| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Monday Sessions |
| Session EM+NS+PS-MoA |
| Session: | More Moore! II |
| Presenter: | Steven Wolf, University of California at San Diego |
| Authors: | S. Wolf, University of California at San Diego M. Edmonds, University of California at San Diego T. Kent, University of California at San Diego D. Alvarez, RASIRC R. Droopad, Texas State University A.C. Kummel, University of California at San Diego |
| Correspondent: | Click to Email |
A silicon nitride passivation layer on semiconductor surfaces can serve several practical uses, such as acting as a diffusion barrier or channel passivation layer prior to dielectric deposition in FinFets or MOSFETs. When employed as a channel passivation layer, further reaction with an oxidant, such as anhydrous peroxide, can leave Si-N-OH termination, which is reactive with all metal ALD precursors thereby providing high nucleation density. Previous studies show stoichiometric ALD Si3N4 growth on Si(100) by hydrazine and Si2Cl6 at temperatures in excess of 350°C with solid ammonium chloride by-product formation1. The first half reaction of N2H4 leaves N-Hx surface termination, and the second reaction with Si2Cl6 adds silicon to the surface and creates a gaseous HCl by-product. An ammonium chloride by-product is usually caused by wall reactions of unreacted precursors. This study focuses on developing a low temperature silicon nitride ALD process with no unwanted solid by-product formation. STM/STS and XPS are employed to characterize SiNx film growth on Si0.5Ge0.5(110).
A test chamber consisting of a reactor chamber, dosing lines, and a dry pump was created and heated to 125°C for 12 hours to allow for sufficient heating of all stainless steel components. In excess of 100 ALD cycles were ran in the test chamber with no visible evidence of powder formation on any walls, and it was concluded that this lengthy heating process prior to SiNx ALD is necessary to eliminate the unwanted powder by-product formation. Next, at a substrate temperature of 275°C and wall temperature of 20°C, the silicon nitride ALD procedure was performed on a p-type Si0.5Ge0.5(110) surface that underwent an ex-situ wet organic clean followed by a dip into a 2% HF/water solution with a toluene layer on top. The sample was pulled through toluene and loaded into UHV as quickly as possible to minimize native oxide formation. After a 315 MegaLangmuir anhydrous hydrazine dose, XPS shows N-Hx surface termination, and removal of half of the initial carbon contamination. A subsequent 21 MegaLangmuir Si2Cl6 dose followed by 17 cycles of 3 MegaLangmuir hydrazine and 3 MegaLangmuir Si2Cl6 leads to increased silicon nitride growth as shown by a large increase in XPS Si 2p and N 1s peaks, as well as a decrease in the Ge 3d substrate peak. After the ALD cycling with room temperature walls, a white powder, presumed to be ammonium chloride, was seen in the reactor, but will now be avoided using the 125°C wall temperature.
1. S. Morishita et. al., Appl. Surf. Sci., 112, p:198-204 (1997).