JPH02307219A - Manufacture of electrode of semiconductor element - Google Patents

Abstract

PURPOSE:To form a viahole of a smaller size than that of a conventional one and to form an electrode of a viahole structure even if a thick substrate is used by providing a metal mask by an oblique depositing method on the way of etching, and then additionally etching it to passing a hole, etc. CONSTITUTION:When an electrode 5 of a viahole structure to be directly conducted with an element electrode 3 formed on the surface of a semiconductor substrate 1 is formed in a viahole formed from the rear face side of the substrate 1, with photoresist 2 formed on the rear face of the substrate 1 as a mask it is etched from the rear face to the vicinity of the front face to form a first viahole, and a metal mask layer 6 is formed in the first viahole and the periphery by oblique depositing. Then, the exposed part of the substrate formed with the shade of the oblique depositing is etched with the layer 6 as a mask, and a second viahole 7 reaching the electrode 3 through the substrate 1 is formed. Thereafter, an electrode material 4 is rotatably deposited to bury the first and second viaholes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing an electrode for a semiconductor device, and particularly to a method of manufacturing an electrode of a semiconductor device adopting a via-hole structure, such as a compound semiconductor device. It is.

[Conventional technology] Conventionally, gallium arsenide (hereinafter abbreviated as GaAs) has been used.
For example, GaAs M old C (MM
is an abbreviation for monolithic microwave) and power Ga.
In a semiconductor device such as As PET, which has a large chip and a complex structure, a via-hole structure is adopted as an effective means for reducing inductance in the source electrode, which provides direct conduction from the back surface of the device.

Hereinafter, as an example of a method for forming a via hole structure in GaAs PET, wet etching and A
A method of manufacturing an electrode with a via hole structure using the u-plating technique will be explained. Note that illustration of the details of the main body of GaAs PET is omitted.

FIG. 2 is a manufacturing flow diagram showing a conventional method for forming an electrode with a via hole structure in the order of steps using schematic cross-sectional views of main parts.

In Figure 2 (a), the thickness C is 1001J1! A photoresist 2 is applied to the back surface of a GaAsM plate 1, which is referred to as 1, by a photolithography (hereinafter abbreviated as photolithography) process.
A 100 μm x 100 gm opening 2a with one side D is patterned at the same position as the source electrode 3 formed on the front side of the GaAs substrate 1.

In FIG. 2(b), a via hole is formed by etching the GaAS substrate 1 from the back side to the surface of the source electrode 3 using a phosphoric acid-based etchant.

The length E of the opening on the back side of the via hole etched at this time is approximately 200 mm, and the length F on the front side is 170~19 mm.
The edge taber (θ) of this hole is approximately 75″, with the back side slightly open.

In FIG. 2C, the photoresist 2 is removed using an organic solvent.

In FIG. 2(d), Au-based vacuum evaporation is performed on the entire surface of the GaAs substrate 1 and the source electrode 3 by a rotary evaporation method to form a current film 4. According to the above-mentioned rotary evaporation method, the metal vapor enters the via hole from multiple angles, so that the current film 4 is formed without any gaps.

In FIG. 2(e), a U plating layer 5 with a thickness of about 501 m is formed on the current film 4 by electrolytic plating, and the formation of the via hole structure electrode is completed.

[Problems to be Solved by the Invention] In the conventional method for manufacturing electrodes of semiconductor devices as described above,
In particular, the following problems have occurred in the formation of via holes.

(b) Since etching is performed using a wet etchant, an isotropically etched shape is likely to occur, and a hole shape that is larger than a predetermined size is likely to occur.

Because of the phenomena (b) and (a), it is necessary to make the GaAs substrate extremely thin in order to form small-sized holes. For example, if the target size is 5 (II Jm x 50 μm), the thickness of the GaAs substrate needs to be about 501 Jm or less.

(c) In addition, small mask patterns (for example, 501
When trying to etch using m x 50-),
Etching is likely to stop midway through the etching process, making it impossible to form a through hole that reaches the source electrode.

To summarize the above (a), (b), and (c), in the case of the current process using a wet etchant, small holes cannot be formed unless the GaAs substrate is extremely thin. On the other hand, the size of the via hole is desired to be as small as possible due to pattern constraints.

This invention was made in order to solve the above problem, and even when using a substrate as thick as that used as a normal element substrate, it is possible to form via holes smaller than conventional ones and use electrodes with a via hole structure. It is an object of the present invention to provide a manufacturing method that can form.

[Means for Solving the Problems] A method for manufacturing an electrode for a semiconductor device according to the present invention includes forming a via hole using a conventional wet etchant;
In the process of filling this via hole with metal to form an electrode with a via hole structure, first, the etching to form the first via hole is stopped midway through, and then a metal mask is formed by an oblique evaporation method. After forming a very small second via hole by additionally etching the micro-sized exposed portion of the substrate that was not deposited due to the shadow of the oblique evaporation of the mask and creating a through hole, an isotropic layer was formed by rotary evaporation. By performing vapor deposition, an electrode with a via hole structure is formed.

[Function] In this invention, the etching of the relatively large via hole that is first formed is stopped before the substrate is penetrated, and then a metal mask is formed by oblique vapor deposition, thereby eliminating the shadow of the oblique vapor deposition caused by the side wall of the via hole. The small area at the bottom of the via hole where the metal mask was not formed is etched again using the metal mask as a mask to form a through hole, so a very small via hole is formed when viewed from the source electrode side. Therefore, in terms of size, it is sufficient to form a source electrode with a small area corresponding to the small via hole in the substrate penetrating portion.

[Example: (a) to (d2) in Figure 1A and (e) to (e) in Figure 1B
(h) is a manufacturing flow diagram with schematic cross-sectional views of main parts showing one embodiment of the method for manufacturing a via hole electrode of a semiconductor device according to the present invention in the order of steps. Note that (d2) in FIG. 1A is a partially enlarged view illustrating a method of calculating the dimensions of the via hole opening in FIG. 1A (d).

Further, the reference numerals 1 to 5 are the same as the same or corresponding parts used in the explanation of the conventional example shown in FIGS. 2(a) to 2(e).

Hereinafter, the forming method and its state will be explained with reference to the process steps shown in FIGS. 1A (a) to 1B (h).

In (a) of FIG. 1A, GaA with a thickness C of 100-
A photoresist 2 formed on the back surface of the s-substrate 1 by a photolithography process is coated with 1ooolJff+×100 μm, with the length of one side being D, near the position of the source electrode 3 formed on the surface of the substrate.
The opening 2a is buttered.

In (b) of FIG. 1A, using a phosphoric acid-based etchant, the opening 2a is etched by 90 μm from the back surface of the GaAs substrate 1.
Etch to a depth G of m. Since the thickness of the GaAs substrate 1 at this time is 100 .mu.m (C), etching of 90 .mu.m leaves an etching residue of 1O-(H).

In FIG. ffllA (e), when the photoresist 2 is removed using an organic solvent, an etching hole for a relatively large first via hole is formed in the GaAs substrate 1 before it is penetrated.

In (d) of FIG. 1A, 8g of GaAs substrate is etched in the first etching hole by vacuum evaporation.
An Ω mask 6 is formed by performing oblique vapor deposition.

As shown in (d2) of Fig. 1A, 30° to the substrate surface.
From the diagonal direction of °, Af! When evaporated metal is incident, a portion from the edge of the etched hole on the back surface of the GaAs substrate 1 to a portion A is not deposited because it is shadowed by the side wall on one side of the hole. In addition, in the actual shadow, if the taper on the source electrode side is about θ-75'', the opening at the bottom of the hole where no evaporation is performed will be the part A minus the part B. For example, if the etching depth is 90-1 If the deposition angle is 30°, A=stn30°X 90I
Jm -45gm, B-sin15°×9O--23
- (this is always constant), therefore, A - B = 4
An AJII mask opening 7a of 5 23-22 gm is formed.

In FIG. 1B (e), the GaAs substrate 1 at the heg mask opening 6a formed in the AN mask 6 is additionally etched using a phosphoric acid-based wet etchant.

That is, the remaining GaA in the portion of the Ω mask opening 6a
s is etched through and the via hole opening (second
A via hole (7) is formed to reach the source electrode 3.

In FIG. 1B (f), the Ω mask 6 is removed using an etchant of 1.

In FIG. 1B (g), an Au-based current film 4 is formed on the entire surface of the GaAs substrate 1 and the source electrode 3 by vacuum deposition. At this time, a rotary evaporation method is used as the evaporation means, so that the metal vapor enters from multiple angles without any gaps.

In (h) of FIG. 1B, an Au plating layer 5 is formed on the current film 4 to a thickness of about 501 Jm using an electrolytic plating method, and the Au plating layer 5, the current film 4, and the via hole opening 7 are formed. The formation of the via hole structure electrode is completed.

Note that the numerical values used in the above description are merely examples, and the present invention is not limited thereto.

In addition, in the above embodiment, a method for forming an electrode with a via hole structure in a semiconductor device using a GaAs substrate was described, but the manufacturing method of the present invention can be applied to other compound semiconductors, elemental semiconductors, etc. that require via holes. It can be easily applied to semiconductors.

[Effects of the Invention] As explained above, according to the via hole manufacturing method of the present invention, a metal mask is provided by an oblique evaporation method during etching, and then additional etching is performed to penetrate the hole. A small second via hole can be formed by wet etching, which has been difficult in the past. Therefore, a method for forming electrodes of a microstructured semiconductor device having a via hole structure has been established.

Further, there is an effect that the size of the via hole opening can be selected simply by changing the evaporation angle regardless of the thickness of the substrate of the semiconductor element.

Further, the present invention has high industrial value, since it becomes easy to reduce the size of the via hole in a semiconductor device that requires a via hole structure, thereby reducing the size of the device structure.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1A and 1B are manufacturing flow diagrams with cross-sectional views of essential parts showing one embodiment of the method for manufacturing a higher hole structure electrode of a semiconductor device according to the present invention, and FIG. FIG. 2 is a manufacturing flow diagram showing a conventional method for forming an electrode with a via hole structure in the order of steps. In the figure, 1 is a GaAs substrate, 2 is a photoresist, 2
a is an opening, 3 is a source electrode, 4 is a current film,
5 is an Au plating layer, 6 is an Aρ mask, 6a is an AΩ mask opening, and 7 is a via hole opening. In this 415th month, the form of the death of Yoyorobai N Tsume Ruoffhezu=- A Flow Figure 1B Procedural Amendment (Voluntary)

Claims (1)

[Scope of Claims] A method for manufacturing an electrode of a semiconductor device, comprising forming an electrode with a via hole structure in a via hole formed from the back side of the semiconductor substrate to have direct conduction with the device electrode formed on the surface of the semiconductor substrate. A first via hole is formed by etching from the back surface to the vicinity of the surface using a photomask formed on the back surface of the semiconductor substrate as a mask, and a metal mask layer is formed in and around the first via hole by oblique vapor deposition. and etching the exposed portion of the semiconductor substrate in the first via hole formed by the shadow portion of the oblique vapor deposition using the metal mask layer as a mask to penetrate the semiconductor substrate and form the device electrode. 1. A method of manufacturing an electrode for a semiconductor device, characterized in that after forming a second via hole that extends, the first and second via holes are filled by rotary evaporation of an electrode material.