# US 5,344,793 A · Formation of silicided junctions in deep sub-micron MOSFETs by defect enhanced CoSi2 formation

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- Number: US 5,344,793 A
- Document ID: US5344793A
- Status: Granted
- Kind: A
- Application number: 08/026,944
- Filed: 1993-03-05
- Granted: 1994-09-06
- Earliest claimed: 1993-03-05
- Assignees: Siemens Aktiengesellschaft
- Inventors: Heinrich Zeininger; Christoph Zeller; Udo Schwalke; Uwe Doebler; Wilfried Haensch
- Web page: https://patentgrep.com/patent/US5344793A

## CPC

- H10D 62/83: being Group IV materials, e.g. B-doped Si or undoped Ge
- H10D 64/0112: {using conductive layers comprising silicides}
- H10D 64/62: Electrodes ohmically coupled to a semiconductor
- Y10S 148/017: Clean surfaces
- Y10S 148/019: Contacts of silicides
- Y10S 438/974: Substrate surface preparation
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An method of providing defect enhanced CoSi2 formation and improved silicided junctions in deep submicron MOSFETs. A silicon wafer having a diffusion window is first precleaned with hydrofluoric acid. After the HF precleaning, the silicon wafer is transferred to a conventional cobalt sputtering tool where it is sputter cleaned by bombardment with low energy Ar+ ions so as to form an ultra-shallow damage region. After the sputter cleaning, and without removing the wafer from the sputtering tool, Cobalt metal is deposited on the silicon wafer at room temperature and a CoSi2 layer is formed in the diffusion window.

## Claims

### Claim 1

A method of forming silicided junctions in a deep submicron MOSFET, comprising the steps of:
precleaning, in an acid dip, a silicon wafer having an oxide layer disposed thereon and diffusion window open in the oxide layer so as to expose bulk silicon;
after the precleaning, transferring the silicon wafer to a sputtering tool;
in the sputtering tool, sputter cleaning by bombarding the silicon wafer with low energy Ar+ ions, wherein the bombardment with low energy Ar+ ions occurs at about 1.5 KeV at 1 micro-amp, so as to form a damage region in the bulk silicon exposed by the diffusion window, the damage region being of a depth in the range of three to twenty monolayers of the bulk silicon;
after the bombarding, without removing the silicon wafer from the sputtering tool, depositing cobalt metal at room temperature on the silicon wafer so as to form a cobalt silicide layer; and
wherein the cobalt silicide layer is formed during deposition of the cobalt metal without any further annealing step.

### Claim 2 (depends on 1)

The method of claim 1 wherein the cobalt silicide layer formed during deposition of the cobalt metal is less than 30 nanometers in depth.

### Claim 3

A method of forming silicided junctions in a deep sub-micron MOSFET, comprising the steps of:
precleaning a silicon wafer, having a diffusion window formed therein, with an acid;
after the precleaning, transferring the silicon wafer to a cobalt sputtering tool;
in the cobalt sputtering tool, sputter cleaning by bombarding the silicon wafer with low energy ions so as to damage at least several monolayers of silicon exposed by the diffusion window; and,
after the bombarding, depositing cobalt metal on the silicon wafer, at room temperature, so as to form a cobalt silicide layer with no further annealing step.

### Claim 4 (depends on 3)

The method of claim 3 wherein bombarding damages only from three to seven monolayers of the silicon exposed by the diffusion window.

### Claim 5 (depends on 3)

The method of claim 3 wherein the bombarding with low energy ions is performed using Ar+ ions at about 1.5 KeV at 1 uA.

### Claim 6 (depends on 5)

The method of claim 5 wherein the bombarding with low energy occurs for 10 minutes or less and is performed using Ar+ ions.

### Claim 7 (depends on 3)

The method of claim 3 wherein the bombarding with low energy ions is performed using Ar+ ions at about 1.5 keV at about 1 micro-amp for 10 to 15 minutes.

### Claim 8 (depends on 3)

The method of claim 3 wherein the cobalt silicide layer formed during deposition of the cobalt metal is less than 30 nanometers in depth.