The adhesion strength and high temperature/high humidity reliability of Polyetherimide (PEI) adhesive on silicon wafer after being treated by RIE, Al-chelate system adhesion promoter, and perchloric acid was investigated, and the relationship between adhesion strength and high temperature/high humidity reliability was explained by various adhesion mechanism theories. 180°peel test and 「85℃85%」humidity test were performed for the initial adhesion strength and high temperature/high humidity reliability tests. For investigating microscopic surface effect SEM, AFM, DI-Water contact angle, AES and ATR-FT-IR studies were carried out.
To investigate RIE effect, PEI was treated with 170 mtorr 40 sccm O2 and 200 Watt RIE for 1, 2, 3, 5 min, and laminated at 300 ℃ for 1 hr. The initial peel strength increased slightly from 1.6 kg/cm for the first 2 min, but decresed after 3 min. High temperature/high humidity resistivity decreased rapidly by RIE etching. RIE treatment on PEI affected on both of roughness and hydrophilicity to increase.
Al-chelate adhesion promoter was coated by spinning on silicon wafer for 3000 rpm 30 sec and cured at 320 ℃ for 4 min. The initial peel strength showed no effect of adhesion promoter treatment, but high temperature/high humidity resistivity increased remarkably. Al-chelate adhesion promoter did not affect the roughness but increased hydrophilicity.
Perchloric acid etching on PEI resulted in decrement of both initial peel strength and high temperature/high humidity reliability. The roughness was not changed by perchloric acid etching. Hydrophilicity was varied with time and temperature. The carbonyl C=O bonding increased slightly and the imide C-N bonding decreased. There was no clear evidence that perchloric acid treatment increased peel strength as was in the metal/polyimide interface research by other researchers.
As a summary, the increment of surface roughness by RIE also increased slightly initial peel strength but increment of hydrophilicity by RIE decreased rapidly high temperature/high humidity reliability. Al-chelate adhesion promoter decreased hydrophilicity, which caused high temperature/high humidity resistivity strengthening. The perchloric acid treatment showed no clear effects. The mechanisms of initial peel strength increment and of high temperature/high humidity reliability have to be further investigated.
