JPH07193122A - Production of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the formation of an affected hardening layer that is caused by an etching gas that enters the inside of bubble generating inside the adhesive material combining a glass plate and a GaAs substrate, and is difficult to be removed from the surface of the adhesive material, and to improve its appearance yield. CONSTITUTION:When an element part is to be formed, a gate electrode 3 is formed and at the same time a laminated metallic film 6 made of the same structure is also formed in an element separation area 13, which is used as a film to stop etching a GaAs substrate 1 from its rear face by a chlorine-based gas using a PHS 12 as a mask. Thus, an affected hardening layer that is caused by the entrance of chlorine gas into an adhesive material 7 can be prevented even when a bubble 9, etc., are formed inside the material 7.

Description

Detailed Description of the Invention

[0001]

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

[0002]

BACKGROUND ART FIG. 4 is cross-sectional view of one example of prior art of GaAsFET PHS (P lated H eat S ink) structure, Figure 5
Is a plan view. In the figure, 1 is a GaAs substrate on which a field effect transistor (FET) is formed, 2 is an insulating film, 3 is a gate electrode made of gold / platinum / titanium / (Au / Pt / Ti), and 4 is the GaAs substrate 1 Gold / platinum / titanium / nickel / gold-germanium (A
u / Pt / Ti / Ni / Au.Ge) source electrode, 5 is a drain electrode formed at the same time as the source electrode, 8 is a glass plate serving as a reinforcing plate, 7 is the GaAs substrate 1 on the glass plate 8. A sticking material for sticking, 10 is a via hole, and 12 is gold-plated P
HS, 11 is a conductive film for electroplating the PHS 12, and 13 is a conductive film 11 using the PHS 12 as a mask.
And 9 are element isolation regions formed by etching the GaAs substrate 1, and 9 are bubbles or gaps generated in the bonding material 7 between the glass plate 8 and the GaAs substrate 1.

[0003]

In the structure shown in FIGS. 4 and 5 according to the prior art, the element isolation region 13 is formed by etching the conductive film 11 by ion milling using the PHS 12 as a mask, and thereafter To PHS12
The GaAs substrate 1 is etched by the dry etching technique using the as a mask, but in this case, there are the following problems.
Although a GaAs substrate having a thickness of about 500 μm is used, it is effective to reduce the thickness of the GaAs substrate to about 20 to 150 μm in order to quickly release the heat generated in the GaAs substrate. A PHS structure is formed by a conventional technique after polishing and etching from the back surface in a state where the front side with the FET formed is attached to a transparent plate such as a glass plate to reduce the thickness to a desired thickness. After that, the GaAs substrate is etched by the dry etching technique using PHS or the photoresist as a mask to separate the elements.

In this case, however, a gap is formed between the glass plate and the GaAs substrate adhered by the adhesive material due to the coating film thickness at the time of applying the adhesive material, the attachment method and the thermal history or stress in the processing process. Or there is a problem that bubbles are generated. The surface of the adhesive material exposed after etching the GaAs substrate for element isolation is alteration hardened by the etching gas, and this alteration hardened layer can be removed by ashing with oxygen (O ₂ ) plasma. However, when the etching gas enters the above-mentioned gaps or bubbles and the surface of the bonding material in a wide range is modified and hardened, it is difficult to remove the modified hardened layer by ashing with O ₂ plasma, and it is difficult to remove the GaAs after element isolation. When the substrate is peeled off from the glass plate by the conventional method, the deteriorated hardened layer that cannot be completely removed adheres to the FET formed on the GaAs substrate, impairs the appearance, and deteriorates the manufacturing yield. In order to prevent the deterioration of the appearance yield, it is necessary not to form a wide range of hardened deterioration layer that cannot be removed. An object of the present invention is to provide a method of manufacturing a semiconductor device which solves the above-mentioned conventional problems and does not form a deteriorated hardened layer that cannot be completely removed.

[0005]

According to the present invention, an element portion including a gate electrode, a source electrode and a drain electrode is formed on the surface of a semi-insulating compound semiconductor substrate, and the gate electrode, the source electrode or the drain electrode is formed. At the same time, a step of forming a laminated metal film having the same structure as all or part of it in the element isolation region of the substrate, and a step of attaching a reinforcing plate to the element formation surface of the substrate via an attaching material, Forming a conductive film for PHS (Plated Heat Sink) plating and a PHS having a predetermined pattern on the back surface of the substrate; etching the conductive film from the back surface of the substrate using the PHS as a mask; and masking the PHS. As a step of etching the element isolation region of the substrate from the back surface of the substrate as A method of manufacturing a semiconductor device, which comprises using as the film to stop the etching.

Further, according to the present invention, an element portion including a gate electrode, a source electrode and a drain electrode and an insulating film between the electrodes is formed on the surface of a semi-insulating compound semiconductor substrate, and the insulating film is formed. At the same time, a step of forming an insulating film in the element isolation region of the substrate, a step of attaching a reinforcing plate to the element formation surface of the substrate via an attaching material, and a PHS (Plated Heat Sink) plating on the back surface of the substrate. Forming a conductive film and a PHS having a predetermined pattern for etching, etching the conductive film from the back surface of the substrate using the PHS as a mask, and separating elements of the substrate from the back surface of the substrate using the PHS as a mask. And a step of etching a region, wherein the insulating film is used as a film for stopping etching during etching of the substrate. Is.

[0007]

In the present invention, first, the element portion including the gate electrode, the source electrode, the drain electrode and the active region is formed on the GaAs substrate by the conventional technique. Then, when forming the gate electrode or the source electrode / drain electrode, a laminated metal film of the same metal as the gate electrode or the source electrode / drain electrode is simultaneously formed in the element isolation region on the GaAs substrate. After the formation of the element portion on the GaAs substrate is completed, the surface of the GaAs substrate on which the element is formed is attached to the reinforcing plate with an attaching material, and Ga is formed by the conventional technique.
The back surface of the As substrate is polished and thinned to form via holes and PHS. The PHS is used as a mask to etch away the element isolation region of the GaAs substrate from the back surface by dry etching to expose the laminated metal film. Next, the exposed laminated metal film is etched by ion milling using the above-mentioned PHS as a mask to separate the above-mentioned GaAs substrate. Here, the laminated metal film prevents the adhesive gas from permeating and hardening when the dry etching of the element isolation region of the GaAs substrate is caused by the etching gas entering the gaps and bubbles generated inside the adhesive material. For this reason, since the deteriorated hardened layer of the adhesive material is formed only on the surface, it is easily removed by ashing with O ₂ plasma. An insulating film may be used instead of the laminated metal film. In this case,
By leaving an oxide film formed as an insulating film between the gate, source and drain electrodes of the element portion in the element isolation region by the conventional technique, it can be used as a film for stopping etching. The film for stopping the etching due to the oxide film can be removed by wet etching, and it is effective in preventing the deterioration hardening layer due to the dry etching on the surface of the bonding material.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a plan view of a semiconductor device obtained by the method of the present invention, and FIG. 2 is AA ′ in FIG.
It is sectional drawing by a line. In FIG. 1, a GaAs substrate 1
An element composed of a gate electrode 3, a source electrode 4 and a drain electrode 5 is formed on the top by a conventional technique. Also, in the element isolation region of each element, during dry etching of the element isolation region from the back surface of the GaAs substrate, it is possible to prevent the etching gas from entering the gaps or bubbles generated inside the adhesive material and causing the adhesive material to be deteriorated and hardened. The laminated metal film 6 is formed. As shown in FIG. 2, the surface of the GaAs substrate 1 on which the elements are formed (front surface) is fixed to a glass plate 8 which is a reinforcing plate by a bonding material 7. The air bubbles 9 are generated due to variations in the coating film thickness at the time of applying the adhesive material 7, thermal history or stress during the attaching method and processing process. Also G
On the back surface of the aAs substrate 1, a via hole 10 and a conductive film 1 are provided.
1, PHS12 is formed. The element isolation region 13 is formed by using the PHS 12 as a mask to remove the conductive film 11 and then using the laminated metal film 6 as a film for stopping etching.
The As substrate 1 is removed.

Next, a manufacturing process of the semiconductor device having the structure shown in FIGS. 1 and 2 will be described with reference to FIG. First, FIG.
As shown in (a), after forming an insulating film 2 on a GaAs substrate 1 in which an active layer region is formed by a conventional technique, titanium (Ti) thickness is 500 angstrom and platinum (Pt) thickness is formed by vapor deposition method. 1000 angstroms, the gate electrode 3 made of gold (Au) has a thickness of 2000 angstroms, the thickness of gold germanium is 1500 angstroms, the thickness of nickel is 500 angstroms, the thickness of titanium is 500 angstroms, and the thickness of platinum is 1000 angstroms.
An element portion composed of the source electrode 4 and the drain electrode 5 of angstrom and gold thickness of 2000 angstrom is formed. When forming the gate electrode 3 described above, the laminated metal film 6 having the same structure is formed in the element isolation region 13 simultaneously with the gate electrode. Next, FIG. 3 (b)
As shown in FIG. 4, the surface (front surface) on which the element portion is formed on the GaAs substrate 1 is attached to the glass plate 8 with the attaching material 7 (eg, negative resist) by using the conventional technique. At this time, bubbles 9 are generated inside the sticking material 7 due to variations in the coating film thickness at the time of applying the sticking material 7, the heat history or stress of the sticking method and the working process. Then
The back surface of the GaAs substrate 1 is polished and thinned to a thickness of 30 to 150 μm to form a conductive film 11 having a via hole 10, a titanium thickness of 500 Å and a gold thickness of 2000 Å, and then using the photoresist 15 as a mask. The PHS 12 is formed by gold plating with a thickness of about 30 μm. Next, as shown in FIG.
Conductive film 1 in element isolation region 13 using HS 12 as a mask
After etching 1 by ion milling, the same PH
Using S12 as a mask, the GaAs substrate 1 is etched with a chlorine-based gas to expose the laminated metal film 6. next,
As shown in FIG. 3D, using the PHS 12 as a mask, the laminated metal film 6 in the element isolation region 13 is removed by etching by ion milling to complete the isolation between the elements. After that, the hardened layer 14 on the surface of the bonding material 7 formed when the laminated metal film 6 is removed by etching by ion milling is removed by oxygen (O ₂ ) plasma. Finally,
The GaAs substrate 1 which has been separated into elements in the state of being attached to the glass plate 8 of FIG. 3D is separated into individual elements by removing the attaching material 7 by a cleaning method using a conventional technique. The semiconductor device manufacturing process is completed.

Further, as a second embodiment of the present invention, the following method can also be mentioned. In the first embodiment, GaAs
A laminated metal film which is formed simultaneously with the gate electrode 3 as a film for stopping the etching when the GaAs substrate 1 is removed by etching from the back surface of the substrate 1 by using the PHS 12 as a mask and chlorine-based gas, and has the same structure. 6 is used, a part of the source electrode (or drain electrode) can be used as the laminated metal film 6. In this case,
Thickness of gold germanium which is a constituent metal of the source electrode 15
00 angstrom, nickel thickness 500 angstrom, titanium thickness 500 angstrom, platinum thickness 1000 angstrom, gold thickness 2000 angstrom, titanium thickness 500 angstrom, platinum thickness 1000 angstrom, gold thickness By forming 2000 angstroms in the element isolation region at the same time, the laminated metal film 6 is formed, and the same effect as that of the first embodiment can be obtained.

Further, as a third embodiment of the present invention, an insulating film such as an oxide film is used instead of the laminated metal film from the back surface of the GaAs substrate using PHS as a mask with a chlorine-based gas to form Ga.
It can also be used as an etching control film when removing the As substrate by etching. In this case, the oxide film formed as an insulating film between the element gate, source and drain electrodes by the conventional technique can be used as a film for stopping etching by leaving the oxide film in the element isolation region.
The film for stopping the etching due to the oxide film can be removed by wet etching, and it is effective in preventing the deterioration hardening layer due to the dry etching on the surface of the bonding material.

[0012]

As described above, according to the present invention, GaA
By forming a laminated metal film or the like at the same time as a gate electrode or the like in the element isolation region on the substrate, chlorine-based gas is used to separate the glass plate and GaAs in the element isolation process of the semiconductor device having the PHS structure.
It is possible to prevent the generation of a hardened layer on the surface of the adhesive material over a wide range, which can be caused by infiltration into the air bubbles generated inside the adhesive material that adheres the substrate, and it is easy to remove the hardened layer by oxygen plasma. To Due to this effect, it is possible to prevent the production yield from being deteriorated due to the stains that are generated when the hardened layer is reattached to the semiconductor device during the removal of the adhesive in the cleaning method using the conventional technique.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor device obtained according to an embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor device obtained according to an embodiment of the present invention.

FIG. 3 is a process cross-sectional view showing one embodiment of the present invention in process order.

FIG. 4 is a cross-sectional view of a semiconductor device according to a conventional example.

FIG. 5 is a plan view of a semiconductor device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 GaAs substrate 2 Insulating film 3 Gate electrode 4 Source electrode 5 Drain electrode 6 Laminated metal film 7 Adhesive material 8 Glass plate 9 Bubbles 10 Via hole 11 Conductive film 12 PHS 13 Element isolation region 14 Hardened layer (by ion milling) 15 Photoresist 16 Hardened layer (by chlorine gas)

Claims (2)

[Claims] 1. An element portion including a gate electrode, a source electrode and a drain electrode is formed on the surface of a semi-insulating compound semiconductor substrate, and at the same time as the formation of the gate electrode, the source electrode or the drain electrode, the whole or a part thereof. Forming a laminated metal film having the same structure in the element isolation region of the substrate, attaching a reinforcing plate to the element forming surface of the substrate via an attaching material, and forming P on the back surface of the substrate.
Forming an energization film for HS (Plated Heat Sink) plating and PHS in a predetermined pattern; etching the energization film from the back surface of the substrate using the PHS as a mask; And a step of etching the element isolation region of the substrate from the back surface, wherein the laminated metal film is used as a film for stopping etching during etching of the substrate. 2. An element portion including a gate electrode, a source electrode and a drain electrode, and an insulating film between the electrodes is formed on the surface of a semi-insulating compound semiconductor substrate, and the substrate is formed at the same time when the insulating film is formed. A step of forming an insulating film in the element isolation region, a step of attaching a reinforcing plate to the element forming surface of the substrate via an attaching material, and a PHS on the back surface of the substrate.
(Plated Heat Sink) A step of forming a conductive film for plating and a PHS having a predetermined pattern, a step of etching the conductive film from the back surface of the substrate using the PHS as a mask, and a back surface of the substrate using the PHS as a mask. And a step of etching the element isolation region of the substrate, wherein the insulating film is used as a film for stopping etching during the etching of the substrate.