JPS62106620A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent any induced defective crystal as well as any pollution in drive-in process from occurring by a method wherein ion is implanted through a silicon nitride film to be well-forming heat-treated while the silicon nitride film is used for LOCOS process. CONSTITUTION:A silicon oxide film 2, a silicon nitride film 3 are formed on an N-type silicon substrate 1. First, alignment patterns for lithography in the next process are formed by selectively etching silicon nitride film 3 as shown in A. Second, an ion implantation preventing region is formed of resist 4 by photolithography to be boron ion implanted. Third, the resist 4 is removed to drive-in P well with the silicon nitride film 3 is formed as it is. Finally the silicon nitride film 3 is selectively removed to oxidize the removed region forming an LOCOS oxide film 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a well.

2. Description of the Related Art Conventionally, the process flow shown in FIG. 2 is generally used for well structures used in OMO3 and well-type solid-state imaging devices. The manufacturing method will be briefly described below. First, as shown in FIG. 2(a), a thick silicon oxide film 7 is formed on the surface of an N-type silicon substrate 21, and a portion thereof is selectively removed. Next, after forming a protective oxide film 8 for ion implantation, boron ions are implanted over the entire surface (FIG. 2(b)).

Then, when heat treatment is performed to form the P-type well 26, the P-type well 26 is selectively formed as shown in FIG. 2(C). Then, after completely removing the thick silicon oxide film 7 and protective oxide film 8, a silicon oxide film 22 and a silicon nitride film 23 are grown (see FIG. 2).
d)). Then, in order to form an isolation region, after selectively removing the silicon nitride film 23, an oxidation treatment is performed to form a LOCO8 oxide film 26 as shown in FIG. .

Problems to be Solved by the Invention In such conventional methods, since a thick oxide film is formed also in the active region, there is a problem in that crystal defects are easily induced. The present invention is intended to solve these problems, and aims to suppress the occurrence of crystal defects and shorten the process.

Means for Solving the Problem In order to solve this problem, the present invention performs ion implantation through the silicon nitride film, and directly performs a well forming heat treatment to form the silicon nitride film.
This is used in the OCO3 process.

Effect: With this method, a thick oxide film is never formed on the active region, so crystal defects are not induced.
Moreover, contamination during the well forming heat treatment is also prevented by the silicon nitride film.

Embodiment FIG. 1 is a flowchart of a method for manufacturing a well structure according to an embodiment of the present invention. In FIG. 1, 1 is an N-type silicon substrate, 2 is a silicon oxide film, 3 is a silicon nitride film, and 4 is a silicon nitride film. 5 is a resist, 5 is a P-type well, and 6 is a LOCO3 oxide film. The manufacturing method will be briefly described below with reference to FIG. First, a silicon oxide film 2 and a silicon nitride film 3 are formed on an N-type silicon substrate 1. and,
A pattern for alignment in the next step of lithography is formed by selectively etching the silicon nitride film 3 as shown in A (FIG. 1(a)).

Next, an ion implantation blocking region is formed using resist 4 by photolithography, and boron ions are implanted (
Figure 1(b)). Next, with the resist 4 removed and the silicon nitride film 3 formed, P well drive-in is performed (FIG. 1(C)). Then, the silicon nitride film 3 is selectively removed, and the removed region is oxidized to form a LOCO3 oxide film 6 (first
Figure (d)).

Comparing the above steps with the conventional example, first of all, there is no step of forming a thick thermal oxide film on the active region, which was performed in the conventional example, so the induction of crystal defects is suppressed. Second, in the P-well drive-in step, which is a high-temperature heat treatment, the substrate surface is covered with a dense silicon nitride film, which prevents contamination during the heat treatment. The above is effective for devices that are particularly sensitive to substrate quality, such as solid-state image sensors. Thirdly, the process can be simplified.

In other words, the formation of a thick oxide film and the formation of a protective oxide film for ion implantation can be omitted. It is especially superior to the conventional method in the above three points.

In addition, although the manufacturing method of P well was shown in the example,
Even in N-well formation using a Type 1 substrate,
It is clear that similar effects can be obtained.

Effects of the Invention As described above, the present invention provides extremely effective effects such as suppressing the induction of crystal defects, preventing contamination during drive-in, and simplifying the process.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a method for manufacturing a well structure according to an embodiment of the present invention, and FIG. 2 is a flowchart showing a conventional method for manufacturing a well structure. 1.21...N-type silicon substrate, 2,22...
...7 Recon oxide film, 3,23... Silicon nitride film, 4... Resist, 5.25.
...P-type Twel, 6,26...LoCO3
Oxide film, 7... Thick silicon oxide film, 8...
Protective oxide film. Name of agent: Patent attorney Toshio Nakao and 1 other person25
-P shape Riel

Claims (3)

[Claims] (1) A step of forming an oxide film on a semiconductor substrate of one conductivity type, a step of forming a silicon nitride film on the oxide film, and an acceleration energy that sufficiently penetrates the silicon nitride film and the oxide film. A method for manufacturing a semiconductor device, comprising the steps of selectively implanting ions of a conductivity type opposite to that of the semiconductor substrate, and selectively removing the silicon nitride film and performing oxidation treatment. (2) The method for manufacturing a semiconductor device according to claim 1, further comprising a step of heat treatment after the selective ion implantation step. (3) The method for manufacturing a semiconductor device according to claim 1, further comprising a step of forming a pattern for alignment of lithography in the selective ion implantation step and the selective oxidation step before the selective ion implantation step. .