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Method and System for Replacing Metal Oxide Semiconductor Field Effect Transistor Gate with Silicon without using Dummy Oxide

IP.com Disclosure Number: IPCOM000240752D
Publication Date: 2015-Feb-25
Document File: 4 page(s) / 92K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method and system for replacing Metal Oxide Semiconductor Field Effect Transistor (MOSFET) gate with Silicon (Si) without using dummy oxide.

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Page 01 of 4

Method and System for Replacing Metal Oxide Semiconductor Field Effect Transistor Gate with Silicon without using Dummy Oxide

Presently, replacement of gate MOSFETs with amorphous Si dummy gate and SiO 2

dummy oxide is performed using Si technology. SiO2 or other oxides used as dummy gate oxide are problematic. The problem of dummy gate oxides is mainly because of Dilute Hydrofluoric (DHF) acid. The DHF used over MOSFET gate can undercut below spacer and result in high-K encroachment under spacer, thus increasing the fringing electric field. Also, other techniques such as amorphous Carbon without dielectric field are also proposed. However, the low thermal stability of that material causes problem

when depositing nitirde spacer and during source/drain activation or epitaxy.

Disclosed is a method and system for directly replacing Germanium (Ge) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) gate with an amorphous Silicon (Si) as a dummy gate. Here, the replacement of Ge MOSFET gate flow can be applied to the planar and FinFETs.

The dummy gate used for replacing MOSFET gate can be selectively defined by Reactive-ion Etching (RIE). The RIE defined with high selectivity with respect to Ge and nitride forms a spacer. However, junction can be formed using ion-implant or epitaxy and diffusion or combination. After forming the junction, Inter Layer Dielectric (ILD) and Chemical Mechanical Planarization (CMP) is also deposited on the junction. Then, the dummy Si gate can be selectively removed by using a Tetramethylammonium hydroxide (TMAH) based wet process without any need for dummy oxide.

Fig. 1 illustrates a basic Ge Substrate, where isolation of MOSFET is represented in sky blue colour and the Ge substrate is placed on top of the MOSFET is represented in brown colour.

FIG. 1

The method of replacing Ge MOSFET gate starts by depositing dummy amorphous Si directly on Ge, which is illustrated in Fig. 2.

1


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FIG. 2

As illustrated in fig. 2, the dummy amorphous Si represented in orange is deposited over Ge MOSFET without dummy oxide. Also, a Hard Mask (HM) represe...