# US 8,772,860 B2 · FINFET transistor structure and method for making the same

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- Number: US 8,772,860 B2
- Document ID: US8772860B2
- Status: Granted
- Kind: B2
- Application number: 13/116,018
- Filed: 2011-05-26
- Published: 2012-11-29
- Granted: 2014-07-08
- Earliest claimed: 2011-05-26
- Assignees: United Microelectronics Corp.
- Applicants: Rai-Min Huang; Sheng-Huei Dai; Chen-Hua Tsai; Duan Quan Liao; Yikun Chen; Xiao Zhong Zhu
- Inventors: Rai-Min Huang; Sheng-Huei Dai; Chen-Hua Tsai; Duan Quan Liao; Yikun Chen; Xiao Zhong Zhu
- Web page: https://patentgrep.com/patent/US8772860B2

## CPC

- H10D 62/116: {adjoining the input or output regions of field-effect devices, e.g. adjoining source or drain regions}
- H10B 12/056: {the transistor being a FinFET}
- H10B 12/36: {the transistor being a FinFET}
- H10D 30/024: {of fin field-effect transistors [FinFET]}
- H10D 30/62: Fin field-effect transistors [FinFET]
- H10D 30/6213: {having rounded corners}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

A FINFET transistor structure includes a substrate, a fin structure, an insulating layer and a gate structure. The fin structure is disposed on the substrate and directly connected to the substrate. Besides, the fin structure includes a fin conductive layer and a bottle neck. The insulating layer covers the substrate and has a protruding side which is formed by partially surrounding the bottle neck of the fin structure, and a bottom side in direct contact with the substrate so that the protruding side extend to and under the fin structure. The gate structure partially surrounds the fin structure.

## Claims

### Claim 1

A method for forming a FINFET transistor structure, comprising:
providing a substrate and a fin structure disposed on said substrate, wherein said fin structure comprises a mask layer, a buffer layer, a cap layer, a fin conductive layer and a spacer surrounding said mask layer, said buffer layer, said cap layer and said fin conductive layer;
performing a substrate etching step comprising a vertical etching step and a lateral etching step to form a first recess and a second recess connecting to said first recess in said substrate, wherein said second recess has a protruding side extending to and under said fin structure;
forming an oxide to fill said first recess and said second recess;
removing said spacer after said oxide filling up said first recess and said second recess; and
forming a gate structure comprising a gate dielectric layer and a gate material layer, said gate structure partially surrounding said fin structure, wherein said gate dielectric layer is disposed outside of said second recess.

### Claim 2 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein said vertical etching step is performed before said lateral etching step.

### Claim 3 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein said vertical etching step is performed after said lateral etching step.

### Claim 4 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein forming said fin structure comprises:
providing said substrate, said cap layer disposed on said substrate, said buffer layer disposed on said cap layer and said mask layer disposed on said buffer layer;
using said mask layer as an etching mask to perform a fin structure etching step to partially remove said buffer layer, said cap layer and said substrate;
forming a spacer material layer to completely cover said mask layer, said buffer layer, said cap layer and said substrate; and
performing a side wall etching step to partially remove said spacer material layer to obtain said side wall.

### Claim 5 (depends on 4)

The method for forming a FINFET transistor structure of claim 4, wherein said spacer material layer comprises a first spacer material layer and a second spacer material layer.

### Claim 6 (depends on 4)

The method for forming a FINFET transistor structure of claim 4, wherein said fin structure etching step comprises a dry etching step.

### Claim 7 (depends on 6)

The method for forming a FINFET transistor structure of claim 6, wherein said fin structure etching step further comprises a wet etching step.

### Claim 8 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein a dry etching is used to perform said vertical etching step.

### Claim 9 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein said lateral etching step comprises a dry etching step.

### Claim 10 (depends on 9)

The method for forming a FINFET transistor structure of claim 9, wherein said lateral etching step further comprises a wet etching step.

### Claim 11 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein a furnace oxidation procedure is used to oxidize said substrate to form said oxide and said oxide becomes a field oxide to segregate said substrate and said fin structure.

### Claim 12 (depends on 11)

The method for forming a FINFET transistor structure of claim 11, further comprising:
removing said spacer by a wet etching after forming said oxide.

### Claim 13 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein said vertical etching step forms a first recess for use as a shallow trench isolation.

### Claim 14 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, wherein said lateral etching step forms a bottle neck in said fin structure.

### Claim 15 (depends on 14)

The method for forming a FINFET transistor structure of claim 14, wherein said bottle neck has a width between 3 μm-10 μm.

### Claim 16 (depends on 14)

The method for forming a FINFET transistor structure of claim 14, wherein a width of said bottle neck is 40%-60% of that of said fin structure.

### Claim 17 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, further comprising:
oxidizing said substrate to form a pad layer disposed on the sidewall of said first recess and said second recess.

### Claim 18 (depends on 17)

The method for forming a FINFET transistor structure of claim 17, further comprising:
covering said fin structure comprising said sidewall by using said oxide; and
partially removing said oxide so that the outer surface of said oxide is in direct contact with the bottom of said spacer.

### Claim 19 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, further comprising:
removing said mask layer and said buffer layer so that said gate dielectric layer is in direct contact with said cap layer.

### Claim 20 (depends on 1)

The method for forming a FINFET transistor structure of claim 1, further comprising:
removing said cap layer.