# US 8,236,603 B1 · Polycrystalline semiconductor layers and methods for forming the same

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- Number: US 8,236,603 B1
- Document ID: US8236603B1
- Status: Granted
- Kind: B1
- Application number: 12/554,486
- Filed: 2009-09-04
- Granted: 2012-08-07
- Earliest claimed: 2008-09-04
- Assignees: Solexant Corp.; Rochester Institute of Technology
- Inventors: Leslie G. Fritzemeier; Ryne P. Raffaelle; Christopher Leitz
- Web page: https://patentgrep.com/patent/US8236603B1

## CPC

- H10F 71/131: {Recrystallisation; Crystallization of amorphous or microcrystalline semiconductors}
- H10F 77/164: Polycrystalline semiconductors
- Y02E 10/50: Photovoltaic [PV] energy
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- Y10S 438/969: Simultaneous formation of monocrystalline and polycrystalline regions
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A semiconductor structure may include a polycrystalline substrate comprising a metal, the polycrystalline substrate having substantially randomly oriented grains, as well as a buffer layer disposed thereover. The buffer layer may comprise a plurality of islands having an average island spacing therebetween. A polycrystalline semiconductor layer is disposed over the buffer layer.

## Claims

### Claim 1

A method for forming a semiconductor structure, the method comprising:
providing a polycrystalline substrate comprising a metal and having substantially randomly oriented grains;
forming, over the polycrystalline substrate, a buffer layer comprising a plurality of spaced-apart islands;
forming a semiconductor layer over the buffer layer;
forming a mask over the semiconductor layer; and
inducing relative motion, in a travel direction, between the polycrystalline substrate and a high-temperature region,
wherein one grain of the semiconductor layer grows from the mask preferentially in the travel direction, thereby forming a single-crystalline portion of the semiconductor layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein, prior to the formation of the single-crystalline portion, the semiconductor layer has an average grain size approximately equal to an average spacing between the plurality of spaced-apart islands.

### Claim 3 (depends on 1)

The method of claim 1, wherein forming the semiconductor layer comprises depositing an initial semiconductor layer at a deposition temperature and annealing the initial semiconductor layer at an annealing temperature greater than the deposition temperature, thereby forming the semiconductor layer.

### Claim 4 (depends on 3)

The method of claim 3, wherein the annealing temperature is less than a melting point of the initial semiconductor layer.

### Claim 5 (depends on 1)

The method of claim 1, further comprising forming a photovoltaic device over the single-crystalline portion of the semiconductor layer.

### Claim 6 (depends on 5)

The method of claim 5, wherein the photovoltaic device comprises at least one of a p-n junction or a p-i-n junction.

### Claim 7 (depends on 1)

The method of claim 1, wherein forming the semiconductor layer comprises:
depositing an initial semiconductor layer in an amorphous state such that it retains residual stress after deposition; and
crystallizing the initial semiconductor layer into a polycrystalline state, thereby forming the semiconductor layer,
wherein the residual stress in the initial semiconductor layer provides at least a portion of a driving force for crystallizing the initial semiconductor layer.

### Claim 8 (depends on 1)

The method of claim 1, further comprising forming a capping layer over the semiconductor layer, the capping layer comprising at least one of Al, W, alumina, silicon dioxide, or silicon nitride.

### Claim 9 (depends on 1)

The method of claim 1, wherein forming the semiconductor layer comprises nucleating a grain at a location of each of the plurality of spaced-apart islands of the buffer layer.

### Claim 10 (depends on 1)

The method of claim 1, wherein the polycrystalline substrate comprises at least one of steel or a refractory metal.

### Claim 11 (depends on 1)

The method of claim 1, wherein the buffer layer comprises at least one of a metal, a metal alloy, or a dielectric material.

### Claim 12 (depends on 1)

The method of claim 1, wherein the buffer layer comprises at least one of Cu, Al, W, or Re.

### Claim 13 (depends on 1)

The method of claim 1, wherein the semiconductor layer comprises Ge.

### Claim 14 (depends on 1)

The method of claim 1, wherein the single-crystalline portion is greater than 50% of the semiconductor layer.

### Claim 15 (depends on 14)

The method of claim 14, wherein the single-crystalline portion is greater than 90% of the semiconductor layer.

### Claim 16 (depends on 1)

The method of claim 1, wherein forming the semiconductor layer comprises:
depositing an initial semiconductor layer;
forming a capping layer over the initial semiconductor layer; and
crystallizing the initial semiconductor layer, thereby forming the semiconductor layer.

### Claim 17 (depends on 16)

The method of claim 16, further comprising removing the capping layer from the semiconductor layer.

### Claim 18 (depends on 16)

The method of claim 16, wherein the capping layer comprises at least one of Al, W, alumina, silicon dioxide, or silicon nitride.