Nano-Structures Stiction Suppression by Molecular Structure Optimized Surface Energy Reduction Agent

Abstract

Scaling of semiconductor devices has caused nano-structure stiction issues during the drying step of wafer cleaning. We have already proposed a surface modification process to reduce the surface energy, and we have demonstrated this process is more effective for preventing nano-structure stiction than conventional IPA (isopropyl alcohol) drying. In this paper, the proper molecular structure is investigated for surface modification agents. It is important for the suppression of stiction to reduce a surface free energy rather than to increase a water contact angle. We have attained stiction free drying of a high aspect ratio pattern with 15 nm half pitch line and space using agents with shorter alkyl groups.

State of the Art and Future Perspectives in Advanced CMOS Technology

“…In the field of microfabrication, the hydroxyl groups are considered highly reactive and are often seen from the silicon oxide surfaces after SC1 or ozonated water treatment. Therefore, replacing the hydroxyl groups with inactive molecules like silylation agents is a good solution to minimize the stiction [ 243 ]. In ref.243, two kinds of straight-chain alkyl group were compared by means of drying HAR structure evaluation.…”

“…Attenuated total reflection–infrared spectroscopy (ATR-FTIR) measurements results showed that C1 treatment sufficiently eliminates the hydroxyl groups, as shown in Figure 39 . On the other hand, it is expected that the C8 reaction was suppressed by its steric hindrance, therefore the existing hydroxyl groups could not be sufficiently substituted with alkyl groups [ 243 ]. The drying observation of the HAR structures with aspect ratio of 13.3 using the C1 and C8 confirmed that it is not important to obtain high water repellency, but it is very important to obtain lower surface free energy, as shown in Figure 40 [ 243 ].…”

“… ATR-IR spectrum measured from silicon oxide powder treated with C1 or C8 shows that C1 has better result because of higher hydrocarbon groups around 750 to 900 cm −1 , while lower hydroxyl group at 960 cm −1 [ 243 ]. …”

“…In ref. 243, two kinds of straight-chain alkyl group were compared by means of drying HAR structure evaluation. The carbon number of the straight-chain alkyl group in the agents is 1 and 8, so they are named C1 and C8, respectively [243].…”

“…243, two kinds of straight-chain alkyl group were compared by means of drying HAR structure evaluation. The carbon number of the straight-chain alkyl group in the agents is 1 and 8, so they are named C1 and C8, respectively [243]. The contact angle of C1(85 • ) is lower than that of C8 (101 • ) as shown in Figure 38, which means longer straight-chain alkyl groups enable a more highly hydrophobic surface [243].…”