JPS62281367A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device that integrally includes a bipolar transistor and a Schottky diode element.

[Conventional technology]

Conventionally, as a method for manufacturing a semiconductor device having a bipolar transistor and a Schottky diode integrated on a semiconductor substrate, a method has been adopted in which a graft base of the transistor and a guard ring layer of the Schottky diode are simultaneously formed. However, in the method that has been widely used in recent years to improve the performance of bipolar transistors, that is, the method in which the emitter and base electrodes are formed separately using a self-alignment method using polycrystalline silicon, the guard ring of the Schottky diode is It is difficult to form layers.

Therefore, as shown in FIG.
1, an N-type buried collector 302 and an N-type epitaxial layer 303 are formed, and a silicon oxide film 30 for element isolation is formed.
4, the silicon nitride film 312 that separates the emitter polycrystalline silicon electrode 310 and the base polycrystalline silicon layer 311 is removed using the photoresist 315 as a mask, and then the silicon oxide film 313 that separates the polycrystalline silicon 311 is removed. A silicon oxide film 314 is removed to separate the N-type epitaxial layer 303 and polycrystalline silicon 311.
By removing the N-type epitaxial layer 30
There is no choice but to adopt a method of exposing the surface of 3 and forming a Schottky diode there.

[Problem that the invention seeks to solve]

In the method shown in FIG. 3 described above, since the thick multilayer insulating films 312, 313, and 314 once formed are removed, the contact step difference in the Schottky diode becomes large and the coverage of the metal electrode deteriorates. Further, since no guard ring is formed, problems arise such as a high performance Schottky diode cannot be obtained.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention forms the emitter and base electrodes of a bipolar transistor in a self-aligned manner using polycrystalline silicon, and also enables the formation of a guard ring in a Schottky diode in a self-aligned manner. This will improve the performance of the device.

The method for manufacturing a semiconductor device of the present invention includes the steps of forming a first insulating film at a Schottky diode forming position on a -4 voltage type semiconductor substrate, and forming a second insulating film in contact with the first insulating film. A first polycrystalline silicon film of a conductivity type is formed, and the first polycrystalline silicon film in a region including the first insulating film is selectively removed to form a first insulating film and a second insulating film. a step of exposing the second insulating film, and applying an under force to the second insulating film.
forming a second polycrystalline silicon film, and applying a graft base of an opposite conductivity type to the semiconductor substrate through the second polycrystalline silicon film and using the first insulating film as a mask. forming a guard ring, forming a base region and a second guard ring by ion implantation, and removing the first insulating film to expose the main surface of the semiconductor substrate surrounded by the guard ring. This includes a step of forming a Schottky diode.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) FIGS. 1(a) to 1(h) are cross-sectional views showing a first example of the present invention in the order of manufacturing steps.

First, as shown in FIG. 5A, a highly concentrated N-type buried collector 102 of the opposite conductivity type is selectively formed on a P-type silicon substrate 101, and a region including this N-type buried collector 102 is then formed. There are 1 to 2 low concentration N-type epitaxial layers 103 on top.
Formed with a thickness of μm. Subsequently, a silicon oxide film 104 is formed by selective oxidation to isolate element regions. After that, silicon nitride 115j10 is used as the first insulating film.
The silicon nitride film 105 is selectively removed so as to leave the silicon nitride film 105 in the Schottky diode formation region. Furthermore, using this silicon nitride film 105 as a mask, a silicon oxide film 106 as a second insulating film is formed by about 2,500 people by thermal oxidation.

Next, as shown in FIG. 4B, a first polycrystalline silicon film 107 is grown to a thickness of 3,000 to 4,000 wafers over the entire surface. Then, selective oxidation is performed on this first polycrystalline silicon film 107 using a silicon nitride film (not shown), which is an oxidation-resistant film, to form a silicon oxide film 108.

After that, aluminum 109 was used as a mask for ion implantation.
etc., high concentration poron is ion-implanted into the first polycrystalline silicon film 107, and the first polycrystalline silicon film 1
07 is a P-type polycrystalline silicon film.

Next, as shown in FIG.
A silicon nitride film 110 is formed to a thickness of 2,000 to 3,000 wafers. Then, apply photoresist 111 to the required locations.
The second silicon nitride film 110 and the first polycrystalline silicon film 107 are sequentially anisotropically etched by reactive ion etching (RTE) using this pattern as a mask, and the first silicon Parts of the nitride film 105 and silicon oxide film 106 are exposed.

Subsequently, as shown in FIG. 3(d), the photoresist 111 is removed and a third silicon nitride film 1 is deposited on the entire surface by CVD.
12 to a thickness of 1000 to 2000 people, and further RT
By anisotropically etching the third silicon nitride film 112 using the E method, the third silicon nitride film 112 is left only on the side surfaces of the opening in the first polycrystalline silicon film 107. As a result, the second silicon nitride film 110 and the third silicon nitride film 112 are integrated.

Next, the exposed silicon oxide film 106 is removed using Hasofford hydrofluoric acid solution. At this time, the silicon nitride film 106 extends approximately 5.5 mm to the bottom of the first polycrystalline silicon film 107.
000 side etching and undercut.

Next, as shown in FIG. 8 (8), 2000 to 4000 layers of the second polycrystalline silicon film 113 are grown to backfill the undercut portion, thereby connecting it to the first polycrystalline silicon film 107. .

Then, heat treatment at 900°C for 20 to 30 minutes
The boron contained in the polycrystalline silicon film 107 of
polycrystalline silicon film 113 and N-type epitaxial layer 1
03 and the graft base 114 of the transistor
At the same time, the first guard ring region 115 of the Schottky diode is formed. Subsequently, selective etching is carried out so that the second polycrystalline silicon film 113 remains only in the backfilling portion of the undercut by utilizing the difference in etching rate of the polycrystalline silicon film due to the difference in boron content concentration.

Further, the exposed side surfaces of the second polycrystalline silicon film 113 and the surface of the N-type epitaxial layer 103 are oxidized to form a silicon oxide film 116 to a thickness of approximately 500 nm. Next, apply boron to the entire surface at a thickness of 1.0 to 5°Q x 10”c.
Ion implantation is performed at a dose of m-'' to form a P-type active base region 117, and a second guard ring region 1 is formed.
form 18.

At this time, since the Schottky diode formation region is covered with the first silicon nitride film 105, boron is not implanted.

Next, as shown in FIG.
9 to 1,000 to 2,000 people using the CVD method. Subsequently, this fourth silicon nitride film 119 is formed by RIE method.
By anisotropically etching the fourth silicon nitride film 119, the fourth silicon nitride film 119 remains only on the side surfaces of the groove-shaped portion.

Then, a photoresist 120 is patterned so as to leave the photoresist on the Schottky diode formation region, and the silicon oxide film 116 in the emitter formation region is selectively removed using a bath-faded hydrofluoric acid solution, and the active base 116 in the emitter formation region is removed. expose the surface of

Furthermore, as shown in the same figure (g), a photoresist 120-t
- After removal, the third polycrystalline silicon film I21 is
Grows from 0 to 3000 people and arsenic 5.0 x 1015 on the entire surface
~1. Ion implantation was performed at a dose of Ox 10 I6 cm-2, and forced diffusion was performed at 900 to 950°C.
An N-type emitter 122 is formed within the P-type active base 117 to form a bipolar transistor.

At this time, the silicon nitride film 105 and the silicon oxide film 116 serve as masks in the Schottky diode formation region, and arsenic is not diffused. Furthermore, since the distance between the N-type emitter 122 and the P-type graft base 114 is maintained in a well-controlled manner by the fourth silicon nitride film 119, a breakdown voltage drop does not occur due to contact between the high concentration regions of opposite conductivity types.

Thereafter, a photoresist pattern 123 is formed, and the third polycrystalline silicon 121 into which arsenic ions have been implanted is selectively removed to form a floating electrode.

After that, as shown in the same figure (h), 2,000 to 3,000 silicon oxide films 124 are grown by the CVD method to form emitters, Schottky diodes, and various contact holes such as bases, collectors, and resistors (not shown). R.I.
Holes are opened using the E method. As a result, the N-type epitaxial layer 103 and the second guard ring layer 118 are exposed in the Schottky diode region, so a Schottky material such as platinum is deposited thereon to a thickness of 300 to 800 nm, and then A Schottky diode can be formed by heat-treating and forming platinum silicide 125.

At this time, platinum silicide 125 is also formed in other contact parts.

Thereafter, electrode wiring is formed using aluminum 126 by a normal method to complete the semiconductor device.

Therefore, in this embodiment, the graft base 114 and emitter 122 of the transistor can be formed in a self-aligned manner, and the guard rings 115 and 118 of the Schottky diode can also be formed in a self-aligned manner.

In addition, in the semiconductor device configuration in which the transistor and the Schottky diode are integrated and the first polycrystalline silicon is connected to the graft base and the guard ring, respectively, the Schottky diode can be easily used as a clamp diode. Can be used.

(Embodiment 2) FIGS. 2(a) to 2(C) are cross-sectional views showing a second embodiment of the present invention in the order of steps.

First, as shown in the same figure (a), an N-type buried collector 202 and an N-type epitaxial layer 203 are formed on a P-type silicon substrate 201.
A silicon oxide film 2 is formed thereon by selective oxidation.
04 is formed, and a silicon nitride film 205 as a second insulating film is grown to a thickness of 1,000 to 2,000 nm using the CVD method. Then, the silicon nitride film 205 is selectively removed, and then a silicon oxide film 206 as a first insulating film is formed in the Schottky diode formation region by thermal oxidation.
form.

Next, a P-type polycrystalline silicon film 207 is formed, a photoresist 211 is patterned, and using this as a mask, the polycrystalline silicon film 207 is selectively removed by RIE, thereby forming a silicon oxide film 206 and a silicon nitride film. A part of 205 is exposed.

Next, as shown in FIG. 2B, the photoresist 211 is removed, and a silicon oxide film 212 is formed on the surface of the first polycrystalline silicon 207 by thermal oxidation, and the silicon oxide film 206 is thickened.

Then, the silicon nitride film 205 is side etched to the bottom of the first polycrystalline silicon film 207 to form an undercut.

Furthermore, the second polycrystalline silicon film 213 is selectively backfilled, and a graft base 214 and a first guard ring 215 are formed. Then, a silicon oxide film 216 is formed on the exposed surfaces of the second polycrystalline silicon film 213 and the N-type epitaxial layer 2030. Subsequently, boron ions are implanted to form a P-recoverable base 217, and a second guard ring layer 218 is also formed.

At this time, since the region where the Schottky diode is to be formed is covered with a thick silicon oxide film 206, boron ions are not implanted.

Thereafter, as shown in FIG. 2(c), a second silicon nitride film 219 is grown to a thickness of 1,000 to 2,000 nm using the CVD method, and then this second silicon nitride film 219 is anisotropically grown using the RIE method. Then, the second silicon nitride film 219 is left only on the side surfaces of the groove-shaped portion.

Hereinafter, similarly to the first embodiment, a bipolar transistor is formed by selectively removing the silicon oxide film 216 in the emitter formation region and forming an emitter 222 and a third polycrystalline silicon film 221 that will become an emitter electrode. be done.

At this time, the surface of the N-type epitaxial layer 203 surrounded by the guard ring layer 218 is exposed by removing part of the silicon oxide film 206 and the silicon oxide film 216 in the Schottky diode formation region, and platinum silicide is deposited on this surface. By forming 225, it is possible to form a Shore-key diode.

In the figure, 224 is a silicon oxide film.

In this embodiment, the same effects as in the first embodiment can be obtained, and since the insulating film on the first polycrystalline silicon 207 is a silicon oxide film 212 formed by thermal oxidation, the first This has the advantage that the step shape is gentler than that of the embodiment, and the coverage of the aluminum 226 is better.

〔Effect of the invention〕

As explained above, the present invention forms a first insulating film and a second insulating film on a -i conductivity type semiconductor substrate, forms a polycrystalline silicon film of an opposite conductivity type thereon, and forms a polycrystalline silicon film of an opposite conductivity type. forming a graft base of an opposite conductivity type and a first guard ring on the semiconductor substrate through the silicon film and using the first insulating film as a mask, and further forming a base region and a second guard ring by ion implantation; and then removing the first insulating film to expose the main surface of the semiconductor substrate surrounded by the guard ring to form a Schottky diode. base.

A high performance bipolar transistor and a Schottky diode can be easily formed by forming them in a self-aligned manner and at optimal positions, similar to the graft base.

[Brief explanation of the drawing]

FIGS. 1(a) to (h) are cross-sectional views showing the first embodiment of the present invention in the order of manufacturing steps, and FIGS. 2(a) to (c) are cross-sectional views showing the second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the main steps of the embodiment. FIG. 3 is a cross-sectional view for explaining the conventional method. Lot, 201, 301...P type silicon substrate, 10
2.202,302...N-type embedded collector, 103.
203, 303... N-type epitaxial layer, 104.
...Silicon oxide film, 105...Silicon nitride film (first insulating film), 106...Silicon oxide film (second insulating film), 107...Polycrystalline silicon, 108...Silicon oxide Film, 109... Aluminum, 110...
- Second silicon nitride film, 111... Photoresist, 112... Third silicon nitride film, 113... Second polycrystalline silicon, 114... Graft base, 1
15... First guard ring, 116... Silicon oxide film, 117... Active base, 118... Second guard ring, 119... Fourth silicon nitride film, 1
20... Photoresist, 121... Third polycrystalline silicon, 122... Emitter, 123... Photoresist, 124... Silicon oxide film, 125...
Platinum silicide, 126...aluminum, 204...
... silicon oxide film, 205 ... silicon nitride film (second insulating film), 206 ... silicon oxide film (first insulating film) 207 ... polycrystalline silicon, 211 ... photoresist, 212...Silicon oxide film, 213...
- Second polycrystalline silicon, 214... Graft base, 215... First guard ring, 216... Silicon oxide film, 217... Active base, 218... Second guard ring, 219...Silicon nitride film, 22
1... Silicon oxide film, 222... Emitter, 22
4... Silicon oxide film, 225... Platinum silicide, 304... Silicon oxide film, 310... Emitter polycrystalline silicon electrode, 311... Base polycrystalline silicon electrode, 312... Silicon nitride film , 313... silicon oxide film, 314... silicon oxide film, 315...
...Photoresist.

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor device having a bipolar transistor and a Schottky diode on a semiconductor substrate, a first insulating film is formed at a Schottky diode formation position on a semiconductor substrate of one conductivity type, and a second forming a first polycrystalline silicon film of opposite conductivity type and selectively removing the first polycrystalline silicon film in a region including the first insulating film to form a first polycrystalline silicon film; A step of exposing a part of an insulating film and a second insulating film, a step of undercutting the second insulating film, forming a second polycrystalline silicon film, and forming a second polycrystalline silicon film. forming a graft base of an opposite conductivity type and a first guard ring on the semiconductor substrate using the first insulating film as a mask; and forming a base region and a second guard ring by ion implantation. . A method of manufacturing a semiconductor device, comprising: removing the first insulating film to expose a main surface of the semiconductor substrate surrounded by the guard ring, and forming a Schottky diode there.