................................................... 27
26 TestStand Test Limits in Excel [5].......................................................................... 28
27 Semiconductor Multi Test Options Tab [5] ............................................................ 28
28 Course and Instructor Evaluation Average Results ................................................ 31

vi
LIST OF ABBREVIATIONS
ATE – Automated Test Equipment
DUT – Device Under Test
DIO – Digital Input/Output (I/O)
ELO – Expected Learning Outcomes
HSDIO – High Speed Digital Input/Output
NI – National Instruments
PSPE – Program for Semiconductor Product Engineering
PXI – PCI eXtensions for Instrumentation (also used in National Instrument’s part
names)
SMU – Source Measurement Unit
STS – Semiconductor Test System
TSM – TestStand Semiconductor Module
VI – Virtual Instrument

1
CHAPTER I
INTRODUCTION OF SEMICONDUCTOR TEST SYSTEM
1.1 Background of Semiconductor Testing at Texas Tech
The Program for Semiconductor and Product Engineering (PSPE) at Texas Tech
University primarily focuses on instructing students in the different methods for
semiconductor testing. Through this program, students are prepared for an industrial
test or product engineering job. To accomplish this, the students take specific classes
with a focus on semiconductor devices which are associated with a lab component
where students get hands on experience testing various devices utilizing similar
instruments used at semiconductor companies.
National Instruments (NI) is a company that designs and manufactures instruments
for engineers from simple digital multi meters to more complex arbitrary waveform
generators. NI partners with PSPE by providing the laboratory with testing equipment.
The main NI equipment used by the students is the PCI Extensions for Instrumentation
or the PXI. The PXI is a modular device that allows for different types of instruments
to be inserted into a single chaise for different testing purposes. The different
instruments that can be used in the PXI are the same as traditional bench equipment,
such as a Source Measurement Unit (SMU) and a High Speed Digital Input/Output
(HSDIO). Students apply the testing methods discussed in class on a device of their
choice using the PXI.
1.2 The Semiconductor Testing System
The PSPE lab mostly uses bench equipment, but most companies use Automated
Test Equipment (ATE) when it comes to device manufacturing. NI recently started to
shift into the world of semiconductor ATEs in the form of the Semiconductor Test
System (STS). The STS is a system released in August of 2014 that uses one or
multiple PXIs to perform the full spectrum of DC and parametric tests on
semiconductor devices. The system comes packaged with the new Semiconductor

2
Module and PinMap drivers for NI LabVIEW and TestStand, programming languages
used to interface the various equipment used in the PXI. The following figure shows
how the STS incorporates the PXI and LabVIEW.
Figure 1 Semiconductor Test System [1]

3
The STS comes in three different sizes; T1, T2, and T4 (Figure 1.2). The
different sizes dictate the number of PXI chassis that can fit into one system. The
PSPE lab received a T4, which is capable of holding four 18-slot PXI chassis.
Figure 2 Different STS Sizes [1]

4
CHAPTER II
COURSE DEVELOPMENT
2.1 Motivation
Within the PSPE lab, the task of training new students on all the equipment had
been left to former students. Though many of the students were able to learn how to
properly use the equipment, there was still a gap between the fully experienced
students and the ones with limited training. At times, students trusted word of mouth
on the proper method to set up a test, which sometimes meant students were doing an
unnecessary amount of work to accomplish a simple task. One such incident is when a
student requested an updated version of switching software to make 124 connections
on a 12 pin device.
With a brand new system introduced to the lab, a former training class was needed
to bridge the gap and ensure all students were properly trained to use the STS. The
class also prepares students with test methods used in industry allowing them to find a
job in the semiconductor field with companies that use the STS.
2.2 Expected Learning Outcomes
In the process of developing the course, a few items had to be completed. First, the
course objective needed to be identified. When considering the objective, the
motivation was taken into high consideration. The final objective was identified as
“To develop the skills needed for industry test standards”. Next, the syllabus had to be
developed. A copy of the syllabus can be found in Appendix A. When considering the
syllabus, the Expected Learning Outcomes (ELO) were identified as the following:
1. Understand modular testing using the PXI-based Modular test system as
implemented by National Instruments in the STS ATE System Map integrated
circuit functional and system inputs and outputs to test system resources
reconfigurability.

5
2. Reconfigure and sequence test programs in the ATE environment using Test
Stand
3. Demonstrate expert knowledge of LabVIEW and Test Stand
4. Understand limitations of test equipment in terms of repeatability and
reproducibility
5. Perform statistical analysis on results incorporating device variability and test
equipment precision
6. Summarize test results and present process and test capability analyses
Finally, students with a desire to pursue jobs in the semiconductor field had to be
identified. These students had to have a motivation to learn a brand new system from
the ground up and be willing to help their peers. Fortunately, ten students with these
traits were identified for the first offering of the class in the fall 2014 semester. Their
work then motivated a class of thirty-five for the spring 2015 semester.

6
CHAPTER III
COURSE CURRICULUM
3.1 Probability and Statics
The first part of the course focuses on probability and statistics, with a stronger
emphasis on the latter. First, the difference between probability and statics has to be
understood. Probability is using the known population to predict the outcome of a
sample. For example, if a bag of marbles contains three red marbles, two green
marbles, and five blue marbles, probability is used to predict the likelihood that one
red, one green, and one blue marble will be selected. Typically, test engineers do not
rely on probability, and instead utilize statistics.
Statistics differs from probability by using a sample or samples to understand a
population. Going back to the marble example (assuming now the population is
unknown), if single samples of three marbles are chosen and it is one red, one blue,
and one green, then the population can be predicted to be 1/3 red, 1/3 blue, and 1/3
green. Now if the population is known as it was in the probability example, it is clear
the statics are inaccurate. This inaccuracy is due to the small sample size when
considering the total population of ten marbles. The desired sample size brings up a
fundamental theorem when discussing statistics; the Central Limit Theorem.
3.1.1 Central Limit Theorem
The Central Limit Theorem (CLT) states that in the limit of a large number of
samples (< 30), the distribution of a random variable will tend toward a Gaussian
distribution, or bell curve. In the field of test engineering, the number of samples, n, is
the number of measurements taken. Theses measurement values follow the behavior
of a Gaussian and are characterized by two main values, the mean (Formula 3.1) and
standard deviation (Formula 3.2).

7
(1)
(2)
The mean is the average value of all samples. It is the expected and most
probable value whenever a measurement is taken. The standard deviation is the
measurement of the dispersion of the uncertainty of the measured quantity about the
mean. [2]
3.1.2 Process Capability
Statistical analysis used when taking measurements allows for characterization
of device being tested, but in order to fully understand the device, the process in the
manufacturing of the devices must also be characterized. This calculated value is
known as the process capability, or the variation in the process in manufacturing a
product. It is ideally defined as 6σ (± 3σ) so that the maximum number of devices pass
for high production yield.
Figure 3 Ideal Process Capability [2]
The Process Capability can be described with two different factors; the Process
Potential Index and the Process Capability Index. First, an upper and lower spec limit
must be defined (Figure 3.2).

8
Figure 4 Gaussian Distribution with Spec Limits [2]
The Upper Spec Limit (USL) is the maximum acceptable value to allow a
measurement to pass. The Lower Spec Limit (LSL) is the minimum acceptable value
to allow a measurement to pass. With the spec limits defined, the Process Potential
Index, or Cp, can be found with the following formula.
(3)
Cp is the ratio of the range of passing values and the process capability [2].
The larger the Cp, the more stable the process. Any value less than 2 indicates a
process stability issue.
The Process Capability Index, or Cpk, is the process capability with respect to
the centering between specifications limits [2]. When considering only one side of the
specification limits, Cpk can be calculated by the appropriate value in Equation 4. A
Cpk of equal to or greater than 1.5 is needed in order to achieve 6σ.

9
(4)
When given a two sided specification, both values in Equation 4 are calculated
and the lower of the two values is taken or the Cpk can be calculated using Equation 5.
(5)
Where k is calculated using Equation 6 in which T is the target value and µ is
the mean of the distribution. It is important to note that if T=µ, the distribution is
centered on the mean and therefore Cp=Cpk.
3.1.2 Repeatability and Reproducibility
After considering the variation in the process of the device, the variation of the
instruments must be considered. This brings up the difference between accuracy and
precision. The accuracy of an instrument is its ability to get close to the expected
value. The precision of the instrument is its ability to get close to the same values after
multiple measurements. However, the measurements themselves are not necessarily
accurate. The precision of the instrument is also described as its repeatability and
reproducibility.
Repeatability is an instruments ability to take multiple measurements and
return the same result. For example, if the voltage is measured at the output pin of a
device and is found to be 2.5 V, then another five measurements are taken and all are
found to be 2.5 V, then the instrument proves it is repeatability.
Reproducibility is an instruments ability to take measurements under different
conditions and return the same result. Using the output pin example, if the voltage is
again measured the next day and by a different engineer and still returns 2.5 V, then
the instrument proves it is reproducible.
)1( kCC ppk 
 LSLUSL
T
k



5.0

(6)

10
However, no instrument is perfect and therefore the repeatability and
reproducibility must be quantified to understand the capabilities of said instrument.
First, consider the standard deviation of repeatability by taking multiple measurements
from the same pin and same device, as in the above example. Then find the standard
deviation of reproducibility by taking the measurements under different conditions
such as time of day, different instrument, or different engineer. Finally, calculate the
sum of the square root of the squares of both values (Formula 3.5).
(7)
When considering the repeatability of the instrument, it is important to
implement gaurdbanding, which is a technique used to tighten the test limits to
compensate for the uncertainty of the instrument. Gaurdbanding involves defining a
upper and lower test limit that is tighter on the graph (Figure 5) by ±ɛ as defined in
equation 6.
Equation 1 Gaurdband Limits [2]
Figure 5 Guarbanding Test Limits [2]

11
An issue with gaurdbanding is it increases the likelihood of failing good
devices, which is known as a type 1 error. To improve the gaurdband and reduce the
number of type 1 errors, the repeatability and accuracy of each test can be improved,
but this will increase test time. It is important for the engineer to consider the trade
offs of type 1 errors and test time reduction. Typically, a value of 3 or 6 is used for ɛ.
Figure 5 shows upper and lower tests limits that are set by ɛ= 3σ. Using 6σ reduces the
number of passing defective devices, also known as a type 2 error, but may increase
the number of type 1 errors.
3.2 Solid State Physics
When testing semiconductor devices, it is imperative that the physics behind
the device is understood in order to explain why the behavior being observed is
occurring. When developing test methods, it is important to understand how the
electrons flow inside the semiconductor in order to make the proper connections on
the device.
In order to understand the behavior of the electron flow, it is easiest to start
with a simple P-N junction (Figure 3.1), such as a diode. The behavior of the diode
can then be applied to more complex CMOS devices.
Figure 6 Forward Biased P-N Junction [3]

12
First, the I-V curve (Figure 3.2) of diode is studied to understand the proper
flow of current when the device is in different states. The first state is the Forward
Current state in which the device is open allowing current to flow. While in the
Forward Current state, the depletion region of the diode is small. The next state is the
Reverse Blocking state. In this state, the diode is in reverse bias and is blocking
current. The depletion region in the blocking state is large compared to the forward
state. Finally, there is the Reverse Breakdown state. After a threshold of voltage is
reached, the depletion region is too large and current starts to sink through the device.
This is a dangerous state to be in as the current is not limited and can damage the
device.
Figure 7 Forward Biased P-N Junction [3]
3.3 Testing Strategies
Semiconductor devices have characteristics that are described in the device’s
data sheet. All device characteristics can be tested and confirmed with the proper
strategy and equipment. Some test values are not explicitly described in the data sheet,
but the test is still important. One such test is continuity.

13
3.3.1 Continuity
Continuity is thought to be the bread and butter of testing. It is always the first
test performed for several different reasons. First, continuity is used to detect the
electrostatic discharge (ESD) diodes present in all devices. The diodes are imperative
to protect the device from being damaged in case of static discharge. Since it is known
that all devices have ESD protection diodes on each pin, other than VDD and GND,
continuity is also used to ensure there are proper connections between the device
under test (DUT) and the instruments being used.
The diodes presented in the device are connected from a pin on the device to
VDD and one to GND. To perform a continuity test, all pins must first be grounded.
Next, a current is applied to a single pin on the DUT. When detecting the Vcc diode,
current is sourced. This puts the diode connected to GND in reverse bias which blocks
the current and the diode connected to Vcc in forward bias allowing the current to
flow out the power pin to ground. When detecting the GND diode, the current is sunk.
This puts the VDD diode in reverse bias which blocks the current and the diode
connected to GND in forward bias allowing current to flow to ground. When detecting
either diode, the voltage drop is measured, and is typically around 550 and 750 mV.
Figure 8 Continuity on a Single Pin [5]

14
Continuity can be performed on an SMU or HSDIO. The choice of instrument
is up to the engineer and depends on factors such as test time, and the particular device
being tested.
3.3.2 Leakage Current
The input to a CMOS device has high impedance that theoretically allows no
current to flow. In practicality, whenever a voltage is applied, there is a small amount
of current that “leaks” from the pin. Leakage current can detect physical defects, such
as metal filaments that can cause shorts, and an issue in the process of the DUT that
can cause a failure later down the line. This failure is known as infinite mortality [2].
Leakage current can also cause DC offsets which can affect customer applications.
Typically leakage current is less than 1 µA [4]. At times, output pins may have high
impedance and in that case the leakage current should be measured at the output as
well.
When performing a leakage current test, first ensure the DUT is powered on by
connecting VDD to a voltage source. Next, DC voltage is forced on the pin being
tested. The value of the voltage is depends on the type of device being tested. If it is an
analog device, the measurement is taken at the VDD voltage level, and at 0 V. If it is a
digital device, the voltage is set to the input voltage thresholds, VIH and VIL.
Figure 9 Leakage Current Test on SMU [5]

15
Leakage current test can be performed on either an SMU or HSDIO. The
choice of instrument is up to the engineer and depends on factors such as test time, and
the particular device being tested.
3.3.3 Power Consumption
The Power Consumption test is used to detect catastrophic failures in the DUT.
As the name implies, the test measures the DUT’s power consumption under normal
operating conditions. Depending on the DUT, the test may need to be performed
multiple times in the different states of the device.
To perform the Power Consumption test, the device is powered on at the
maximum supply voltage. Then, the current from the VDD pin is measured. This
current value is called IDD. Power consumption is the product of VDD and IDD.
Typically an SMU is used to source VDD and measure IDD. An HSDIO can be used
to change the state of the DUT. The highest value is taken as the maximum power
consumption.
Figure 10 Power Consumption Test [5]
3.3.4 Voltage Output High/Voltage Output Low
When considering device performance, it is important to understand the output
voltage levels to ensure they comply with the system. The Voltage Output High

16
(VOH) is the minimum voltage required for output HI at load current. VOH is
measured when the input pins are set to output a HI. For example, in the case of an
AND gate, if the inputs are both set to 1, the value of VOH is the voltage at the time of
the device outputs a 1. When performing VOH, it is important to have a sinking
current acting as a load. If the pins are unable to source enough current to match or
exceed the sinking current, the output voltage will decrease which indicates poor
output circuitry.
Voltage Output Low (VOL) is the maximum voltage required for an output LO
at load current. VOL is measured when the input pins are set to output a LO. In the
case of an AND gate, if the inputs are both 0, the value of VOL is the voltage at the
time the device output is 0. When performing VOL, it is important to have a constant
current sourcing into the output pin to act as the driving circuitry of another chip. If
the pin is unable to sink more current than is being source, the output voltage will be
significantly higher than 0 V. It is important to note the VOH ≠ VOL in order for the
device to not falsely switch between HIGH and LO with the presence of noise.
Figure 11 VOH/VOL Test [6]
VOH/VOL is tested using an HSDIO to control the DUT inputs and
measure the output voltage. An SMU is used to power the device on and sink or
source current to act as a constant current load for VOH, or another chip’s pin driving

17
circuitry for VOL [6]. When setting the input levels, 3.3 V is used for an input of 1
and 0 V is used for an input of 0. Different values may be specified in the data sheet
and should be used in place of the typical values.
3.3.5 Functionality
Functionality is a fundamental test for all devices. It is important to ensure the
DUT is operating as expected based on the type of device. In other words, the test
ensures an AND gate operates like an AND gate and an ADC operates like an ADC.
To perform a functionality test, the engineer must first understand how the
device is intended to operate. From there, either the HSDIO or SMU is used to force
the operation of the DUT. Typically an SMU is used for analog devices and an
HSDIO is used for digital devices. An SMU should always be used to power on the
device. When measuring the output, a simple indicator can be used to display a HI or
LO for digital chips. For an analog output, the voltage can be measured and displayed
to ensure proper functionality.
3.3.6 Test Plan Development
Before performing any test, a Test Plan should first be developed. The
intention of the Test Plan is to help guide the engineer while performing the tests. The
Test Plan is also used when anyone that is not familiar with the particular device
attempts to performs tests on said device. The Test Plan should include enough
information about the device that anyone could familiarize themselves enough to
perform all the tests described in the Test Plan. The following is a simple breakdown
of the items considered when developing a Test Plan:
• Pick your part

18
• Choose each test to be performed
• Choose number of parts
• Choose number of times to test
• Choose instruments to use
• Defend reasons for each decision
The final item of defending reasons for each decision is essential in the Test
Plan. All choices made have pros and cons. It is important that trade off studies be
made when it comes to considering items like instruments being used and number of
times to perform each test.
3.4 Pin Map and Pin Map Application Program Interface
The Pin Map and Pin Map Application Program Interface (API) are essential
parts of testing using the STS. The Pin Map is used to make connections from the
DUT directly to the instruments being used. The Pin Map is created as an XML file
utilizing a specific schema. Within this file the following are defined [5] (Figure 3.7):
• Tester Resources
• Pins o DUT
• Test cell sites
• Connections between tester resources and DUT pins
• System pins

19
Figure 12 Overall Pin Map Schema [5]
3.4.1 Pin Map Creation
DUT pins and system pins are defined first on the schema (Figure 3.7). Each
pin is defined by its name and associated with a single DUT. The pin name can be
anything, but it is best to use the name in the data sheet to avoid confusion. DUT pins
are associated with each test site where as system pins are associated with all test sites.

20
Figure 13 DUT Pin Schema [5]
Next, instruments are defined on the schema. NI-HSDIO and NI-DCPower
instruments are natively supported by the Pin Map and are automatically defined. First
the type of instrument is defined followed by its name. The name of the instrument
must match the name given in NI-MAX. Finally, the number of channels is defined.
Figure 14 Instrument Definition Schema [5]
After defining the instruments, the site connections are defined. The STS is
capable of 4 sites in total. The site number must start at 0 and continue consecutively
without gaps.
Figure 15 Site Definition Schema [5]

21
Once all parameters are defined, it is time to make the connections of each pin
to the device resource. When defining the connection, start with the pin to connect.
Next, define the site the pin is connected to. Then, define the desired instrument.
Finally, define the instrument channel to complete the pin connection. Ensure all
names and numbers are the same as the definitions previously defined.
Figure 16 Pin Connection Schema [5]
3.4.2 Pin Map API Definitions
The Pin Map API is the connection between the created Pin Map and the test
program in LabVIEW. It can be found under TestStand Semiconductor Module menu
in the Functions tab (Figure 3.11) on the block diagram. The Pin Map API comes
complete with VI’s for NI-HSDIO, NI-DCPower, Radio Frequency instruments, and
Switching instruments. It also includes a “Get Pin Names” VI and a Publish Data VI.
Both are essential in programming the various tests and being able to view the data
from the tests after they are executed.

22
Figure 17 Pin Map API Location [5]
The first VI that will be discussed is the “Get All NI-HSDIO Instrument
Names”. This VI returns all the instrument names as defined in the created Pin Map.
The VI simply takes the input from the Semiconductor Module Context (SMC) and
outputs a string of the instrument names that are then routed to the HSDIO VI.

23
Figure 18 Get All NI-HSDIO Instrument Names VI [5]
Figure 19 Correlation Between Get All NI-HSDIO Instrument Names VI and Pin Map
[5]
The “Get Pin Names” VI (Figure 3.14) takes the SMC and outputs all the pin
names as defined in the Pin Map. There are separate outputs for DUT Pins and System
Pins. The output is a 1D array of strings. This array is then used as the input to the
“Pins to NI-HSDIO (or DCPower) Sessions” (Figure 3.15) to develop the channel list
needed for the HSDIO VI’s.

24
Figure 20 Get Pin Names VI [5]
Figure 21 Pins To NI-HSDIO Sessions VI [5]
The “Publish Data” VI takes an input of the Pin Query Context, which contains
all the pin information from the pin map, and correlates it with the Data In to generate
a report. The Publish Data Id is defined by the engineer and must correspond with the
name in TestStand.
Figure 22 Publish Data VI [5]

25
3.4.3 Using the Pin Map
The Pin Map API allows for several changes when programming a test. First,
the instrument name resource is defined by the Pin Map API and it no longer a control
or constant. Next, the instrument channels no longer are hard defined, but instead
defined by the Pin Map API. The initialization and closing of the HSDIO sessions also
no longer need to be defined as they will be done in a separate VI. Finally, the output
measurement is not a simple indicator, but instead reported using the “Publish Data”
VI with the pin name associated to each value.
Figure 23 Using the Pin Map API [4]
3.5 TestStand and Semiconductor Multi Test Step
TestStand is a sequence editor that is designed to run multiple tests in a
specific order. Within TestStand there are different terms that must be defined. First, a
Step is an operation or test in a test program [5]. A sequence is an order list of steps.
Sequences are run in order to execute the steps in the order the steps are listed.

26
Within the sequence, there are three test groups: Setup, Main, and Cleanup.
Setup contains steps that initialize the instruments that will be used. Main contains all
the steps of the tests that are to be performed. Cleanup contains all steps that reset and
close down all the devices initialized in Setup.
Figure 24 TestStand Sequence [5]
3.5.1 Semiconductor Multi Test
TestStand Semiconductor Module (TSM) adds a new step to TestStand called
the Semiconductor Multi Test (SMT). SMT is used to load LabVIEW VI’s that use the
Pin Map API into TestStand and set up the test. SMT allows for multiple
measurements to be made in a single step, and multisite execution.

27
Figure 25 Semiconductor Multi Test Setup [5]
When setting up tests using SMT, several parameters must be defined. First,
the Test Number and Test Name are defined by the engineer and will appear in the
logs. The name and number do not affect the test, but it should be something that
allows for simple recognition of the test. Then, the Pin field is a drop down menu that
contains all the pins ad defined in the Pin Map. The Published Data Id is the string
from the Publish Data VI and both names must match exactly.
The High Limit and Low Limit are values as defined by the engineer, typically
found in the data sheet. These values are used to determine if the pin pass or failed.
When defining the limits, only put a numerical value into the field. Next, select the
scaling factor from the drop down menu, and finally input the unit being measured.
The limit fields will automatically be populated by the scaling factor and unit.
When defining the test permeates, some engineers may find it more convenient
to use a program such as Microsoft Excel to more quickly define each test. To do so,
simply go to the Semiconductor Module tab at the top of TestStand and select “Export
Test Limits from [Sequence Name]”. From there the engineer can open the test limits
in Excel and edit it as they wish. It is important to stick with the format of the opened
file (Figure 3.19). It is suggested to define at least one limit before exporting the file to
edit. Once complete, select “Import Test Limits to [Sequence name]”

28
Figure 26 TestStand Test Limits in Excel [5]
The Options tab of SMT contains options that allow the engineer to control the
test. First, there is an option to stop performing tests after the first failure. When this
option is enabled, the step will stop after detecting a single failure and continue to the
other steps in the sequence. This option is mostly used for debugging purposes, but
still may be useful when performing tests on devices.
Next, the evaluation comparison mode has several different options to
determine the evaluation of a pass or fail. The multisite option allows for choosing
different multisite performances. “One thread per subsystem” is default and generally
selected. Finally, an option to specify DUT is available that assists with debugging.
Figure 27 Semiconductor Multi Test Options Tab [5]

29
CHAPTER IV
COURSE EVAUATION
4.1 Assessment
Throughout the course of the semester, students were assessed on their
retention of the material discussed in class. Several forms of assessment were used to
ensure students were meeting the Expected Learning Outcomes (ELO). The fall and
Spring semester varied slightly based on the number of students. In the fall, only ten
students were enrolled allowing the assessments to be more project based. In the
spring, thirty-five students enrolled making the assessment more exam and quiz based.
Both semesters had the same final project.
4.1.1 Fall Semester Assessment
In the fall 2014 semester, ten students were enrolled in the course. With that
being the case, the ELO’s were met using a project based approach. First, an exam to
demonstrate the ability to design tests in LabVIEW using NI-HSDIO to meet ELO’s 1,
3, 4, and 5. The average for the first exam was a 90. A final project was assigned to
use the STS ATE to perform all tests discussed in class using TestStand, TSM, and
LabVIEW on a logic gate. The final exam was designed to meet ELO’s 1-6. The
average of the final exam was an 87. Two Quizzes were also given to meet ELO’s 5
and 6. The class average of both quizzes was a 95. The final average in the class was a
94, with all students earning an A for the semester.
4.1.2 Spring Semester Assessment
The spring semester had thirty-five students enrolled in the course. After the
lengthy amount of time to arrange the first exam project for only ten students, it was
clear another assessment model had to be developed. First, two quizzes and a written
exam were administered to meet ELO’s 4-6. The class average for the written exam
was an 87. The class average of both quizzes was an 86. After the first exam, quizzes

30
were given daily in class to meet ELO’s 1-3. Because the material was brand new to
the students, the quiz answers were discussed in class and the student received a
participation grade. The same final project was assigned to the spring semester class to
meet ELO’s 1-6. The project is still in works and the results are pending.
4.2 Instructor Evaluation
In the fall semester, students enrolled in the course took a course and instructor
evaluation survey. The students were was three questions:
1. The course objective were specified and followed by the instructor
2. Overall, the instructor was an effective teacher
3. Overall, this course was a valuable learning experience.
The students were to answer the above questions on a scale of 1 through 5, 1
being the Strongly Disagree and 5 being Strongly Agree. Table 4.1 has the average
results from all ten students for the three questions.
Table 1 Course and Instructor Evaluation Average Results
Course and Instructor
Evaluations
Average Score from 10
Students
1. The course objective were
specified and followed by the instructor
4: Agree
2. Overall, the instructor was an
effective teacher
4: Agree
3. Overall, this course was a
valuable learning experience
4: Agree

31
Figure 28 Course and Instructor Evaluation Average Results
Some students from the fall made suggestions that assisted in shifting the focus
of the material in the spring semester. First, a student suggested better training on the
brand new equipment. For that, students in the spring have been trained on the
equipment in the lab one on one after arranging a time with the instructor. There was
also a stronger emphasis on how to properly use the STS in class with several
demonstrations. Another student suggested the instructor needed to improve on
teaching capabilities. To meet that, the instructor met with several colleagues and
advisors to receive advice. The instructor also met with former students in order to
better structure the class based on their feedback of what material they felt needed
more attention. This helped the instructor organize the class better and be more
effective in the classroom.
0
1
2
3
4
5
6
7
Strongly Agree Agree Neutral Disagree Strongly
Disagree
Question 1
Question 2
Question 3

32
4.3 Future Work
The course had proven quite popular to students wishing to learn advanced
methods in semiconductor testing and it continually requested to be taught another
semester since some students were unable to take it when offered. Currently, a student
from the fall 2014 semester is tutoring the class. His knowledge and ability to assist
the students in the spring 2015 semester had prepared him to take over instructor the
course in the fall 2015 semester. The course has also brought more attention to the
structure of the semiconductor testing curriculum at Texas Tech. Students are
requesting a stronger emphasis on equipment training mixed with testing theory. The
PSPE faculty and senior students are in works to incorporate the hands on training into
the curriculum.

33
CHAPTER V
CONCLUSION
The technological world is always changing, and it is the goal of academia to
prepare students for all the changes. With the introduction of brand new state of the art
equipment, it is the responsibility of instructors to introduce and train students so they
can be prepared for new industry standards. The STS is just one piece of technology
students will be tasked to use when they move onto their jobs into the semiconductor
field. The main focus of the PSPE is to bridge the gap between academia and industry.
It is also the focus of this course to give students a chance to learn new equipment
being quickly adopted by their field, and give them a leg up in the job market. One
student from the fall 2014 semester landed an interview based on their work with the
STS.
The curriculum of semiconductor testing at Texas Tech will continue to grow
with the changing world. The STS and Advanced Modular testing course are just one
step in the advancement of technological knowledge that will stimulate the student-
industry partnership.

34
BIBLIOGRAPHY
[1] “NI Semiconductor Test Systems – National Instruments.” [Online] Available:
http://www.ni.com/pdf/niweek/us/STS_Flyer.pdf
[2] G. Roberts, M. Burns, et al. An Introduction to Mixed-Signal IC Test &
Measurement, 2nd ed. New York: Oxford University Press, 2012.
[3] “Analogue electronics/pn junctions” [Online] Available:
http://en.wikibooks.org/wiki/Analogue_Electronics/pn_Junctions
[4] “Diodes-SparkFun.” [Online] Available:
https://learn.sparkfun.com/tutorials/diodes/real-diode-characteristics
[5] NI STS 2013 Training Material[Proprietary]
[6] “Output Voltage Level Testing Technical Details (VOH,VOL) - National
Instruments.” [Online] Avaliable: http://www.ni.com/example/30948/en/

35
APPENDIX A
SYLLABUS

36

37

38

STS Thesis by Hall 2015

More Related Content

Viewers also liked

Similar to STS Thesis by Hall 2015

More from Hank Lydick

STS Thesis by Hall 2015