Heteroepitaxy Ge/Si and Dopant Incorporation by Chemical Vapor Deposition
Date Issued
2014
Date
2014
Author(s)
Tu, Wen-Hsien
Abstract
To scale down the CMOS devices in the future, Ge not only the compatible with current Si industry, but also the higher carrier mobility than Si channel. For hole mobility, Ge has the highest hole mobility even compared with group III-V materials. Using the SiGe stressor at source and drain, which is called strain technology, the Ge channel can have both higher electron and hole mobility. Base on its wide use of future CMOS device in the future industry, it is needed to grow high quality SiGe or even Ge material using chemical vapor deposition (CVD) system.
In the first part of this thesis, the SiGe nanoring formation mechanism by Ge out-diffusion from the capped SiGe dot in the ultra-high vacuum CVD (UHV/CVD) is discussed. It is found that the formation of SiGe nanoring can be affected in different carrier gas environment. Less H passivation on the SiGe dot can result more Si cover on the top of dot and retard the Ge out-diffusion to form the nanoring. To grow the nanoring structures on the Ge substrate, the growth mechanism of the Si on Ge growth is studied. The transition from 3-dimensional (3D) to 2-dimensional (2D) growth for Si on Ge, which is different from the Ge on Si case, was observed for the first time. The Si quantum dots can be observed in the initial Si growth on Ge. With the increasing Si deposition, the surface can be flatten without any nanostructures above. At the wetting layer of SiGe dot, more Ge coverage on the surface leads to higher growth rate than the peak of the dot. This different Si growth rate at the SiGe dots region leads to the growth transition from 3D to 2D of Si growth on Ge.
Base on the study on carrier gas and Ge content can affect the SiGe growth mechanism, the second part of this thesis will study the growth rate the photoluminescence characteristics of SiGe and Ge film using silane (SiH4), dichlorosilane (SiCl2H2) and germane (GeH4) in the rapid thermal CVD (RTCVD). It is found that: 1. the SiGe growth rate can be enhanced by Ge content. 2. the SiGe and Ge growth rate using SiH4 and GeH4 can be enhanced in N2 environment. however, the the SiGe growth rate using SiCl2H2and GeH4 can be reduced. Harder desorption of gas phase SiCl2 to retard the coming Si or Ge adsorption can be the reason for reduced growth rate.
For the application of source/drain stressor or the channel of junction less device, the doping technology of Ge is studied in the third part in this thesis. The first technology is the solid phase doping for shallow junction. The solid layers, which have high boron or phosphorous dopants, can diffusion to Ge for shallow junctions. Due to the ion implantation damage free, the diodes doped by solid phase doping have low leakage. However, the dopant solid solubility in Ge is low and diffusion is high during the following activation. So the in situ doping by CVD with different post activation is used to grow high doped Ge. The 3x1020 cm-3 p-type Ge can be reach directly by in situ doping and in situ H2 anneal. Due to the fast phosphorous diffusion, the rapid thermal anneal (RTA) and laser anneal are used to activate n-type dopant. The 2x1020 cm-3 n-type Ge can be reach directly by in situ doping and laser anneal.
Subjects
化學氣象沉積
奈米環狀結構
應變
三維生長回歸到二維生長
載氣效應
矽鍺成長速率
固態參雜
直接參雜
雷射活化
Type
thesis
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