JPS61168966A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device having a PHS (plated heat sink) structure with reduced variation of heat resistance in a desirable yield, by forming a second semiconductor layer on a semiconductor substrate and etching the substrate from the bottom face thereof up to the second semiconductor layer. CONSTITUTION:An AlGaAs layer 2, a GaAs buffer layer 3 for forming a GaAs MESFET, and a GaAs active layer 4 are epitaxially deposited on a semi- insulating GaAs substrate 1. The substrate is further provided with an Al Schottky electrode 7, AuGe-Ni source electrode 5 and an AuGe-Ni drain electrode 6. The GaAs substrate 1 is etched from the bottom face thereof with a liquid mixture of ammonia and hydrogen peroxide. Since Al0.4Ga0.6As is hardly etched, the etching effect can be stopped at the layer 2. Therefore, the thickness (t) of the substrate can be controlled as required, by means of appropriately selecting the thicknesses of the Al0.4Ga0.6 layer 2 and the GaAs buffer layer 3. Ti and Au films 8 and 9 are further deposited and an Au plated layer 10 is provided. Thus, a PHS structure can be obtained.

Description

Detailed Description of the Invention C. Field of Commercial Application] The present invention relates to a method for manufacturing a semiconductor device. Plated He
The present invention relates to a method of manufacturing a 8ink) structure.

[Conventional technology]

Due to the characteristics of the device, it is necessary to efficiently dissipate the heat generated from the element in four of the compounds with high M resistance. In cases where the elements are highly integrated and the heat source is concentrated, such as in a cost-compensating circuit device, and when the amount of heat generated is large, such as in the case of a discreet quadrant sister, there is a problem of heat dissipation. &,
The structure is called PH8 fabrication because the temperature is 3°C at Z-shaped.The GaAs substrate with large 1iPI resistance is made as thin as possible, and metal such as Au, Ag, Cu, etc. is made on the substrate with a thickness of several 10 μm to 100 μm. Attempts have been made to construct a structure in which heat is dissipated through this metal by thickly plating it.

The conventional method for forming the PH8 structure was generally as follows.

Okay, the surface [The entire surface of the semiconductor substrate on which the element is formed is polished to a thickness of 100 μm. Next, the surface of the base is etched to a thickness of 10 to 30 μm.
Finish to m. Metal on the 41k side of the board, e.g. 9
Agt - Thick plating to a thickness of 30 to 100 μm.

[Problems determined by the invention = 9] In the above-mentioned conventional method of forming PHS barrels, there is a large variation in the thickness of the substrate that occurs when the substrate is made thinner. The fear of reproducibility has become a serious problem. To give a specific example, when a 400 μm GaAs substrate is polished from the back side to a thickness of 100 μm, a thickness variation of approximately ±10 μm occurs within the surface of the 2"φ diameter substrate. Next, a mixed slag of sulfuric acid and hydrogen peroxide is used to polish the substrate. When the back side of the substrate is etched to a finished thickness of 20 μm, the variation in thickness due to etching is ±4 μm. ±1 for thickness variation
It has a thickness of 4 μm and has the same roughness as the finished O thickness of the substrate. As shown in the upper row, in the past, it was difficult to obtain an LT element with uniform resistance even on the same substrate surface due to the fear of mounting during the PH84S manufacturing process.

It is an object of the present invention to solve the above-mentioned problems and provide a method for producing a uniform thin semiconductor substrate having a P)is structure ζ with a high yield. .

[+ steps to eliminate problem points tS]

The structure of the 424-body device of the present invention is such that a semiconductor substrate having a semiconductor element T-plate surface is made into a thin film from the surface, and heat generated from the front 6D semicircular body is transferred to a friend metal provided on one surface of the semiconductor substrate. In the back manufacturing of a conductor g device with a structure that emits an efficient process to a thick film, at least INIT is applied to a semiconductor substrate.
(1) A step of forming a 2/1 or more semiconductor epitaxial layer containing a second semiconductor different from the semiconductor substrate, and an etching ratio between the second semiconductor layer and the semiconductor substrate. A large etching method 1c is comprised of a step of etching the 24 halves of the substrate from one side until the second semiconductor layer is reached.

[Effect]

In the present invention, a second conductor material layer is epitaxially formed on a semiconductor substrate by a predetermined etching method to form a second conductive material layer that can have a large etching ratio, and a third layer is formed on the second conductive material layer to form a device. Semiconductor material @t is grown epitaxially. When a PH8 structure is formed using this substrate r, it is possible to stop the etching of the substrate semiconductor at the second half-wood material layer described above, and eliminate the variation in thickness that occurs during back side polishing and back side etching of the substrate. I can do it.

Furthermore, by changing the thickness of the epitaxial layer of the second semiconductor material, it is possible to precisely determine the thickness of the finished substrate, and the thickness of the epitaxial layer is extremely controllable. It is possible to control the variation within the plane of the substrate to less than 5 cm.

[Implementation row]

Hereinafter, embodiments of the present invention will be congratulated with reference to the drawings.

FIGS. 1(a) to 1(e) are cross-sectional views of different types of work to explain one embodiment of the present invention. In this example, A J x G a □-x
A s f epitaxial growth is performed, followed by epitaxial growth of a single GaAa buffer layer and a Ga As active layer, and using this substrate, a high power GaAs MES F'ET (GaAs 1vlet
l Sem1 conductor field eff
ect transistor) t-If it is sent once, it will be removed.

First, as shown in Figure 1 (ta), semi-insulating G a A
GcaMUcVD (Metal (J
rgamicChemical Vapor Dep
position) AI using Den 2. , 4Gao, 6A
s #i2'f: 1 μm Extreme epitaxial growth. In order to increase the etching selectivity between GaAs and AlxGa1-xAs in the subsequent process, it is desirable that the VCAICD composition ratio be O13 or more, and in this example, the Al composition ratio was set to 0. .4. Next, a GaAs buffer y-M3 and a GaAs active pressure layer 4t are successively formed to form a GaAs seed bFET.
-Grow epitaxially.

UaAs(B5Lll:m4iX(i'J Takashi Takashi a
A s ME S F E Tt) and in some cases, s
ik impurity cut, impurity, cliff fj7 (n is n2lXl0
Cm 4 degrees and thickness 0.3 μm @ degrees. Ga
As buffer! So 3ζ high resistance M, I So and Mk facetch 7
In this case, the film is deposited to a thickness of 9 .mu.m when the finished film thickness t is approximately 10 .mu.m.

First, in the device shown in Figure 41(b), one Al Schottky pole 7. is placed on the surface of the above substrate. AuGe5N1;/-x1 5 and A u c) e #N Bdo L/ (nt+M
6 k-'f Niretsure is formed by the well-known vacuum evaporation and lift-off method.

To make the input VC1 substrate thinner, first, the 0 section 3 bases 1 (1) - surface was molded using an alumina abrasive with a grain size of 1200 to a thickness of about 100 μm.

After polishing was completed, a glass substrate was attached to the bottom surface of the semiconductor substrate using electron wax, and a mixture of annealing and hydrogen peroxide was applied to remove the swelling of the four substrates and the device on the narrow side of the substrate. Etch the GaAs substrate from both sides using a liquid.

Hard etching [- AIo, 4086.6AB
Since a is a fake that has not been etched, as shown in Figure 1 (C), A 1! 0.4 Gao, 6A S layer 2
The only thing that can be done is to stop the etching. At this time,
The basic thickness can be varied freely with the thickness of the 6A8512 and GaAs buffer layer 3.

After etching, Au becomes a heat mink on the substrate.
Plating/II 10"C 501tm radiance formed.

Before the continuous Au plating, a thin T film of about 500 A, a thin Au film 9't of about 1000 A, and a thin Au film 9't of about 1000 A are continuously sputtered. These 11ids and Au film 9a
This is to facilitate the T-screen plating of Au.

Finally, the glass plate attached to the surface of the substrate is peeled off in a heated trichlortyrene, resulting in the PH8 structure shown in FIG. 1(d).

FIG. 2 is a cross-sectional view of a semiconductor device which has been fully implemented in accordance with the present invention. +: A If o, 4 Ga o, s used as a stop layer for etching during the actual feeding.
A a layer 2'i GaAs substrate 1t etched and removed using hydrogen fluoride filling. 11 A high-output GaAs MESFET having a PH8 structure with little variation in heat resistance, that is, with little variation in thermal resistance, can be manufactured with high yield.

I used a discrete element as an example, but -41
: It is clear that the invention can be applied to a fruit circuit as well.

〔Effect of the invention〕

As explained above, 4+: If the invention is applied, a uniform wide semiconductor substrate can be easily produced, and a semiconductor device having a PH8 structure can be manufactured in a neat manner.

[Brief explanation of drawings]

Figures 1+a+ to (dl) are shown in order of process for explaining an embodiment of the present invention. Figures fc sectional m1 and 4IJ2 are cross-sectional views of a semiconductor device IT formed with an edge in another embodiment of the present invention. Yes. ■...GaAS substrate, 2-- AI! □, 4
Ga 0.6AS layer, 3...GaAs buffer layer, 4...GaAs active layer, 5...source electrode, 6...drain electrode, 7...・Schottky electrode, 8・river・Ill, membrane, 9・river・・
Au film, 10... Au plating layer. -2-9, - Agent Patent Attorney Uchihara f1゛＼雫－曽□－ Part I /I! t $ 2 times

Claims (1)

[Claims] In a method for manufacturing a semiconductor device having a structure in which a semiconductor substrate having a semiconductor element on the front surface is thinned from the back surface and heat generated from the semiconductor element is efficiently released to a thick metal film provided on the back surface of the semiconductor substrate, the semiconductor substrate forming two or more semiconductor epitaxial layers including at least one second semiconductor layer different from the semiconductor substrate thereon;
a step of etching away the semiconductor substrate from the back surface until reaching the second semiconductor layer using an etching method with a high etching ratio between the second semiconductor layer and the semiconductor substrate. manufacturing method.