JP3473977B2 - Method of forming LED array - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an LED array.

[0002]

2. Description of the Related Art When an LED array is formed, a light emitting diode (L) is formed between a first conductive type semiconductor substrate and the substrate.
It is necessary to form a large number of second conductivity type impurity diffusion regions forming a pn junction for ED) in an array. In that case,
An insulating film having an opening is used as a diffusion preventing film having a function of exposing a portion of the substrate where a second conductivity type impurity region (for example, p-type impurity diffusion region) is formed and covering the other portion, and the impurity diffusion Is done. Then, an electrode is formed on the surface portion of the insulating film through the opening of the insulating film so as to be connected to the p-type impurity diffusion region. As a conventional example of a method for forming an LED array including the step of forming openings and electrodes of such an insulating film, there is one disclosed in Document I (Document I: JP-A-5-67807 “LED element”). ).

FIG. 6A is a plan view of a conventional LED array disclosed in Document I, and FIG. 6B is a sectional view taken along line XX in FIG. 6A. Is shown.

In the method of forming an LED array disclosed in Document I, an insulating film 42 is formed on an N-type semiconductor substrate 40,
The diffusion prevention film is formed by providing the opening 43 in the insulating film 42. After that, a diffusion protective film (evaporation preventing film of constituent elements of the compound semiconductor substrate, not shown) is formed on the sample by any suitable method to diffuse zinc. At this time, the p-type diffusion region 44a is formed on the substrate 40. This p-type diffusion region 44a becomes a part of the constituent components of the light emitting section.
Note that 44b is the same p-type diffusion region as 44a, but is used as a defect detection pattern. Also,
An electrode 46 is formed on the insulating film 42, and the substrate 40
An N-type electrode 48 is formed on the back surface of the.

In the LED array of the above-mentioned document I, the planar shape of the opening 43 of the insulating film 42 is a square or a rectangle, and the electrode 46 partially overlaps the p-type diffusion region 44a. It is formed and has a plane shape of an L-shape or an inverted T-shape.

[0006]

By the way, when forming an LED array, it may be more convenient to perform the etching for forming the opening 43 in the insulating film 42 by wet etching for the convenience of the process. . For example, when alumina is used as the insulating film, wet etching is used because it is difficult to dry-etch the alumina. In addition, it may be more convenient to perform patterning of the electrodes by wet etching for the convenience of the process.

However, in the conventional method of forming an LED array, the resist pattern used for forming the opening 43 in the insulating film 42 has an opening having a quadrangular planar shape, and the electrode 46 is formed. Each of the resist patterns for use had an island shape such as an L-shape or an inverted T-shape in plan view, and the corner portions of the resist pattern were all right angles or substantially right angles. Therefore,
When the insulating film 42 and the electrode forming thin film are etched by the wet etching method in the lithography process, the chemical solution stays at the corners of the resist pattern due to the surface tension of the chemical (etchant). The part and the thin film part for electrode formation cannot be removed well. Therefore, it has been found that there is a problem that the opening 43 and the electrode cannot faithfully reproduce the shape as designed. If the planar shape of the opening 43 itself varies, the area of the second conductivity type impurity diffusion region (light emitting portion) varies, and if the planar shape of the electrode 46 varies, the second conductivity type impurity diffusion region. Since the exposed area of the (light emitting section) is varied, in any case, the area of the light emitting section varies, which causes variation in the light emission amount of the LED array. In particular, when the LED array is integrated with high density to reduce the light emitting area, the variation of the light emitting area has been a serious problem.

This application has been made in view of the above-mentioned problems, and an object of this application is to make it possible to reduce the variation in the shape of the opening of the insulating film as compared with the conventional LED.
It is to provide a method for forming an array.

[0009]

In order to achieve the object of the present invention, the LED array forming method of the present invention has the following features. That is, a step of forming an insulating film on a semiconductor substrate, a step of forming a resist pattern having an opening for forming a light emitting portion of an LED array on the insulating film, and a portion of the insulating film exposed from the opening are wet. In the method for forming an LED array, which includes a step of removing by an etching method and a step of diffusing impurities in a semiconductor substrate portion exposed by removing the insulating film to form an impurity diffusion region for a light emitting portion, Is formed into a shape having no corners, a shape having rounded corners, or a shape having at least two obtuse angles at the corners, and the impurity diffusion region is substantially a region not covered with the insulating film. Provide the same size.

[0010]

[0011]

[0012]

In carrying out the present invention, the shape of the opening of the resist pattern is such that the etchant is fluidized, that is, there is no corner, the corner is rounded,
Alternatively, whether the corner has a shape having at least two obtuse angles may be determined according to the design. For example, in the case of a resist pattern for forming openings in an insulating film, it is considered that it is preferable that all the openings have the above-mentioned shape for fluidizing the etchant, but in the case of an island-shaped resist pattern, It is considered preferable that the shape on the side that is convex on the resist side is one that facilitates fluidization of the etchant.

[0014]

According to the above-described structure of the present invention, when the opening is formed in the insulating film, the insulating film is formed on the semiconductor substrate,
A resist pattern having an opening for forming a light emitting portion of the LED array is formed on this insulating film. As the resist pattern for forming the light emitting portion, the shape of the opening of the resist pattern is a shape for fluidizing an etchant used in the wet etching method, a shape without corners, a shape with rounded corners or a corner. A part whose shape has at least two obtuse angles is used. In this way, since the shape of the opening is formed so that the etchant can be easily fluidized, the etching solution is prevented from staying at a specific place in the opening of the resist pattern. Therefore, since the inside of the opening can be uniformly etched, the variation in the area of the light emitting portion can be reduced.

In this preferred embodiment, when the opening of the insulating film is formed, the shape of the opening of the insulating film can be made uniform by using the wet etching method.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming an LED array according to the present invention will be described below with reference to the drawings. It should be noted that the drawings merely schematically show the shapes, sizes, and arrangements of the respective constituent components to the extent that the present invention can be understood. Prior to the method of forming the LED array, the opening of the resist pattern used in the present invention and the photomask pattern for forming the resist pattern will be described.

First, FIGS. 1A to 1C show a resist pattern for forming an opening of an insulating film used in the first embodiment of the present invention, a photomask pattern for the resist pattern (however, for a negative type). And the shape of the insulating film at the opening.

FIG. 1A shows a plan view of a resist pattern having an opening for forming a light emitting portion. The shape of the resist pattern having the openings has the openings 15, and the four corners of the quadrangle are rounded with a radius r.

FIG. 1B shows the plane of the photomask pattern used when forming the resist pattern of the opening. An opening pattern (hatched portion) 26 is formed in the opening photomask pattern 24.
The opening pattern 2 of this opening photomask pattern
6 has rounded corners with a radius r as at the four corners.

After removing the insulating film 14 formed on the semiconductor substrate by etching using the resist pattern of the opening and the photomask pattern for the opening described above,
The opening 17 is formed in the insulating film 14 ((C) of FIG. 1).

At this time, the corners of the opening 17 of the insulating film 14 have a rounded shape with a radius r.

On the other hand, (A) to (C) of FIG.
The shape of the electrode patterning resist pattern, the electrode photomask pattern, and the electrode used when forming the electrode of the example is shown. Since the electrode patterning resist pattern 22 has an island shape, it is also referred to as an island resist pattern.

FIG. 2A shows the shape of the electrode patterning resist pattern. This electrode patterning resist pattern 22 has corners with radii r ₁ , r ₂ ,
It has a roundness of r ₃ and is formed so as to partially overlap the opening 17 of the insulating film 14. A peripheral portion of the electrode patterning resist pattern 22 is composed of the electrode forming thin film 19.

FIG. 2B shows a photomask pattern for electrodes. Photomask pattern 2 for this electrode
8 has an electrode pattern 30 (hatched portion) having the same shape as the electrode patterning resist pattern 22.

2C shows an electrode forming thin film 19 using a resist pattern 22 for electrode patterning.
The electrode 20 formed when the film is removed by etching is shown. Here, the electrode 20 is composed of an electrode lead portion 20a and a wire bonding pad 20b.

Next, the shapes of the resist pattern of the opening and the resist pattern for electrode patterning used in the second embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B).

Openings 15 are formed in the resist pattern 16 of the second embodiment, and the four corners of the openings 15 have two obtuse angles α and β ((A) of FIG. 3). ).

Further, the corner portions of the electrode patterning resist pattern 22 of the second embodiment are formed with obtuse angles α and β, and the electrode patterning resist pattern 2 is formed.
The peripheral portion of 2 is composed of an electrode forming thin film 19 ((B) of FIG. 3).

Next, the forming method of the present invention will be described with reference to FIGS. 4A to 4C and 5A to 5C.

As the semiconductor substrate 10, an intermediate layer in which the composition between the substrate and the GaAsP growth layer is stepwise changed is provided on a GaAs substrate, and an N-type GaA having a desired composition is provided thereon.
A substrate on which an sP layer is epitaxially grown (hereinafter referred to as GaA
It is called sP / GaAs substrate. ) Is used. This GaAs
An insulating film 14 is formed on the P / GaAs substrate 10 (see FIG. 4).
(A)). At this time, the insulating film is an alumina film (Al ₂ O ₃
Film) and its film thickness is, for example, 2000 A ° to 3000 A
(The symbol A ° represents angstrom).

Next, a resist pattern 16 having an opening 15 is formed on the insulating film 14 by using the photolithography method (FIG. 4B). At this time, the photomask pattern used when forming the resist pattern 16 has the shape shown in FIG. After that, the resist pattern 16 in the opening is used as an etching mask to remove a part of the insulating film 14 by a wet etching method (FIG. 4C). The conditions of the wet etching at this time are as follows.

Etching solution: hot phosphoric acid solution Etching temperature: 80 ° C. to 85 ° C. Etching time: about 2 minutes By this etching, the opening 17 of the insulating film 14 is formed. The shape of the opening 17 of the insulating film 14 formed at this time is a shape having rounded corners at the four corners as shown in FIG.

Next, after forming, for example, a PSG film (not shown) on the GaAsP / GaAs substrate, impurities are diffused to form an impurity diffusion region 18 (A in FIG. 5). The impurity diffusion region 18 is also called a light emitting portion.

Next, after removing the PSG film by using any suitable method, the insulating film 14 and Ga having the opening 17 and Ga are removed.
An electrode forming thin film 19 is formed on the AsP / GaAs substrate 10 so as to cover the entire surface by, for example, the EB vapor deposition method (FIG. 5B). Al as the thin film 19 for forming the electrode
A film is used, and the film thickness is set to 1.5 μm to 2.5 μm.

Next, after applying an arbitrary suitable resist on the electrode forming thin film 19 (not shown) and drying it, the electrode forming thin film 19 is removed by etching using a photolithography method, and then the electrode forming thin film 19 is formed. The lead portion 20a is formed ((C) of FIG. 5). The photomask pattern for electrodes used in the photolithography process at this time is as shown in FIG.
(B) of FIG. Therefore, the shape of the electrode patterning resist pattern 22 formed in the exposure step is
As in the case of FIG. 2B, the electrode patterning resist pattern has rounded corners. After that, the electrode patterning resist pattern 22 is used as a mask by using a wet etching method to remove the electrode forming thin film 19 to form an electrode lead portion 22a and a wire bonding pad 20b (see FIG. 2C). . Here, as the electrode patterning resist pattern, an island-shaped resist pattern corresponding to the shape of the electrode is used, and the corner portions have a shape for fluidizing the etchant used in the wet etching. In the configuration using the resist pattern, the flow of the etching solution to the corners of the island-shaped resist pattern is improved as in the case of the etchant for the opening described above, so that the etching solution does not stay in the corners of the resist pattern. , The shape of the electrode becomes uniform. For this reason, the shape of the electrode (the electrode at this portion is called the electrode lead-out portion) in the portion connected to the light emitting portion through the opening of the insulating film becomes uniform, so that the light emission amount of the LED array can be made uniform. . Further, since the electrode shape can be faithfully reproduced with respect to the design value, there is an advantage that the resistance of the electrode and the capacitance between the front surface electrode and the back surface electrode formed via the substrate can be controlled.

LED formed through the above-mentioned forming process
The openings of the insulating film of the array and the electrodes have no corners, and the openings and the electrodes can be formed uniformly over the entire LED array of the light emitting section. Therefore, since the area of the light emitting portion can be made uniform, it is possible to manufacture an LED array in which the emission intensity of the LED array does not vary.

The first embodiment of the present invention described above is an example in which the openings 17 of the insulating film 14 and the corners of the electrodes 20 are rounded. However, the second embodiment ((in FIG. 3). The corners described in (A) and (B)) may have obtuse angles. In this case, the opening of the insulating film and the electrode are formed in the same manner as in the forming method of the first embodiment.

[0038]

As is apparent from the above description, according to the method of forming an LED array of the present invention, a corner portion of an opening is used in wet etching as a resist pattern having an opening for forming a light emitting portion. A resist pattern having a shape for fluidizing the etchant is used.
For this reason, the wet etching liquid easily flows even to the corners, and the shape of the opening of the insulating film becomes uniform.
Therefore, it is considered that the variation in the area of the light emitting portion of the LED array is reduced and the variation in the light emission amount can be suppressed.

Further, as the electrode patterning resist pattern, an island-shaped resist pattern corresponding to the shape of the electrode is formed, and the corner portions are shaped to fluidize the etchant used in the wet etching. In the configuration using the resist pattern, as in the case of the etchant for the opening described above, the flow of the etching solution to the corners of the island-shaped resist pattern is improved, so that the etching solution does not stay at the corners of the resist pattern. , The shape of the electrode becomes uniform. Therefore, the shape of the electrode (the electrode in this portion is referred to as the electrode lead-out portion) in the portion connected to the light emitting portion through the opening of the insulating film becomes uniform, so that LE
The light emission amount of the D array can be made uniform. Further, since the electrode shape can be faithfully reproduced with respect to the design value, there is an advantage that the resistance of the electrode and the capacitance between the front surface electrode and the back surface electrode formed via the substrate can be controlled.

[Brief description of drawings]

FIG. 1A is a plan view of a resist pattern in an opening of a first embodiment of the present invention, and FIG. 1B is a plan view of a photomask pattern for an opening in a resist pattern.
Further, (C) is a plan view for explaining the shape of the insulating film.

FIG. 2A is a plan view of an electrode patterning resist pattern according to the first embodiment of the present invention, and FIG. 2B is a plan view of an electrode photomask pattern used in a photolithography process. Further, (C) is a plan view for explaining the shape of the electrode.

FIG. 3A is a plan view of a resist pattern in an opening of a second embodiment of the present invention, and FIG. 3B is a plan view provided for explaining the shape of a resist pattern for electrode patterning.

4 (A) to (C) are L of the first embodiment of the present invention.
FIG. 6 is a process chart provided for explaining a method for forming an ED array.

5A to 5C are process diagrams provided for explaining the method for forming the LED array of the first embodiment of the present invention, which is subsequent to FIG.

6A is a plan view of a conventional LED array, and FIG. 6B is a cross-sectional view taken along line XX shown in FIG.

[Explanation of symbols]

10: N-type GaAsP / GaAs substrate 14: Insulating film 15: opening 16: Resist pattern 17: opening 18: Impurity diffusion region (light emitting portion) 19: Thin film for electrode formation 20a: electrode lead-out part 20b: Wire bonding pad 20: Electrode 22: Resist pattern for electrode patterning 24: Photomask pattern for opening 26: Opening pattern 28: Photomask pattern for electrodes 30: Electrode pattern

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Shimizu               1-7 Toranomon, Minato-ku, Tokyo Okiden               Ki Industry Co., Ltd. (72) Inventor Masumi Yanaka               1-7 Toranomon, Minato-ku, Tokyo Okiden               Ki Industry Co., Ltd.                (56) References JP-A-2-178980 (JP, A)                 JP-A-53-135585 (JP, A)                 JP-A-57-56935 (JP, A)                 JP-A-4-264780 (JP, A)

Claims (3)

(57) [Claims] 1. A step of forming an insulating film on a semiconductor substrate, a step of forming a resist pattern having an opening for forming a light emitting portion of an LED array on the insulating film, and the step of exposing from the opening. An LED array comprising: a step of removing an insulating film portion by a wet etching method; and a step of diffusing impurities in the semiconductor substrate portion exposed by removing the insulating film to form an impurity diffusion region for a light emitting portion. In the forming method, the shape of the opening is formed to have no corner, a corner having a rounded shape, or a corner having at least two obtuse angles, and the impurity diffusion region is provided with the insulating layer. A method for forming an LED array, which comprises providing a region substantially the same as a region not covered with a film. 2. The method of forming an LED array according to claim 1, wherein a step of forming an electrode forming thin film on the semiconductor substrate, a step of forming an electrode forming resist pattern on the thin film, Patterning a thin film to form the electrode having one end of the thin film connected to the light emitting portion, wherein at least a part of a corner portion of the electrode provided in the impurity diffusion region is rounded. A method for forming an LED array, which is characterized in that the LED array is formed into a shape having 3. The method of forming an LED array according to claim 1, wherein the etching solution used in the wet etching method is hot phosphoric acid.