JP2792421B2 - Method for manufacturing semiconductor device - Google Patents

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), 4 is the GaAs substrate 1 The gold / platinum / titanium / nickel / gold / germanium (A
u / Pt / Ti / Ni / Au.Ge), 5 is a drain electrode formed simultaneously with the source electrode, 8 is a glass plate serving as a reinforcing plate, 7 is a GaAs substrate 1 on the glass plate 8. Pasting material for pasting, 10 is a via hole, 12 is a 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 an element isolation region 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]

4 and 5, the element isolation region 13 is formed by etching the conductive film 11 by ion milling using the PHS 12 as a mask, and then forming the same. PHS12
Is used to etch the GaAs substrate 1 by dry etching technology. In this case, however, 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 heat generated in the GaAs substrate. A PHS structure is formed by a conventional technique after polishing and etching from the back surface to a desired thickness in a state where the front side on which the FET is formed is attached to a transparent plate such as a glass plate. Thereafter, the GaAs substrate is etched by dry etching using PHS or a photoresist as a mask to perform element isolation.

In this case, however, there is a gap between the glass plate and the GaAs substrate attached by the adhesive due to the applied film thickness at the time of application of the adhesive, the attaching method, and the heat history or stress of the working process. Alternatively, there is a problem that air bubbles are generated. The surface of the adhesive material exposed after etching the GaAs substrate for element isolation is altered and hardened by the etching gas, and the altered hardened layer can be removed by ashing with oxygen (O ₂ ) plasma. However, when the etching gas enters the gaps or bubbles and the surface of the adhesive material over a wide area is altered and hardened, it is difficult to remove the altered hardened layer by ashing with O ₂ plasma, and it is difficult to remove GaAs after element isolation. When the substrate is peeled off from the glass plate by a conventional method, the deteriorated hardened layer that cannot be completely removed adheres to the FET formed on the GaAs substrate, impairing the appearance and deteriorating the manufacturing yield. In order to prevent the appearance yield from deteriorating, it is necessary not to form the above-mentioned altered hardened layer which cannot be completely removed. An object of the present invention is to provide a method of manufacturing a semiconductor device which solves such a conventional problem and does not form an altered hardened layer which 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 a surface of a semi-insulating compound semiconductor substrate, and the formation of the gate electrode, the source electrode or the drain electrode is performed. At the same time, a step of forming a laminated metal film having the same structure as the whole or a part thereof 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 adhesive, 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; Etching a device isolation region of the substrate from the back surface of the substrate, wherein the laminated metal film is used for etching the substrate. A method of manufacturing a semiconductor device, which comprises using as the film to stop the etching.

The present invention also provides a method for forming an element portion including a gate electrode, a source electrode, and a drain electrode on a surface of a semi-insulating compound semiconductor substrate and an insulating film between the electrodes, and forming the insulating film. At the same time, a step of forming an insulating film in an element isolation region of the substrate, a step of attaching a reinforcing plate to an element formation surface of the substrate via an adhesive, 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, etching the conductive film from the back surface of the substrate using the PHS as a mask, and isolating the substrate from the back surface of the substrate using the PHS as a mask. Etching a region, wherein the insulating film is used as a film for stopping etching at the time of etching the substrate. It is.

[0007]

According to the present invention, an element portion including a gate electrode, a source electrode, a drain electrode and an active region is first formed on a GaAs substrate by a conventional technique. 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 on which the element is formed on the GaAs substrate is attached to a reinforcing plate with an adhesive, and Ga is formed by a conventional technique.
The back surface of the As substrate is polished and thinned to form via holes and PHS. Using the PHS as a mask, the element isolation region of the GaAs substrate is etched away 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 perform element isolation of the GaAs substrate. Here, the laminated metal film prevents the etching gas from penetrating into gaps and bubbles generated inside the adhesive material during dry etching of the element isolation region of the GaAs substrate, thereby preventing the adhesive material from being altered and hardened. Therefore, the altered hardened layer of the adhesive is formed only on the surface, and is easily removed by ashing with O ₂ plasma. Further, an insulating film may be used instead of the laminated metal film. In this case,
The oxide film formed as an insulating film between the gate, source, and drain electrodes of the element portion 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 by the oxide film can be removed by wet etching, which is effective in preventing a deteriorated hardened layer due to dry etching on the surface of the adhesive material.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a semiconductor device obtained by the method of the present invention, and FIG.
It is sectional drawing by a line. In FIG. 1, a GaAs substrate 1
An element including a gate electrode 3, a source electrode 4, and a drain electrode 5 is formed thereon 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, the etching gas is prevented from penetrating into gaps or bubbles generated inside the adhesive material, thereby preventing the adhesive material from being altered and hardened. The laminated metal film 6 is formed. As shown in FIG. 2, the surface (surface) of the GaAs substrate 1 on which the elements are formed is fixed to a glass plate 8 as a reinforcing plate by an adhesive 7. The bubbles 9 are generated due to a variation in the applied film thickness when the adhesive 7 is applied, a heat history or a stress during the attaching method and the processing process. G
The via hole 10 and the conductive film 1 are provided on the back surface of the aAs substrate 1.
1. The PHS 12 is formed. After removing the conductive film 11 using the PHS 12 as a mask, the element isolation region 13 is used as a film for stopping the etching of the laminated metal film 6 to form a Ga.
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 FIG. 1A, after an insulating film 2 is formed on a GaAs substrate 1 on which an active layer region is formed by a conventional technique, a thickness of 500 Å of titanium (Ti) and a thickness of platinum (Pt) are formed by a vapor deposition method. A gate electrode 3 having a thickness of 1000 angstroms and a thickness of 2000 angstroms of gold (Au); a thickness of 1500 angstroms of gold germanium; a thickness of 500 angstroms of nickel; a thickness of 500 angstroms of titanium;
An element portion composed of the source electrode 4 and the drain electrode 5 each having a thickness of Å and a thickness of 2,000 Å of gold is formed. When the gate electrode 3 is formed, the laminated metal film 6 having the same structure is formed in the element isolation region 13 simultaneously with the gate electrode. Next, FIG.
As shown in FIG. 1, the surface (surface) on which the element portion is formed on the GaAs substrate 1 is attached to the glass plate 8 with an adhesive 7 (for example, a negative resist) using a conventional technique. At this time, bubbles 9 are generated in the inside of the bonding material 7 due to a variation in the applied film thickness when the bonding material 7 is coated, a heat history or a stress in the bonding method and the processing process. Then
The back surface of the GaAs substrate 1 is polished and thinned to a thickness of 30 to 150 μm, and a via hole 10, a conductive film 11 having a thickness of 500 Å of titanium and a thickness of 2,000 Å of gold are formed, and the photoresist 15 is used as a mask. The PHS 12 is formed by gold plating having a thickness of about 30 μm. Next, as shown in FIG.
Using the HS 12 as a mask, the conductive film 1 in the element isolation region 13
After etching 1 by ion milling,
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 stacked metal film 6 in the element isolation region 13 is removed by etching by ion milling to complete the isolation between the elements. Thereafter, the hardened layer 14 on the surface of the adhesive 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 from elements in the state of being bonded to the glass plate 8 of FIG. 3D is separated into individual elements by removing the bonding material 7 by a cleaning method using a conventional technique. Then, the manufacturing process of the semiconductor device is completed.

[0010] As a second embodiment of the present invention, the following method is also mentioned. In the first embodiment, GaAs
Using the PHS 12 as a mask, a laminated metal film formed simultaneously with the gate electrode 3 and having the same structure as a film for stopping the etching when the GaAs substrate 1 is etched and removed with a chlorine-based gas from the back surface of the substrate 1 Although 6 is used, a part of the source electrode (or the drain electrode) may be used as the laminated metal film 6. In this case,
Thickness of gold germanium which is a constituent metal of source electrode 15
00 Å, nickel 500 Å, titanium 500 Å, platinum 1000 Å, gold 2,000 Å, titanium 500 Å, platinum 1000 Å, and gold By simultaneously forming 2,000 Å in the element isolation region, the laminated metal film 6 is obtained, and the same effect as in the first embodiment can be obtained.

In a third embodiment of the present invention, an insulating film, such as an oxide film, is formed from the back surface of a GaAs substrate using a PHS as a mask with a chlorine-based gas instead of a laminated metal film.
It can be used as an etching control film when the As substrate is removed by etching. In this case, an oxide film formed as an insulating film between the gate, source, and drain electrodes of the element portion 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 by the oxide film can be removed by wet etching, which is effective in preventing a deteriorated hardened layer due to dry etching on the surface of the adhesive material.

[0012]

As described above, according to the present invention, GaAs is used.
By forming a laminated metal film and the like at the same time as the gate electrode and the like in the element isolation region on the s substrate, in the element isolation step of the semiconductor device having the PHS structure, the chlorine-based gas and the GaAs
It is possible to prevent the formation of a deteriorated hardened layer on the surface of the adhesive material over a wide range, which can be caused by infiltrating the inside of the air bubbles generated inside the adhesive material on which the substrate is attached, and it is easy to remove the hardened layer by oxygen plasma. To With this effect, it is possible to prevent the production yield from deteriorating due to contamination caused by re-adhesion of the above-described cured layer to the semiconductor device at the time of removing the adhesive in the cleaning method using the conventional technique.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a plan view of a conventional semiconductor device.

[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-based gas)

──────────────────────────────────────────────────の Continued on the front page (58) Surveyed fields (Int.Cl. ⁶ , DB name) H01L 21/337-21/338 H01L 27/095 H01L 27/098 H01L 29/775-29/778 H01L 29 / 80-29/812 H01L 21/70-21/74 H01L 21/76-21/765 H01L 21/77

Claims (2)

(57) [Claims] An element portion including a gate electrode, a source electrode, and a drain electrode is formed on a 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, all or part thereof. Forming a laminated metal film having the same structure in an element isolation region of the substrate, attaching a reinforcing plate to an element formation surface of the substrate via an adhesive, and forming a P on the back surface of the substrate.
A step of forming an electrically conductive film for HS (Plated Heat Sink) plating and a PHS of a predetermined pattern; a step of etching the electrically conductive film from the back surface of the substrate using the PHS as a mask; and a step of etching the substrate using the PHS as a mask. Etching a device isolation region of the substrate from a back surface, wherein the laminated metal film is used as a film for stopping etching when etching 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 a surface of a semi-insulating compound semiconductor substrate, and the substrate is formed simultaneously with the formation of the insulating film. Forming an insulating film in the element isolation region of step (a), bonding a reinforcing plate to the element forming surface of the substrate via a bonding material, and forming 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 using the PHS as a mask from the back surface of the substrate; and a back surface of the substrate using the PHS as a mask. Etching a device isolation region of the substrate, wherein the insulating film is used as a film for stopping etching when etching the substrate.