JPH03155126A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve electric characteristics of a tall, small-diameter contact by providing a film to prevent the outdiffusion of impurity during annealing, and providing a barrier metal layer to prevent solid solution reaction between aluminum and polysilicon. CONSTITUTION:A contact hole 5 is formed in an insulating SiO2 film 3 and a BPSG 4, which are provided on one main surface of a wafer 1. A polysilicon layer 6 is deposited on the main surface to fill the contact hole 5. All the polysilicon layer 6 is isotropically etched away except in the contact hole 5. The polysilicon in the contact hole is doped with impurity by ion implantation. The doped region is annealed after an outdiffusion preventive film such as Si3N4 is formed. The preventive film is then removed, followed by the formation of a barrier metal layer 8 and an aluminum layer 9. The layers 8 and 9 are etched to provide an aluminum interconnection layer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which the electrical characteristics of contacts with small diameters and high steps are improved.

(Example) Conventional technology As the degree of integration of semiconductor devices improves, the contact holes that connect the internal elements have become smaller in diameter and have a higher height difference.A simple contact method using Afl or sputtering can eliminate the difference in height. An increase in contact resistance due to a decrease in the film thickness of Aj2, and furthermore, disconnection of the Al wiring at the stepped portion is unavoidable. For this reason, a contact method has been proposed in which polysilicon is buried in the contact hole prior to Al wiring to improve step coverage.

Hereinafter, the manufacturing process of a conventional polysilicon buried contact will be explained with reference to FIG.

Today, the most common insulating film structure is the one shown in Figure 2 (1), where a 3,000-layer thick Si film is grown using a low-pressure vapor phase growth apparatus.
n, film < 23), and 8PSG (boron phosphorus silicate glass, hereinafter referred to as BPSG) (2
The manufacturing process of the polysilicon buried contact formed in the two-layered insulating film of 4) is roughly as follows. Note that the process number and drawing number correspond.

1. Wafer (
A contact hole (26) of 0.8 μm×0.8 μm and depth 1.1 μm is opened in the upper surface of the contact region (22) previously formed in 21).

2. Polysilicon deposition A polysilicon layer (27) with a thickness of 12,000 layers is grown using a low pressure vapor phase growth apparatus.

3. Polysilicon layer (27
), and the polysilicon layer (27) is etched back as shown so as to leave only the polysilicon layer (27) inside the contact hole (26).

4. Ion implantation After ion implantation of "phosphorus" ions into the polysilicon layer (27), 3.
0m1n, is annealed and contact area (22)
The same conductivity type and high conductivity.

5. Al sputter A! 0.8 μm thick using sputtering equipment! (aluminum) film (28) is formed.

6. Al etch photolithography! The aluminum wiring region (28) is left by etching, and then a low temperature heat treatment is performed to improve the contact between aluminum and silicon.

Since the polysilicon buried contact described above has good step coverage, if ion implantation and annealing are properly performed, a contact with extremely good electrical characteristics should be obtained. However, the contact performance designed so far, that is, the contact resistance and ohmic properties, is rarely achieved, and the reason for this is unknown.

Further research revealed that, compared to N1 contacts, in P" contacts, the grain size is smaller due to slower growth of dalein during annealing after ion implantation, and recovery from ion implantation defects also tends to be slower. Therefore, polysilicon It was found that the aluminum interface became unstable, making it easier for polysilicon to dissolve into the aluminum during sintering.

(c) Problems to be Solved by the Invention The present invention is based on the elucidation of the above-mentioned cause of one problem existing in the prior art, and is aimed at improving the electrical characteristics of contacts with small diameters and high height differences, that is, electrical resistance and stability. Another object of the present invention is to provide a method for manufacturing a semiconductor device with improved ohmic properties.

(d) Means for Solving the Problems The present invention involves a step of forming a contact hole in an insulating film on one main surface of a wafer, forming a polysilicon layer on one main surface of the wafer, and filling the contact hole with the polysilicon. Process: Isotropically etching the polysilicon layer leaving only the polysilicon in the contact hole; Implanting impurity ions into the polysilicon within the contact hole; After depositing the out-diffusion prevention film, annealing the ion-implanted region. Go to the process of forming the barrier metal film after removing the out-diffusion prevention film! a step of forming a film;
It consists of a series of steps in which an aluminum wiring region is left by etching an Al film and a barrier metal film.

(*) Effect The process of annealing the ion-implanted region after forming the out-diffusion prevention film prevents out-diffusion of implanted ions and reduces the conductivity of the buried polysilicon layer.

In addition, the process of forming the barrier metal film prevents a solid solution reaction between Al in the Si notch and the buried polysilicon, reducing the relative impurity concentration of the polysilicon and increasing the Si nodule (no.
dule) from occurring.

(F) EXAMPLE The present invention will now be described in detail with reference to FIG. 1, which explains the manufacturing process. Note that the process number and drawing number correspond.

This example consists of the following eight steps. However, all numerical values used in the following explanation are representative values, and do not limit the technical scope of the present invention.

1. Contact hole etching 3 formed on the entire surface of the wafer (1) using a low pressure vapor phase growth apparatus
A Si film (3) with a thickness of 8,000 nm thick was formed on the top surface of this Si film (3) using an atmospheric pressure vapor phase growth apparatus.
A contact hole (6) of 0.8 μm×0.8 μm and 1.1 μm deep is made in the insulating film made of rSG (4) using photolithography and oxide film etching. Note that region (2) is a highly doped contact region specially formed for contact.

2. Polysilicon deposition A polysilicon layer 6) with a thickness of 12,000 layers is grown using a low pressure vapor phase growth apparatus.

3. Polysilicon layer (6) by polysilicon etchback chemical dry etching
Isotropic etching is performed to leave only the polysilicon layer (6) inside the contact hole (5). At this time, the polysilicon layer (6) is etched back so that the Sin film (4) appears on the surface. Ru.

4. Ion implantation Boron ions are implanted into the polysilicon layer (6) under the conditions of an acceleration electric field of 80 keV and a dose of lXl0"ions/cm".

5. Formation of out-diffusion prevention film: Grow a 500 μm thick N4 film (7) using a reduced pressure vapor phase growth apparatus. After that, in a nitrogen gas atmosphere, at 900°C,
Annealing of 30 m1n is performed to make the ion-implanted polysilicon layer (6) the same conductivity type and high conductivity as the contact region (2). Furthermore, after annealing, 5isNa
Remove membrane (7).

6. In Figure 1 (6), which explains the barrier metal sputter manufacturing process, a one-layer structure barrier metal (8) is shown, but a 500mm thick 0cm (titanium) film is formed by sputtering. Furthermore, a 1000-layer thick TiN (titanium nitride) film or TiW (titanium tungsten) film is formed on the top surface.
It is preferable to have a two-layer structure such as a membrane.

7. To 1 spatter A! A 0.8 μm thick Al (aluminum) film (9)) is formed using a sputtering device.

8. Affi, barrier metal etch Photolithography and barrier metal etching leave an aluminum wiring area (10). Thereafter, low-temperature heat treatment is performed to improve the contact between aluminum and silicon.

(G) Effects of the Invention As described above, according to the present invention, the out-diffusion prevention film prevents out-diffusion of impurities during annealing, and forms a Schottky barrier at the interface between the aluminum wiring region and the buried polysilicon layer. and a decrease in conductivity can be prevented.

Furthermore, the barrier metal prevents a solid solution reaction between Al and the buried polysilicon layer, thereby preventing a decrease in conductivity due to the generation of silicon nodules.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a manufacturing process flow explaining the present invention in detail, and FIG. 2 is a cross-sectional view showing a manufacturing process flow explaining a conventional technique.

Claims (3)

[Claims] (1) a step of forming a contact hole in an insulating film provided on one main surface of the wafer; a step of forming a polysilicon layer on one main surface of the wafer and filling the contact hole with the polysilicon; a step of isotropically etching the polysilicon layer leaving only the polysilicon in the contact hole; a step of ion-implanting impurities into the polysilicon in the contact hole; a step of annealing the ion-implanted region after depositing an out-diffusion prevention film; A semiconductor device comprising the steps of forming a barrier metal film after removing an out-diffusion prevention film, forming an Al film, and etching the Al film and the barrier metal film to leave an aluminum wiring region. manufacturing method. (2) The out-diffusion prevention film is Si_3N
The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is formed by _4. (3) The method of manufacturing a semiconductor device according to claim 1, wherein the step of forming the barrier metal film comprises a step of forming a Ti film and a TiN film or a TiW film formed on the top surface of the Ti film.