Microfabrication Recipes and Notes

This page includes

Most of this data was collected by members of the UW MEMS laboratory in the EE microfabrication laboratory or the WTC cleanroom. You are encouraged to contribute to this collection. Here is a Word template for recipes.

Recipes

Recipe Autor Date Comments & Links
       

Lithography

       
Oriel Aligner - avoid accidential exposures Sarah McQuaide July 2003  
AZ1512 - resist thickness approx - 1µm Udo Lang April 2000 With oven, time: 1:45 hours
AZ1512 - resist thickness approx - 1 mic. Yael Hanein April 2000 With hot plate, time 15 min
AZ 4620, single layer , thickness - 12 mic for RIE etching Udo Lang April 2000  
AZ4620 two layers for "deep" RIE etching Udo Lang April 2000  
       

RIE

       
Spin-on glass etching Xiaorong Xiong October 2000  
Nitride etching Udo Lang June 2000  
Etching of resist/organic material leftovers Yael Hanein June 2000  
SF6 for silicon etching Udo Lang June 2000  
       

Wet Etching

       
Cr mask for deep KOH etching Yael Hanein May 2000  
       

General

       
Pt electroplating Yael Hanein June 2000  
Circuit board M. Terry May 2000  
       

Masks

A few useful tips for designing and working with masks. Although some of the ideas below seem somewhat trivial, all have been overseen by many users :

  • When designing your mask keep in mind what is the printing/writing resolution. If you use the UW Publication Services you are currently limited to 14000dpi.
  • If you use dark field masks by generating the negative image of your design, remember that your alignment marks will be reversed, too. Keep in mind that a black mask with transparent crosses, for example, is extremely inconvenient to align. Design your alignment marks in a way that they will eventually appear as black features on transparent background.
  • With any CAD software you use, always design your mask with as many building blocks as possible. Use these blocks as references in other blocks. Avoid as much as possible the use of "COPY".
  • When trying to do alignment, make sure that both lamps of the mask aligner are working. Work with the split field mode of the microscope, this will enable you to do easy alignment over an entire wafer.

Etch Rates

Material Etchant Rate Conditions Author Date Comments & Links
             
Si KOH     Udo Lang  

relatively low selectivity between Si and oxide;
high selectivity between Si and nitride;
selectivity depends on T;
verify solution concentration before use

Si 100  

2.2µm/h;
9µm/h;
55µm/h;

45%, 30°;
45%, 50°;
45%, 80°
Udo Lang    
Si 100   3.3µm/h;
13µm/h;
83µm/h
25%, 30°;
25%, 50°;
25%, 80°
Udo Lang    
Si 110   3.3µm/h;
13.6µm/h;
85µm/h
45%, 30°;
45%, 50°;
45%, 80°
Udo Lang   very rough surface
             
Si EDP ~60µm/h 110° Yael Hanein   high selectivity between Si and oxide;
excellent for deep etching with oxide as a mask (through holes);
very toxic
             
SiO2 BOE 50nm/min 10:1      
Nitride BOE 200nm/h 10:1 Yael Hanein    
             
Au Au etchant ~700Å/min        
             
Al HNA (20:3:77 acetic:nitric:phosphoric acid) ~1µm/h T > 35° Joel Reiter    
             

Color of SiO2 and Si3N4 Films

From Physics of Semiconductor Devices by S. M. Sze.

Color SiO2 Thickness Range (µm) Si3N4 Thickness Range (µm)
     
Silicon
0-0.027
0-0.02
Brown
0.027-0.053
0.02-0.04
Golden brown
0.053-0.073
0.04-0.055
Red
0.073-0.097
0.055-0.073
Deep blue
0.097-0.10
0.073-0.77
Blue
0.10-0.12
0.077-0.093
Pale blue
0.12-0.13
0.093-0.10
Very pale blue
0.13-0.15
0.10-0.11
Silicon
0.15-0.16
0.11-0.12
Light yellow
0.16-0.17
0.12-0.13
Yellow
0.17-0.20
0.13-0.15
Orange red
0.20-0.24
0.15-0.18
Red
0.24-0.25
0.18-0.19
Dark red
0.25-0.28
0.19-0.21
Blue
0.28-0.31
0.21-0.23
Blue green
0.31-0.33
0.23-0.25
Light green
0.33-0.37
0.25-0.28
Orange yellow
0.37-0.40
0.28-0.30
Red
0.40-0.44
0.30-0.33
     


© Karl F. Böhringer, Department of Electrical Engineering, Box 352500, Seattle, WA 98195-2500, USA