JPH0513780A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device having electronic elements for large power that can be produced by preventing any decrease in yield by the process for making a thin semiconductor substrate for heat radiation. CONSTITUTION:A metal thick films 2 and 4 are selectively formed on a base substrate 1 such as clear quartz substrate which has a mechanical strength and smooth surface. Then, a semiconductor substrate 5 is placed on the metal film 4, and both of them are bonded under pressure or heat. Then, the top surface of the semiconductor substrate 5 is polished mechanically or chemically and the substrate is made thinner. Thereafter, by using the conventional electronic element forming method for semiconductor substrate 5, and an electron element is formed on the thinned semiconductor substrate 5 or on the epitaxial growth made on the semiconductor layers 6 and 7 on the semiconductor substrate 5. Finally, only the clear, smooth-surfaced substrate 1 used as the base is selectively removed by etching. By doing this, the process of forming a metal film on the rear surface of the semiconductor substrate can be performed while the substrate is in thick state, and a higher mechanical strength can be ensured by the substrate used as base in the electron element formation process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a semiconductor element for high power.

[0002]

2. Description of the Related Art In a semiconductor device handling a large amount of power, in order to prevent deterioration of the device performance due to heat generation during operation of the device itself, the semiconductor device in which the device is built in is completed after the diffusion process in which the electronic device is built in the semiconductor substrate. The upper surface of the substrate and the quartz substrate are bonded together, and the semiconductor substrate is made mechanically or chemically polished from the rear surface side of the semiconductor substrate exposed on the front surface to reduce the thickness of the semiconductor substrate, or on which the metal film is further formed. After that, it is necessary to improve the heat dissipation of the semiconductor element by performing a step of separating the semiconductor substrate from the quartz substrate or the like which is the base.

[0003]

However, in the above-mentioned conventional structure, when the thickness of the semiconductor substrate formed in the element is reduced, the mechanical strength of the semiconductor substrate is lowered, and the subsequent metal film forming step, In the process of separating the semiconductor substrate and the base substrate, there is a high possibility that the entire semiconductor substrate or the elements will be destroyed, which has been a cause of lowering the yield of the semiconductor elements.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor device having a large power semiconductor element that generates a large amount of heat without lowering the yield.

[0005]

In order to achieve the above object, in the method of manufacturing a semiconductor device of the present invention, first, a substrate having mechanical strength, such as a quartz substrate, which is transparent and has a smooth surface is selectively formed. A metal film is formed on the metal film, a semiconductor substrate is then placed on the selectively formed metal film, and the metal film and the semiconductor substrate are pressure bonded or pressure bonded while heating. Then, the upper surface of the pressure-bonded semiconductor substrate is mechanically or chemically polished to thin the semiconductor substrate. Thereafter, by using a conventional method for forming an electronic element on a semiconductor substrate, an electronic element is formed on a semiconductor substrate which is pressure-bonded to a metal film and thinned, or a semiconductor layer is epitaxially grown on this semiconductor substrate. After that, only the transparent substrate with a smooth surface, which was the base,
Selectively removed by chemical etching.

[0006]

With the above structure, the step of forming the metal film on the back surface of the semiconductor substrate can be performed in a state in which the thickness of the semiconductor substrate is thick. The mechanical strength can be secured. In addition, since the semiconductor substrate and the base substrate are separated by selective chemical etching of the base substrate, the semiconductor substrate is not subjected to mechanical stress as in the past in this process, and the entire substrate and elements are prevented from being destroyed. Will be easier.

[0007]

1 is a process diagram showing a method of manufacturing a semiconductor device according to an embodiment of the present invention, which is a process diagram for forming a GaAs FET having a thin semiconductor substrate and a metal film on the back surface of the device. First, as shown in FIG. 1A, an Au thin film 2 is vapor-deposited on one surface of a quartz substrate 1 having a smooth surface, and a photoresist film 3 is selectively formed thereon. By using this photoresist film 3 as a mask, as shown in FIG.
Au plating is selectively performed on the surface of the quartz substrate 1 on which Au is vapor-deposited to partially form the Au thick film 4. Next, as shown in FIG. 1C, the quartz substrate 1 on which the Au thick film 4 is partially formed
The semi-insulating GaAs substrate 5 is placed on the upper surface, and the Au thick film 4 and the semi-insulating GaAs substrate 5 are pressure bonded while heating the whole. Next, the semi-insulating GaAs substrate 5 is subjected to mechanical polishing and chemical polishing from the upper surface, so that 30 as shown in FIG.
Make the thickness of μm. Next, as shown in FIG.
On a semi-insulating GaAs substrate 5 having a thickness of μm, an AlGaAs layer 6 not intentionally containing impurities and an GaAs layer 7 intentionally containing impurities to be an active layer of an FET are sequentially epitaxially grown. . Next, as shown in FIG. 1F, a region including a part or the whole of the GaAs layer 7 above the portion where the Au thick film 4 is not formed is an AlGaAs layer which intentionally does not include at least impurities from above. 6
Selectively remove until halfway. Further, a source electrode 8, a drain electrode 9 and a gate electrode 10 are formed on the GaAs layer 7 which is selectively left with impurities intentionally included. After the step of forming the FET, as shown in FIG. 1G, only the quartz substrate 1 is selectively removed with an HF-based etching solution. Finally, the FETs are separated at the portion where the Au thick film 4 is not present, and as shown in FIG.
A GaAs FET is formed on a 30 μm thick semi-insulating GaAs substrate 5 having a u thick film 4.

In this embodiment, GaA is used as the electronic element.
Although the manufacturing of the sFET has been described, the electronic element is not limited to the FET, and may be a diode, a capacitor, or the like, or an integrated circuit combining these. The semiconductor substrate is Ga
Not limited to As, Si or another compound semiconductor may be used. In this example, the Au film was first formed on the quartz substrate, but it is transparent, has surface flatness and mechanical strength, and has heat resistance that can withstand heating in the process of forming a semiconductor epitaxial layer or an electronic element. The present invention is not limited to this as long as it has the above-mentioned property and can be selectively removed by chemical etching with respect to the semiconductor substrate. Further, in the present embodiment, the Au thick film 4 was formed on the quartz substrate 1 by the selective plating method, but the forming method is not limited to this, and the kind of metal is not limited to Au, and the semiconductor epitaxial layer after that is formed. It may be appropriately selected so that there is no inconvenience in the process of forming the electronic element. Further, in this embodiment, after the semi-insulating GaAs substrate 5 is set to 30 μm, the undoped AlGaAs layer 6 and the doped GaAs layer 7 as the active layer of the FET are sequentially epitaxially grown in order to improve the electrical isolation between the electronic elements. However, the thickness of the semiconductor substrate is not limited to this, and the undoped layer is not limited to AlGaAs, and may be GaAs, InGaAs or the like, or may be omitted. The method for forming the active layer is not limited to the epitaxial growth method,
The injection method may be used.

In this embodiment, the AlGaAs layer 6 and Ga are
Although the electronic device is formed by epitaxially growing the As layer 7, the electronic device can be directly formed on the GaAs substrate 5.

[0010]

As described above, according to the present invention, first, a metal film is selectively formed on a transparent substrate having a smooth surface, and a semiconductor substrate is placed on the selectively formed metal film. The metal film and the semiconductor substrate are pressure bonded or thermocompression bonded. Next, the upper surface of the semiconductor substrate pressed to the metal film is mechanically or chemically polished to thin the semiconductor substrate, and a semiconductor layer is epitaxially grown on the thinned semiconductor substrate or further on this semiconductor substrate. Form an electronic device. Finally, by selectively chemically etching and removing only the transparent and smooth surfaced substrate on which a metal film is formed, it is possible to manufacture without lowering the yield and to radiate heat through the thick metal film on the back surface of the semiconductor substrate It is possible to provide a semiconductor device having.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

[Explanation of symbols]

1 Quartz substrate 2 Au thin film 3 photoresist film 4 Au thick film 5 Semi-insulating GaAs substrate (semiconductor substrate) 6 Undoped AlGaAs layer 7 Doped GaAs layer 8 Source electrode 9 Drain electrode 10 Gate electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihisa Sugimura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electronics             Industry Co., Ltd.

Claims (2)

[Claims] 1. A step of selectively forming a metal film on a transparent substrate having a smooth surface, and a semiconductor substrate provided on the selectively formed metal film, and the semiconductor substrate and the metal film. Is performed by pressure bonding or thermocompression bonding, a step of polishing the upper surface of the semiconductor substrate pressure-bonded with the metal film to thin the semiconductor substrate, and a step of pressure-bonding the metal film with the thinned semiconductor substrate surface A method of manufacturing a semiconductor device, comprising at least a step of forming and a step of selectively removing only the transparent substrate having a smooth surface on which a metal film is selectively formed by selective chemical etching. 2. A semiconductor thin film layer is epitaxially grown on a semiconductor substrate which is pressure-bonded with a metal film and thinned, instead of the step of forming an electronic element on the surface of the semiconductor substrate pressure-bonded with the metal film and thinned, and the epitaxially grown semiconductor 2. The method for manufacturing a semiconductor device according to claim 1, wherein the step is a step of forming an electronic element on the thin film layer.