# US 6,720,273 B1 · Device and method for the high-frequency etching of a substrate using a plasma etching installation and device and method for igniting a plasma and for pulsing the plasma out put or adjusting the same upwards

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- Number: US 6,720,273 B1
- Document ID: US6720273B1
- Status: Granted
- Kind: B1
- Application number: 09/763,138
- Filed: 2001-04-20
- Granted: 2004-04-13
- Earliest claimed: 1999-06-18
- Assignees: Robert Bosch GmbH
- Inventors: Volker Becker; Franz Laermer; Andrea Schilp; Thomas Beck
- Web page: https://patentgrep.com/patent/US6720273B1

## CPC

- H01J 37/32174: {Circuits specially adapted for controlling the RF discharge}
- C30B 33/12: in gas atmosphere or plasma
- H01J 37/32082: {Radio frequency generated discharge (H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence)}
- H10P 50/242: {of Group IV materials}
- H10P 50/244: {comprising alternated and repeated etching and passivation steps}
- H10P 50/694: {characterised by their behaviour during the process, e.g. soluble masks or redeposited masks}
- H10P 50/695: {characterised by the process involved to create the mask, e.g. lift-off masks or sidewalls or to modify the mask}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A device and a method capable of being carried out therewith for, preferably, anisotropically etching a substrate (10), in particular, a patterned silicon body, with the assistance of a plasma (14), is proposed. In the process, the plasma (14) is produced by a plasma source (13) to which a high-frequency generator (17) is connected for applying a high-frequency power. Moreover, this high-frequency generator is in communication with a first means which periodically changes the high-frequency power applied to the plasma source (13). Besides, provision is preferably made for a second means which adapts the output impedance of the high-frequency generator (17) to the prevailing impedance of the plasma source (13) which changes as a function of the high-frequency power. The proposed anisotropic etching method is carried out in separate and alternating etching and polymerization steps, a higher high-frequency power of up to 5000 watts being, at least temporarily, applied to the plasma source (13) during the etching steps than during the deposition steps. The proposed device is also suitable for igniting a plasma (14) and for adjusting upward or pulsing a plasma power from a starting value to up to 5000 watts.

## Claims

### Claim 1

A device for etching a patterned silicon body substrate with a plasma, comprising:
a high-frequency generator;
a plasma source for generating a high-frequency electromagnetic alternating field, a high frequency power to be applied to the plasma source with assistance of the high-frequency generator;
a reactor for generating the plasma from reactive particles through an action of the high-frequency electromagnetic alternating field upon one of a reactive gas and a reactive gas mixture; and
a first arrangement for producing a periodical change in the high-frequency power applied to the plasma source;
wherein the first arrangement includes one of:
a component for controlling a power of the high-frequency generator, a digital ramp generator being programed via a software in the component, and
a component for controlling the power of the high-frequency generator including an analog ramp generator.

### Claim 2 (depends on 1)

The device according to claim 1, wherein the analog ramp generator has an RC circuit which is provided with at least one diode.

### Claim 3 (depends on 1)

The device according to claim 1, further comprising a second arrangement which, during the periodical change in the high-frequency power applied to the plasma source, at least temporarily adapts an output impedance of the high-frequency generator to a prevailing impedance of the plasma source which changes as a function of the high-frequency power.

### Claim 4 (depends on 3)

The device according to claim 3, wherein:
the adaptation of the output impedance is carried out one of continuously and stepwise and is automated; and
the applied high-frequency power lies between 400 W and 5000 W.

### Claim 5 (depends on 3)

The device according to claim 3, wherein the second arrangement is an impedance transformer.

### Claim 6

A method for anisotropically etching a substrate using a device for etching the substrate with a plasma, comprising the steps of:
causing a plasma source to generate a high-frequency electromagnetic alternating field, a high-frequency generator being adapted to apply a high-frequency power to the plasma source;
causing a reactor to generate the plasma from reactive particles through an action of the high-frequency electromagnetic alternating field upon one of a reactive gas and a reactive gas mixture;
causing a first arrangement to produce a periodical change in the high-frequency power applied to the plasma source by one of:
operating a component for controlling a power of the high-frequency generator via a software-programmed digital ramp generator, and
operating a component including an analog ramp generator and for controlling the power of the high-frequency generator,
carrying out the anisotropic etching process in separate etching and polymerization steps alternatingly following each other; and
applying a polymer to lateral patterns defined by an etching mask during the polymerization steps, the polymer being removed again in each case during the subsequent etching steps;
wherein, during the etching steps, at least temporarily, and in each case higher high-frequency power is applied to the plasma source than during the deposition steps.

### Claim 7 (depends on 6)

The method according to claim 6, wherein during the etching steps, at least temporarily, a high-frequency power of 800 watts to 5000 watts is applied to the plasma source, and during the deposition steps, at least temporarily, a high-frequency power of 400 watts to 1500 watts is applied to the plasma source.

### Claim 8 (depends on 6)

The method according to claim 6, wherein at least one of:
an increase in the high-frequency power during a change from the deposition steps to the etching steps is carried out one of stepwise and continuously; and
a decrease in the high-frequency power during the change from the etching steps to the deposition steps is carried out one of stepwise and continuously.

### Claim 9 (depends on 8)

The method according to claim 8, wherein at least the increase in the high-frequency power is carried out in such a manner that during this time, at least temporarily, an impedance of the high-frequency generator is adapted to a plasma impedance at least approximately in (a) one of a continuous and stepwise, and (b) an automated manner via a second arrangement.

### Claim 10 (depends on 8)

The method according to claim 8, wherein at least one of:
a duration of the increase in the high-frequency power during the change from the deposition steps to the etching steps is 0.2 sec to 5 sec; and
a duration of the decrease increase in the high-frequency power during the change from the etching steps to the deposition steps is 0 sec to 2 sec.

### Claim 11 (depends on 7)

The method according to claim 7, wherein during the etching steps the high-frequency power is between 2000 watts and 4000 watts.

### Claim 12 (depends on 7)

The method according to claim 7, wherein during the deposition steps the high-frequency power is between 500 watts to 1000 watts.

### Claim 13 (depends on 9)

The method according to claim 9, wherein the second arrangement includes an impedance transformer.

### Claim 14 (depends on 10)

The method according to claim 10, wherein the duration of the increase in the high-frequency power during the change from the deposition steps to the etching steps is 0.5 sec to 3 sec.

### Claim 15 (depends on 10)

The method according to claim 10, wherein the duration of the decrease in the high-frequency power during the change from the etching steps to the deposition steps is 0 sec to 0.5 sec.

### Claim 16

A device for etching a substrate with a plasma, comprising:
a plasma source adapted to generate a high-frequency electromagnetic alternating field;
a high-frequency generator adapted to apply a high-frequency power to the plasma source;
a reactor adapted to generate the plasma from reactive particles by the high-frequency electromagnetic alternating field acting on one of a reactive gas and a reactive gas mixture; and
a first arrangement adapted to produce a periodical change in the high-frequency power applied to the plasma source, the first arrangement being a component for controlling a power of the high-frequency generator, the component including one of a digital ramp generator programmed via a software and an analog ramp generator.