TYSTAR 16

Non-MOS Poly-Silicon LPCVD Furnace

(tystar16)

 

1.0         Title

TYSTAR 16 Non-MOS Poly-Silicon LPCVD Furnace

2.0         Purpose

Tystar16 is used to deposit poly-crystalline silicon film, doped with phosphorus or un-doped. It can process both 4 and 6 inch wafers. It can also be used to deposit undoped amorphous silicon film.

3.0         Scope

This chapter covers the general furnace description of TYSTAR 16, TYCOM and furnace operation procedure, which includes process recipe loading, wafer loading/unloading, process status monitor, labmember level problem diagnosis, and wafer cleaning requirements.

4.0         Applicable Documents

Revision History

4.1         TYTAN Diffusion Furnace System Instruction Manual (copy in Office).

4.2         TYCOM 9900 Microprocessor Control System Instruction Manual (copy in Office)

4.3         Material Safety Data Sheets for Silane (SiH4), Phosphine (PH3), and Nitrogen (N2) (copy in Lobby).

5.0         Definitions & Process Terminology

5.1         Non-MOS Furnace: The wafers processed in this kind of furnaces may contain materials (thin film, dopant, or contaminant) that are not compatible with the MOS processes. If CMOS devices are processed in a Non-MOS furnace, the electric performance of the devices may be changed. Wafers with metal films can be processed in Non-MOS furnaces only with Microlab manager’s permission.

5.2         LPCVD: Low Pressure Chemical Vapor Deposition. The film deposition process is controlled by the migration and reaction of the process gas on the wafer surfaces at low pressure, usually at hundreds of milli-torr pressure. This method generates good film property and uniformity.

5.3         Poly-Silicon: The film consists of silicon grains with different crystal orientation.

5.4         Amorphous-Silicon: The film contains random silicon atoms without crystal orientation.

6.0         Safety

Follow general safety guidelines in the lab as well as the specific safety rules as per follow:

6.1         Electric Shock Hazard: TYSTAR furnaces utilize high electric power (high amperages) to generate heat.  Do not open the side panels or touch the high power electrical parts in the furnace cabinet.

6.2         Chemical Hazard: Silane and Phosphine gases used in the deposition process are flammable and/or toxic. Proper purge procedure should be followed if the process is aborted due to equipment failure or human mistake, when the process gases are flowing.

6.3         Burn Hazard. Cantilevers, boats, and wafers coming out of the furnace are very hot.  Wear face shield when loading/unloading wafers. Proceed with caution. Avoid touching of any furnace quartz ware to prevent burning of your hands and contamination of the furnace. No flammable chemical, especially organic solvents, should be in the load station when the tube is open.

6.4        All new recipes must be checked by the process staff, before they can be used on any TYSTAR furnaces. Customized recipes should be stored on the labmember’s diskette, not the standard diskettes.

7.0         Statistical/Process Data

7.1         Microlab web page.

7.2         Problem and comment section under equipment section of the wand.

7.3        Enable message for individual TYSTAR furnace.

8.0        Available Process, Gases, Process Notes

8.1         Wafer cleaning requirements before loading into TYSTAR furnaces

8.1.1          Photo-resist on the wafer surface must be stripped first in PRS3000 bath of Sink5, Technics-c, or Matrix, then cleaned in Sink8 piranha bath. New wafers can skip this step.

8.1.2          All wafers then cleaned in Sink6 piranha bath. Wafers just unloaded from an MOS furnace can be loaded into another furnace without further cleaning. Wafers just unloaded from a Non-MOS furnace can be loaded into another Non-MOS furnace too.

8.1.3          Transfer clean wafers into a blue wafer transfer box. Do not take the TEFLON cassette with wafers to the furnace directly to prevent contamination of the cassette.

Available Processes

8.2         Phosphorus doped poly-silicon LPCVD.

8.3         Low phosphorus doped poly-silicon LPCVD for stress adjustment.

8.4         Un-doped poly-silicon LPCVD.

8.5         Un-doped amorphous silicon LPCCD.

Available Gases

8.6         Nitrogen (N2): Used to purge out room air after wafer loading and process gases after deposition. It is also used to vent the tube up to the atmosphere pressure, and process pressure control.

8.7         Silane (SiH4): Source of the silicon in the film.

8.8         Phosphine (PH3): Used for phosphorus doping. The phosphine gas used in the Microlab is a 50% SiH4/ 50%PH3 mixture, for all the furnaces. There are two MFC’s installed in TYSTAR16: PH3HI (0-10sccm), PH3LO (0-3sccm).

Process Notes

8.9         TYSTAR16 is a non-MOS furnace that is mainly used for MEMS devices. The electric property of the silicon film deposited may be compromised by the contaminants form previous runs. If you are making MOS devices, you should use TYSTAR 10 instead.

8.10      All the standard poly-silicon processes run at 615ºC, and the standby at 550ºC. The maximum operating temperature is 650ºC and the minimum is 450ºC.

8.11      To process glass wafers, you should wait the furnace to cool down below 550ºC after you load the appropriate recipe. It allows the furnace to cool down uniformly.

8.12      Do not leave the furnace door open for over 30 minutes. It will generate a large temperature gradient that may crack the quartz tube. If you need more time, e.g. you drop a wafer and need to get another one, you should close the door manually, then abort the recipe. When you are ready again, re-start the recipe again.

Processing Glass/pyrex Substrate in Tystar16 Furnace (below 550ºC)

Undoped amorphous poly can be deposited on borofloat glass/Pyrex substrates in Tystar16 in a designate boat. The Loading temperature is often set at the same temperature as deposition temperature at or below 550ºC, which is below both the softening point (821ºC) and annealing point (560ºC) of the borofloat glass. Do not exceed process temperatures of 550ºC, and use the dedicated borofloat glass boat at the station to process your glass/pyrex wafers. Replace one of the boats in the tube with the designated borofloat boat for your process.

16FUPLYA recipe can be used at typical deposition temperature of about 525ºC to deposit the amorphous poly film. This can produce 700  - 1300 Å/hr of amorphous poly film (according to previous labmember reports). Please, refer to MOD 31 in Chapter 1.3 of the lab manual for more detailed information on Pyrex/borofloat glass cleaning/processing in the VLSI area of the Microlab.

9.0        Overall Furnace Operation

9.1         General TYSTAR Furnace Information

The TYSTAR Furnace consists of three basic modules: Load Station Module, Furnace Module, and Source Cabinet Module. Microlab labmembers have access to the Load Station Module in the clean room area. The other two are in the Tylan service chase. Only Microlab staff with proper training have access to these two modules due to potential hazards.

The Load Station Module houses a laminar flow unit with HEPA filter for clean air distribution. A Boat Loader Unit opens/closes the furnace door and pulls-out/pushes-in the cantilevers with wafer boats sitting on top. The operation can be automatically controlled by a process recipe, or manually using the ROP (see section 9.3).

The Furnace Module consists of a quartz process tube, thermal couples, and heating elements. It is divided into three zones: Load, Center, and Source. The temperature is controlled through a PID electronic board (DTC). All the control parameters can be set in the process recipe. The volume of the quartz tube is approximately 45 liters. The process gas flows into the tube from the Source end and vented through the holes on the Load end.

The Source Cabinet Module contains several Mass Flow Controllers (MFC) that regulate the process gas flows. An electronic gas control system MFS 460 coordinates all the MFC and interlocks for safe operation.

9.2         TYCOM Terminal

The TYCOM Terminal controls/monitors all the TYSTAR Furnace operations. It consists of a CPU with two floppy disk drives, a CRT monitor and a keyboard. Disk drive #2, on the right side, is used for viewing and loading of recipes. The auxiliary drive is used for copying diskettes.  The standard recipes for an individual furnace are stored on a floppy diskette labeled with the furnace name, e.g. TYSTAR1. The floppy disk used has a special format. Please ask staff if you need one to store your customized recipes.

9.2.1          TYCOM Commands

TYCOM CPU only recognizes CAPITAL letters only. You can use the numerical key pad on the right hand side of the keyboard to enter numbers. However, do not use the [Enter] key on the numerical key pad. It will cause error when loading a recipe.

Commands

Function

Example

DI DI

Displays the recipe directory of the diskette in Drive #2

 

DI RE “recipe name”

Displays the content of a recipe on the diskette in Drive #2

DI RE 16SDPLYA

LO “recipe name” “#”

Load a recipe to a TYSTAR furnace

LO 16SUPLYA 16

DI ST “#”

Displays current status of a TYSTAR furnace (see section 9.2.2)

DI ST 16

DI DE “#”

Displays the system configuration of a TYSTAR furnace

DI DE 16

DI AL “#”

Displays previous process alarms of a TYSTAR furnace

DI AL 16

9.2.2          Display Furnace Status

 When you use DI ST commands, the CRT monitor displays the status of the TYSTAR furnace. This information is very important, especially for equipment problem diagnosis. The following example is used to explain the information labmembers should know. The furnace status to be displayed is TYSTAR16 with recipe 2STNBYA loaded but not running (Idle state).

07/05/02

16:30:32

 

 

 

 

 

 

 

 

*=DISABLED

 

 

 

 

 

 

 

TUBE

STATUS

PROCID

 

ET

 

STEP

TIME-TO-GO

STEP ET

016

READY

16STNBYA

 

00:00:00

 

0000

00:00:00

00:00:00

 

 

 

 

 

 

 

 

 

 

OUTPUTS

RELAYOUT

RELAYIN

INPUTS

 

 

N2VAC =

0.0

N2VAC =

OFF

DNTLK =

OFF

TEMPL =

H

  752.3

0880

N2BKFL =

250.0

N2BKFL = 

ON

ANTLK =

OFF

TEMPC =

G

751.0

0726

SIH4 =

.0

SIH4 =

OFF

BNTLK =

OFF

TEMPS =

L

747.2

0744

PH3HI =

.0

PH3HI =

OFF

VNTLK =

OFF

CALIBL =

 

752.1

 

PH3LO =

.0

PH3LO =

OFF

GNTLK =

OFF

CALIBC =

 

750.9

 

PRCPR =

.0

PRCPR =

OFF

CCIN6 =

ON

CALIBS =

 

747.3

 

SPEED =

.0

VACUUM =

ON

BPOUT =

OFF

 

 

 

 

ANAO8 =

.0

CCOUT8 =

OFF

N2PRSAL =

OFF

 

 

 

 

TEMPL =

600.0

PREPH3 =

OFF

 

 

N2VAC =

G

249.9

 

TEMPC =

600.0

PRESPA =

OFF

 

 

N2BKFL =

G

0.0

 

TEMPS =

600.0

CCOUT11 =

OFF

 

 

SIH4 =

G

0.2

 

 

 

CCOUT12 =

OFF

 

 

PH3HI =

G

0.0

 

 

 

CCOUT13 =

OFF

 

 

PH3LO =

G

0.0

 

 

 

DTCENA =

ON

 

 

PRCPR =

G

246.3

 

 

 

LOAD =

OFF

 

 

 

 

 

 

 

 

UNLOAD =

OFF

 

 

 

 

 

 

The following sections explain the above display in details.

9.2.2.1    Display Header (first 4 rows)

The first row shows the current Data and Time stored in TYCOM CPU. The second row indicates that any INPUT or OUTPUT followed by an * on the display is disabled. None of the INPUT and OUTPUT of TYSTAR 1-4 is disabled.

On the third and fourth lines:

TUBE - - - - - - - - - -  TYSTAR furnace #.

STATUS - - - - - - - -  READY (idle, recipe loaded but not running)

                                                      RUN     (recipe running)

                                                      HOLD   (recipe hold at certain step)

                                                      STNBY (no recipe loaded, indicate power failure)

PROCID - - - - - - - -  Recipe ID, stated in the first line of the recipe, usually the same as the recipe file name.

ET - - - - - - - - - - - - Total time elapsed since the process starts.

STEP - - - - - - - - - -  Current recipe step.

TIME-TO-GO - - - - - Time left to run in the current step.

STEP ET - - - - - - - - Time elapsed in the current step.

9.2.2.2    OUTPUTS – Process parameter settings sent from TYCOM CPU to a TYSTAR furnace.

N2VAC, N2BKFL, SIH4, etc - - - -   Process gas flow settings

SPEED - - - - - - - - - - - - - - - - - - - Boat pull-out/push-in speed settings.

TEMPL, TEMPC, TEMPS - - - - - -     Temperature settings for Load, Center, and Source Zone

ANAO8 - - - - - - - - - - - - - - - - - - - -   Available for future use.

9.2.2.3    RELAYOUT – Commands sent from TYCOM to al TYSTAR furnace to turn on/off Contact Closure Switches.

N2VAC, N2BKFL, SIH4, etc - - -  Turn on/off the NUPRO valves of individual process gas. If off, no process gas flows regardless what the flow setting is.

PRCPR  - - - - - - - - - - - - - - - - - - Turns on/off the process pressure control. PRCPR and N2VAC can not be turned on at the same time. When PRCPR is turned on, N2VAC becomes a slavery for the pressure control.

VACUUM - - - - - - - - - - - - - - - - -     Open/close the