This presentation present about TCAD, Simulation and Modeling, Lambda Design Rule, Stick Diagram, Floor planning, Sheet resistance concept.

1. Presentation - 2
TALLINN UNIVERSITY OF TECHNOLOGY
Course : Communicative Electronics
Subject : Microelectronics (IED3030)
Harish Kumar Singh – 177319IVEM

2. Topics
1. TCAD
2. Simulation and Modeling
3. Lambda Design Rule
4. Stick Diagram
5. Floor planning
6. Sheet resistance concept

3. Technology Computer Aided Design
(TCAD)
Simulation Tool for semiconductor processing, device
operation and interconnect characterization for
technology development and manufacturing.
Process TCAD : Modelling of the fabrication(such
as diffusion, lithography, deposition, etching,
oxidation, mechanical stress etc)
Device TCAD : Modelling of the device operation
(electrical, thermal, optical and mechanical
behaviour of semiconductor devices)

4. Example
• Process simulations
Simulate doping profiles obtained by
specific processing techniques,
calibrate the model with experimental
data and then optimize the process to
obtain the desired profile.
• Device simulations
Simulate the output
characteristics of a MOSFET
device and calibrate the device
architecture to fine-tune the
device performance.

5. Benefits of TCAD
• Optimize process modules and integration by fully
exploring the process parameter space while reducing the
number of experimental wafers and development cycles.
• Capture and analyze the impact of process variation on
device performance, and to increase process
capability, robustness and yield.
• Use deep physical approach to predictive accuracy for a
device, which reduce the costly and time-consuming
test wafer runs when developing and characterizing a
new semiconductor device or technology.
• Latest TCAD tools provide powerful GUI-driven (2D,
3D) simulation environment for managing simulation
tasks and analyzing simulation results

6. Providers & Applications
Proprietary TCAD Providers :
Synopsys, Silvaco, Crosslight, Cogenda Software, Global
TCAD Solutions and Tiberlab
Open Source Providers:
GSS, Archimedes, Aeneas, NanoTCAD ViDES, DEVSIM and
GENIUS
Applications:
CMOS, power, memory, image sensors, solar cells, and
analog/RF devices fabrication

7. Simulation and Modeling
A model is a representation of some system.
Physical modelling : For example virtual model of MOS
transistor.
Mathematical modelling: Use mathematical formula
to simulate I-V curve of MOS transistor
Process modelling : Process to be followed for
fabricate of MOS transistor
Simulation is the operation of the model of the system
to evaluate the performance of the system. It allows you
to optimize the system, to prevent failure and to adjust
any parameters within the system being investigated.
For example simulation of MOS transistor at different
temperature.

8. Lambda Design Rule
Distance by which a geometrical feature or any one
layer may stay from any other geometrical feature
on the same layer or any other layer. All processing
factors are included plus a safety margin.
λ used to prevent problems due to mask
misalignment or exposure & development
variations on every feature, which otherwise could
lead to :
• over-diffusion • over-etching etc

9. Lambda Rule
• Define rule for minimum channel length
• Minimum distance rules between device
layers used during layout, e.g.,
 polysilicon <-> metal
 metal <-> metal
 diffusion <-> diffusion and
 minimum layer overlaps etc
• Layout design rule checker (DRC)
automatically verifies that no design rules
have been broken

10. Basic Rule

11. Basic Rule

12. Basic Rule
All device mask dimensions are based on multiples of λ, e.g., polysilicon
minimum width = 2λ . Minimum metal to metal spacing = 3λ

13. Stick Diagram

14. Stick Diagram

15. Stick Diagram
• VLSI design aims to translate circuit
concepts onto silicon
• Stick diagrams are a means of
capturing topography and layer
information using simple diagrams
• Stick diagram convey layer information
through colour codes
• Acts as interface between symbolic
circuit and the actual layout

16. Stick Diagram : Cartoon
• Does show
– All components
– Components relative placements
– Help to plan layout and routing
• Does NOT show
– Exact placement of components
– Transistor sizes
– Wire lengths, wire widths, tub boundaries
– Any other low level details such as parasitics

17. Stick Diagram : Notations

18. Stick Diagram : Notations
Rule 1: Two sticks of same type cross
each other represent electrical
isolation.
Rule 2: Two or more stick of different
type cross each other without contact
represent electrical contact.
Rule 3: Poly crosses diffusion
represents a transistor .
Rule 4: In CMOS a demarcation line
drawn to avoid touching of p-diff and
n-diff.

19. Stick Diagram : Use
• Easy approach to perform simple CMOS
circuit layout
• Helps to plan physical design before using
the actual CAD tools
• Complicated wiring of gates and cells id
often easier to visualize
• Crossover(such as Metal1-Metal2) are easy
to plan
• Help to visualize the signal flow in complex
netwoks

20. Floor planning
• Find approximate locations of a set of
modules that need to be placed on a
layout surface
- Available region typically
considered rectangular
- Modules are also typically
rectangular in shape, but there can
be exceptions (e.g. L-shaped
modules)

21. Chip Planning Example
Chip Planning = Floor planning + I/O Pads +
Power/Grd Planning

22. Problem Definition

23. Example

24. Wire Length and Cost

25. Dead space

26. Representation of Floor plan

27. Sheet Resistance
• The sheet resistance is a measure of
resistance of thin films that have a
uniform thickness.
• It is commonly used to characterize materials
made by semiconductor doping, metal
deposition, resistive paste printing and glass
coating. Ex: doped semiconductor regions
(silicon or polysilicon ) and resistors.
• Sheet resistance is applicable to two-
dimensional systems where the thin film is
considered to be a two- dimensional entity.

28. Consider a uniform slab of conducting material of
resistivity ρ of width W, thickness t and length
between faces A&B is L. as shown in figure.
Consider L and W are equal
Where Rs is ohm per square or sheet resistance.
From the above equation Rs is independent of the
area of square. The resistance of the MOS layers
depend on the thickness and the resistivity of the
material of the layer

29. Thank You

30. Bibliography
• https://www.synopsys.com/silicon/tcad.html
• http://www.micro.deis.unibo.it/~rudan/MATERIALE_D
IDATTICO/diapositive/TCAD/01_TCAD_laboratory_Intr
oduction_GBB_20150223H1655.pdf
• http://www.powershow.com/view/3d1881-
ZmU3M/Stick_Diagrams_by_S_N_Bhat_Lecturer_Dept
_of_E_C_Engg_M_I_T_Manipal_Sn_bhat_manipal_edu_
msnbhat_yahoo_com_powerpoint_ppt_presentation
• http://snsct.snscourseware.org/files/CW_590aadeda
36f2/Stick%20diagram.pdf
• https://www.youtube.com/watch?v=TYy2o8Qy4TY