JPS63211755A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a semiconductor device having a Schottky diode, whose leaking current is small, by providing a hole for a guard ring region for the Schottky diode at the same time when a collector contact hole is formed, diffusing impurities from the upper part of etched silicon, forming a guard ring layer, and exposing the surface of an epitaxial layer surrounded with said layer. CONSTITUTION:After a P-type polycrystalline silicon is removed, boron is implanted, and a P-type polycrystalline silicon layer 208B is formed. Then a nitride film 211 is formed. Boron is diffused in an epitaxial layer 103 by heat treatment. A guard ring 210 for a Schottky diode is formed around an oxide film. Then silicon on the nitride film and a Schottky-junction forming region is removed. An oxide film 105 on the Schottky-junction forming region is exposed. After a CVD silicon oxide film is grown, the oxide film 105 on a contact region and the Schottky-junction forming region is removed. The surface of the epitaxial layer surrounded with the guard ring 210 is exposed. Thereafter, a platinum silicide layer 126 is formed, and the Schottky junction is formed.

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 semiconductor device that integrally includes a bipolar transistor, a Schottky diode element, and the like.

[Conventional technology]

In response to the demand for higher performance of bipolar transistors, in recent years a manufacturing method using polycrystalline silicon and forming emitter and base electrodes separated by self-alignment lines has come into widespread use.

like this! When trying to form a semiconductor device with improved circuit performance by mixing a Schottky diode with a guard ring with an R-type bipolar transistor, conventionally, as shown in Figure 3(a), the P-type After forming an N+ type buried collector 1.02 of a transistor on a silicon substrate 101, an N type epitaxial layer 10 is formed.
3 is grown to form silicon oxide films 104 and 105, and an opening is formed in the silicon oxide film 105 at the same time as an opening in a part of the collector of the piebola transistor, and also in a region where a Schottky junction is to be formed. By depositing a crystalline silicon film and selectively oxidizing this polycrystalline silicon film, the electrodes of the bipolar transistor, that is, the collector polycrystalline silicon 308A and the base polycrystalline silicon 308B, are separated, and at the same time, silicon oxide is formed in the opening. A film pattern 311B is formed.

Next, as shown in FIG. 3(b), by diffusing impurities into the N-type epitaxial layer 103 through the polycrystalline silicon, a P-type guard ring layer 316 is formed in the region surrounding the silicon oxide film pattern 311B. By forming and removing the silicon oxide film 311B, an N-type epitaxial layer 103 surrounded by a P-type guard ring layer is formed.
The surface was exposed and metal was deposited on it to form a Schottky junction.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, an opening is provided in the insulating film over the area where the Schottky junction is to be formed, and the polycrystalline silicon grown on the exposed N-type epitaxial layer is directly selectively oxidized. Oxidation also tends to progress in the N-type epitaxial layer, which tends to induce crystal defects on the Schottky junction forming surface. As a result, the Schottky diode has the disadvantage of generating leakage current.

In addition, selectively oxidized polysilicon layers are sometimes used as resistors by optimizing the concentration of impurities added, but the oxide film digs into the resistor mask pattern (so-called bird's beaks), resulting in poor mask dimensions and finished product. There will be a difference between the dimensions.

For this reason, there is a drawback that this pattern conversion difference must be taken into consideration in advance in mask design. Furthermore,
The variation in the pattern conversion difference is a major factor in the variation in polysilicon resistance value.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device having a Schottky diode that eliminates the above drawbacks and has a low leakage current.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes the steps of forming an insulating film on a first conductivity type semiconductor substrate, and then forming openings at predetermined positions including the periphery of a region where a Schottky junction is to be formed; Depositing a polycrystalline silicon film and selectively etching the polycrystalline silicon film to leave the polycrystalline silicon film at least on the opening, and forming a second conductivity type film through the polycrystalline silicon film. forming a second conductivity type guard ring layer in the semiconductor substrate by diffusing impurities; and removing an insulating film surrounded by the guard ring layer to expose a part of the semiconductor substrate. , and forming a Schottky junction by depositing metal on the exposed portion of the semiconductor substrate.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A to 1J are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1(a), a P-type silicon substrate 1
01, selectively forming an N1 type embedded collector 102,
Furthermore, a lightly doped N-type epitaxial layer 103 is grown to a thickness of 1 to 2 μm on the region including this N+ type buried collector 102.

Next, element regions are separated by forming a silicon oxide film 104 by selective oxidation.

Thereafter, the surface of the epitaxial layer M103 is exposed, and then a silicon oxide film 105 is formed to a thickness of 2,000 to 2,500 nm. Next, by selectively etching and removing the silicon oxide film 105, a transistor collector electrode formation region 106 and a Schottky diode guard ring formation region 107 are formed on the surface of the N-type epitaxial layer 103.

Next, as shown in FIG. 1(b), a first polycrystalline silicon film is grown over the entire surface to a thickness of 2,000 to 5,000 wafers.

Next, after separating each electrode by selective etching,
Phosphorus is diffused into the collector polycrystalline silicon electrode 108A, boron is introduced into the base electrode polycrystalline silicon 108B, and heat treatment is performed to diffuse boron into the N-type epitaxial layer to form a guard ring 110.

Next, as shown in FIG. 1(C), the silicon nitride film 11
After growing 1,000 to 2,000 people on the entire surface,
Using a mask 112 made of photoresist, the silicon nitride film in the emitter formation region of the transistor and the polycrystalline silicon underneath are sequentially anisotropically etched to expose the surface of the silicon oxide film 105 on the emitter formation region.

Next, as shown in FIG. 1(d), the mask 112 is removed and a silicon nitride film 113 with a thickness of 100% is deposited on the entire surface by CVD.
The silicon nitride film 113 is grown to a thickness of 0 to 2000 nm, and then anisotropically etched by RIE, leaving the silicon nitride film 113 only on the side surfaces of the opening of the base electrode polycrystalline silicon 108B. let At this time, silicon nitride films 113 and 111 are integrated.

Next, the exposed silicon oxide film 105 is removed using buffered hydrofluoric acid. At this time, the silicon oxide film 10
5 is 3000~50 to the bottom of polycrystalline silicon 108B
00 people side etched and undercut.

Next, as shown in FIG. 1(e), a second polycrystalline silicon film is grown to a thickness of 20 to 4000 nm to backfill the undercut portion and form a polycrystalline silicon film 108B for the base electrode. The boron contained in the base electrode polycrystalline silicon 108B is removed from the second polycrystalline silicon and the N-type epitaxial layer 10 by heat treatment at 900°C.
3 to form the graft base 115 of the transistor.

Next, by utilizing the difference in etching speed of the polycrystalline silicon film due to the difference in boron concentration, selective etching is performed so that the second polycrystalline silicon remains only in the backfilled portion of the undercut. Subsequently, the exposed side surfaces of the second polycrystalline silicon 114 and the surface of the N-side epitaxial layer 103 are oxidized to form a silicon oxide film 116 with a thickness of about 1000 wafers.

Next, boron ions are implanted at a dose of 1.0 to 5.0×101 to form a P-type active base 117. At this time, since the Schottky junction forming region is masked with the silicon oxide film 105, boron is not implanted.

Next, as shown in FIG. 1(f), a silicon nitride film 118 is grown on the entire surface by CVD to a thickness of 1000 to 2000 nm, and then this silicon nitride film is anisotropically etched by RIE. By doing so, the silicon nitride film 118 is left only on the side surfaces of the groove-shaped portion. Furthermore, by etching and removing the silicon oxide film 116 at the bottom of the emitter formation region, a part of the surface of the active base layer 117 is exposed.

Next, the third polycrystalline silicon 119 is
It grows to a thickness of 0,000 ml, and then the whole surface is coated with arsenic 5. θ~10
Ion implantation is performed at a dose of 15 to 1.0×10 16 CI 11-2. Then, arsenic is diffused by heat treatment at 900 to 950° C. to form an N-type emitter 120 in the P-type active base 117, thereby forming a transistor. At this time, the silicon nitride film 111 serves as a mask in the Schottky junction formation region, and arsenic is not diffused. Also, emitter 120
and the graft base 115 are connected to the silicon nitride film 118.
Since the distance is secured with good controllability, parasitic base resistance can be reduced without causing a drop in breakdown voltage due to contact between highly concentrated regions of opposite conductivity type, making it possible to form high-performance transistors. .

Next, as shown in FIG. 1(g), the third polycrystalline silicon 119 into which arsenic ions have been implanted is selectively removed to form an emitter electrode 119A. Next, the silicon nitride film 111 is selectively removed by RIE using a mask 121 made of photoresist, thereby removing the polycrystalline silicon on the Schottky junction forming region and the collector polycrystalline silicon electrode 108A, as well as the base (not shown) and the collector polycrystalline silicon electrode 108A. Expose the polycrystalline silicon surface of the resistor, etc.

Next, as shown in FIG. 1(h), after removing the mask 121, a mask 122 made of photoresist with holes only in the Schottky junction forming area is formed, and The crystalline silicon is removed by RIE using the mask 122 and the silicon nitride film 111 to expose the silicon oxide film 105.

Next, as shown in FIG. 1(i), after removing the mask 122, silicon oxide 123 is deposited at 2000 to 30% by CVD method.
The silicon oxide film 10 is grown on the Schottky junction formation region to form various contacts such as an emitter, collector, Schottky junction, and base and resistor (not shown).
5 is completely removed and the surface of the N-type epitaxial layer 103 is exposed by etching by RIE. This exposes the surface of the N-type epitaxial layer and one end of the guard ring 110, and at the same time exposes the emitter electrode 119A and the collector polycrystalline silicon electrode 1.
08A surface is exposed.

Next, as shown in FIG. 1 (j>), a Schottky material such as platinum is deposited on the entire surface by sputtering to a thickness of 300 to 800 mm, and further heat-treated to form platinum silicide 126. Form a bond.At this time,
Platinum silicide is also formed in other contact portions. Thereafter, an aluminum electrode 127 is formed by a normal method to complete the semiconductor device.

In this way, in this example, in the process of forming a high-performance bipolar transistor in which the emitter and base electrodes are formed in a self-aligned manner using polycrystalline silicon, a shot having a gert ring formed in a self-aligned manner is used. When forming the key diode, there is no need to form a thick polycrystalline silicon oxide film as in the conventional method, and there is no need to oxidize the surface of the N-type epitaxial layer in the Schottky junction forming region. As a result, crystal defects are not induced near the surface of the N-type epitaxial layer, making it possible to manufacture a high-quality semiconductor device in which the leakage current of the Schottky diode is extremely small.

In addition, in the structure of a semiconductor device in which a transistor and a Schottky diode are integrated as in Example 1, and a polycrystalline silicon film is connected to a graft base and a guard ring, respectively, the Schottky diode is clamped. It can be easily used as a diode.

FIGS. 2(a) to 2(C) are cross-sectional views of a semiconductor chip shown in order of steps for explaining a second embodiment of the present invention.

First, as shown in Figure 2 (a), after selectively etching away the P-type polycrystalline silicon, boron ions are implanted.
For example, polycrystalline silicon 208B having a layer resistance of 5 to 1 Ω/hole is formed by ion-implanting boron at a dose of 1.0 to 5.0×10 ” cm −2 .

Next, as shown in FIG. 2(b), the silicon nitride film 2'
Epitaxial layer 1 is grown from polycrystalline silicon 208B by growing 11 and performing heat treatment at 900 to 1000°C.
Boron is diffused into the silicon oxide film to form a guard ring 210 of a Schottky diode around the silicon oxide film.

Thereafter, the silicon nitride film and the polycrystalline silicon on the Schottky junction forming region are removed by photoresist treatment and RIE treatment twice, as shown in FIG. 1 (g>(h)) of the first embodiment described above. Then, the silicon oxide film 105 on the Schottky junction formation region is exposed.

Subsequently, as shown in FIG. 2(C), after growing the CVD silicon oxide film, the silicon oxide film 105 on the resistor contact region and the Schottky junction formation region is selectively removed by RIE, and a P-type guard is formed. The surface of the N-type epitaxial layer surrounded by ring 210 is exposed. After that, a Schottky material such as platinum is sputter-formed to a thickness of 300 to 800 mm, and then heat-treated to form platinum silicide 12.
6 to form a Schottky junction. Thereafter, an aluminum electrode 127 is formed by a normal method to complete the semiconductor device.

In this second embodiment, since the guard ring of the Schottky diode is formed at the same time as the impurity introduction for forming the polycrystalline silicon resistive element, a semiconductor device in which the Schottky diode and the polycrystalline silicon resistive element are integrated can be manufactured. It has the advantage of being easy to form.

〔Effect of the invention〕

As explained above, the present invention provides a semiconductor device in which the emitter and base of a bipolar transistor are formed in a self-aligned manner using a polycrystalline silicon film, and a Schottky diode with a guard ring is also formed in a self-aligned manner.
Instead of using selective oxidation technology for polycrystalline silicon, which causes Schottky diode leakage, when opening the collector contact, the guard ring region of the Schottky diode is also opened at the same time, and impurities are removed from the selectively etched polycrystalline silicon. After forming a guard ring layer by diffusion, the surface of the epitaxial layer surrounded by the guard ring layer is exposed to form a Schottky diode, which prevents crystal defects from being induced in the epitaxial layer by selective oxidation of polycrystalline silicon. do not have. As a result, the Schottky diode has low leakage current and can maintain high quality.

In addition, since the first polycrystalline silicon film according to the present invention can be patterned with high precision by RIE, it is possible to pattern the first polycrystalline silicon film with high precision without considering the oxidation depth when selectively oxidizing polycrystalline silicon as in the past. , which is advantageous for high integration of semiconductor devices. Furthermore, when a polycrystalline silicon film is used as a resistor, selective etching by RIE reduces variation in resistance width compared to variation in dig-in width by selective oxidation, which improves the absolute accuracy of polycrystalline silicon resistors. I can do it.

[Brief explanation of the drawing]

FIGS. 1(a) to (j) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining the first embodiment of the present invention, and FIGS. 2(a) to (C) are cross-sectional views of a semiconductor chip according to the second embodiment of the present invention. FIG. 3(a) is a cross-sectional view of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.
-(b) are cross-sectional views for explaining a conventional method of manufacturing a semiconductor device. 101... P-type silicon substrate, 102... N-type buried collector, 103... N-type epitaxial layer, 104
．． 105,116,123,309,311...Silicon oxide film, 111,113,118°211.315
...Silicon nitride film, 108, 114.119, 20
8,308...polycrystalline silicon, 112.121,1
22,124...Mask, 110.210,316.
... Guard ring, 115,320 ... Graft base, 117,322 ... Active base, 120,325
...Emitter, 126...Platinum silicide, 127
...Aluminum electrode. j'' song.

Claims (1)

[Claims] After forming an insulating film on the first conductivity type semiconductor substrate, a process of forming openings at predetermined positions including the periphery of the Schottky junction formation area, and a process of forming a polycrystalline silicon film on the entire surface and then selectively etching to leave a polycrystalline silicon film at least on the opening, and diffusing a second conductivity type impurity through the polycrystalline silicon film to form a second conductivity type guard ring layer in the semiconductor substrate. a step of removing the insulating film surrounded by the guard ring layer to expose a part of the semiconductor substrate; and a step of depositing metal on the exposed portion of the semiconductor substrate to form a Schottky junction. A method for manufacturing a semiconductor device, comprising: