JP2001085740A - Method for designing mask dimension of surface-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for designing a mask dimension at the formation of metallic wiring by etching for making the width of the metallic wiring smaller than that of an ohmic electrode, and making it larger than that of a contact hole. SOLUTION: At the formation of an Al wiring 20 by etching using a mask 24, if the width of the mask 24 is defined as W, W is selected so that the inequalities L+2(S+dS)+a>W>C+2(S+dS)+2a (L is the width of an Au electrode 14, C is the width of a contact hole 18, S is the width of the etching quality of the side face of the Al wiring, dS is the fluctuation of the etching quantity, and (a) is the deviation of the alignment of the mask) is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a mask dimension for obtaining a metal wiring shape in which a variation in external light emitting efficiency of a surface light emitting element is suppressed.

[0002]

2. Description of the Related Art In a surface light emitting device such as a surface emitting light emitting diode, an electrode for injecting current necessarily covers a part of the light emitting surface, so that the decrease in external light emitting efficiency is small and the light emitting surface is small. A structure that emits light as uniformly as possible is required. FIG. 1 shows an example of the structure of a mesa light emitting diode satisfying such a requirement. (A) is a plan view and (B) is a sectional view.

In this light-emitting diode, an Au electrode 14 in ohmic contact is provided at the center of the pn junction surface of a light-emitting portion 12 made of a semiconductor layer formed on a substrate 10;
The entire light emitting surface is covered with a transparent insulating film 16. A hole is formed in this insulating film to form a contact hole 18, and a metal (Al) wiring 20 is provided thereon.

According to this structure, since the ohmic electrode 14 is provided at a symmetrical position at the center of the light emitting surface, the uniformity of light emission is good, and the area of this electrode is reduced (for example, for a light emitting portion of 20 μm square). (5 μm square) can prevent a decrease in external luminous efficiency.

[0005]

SUMMARY OF THE INVENTION An ohmic electrode (A
Since u) generally needs only to have a thickness of about 0.1 μm,
Patterning can be performed with high repeatability (± 0.5μ
m), since the upper Al wiring passes through the step of the mesa when it goes out of the light emitting portion, it needs to be formed to a thickness of about 1 μm to prevent disconnection. The patterning accuracy of the Al film having such a thickness is not good (about ± 1 μm). This is because when etching Al, the pattern side surface is etched. Due to the variation in etching of the Al side surface, the width of the Al electrode may be wider than the Au electrode as a result of patterning. In this case, light output is reduced due to light shielding by the Al wiring. In particular, when the light emitting diodes are formed into an array and applied to an optical print head, there is a problem that the light output becomes a major cause of variation in light output between elements.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for designing a mask dimension when etching a metal wiring so that the width of the metal wiring can be made smaller than the width of the ohmic electrode and larger than the width of the contact hole. Is to provide.

[0007]

According to the present invention, a metal electrode which is in ohmic contact with a light emitting portion comprising a semiconductor layer formed on a substrate is connected to a metal wiring via a contact hole formed in an insulating film. A method for designing mask dimensions when forming the metal wiring by etching using a mask, wherein the width of the mask is W
L + 2 (S + dS) + a>W> C + 2 (S + dS) +2
a where L is the width of the metal electrode, C is the width of the contact hole, S is the width of the etching amount on the side surface of the metal wiring, dS is the variation of the etching amount, and a is the misalignment of the mask. As described above, this is a method of designing a mask dimension characterized by selecting W.

According to such a mask dimension designing method,
Since the width of the metal wiring can be made smaller than the width of the ohmic electrode, it is possible to suppress variations in external luminous efficiency.

[0009]

FIG. 2 is a view showing a light emitting diode according to an embodiment of the present invention, wherein (A) is a plan view and (B).
Is a sectional view. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals.

The Al electrode is patterned so that the width of the Al electrode 20 is smaller than the width of the Au electrode.
The design dimensions of the mask dimensions when patterning such an Al electrode 20 will be described in detail below with reference to FIG. FIG. 3 shows an Au electrode, a contact hole, and an Al electrode.
The positional relationship of the wiring mask is shown.

Here, the width of the Au electrode 14 on the semiconductor layer 12 is L. This electrode pattern has a small dimensional variation to be formed by the lift-off method. Next, the insulating film 16
To form a contact hole 18 having a width C.
Since the holes are formed by dry etching, variations in the width C are small. However, the position of the contact hole 18 is set at the center line 22 of the Au electrode 14 due to misalignment of the mask.
From the maximum ± a. Next, Al is deposited and the mask 24 is deposited.
Is provided and Al is patterned. The width of the mask 24 at this time is W. Al is 1μ thick to prevent disconnection
Therefore, when patterning is performed using this mask and etching is performed using a phosphoric acid-based etchant, etching of the side surface of the wiring portion proceeds while Al in an unnecessary portion is removed, and the etching proceeds in comparison with the mask width W. Finished Al
The width W 'becomes smaller. Now, let S be the etching amount (width) of the side surface of the wiring. However, a variation ± dS occurs in this etching amount. Considering these, W ′ = W−2 (S ± dS) (1)

For the purpose of the present invention, in order to suppress variations in external light emission efficiency, it is necessary to prevent the Al wiring 20 from protruding outside the Au electrode 14. As long as W 'is smaller than L, the alignment of the Al wiring mask 24 with respect to the center line 22 of the Au electrode 14 may be shifted by ± a as in the case of the contact hole mask. Therefore, the required condition is L> W−2 (S + dS) −a (2) in consideration of the worst state. However, the width of the Al wiring 20 is reduced, and any edge of the Al wiring must not overlap the contact hole 18. In consideration of this, it is necessary to determine the width W of the Al wiring mask 24 such that L> W−2 (S + dS) −a> C + a (3) Rewriting the above equation, L + 2 (S + dS) + a>W> C + 2 (S + dS) + 2a (4) Now, a design example in the case of manufacturing a light emitting diode with L = 10 μm and C = 3 μm is as follows. S is about 1 μm,
Assuming that dS is about 0.5 μm and a is about 1 μm, and substituting this into Equation (4), the mask width W should be 9 to 14 μm. The central value of this range is 11.5 μm
W was selected in a suitable manner, and a light emitting diode was produced.

According to the design of the mask dimensions as described above,
Even if the patterning of Al varies, the Al wiring 2
Since 0 does not come out of the Au electrode 14 and the light shielding always occurs with the Au electrode having a stable size, the variation in the external luminous efficiency is small.

The variation M of the light output when the n light emitting diodes are arranged in an array is expressed as follows: M = (maximum light output−minimum light output) / average light output × 100
(%), The typical value of the conventional example is about 15% when n = 128, but is reduced to about 10% according to the Al wiring formed by the mask according to the mask dimension designing method of the present invention. did.

In the above embodiment, the surface light emitting diode has been described as an example. However, the present invention is not limited to a diode.
It will be apparent to those skilled in the art that it is generally applicable to surface emitting devices such as n-type surface emitting thyristors.

[0016]

According to the mask dimension designing method of the present invention, since the width of the metal wiring can be made smaller than the width of the ohmic electrode, it is possible to suppress variations in external light emission efficiency.

[Brief description of the drawings]

FIG. 1 is an example of a structure of a mesa light emitting diode,
(A) is a plan view and (B) is a sectional view.

FIG. 2 is a view showing a light emitting diode according to the present invention;
(A) is a plan view and (B) is a sectional view.

FIG. 3 is a diagram showing a positional relationship between an Au electrode, a contact hole, and a mask.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 12 Light emitting part 14 Au electrode 16 Insulating film 18 Contact hole 20 Metal (Al) wiring

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiji Ohno 3-5-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka F-term in Nippon Sheet Glass Co., Ltd. 5F041 AA14 CA12 CA74 CA77 CA98 CB22

Claims (3)

[Claims] 1. A surface-emitting device in which a metal electrode in ohmic contact with a light-emitting portion formed of a semiconductor layer formed on a substrate is connected to a metal wiring via a contact hole formed in an insulating film. This is a method of designing a mask dimension when wiring is formed by etching using a mask, where W is the width of the mask, and L + 2 (S + dS) + a>W> C + 2 (S + dS) +2
a where L is the width of the metal electrode, C is the width of the contact hole, S is the width of the etching amount on the side surface of the metal wiring, dS is the variation of the etching amount, and a is the misalignment of the mask. As described above, a mask dimension designing method characterized by selecting W. 2. The method according to claim 1, wherein said metal wiring is an Al wiring. 3. The method according to claim 1, wherein the surface light emitting device is a diode or a thyristor.