Pattern Density Dependency of the Underlying Layer on O₃-Tetraethylorthosilicate (TEOS) Film Formation

Abstract

We investigated whether O3-tetraethylorthosilicate (TEOS) film formation by atmospheric-pressure chemical vapor deposition (AP-CVD) creates pattern density effects on the underlying layer. The film thickness ratio of a pattern region to the flat region was 1.5 on a film formed by plasma enhanced chemical vapor deposition using TEOS (PE-TEOS film), and ethanol treatment significantly increased the ratio by 7.0–8.0 times. Moreover, the deposited film became much thicker on the dense pattern region and much thinner on the flat region after ethanol treatment. We propose that the pattern density effect on the deposited film thickness was generated by two types of film formation through each precursor, a polysiloxane with a low deposition rate (DR) on the flat region covered with ethoxy groups (Si-OR), and a silanol with a high DR on the dense pattern region covered with hydroxyl groups (Si-OH).

Gap Filling Model of O3-Tetraethylorthosilicate Film Formed on an Underlying Layer Pretreated with Organic Solvent

“…In a previous report, we showed that the DR difference between the flat and pattern areas increases when the under layer is pretreated with ethanol. 12 This difference also increased with an increase of the pattern density. We concluded that the increase in DR on the pattern area occurs due to the contribution of silanol.…”

“…This insufficient supply of silanol is in contrast to the flat areas, where silanol is readily supplied by the gas flow. 12 As a result, the Si-OR sites in the trenches are longer exposed to O 3 , transforming the Si-OR sites into Si-OH which then react quickly to the silanol, causing a faster DR. The ratio of silanol for polysiloxane which contributes to the deposition is also estimated from deposition rate as followings: On the chemical SiO2 (in case of the ethanol pretreatment), the ratio of silanol to polysiloxane is 1.0 (DR = 97.0 nm/min) to around 0.3 (29.1 nm/min).…”

“…However we could not clarify the gap-filling model at that time. In addition, previous studies have described the relationship between an underlying surface condition and ethanol adsorption, 10 the relationship between its adsorption and the deposition rate (DR), 11 the pattern density effect of the DR 12 as well as the relationship between the surface free energy (SFE) of the underlying layers and the O3-TEOS film formation. 13 When the thermal SiO2 (underlying layer) was slightly etched by dilute hydrofluoric acid (DHF), more ethanol was adsorbed.…”

“…10 It was concluded that ethoxy groups, which were generated by ethanol treatment following light etching using DHF, do not become adsorption sites on the surface of thermal SiO2 during O3-TEOS film deposition, since the O3-TEOS film was formed at a low DR. 11 It was also found that the O3-TEOS film became much thicker on the dense pattern region and much thinner on the flat region after ethanol treatment. 12 We proposed that the pattern density effect on the deposited film thickness was generated by two types of film formation through each precursor, a polysiloxane with a low deposition rate (DR) on the flat region covered with ethoxy groups (Si-OR), and a silanol with a high DR on the dense pattern region covered with hydroxyl groups (Si-OH). 12 Based above studies, [10][11][12] the relationship between the surface free energy (SFE) of the underlying layers and the O3-TEOS film formation was discussed.…”

“…12 We proposed that the pattern density effect on the deposited film thickness was generated by two types of film formation through each precursor, a polysiloxane with a low deposition rate (DR) on the flat region covered with ethoxy groups (Si-OR), and a silanol with a high DR on the dense pattern region covered with hydroxyl groups (Si-OH). 12 Based above studies, [10][11][12] the relationship between the surface free energy (SFE) of the underlying layers and the O3-TEOS film formation was discussed. 13 The O3-TEOS CVD rate decreased as the polar component of SFE decreased for the surface pretreated with organic solvents.…”