# US 11,906,946 B2 · System and method for controlling directionality of fast-wet etching of crystalline silicon, c-Si

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- Number: US 11,906,946 B2
- Document ID: US11906946B2
- Status: Granted
- Kind: B2
- Application number: 17/496,111
- Filed: 2021-10-07
- Published: 2022-04-14
- Granted: 2024-02-20
- Earliest claimed: 2020-10-08
- Assignees: National University of Singapore; Agency for Science, Technology and Research
- Applicants: National University of Singapore; Agency for Science, Technology and Research
- Inventors: Utkur Mirsaidov; Michel Bosman; Tanmay Ghosh; Zainul Aabdin; Frank Holsteyns; Antoine Pacco
- Web page: https://patentgrep.com/patent/US11906946B2

## CPC

- G05B 19/4099: Surface or curve machining, making three-dimensional [3D] objects, e.g. desktop manufacturing
- H10P 50/644: {Anisotropic liquid etching (H10P50/61 takes precedence)}
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- G05B 2219/45031: Manufacturing semiconductor wafers
- H10D 62/122: {oriented at angles to substrates, e.g. perpendicular to substrates}
- H10D 62/405: {Orientations of crystalline planes}
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

This document describes a system and method for selectively switching the fast-wet-etching direction of crystalline silicon, c-Si, nanostructures between the (100) and the (110) crystallographic planes of c-Si by a simple method of sample agitation. This method effectively allows the invention to achieve anisotropic and isotropic wet-etching of c-Si.

## Claims

### Claim 1

A method for controlling directionality of fast-wet-etching of crystalline silicon, c-Si, the method comprising:
anisotropically wet-etching the c-Si along a first crystallographic plane of the c-Si using an etching solution that wet-etches the c-Si along the crystallographic plane at a faster rate than the c-Si along a second crystallographic plane of the c-Si, wherein the etching solution comprises potassium hydroxide (KOH) and the etching byproducts from the wet-etched c-Si comprises orthosilicic acid, Si(OH)4, and wherein the KOH solution comprises concentration levels <10% (w/v), and is maintained at a temperature range between 20° C.-30° C.; and
increasing the rate of removal of etching byproducts from the second crystallographic plane of the wet-etched c-Si to cause the wet-etching of the c-Si along the second crystallographic plane to be at a faster rate than the wet-etching of the c-Si along the first crystallographic plane of the c-Si.

### Claim 2 (depends on 1)

The method according to claim 1 wherein the step of increasing the rate of removal of the etching byproducts from the second crystallographic plane of the wet-etched c-Si comprises:
agitating the etching solution such that the etching solution fluid contacts the c-Si along a direction parallel to the second crystallographic plane of the c-Si.

### Claim 3 (depends on 1)

The method according to claim 1 wherein the step of increasing the rate of removal of the etching byproducts from the second crystallographic plane of the wet-etched c-Si comprises:
applying an oscillatory force to the c-Si such that the c-Si oscillates for part of the time along a direction parallel to the second crystallographic plane of the c-Si.

### Claim 4 (depends on 1)

The method according to claim 1 further comprising the step of:
reducing the rate of removal of etching byproducts from the second crystallographic plane of the wet-etched c-Si to cause the wet-etching of the c-Si along the second crystallographic plane to be at a slower rate than the wet-etching of the c-Si along the first crystallographic plane of the c-Si.

### Claim 5

A system for controlling directionality of fast-wet-etching of crystalline silicon, c-Si, the system comprising:
a wet-etching setup configured to:
anisotropically wet-etch the c-Si along a first crystallographic plane of the c-Si using an etching solution that wet-etches the c-Si along the first crystallographic plane at a faster rate than the c-Si along a second crystallographic plane of the c-Si, wherein the etching solution comprises potassium hydroxide (KOH) and the etching byproducts from the wet-etched c-Si comprises orthosilicic acid, Si(OH)4, and wherein the KOH solution comprises concentration levels <10% (w/v), and is maintained at a temperature range between 20° C.-30° C.; and
increase the rate of removal of etching byproducts from the second crystallographic plane of the wet-etched c-Si to cause the wet-etching of the c-Si along the second crystallographic plane to be at a faster rate than the wet-etching of the c-Si along the first crystallographic plane of the c-Si.

### Claim 6 (depends on 5)

The system according to claim 5 wherein the increasing of the rate of removal of the etching byproducts from the second crystallographic plane of the wet-etched c-Si comprises the wet-etching setup being further configured to:
agitate the etching solution such that the etching solution fluid contacts the c-Si along a direction parallel to the second crystallographic plane of the c-Si.

### Claim 7 (depends on 5)

The system according to claim 5 wherein the increasing of the rate of removal of the etching byproducts from the second crystallographic plane of the wet-etched c-Si comprises the wet-etching setup being further configured to:
apply an oscillatory force to the c-Si such that the c-Si oscillates for part of the time along a direction parallel to the second crystallographic plane of the c-Si.

### Claim 8 (depends on 5)

The system according to claim 5 wherein the wet-etching setup is further configured to:
reduce the rate of removal of etching byproducts from the second crystallographic plane of the wet-etched c-Si to cause the wet-etching of the c-Si along the second crystallographic plane to be at a slower rate than the wet-etching of the c-Si along the first crystallographic plane of the c-Si.