Photolithography Machine Control System

RIT Computer Engineering Senior Design Project

Ben Conrad February 13, 2004 Mark Edwards

User Interface• Seven Executable Commands

– DEV#1: Dispense developer solution– PREWET: Dispense de-ionized(DI) water– RINSE: Dispenses DI water to clean wafer– N2: Dispenses Stream of Nitrogen (N2)– SPIN: Spin Dry the wafer– WAIT: Static delay option.– END PGM: End the program

• Parameters– Time: .1 – 999.9 sec. (.1 second resolution)– Speed: 0-7,999 RPM

How It Works

The Solitec Model 8360 spin casting and temperature controlled positive develop bake system is used in the photolithography process of making microelectronic circuits on silicon wafers. It automates the process of applying photoresist and baking a wafer, and is fully programmable through user input. This is accomplished through a keypad and LCD display. The user enters a series of operations with parameters on the keypad, thus forming “recipes” for the processing of particular sets of wafers. The main modules visible to the user are the digital display and input keypad, the input wafer cartridge, the chemical application spin chuck, the bake chuck, and the output wafer cartridge.

How We Did It

Parts Used in System I/O Circuit• (1) HCS12 Microcontroller

• (4) 74F675A 16-bit Serial In, Parallel Out Shift Registers

• (2) 74F676 16-bit Parallel In, Serial Out Shift Registers

• (2) LM741 Operational Amplifiers

• (2) DAC0800 8-bit Digital to Analog Converters

Design Goals•Meet customer requirements – system able to hold 10 “recipes” for wafer processing, control wafer speed from 0-8000RPM, timing accurate to 0.1 seconds.

•Allow use on coat and develop tracks – provide recipes general enough for controller to function on either machine

•Save RIT money – our total cost is $500 compared to $25,000 from industry – 98% savings

•Future Expandability

- Software handles extra sensors which may be added later

- System I/O hardware provides twice the I/O needed allowing expansion to machine with more processing stations

Solitec 8360 in RIT’s Fab

Spin Chuck  Vacuum Tube

Bake Chuck  Vacuum Tube

Wafer Output Cartridge

(25 wafers)

Wafer Input Cartridge

(25 wafers)

Top Down View

¾ Overhead View

Technological Arts’ HSC12 Board

Over 4000 lines of HCS12 assembly code was written to operate both the system and UI HCS12s.

The software controlled the inputs and outputs

diagrammed (left) by expanding the HCS12’s

input and output capabilities through the use of shift registers (below). Dual DAC’s provided analog

signals which controlled the motor speed.

Coating the wafer with photoresist or developing it by wet etching off layers after masking is an essential step in the process of creating microchips. In either track, the control system loads a wafer from the input cartridge, then moves it to the spin chuck. Once on the spin chuck, a vacuum is applied. The spin chuck is then accelerated to anywhere from 0-8000RPM while various chemicals are applied to the wafer. The 8360 has the ability to dispense a main chemical (developer), de-ionized water, and an air stream of nitrogen. When finished, the system moves the wafer to the bake chuck, where the wafer is heated for a variable, user-defined length of time. Finally, the system moves the wafer to the output cartridge, and the wafer is ready to be processed by another system.

B0

HC12- A3

B1

16 Bits to Cable (16-31)

8 Bits to DAC1

A4

Serial Out to HC12

B2

HC12- B4

U5

74F676

4

5

2

6

1

78910111314151617181920212223

SI

MODE

CLK

SO

CS

P0P1P2P3P4P5P6P7P8P9

P10P11P12P13P14P15

HC12-A116 Bits to Cable (0-15)

HC12- B2

B3

HC12- A7

8 Bits to DAC0

B4

Serial Out to HC12

B5

HC12-A2

HC12-A5

U3

74F675A

4

3

5

7891011131415

1617181920212223

6

1

2

SI

R/W

STCP

Q0Q1Q2Q3Q4Q5Q6Q7

Q8Q9

Q10Q11Q12Q13Q14Q15

SO

CS

SHCP

Ben Conrad, Mark Edwards

A3

A6

Schematic: Shift Register to HC12 Connections

16 input Bits (0-15)

HC12- A6

32 Input Bits

A7

U2

74F675A

4

3

5

7891011131415

1617181920212223

6

1

2

SI

R/W

STCP

Q0Q1Q2Q3Q4Q5Q6Q7

Q8Q9

Q10Q11Q12Q13Q14Q15

SO

CS

SHCP

U2

74F675A

4

3

5

7891011131415

1617181920212223

6

1

2

SI

R/W

STCP

Q0Q1Q2Q3Q4Q5Q6Q7

Q8Q9

Q10Q11Q12Q13Q14Q15

SO

CS

SHCP

HC12-A4

16 input Bits (16-31)

A2

HC12- B3

A1

U6

74F676

4

5

2

6

1

78910111314151617181920212223

SI

MODE

CLK

SO

CS

P0P1P2P3P4P5P6P7P8P9

P10P11P12P13P14P15

HC12-A0A0

U2

74F675A

4

3

5

7891011131415

1617181920212223

6

1

2

SI

R/W

STCP

Q0Q1Q2Q3Q4Q5Q6Q7

Q8Q9

Q10Q11Q12Q13Q14Q15

SO

CS

SHCP

HC12- B5

HC12 - P7

16 Bits to Cable (32-47)

HC12 - P6

48 Output Bits

A5

Part Price ($) Quantity Cost40x4 LCD Module w/ Backlight 29 1 294x4 Matrix Keypad 20 1 20

MAX232 (Serial Driver) 4 2 88MHz Crystal 1 2 2

20 Key Encoder 7 1 7

16-Bit Par. In Serial out Shift Register 5 2 1016-Bit Serial in Par. Out Shift Register 9 4 36Misc (wire, connectors, etc) 25 1 25

Misc Chips (DAC0800, LM741, etc) 1 10 10M68HC12 Microcontroller Dev Board. 180 2 360

TOTAL $507

Cost Breakdown

A collaborative effort between RIT Computer Engineering and Microelectronic Engineering Special thanks to: John C. Nash, Dr. Alan D. Raisanen, Thomas J. Grimsley, and Dr. Roy Czernikowski

The top-down diagram shows the wafer input and wafer output cartridges located on opposite ends of the line while the spin chuck and bake chuck are in the center. Vacuum tubes hold the wafers onto each chuck as they are processed. The gray rectangle represents a tray which is able to move between the input and output cartridge for wafer loading and unloading, respectively.

The 3/4th overhead view diagram shows the holes cut into the system tray to allow each chuck to move up or down to allow the tray to move to one of its three positions (at input, center, at output.) Conveyer belts move the wafer from the input assembly and to the output assembly. The black squares represent three switches used for position sensing on the system tray and two vacuum sensors on the vacuum tubes to determine if a wafer is currently making contact with the tube (and thus on the tube’s chuck.)

Control System Block Diagram

System I/O Hardware

Standby M ode 1 2 3 ESC

M ode:_ 4 5 6 SS

1 2 3 7 8 9 NXT

Run Program Service < 0 > ENT

Rec#00 1 2 3 ESC

4 5 6 SS

7 8 9 NXT

< 0 > ENT

Status: RunningBake Time: 000.0 Motor Speed: 0000

Funct: Step: 1 1 2 3 ESC

Rec #: 4 5 6 SS

1 2 3 4 5 6 7 8 9 NXT

DEV PREWET RINSE N2 SPIN WAIT < 0 > ENT

Time:Speed:

1 2 3 ESC

4 5 6 SS

1 2 3 7 8 9 NXT

Manual Op Status Vie w I/O < 0 > ENT

Standby Mode

Run Mode

Program Mode

Status Mode

UI Controller

The Team

Digital Controller – HCS12Analog I/O to Motor Board

Motor Speed In

Next Speed Out

Motor Accel Out

Digital Inputs

Position/Level Switch Sensors

Hot Plate at Temp.

No more wafers to processWafer sender ready

Wafer receiver cassette fullWafer receiver ready

Digital OutputsStore finished wafer

Load next incoming wafer

Solenoid Outputs

Servo BoardMotor RPMDetect

Switch Sensors

Entrance Wafer

Cassette Holder

Exit Wafer Cassette Holder

Solenoids

Hot Plate

HC11 SPI Interface

ClkSDI/MISO

SDO/MOSI

LCD Panel

Keypad

HCS 12