JPS5885546A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress a narrow channel effect phenomenon by forming a sectional sector-shaped film which narrows downwardly on an oxidation resistant film formed above a region for forming an element of a semiconductor substrate, implanting impurity ions with the sector-shaped film as a mask and forming a field oxidized film with the resistant film as a mask. CONSTITUTION:The entire surface of a silicon oxidized film 25 is etched to the surface of a photoresist film 24 with ammonium solution, thereby exposing the surface of the film 24. Subsequently, the film 24 is etched and removed, thereby forming a sectional sector-shaped silicon oxidized film 25 which narrows downwardly. Then, with the film 25 as a mask a silicon nitrided film 23 is etched and removed by a chemical dry etching method. Thereafter, with the film 25 as a mask channel stopper impurity (such as boron) ions are implanted to the surface of a substrate 21, thereby forming a p<+> type field inversion preventive region 26.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device.
This article relates to improvements in SI element isolation technology.

Conventionally, for example, as an element isolation technology for MOS-LSI,
A so-called selective oxidation method was commonly used. Hereinafter, the steps of the selective oxidation method will be briefly explained with reference to FIG. Semiconductor substrate (for example, P type, crystal orientation [100]) 7
An oxide film 2 is formed on the surface of the oxide film 2, and an oxidation-resistant mask such as a silicon nitride film 3 is deposited on the oxide film 2. , /4'
Turn. Then, for example, impurities in the field part? The inversion prevention region 4 is formed by ion implantation and addition of ions. Next, field oxidation is performed to form a field oxide film 5, and 7 selective oxidation is performed.

However, the highly integrated manufacturing process using the selective oxidation method described above has the following drawbacks. That is, the width of the field oxide film 5 is determined not only by the technical limit of photolithography, but also by the length of the so-called bird's beak, which limits the width of the field. Furthermore, did you implant ions for the channel stopper? During the field oxidation process, Ron is also diffused laterally into the 1-element formation region (section A in Figure 1) or the P region.
The effective device area becomes narrower. Unfortunately, this has the disadvantage of causing narrow channel effects such as a decrease in transistor current and an increase in threshold voltage.

The present invention has been made in view of the above circumstances, and its object is to provide an oxidation-resistant film above a region of a semiconductor substrate where elements are not to be formed, and to form a fan-shaped cross section that narrows downward on the oxidation-resistant film. A film is provided, and impurities are ion-implanted using this fan-shaped film as a mask 7. By forming a field oxide film using the oxidation-resistant film as a mask, the impurities ion-implanted especially for channel strike and passivation are diffused into the element region. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can substantially reduce the narrow channel effect phenomenon that becomes an obstacle when producing highly integrated devices.

An embodiment of the present invention will be explained below with reference to the drawings.

1. First, as shown in FIG. For example, a silicon nitride film 23 is deposited as a permanent film material.

Next, a photoresist 1 is applied on this silicon nitride film 23.
11224 (e.g., positive type resistor made by Tokyo Ohkasha) 0F
PR800) is formed, and this resist film 24 is patterned by a normal photographic method. After this Ze-turning process, the peripheral edge of the photoresist glossy turn has a gentle slope of 180 mm that narrows in the depth direction.
Perform baking at about ℃. Exposed silicon nitride film 23
A silicon oxide film 25 is then formed on the photoresist film 24. In this process, a coating solution for forming a silicon oxide film [for example, OC
D (manufactured by Tokyo Ohka Co., Ltd., trade name)] is applied and formed using a spinner, and the necessary baking is performed to form the silicon oxide film 25.
It forms the

Next, as shown in FIG. 2(B), the silicon oxide film 25
The entire surface of the photoresist film 240 is etched using an ammonium fluoride solution or the like to expose the surface of the photoresist film 240. Thereafter, this photoresist film 24 is removed by etching to form a silicon oxide film 25 having a fan-shaped cross section that is narrower at the bottom. Next, as shown in FIG. 2 (0), using the silicon oxide film 25 as a mask, the silicon nitride film 23 is removed by chemical drying and etching. Next, using the fan-shaped silicon oxide film 25 as a mask, A P-type field inversion prevention region 26 is formed by ion-implanting an impurity (for example, boron) into the inner surface of the channel 21.
form. At this time, since the shape of the silicon oxide film 25, which serves as a mask during ion implantation, has a fan-like, reversely tapered cross section, the edge of the P+ type field reversal prevention region 26 formed by ion implantation is Reverse chi! The shape is determined by the length of the upper side of the silicon oxide film 25. Next, the second
As shown in Figure (D), an oxidation-resistant silicon nitride film 23
The upper silicon oxide film 25 and the silicon oxide film 22 on the upper part of the substrate 2 are removed and exposed! 1.
Using the silicon nitride film 23 as an oxidation mask, a field oxide film 27 is formed by combustion on the exposed surface of the substrate 210. In this way, since the first impurity for forming the channel strike and oxide regions is ion-implanted on the mask for forming the field oxide film 27 through the fan-shaped cross-sectional mask, the ends of the mask are different; The field inversion prevention region 26 does not diffuse into the element region, suppressing the narrow channel effect and making it easier to suppress the threshold voltage of the transistor.

Note that from this point on, the transistor may be manufactured according to a normal manufacturing process. Since this step is a common technique for those skilled in the art, its explanation will be omitted.

Next, an example of forming an ion implantation mask having a fan-shaped cross section formed on an llI4 oxidation mask will be described. As shown in FIG. 3(A), the semiconductor substrate (for example, P
A 1-depleted Hm 32 is formed on the wall and the crystal orientation [100]) 31, and a silicon nitride film 33, for example, is deposited on this oxide film 32-1 as a -6-oxidation-resistant film material. Next, an oxide film 34 is formed on this silicon dimpled film 33 by the CVD method.

Next, after exposure to a CF4 gas plasma 7, a photoresist film (not shown) is formed on the oxide film 34, and this photoresist film is subjected to non-turning by photolithography. After that, when the oxide film 34 is etched with an NH4F solution using the photoresist pattern as a mask, the side where the photoresist pattern and the oxide film 34 are in close contact deteriorates due to the plasma irradiation, and the pattern of the oxide film 34 is as shown in FIG. 3(B). The base is etched so that it becomes narrower in the depth direction. In addition to the plasma irradiation method described above, such a taper nip can be etched by etching using an etching solution containing a small amount of alcohol or the like mixed in an NH4F solution without plasma irradiation. A photoresist 35 is applied using a spinner to the silicon nitride film 33 and oxide film 34 exposed by the thus formed silicon nitride film 33 and oxide film 34 formed by etching. Etch until the surface is exposed. And this exposure [.

When the fused film 34 is etched, a photoresist 35 having a viscous cross-section as shown in FIG. 3(C)K is formed.

The subsequent steps are shown in FIG. 2(C) in the above example.
, may be carried out in the same manner as the step (D).

As explained above, according to the present invention, an antioxidizing film is provided above a region for forming elements of a semiconductor substrate, and a fan-shaped film with a cross section narrowing downward is provided on this one antioxidizing film. By implanting impurity ions as a mask and forming a field oxide film using the oxidation-resistant film as a mask, diffusion of the impurity ion-implanted especially for channel stop 2 into the device region is substantially reduced, It is possible to provide a method for manufacturing a semiconductor device that suppresses the narrow channel effect phenomenon that becomes an obstacle when producing highly integrated devices.

[Brief explanation of drawings]

FIG. 1 is a structural cross-sectional view of a tank explaining a conventional semiconductor device manufacturing method, and FIGS. 2 (A) to (9) are structural cross-sectional views showing an embodiment of the present invention in the order of manufacturing steps. , and FIGS. 3(/1) to (C) are structural sectional views showing another embodiment of the present invention in the order of manufacturing steps. 21.31... Semiconductor substrate, 22.32... Oxide film, 23.33... Oxidation resistant film (Silicon shop 1 to J)
, 24.34...Oxide film, 25...Silicon oxide film, 35...Photoresist, 26...Field inversion prevention region, 27...Field oxide film. Applicant's agent Patent attorney Takehiko Suzue-9= Figure 1 Figure 2 (A)

Claims (2)

[Claims] (1) A process of providing an oxidation-resistant film above the area where elements are to be formed on a semiconductor substrate, a process of providing a fan-shaped film with a cross section that narrows downward on the oxidation-resistant film, and using this fan-shaped film as a mask to ionize impurities. A method for manufacturing a semiconductor device, comprising the steps of: implanting; and forming a field oxide film using the oxidation-resistant film as a mask. (2) The fan-shaped film is formed by forming a first film having an etching groove that narrows in the depth direction on the oxidation-resistant film.
2. The method of manufacturing a semiconductor device according to claim 1, wherein the second film is formed in the etching groove of the first film, and then the first film is etched.