JPS6185838A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the insulating isolation oxide films from encroaching into the element region and to prevent the generation of protrusion on the boundaries between the insulating isolation oxide films and the element region by a method wherein grooves for isolation, which reach in the semiconductor substrate in a self-alignment manner, are formed between the element region and the insulating regions and a silicon nitride film is buried in the grooves. CONSTITUTION:An oxidation is performed selectively on the surface of an n-type epitaxial layer 202, and silicon oxide films 205 are formed. A side etching is performed on a silicon nitride film 203 using heat phosphoric acid and so forth to reduce the pattern in a self-alignment manner. Subsequently, a silicon oxide film 204 is removed using hydrofluoric water solution. An etching is performed on the epitaxial layer 202 by an ion-etching technique using the silicon nitride film 203 and the silicon oxide films 205 as masks to form grooves 207. Then, the silicon oxide films 205 are removed using hydrofluoric solution. Subsequently, a silicon nitride film 208 is formed on the whole surface and parts of the silicon nitride film 208 are removed by an ion-etching technique. Epitaxial layers 202B other than the epitaxial layer 202B on an element region 202A are converted into silicon oxide films 209 by performing a thermal oxida tion and the insulating isolation film 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 is an improved method for insulating and isolating element regions.

[Conventional technology]

Conventionally, various methods for isolating elements in a semiconductor device have been proposed because they are directly related to the integration density and performance of the semiconductor device. A typical method is a method called the isoplanar method or LOCO8 method, which performs insulation isolation using an oxide.

FIGS. 4A and 4B are cross-sectional views of the main steps of a semiconductor device for explaining this oxide separation method.

First, as shown in FIG. 4 la, N-type epitaxial Ji 102 is grown on a P-type substrate 101 . Next, a silicon nitride film 103 is formed, and the silicon nitride film 103 outside the element region is removed, and then the epitaxial layer 102 is etched to about 1/2 the thickness.

Then, by oxidizing this as shown in FIG. 1BL, an oxide film 104 is formed, thereby forming an element region 105t which is insulated and isolated by the oxide 104.

[Problem that the invention seeks to solve]

However, in this conventional method, oxidation J[1
04 grows not only in the depth direction but also in the lateral direction from the surface, a depression 106 called a bird's beak in the element region 105 and a protrusion 107 called a bird's head are generated at the boundary between the silicon nitride film 103. All of these are unfavorable for increasing the density and multilayering of elements, and reducing this is one of the challenges.

Therefore, an object of the present invention is to solve these problems of the prior art, thereby making it possible to obtain a semiconductor substrate with a flat surface without the oxide film for insulation isolation digging into the element region. An object of the present invention is to provide a method for manufacturing a semiconductor device.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes forming a two-layer pattern consisting of a first silicon nitride film and a first silicon oxide film in an element formation region on a semiconductor substrate, and using the pattern as a mask for oxidation. a step of selectively forming a second silicon oxide film by etching the first silicon nitride film using the first silicon oxide film as a mask; 1st
a step of forming a groove of a predetermined depth by etching the semiconductor substrate using the second silicon oxide film and the first silicon nitride film as a mask; The method includes a step of embedding a second silicon nitride film in the trench, and a step of selectively oxidizing the semiconductor substrate using the first and second silicon nitride films as masks.

[Effect]

The present invention forms an isolation NT shadow on a semiconductor substrate between an element region and an insulating region using a self-line, and buries a silicon nitride film, which is an oxidation-resistant film, in this isolation groove. This is a method of manufacturing a semiconductor device in which a silicon nitride film is deposited on a silicon nitride film, followed by thermal oxidation to form an oxide film in an insulating region, thereby separating element regions with an oxide film.

Therefore, in the present invention, in order to perform oxidation for insulation isolation while the oxidation-resistant silicon nitride film is also formed on the side surfaces of the element region, the insulation isolation oxide film is prevented from penetrating into the element region. Also, protrusions at the boundary with the element region can be prevented.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1bl-Ig) are cross-sectional views of the main steps of a semiconductor device for explaining an embodiment of the present invention, showing a case where an island region in which a bipolar element is formed is formed by insulation isolation.

First, as shown in FIG. 1, an N-type epitaxial layer 202tl- is grown on a P-type silicon substrate 201 to form a semiconductor substrate. Next, a silicon nitride film 2 is applied to this surface.
A silicon oxide film 204t-204t is grown to a thickness of about 1,000 to a zero thickness, and then a silicon oxide film 204t-204t is formed to a thickness of about 0 to 2,000 by vapor phase growth. Next, the silicon oxide film 204 outside the element area
and the silicon nitride film 203k are removed by ordinary photolithography.

Next, as shown in FIG. 1 (bl), the silicon nitride film 203
Then, using the silicon oxide film 204 as a mask, the surface of the epitaxial layer 2020 is selectively oxidized to form a silicon oxide film 205t''.
5 is formed to be sufficiently thicker than the silicon oxide film 204 formed by vapor phase growth.

Next, as shown in FIG. 1(e), a silicon nitride film 203
Perform side etching with hot phosphoric acid or the like to shrink the pattern in a self-aligned manner. Approximately 30,000 side etches are performed. Subsequently, the silicon oxide film 204 is removed using a hydrofluoric acid-based aqueous solution or the like. At this time, the silicon oxide film 20
Although the surface of 5 is etched by the mold blade, the silicon oxide film 2
It remains because it is thicker than 04. This silicon oxide film 20
5 and the reduced silicon nitride film 203, an exposed portion 206 is formed on a part of the surface of the epitaxial layer 2020. As shown in FIG. Using the film 205 as a mask, the epitaxial layer 202 is etched using ion etching technology to form a groove 207. In this case, by using ion etching technology, silicon etching can be performed only in the vertical direction without spreading in the lateral direction. The depth of the groove is set to be equal to or greater than the film thickness of the epitaxial i 202.

Next, as shown in FIG. 1+61, 1 silicon oxide film 205
is removed with a hydrofluoric acid solution. Subsequently, silicon nitride is formed on the entire surface to a thickness of about 1500 t'.

In this case, it also adheres to the groove 207 and fills it up.

Next, as shown in FIG. 1(f)K, in the silicon oxide film etching method using ion etching technology, since etching progresses only in the direction perpendicular to the substrate, the silicon nitride film 208A buried in the trench 207 remains. do. Moreover, since the silicon nitride films 203 and 208 are double layered and thick on the element region 202A, the silicon nitride film 203 remains due to the difference in film thickness. In this way, the element region 202A has a shape in which the top and side surfaces are surrounded by the silicon nitride films 203 and 208A.

Next, as illustrated in FIG. In this case, the silicon nitride film 208 serves as an oxidation-resistant mask, and a flat isolation region is formed without causing any digging.

FIG. 2 is a sectional view showing an example of a bipolar transistor manufactured by the method of the present invention.

In FIG. 2, an N+ type buried layer 302 and a P type inversion prevention layer 303 are formed on a P type silicon substrate 301 to reduce collector resistance. Silicon substrate 301
A bipolar transistor insulated and isolated by a silicon oxide film 304 and a silicon nitride film 305 is formed thereon by the method of the present invention. Bipolar transistors are formed using well-known techniques. A collector lead-out layer 307 , a P-type base region 308 , and an N1-type emitter region 309 are formed in the N-type epitaxial layer 306 , and each region is drawn out to the outside by an electrode 310 .

As is clear from FIG. 2, the oxide film 304 for insulation isolation
is formed without digging into the element region, making it possible to form the element region with good dimensional accuracy and to form a flat semiconductor surface.

FIG. 3 is a sectional view showing an example of a polycrystalline silicon resistor manufactured by the method of the present invention.

In FIG. 3, a polycrystalline silicon resistor 404 is insulated and isolated by a silicon oxide film 402 and a silicon nitride film 403, which are formed by oxidizing a polycrystalline silicon film on an insulating film 401 by the method of the present invention. It is formed. The resistance value of υ is controlled by doping the polycrystalline silicon resistor 404 with a predetermined impurity. Further, connections to other elements and connections to the outside are formed by metal wiring 405.

As is clear from FIG. 4, the polycrystalline silicon resistor 4
04 is a silicon oxide film 4 covered with a silicon nitride film 403 and formed by oxidizing a polycrystalline silicon film.
Since it is formed faithfully to the mask without digging into the resistor element 02, it is a highly accurate resistor element.

〔Effect of the invention〕

As described above in detail, the semiconductor device manufacturing method of the present invention can suppress the occurrence of bird's beak in the oxide film of the insulation film isolation by the above means, so that the element region can be formed with high dimensional accuracy. It has the effect of improving the performance and miniaturization of devices. In addition, since the semiconductor surface can be formed flat while suppressing the occurrence of bird's beaks, multi-layering can be easily achieved and breakage in the upper layer can be prevented, which has the effect of increasing the reliability of the device. .

Therefore, according to the present invention, it is possible to obtain a semiconductor device with higher performance, higher density, and higher reliability, and its effects are significant.

[Brief explanation of drawings]

1al to 1al-(gl is a cross-sectional view of the main steps of a semiconductor device for explaining an embodiment of the present invention, and FIGS. 2 and 3 are an example of a bipolar transistor manufactured by the method of the present invention, and A cross-sectional view showing an example of a polycrystalline silicon resistor, FIG. P-o silicon substrate, 202, 202
B...N-type epitaxial layer, 202A...
...Element region (N-type epitaxial layer), 203...
...Silicon nitride film, 204.205...
Silicon oxide film, 206...Exposed portion, 207.
...Groove, 208...Silicon nitride film, 2
09...Silicon oxide film, 301...
P type silicon substrate, 302... N+ type buried layer, 303... Inversion prevention layer (P type), 304...
...Silicon oxide film, 305...Silicon nitride film, 306...N-type epitaxial layer, 3
07... Collector drawer layer, 308...
-P type base region, 309...N+ type emitter region, 310...electrode, 401...insulating film, 402...silicon oxide film, 403...・
... Silicon nitride film, 404 ... Polycrystalline silicon crystal, 405 ... Metal wiring. Agent Patent Attorney Susumu Uchihara, - 2C/ Pju' Shirifun Ball JJumi 01 z, r/ Mayuzumi 1 Bmine 2 Gaku

Claims (1)

[Claims] A two-layer pattern consisting of a first silicon nitride film and a first silicon oxide film is formed in an element formation region on a semiconductor substrate, and oxidation is performed using the pattern as a mask to selectively form a second silicon oxide film. etching the first silicon nitride film using the first silicon oxide film as a mask to reduce it in a self-aligned manner, and then removing the first silicon oxide film; forming a groove of a predetermined depth by etching the semiconductor substrate using a second silicon oxide film and the first silicon nitride film as a mask; and filling the groove with a second silicon nitride film. and selectively oxidizing the semiconductor substrate using the first and second silicon nitride films as masks.