JP2007165471A - Method for etching gallium nitride semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for etching a gallium nitride semiconductor capable of inhibiting the generation of nitrogen holes while being capable of increasing an etching rate. <P>SOLUTION: A mask 23 has a pattern 23a in the etching of gallium nitride. A substrate product 24 is arranged to etching equipment 25. Gallium nitride 15 is etched by using the plasma 27 of a gas G<SB>E</SB>containing Cl<SB>2</SB>, BCl<SB>3</SB>and N<SB>2</SB>. As one example of etching conditions, parallel-plate plasma etching equipment is used as the etching equipment. The flow rate of the gas G<SB>E</SB>containing Cl<SB>2</SB>, BCl<SB>3</SB>and N<SB>2</SB>is set at a value from 30 to 60 sccm. A supply power is set at the value from 0.0002 to 0.01 W/mm<SP>2</SP>. A pressure is set at the value from 1 to 5 Pa. A nitrogen flow ratio (N<SB>2</SB>/(Cl<SB>2</SB>+BCl<SB>3</SB>+N<SB>2</SB>)) is set at the value from 0.1 to 0.2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for etching a gallium nitride based semiconductor.

In Non-Patent Document 1, GaN is etched using inductively coupled Cl ₂ / BCl ₃ plasma. The GaN samples were etched using various Cl ₂ / BCl ₃ ratios and total pressures while maintaining an inductive power of 600 W, a bias of −120 volts, and a substrate temperature of 70 degrees Celsius. Referring to FIG. 1 of Non-Patent Document 1, in BCl ₃ plasma, the etch rate decreases with increasing pressure. In Cl ₂ plasma, the etch rate is maximized at a pressure of about 25 mTorr. For Cl ₂ /10% BCl ₃ plasma and Cl ₂ /50% BCl ₃ plasma, the etch rate is maximized at a pressure of about 30 mTorr. The etch rate when using Cl ₂ /10% BCl ₃ plasma is greater than the etch rate when using Cl ₂ /50% BCl ₃ plasma.

In Non-Patent Document 2, a GaN-based semiconductor is etched using inductively coupled Cl ₂ / N ₂ plasma. Referring to FIG. 4 of Non-Patent Document 2, the etch rate of p-GaN, n-GaN, InGaN, and AlGaN decreases as the nitrogen ratio increases in the Cl ₂ / N ₂ mixed gas.
J. Vac. Sci. Technol. A17 (4), Jul / Aug 1999 pp. 2214-2219 Journal of Korean Physical Society, Vol. 41, No. 2, August 2002, pp.L184-L187

  In gallium nitride semiconductors, the problem of nitrogen vacancies appears in various situations. In dry etching of a gallium nitride based semiconductor, nitrogen vacancies are generated by etching. When nitrogen vacancies are formed on the surface of a gallium nitride based semiconductor, the quality of crystals grown thereafter is affected. It also affects the characteristics of the semiconductor device such as an increase in leakage current.

  Apart from this, as described in Non-Patent Document 2, gallium nitride based semiconductors are chemically more stable than other III-V compound semiconductors. For this reason, it is desired to increase the etching rate of the gallium nitride semiconductor in dry etching.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of etching a gallium nitride based semiconductor that can suppress generation of nitrogen vacancies and increase an etching rate.

One aspect of the present invention is a method for etching a gallium nitride based semiconductor. The method includes a step of etching the gallium nitride based semiconductor using a plasma of a gas containing Cl ₂ , BCl ₃ and N ₂ to form an etched gallium nitride based semiconductor.

According to this method, since the gallium nitride based semiconductor is etched using the plasma of the gas containing N ₂ , generation of nitrogen vacancies is suppressed during the etching. In addition, in the etching using the plasma of the gas containing Cl ₂ , BCl ₃ and N ₂ , unlike the etching using the plasma of the gas containing Cl ₂ and N ₂ , the gallium nitride based semiconductor is accompanied by an increase in the N ₂ ratio. The etching rate does not decrease monotonously.

  In the method of etching a gallium nitride semiconductor according to the present invention, the gallium nitride semiconductor is n-type gallium nitride, p-type gallium nitride, or undoped gallium nitride.

  According to this method, materials such as n-type gallium nitride, p-type gallium nitride, or undoped gallium nitride are often used in gallium nitride-based electronic devices, so that the electrical characteristics of the electronic device can be improved.

  In the method of etching a gallium nitride semiconductor according to the present invention, the etching is performed using a parallel plate etching apparatus. According to this method, the parallel plate etching apparatus can be applied without using the ECR plasma apparatus and the ICP plasma apparatus.

  In the method for etching a gallium nitride semiconductor according to the present invention, the etching is performed using an inductively coupled plasma etching apparatus.

  The method for etching a gallium nitride based semiconductor according to the present invention further comprises a step of forming a resist mask on the gallium nitride based semiconductor prior to etching the gallium nitride based semiconductor, wherein the etched gallium nitride comprises: The pattern of the resist mask is transferred.

  According to this method, the selectivity with respect to the resist can be improved.

In the method for etching a gallium nitride semiconductor according to the present invention, the ratio _X N2 _/ flow rate _X BCl3, _{N 2} flow rate _{X N2} flow _X Cl2, BCl ₃ of Cl ₂ in the etching _{(X Cl2 + X BCl3 + X} N2) Is preferably 0.1 or more.

Ratio _X N2 _/ flow rate _X BCl3, _{N 2} flow rate _{X N2} flow _X Cl2, BCl ₃ of Cl ₂ in the etching _{(X Cl2 + X BCl3 + X} N2) is preferably 0.2 or less.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there is provided a method for etching a gallium nitride based semiconductor that can suppress the generation of nitrogen vacancies and increase the etching rate.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, an embodiment of the method for etching a gallium nitride based semiconductor according to the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

A method for manufacturing a semiconductor device by etching a gallium nitride-based semiconductor will be described with reference to FIGS. 1A, 1B, 2A, and 2B. In this embodiment mode, gallium nitride is used as the gallium nitride semiconductor. FIG. 1A is a drawing showing a step of forming a gallium nitride region. In order to deposit gallium nitride, the substrate 11 is placed on the susceptor of the crystal growth apparatus 13. As the substrate 11, for example, a sapphire substrate, a gallium nitride substrate, a SiC substrate, a Si substrate, or the like can be used. As the crystal growth apparatus 13, for example, an organic metal vapor phase epitaxy (OMVPE) furnace can be used. Raw material metal-organic vapor phase epitaxy reactor G _{M (e.g.,} trimethyl gallium, ammonia, and hydrogen) to supply, to produce an epitaxial substrate 16 by growing a gallium nitride layer 15.

  Next, a mask is formed on the gallium nitride film 15. FIG. 1B is a diagram illustrating a process of manufacturing a mask. In this embodiment, a resist mask is formed, but the mask material is not limited to the resist. After applying a resist on the gallium nitride film 15, the resist 19 is exposed 21 using an optical mask 17 having a pattern. The exposed resist is developed to form a mask (reference numeral 23 in FIG. 2A). Thereby, the substrate product 24 is provided.

FIG. 2A is a diagram illustrating a process of etching gallium nitride. The mask 23 has a pattern 23a. The substrate product 24 is placed in the etching apparatus 25. The gallium nitride 15 is etched using the plasma 27 of a gas _{G E} containing Cl _2, BCl ₃ and _{N 2.}

An example of etching conditions is shown.
Etching device: parallel plate type plasma etching apparatus _Cl 2, BCl ₃ and _N gas _{G E} containing ₂ flow: 30 or more 60sccm less supply power: 0.0002 or 0.01 W / mm ²
Pressure: 1 or more and 5 Pa or less N ₂ / (Cl ₂ + BCl ₃ + N ₂ ) Nitrogen flow rate ratio: 0.1 or more and 0.2 or less. For example, the gallium nitride based semiconductor can be n-type gallium nitride, p-type gallium nitride, or undoped gallium nitride.

It is preferable flow rate of the G _E is 30sccm more. It is preferable that the flow rate of _GE is 60 sccm or less.
If the power supplied to the etching apparatus is 0.0002 or more and W / mm ^2, there is a technical advantage of suppressing etch pits. If the power supplied to the etching apparatus is 0.01 W / mm ^2, there is a technical advantage of high-speed etching. The pressure in the chamber is preferably 1 Pascal or higher. If the pressure in the chamber is 5 Pascals or less, there is a technical advantage that a substantially vertical shape can be obtained.
If Cl flow rate _X BCl3 _two flow _X Cl2, BCl _3, the ratio of _{N 2} flow rate _{X N2 X N2 / (X Cl2} + X BCl3 + X N2) is 0.1 or more during etching of improvement in etch rate There are technical advantages.
If Cl flow rate _X BCl3 _two flow _X Cl2, BCl _3, the ratio of _{N 2} flow rate _{X N2 X N2 / (X Cl2} + X BCl3 + X N2) is 0.2 or less during etching, improved etch rates and There is a technical advantage of improving the selectivity of the resist.

According to this method, since the gallium nitride 15 is etched using the plasma 27 of the gas G _E (including N ₂ ), generation of nitrogen vacancies is suppressed during the etching. Further, in the etching using the plasma 27 of the gas G _E (including Cl ₂ , BCl ₃ and N ₂ ), unlike the etching using the plasma of the gas including Cl ₂ and N ₂ , the N ₂ ratio increases. Thus, the etching rate of gallium nitride does not decrease monotonously.

  FIG. 2B shows a substrate product having an etched gallium nitride film. The substrate product 29 includes a substrate 11 and an etched gallium nitride film 31. In the gallium nitride film 31, a shape corresponding to the pattern 23a of the mask 23 is formed as a result of etching. Many of the nitrogen vacancies in the etched surface 13b of the gallium nitride film 31 are complemented.

FIG. 3 is a drawing schematically showing an etching apparatus used in a method for etching gallium nitride. The etching apparatus 25 includes a process chamber 41. A vacuum exhaust device 43 is connected to the process chamber 41, and the reaction product, raw material gas, residual gas and the like are exhausted to maintain the degree of vacuum in the process chamber 41. In the process chamber 41, a first electrode 45 and a second electrode 47 are provided. The first electrode 45 and the second electrode 47 face each other, and when high frequency power is applied between the first electrode 45 and the second electrode 47, plasma is generated. The first electrode 45 supports the wafer W. The first electrode 45, and the high-frequency electrode 49 is connected, is used to the process chamber 41 to generate plasma of the etching gas G _E. The first electrode 45 is made of, for example, an aluminum material. The second electrode 47 is made of, for example, an aluminum material. The second electrode 47 has a shower head structure, for supplying an etching gas G _E as uniform plasma is generated on wafer W which is held on the first electrode 45 into the process chamber . A gas supply system 51 is connected to the second electrode 47 via a piping system 53 and a valve system 55. The gas supply system 51 includes a nitrogen gas source 51a, a boron trichloride gas source 51b, and a chlorine gas source 51c. As the gas supply system 51, three gas sources 51a to 51c are shown as typical gas sources. The gas flow rate from each of the gas sources 51a to 51c is adjusted by valves 55a to 55c.

Example 1
Subsequently, an example for the present embodiment will be described. FIG. 4 is a diagram showing a result of an experiment performed using the etching apparatus shown in FIG. The gallium nitride film is deposited on the sapphire substrate. The gallium nitride film is an undoped film. Referring to FIG. 4, experimental values D1 to D4 are shown.
Experimental value D1:
Cl _2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 50 sccm
Supply power: 0.004 W / mm ²
Pressure: 3 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.0
Experimental value D2:
Cl _2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 50 sccm
Supply power: 0.004 W / mm ²
Pressure: 3 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.09
Experimental value D3:
Cl _2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 50 sccm
Supply power: 0.004 W / mm ²
Pressure: 3-pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.17
Experimental value D4:
Cl _2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 50 sccm
Supply power: 0.004 W / mm ²
Pressure: 3 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.29
It is.

Since the gallium nitride 15 is etched using the plasma 27 of a gas containing N ₂ , generation of nitrogen vacancies is suppressed during the etching. Further, in the etching using the plasma 27 of the gas containing Cl ₂ , BCl ₃ and N ₂ , unlike the etching using the plasma of the gas containing Cl ₂ and N ₂ , the gallium nitride is increased as the N ₂ ratio increases. The etching rate does not decrease monotonously. As shown in FIG. 4, the etching rate increases when the ratio of nitrogen is about 0.1 to about 0.2.

(Example 2)
Experimental values E1 to E3 in the inductively coupled plasma etching apparatus are shown.
Experimental value E1:
Etch rate: of 100 nm / min _Cl 2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 40 sccm
Supply power: 0.009 W / mm ²
Bias power: 0.003 W / mm ²
Pressure: 0.5 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.0
Experimental value E2:
Etch rate: 125 nm / minute _Cl 2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 40 sccm
Supply power: 0.009 W / mm ²
Bias power: 0.003 W / mm ²
Pressure: 0.5 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.14
Experimental value E3:
Etch rate: of 100 nm / min _Cl 2, BCl ₃ and _N gas _{G E} containing ₂ flow rate: 40 sccm
Supply power: 0.009 W / mm ²
Bias power: 0.003 W / mm ²
Pressure: 0.5 Pascal nitrogen flow ratio (N ₂ / (Cl ₂ + BCl ₃ + N ₂ )): 0.33
It is.

  In the method for etching gallium nitride according to the present embodiment, a resist mask 23 is formed on gallium nitride 15 prior to etching gallium nitride 15. Thus, the resist mask pattern is transferred to the etched gallium nitride. This method has a good selectivity with respect to the resist.

According to the present embodiment, the effect of surface modification of gallium nitride can be obtained by adding nitrogen as compared with etching using a mixed gas of Cl ₂ / BCl ₃ described in Non-Patent Document 1. An increase in nitrogen vacancies in the etched gallium nitride surface layer is suppressed. Further, the selectivity with respect to the resist is improved. Furthermore, side etching is reduced.

Further, according to the present embodiment, the selectivity with respect to the resist can be improved as compared with the etching using the mixed gas of Cl ₂ / N ₂ described in Non-Patent Document 2. Also, side etching is reduced. Furthermore, the etching rate is improved.

As shown in the experimental results of Non-Patent Document 2, when a mixed gas of Cl ₂ / N ₂ is used, the etching rate decreases as the amount of nitrogen added increases. However, when a mixed gas of Cl ₂ , BCl ₃ and N ₂ is supplied to the chamber, the etching rate of gallium nitride does not decrease monotonically as the amount of nitrogen added increases, but increases as the amount of nitrogen added increases. Shows the maximum value. After this maximum, the gallium nitride etch rate decreases as the amount of nitrogen added increases.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. In this embodiment, gallium nitride is described as an example, but InGaN, AlGaN, and InAlGaN can also be etched. These materials, like gallium nitride, exhibit reduced generation of nitrogen vacancies and chemically stable properties. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1A is a drawing showing a step of forming a gallium nitride region. FIG. 1B is a diagram illustrating a process of manufacturing a mask. FIG. 2A is a diagram illustrating a process of etching gallium nitride. FIG. 2B shows a substrate product having an etched gallium nitride film. FIG. 3 is a drawing schematically showing an etching apparatus used in the present embodiment. FIG. 4 is a diagram showing a result of an experiment performed using the etching apparatus shown in FIG.

Explanation of symbols

G M _... raw material, 11 ... substrate, 13 ... crystal growth apparatus, 15 ... gallium nitride film, 16 ... epitaxial substrate, 17 ... optical mask, 19 ... resist, 21 ... exposure, 23 ... mask, 24 ... substrate product, 25 DESCRIPTION OF SYMBOLS Etching device, 27 ... Plasma, 29 ... Substrate product, 31 ... Etched gallium nitride film, 31b ... Surface to be etched of gallium nitride film, 41 ... Process chamber, 43 ... Vacuum exhaust device, 45 ... First electrode 47 ... second electrode, W ... wafer, 49 ... high frequency electrode, 51 ... gas supply system, 53 ... piping system, 55 ... valve system, 51a ... nitrogen gas source, 51b ... boron trichloride gas source, 51c ... chlorine Gas source, 53a ... nitrogen piping, 53b ... boron trichloride piping, 53c ... chlorine piping, 55a-55c ... valve

Claims (6)

A method of etching a gallium nitride based semiconductor,
A method comprising etching a gallium nitride based semiconductor using a plasma of a gas containing Cl ₂ , BCl ₃ and N ₂ to form an etched gallium nitride based semiconductor.   The method according to claim 1, wherein the gallium nitride based semiconductor is n-type gallium nitride, p-type gallium nitride, or undoped gallium nitride.   The method according to claim 1, wherein the etching is performed using a parallel plate etching apparatus or an inductively coupled plasma etching apparatus. Prior to etching the gallium nitride based semiconductor, further comprising forming a resist mask on the gallium nitride based semiconductor;
The method according to claim 1, wherein the resist mask pattern is transferred to the etched gallium nitride. Ratio _X N2 _/ flow rate of Cl _{2 X} Cl2, BCl ₃ flow _X BCl3, _{N 2} flow rate _{X N2 (X Cl2 + X BCl3} + X N2) during etching is 0.1 or more, wherein, wherein The method as described in any one of Claims 1-4. Ratio _X N2 _/ flow rate of Cl _{2 X} Cl2, BCl ₃ flow _X BCl3, _{N 2} flow rate _{X N2 (X Cl2 + X BCl3} + X N2) during etching is 0.2 or less, wherein, wherein The method as described in any one of Claims 1-5.

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