JPH0353519A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to fill up a contact hole with polycrystalline silicon in an excellent reproducible manner by a method wherein, after the contact hole has been filled up with a conductive polycrystalline silicon film and an undoped polycrystalline silicon film, phosphorus is doped on the non- doped polycrystalline silicon film excluding the inside of the contact hole, and then an etching treatment is conducted. CONSTITUTION:First, an N<+> diffusion layer 12 is at least selectively formed on a P-type semiconductor substrate 11. A silicon oxide film 13 is coated using an oxide film vapor growth method, and a contact hole is perforated. Then, a polycrystalline silicon film is coated, and phosphorus is added by thermal diffusion. Then, after the contact hole has been filled up by coating an undoped polycrystalline silicon film 15, phosphorus is implanted by conducting an ion implanting method under the condition wherein phosphorus is not added to the polycrystalline silicon located inside the contact hole. Then, the polycrystalline silicon films 14 and 15 in the contact hole are left, and the polycrystalline silicon films 17 and 18 on the other region are removed. Then, an Al wiring layer 16 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of burying a contact hole.

[Conventional technology]

One of the methods for miniaturizing semiconductor devices is to bury and planarize contact holes using polycrystalline silicon or high-melting point metal. Conventional technology using polycrystalline silicon is shown in Figures 3(a) and (b).
).

As shown in FIG. 3(a), an N+ diffusion layer 2 is at least selectively formed on a P-type semiconductor substrate 1 (silicon). After a silicon oxide film 3 is deposited by vapor phase growth, a contact hole is opened. Next, polycrystalline silicon is deposited, and phosphorus is added by thermal diffusion to form conductive polycrystalline silicon wA4.Next, a non-doped polycrystalline silicon film 5 is deposited.

Next, as shown in FIG. 3(b), by anisotropic dry etching, the polycrystalline silicon film 4.5 in the contact hole is left and the polycrystalline silicon in other regions is removed. Next, the AJ2 wiring 6 is formed.

[Problem to be solved by the invention]

In the conventional contact hole filling method described above, a polycrystalline silicon film is etched using an anisotropic dry etching method, but due to variations in the thickness of the deposited polycrystalline silicon film and variations in the etching rate of the anisotropic dry etching, Overetching may occur depending on the location within the semiconductor substrate. In such a place, there is no polycrystalline silicon to be filled in the contact hole, resulting in a steep step, and when forming the wiring layer, the disadvantage is that the wiring layer breaks as shown in Figure 4. There is.

An object of the present invention is to provide a method for manufacturing a semiconductor device that allows contact holes to be filled with polycrystalline silicon with good reproducibility. [Means for Solving the Problems] The method for manufacturing a semiconductor device of the present invention includes forming an insulating film having a contact hole on one main surface of a semiconductor substrate, and then
depositing a first polycrystalline silicon film to a thickness that does not fill the contact hole; adding phosphorus to the first polycrystalline silicon film; a step of depositing a second polycrystalline silicon film to a thickness that fills the contact hole; a step of adding phosphorus to the second polycrystalline silicon film except for the inside of the contact hole; The method includes a step of removing the first polycrystalline silicon film doped with phosphorus and the second polycrystalline silicon film doped with phosphorus.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1A to 1C are cross-sectional views of a semiconductor chip shown in the order of main steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1(a), a P-type semiconductor substrate 11
The N+ diffusion layer 12 is at least selectively formed. A silicon oxide film 13 of 1.0 .mu.m is deposited by a vapor phase oxide film lengthening method, and a contact hole with an opening diameter of 1.0 .mu.m x 1.0 .mu.m is made. Next, apply a polycrystalline silicon film to a thickness of 200 nm.
It adheres and phosphorus is added through thermal expansion. N+ diffusion layer 12
This is to provide a low-resistance connection between the wire and the wiring layer that will be formed in a later process. The conductive polycrystalline silicon film 14 thus formed only covers the aforementioned contact hole and the surface of the underlying N+ diffusion layer 12, but does not fill the contact hole.

Next, as shown in FIG. 1(b), a non-doped polycrystalline silicon film 15 is deposited to a thickness of 800 nm to fill the contact hole, and then ion implantation is performed to inject phosphorus into the polycrystalline silicon in the contact. In this case, phosphorus is injected at 550 keV and 16 crs-2. 17 is a phosphorus-doped polycrystalline silicon film;
Reference numeral 18 denotes a highly concentrated phosphorus-doped polycrystalline silicon film in which phosphorus is added by ion implantation to the region (14) to which phosphorus is added by thermal diffusion.

Next, as shown in FIG. 1(c), a mixture of hydrofluoric acid and nitric acid is used to remove the polycrystalline silicon 14 in the contact hole.
．． 15 is left and the other areas are polycrystalline silicon 17.
Remove 18. Next, an Affi wiring layer 16 is formed.

Polycrystalline silicon with a high phosphorus concentration is etched faster in a mixture of hydrofluoric acid and nitric acid than polycrystalline silicon with a low phosphorus concentration, so non-doped polycrystalline silicon can be reliably left in the contact hole. Contact holes filled with crystalline silicon can be stably manufactured.

A second embodiment of the present invention will be described with reference to FIGS. 2(a) to 2(c).

First, as shown in FIG. 2(a), a P-type semiconductor substrate 21
An N+ diffusion layer 22 is formed therein. A silicon oxide film 23 of 1.0 μm is deposited by a vapor phase oxide film lengthening method, and
Drill a contact hole with an opening diameter of 1.0 μm. Next, 200 nm of polycrystalline silicon is deposited, and phosphorus is added by thermal diffusion.

Next, a non-doped polycrystalline silicon film 25 of 800 nm is deposited. The process up to this point is the same as the first embodiment. Next, by ion implantation method, 300 keV, I
Phosphorus is injected under conditions of m-2. 27 is a polycrystalline silicon film doped with phosphorus, and 25 is a polycrystalline silicon film to which phosphorus is not added. Next, as shown in FIG. 2(b), the polycrystalline silicon film 27 doped with phosphorus is removed using a mixed solution of hydrofluoric acid and nitric acid. Furthermore, by ion implantation method,
In this case, phosphorus is implanted at 300 keV and IXIO"Cal-2 under the condition that phosphorus is not added into the contact. 28 is a region where phosphorus is added by thermal diffusion, and a high temperature region where phosphorus is added by ion implantation is added. Next, as shown in Figure 2 (C), a mixed solution of hydrofluoric acid and nitric acid is used to leave the polycrystalline silicon 14 and 15 in the contact hole, and to remove the remaining polycrystalline silicon. The polycrystalline silicon 27, 28 in the region is removed.Next, the Af wiring layer 26 is formed.Polycrystalline silicon with a high phosphorus concentration is more resistant to a mixed solution of hydrofluoric acid and nitric acid than polycrystalline silicon with a low phosphorus concentration. By taking advantage of the high etching speed and repeating the process of adding phosphorus and removing the phosphorus-added polycrystalline silicon multiple times, the contact hole filled with polycrystalline silicon can be made more stable. It can be manufactured by

〔Effect of the invention〕

As explained above, in the present invention, after a contact hole is filled with a conductive polycrystalline silicon film and a non-doped polycrystalline silicon film, the non-doped polycrystalline silicon film is doped with phosphorus except inside the contact hole, and then etched. By doing this, polycrystalline silicon doped with a high concentration of phosphorus is more susceptible to chemicals such as hydrofluoric acid than polycrystalline silicon doped with a low concentration of phosphorus or polycrystalline silicon with no impurities. Utilizing the high etching rate of a mixed solution of nitrate and nitric acid, semiconductor devices having contact holes filled with polycrystalline silicon can be manufactured with good controllability.

[Brief explanation of drawings]

FIGS. 1(a) to 1(c) are cross-sectional views of semiconductor chips arranged in the order of main steps for explaining the first embodiment of the present invention;
FIGS. 2(a) to (C) are cross-sectional views of semiconductor chips arranged in the order of main steps for explaining a second embodiment of the present invention;
3(a) and 3(b) are cross-sectional views of semiconductor chips arranged in the order of main steps to explain the conventional manufacturing method of semiconductor devices, and FIG. 4 is a cross-sectional view of the semiconductor chip to explain the drawbacks of the conventional example. This is a cross-sectional view. 1.11.21...P-type semiconductor substrate, 2.12.22
... N+ diffusion layer, 3.13.23 ... silicon oxide film, 4, 14.24 ... conductive polycrystalline silicon film, 5
．． 15.25...Non-doped polycrystalline silicon film, 6,
16.26...Ajl wiring, 17, 27, 18, 28
．． 29...Phosphorus-doped polycrystalline silicon film.

Claims (1)

[Claims] forming an insulating film having a contact hole on one main surface of the semiconductor substrate, and then depositing a first polycrystalline silicon film to a thickness that does not fill the contact hole; a step of adding phosphorus to the film; a step of depositing a second polycrystalline silicon film on the first polycrystalline silicon film to a thickness that fills the contact hole;
a step of adding phosphorus to the second polycrystalline silicon film except inside the contact hole; and the first polycrystalline silicon film doped with phosphorus and the second polycrystalline silicon film doped with phosphorus outside the inside of the contact hole. 1. A method for manufacturing a semiconductor device, the method comprising: removing a silicon film.