Acid Bench 02

Acid Bench 02
Equipment Details
Technology	Wet chemical processing
Materials Restriction	CMOS Clean
Sample Size	4" and 6" wafers
Chemicals Used	BHF Phosphoric acid Hydrofluoric acid Nanostrip Sulfuric acid Hydrogen peroxide
Equipment Manual
Overview	System Overview
Operating Procedure	SOP
Supported Processes	Supported Processes
User Processes	[]
Maintenance	[]

Acid Bench 02 is used for acid processing on CMOS-clean wafers for a variety of purposes. The Buffered HF (BHF) tank and dilute HF tanks (users set the concentration) are generally used for wet etching of silicon dioxide selective to silicon. The hot phosphoric tank is generally used for selective wet etching of silicon nitride selective to silicon dioxide and/or silicon. The Nanostrip tank is generally used for wafer cleaning and/or removal of positive photoresist from silicon wafers.

Announcements

• Please do not change nanostrip between 9:30-11:00 on Mondays. There are 2 scheduled tank changes in the lab during that time, and doing an extra tank will overwhelm the Acid Waste Neutralization (AWN) system.

System Overview

Chemicals Allowed

• Buffered HF (BHF)
• Phosphoric acid
• Nanostrip
• Hydrofluoric acid (HF)
• Sulfuric acid (H₂SO₄)
• Hydrogen peroxide (H₂O₂)
• Hydrochloric acid (HCl)

Safety

Proper PPE for this bench are apron, face shield, trionic gloves and safety glasses

There is a separate apron available for use when doing hot phosphoric processing - this apron is more heat resistant than the standard apron

Warning:

You must use the buddy system for all chemical processing. No processing if you are alone in the lab. If the yellow warning lights are on it means that there are 2 or 1 people in the lab.

Working with chemicals can be very dangerous. Chemicals used at this bench are some of the most hazardous in the lab. To minimize the chance of accident, make sure you always:

• Wear proper PPE at the bench. This includes apron, faceshield, and Trionic gloves
• LNF Glove Policy
• Know the properties and hazards of chemicals you are working with. If you don’t know, find out by reading about them or asking staff.
• Plan the details of your process. Before you start working, plan what quantities of chemicals and sample carriers you will use. Plan how you will rinse your sample and what you will do with any waste generated. Make sure you know how the controllers work.
• Only process 4” and 6” wafers.
• Do not use this bench without proper training
• Waste from this bench goes into the LNF's acid waste neutralization system and then to the city sewers. No solvents can be used or disposed of in this bench.

Hardware Details

Acid Bench 02 consists of:

• Recirculating Buffered HF (BHF) tank
• Heated bath for etching with Phosphoric acid at 165 degrees Celsius for nitride etching
• Heated bath for Nanostrip cleaning and photoresist removal
• Unheated chemical bath for Hydrofluoric acid (HF) Etching
• A Quick Dump Rinse ("QDR") for rinsing wafers
• A Bottle wash station for rinsing empty acid bottles before disposal.

Substrate Requirements

• 4 inch and 6 inch wafers
• Silicon Substrates ONLY

Material Restrictions

The Acid Bench 02 is designated as a CMOS Clean class tool. Below is a list of approved materials for the tool. Approved means the material is allowed in the tool under normal circumstances. If a material is not listed, please create a helpdesk ticket or email info@lnf.umich.edu for any material requests or questions.

Approved materials

Supported Processes

LNF Standard Processes in this bench

• Buffered HF (BHF) for etching silicon dioxide
• Hydrofluoric acid (HF) for etching silicon dioxide
• Hot Phosphoric acid ("Hot Phos") for etching silicon nitride
• Nanostrip for cleaning wafers and stripping approved positive photoresists
• Piranha Etch for cleaning silicon wafers

Acid 02 Supported Processes Allowed

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Standard Operating Procedure

Acid 02 Standard Operating Procedure

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Checkout Procedure

1. Take the General Wet Bench Training, if you haven't already.
2. Read through this page and the Standard Operating Procedure above.
3. Fill out Acid Bench Process Request Form. You will need to fill this out for each bench you plan on using.
4. Practice with your mentor or another authorized user until you are comfortable with tool operation.
   1. If your mentor is not an authorized user or you do not know of an authorized user that can train you, proceed to the next step.
5. Score 100% on this quiz: Acid Bench 02 Training Quiz.
6. Open a helpdesk ticket and request a checkout.
7. A tool engineer will schedule a time for checkout.

Maintenance

• Buffered HF is changed on an as-needed basis when crystallization is observed or when etch rate changes considerably.
• Hot Phosphoric, and HF are generally user-maintained baths. Please fill out helpdesk ticket if you need training or assistance.
• Nano-strip Tank Change process can be found here and user done. Remember that if the nanostrip is over 1 week old, you should drain, rinse, and refill the tank.