US EPA

6762477 

Journal Article 

ETCHING RATE AND MECHANISM OF DOPED OXIDE IN BUFFERED HYDROGEN-FLUORIDE SOLUTION 

Kikuyama, H; Waki, M; Kawanabe, I; Miyashita, M; Yabune, T; Miki, N; Takano, J; Ohmi, T; , 

1992 

1 

Journal of Electrochemical Society
ISSN: 0013-4651
EISSN: 1945-7111 

ELECTROCHEMICAL SOC INC 

PENNINGTON 

2239-2243 

WOS:A1992JG90100029 

Etching rates of borosilicate, borophosphosilicate, phosphosilicate, and arsenosilicate glass films in various buffered hydrogen fluoride solution (BHF) have been studied. Etching rates were found to depend on the glass composition and dopant concentration as well as the concentration of ammonium fluoride in the BHF. This phenomenon is clearly different from the etching rate of thermal SiO2 oxide which is hardly affected by the concentration of ammonium fluoride in excess of equimolar to the HF concentration. The etching rates of the doped films may sometimes be higher than that of a nondoped SiO2 film but the rate is reduced when certain other dopants are present. This phenomenon is attributable to valence differences between silicon and the dopant elements. If the doped film is electrophilic compared to silicon, the etching rate is higher; if it is nucleophilic, the etching rate is lower. By controlling the type and concentration of the dopant and the concentration of NH4F in BHF, it is possible to etch the doped film and thermal oxide at either the same rate or selectivity with respect to one another.