[mems-talk] AZ5214E image reversal resist conditions

[Yue Mun Pun, Jeffrey]

Hi,
I have tried the following with AZ5214E on SiO2 wafers:
a.  Positive image using AZ5214E by spin coating at 3500rpm, exposed to a dose of 74mJ/cm2 at i-line UV, develop 20s using pure AZ Developer (not AZ351 nor AZ400K developer).  The results show that the small images of 26umex was over-exposed even though the thickness of the resist was 1.47-1.49um which is near to 1.50um.

b.  Negative (image reversed) using AZ5214E by spin coating at 3500rpm, exposed to a dose of 74mJ/cm2 i-line UV, developed 20s using pure AZ developer (not AZ351 nor AZ400K Developer).  The results also show images were overexposed in the features of small dimensions of 26um.  Thickness of resist was slightly thinner at 1.42-1.48um.

c.  With the above results, I used image reversal again by the same spin coating speed of 3500rpm, exposed at a lower dose of 54mJ/cm2, develop at 20s using pure AZ developer.  The small images were less over-exposed even though there was still some over-exposure.  However, I realized that 20s with pure AZ developer may be too long because the resist thinned down to 0.9-1.32um.  

Also in all the image-reversal processes I have tried, I have noticed a lot of pin-holes in the image-reversed resist.  Does anyone know why this is so and how do I solve this?  

I should add that I had flood exposed the AZ5214E at 200mJ/cm2 after the reversal bake of 120'C for 2mins.

Mr. Jeffrey Mun Pun YUE
余文彬
Division of Bioengineering
E3A-07-02, Nanobioanalytics Lab
7 Engineering Drive 1
National University of Singapore
Singapore 117574
Tel: (65) 65166482, Fax: (65) 68723069
E-mail:  g0500396 at nus.edu.sg