The document describes the design of a chemical vapor deposition (CVD) system. It discusses the working principles of CVD, the key components of a CVD system including the reactor chamber, gas distribution system, heating elements and vacuum system. It outlines the functional, performance and reliability requirements for the CVD tool, as well as environmental health and safety considerations. The document also discusses the product lifecycle and costs associated with developing, operating and disposing of the CVD system.

1. CHEMICAL VAPOUR DEPOSITION: SYSTEM
DESIGN DOCUMENT
Aun Ahsan
DCU
April 2016

2. TABLE OF CONTENTS
1. Introduction..............................................................................................................................................................3
2. Working principle of CVD....................................................................................................................................3
2.1 Operation and components of a CVD system...............................................................................4
Works Cited...................................................................................................................................................................... 10

3. 1. INTRODUCTION
The basics of Chemical Vapour Deposition (CVD) are deposition of a film by initiating a chemical
reaction inside a chamber filled with suitable reagents that are vapourized in an inert carrier
gas. The energy supplied by the chamber surroundings causes the diffused reagents to react and
form a desired material film on the target surface [1]. CVD is used to produce high quality, high
performance materials, most commonly used in semiconductor industry to produce thin films.
CVD is split into several types of CVD processes including Atmospheric pressure CVD (APCVD),
Low pressure CVD (LPCVD) and Plasma enhanced CVD (PECVD). LPCVD and PECVD are the
most important CVD processes in microelectromechanical systems.
2. WORKING PRINCIPLE OF CVD
In the LPCVD process the wafers enter the quartz tube through the load doors and are held
vertically on the wafer boat. The quartz tube is placed on the 3-zone furnaces which start off at a
low pressure of around 0.1Pa indicated by the pressure sensor. The tube is then heated to the
desired temperature from 600-660C̊ (for compounds like SiH4), the working gas is inserted into
the tube at the pressure between 10-1000P [2]. This gas reacts with the substrate and creates a
solid phase material on the substrate; the excess material is pumped out of the tube. The
deposition rate is determined by the temperature and the pressure. The limiting factor is the
temperatures in the type of materials used, with higher temperatures the uniformity increases
with less defects present.
Figure 1 Typical Hot-Wall LPCVD reactor [3]

4. 2.1 OPERATION AND COMPONENTS OF A CVD SYSTEM
Figure 2 a schematic side elevational view of a chemical vapour deposition system [4]
With reference to Figure 2 the CVD system consists of housing 12, the substrates (G) enter
through 30 and exits through 32. The substrates are introduced in the deposition chamber 14
defined by the lower and upper housing portions 16 and 18 that have a horizontal planar
junction 20 with each other. A seal assembly 22 extends between the lower and the upper
housing portions. The G substrate moves along the direction C on a roll conveyor 24 [4], located
within the deposition chamber and chemical vapour distributor 26 includes the distributor
plenums 28 that are located in the deposition chamber 14 to provide chemical vapour
deposition of coating on the conveyed substrate. Referencing both Figure 2 and Figure 4 the
chemical vapour deposition system 10 includes as oven 78 contained in the housing. The oven
has opposite lateral slots 80 through which the roll conveyor 24 and the chemical vapour
distributor 26 project through the heated oven. The oven has a insulated design and is mounted
on the housing 12 [4]. Inside the oven heaters 84 are extended along the length of the housing,
electrical connectors 8 connect the heaters 84 in banks a, b, c, d and e to control temperature
differentials of the substrate as well as controlling the heating of their upper and lower surfaces.
Collection of broken glass/ substrate below the conveyor rolls 24. A vacuum source 38 is
included in the chemical vapour deposition system as illustrated by Figure 3 to draw a vacuum
in the deposition chamber 14. A hydraulic cylinder mounted on the seal flanges 62 and movable
clamp 74 that engages the upper seal flange 64 and it is secured by one thread connector 76 to
a piston connecting rod of the hydraulic cylinder.

5. Figure 3 cross section of seal assembly
Figure 4 cross sectional view through the deposition system [4]
Figure 5 Operation block for CVD system

6. 3. STAKEHOLDERS
Stakeholders are defined as Customers and other interested parties, that could benefit from the
product [5]. This system is designed for 300mm ,32nm feature size. The table represents the
customers and their expectations and requirements for the product.
Customers Requirements and expectations
Semiconductor manufacturing companies
like intel, Samsung, Texas Instruments,
Toshiba, Sandisk, and Qualcom.
A state of the art CVD tool designed for the
semiconductor industry, increased throughput
with multiple wafers, competitive pricing, and
reducing cost of ownership overall.
Process Engineers Ease of use with UI based software, accurate
distribution of chemical vapour. Sensors for
accurate pressure and temperature control.
Process Technicians Easy maintenance, reduction of downtime and
ease of collecting defective and broken
substrates through the use of a screen.
Project Managers Accurate use of Chemical vapour, minimising
the deposition of vapour on reactor walls
through targeted distributors. Reduction in
visible defects and morphing.
Research and development Provided support for 300nm and 450nm wafer
sizes.
Below is the table of interested parties who are in the industry and are connected or concerned
about the system [5].
Other Parties Requirements and expectations
Safety Officers Materials used in the construction of the
system are per safety requirements.
Environment Adequate control of dangerous chemicals and
gases and including of the annular radiation
shield. Leakage detection system in place.
Clean room environment standard
conformant.
Quality Engineers CVD system conforms with the industry
standard with less defects and good control of
pressure and temperature.
4. TECHNICAL REQUIREMENTS
4.1 FUNCTIONAL REQUIREMENTS
The following are the functional requirements for optimal operation.
 Conveyor will transfer the multiple wafers into position of the distributors inside the
housing
 The clamps will be secured and Hydraulic cylinder activated
 Vacuum will be drawn in the deposition chamber
 Activation of elongated heaters to heat the substrate to optimal temperature
 Chemical vapour distributors engaged when position of wafers is aligned.

7.  When prescribed chemical vapour has been issued, the by products are removed using
gas flow.
 Deactivation of the Hydraulic cylinder and seals
 The wafers are moved on the conveyor through the housing exit.
4.2 PERFORMANCE REQUIREMENTS
The system confers to the following performance requirements [6] [7]:
 The Equipment will require 415±10% V, 3-Phase, with Frequency 20±2% Hz
 10 wafers will be deposited simultaneously, with deposition rates of 50-60 microns /
hour
 The CVD reactor shall have liquid cooling to provide a skin temperature of 25-30 C̊ at
peak temperatures
 Coating uniformity will be ±10
 The vacuum system shall have two pumps, each pump will be capable of handling entire
throughput in case of failure
4.3 RELIABILITY REQUIREMENTS
The system shall have the following reliability requirements [6]:
 The tool shall have 95% availability
 MTBF of > 500 hours
 MTTR of < 8 hours
 The productivity scalar in relation to the current system will be > 1
 The foot print scalar in relation the current system will be = 1.
4.4 ENVIRONMENTAL HEALTH AND SAFETY REQUIREMENTS
The following requirements are met by the system [6] [7]:
 Pressure sensor for sensing leakage is provided.
 Emergency procedures and well documented and documents are provided
 Audible and visual alarm to indicate malfunctions.
 Tool complies with the SEMI S2 and S8 ESH requirements.

8. 5. PRODUCT BREAKDOWN STRUCTURE
6. EQUIPMENT LIFECYCLE AND COSTS
The product is classified according to the different stages of the products life i.e. the production,
the use and disposal of the product.
Tool Production:
 Concept designed with stakeholders expectations realised.
 Engineered per safety and production standards and prototype is produced.
 Tested and calibrated
 Customers must send coated examples of the substrate for further testing
 High costs with low usage.
Took Maintenance:
 Regular optimisation for increased yield
 Maintenance during downtime and breakdowns.
 Moderate costs with maintenance and changing components
Tool End of life:
 Dismantling and disposing of equipment parts
 Reusable components should be refurbished and re-used
 Costs are minimal
User
Interface
Enter/exit
doors
Conveyor
Rolls
Distributors
Vacuum
System
Seals/Clamp
Vacuum
Pumps
Hydraulic
cylinder
Pressure
Sensor
Oven
System
Elongated
Heaters
Heating
Element
Temp
sensor
Exhaust
filtering
Valves
PID
Controller

9. 7. ENVIRONMENTAL IMPACT
The environmental impacts of the CVD process mainly come from the chemicals used for the
coating of the substrate.

10. WORKS CITED
[1] P. ahern, Lecture notes EE541 nano and microelectropncis device manufacturing, DCU,
2016.
[2] T. M. a. M. P. Ronald Curley, “Low-pressure CVD and Plasma-Enhanced CVD,” University of
Maryland, Maryland, 2012.
[3] “MEMS Thin Film Deposition Processes,” memsnet, 2014. [Online]. Available:
https://www.memsnet.org/mems/processes/deposition.html. [Accessed 18 04 2016].
[4] J. B. F. J. E. H. Gary T. Faykosh, “Chemical Vapour deposition system”. United States Patent US
6,719,848 B2, 13 04 2004.
[5] NASA, “NASA Systems Engineering Handbook,” Rev1, 2007.
[6] ISMI, “Equipment Performance Metrics,” SEMATECH, Austin, TX.
[7] D. M. R. LAB, “DMLR specification for CVD,” DMLR, Hydrabad.