JPS6159675B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a MOS type semiconductor device.

A conventional method for manufacturing a MOS type semiconductor device will be explained with reference to FIG. Conventionally, a gate oxide film 2 is first formed on a semiconductor substrate, such as a silicon substrate 1, with a thickness of 300 to 300 nm.
A polycrystalline silicon film 3 containing impurities is formed thereon to a thickness of 3000 to 5000 Å.
Furthermore, a thin oxide film 4 having a thickness of 200 to 500 Å is formed on the polycrystalline silicon film 3, and a silicon nitride film 5 is formed thereon to a thickness of 1000 to 2000 Å. (See FIG. 1a) Next, leaving only the active region 6, the silicon nitride film 5, thin oxide film 4, polycrystalline silicon film 3, and gate oxide film 2 are sequentially removed. In addition, before or after removing the gate oxide film 2, the same impurity as the silicon substrate 1, such as boron, is implanted into the entire surface of the silicon substrate 1 other than the active region 6 by ion implantation in order to isolate the elements. Region 7 is formed. (See FIG. 1b) Next, a thick thermal oxide film 8 having a thickness of 6000 to 10000 Å is formed on the silicon substrate 1 for isolation between elements.
At this time, the side surfaces of the polycrystalline silicon film 3 are also oxidized. Therefore, the width of the active region 6 becomes smaller. At the same time, the side surface of the polycrystalline silicon film 3 is oxidized and expands, causing protrusions 9 of the oxide film.
is created. (See Figure 1c) Next, leaving only the gate region 10 in the active region 6, the other active regions 6 are covered with a silicon nitride film 5, a thin oxide film 4, a polycrystalline silicon film 3, and a gate oxide film. Perform the removal of 2. Further, an impurity such as phosphorus is diffused over the entire surface to form impurity diffusion regions 11 that will become source/drain regions in the silicon substrate 1. (See FIG. 1d) Next, by thermal oxidation, an oxide film 12, which will become an intermediate insulating film, is formed on the impurity diffusion regions 11, which will become the source and drain. At this time, the side surfaces of the polycrystalline silicon film 3 in the gate region 10 are also oxidized, resulting in a reduction in gate length and gate width. At the same time, the side surfaces of the polycrystalline silicon film 3 are oxidized and expanded, resulting in the formation of protrusions 13 of the oxide film. (See FIG. 1 e) Next, the silicon nitride film 5 on the gate region 10 is
remove. The thin oxide film 4 underneath is also removed. Then, polycrystalline silicon film 3, thermal oxide film 8
and metal wiring on the oxide film 12, for example, Al.
By forming the wiring 14, a self-aligned contact between the metal wiring and the gate is made.
(See FIG. 1 f.) However, in such a conventional manufacturing method, as mentioned above, when forming the thick thermal oxide film 8 and furthermore when forming the oxide film 12, the side surfaces of the polycrystalline silicon film 3 are also oxidized. Therefore, there is a drawback that the width of the active region 6, as well as the gate length and gate width cannot be precisely controlled. Further, due to the expansion of the side surface of the polycrystalline silicon film 3 due to the oxidation, the protrusions 9 and 1
3, it has the disadvantage that the surface becomes uneven.

The present invention has been made in view of the above points, and provides a method for manufacturing a MOS type semiconductor device that can accurately control the active region width, gate length, and gate width, and can also have a smooth surface. The purpose is to provide.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing an embodiment of the invention.
In this embodiment, first, a gate oxide film 22 is formed to a thickness of 300 to 1000 Å on a semiconductor substrate, such as a silicon substrate 21, and a polycrystalline silicon film 23 containing impurities is formed thereon to a thickness of 3000 to 5000 Å. moreover,
A thin oxide film 24 with a thickness of 200 to 500 Å is formed on the polycrystalline silicon film 23, and a silicon nitride film 2 is formed on it.
5 to a thickness of 1000 to 2000 Å. (See FIG. 2a) Next, the multilayer film (consisting of the gate oxide film 22, the polycrystalline silicon film 23, the thin oxide film 24, and the silicon nitride film 25) is left only in the active region 26, and the remaining parts are the silicon nitride film 25, Thin oxide film 24, polycrystalline silicon film 23, and gate oxide film 22 are removed in this order. In addition, before or after removing the gate oxide film 22, impurities of the same type as the silicon substrate 21, such as boron, are implanted by ion implantation for device isolation into the silicon substrate 21 other than the active region 26. Diffusion area 27
form. (See FIG. 2b) Next, a thin oxide film 28 is formed on the side surface of the polycrystalline silicon film 23 by thermal oxidation, and a silicon nitride film 29 is further formed to a thickness of 1000 to 2000 Å on the entire surface.
In this case, the thin oxide film 28 is also formed on the surface of the silicon substrate 21 other than the active region 26. (Figure 2c
(See) Thereafter, the silicon nitride film 29 is removed by dry etching, such as sputter etching. In this case, by selecting conditions appropriately, the active area 2
The silicon nitride film 25 can be left on the top surface of the polycrystalline silicon film 23 of No. 6, and the silicon nitride film 29 can be left on the side surfaces. Next, the thin oxide film 28 on the surface of the silicon substrate 21 other than the active region 26 is removed.
(See FIG. 2d) Next, a thick oxide film 30 for isolation between elements is formed on the surface of the silicon substrate 21 around the active region 26 by thermal oxidation. At this time, since the side surfaces of the polycrystalline silicon film 23 in the active region 26 are also covered with the silicon nitride film 29, there is no lateral oxidation. Therefore, the width of the active region 26 does not decrease, and no protrusions of the oxide film caused by side oxidation of the polycrystalline silicon film 23 occur. (See FIG. 2e.) Next, in the active region 26, only the gate region 31 is left with the multilayer film, and the other active regions 26 are covered with silicon nitride films 25, 29, a thin oxide film 24, and a polycrystalline silicon film 23. , the gate oxide film 22 is removed. Further, an impurity such as phosphorus is diffused over the entire surface to form impurity diffusion regions 32 that will become source/drain regions in the silicon substrate 21. (1st
(See FIG. (see Figure g).

Thereafter, the silicon nitride film 34 is removed by dry etching, such as sputter etching. In this case, by appropriately selecting conditions, it is possible to leave the silicon nitride film 25 on the upper surface of the polycrystalline silicon film 23 in the gate region 31 and the silicon nitride film 34 on the side surfaces. Next, the thin oxide film 33 other than the gate region 31 is removed. (See FIG. 2h) Next, by thermal oxidation, an oxide film 35 that will become an intermediate insulating film is formed to a thickness of 2000 to 5000 Å on the impurity diffusion regions 32 that will become the source and drain. At this time,
Since the side surfaces of the polycrystalline silicon film 23 are covered with the silicon nitride film 34, oxidation of the side surfaces does not occur. Therefore, reduction of gate length and gate width,
No protrusions of oxide film are formed. (See FIG. 2i) After that, the silicon nitride film 2 of the gate region 31 is
Remove 5,34. In addition, thin oxide films 24, 3
3 is also removed. And polycrystalline silicon film 23,
By forming a metal wiring, such as an Al wiring 36, on the oxide films 30 and 35, a self-aligned contact between the metal wiring and the gate is made.
(See FIG. 2j.) In the above embodiment, the side surfaces of the polycrystalline silicon film 23 in the active region 26 and gate region 31 are covered with oxide films 28 and 33, and the silicon nitride film 23 is further covered with the silicon nitride film 23.
9 and 34, but the oxide films 28 and 33
can be omitted.

As described above in the embodiments, in the manufacturing method of the present invention, the exposed side surfaces of the polycrystalline silicon film are covered with a silicon nitride film during oxidation. Therefore, the side surfaces of the polycrystalline silicon film are prevented from being oxidized during oxidation, and as a result, the active region width, as well as the gate length and gate width, can be precisely controlled. Furthermore, since the formation of protrusions in the oxide film due to lateral oxidation of the polycrystalline silicon film can be prevented, the surface can be made smooth.

[Brief explanation of the drawing]

1A to 1F are sectional views showing a conventional method for manufacturing a MOS type semiconductor device, and FIGS. 2A to 2J are sectional views showing an embodiment of the method for manufacturing a MOS type semiconductor device according to the present invention. 21... Silicon substrate, 22... Gate oxide film, 23... Polycrystalline silicon film, 24... Oxide film, 25... Silicon nitride film, 26... Active region, 28... Oxide film, 29... Silicon nitride film,
30... Oxide film, 31... Gate region, 33...
Oxide film, 34... silicon nitride film, 35... oxide film.

Claims (1)

[Claims] 1. A multilayer film consisting of a gate oxide film, a polycrystalline silicon film containing impurities formed on it, a thin oxide film formed on it, and a silicon nitride film formed on it. a step of forming a thin oxide film on the side surface of the multilayer film; a step of forming a silicon nitride film on the entire surface of the multilayer film; and a step of forming a silicon nitride film on the entire surface of the multilayer film. A method of manufacturing a MOS type semiconductor device, comprising the step of forming an oxide film on the surface of the semiconductor substrate. 2. A multilayer film consisting of a gate oxide film, a polycrystalline silicon film containing impurities formed on it, a thin oxide film formed on it, and a silicon nitride film formed on it is deposited on a selected surface of the semiconductor substrate. a step of forming a silicon nitride film on the entire surface of the multilayer film; and a step of forming an oxide film on the surface of the semiconductor substrate around the multilayer film. manufacturing method.