KR20130108572A - Method for etching sapphire substrate - Google Patents

Method for etching sapphire substrate Download PDF

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KR20130108572A
KR20130108572A KR1020137008188A KR20137008188A KR20130108572A KR 20130108572 A KR20130108572 A KR 20130108572A KR 1020137008188 A KR1020137008188 A KR 1020137008188A KR 20137008188 A KR20137008188 A KR 20137008188A KR 20130108572 A KR20130108572 A KR 20130108572A
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sapphire substrate
etching
photoresist
prebaking
temperature
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도모야스 니시미야
히로유키 다카하시
아키나오 오쿠모토
아츠키 마루노
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사무코 가부시키가이샤
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
    • H01L21/0273—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers characterised by the treatment of photoresist layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/3065—Plasma etching; Reactive-ion etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate

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  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
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  • Condensed Matter Physics & Semiconductors (AREA)
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Abstract

In the present invention, a photoresist is formed on a sapphire substrate used in a semiconductor light emitting device, and after irradiation with ultraviolet rays having a wavelength of 400 nm or less, the photoresist is applied in a method of etching the sapphire substrate by dry etching using the photoresist pattern as a mask. And a prebaking step of heating the sapphire substrate at a temperature higher than that of the ultraviolet irradiation before the ultraviolet irradiation, and a postbaking step of heating the sapphire substrate at a temperature higher than the prebaking process after the ultraviolet irradiation; And, after the post-baking process, dry etching using the photoresist pattern as a mask to form a plurality of convex portions having an angle of 90 ° or less on the sapphire substrate on the sidewall of the sapphire substrate. .

Description

Etching method of sapphire substrate {METHOD FOR ETCHING SAPPHIRE SUBSTRATE}

The present invention relates to a method of etching a sapphire substrate used in a semiconductor light emitting element.

A semiconductor light emitting diode (LED) has a structure in which electrodes are formed on a p-type semiconductor layer and an n-type semiconductor layer on a substrate. When light is generated in a light emitting region having an active layer by recombination of holes injected from a p-type semiconductor layer and electrons injected from an n-type semiconductor layer, the light is taken out from the surface on which the electrode is formed or from the substrate surface on which the semiconductor layer is not grown. I am supposed to lose.

In a light emitting diode having such a structure, a number of convex portions (concave portions) are formed on the surface of a substrate, and a method of improving external quantum efficiency by scattering and diffracting light generated in a light emitting region has been proposed. In GaN (gallium nitride) -based LEDs, which are one of semiconductor LEDs, sapphire substrates having excellent characteristics are widely used as substrates for crystal growth of GaN-based semiconductors. Many convex parts are formed.

By the way, in the plasma etching apparatus, it is generally desired to be able to etch the thickness of 1 micrometer in about 10 minutes. In order to obtain such an etching rate, it is necessary to etch at a high output high frequency power, but using a high output high frequency power causes burning or carbonization in the photoresist. Therefore, conventionally, the sapphire substrate is placed on a mounting table incorporating a cooling mechanism, and the sapphire substrate is cooled by bringing the sapphire substrate into close contact with the mounting table by means of a mechanical chuck or an electrostatic chuck such as a clamp. (Patent Document 1).

Japanese Patent Application Laid-Open No. 2007-109770

By the way, when using a mechanical chuck or an electrostatic chuck, it takes time to remove the substrate after installation or processing of the substrate on the mounting table. In addition, even when a mechanical chuck or an electrostatic chuck is provided, when the substrate is insufficiently installed, the adhesion between the substrate and the mounting table may decrease, resulting in burnout or carbonization of the photoresist by dry etching.

In order to further improve the external quantum efficiency, a tapered shape (conical object, conical shape) is formed on the surface of the sapphire layer, and the gap between the adjacent convex parts is narrowed. It is done. If the spacing below the convex portion is large, the proportion of the plane portion occupying the surface of the sapphire layer increases, and among the light incident from the light emitting layer (GaN layer) to the sapphire layer, the ratio of light incident on the plane portion at an angle smaller than the critical angle increases. . For this reason, the external quantum efficiency on the surface side (GaN layer side) from which light is emitted becomes low. On the other hand, when the spacing below the convex part is narrowed, the ratio of the convex part inclined surface which occupies the surface of the sapphire layer increases, and the ratio of the light incident on the sapphire layer at an angle smaller than the critical angle becomes smaller. For this reason, the external quantum efficiency of the surface side from which light comes out becomes high.

Therefore, ideally, the narrower the spacing below the convex portion, that is, the smaller the planar portion is preferable, but in the case of forming such a structure on the sapphire surface by plasma etching, the shape of making the planar portion sufficiently small in the conventional photomask forming method It was difficult to produce a photo mask.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for etching a sapphire substrate capable of forming a semiconductor light emitting device having excellent external quantum efficiency, and to provide a method for etching a sapphire substrate capable of suppressing the occurrence of burning or carbonization of photoresist. .

In order to solve the above problems, the present invention provides a method of etching a sapphire substrate which is formed by etching a UV light having a wavelength of 400 nm or less by forming a photoresist pattern on a sapphire substrate used in a semiconductor light emitting device. In

A prebaking step of heating the sapphire substrate at a temperature higher than that of the ultraviolet irradiation after the photoresist is applied and before the ultraviolet irradiation;

A post-baking step of heating the sapphire substrate at a higher temperature than the pre-baking step after irradiating ultraviolet rays,

After the post-baking step, an etching step of forming a plurality of convex portions having a sidewall angle of 90 ° or less on the sapphire substrate by dry etching using the photoresist pattern as a mask.

And FIG.

Moreover, the etching method of the sapphire substrate of this invention WHEREIN: It is characterized by forming many conical object or conical convex parts whose angle of the side wall with respect to the surface of the said sapphire substrate is less than 90 degrees.

In addition, the etching method of the sapphire substrate of the present invention is characterized in that the temperature at the time of ultraviolet irradiation is room temperature ~ 100 ℃, the heating temperature of the prebaking process is 120 ~ 130 ℃.

Furthermore, the etching method of the sapphire substrate of this invention is characterized by the heating temperature of a postbaking process being higher than the temperature of the sapphire substrate at the time of dry etching.

According to the etching method of the present invention, even if the sapphire substrate is not placed on the mounting table by the mechanical chuck or the electrostatic chuck, the burning and carbonization during the post-baking and the etching treatment can be eliminated while maintaining the photoresist shape. Etch rate can be obtained.

1 is a diagram schematically showing a cross-sectional structure of a semiconductor light emitting device having a convex portion of a conical object on a sapphire substrate surface.
It is a schematic block diagram which shows the plasma etching apparatus used for the etching method which concerns on one Embodiment of this invention.
3 is a flowchart schematically showing an etching method according to the present embodiment.
4 shows an SEM image of the sapphire substrate obtained in each step of the etching method according to Example 5, wherein (a) is initial (after prebaking), (b) is after postbaking, and (c) is SEM image after etching Respectively.
Fig. 5 shows SEM images of the sapphire substrates obtained in each step of the etching method according to Example 6, wherein (a) is initial (after prebaking), (b) is after postbaking, and (c) is SEM image after etching. Respectively.
6 shows an SEM image of the sapphire substrate obtained in each step of the etching method according to Example 8, wherein (a) is initial (after prebaking), (b) is after postbaking, and (c) is SEM image after etching Respectively.
7 (a) and 7 (b) show SEM images of the sapphire substrate obtained in each step of the etching method according to Comparative Example 3, (a) is the initial stage (after prebaking), and (b) is after ultraviolet irradiation. SEM images are shown respectively. (c) shows the SEM image after the ultraviolet irradiation of the etching method related to Comparative Example 4, (d) the photoresist thickness and photoresist at the initial (after prebaking) and after ultraviolet irradiation (150 ℃ and 200 ℃) The angle of the convex side wall is shown.
8 shows SEM images of the sapphire substrate obtained in each step of the etching method according to Example 9, (a) shows lithography, (b) shows prebaking, and (c) shows SEM images after plasma etching. .
9 shows SEM images of the sapphire substrate obtained in each step of the etching method according to Example 10, wherein (a) shows lithography, (b) shows prebaking, and (c) shows SEM images after plasma etching. .

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described, referring drawings.

1 shows an example of a cross-sectional structure of a gallium nitride compound semiconductor light emitting device (GaN semiconductor LED). The GaN semiconductor semiconductor 20 is formed by stacking an n-type GaN layer 22, a GaN active layer 23, and a p-type GaN layer 24 on a sapphire substrate 21. In the GaN semiconductor LED 20, in order to improve the external quantum efficiency, a photoresist pattern is formed on the sapphire substrate 21 and etched to form a plurality of convex portions 21a on the surface of the substrate, and then an n-type GaN layer. (22), the GaN active layer 23 and the p-type GaN layer 24 are laminated.

In this embodiment, the etching method mentioned later was used in order to form many convex parts 21a in the sapphire substrate 21.

2 shows a schematic configuration of a plasma etching apparatus 10 used in the etching method according to the present embodiment. The device is inductively coupled (ICP), in which the lower electrode 12 in the shape of a plate is enclosed in the sealed reaction chamber 11, and the excitation coil (14) is formed in the upper part (outside) of the reaction chamber 11 through a quartz plate 14. 15) are provided, respectively. The excitation coil 15 is a three-dimensional vortex (inverted tornado type) coil, and supplies high frequency electric power from the center of the coil, and the end of the coil outer circumference is grounded. The tray carrying the sapphire substrate 21 is placed on the lower electrode 12. In addition, the lower electrode 12 is connected to the high frequency power source 13. The lower electrode 12 has a built-in cooling mechanism for cooling the sapphire substrate and is controlled by the cooling control unit 17.

In the etching method of this embodiment, the formation process of the photoresist pattern shown in FIG. 3, the prebaking process, the UV-cure process (also called an ultraviolet irradiation process), the postbaking process, the etching process, and the removal process of the photoresist are performed in order. do. Novolak-type resin was used as a photoresist. The prebaking process is a process of evaporating the extra organic solvent in the resist apply | coated on the sapphire substrate. Although the temperature of a prebaking process is about 80-200 degreeC according to the kind of resist, in a novolak-type resin, it is about 120 degreeC. In the prebaking process, the sapphire substrate 21 to which the resist is applied is placed on a hot plate and prebaked for about 1 to 2 minutes at the above temperature. Thereafter, processing of exposure, development, washing, etc. of the pattern is performed to form a photoresist pattern.

In addition, in order to obtain the taper angle according to the design whose angle with respect to the said substrate surface of the convex side wall formed in the surface of the sapphire substrate 21 by the etching process mentioned later is less than 90 degrees, the said surface of the sapphire substrate 21 is It is preferable to form a mask (conical object) whose angle of the side wall with respect to the surface is less than 90 degrees (see Japanese Patent Laid-Open No. 2003-264171). However, in the sapphire substrate which needs to be etched with high frequency high frequency power, the UV-cure process and the post-baking process of this invention are required in order to harden a mask and not to burn or carbonize a mask during etching.

In the UV-cure process, the sapphire substrate after prebaking is placed on a mounting table of an ultraviolet irradiation device (not shown) temperature controlled to a temperature lower than the prebaking temperature, for example, 100 ° C, so that the surface of the sapphire substrate 21 After reaching | attaining 100 degreeC, the ultraviolet-ray whose wavelength is 400 nm or less was irradiated to the resist pattern for 20 minutes. The crosslinking reaction of a resist resin arises by ultraviolet irradiation. As a result, resist resin hardens | cures and the heat resistance of a resist pattern improves. Then, the temperature in an ultraviolet irradiation device was reduced to room temperature.

The post-baking process was performed by placing the sapphire substrate in which the photoresist pattern was formed on the mounting table of the said ultraviolet irradiation device, and controlling the temperature to temperature higher than a prebaking temperature, for example, 150-250 degreeC. As a result, the excess organic solvent remaining in the resist which could not be removed in the pre-baking process can be completely removed, and a strong mask which does not burn or carbonize even when the sapphire substrate is etched at a high power of high power can be formed. In addition, when the prebaking step is treated at the same temperature as the postbaking step, the solvent in the resist can be completely removed, but a desired pattern cannot be formed in the subsequent exposure or development step. In addition, when the UV-cure step is treated at the same temperature as the post-baking step, crosslinking of the resist resin and removal of the organic solvent occur at the same time, so that the crosslinking reaction of the monomer or the like in the resist resin does not sufficiently proceed or the resist pattern is deformed. .

In the etching step of the sapphire substrate, first, the air in the reaction chamber 11 is discharged while the sapphire substrate 21 is placed on the lower electrode 12 of the reaction chamber 11 of the plasma etching apparatus 10, The pressure in the reaction chamber is brought to a reduced pressure. Thereafter, Cl 2 gas, BCl 3 gas, Ar gas, and the like for etching the sapphire substrate are supplied to the reaction chamber 11 to adjust the gas pressure in the reaction chamber 11. The plasma 26 of the reaction gas is generated by supplying high-frequency high-frequency power to the excitation coil 15 and the lower electrode 12 for 10 minutes. The sapphire substrate is etched by the plasma 26 to form a conical object or conical convex portion whose angle of the side wall with respect to the surface of the sapphire substrate is less than 90 degrees.

Next, specific examples and comparative examples will be described.

Example  One

After apply | coating the novolak resin for photoresists on the sapphire substrate 21 by the rotation coating method, the said sapphire substrate 21 was mounted on the hotplate adjusted to 120 degreeC, and the prebaking was performed. Next, a large number of cone photoresist patterns were formed on the sapphire substrate 21 by lithography. At this time, the exposure conditions were adjusted so that the shape of the photoresist became a cone. Subsequently, the sapphire substrate 21 is placed on a mounting table temperature controlled at 100 ° C. using an ultraviolet irradiation device (device name: UV-1, manufactured by Samko Corporation), and the surface of the sapphire substrate 21 reaches 100 ° C. Thereafter, the resist pattern was irradiated with ultraviolet rays having a wavelength of 400 nm or less for 20 minutes. Then, after cooling the mounting base to room temperature, the mounting base of the said ultraviolet irradiation device was heated up at 150 degreeC, and post-baking was performed for 20 minutes. In addition, in the post-baking, the ultraviolet lamp of the ultraviolet irradiation device was not operated.

Subsequently, with the sapphire substrate 21 mounted on the lower electrode 12 of the reaction chamber 11 of the plasma etching apparatus 10, the air in the reaction chamber 11 is discharged and the inside of the reaction chamber 11 is removed. The pressure was 2 * 10 <-3> Pa. Thereafter, Cl 2 gas, BCl 3 gas, and Ar gas were supplied into the reaction chamber 11 at flow rates of 20 sccm, 50 sccm, and 40 sccm, respectively, and the gas pressure in the reaction chamber 11 was 0.7 Pa. Then, a high frequency power of 200W and 200W (ICP / Bias = 200 / 200W) was supplied to the excitation coil 15 and the lower electrode 12 for 10 minutes to generate a plasma 26 of the reaction gas. Etching was performed by this plasma 26.

Example  2

The sapphire substrate 21 was etched in the same manner as in Example 1 except that the postbaking was performed at 180 ° C.

Example  3

The sapphire substrate 21 was etched in the same manner as in Example 1 except that the postbaking was performed at 200 ° C.

Example  4

The sapphire substrate 21 was etched in the same manner as in Example 1 except that the postbaking was performed at 250 ° C.

Example  5

The etching was performed in the same manner as in Example 1 except that the high frequency powers of the excitation coil 15 and the lower electrode 12 were changed to 500W and 450W (ICP / Bias = 500 / 450W).

The SEM image of the sapphire substrate 21 obtained by the method of Example 5 is shown in FIG. Fig. 4 (a) shows an SEM image after prebaking (shown as “initial” in the figure), and Fig. 4 (b) shows a SEM image after postbaking (shown as “after bake” in the figure), and Fig. 4 ( c) is the SEM image after etching (it shows "after 500 / 450W process" in the figure.).

Example  6

The etching was performed in the same manner as in Example 2 except that the high frequency powers of the excitation coil 15 and the lower electrode 12 were changed to 500W and 450W (ICP / Bias = 500 / 450W).

The SEM image of the sapphire substrate 21 obtained by the method of Example 6 is shown in FIG. Fig. 5 (a) shows an SEM image after prebaking (shown as “initial” in the drawing), and Fig. 5 (b) shows a SEM image after postbaking (shown as “after 180 ° C baking” in the figure), and Fig. 5 (c) is an SEM image after etching (in the drawing, “after 500/450 W processing”).

Example  7

The etching was performed in the same manner as in Example 3 except that the high frequency powers of the excitation coil 15 and the lower electrode 12 were changed to 500W and 450W (ICP / Bias = 500 / 450W).

Example  8

The etching was performed in the same manner as in Example 4 except that the high frequency powers of the excitation coil 15 and the lower electrode 12 were changed to 500W and 450W (ICP / Bias = 500 / 450W).

The SEM image of the sapphire substrate 21 obtained by the method of Example 8 is shown in FIG. Fig. 6 (a) shows an SEM image after prebaking (shown as “initial” in the figure), and Fig. 6 (b) shows a SEM image after postbaking (in the figure, “after 250 ° C. bake”), and Fig. 6 (c) is an SEM image after etching (in the drawing, “after 500/450 W processing”).

Comparative Example 1

The sapphire substrate 21 was etched in the same manner as in Example 1 except that the postbaking was not performed.

Comparative Example 2

The etching was performed in the same manner as in Comparative Example 1 except that the high frequency powers of the excitation coil 15 and the lower electrode 12 were changed to 500W and 450W (ICP / Bias = 500 / 450W).

[Comparative Example 3]

Except having made the prebaking temperature 130 degreeC and the ultraviolet irradiation temperature 150 degreeC, it carried out similarly to Example 1, but the shape of the photoresist changed after ultraviolet irradiation.

For this reason, post-baking and etching process were not performed.

SEM images of the sapphire substrate 21 obtained by the method of Comparative Example 3 are shown in Figs. 7A and 7B. Fig. 7 (a) shows an SEM image after prebaking (in the drawing, “initial (after prebaking)”), and Fig. 7 (b) shows an SEM image after ultraviolet irradiation (in the drawing, “UV at 150 ° C.”). )to be. After the prebaking process, a resist pattern made of a plurality of convex portions of the cone is formed on the sapphire substrate. After the prebaking process, the photoresist had a convex portion of the cone, and the thickness was 1.5 µm. However, after ultraviolet irradiation, the shape of the photoresist changed and the thickness became 1.3 μm. In addition, after prebaking, the angle of the side wall of the convex part of the photoresist with respect to the surface of the sapphire substrate was 70 degrees. However, the said angle became 65 degrees after ultraviolet irradiation. Thus, when ultraviolet irradiation was performed at 150 degreeC, the shape of the resist pattern changed.

[Comparative Example 4]

Except having changed the ultraviolet irradiation temperature into 200 degreeC, it carried out similarly to the comparative example 3, The shape of the photoresist changed after ultraviolet irradiation. For this reason, post-baking and etching process were not performed.

FIG.7 (c) shows the SEM image of the sapphire substrate after ultraviolet irradiation obtained by the method of the comparative example 4 (it shows "UV at 200 degreeC" in the figure.). The SEM image after prebaking becomes the same FIG. 7A as Comparative Example 3. FIG. In the same manner as in Comparative Example 3, after the prebaking process, a resist pattern made up of convex portions of a plurality of cones was formed on the sapphire substrate, and the thickness of the convex portions was 1.5 μm. However, after ultraviolet irradiation, the shape of the photoresist changed and became 0.4 micrometer in thickness. After the prebaking, the angle of the sidewall of the convex portion of the photoresist with respect to the surface of the sapphire substrate was 70 degrees, but after the ultraviolet irradiation, the angle was 25 degrees. Thus, when ultraviolet irradiation was performed at 200 degreeC, the shape of the resist pattern changed remarkably. 7D shows the photoresist thickness and the angle of the photoresist convex sidewalls at the initial stage (after prebaking) and after ultraviolet irradiation (150 ° C and 200 ° C).

Table 1 summarizes the evaluation results of the photoresist state of the surface of the sapphire substrate 21 after the etching of Examples 1 to 8 and Comparative Examples 1 to 4 and the formation state of the convex portion of the conical object on the surface of the sapphire substrate 21. to be. Moreover, about each Example, the shape evaluation and the burning evaluation of the photoresist after postbaking were also performed.

The criteria for each evaluation are listed below the table.

Shape Evaluation of Photoresist After Postbaking Scoring evaluation of photoresist after postbaking Photoresist state of substrate surface after etching Evaluation of taper shape of sapphire substrate after etching Etching rate
(nm / min) Example 1 ○ ○ ○ ○ Unmeasured Example 2 ○ ○ ○ ○ Unmeasured Example 3 ○ ○ ○ ○ Unmeasured Example 4 ○ ○ ○ ○ Unmeasured Example 5 ○ ○ ○ ○ 55 Example 6 ○ ○ ○ ○ 70 Example 7 ○ ○ ○ ○ 80 Example 8 Δ ○ ○ ○ 100 Comparative Example 1 - - × × 35 Comparative Example 2 - - × × Unmeasured Comparative Example 3 - - - - - Comparative Example 4 - - - - -

(1) Evaluation criteria for shape of photoresist after postbaking

X: The shape changed compared with the shape after prebaking.

Δ: The shape was almost maintained as compared with the shape after the prebaking.

(Circle): The shape was maintained compared with the shape after prebaking.

(2) Evaluation criteria for the burning of photoresist after post-baking

X: The photoresist burned out.

(DELTA): Although the etching has no influence, the photoresist burns.

(Circle): The photoresist did not burn.

(3) Evaluation criteria for burning or carbonization of photoresist after etching

X: The photoresist burned or carbonized.

(DELTA): Although the etching has no influence, the photoresist burned or carbonized.

○: The photoresist was not burned or carbonized.

(4) Tapered shape evaluation criteria of sapphire substrate after etching

X: The tapered convex part whose angle of the side wall with respect to a board | substrate surface is less than 90 degrees was not able to be formed.

(Circle): The taper-shaped convex part whose angle of the side wall with respect to a board | substrate surface is less than 90 degrees was formed.

Example  9

After apply | coating the novolak resin for photoresists on the sapphire substrate 21 by the rotation coating method, the sapphire substrate 21 was mounted on the hotplate adjusted to 120 degreeC, and baking was performed. Next, a photoresist pattern of a columnar shape (height 3.0 μm, bottom face diameter 2.2 μm) was formed on the sapphire substrate 21 by lithography (see Fig. 8 (a)). Then, the temperature of a hot plate was adjusted to 160 degreeC, and the prebaking was performed. The extra organic solvent in the photoresist evaporated by the prebaking process, and at the same time, the photoresist pattern, which was circumferential, was deformed into a hemispherical shape (height 2.0 mu m, bottom face diameter 3.0 mu m) (Fig. 8 (b)).

Subsequently, the sapphire substrate was placed on a mounting table temperature controlled at 155 ° C using an ultraviolet irradiation device, and the ultraviolet light was irradiated for 5 minutes after the surface of the sapphire substrate reached 155 ° C. The used ultraviolet irradiation device and the ultraviolet wavelength were the same as in Example 1.

Then, the mounting table of the ultraviolet irradiation device was heated up at 250 degreeC, and post-baking was performed for 5 minutes. In addition, in the post-baking, the ultraviolet lamp of the ultraviolet irradiation device was not operated. The shape of the photoresist pattern after post-baking was hemispherical of 2.0 micrometer in height and 3.0 micrometer in bottom face diameter, and did not change into the shape after prebaking.

Thereafter, Cl 2 is added to the reaction chamber of the plasma etching apparatus. Gas, BCl 3 gas, and Ar gas were supplied at flow rates of 20 sccm, 30 sccm, and 20 sccm, respectively, so that the gas pressure in the reaction chamber 11 was 0.7 Pa, 500 W and 450 W (ICP /) to the excitation coil 15 and the lower electrode 12. Etching was carried out in the same manner as in Example 1 except that high frequency power of Bias = 500 / 450W) was supplied for 15 minutes. As a result, as shown in Fig. 8C, after the plasma treatment, conical convex portions were formed on the surface of the sapphire substrate. The height of the convex convex portion was 1.7 µm and the bottom diameter was 3.5 µm.

Example  10

Conical convex portions were formed on the surface of the sapphire substrate in the same manner as in Example 9 except that the prebaking temperature was 100 ° C and the temperature at the time of ultraviolet irradiation was 95 ° C. As shown in Fig. 9 (a), also in Example 10, the photoresist pattern formed on the sapphire substrate by lithography was columnar (height 3.0 µm, bottom face diameter 2.2 µm). On the other hand, as shown in FIG.9 (b), the shape of the photoresist pattern after prebaking was a columnar shape with a height of 3.0 micrometers, and a bottom part diameter of 2.2 micrometers. That is, in Example 10, unlike Example 9, the shape of the photoresist pattern did not change by prebaking. On the other hand, after the plasma treatment, conical convex portions were formed on the surface of the sapphire substrate as in Example 9 (see Fig. 9 (c)). The height of the convex convex portion was 1.9 µm and the bottom diameter was 2.4 µm.

In the above embodiments and examples, the present invention has been described in which the sapphire substrate is etched to form a convex portion or a conical convex portion of a conical object whose angle of the side wall with respect to the surface of the sapphire substrate is less than 90 °. Is not limited to this. For example, the present invention can also be applied to the case where a large number of convex portions having sidewalls perpendicular to the surface of the sapphire substrate are formed. In addition, the convex portion can be applied to a case where a large number of convex portions of the pyramidal object and a long elongated convex portion are formed in addition to the conical object.

20... GaN-based semiconductor LED
21 ... Sapphire Substrate
21a ... Convex portion
22... n-type GaN layer
23 ... GaN active layer
24 ... p-type GaN layer

Claims (6)

In the etching method of a sapphire substrate which forms a photoresist pattern on the sapphire substrate used for a semiconductor light emitting element, irradiates the ultraviolet-ray with a wavelength of 400 nm or less, and dry-etchs using the said photoresist pattern as a mask,
A prebaking step of heating the sapphire substrate at a temperature higher than that of the irradiation of the ultraviolet rays after applying the photoresist, and before irradiating the ultraviolet rays,
A post-baking step of heating the sapphire substrate at a higher temperature than the pre-baking step after irradiating ultraviolet rays,
After the post-baking step, an etching step of forming a plurality of convex portions having a sidewall angle of 90 ° or less on the sapphire substrate by dry etching using the photoresist pattern as a mask is performed.
Etching method of sapphire substrate characterized by including. The method according to claim 1,
The etching process is a method of etching a sapphire substrate, characterized in that a large number of conical or conical convex portions having an angle of less than 90 degrees with respect to the surface of the sapphire substrate. The method according to claim 1 or 2,
The temperature at the time of ultraviolet irradiation is room temperature-100 degreeC, and the heating temperature of a prebaking process is 120-130 degreeC, The etching method of the sapphire substrate characterized by the above-mentioned. The method according to any one of claims 1 to 3,
The heating temperature of a post-baking process is higher than the surface temperature of the sapphire substrate in a dry etching process, The etching method of the sapphire substrate. The method according to any one of claims 1 to 4,
The heating temperature of a postbaking process is 200 degreeC or more, The etching method of the sapphire substrate characterized by the above-mentioned. The method according to any one of claims 1 to 5,
A method for etching a sapphire substrate, wherein the sapphire substrate is returned to room temperature after the ultraviolet ray irradiation and before the postbaking step.
KR1020137008188A 2010-09-10 2011-03-07 Method for etching sapphire substrate KR20130108572A (en)

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JP6225445B2 (en) * 2013-03-26 2017-11-08 東レ株式会社 Photoresist for dry etching, relief pattern using the same, and method for manufacturing light emitting device
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