JPH02177468A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce bird's breaks in the formation of capacitor elements and simplify the forming process by a method wherein an oxidizable first CVD film and an oxidation-resistant second CVD film are in turn stacked on an oxide film, the second CVD film is patterned, and a field oxide film is formed with it as a mask. CONSTITUTION:When a capable element in a semiconductor device is formed, an oxide film 2 is formed on a semiconductor board 1, and an oxidizable first CVD film 3 which serves as a capacitor electrode and an oxidation-resistant second CVD film 4 are in turn formed on the oxide film 2. Next, the second CVD film 4 is selectively patterned. Using the patterned second CVD film 4 as a mask, the first CVD film 3 and the semiconductor board 1 are subjected to a thermal oxidation process to form a thick filed oxide film 7. Next, the second CVD film 4 used as a mask is removed. After the first CVD film 3 that remained without being oxidized is exposed, impurity ions 8 are implanted on the semiconductor board 1 from above the exposed first CVD film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to an improvement in a method for forming a capacitor element such as a memory element in a semiconductor device.

(Prior Art) The main steps of a conventional method for forming a capacitor element in this type of semiconductor device are shown in FIGS. 2(a) to 2(e).
Shown below.

That is, in FIG. 2, the conventional method first
- type silicon semiconductor substrate ll, underlying oxide film 1
2 and a nitride film 13 as an oxidation-resistant film (FIG. 2(a)), and using a resist film 14 patterned by photolithography as a mask, a portion 15 where a capacitor will be formed later is formed. Then, this nitride film 13 is selectively etched away and patterned so that a portion of it remains (FIG. 2(b)).

Next, after removing the resist film 14,
Using the remaining nitride fi+3 as a mask, the so-called
A thick field oxide film 16 is formed in the corresponding portion by thermal oxidation treatment using the LOCO3 oxidation method, and the nitride film 13 and underlying oxide film 12 in the capacitor forming portion 15 are appropriately etched away (as shown in the figure). (C))
.

Furthermore, by thermally oxidizing the entire surface of these, a thin oxide film 17 as a dielectric film is formed, and then a p-type impurity 2, for example, boron 18, is ion-implanted onto the semiconductor substrate 11 to form a high concentration. An impurity region 19 is formed (FIG. 2(d)), and then a polysilicon layer is deposited as an electrode material on the entire surface of the region by CVD, and this is selectively removed by patterning to form a capacitor electrode. A polysilicon layer 20 is formed (FIG. 2(e)), and in this way a desired capacitor element such as a memory element is obtained.

(Problem to be Solved by the Invention) However, in the capacitor element commonly used in conventional memory elements formed through the above-mentioned steps,
In a general manner, the nitride +1i13, which is a patterned oxidation-resistant film, is left on the underlying oxide film 12 of the semiconductor substrate 11, and the corresponding portion is thermally oxidized using the LOGO5 oxidation method. thick field oxide film 16
As a result, the loss of capacitor area due to bird's beak, which is a well-known drawback of this LOGOS oxidation method, is unavoidable, and this is especially difficult for devices that require miniaturization and high density integration. This poses a big problem in securing the gabbacitor capacity, and the formation process itself tends to be relatively too complicated.

The present invention was made to solve these conventional problems, and its purpose is to reduce bird's beak in the formation of capacitor elements in semiconductor devices, and also to improve the formation process. I tried to simplify it. An object of the present invention is to provide a method for manufacturing a semiconductor device of this type, in particular a method for forming a capacitor element in a semiconductor device.

(Means for Solving the Problems) In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention is a method for forming a capacitor element in a semiconductor device, the method comprising: forming an oxide film on a semiconductor substrate; a step of sequentially forming an oxidizable first CVD film and an oxidation-resistant second CVD film, each of which will become a capacitor electrode, on the oxidized top; and selectively forming the second CVD film. Buttering and this buttered second
using the CVD film of the first CVD film as a mask.

and a step of thermally oxidizing the semiconductor substrate to form a thick field oxide film, and a second CVD process used for the mask.
a step of removing the film to expose the first CVD film left without being oxidized; and a step of implanting impurity ions onto the semiconductor substrate from above the exposed first CVD film.
It is characterized by comprising at least:

(Function) That is, in the method of this invention, the first oxidizable material on the oxide film of the semiconductor substrate and used as a capacitor electrode is
sequentially depositing a CVD film of
Since a thick field oxide film is formed through thermal oxidation treatment, bird's beak caused by thermal oxidation can be suppressed, and a sufficient capacitor area and thus its capacity can be secured. .

By simply removing the second CVD film, the first CVD film can be used as it is as a vine capacitor electrode, and the thin underlying oxide film underneath it can be used as it is as an S dielectric film. There is no need to form a film, and the process itself can be simplified.

[Embodiment] Hereinafter, an embodiment of the method for manufacturing a semiconductor device according to the present invention will be described in detail with reference to FIG.

FIGS. 1(a) to d) show a method for manufacturing a semiconductor device applying the method of this embodiment. In FIG. It is.

That is, in this FIG. 1, the method of the embodiment first
After forming a thin underlying oxide film 2 on a - type silicon semiconductor substrate 1, a first oxidizable CVD film as a capacitor electrode is formed on this underlying oxide film 2 by a CVD method.
In this case, a polysilicon layer 3, an oxidation-resistant second CVD film, and a nitride film 4 are sequentially deposited (first
Using the resist film 5 patterned by photolithography as a mask as shown in FIG. It is then removed by etching and buttered (FIG. 2(b)).

Next, after removing the resist film 5, using the nitride film 4 left by the buttering as a mask, thermal oxidation is performed using the LOGO3 oxidation method to form a thick field oxide film 7 in the corresponding part. However, at this time, the portions of the polysilicon film 3 that are not masked by the patterned electrified film 4 are oxidized, so as is well known, the spread of the bird's beak is suppressed. In this way, it is possible to perform thermal oxidation treatment with a shortened bird's beak (Zl(c)
). Subsequently, by appropriately etching and removing the nitride film 4 in the capacitor forming portion 6, the polysilicon film 3 under the nitride film 4 is exposed as a capacitor electrode, and The thin underlying oxide film 2 or S is left as a dielectric film, and then from these F to +Jf semiconductor substrate! A p-type impurity 9, for example, boron 8, is ion-implanted thereon to form a high concentration impurity region 9 (FIG. 2(d)), and in this way, a capacitor such as a memory element as specified is obtained.

Therefore, in this embodiment method, an oxidizable polysilicon layer 3 as a capacitor electrode and an oxidation-resistant nitride film 4 are sequentially deposited on the underlying oxide film 2 of the semiconductor substrate l, and The nitride film 4 is buttered, and the buttered electrified film 4 is used as a mask to perform LOCO
5 A thick field oxide film 7 is formed by thermal oxidation using the oxidation method.
Since the bird's beak can be effectively suppressed, sufficient capacitance can be secured without reducing the capacitor area. By simply removing the polysilicon 1Ii3, the polysilicon 1Ii3 is exposed as it is as a capacitor electrode, and the thin underlayer oxide [2] is left as it is as a dielectric film. There is no need to form the same, and the process itself can be simplified.

In addition, in the method of the embodiment, p is used as the semiconductor substrate.
- type silicon substrate and boron as the ion-implanted impurity have been described, but as long as it functions as a capacitor element, a combination of various types of silicon substrates and various types of impurities may be used. Similar effects and effects can be obtained.

(Effects of the Invention) As described in detail above, according to the method of the present invention, in the method of forming a capacitor element in a semiconductor device, an oxidizable first CVD film as a capacitor electrode is formed on an oxide film of a semiconductor substrate. By sequentially depositing the film and a second oxidation-resistant CVD film, buttering the second CVD film, and using the buttered second CVD film as a mask. Since a thick field oxide film is formed by thermal oxidation treatment, the expansion of the bird's beak caused by heat treatment can be effectively suppressed, and the reduction in capacitor area can be avoided. It has the advantage that a large capacitor capacity can be secured, and by simply removing the second CVD film after forming this field oxide film, the first CVD film 1i can be used as a capacitor electrode, and can also be used as a capacitor electrode. Since the thin oxide film can be used as it is as a dielectric layer, there is no need to form the first CVD film and the oxide film again, and the process itself can be simplified. As a result, it has excellent features such as being able to easily manufacture devices with miniaturization and high density integration.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are cross-sectional views each schematically showing the main steps of a method for manufacturing a capacitor in a semiconductor device using an embodiment of the method of the present invention,
Further, FIGS. 2(a) to 2(e) are cross-sectional views sequentially schematically showing the main steps of a conventional method for manufacturing the above-mentioned capacitor. l...Silicon semiconductor substrate, 2...Underlay oxidation■
q, 3...Polysilicon layer (first CVD 115m
), 4... nitride film (second CVD film), 5...
Resist film, 6...Capacitor forming part, 7...
・Field oxide film, 8...Boron (impurity), 9
...High concentration impurity region. Agent Oiwa Masu Miscellaneous 11; Ho゛口〉(Floating proboscis) 9; Highly concentrated Fukin U Mukken Prefecture

Claims (1)

[Claims] A method for forming a capacitor element in a semiconductor device, the method includes the steps of forming an oxide film on a semiconductor substrate, a first oxidizable CVD film that will become a capacitor electrode, and a second oxidation-resistant CVD film on the oxide film. The second CVD film is selectively patterned, and the patterned second CVD film is used as a mask to form the first CVD film and the semiconductor substrate. forming a thick field oxide film by thermal oxidation;
A step of removing the second CVD film used as the mask to expose the first CVD film left without being oxidized, and introducing impurity ions onto the semiconductor substrate from above the exposed first CVD film. A method for manufacturing a semiconductor device, the method comprising at least the step of injecting.