CMOS metal etch wet bench:
The CMOS metal bench is used for etching Si wafers which may contain standard
metal films like aluminum (Al), gold (Au), and also used for chrome etching.
Piranha cleaning for metal based substrate can also be done in this bench.
Cleaning standard and substrate:
• Bath1- 9:1:H2SO4:H2O2
• Bath2- Aluminum Etching 19:1:4: H3PO4 : HNO3 : H2O
• Bath3-Gold Etching 4gm: 1gm: 40ml K2I2 : I2 :H20
• Bath4- Chrome etching (Preprepared).
• Bath5-Oxide Etching 50:1: H2O : HF
Performance of the tool:
What the tool can do?
The CMOS metal bench has 5 different baths for the processes.
• Bath1- 9:1:H2SO4:H2O2 (Piranha cleaning)
• Bath2- Aluminum Etching 19:1:4: H3PO4 : HNO3 : H2O
• Bath3-Gold Etching 4gm: 1gm: 40ml K2I2 : I2 :H20
• Bath4- Chrome etching.
• Bath5-Oxide Etching 50:1: H2O : HF
Etch rates
Material
Aluminum
Gold
Chrome
Etchant
19:1:4: H3PO4 : HNO3 :
H2O
4gm: 1gm: 40ml K2I2 : I2
:H20
Chrome etchant
Etch rate
100nm/min
200nm/min
1.5nm/sec
The bench also contains a dump rinser, dryer, DI hand sprayer and N2 gun.
System overview:
This wet bench is equipped with polypropylene bath for Al, Au, Cr
Quartz bath for Piranha cleaning of wafers (with photoresists and metal
contamination) with temperature controller.
Polypropylene bath for Dilute HF.
Dump rinser and spin-rinse dryer for 2”, 3”, 4” and 6” wafers.
Quick dump rinser (QDR):
Bench is fitted with a QDR the purpose of which is to rapidly wash the surface of
the water and leave the wafer in a clean condition.
How to use:
 At rest the QDR will be partly full of water when the lid is opened and
wafers are placed inside close the lid and press the start button, this water
will dump and the bath rapidly fills using the top sprays and the bottom fill.
 When full the water flow will stop and the unit will dump its contents.
 A new cycle of filling will commence, the number of cycles can be set on
the dump cycle counter.
 After completion of the cycle the light will flash and warning sound will be
audible until the wafers are removed.
Spinner:
The bench is fitted with a spinner suitable for drying a single wafer and a holder
that will accept wafers of 2”-6”.
How to operate the spinner:
 N2 fault indicates that there is no nitrogen pressure.
 The heater fault indicates that there is an over temperature situation with the
heater.
 The process timer will stop the spinner after the pre-set time has elapsed.
 Lift the lid
 Insert the wafer
 Close the lid
 Turn safety cam such that flat faces the front
 Press start/stop switch(spinner will run for pre-set time and nitrogen purge
will be on)
 End of cycle/dry complete light will illuminate, the spinner start stop will
flash and there will be an audible alarm.
Chemical hazards:
Sulphuric acid, hydrogen peroxide, orthophosphoric acid and Nitric are used at this
wet bench. You must read the Material Safety Data Sheets for these chemicals and
understand safe chemical handling procedures before working at this bench.
The primary hazard classification for the chemical mixtures used at this bench are
For 90% sulphuric/peroxide - Corrosive, oxidizer, air/water reactive.
For orthophosphoric acid - Corrosive.
For Nitric acid - Corrosive, oxidizer.
For Iodine – Corrosive, toxic
Chemical frequency:
Bath1- Piranha should be changed once in 5 days
Bath2- Al etching once the etch rate goes down
Bath3- Au etching once the rate goes down
Bath4- Cr etching once the etch rate goes down.
CMOS general solvent (lift- off) wet
bench:
The CMOS general solvent (lift off) wet bench is used for cleaning up to 6 inch
silicon wafers, or the cleaning of masks after the lithography process using acetone
and IPA.
Cleaning standard and substrate:
Acetone and IPA solutions are put into the respective baths (no ratios) for silicon
wafers and for mask cleaning.
Performance of the tool:
What the tool can do?
The CMOS general solvent (lift-off) wet bench has 2 different baths for the processes.
Bath1 - Silicon and Mask cleaning.
Bath2 - IPA for Silicon and Mask cleaning.
System overview:
This wet bench is equipped with steel bath for acetone cleaning.
Steel bath for IPA/methanol cleaning.
Dump rinse and spin-rinse dryer for 2”-6” wafers.
Quick dump rinser (QDR):
Bench is fitted with a QDR the purpose of which is to rapidly wash the surface of
the water and leave the wafer in a clean condition.
How to use:
 At rest the QDR will be partly full of water when the lid is opened and
wafers are placed inside close the lid and press the start button, this water
will dump and the bath rapidly fills using the top sprays and the bottom fill.
 When full the water flow will stop and the unit will dump its contents.
 A new cycle of filling will commence, the number of cycles can be set on
the dump cycle counter.
 After completion of the cycle the light will flash and warning sound will be
audible until the wafers are removed.
Spinner:
The bench is fitted with a spinner suitable for drying a single wafer and a holder
that will accept wafers of 2”-6”.
How to operate the spinner:
 N2 fault indicates that there is no nitrogen pressure.
 The heater fault indicates that there is an over temperature situation with the
heater.
 The process timer will stop the spinner after the pre-set time has elapsed.
 Lift the lid
 Insert the wafer
 Close the lid
 Turn safety cam such that flat faces the front
 Press start/stop switch(spinner will run for pre-set time and nitrogen purge
will be on)
 End of cycle/dry complete light will illuminate, the spinner start stop will
flash and there will be an audible alarm.
Chemical hazards:
Acetone and IPA are used at this wet bench. You must read the Material Safety
Data Sheets for these chemicals and understand safe chemical handling procedures
before working at this bench.
The primary hazard classification for the chemical used at this bench are:
Acetone - Highly flammable, irritant.
IPA- Highly flammable, irritant.
Controllers:
• This wet bench is fitted with timer controller.
•
Users are allowed to set the process duration.
Disposal of Solvents:
• IPA and acetone is disposed into the storage can below by unscrewing the
cap.
•
Check to make sure that the disposal can is not full before opening the cap.