JPS5951545A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a crystal defect generated when inter-element isolating insulating film is formed from crossing over the semiconductor island region, suppress increase of junction leaf current of semiconductor element formed in the semiconductor island region and enhance yield of element by setting the surface index of substrate to <110>. CONSTITUTION:After forming an isolating oxide film 102 on a p type silicon substrate 101 having surface index <110>, an n-p-n transistor is formed within the island region surrounded by the side surface of an isolating oxide film 102. Thereby, the inter-element isolation is carried out vertically, dislocation generated from the edge of isolating oxide film 102 runs vertically for the surface and does not cross the island region surrounded by the side surface of isolating oxide film. Therefore, a junction current is not increased by abnormal junction of impurity atoms in the area near the junction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device in which elements are isolated by an insulating film, and more particularly to a semiconductor device that prevents an increase in junction leakage current due to crystal defects and improves the yield of transistors. It is something.

Conventional configuration and its problems Isolation between elements using an insulating film is widely used as a very effective method for increasing the density of semiconductor integrated circuit devices. FIG. 1 is a process cross-sectional view of forming an insulating film isolation structure by a conventional selective oxidation method. Figure 1 (,) shows that after forming an oxide film 2 and a nitride film 3 on the surface of a silicon substrate 1, etching is performed, leaving the surface oxide film 2 and nitride film 3 in the area that is to be an island region for forming a semiconductor element. This is what was done. 1st
Figure 1(b) shows the isolation oxide film 4 formed by selective oxidation using the nitride film 3 as a mask, and Figure 1(c) shows the result after the surface oxide film 2 and nitride film 3 have been removed. It is.

Thereafter, a transistor is formed in the island region 5 surrounded by the isolation oxide film 4.

The isolation oxide film 4 formed by the second method has the disadvantage that the isolation region expands due to lateral oxidation (bird's beef), which prevents high density.

FIG. 2 is a sectional view illustrating the process of another embodiment in which the occurrence of bird's beef described above is suppressed.

FIG. 2(a) shows an exposed island region after vertically etching the silicon substrate 6, which will become a separation region, by reactive sputter etching in the structure shown in FIG. 1(a) of the first conventional example. An oxide film 7 and a nitride film 8 are formed on the side surfaces. In FIG. 2(b), an isolation oxide film 9 is then formed by selective oxidation, and the surface oxide film and nitride film are removed. Thereafter, a transistor is formed in the island region 10.

Although the isolation oxide film 9 formed by the above method has the advantage of suppressing the occurrence of bird's beef, it has the problem that stress in the silicon nitride film 8 induces a large number of crystal defects during selective oxidation. It is known that this adversely affects the electrical characteristics of semiconductor elements formed in region 10.

Such crystal defects can be reduced by setting the base oxide film/nitride film thickness ratio to an appropriate value and devising process heat treatment conditions, but if the structure of the silicon opening before selective oxidation is If the shape has a vertical angle as shown in Figure (d), extra stress will be applied to the silicon substrate due to the volume expansion of the silicon opening during selective oxidation, so it is impossible to completely eliminate the occurrence of crystal defects. Can not.

FIG. 3 shows another conventional example of a method for forming a pre-oxide film to eliminate stress during selective oxidation using a nitride film. FIG. 3(a) shows the island region 1 of the silicon substrate 11.
The separation region 13 is vertically etched using a reactive spanner etching method, leaving a hole. FIG. 3(b) shows an oxide film 13 deposited on the surface of a silicon substrate 110 by the CVD method. Silicon opening 13 in silicon substrate
The difference in oxide JIG! can be eliminated by depositing an oxide film 13. Human face 1. [・1 is flattened. In FIG. 3(C), the oxide film 13 is removed by etching only beyond its thickness, leaving the oxide film 14 in the isolation region 13. After that, a transistor is formed in the island region 12 by the above method. The isolation oxide film 14 vertically separates the island regions 12 and is therefore suitable for high density, and has the advantage that crystal defects are less likely to occur since the stress of the nitride film is not applied to the silicon substrate regardless of the selective oxidation method. However, the isolation oxide film 14 embedded in the isolation region 13 and the silicon substrate 11
Due to the difference in film quality between the two, it is inevitable that new crystal defects will occur during the various heat treatment processes used to form semiconductor devices.
As explained above, when elements are separated by an insulating film, especially when elements are separated vertically for higher density, crystals that are induced in the formation process Defects become an unavoidable problem and have a significant negative impact on the electrical characteristics of semiconductor devices formed in the island regions.

OBJECTS OF THE INVENTION The present invention prevents the crystal defects induced when forming the above-mentioned element isolation insulating film from crossing the semiconductor island region surrounded by the side surfaces of the isolation oxide film, and prevents crystal defects from being formed in the semiconductor island region. The present invention provides a semiconductor device which prevents an increase in the junction leaf current of a semiconductor element and improves the yield of the semiconductor element. 110) plane to prevent crystal defects induced during the formation of the element isolation oxide film from crossing within the island region.

Description of Examples The plane index of a silicon semiconductor substrate on which a semiconductor element is to be formed is (111) in a bipolar transistor.
(100) has been used in MOS) transistors. This is selected based on the good crystallinity in epitaxial growth in the former case, and the shield 9 of interfacial charge between silicon and silicon oxide film in the latter case.

-The crystal structure of a silicon single crystal is a diamond structure, and when shear stress is applied to the crystal, dislocations with the [111] plane as the slip plane and the (110) direction as the slip direction are induced. Figure 4(a).

(b) is a vertical insulation film using a conventional silicon substrate.
This figure shows how crystal defects (dislocations) occur when a separated structure is formed. Dislocations can be easily observed as etched bits by chemical etching.

FIG. 4(a) shows the appearance of dislocation etch pits 17 induced when an isolation oxide film 16 is formed in a silicon substrate 15 whose surface has a plane index of (111). (110)
The etch bits appearing in the cross section of the plane are parallel to the surface of the (111) plane and continue in the (110) direction. The stress is concentrated near the edges of the isolation oxide film 16, and the dislocations are generated near the edges of the isolation oxide film 16 and run across the island region 18. Therefore, when a semiconductor element is formed in the island region 18, impurity atoms undergo abnormal diffusion along the dislocations, causing an increase in the leaf current of the junction.

FIG. 4(b) shows the appearance of dislocation etch pits 20 induced when an isolation oxide film 19 is formed on a silicon substrate 18 whose surface has a plane index of (100). (111)
Etch pits that appear in the cross section of the surface are located at an angle of about 60° from the edge of the isolation oxide film 19 downward (1
10) Running in the direction. Dislocations diagonally cross the island region 21 and cause an increase in the junction leaf current of semiconductor elements formed in the island region.The present invention has been made in view of the above points, and the structure of the present invention will be described below. will be explained with drawings.

FIG. 5 is a sectional view showing an embodiment of the present invention. (1
10) After forming an isolation oxide film 102 on a P-type silicon substrate 101 with a planar index by a conventionally known method, an npn transistor is formed in an island region surrounded by the side surfaces of the isolation oxide film. . If the isolation between the elements is vertical, dislocations generated from the edges of the isolation oxide film 102 run in the direction perpendicular to the surface, and do not cross the quadruple island region from the side surface of the isolation oxide film. Therefore, the junction leaf current does not increase due to abnormal diffusion of impurity atoms near the junction. In FIG. 6, 103 is a P-type channel stopper, 1o4 is an n+ buried layer, 105 is an n-type collector layer, 1Q6 is an n+ collector contact, 107 is a P-type base layer, 108 is an n+ emitter layer, 1o9, 11Q are electrode isolation oxide films, and 111 to 113 are collector, emitter, and base electrodes, respectively.

As is clear from the above explanation, the present invention can reduce the effect of reducing the junction leaf current by 1 even in the inter-element wall 11 structure having bird's beef formed by the conventional selective oxidation υ.
．． One is that the above effect is particularly remarkable in #Ni structures where the element amount is vertically divided.

As described in detail, according to the present invention, by setting the plane index of a silicon semiconductor substrate on which a semiconductor element is to be formed to (110), an element isolation insulating film, especially vertical element isolation, can be formed. This system prevents crystal defects induced during the formation of an insulating film from crossing the semiconductor island region surrounded by the side surfaces of the isolation oxide film, and eliminates an increase in the junction leaf current of the semiconductor element formed within the semiconductor island region. , it is possible to provide a semiconductor device with improved yield of semiconductor elements.

[Brief explanation of drawings]

Figures 1(,) to (C) are process cross-sectional views showing a method for manufacturing an isolation oxide film by the conventional selective oxidation method, and Figures 2(,) to (b)
) is a process cross-sectional view of another conventional example showing a method for manufacturing a vertical isolation oxide film, and FIGS. Figure 4 (
a) and Φ) are cross-sectional views illustrating the distribution of dislocations induced when forming an isolation oxide film, and FIG. 5 is a cross-sectional view showing a semiconductor device according to an embodiment of the present invention. Silicon semiconductor substrate, 102...separation oxidation 111.
'3,. 103...Dislocation etch pit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 2 Figure 3 Figure 12 14 Figure 4

Claims (2)

[Claims] (1) A silicon semiconductor substrate having a (110) plane index, and an isolation region in which elements are separated by an isolation insulating film formed in the silicon semiconductor substrate, and functional elements are formed in the isolation region. A semiconductor device characterized by: (2) The surface of the Sakai 1 insulating film is 7 silicon]',
, is perpendicular to the surface of the substrate.