JPH02122669A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the size of an SBD, to eliminate photoresist process and to reduce the cost by forming a smaller self-matching pattern when a silicon nitride pattern is formed and forming a self-matching guard ring region while employing the smaller pattern. CONSTITUTION:A silicon oxide film 104 is formed at the inside of a photoresist film 105. Then the photoresist film 105 is masked again and a silicon nitride film 103 is etched, then the silicon nitride film 103 is patterned similarly to the photoresist film pattern. Thereafter, the photoresist film 105 is removed and thermal oxidation is carried out thus oxidizing the silicon substrate 101 not covered with the silicon nitride film 103 and forming an oxidation film 106 selectively on the surface. Then boron is added onto the surface of the silicon substrate 101 through the thin silicon nitride film 103 and an oxidation film 102 thus forming a p-type guard ring region 107.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a Schottky barrier diode (hereinafter abbreviated as SBD).

[Conventional technology]

A diode that uses a barrier that occurs at the contact interface between a metal and a semiconductor is generally called a Schottky barrier diode (SBD).
), but this SBD is often used in integrated circuits because it has lower forward exposure and smaller parasitic capacitance than a diode using a normal p-n junction. but,
In such an SBD, the metal electrode is usually only in contact with the semiconductor substrate in a plane, so when reverse exposure is applied to the SBD, the electric field is concentrated at the end of the part of the metal electrode in contact with the semiconductor substrate, and the withstand voltage decreases. As a result, a leakage current occurs, and to prevent this leakage current, an impurity region (guard ring) of a conductivity type opposite to that of the substrate is generally placed on the outer periphery of the metal electrode in contact with the semiconductor substrate. )
is formed.

Below, a method for manufacturing a conventional SBD equipped with a guard ring will be explained using FIGS. 3(a) to 3(f).

As shown in FIG. 3(a), an oxide film 302 and a silicon nitride film 303 are sequentially formed on the surface of an n-type silicon substrate 301 as shown in FIG. 3(a). The oxide film 302 and silicon nitride film 303 are formed to a thickness of about 500 and 1000, respectively.

Next, after applying a photoresist film 305 to the entire surface, it is selectively formed at desired positions, and this photoresist film 305 is
The silicon nitride film 303 is removed using HF solution using No. 5 as a mask as shown in FIG. 3(b).

Next, the photoresist film 305 is removed, followed by thermal oxidation. At this time, since the remaining silicon nitride film 303 is an oxidation-resistant film, the silicon substrate 301 covered with the remaining silicon nitride film 303 is not oxidized, while the silicon substrate 301 not covered with the silicon nitride film 303 is oxidized. Then, as shown in FIG. 3(c), an oxide film 3 is selectively formed on the substrate surface.
06 is formed. This selective oxidation film 306 is formed on the crotch by oxidizing it in a steam atmosphere at 1000°C for 60 minutes, and then
．． It is appropriate to set the film thickness to 8 to 1.0 μm.

Next, in order to form a guard ring portion, a photoresist film 313 is first applied over the entire surface, and then selectively formed in a region surrounded by a selective oxide film 306. Next, using the photoresist film 313 and selective oxide film 306 as a mask, poron is added to the surface of the silicon substrate 301 by ion implantation through the thin silicon nitride film 303 and oxide film 302 to form a p-type guard ring region 307. Figure 3(d)
form like this. The poron ion implantation conditions at this time were an energy of 60 KeV and a dose of 5E13 cm-2.
It is appropriate to do so.

Next, the photoresist film 313 is removed, heat treatment is performed to activate the added poron, and silicon crystal defects are removed by ion implantation. Subsequently, the silicon nitride film 303 and the oxide film 302 are removed to form the p-type guard ring region 307 and the n-type guard ring region 307.
The surface of the mold silicon substrate 3010 is exposed, and a platinum silicide layer 308 is formed on the substrate surface as shown in FIG. 3(e). This platinum silicide layer 308 is formed by depositing a platinum thin film on the substrate surface and performing heat treatment, so that platinum silicide is formed in the area that is in contact with silicon, and the platinum on the surface of the oxide film 306 remains unchanged as a platinum thin film. Since this remains, only the platinum is removed using aqua regia.

Next, electrodes made of a titanium/tungsten thin film 309 and an aluminum thin film 310 are selectively formed.
An SBD having a guard ring region 3θ7 as shown in
complete. The titanium/tungsten film 309 is provided to prevent the aluminum thin film 310 from reacting with the platinum silicide layer 308 and changing the SBD characteristics due to the platinum silicide layer.

Although not shown, the other electrode corresponding to one electrode 310 of this SBD is the silicon substrate 301 itself, and may be formed on the bottom surface of the silicon substrate 301.

[Problem to be solved by the invention]

In the conventional SBD manufacturing method described above, a photoresist (313) is newly provided in order to form the p-type guard ring region 307 in the step shown in FIG. 3(d). In order to reliably provide the guard ring region 307, it is necessary to form the photoresist I-[313 with a certain degree of alignment margin, which has the disadvantage that the area increases by the alignment margin.

Further, the SBD characteristics are easily influenced by the area of the SBD formation region.

〔the purpose〕

An object of the present invention is to provide a manufacturing method that can form a guard ring region of an SBD without relying on alignment of photoresist films.

[Means to solve the problem]

The manufacturing method of the present invention includes the steps of forming a first insulating film and a second insulating film including an oxidation-resistant film on the surface of a semiconductor substrate of a first conductivity type, and forming at least this insulating film on the second insulating film. A process of selectively forming a mask film that becomes a mask during etching between the second insulating film and the oxidation-resistant film, and using this mask film, the second insulating film is reduced to approximately the same distance from the edge of the mask film. a step of etching the oxidation-resistant film into the same shape as the mask film; a step of oxidizing the semiconductor substrate using the oxidation-resistant film as a mask to selectively form an oxide film; forming a second conductivity type guard ring region on the semiconductor substrate surface in a self-aligned manner through a gap formed between the selectively formed oxide film and the second insulating film;
The method includes a step of depositing and forming a metal or alloy layer on a portion of the semiconductor substrate surrounded by the guard link region. That is, according to the present invention, there is no need to consider the alignment margin of the photoresist film when forming the guard ring region, and the device can be downsized.

〔Example〕

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

A first embodiment of the present invention will be described with reference to FIGS.

A first insulating film consisting of an oxide film 102 and a silicon nitride film 103 is formed on the surface of an n-type silicon substrate 101, and then a second insulating film of a silicon oxide film 104 is formed by vapor phase epitaxy (see FIG. 1). Form as in a). This oxide film 102
．． It is appropriate that the silicon nitride film 103 and the silicon oxide film 104 grown by vapor phase growth have a thickness of about 500, 1,000, and 5,000, respectively. The n-type silicon substrate is preferably an n-type epitaxial layer formed by epitaxial growth on a p-type silicon substrate having selectively formed n-type regions, but only the epitaxial layer is shown in the figure.

Next, as shown in FIG. 1(b), a photoresist film 105 is
is selectively formed at a desired position, and a silicon oxide film 10 is grown by vapor phase growth using this photoresist film 105 as a mask.
4 is formed by overetching so that the edge of the pattern is inside the edge of the photoresist film 105.

Subsequently, the silicon nitride film 103 is etched again using the photoresist film 105 as a mask using an anisotropic etching method, and the silicon nitride film 103 is patterned into the same shape as the photoresist film pattern.

In addition to the above methods, there are also the following methods. That is, by anisotropic etching, the silicon oxide film 104 and the silicon nitride film 103 are grown by vapor phase growth using the photoresist film 105 as a mask.
are continuously etched into the same shape as the photoresist film. Thereafter, the silicon oxide film 104 grown by vapor phase growth is additionally etched by isotropic etching to obtain a desired shape. However, at this time, the thin oxide film 102 is also etched at the same time, but the shape and manufacturing method used in the subsequent process have no effect.

Next, the photoresist film 105 is removed, followed by thermal oxidation. At this time, since the remaining silicon nitride film 103 is an oxidation-resistant film, the silicon substrate 101 covered with the remaining silicon nitride film 103 is not oxidized, while the silicon substrate 101 not covered with the silicon nitride film 103 is oxidized. Then, an oxide film 106 is selectively formed on the surface as shown in FIG. 1(c). This selective oxide film 106 is 1000
Oxidized for 60 minutes in a steam atmosphere at ℃, 0.8~1.0μ
It is appropriate to set the film thickness to m.

Next, as shown in FIG. 1(d), the silicon substrate 101 is implanted by ion implantation through the thin silicon nitride film 103 and oxide film 102 using the residual vapor phase epitaxy method silicon oxide film 104 and selective oxide film 106 as masks. Boron is added to the surface to form a p-type guard ring region 107. The conditions for boron ion implantation at this time are that the energy is 6
0KeV.

It is appropriate to set the dose amount to 5E13 cm to 2 or more.

Next, heat treatment is performed to activate the added boron and to remove silicon crystal defects by ion implantation. Subsequently, the remaining silicon oxide film 104 . The silicon nitride film 103 and thin oxide film 102 are removed to expose the surfaces of the p-type guard ring region 107 and the n-type silicon substrate 101, and a platinum silicide layer 108 is formed on these surfaces as shown in FIG. 1(e). do.

Next, electrodes made of the titanium/tungsten thin film 109 and the aluminum thin film 110 are selectively formed to complete the SBD having the guard ring region 107 (Fig. 1 ()).
.

In the present invention, a method for manufacturing an SBD using a platinum silicide layer has been described, but after exposing the surfaces of the p-type guard ring region 107 and the n-type silicon substrate 101, immediately after selectively forming an electrode using an aluminum thin film, the platinum silicide layer is S with diode characteristics different from those due to
It is also possible to form a BD.

Although not shown in the figure, the aluminum electrode 1
The other metal electrode corresponding to 10 may be provided on the bottom surface of the silicon substrate 101, or an electrode may be provided in ohmic contact with the surface of the silicon substrate 101 and taken out.

A second embodiment of the present invention will be described with reference to FIGS. 2(a) to 2(h). This embodiment shows a case where a Schottky barrier diode is formed adjacent to a bipolar transistor as a clamp diode for preventing saturation operation of the bipolar transistor.

Since FIGS. 2(a) to 2(c) are the same as those in the first embodiment, description thereof will be omitted.

In FIG. 2(C), the remaining silicon oxide film 204
The silicon nitride film 203 that is not covered is removed in a self-aligned manner. This is suitably carried out in hot phosphoric acid at about 60°C. Subsequently, the remaining silicon oxide film 204 and thin oxide film 202 are removed at the same time, a gap is formed between the selective oxide film 206 and the silicon nitride film 203 that exposes the surface of the silicon substrate 2010 in a self-aligned manner, and heat treatment is performed. Poron is diffused onto the surface of the silicon substrate 20 through this gap to form a p-type guard ring region 207, and thermal oxidation is performed to form an oxide film 211 on the surface of the gap as shown in FIG. 2(d).

Next, the remaining silicon nitride film 203 is removed, and the thin oxide film 202 underneath it and the oxide film 211 formed in the previous step are removed. Subsequently, an oxide film 212 is formed again on the guard ring region 207 and the surface of the silicon substrate 201. This oxide film 212 can be formed by either thermal oxidation or vapor phase growth.
The film thickness is suitable for about 2000 people. Next, a photoresist film 213 is selectively formed, and as shown in FIG.
Poron is implanted into the surface of the silicon substrate 201 through 12 to form a p-type base region 214.

Next, the photoresist film 213 is removed and heat treatment is performed to activate the poron in the base region 214.

Next, as shown in FIG. 2(f), an opening is formed in the oxide film 212 above the p-type base region 214, and an n-type impurity is doped into the p-type base region through this opening to form an n-type emitter. Area 2
form 15.

Next, at least the oxide film 212 on the SBD formation region is removed, and a second platinum silicide layer 208, 208' is deposited on the opening provided for forming the n-type emitter region 215 in the above step and on the SBD formation region. Form as shown in figure (g). At this time, since the platinum silicide layer 208 is ohmically connected to the p-type base region 214 of the bipolar transistor, a part of the opening of the SBD is connected to the p-type base region 214.
It is appropriate to expose the surface of p.
A part of the surface of the mold guard ring region 207 is formed to be exposed.

Next, the method explained in the first embodiment and the conventional example is used as shown in FIG.
As shown in h), electrodes made of aluminum thin films 210 and 210' are formed on titanium/tungsten 209° and 209'.

Furthermore, as described in the first embodiment, it is also possible to simultaneously form the SBD and the electrode using only an aluminum film instead of the platinum silicide layer.

Although the present invention has been described above in detail with reference to embodiments, the scope of application of the present invention is not limited to the guard ring region of a Schottky barrier diode, but is also applicable to the formation of impurity regions used in semiconductor devices. obtain.

〔Effect of the invention〕

As explained above, in the present invention, when forming a pattern of a silicon nitride film for selectively forming an oxide film on the surface of a semiconductor substrate, a pattern smaller than this pattern is formed in a self-aligned manner, and this small pattern becomes an SBD. Since the guard ring region is formed in the same pattern as shown in FIG.

[Brief explanation of drawings]

FIGS. 1(a) to (") are process sectional views showing a first embodiment of the present invention, FIGS. 2(a) to (h) are process sectional views showing a second embodiment of the present invention, FIG. 3(a) to ("・) are cross-sectional views of conventional processes. 101.201,301...Silicon substrate, 1
02.202,302...Oxide film, 103°2
03.303...Silicon oxide film, 104°2
04...Silicon oxide film, 105,205°2
13.305,313...Photoresist film,
106.206,306...Selective oxide film, 1
07゜207.307・・・Guard ring area, 1
08°208.208', 308...Platinum silicide layer, 109.209,209', 309...
...Titanium/tungsten thin film, 110,210,
210'310... Aluminum thin film, 211
, 212... Oxide film, 214... Base region, 215... Emitter region. Agent Patent Attorney Susumu Uchihara Cbno CC) Figure (e) Figure 7 Figure 2 Figure 3 Figure 2 Third Leap

Claims (1)

[Claims] A step of laminating and forming a first insulating film including an oxidation-resistant film and a second insulating film on the surface of a semiconductor substrate of a first conductivity type, and selectively forming a mask film on the second insulating film. using the mask film, etching the second insulating film into a shape smaller than that of the mask film, and forming the oxidation-resistant film into a shape substantially the same as the mask film; a step of etching, a step of oxidizing the surface of the semiconductor substrate using the oxidation-resistant film as a mask to selectively form an oxide film, and a step of etching the selectively formed oxide film and the second insulating film. forming an impurity region of a second conductivity type in the semiconductor substrate in a self-aligned manner through a gap between the semiconductor substrate and the semiconductor substrate; exposing at least a region of the semiconductor substrate surrounded by the impurity region; 1. A method for manufacturing a semiconductor device, comprising a step of forming a metal layer through a metal layer or an alloy layer.