JPS6355954A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve electric withstanding voltage and reliability of a P-N junction, by etching a P-N junction forming region at a desired depth with an insulating oxide film as a mask, and thereafter forming the P-N junction. CONSTITUTION:The upper part of a P-type impurity region in a semiconductor substrate 100 is oxidized, to form an oxide film 120. Thereafter a silicon nitride film 130 is deposited. Then, a resist pattern 140 covering a junction forming region is formed. With the pattern 140 as a mask, the nitride film 130 is removed to form a silicon nitride film pattern 130a. With the pattern 130a as a mask, selective oxidation is performed, and oxide films 150a and 150b are formed. Then, the pattern 130a and the film 120 are removed to form a hole on the junction forming region. After the semiconductor substrate surface is exposed, an etching part 10 is formed by isotropic etching with the films 150a and 150b as masks. Then, polysilicon 160 is deposited and N-type impurities are implanted. An N-type impurity region 170 is formed by heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing semiconductor devices, and in particular to a manufacturing method that improves electrical resistance in element isolation of PN junctions separated by the LOCO5 method in integrated circuits, etc. This is related.

BACKGROUND OF THE INVENTION Normally, in order to obtain insulation isolation of a PN junction in a semiconductor device, for example, electrical insulation between a base region and an emitter region of a transistor in a bipolar IC, the periphery of an active region in a semiconductor substrate is selectively oxidized by the LOCO5 method. ,
For example, as shown in FIG.
An oxidation-resistant mask such as a silicon nitride film is left on the P-type region 210 above 0, and selective oxidation is performed. ! Oxide film region 25
After forming 0a and 250b, the oxidation-resistant mask is removed to form an N-type region 270 in the opening, and a conductive material 260e such as low-resistance polysilicon is deposited to cover the N-type region 270.

Problems to be Solved by the Invention In the insulation isolation of a general PN junction as shown in FIG. The film quality is easily deteriorated by the stress during oxidation, and during processing such as cleaning and etching, the tips 280a and 280b of the insulating oxide film region retreat as shown in Figure (b), causing a short circuit in the PN junction. As shown in Figure 2(c), there are unstable factors such as a high occurrence rate of pinholes 290, etc., and for this reason, when a voltage such as a surge is applied to the PN junction, the insulation oxidation pA Territory area tip 280a
, 280b tends to cause dielectric breakdown. On the other hand, as elements become smaller, it becomes necessary to reduce the depth of the junction. Therefore, the tips 280a, 280 of the insulating oxide film region
When using b for insulation separation of PN junctions, the frequency of short-circuit failures increases, reducing product yield and reliability.

The present invention solves these problems by forming the PN junction by recessing it from the tip of the insulating oxide film region, and
The present invention provides a method for manufacturing a semiconductor device that improves the electrical resistance and reliability of a junction.

Means to Solve the Problem In order to solve this problem, the present invention provides a step of forming an oxidation-resistant first mask material on the main surface of a semiconductor substrate of a first conductivity type; selectively leaving the oxidation-resistant first mask material pattern on a region where a bond is to be formed; and selectively oxidizing using the oxidation-resistant first mask material pattern as a mask. g! etching the junction formation region to a desired depth using the oxide film as a mask; forming a second conductivity type semiconductor region in the junction formation region; Steps of forming a conductive material covering the semiconductor region of the second conductivity type;
- A method for manufacturing a semiconductor device is provided.

Effect: By this method, 48! l In order to remove the instability factor at the tip of the oxide film region, in order to retreat the PN junction from the tip of the insulating oxide film, the PN junction planned to be formed @H is etched to a desired depth using this insulating oxide gap as a mask. Then, P
By forming the N junction, it is possible to achieve good insulation isolation of the PN junction, and to provide a semiconductor device with high noise and high reliability.

Examples Below, examples of the manufacturing method of the present invention are shown in Figure 1 (
The explanation will be based on a) to (e).

(1) First, the P-type lower It region in the semiconductor substrate 100 was oxidized to form about 20 OA of JIQ 120, and then about 40 OA of silicon nitride a 130 was deposited.

(2) Next, a resist pattern 140 was formed to cover the region where a junction was to be formed by a first photomask process [FIG. 1(&)].

(3) Next, the silicon nitride jQ 130 was removed as a resist pattern 1407 mask to form a silicon nitride interlayer pattern 130a [FIG. 1(b)].

(4) Next, the silicon nitride film pattern 130♂ is selectively oxidized using a mask to oxidize JE1 to approximately 1OOOA.
150a.

+50b t-formed. [1st fM(c)] (5) Next, silicon nitride MJ pattern 130a and oxidation 7
1120e After removing by wet etching or the like and forming an opening on the junction formation area to expose the semiconductor substrate surface, oxidized pHQ 150a, 150b is masked',
Then, the surface of the semiconductor substrate in the area where a junction is to be formed is etched by about 1000A by isotropic etching such as dry etching to form an etched portion 10f [see Fig. 1(d)].
) ].

(6) Next, polysilicon 160 of about 3000 A was deposited on the semiconductor substrate surface.

(7) Next, after ion-implanting N-type impurities into the polysilicon 160, heat treatment was performed to form an N-type element II4 region 170 in the region where a junction was to be formed [FIG. 1(e)].

Through the above series of steps, a desired PNIQ composite was formed.

However, as another preferable manufacturing method, the WH oxidizing layer formed in step (1) can be formed not only from the above-mentioned multilayer film of the oxide film and silicon nitride film, but also from a single layer film such as a silicon nitride film. can. In addition to the above-mentioned polysilicon, a metal film such as aluminum or a compound of silicon and metal may be used as the conductive film formed in step (6).

Effects of the Invention By the manufacturing method according to the present invention, the instability factor at the tip of the Ae edge oxide region is removed, and when a voltage such as a surge is applied to the PN junction, the occurrence of short circuit failure due to dielectric breakdown is reduced. The electrical resistance of the PN junction can be improved, making it possible to provide semiconductor devices with high yield and high reliability.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are process cross-sectional views showing a manufacturing method according to an embodiment of the present invention, and FIGS. 2(a) to (C) are cross-sectional views showing a conventional example. 100, 200... semiconductor substrate, 110, 220...
・P-type impurity region, 120... oxide film, 130...
Silicon nitride film, 140...Resist pattern, 15
0,250...Oxide film, 160°260...Polysilicon, 170.270...N type impurity region, 280
. . . tip of insulating oxide film region, 290 . . . pinhole. Name of agent Patent attorney Toshio Nakao One idiot Figure 1 Figure 1 (C) Figure 12

Claims (1)

[Claims] forming an oxidation-resistant first mask material on a main surface of a first conductivity type semiconductor substrate; and selecting a pattern of the oxidation-resistant first mask material on a region of the semiconductor substrate where a bond is to be formed; a step of selectively oxidizing and forming an oxide film using the oxidation-resistant first mask material pattern as a mask; and a step of forming an oxide film in the region where the junction is to be formed using the oxide film as a mask. A method for manufacturing a semiconductor device, the method comprising: etching in the junction formation region; forming a second conductivity type semiconductor region in the junction formation region; and forming a conductive material covering the second conductivity type semiconductor region. .