JPH01165153A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To decrease mandays for thinning a semiconductor section by selectively etching an operating layer region in a semiconductor wafer polished up to specified thickness in fixed depth from the rear and forming a heat sink by filling an etched section with a plating metallic layer. CONSTITUTION:An ohmic electrode 2 is shaped on the surface side of an epitaxial wafer 1, and the wafer 1 is polished in thickness of 80mum from the rear side. An silicon oxide film 3 and the pattern 4 of a photo-resist are formed onto the whole surface of the rear side, and an exposed region in a semiconductor is etched in depth of 50mum. An ohmic metallic film 5 is shaped onto the rear, the photo-resist 4 is dissolved by an organic solvent and the metallic film 5 on surfaces except an etching surface is removed, and the metallic film 5 on the etching surface is brought to an ohmic state through heat treatment. The surface side is coated with an insulating film, and an etching section is filled with a plating Au layer 6. The insulating film on the surface side is gotten rid of, the etching of a semiconductor section is conducted to the surface side, the semiconductor section is isolated, and a semiconductor layer is cut at specified positions, thus isolating an element.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a plated heat sink (hereinafter referred to as PH
The present invention relates to a method for manufacturing a semiconductor device having a structure (denoted as 8).

[Conventional technology]

In power devices such as Gunn diodes, Innoset diodes, and high-output field effect transistors, PH8 is used to improve heat dissipation by making the semiconductor part thinner and forming a heat sink with a plated metal layer on one side.
structure is adopted.

FIG. 2 shows an example of a method for manufacturing a conventional Gunn diode having a PH8 structure.

Approximately 350 μm thick Ga with (100) plane orientation
An impurity concentration of 7 x 10" crr is formed on the surface (lower side in the figure) of the AsN type single crystal substrate by epitaxial growth.
T 3, 5 μm thick buffer layer, impurity concentration lXl0
cm, 10 μm thick active layer, impurity concentration lX
An ohmic metal film 5a such as AuGeNi is formed on the surface of the epitaxial wafer 1 [Fig.
By electrolytic plating, Au with good thermal conductivity is deposited on the metal film 5a.
A plating metal layer 6a such as [
Figure (b)] The part of the epitaxial wafer l that is directly necessary for the operation of the Gunn diode is the epitaxial layer, and the substrate layer part is necessary for handling the sea urchin, but it has poor heat conduction and dissipates heat. Most of the substrate layers are removed using the method described below.

The plated metal layer 6a side is attached to a polishing weight, and the semiconductor layer is uniformly coated on the entire surface from the back side (substrate layer side) by a polishing method.
Polish until the thickness is 0 μm [Figure (C)].

Next, an ohmic electrode 2 with a diameter of 100 μm is placed on the polishing side surface.
A is formed [Figure (d)], and the semiconductor layer portion is etched using this electrode 2a as a mask to separate the semiconductor layer portion [Figure (e)], and the plated metal layer 6a is cut to separate the elements. [Figure (f)].

[Problem that the invention seeks to solve]

In the conventional manufacturing method, as described above, after forming the plating metal layer of the heat sink on the front side of the semiconductor wafer where the active layer is formed, mechanical polishing is performed from the back side.
Most of the substrate layer was removed to make the semiconductor part thinner for better heat dissipation, but mechanically polishing the layer to a uniform thickness of 30 μm was time consuming and time consuming. , which was technically difficult and had low yields, contributing to high costs.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for thinning a semiconductor portion without requiring an additional number of layers and achieving a high yield.

[Means for solving problems]

The manufacturing method of the present invention thins the semiconductor portion by etching with high processing precision, and selectively etches the active layer region of a semiconductor wafer polished to a predetermined thickness to a predetermined depth from the back surface. In this method, a heat sink is formed by filling the etched portion with a plating metal layer.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the invention.

An ohmic electrode 2 is formed on the surface side of the epitaxial wafer S1 on which an epitaxial layer is grown, similar to that shown in FIG. 2' [FIG. 2(a)].

Next, the front side of the wafer 1 is attached to a polishing weight, and the semiconductor layer is polished from the back side (from the bottom in the figure) until the semiconductor layer has a uniform thickness of 80 μm over the entire surface [Figure (b) )
].

Next, a silicon oxide film 3 is formed on the entire back surface by a spunter method or the like, and a photoresist groove turn 4 is formed on the silicon oxide film 3 [FIG. (C)].

The silicon oxide film 3 is etched using the photorenost 4 as a mask [Figure (d)], and the exposed area of the semiconductor is etched to a depth of 50 μm with an etching solution of sulfuric acid-hydrogen peroxide:water = 1-8:1. [Figure (e)]
.

Next, an ohmic metal film 5 is formed on the back surface by vacuum evaporation, the photoresist 4 is dissolved in an organic solvent to remove the metal film 5 on the surface other than the etched surface, and the metal film 5 on the etched surface is removed by heat treatment. Perform ohmic conversion [Figure (f)
].

Next, the front side is covered with an insulating film, and the back side is plated with Au using an electrolytic plating method.
Fill with layer 6 [Figure (g)].

At this time, the sticking layer 6 protruding from the back surface is removed by a polishing method using the back surface as a reference.

Next, the insulating film on the front side is removed, and the semiconductor portion is etched on the front side using the ohmic electrode 2 as a mask.
The semiconductor portion is separated and the semiconductor layer is cut at predetermined locations using a diamond scribe method or the like to separate the elements [Figure (h)].

As described above, according to the present invention, since the semiconductor portion is thinned by etching, the number of man-hours is reduced, it is technically easy, and the yield is improved.

Furthermore, since the plated Au layer is formed only in the necessary areas, the amount of Au material can be saved.

Although the present invention has been described above using the method of manufacturing a Gunn diode as an example, it is of course applicable to manufacturing other semiconductor devices having a PH8 structure.

〔Effect of the invention〕

As explained above, according to the present invention, the thickness of the semiconductor part can be easily reduced, the number of man-hours is reduced and the yield is improved compared to the conventional method, and the M material can be reduced, resulting in cost. It has a similar effect to down.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of a conventional method for manufacturing a Gunn diode having a PH8 structure. DESCRIPTION OF SYMBOLS 1... Epitaxial wafer, 2... Ohmic electrode, 3... Silicon oxide film, 4... Photoresist,
5... Ohmic metal film, 6... Plated Au layer The same reference numerals in the drawings indicate the same or equivalent parts. Patent applicant New Japan Radio Co., Ltd. Figure 1

Claims (1)

[Claims] In a method for manufacturing a semiconductor device with a plated heat sink structure in which a heat sink (heat dissipation electrode) is formed by a plated metal layer on one side of an active layer region, after a semiconductor wafer is mechanically polished to a predetermined thickness. A semiconductor device comprising the steps of selectively etching an active layer region from the back surface to a predetermined depth, and filling the portion etched in the step with a plated metal layer to form a heat sink. manufacturing method.