JPH0371626A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the electrical characteristics of a contact in small bore and high step by a method wherein a contact hole sidewall part is covered with an Si3N4 film and after ion-implanting a polysilicon layer in the contact hole with an impurity, an outdiffusion preventive film is formed to anneal the ion-implanted region. CONSTITUTION:The process of covering a contact hole 6 sidewall part with an Si3N4 film 7 avoids the impurity compensation of a polisilicon layer by the diffusion of inverse conductivity type impurity from BPSG to the buried polysilicon layer. Furthermore, the annealing process of ion implanted region after the formation of an outdiffusion preventive film 9 avoids the outdiffusion of implanted ion as well as the decrease in the conductivity of a buried polisilicon layer 8 and the formation of a barrier in the interface of the layer 8. Through these procedures, the electrical characteristics of the contact in small bore and high step, i.e., electric resistance, stability and ohmic property can be enhanced.

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.

(0) Conventional technology As the degree of integration of semiconductor devices increases, the contact holes that connect internal elements have become smaller in diameter and have higher height differences. An increase in contact resistance due to a decrease in the Al film thickness and furthermore, disconnection of the AI wiring at the stepped portion is unavoidable. For this reason, a contact method has been proposed in which polysilicon is buried in contact holes prior to AI 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).
n, film (23), 8000A thick BPSG (boron phosphorus silicate glass, hereinafter referred to as BPSG) formed on the top surface using an atmospheric vapor phase growth apparatus (
The manufacturing process of the polysilicon buried contact formed in the two-layered insulating film of 24) is roughly as follows. Note that the process number and drawing number correspond.

1. Wafer (
21) on the upper surface of the contact region (22), which is 0.8 μm×0.8 μm and has a depth of 1. Drill a contact hole (26) of 11 m.

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

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

After implanting phosphorus ions into the polysilicon layer (27), it was heated to 9°0°C and 30°C in a nitrogen gas atmosphere.
min, )7=-le and contact area (
Same conductivity type as 22), but higher conductivity.

5. AI sputtering AI (aluminum) Ill (28) with a thickness of 0.8 μm is formed using an AI sputtering device.

6. Leave an aluminum wiring area (28) by Al etch photolithography and AI etching. Thereafter, low-temperature heat treatment is performed to improve the contact between aluminum and silicon.

Since the polysilicon buried contact described above has good stenob coverage, if ion implantation and annealing are properly performed, a contact with extremely good electrical characteristics should be obtained. However, until now, the contact performance set at 5f, that is, the contact resistance and ohmic properties, has rarely been achieved, and the reason for this was unknown.

As a result of the inventors' research on this point, it was found that boron, an impurity of the opposite conductivity type, spreads from the BPSG (24) to the polysilicon layer (27) during annealing in Process 4, and is compensated for by the polysilicon layer (27). The conductivity of layer (27) is reduced and as illustrated in FIG.
The ions implanted in step 4 are outdiffused during the subsequent heat treatment and form the aluminum wiring area (2).
It has been clarified that this decrease in the impurity concentration at the interface between 8) and the polysilicon layer (27) causes a barrier to be formed due to contact between different types of conductors.

(...) Problems to be Solved by the Invention The present invention is based on the elucidation of the above-mentioned causes of the problems existing in the prior art. 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 provides a method for solving the problems by forming a
A process of growing a 13N4 film, an anisotropic etching process that leaves only the Si and N1 films on the side walls of the contact hole, a process of forming a polysilicon layer on one side of the wafer and filling the contact hole with this polysilicon, and a process of forming the contact hole. A step of isotropically etching the polysilicon layer leaving only the polysilicon inside the contact hole, a step of ion-implanting impurities into the polysilicon inside the contact hole, a step of annealing the ion-implanted region after forming an out-diffusion prevention film, and annealing the ion-implanted region to prevent out-diffusion. Step of forming an AI film after film removal, A
It consists of a series of steps in which an aluminum wiring area is left by etching the I film and barrier metal film.

(The process of coating the sidewalls of the contact holes with Si, N, and films prevents impurity convention in the polysilicon layer due to the diffusion of impurities of the opposite conductivity type from the BPSG to the buried polysilicon layer.

Further, the process of annealing the ion implanted region after forming the outdiffusion prevention film prevents outdiffusion of the implanted ions, and prevents a decrease in the conductivity of the buried polysilicon layer and the formation of a barrier at its interface.

(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 embodiment consists of the following IO process. However, all the numerical values used in the following explanation are representative values, and
This is not intended to 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
000000A thickness n, film (3), this Sin.

800 was formed on the top surface of the film (3) using an atmospheric vapor phase growth apparatus.
Using photolithography and oxide film etching, an insulating film made of PSG (4) with a thickness of 0.0000A was etched to 0.8μm.
A contact hole (6) with a diameter of 0.8 μm and a depth of 1.1 μm is opened. Note that region (2) is a highly doped contact region specially formed for contact.

2. SisN4 film deposition A 500A thick SiN film (
7) Grow.

3. S l 3N (film etch) Perform anisotropic etching by dry etching such as reactive ion etching, leaving only the Si, N, and film on the side wall of the contact hole (6).

4. Polysilicon deposition A polysilicon layer (8) with a thickness of 12,000 layers is grown using a low pressure vapor phase growth apparatus.

5. Polysilicon layer (8) by polysilicon etchback chemical dry etching
Isotropic etching is performed to leave only the polysilicon (8) inside the contact hole (6). At this time, SiO! The polysilicon (8) is etched back so that the membrane (5) appears on the surface.

6. Ion implantation acceleration electric field 80 keV, dose amount lXl0” ions/c
Under the conditions of ``1'', 1''
Inject ions.

7. Grow a Si, N, film (9) with a thickness of 500A using an out-diffusion prevention film type vacuum vapor phase growth apparatus. After that, in a nitrogen gas atmosphere,
C. and 30 m1n to make the ion-implanted polysilicon layer (8) the same conductivity type and high conductivity as the contact region (2). Furthermore, after annealing, Si,
N. Remove film (9).

8. AI sputtering An AI (aluminum) film (11) with a thickness of 0.8 μm is formed using an AI sputtering device.

9. AI etch photolithography and AI etching leave an aluminum wiring area (11). 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 SilN film on the side wall of the contact hole prevents impurity diffusion from BPSG and lateral diffusion during annealing, thereby reducing the conductivity of the polysilicon buried layer. Deterioration is prevented.

Further, the out-diffusion prevention film prevents out-diffusion of impurities during annealing, thereby preventing formation of a Schottky barrier and reduction in conductivity at the interface between the aluminum wiring region and the buried polysilicon layer.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a manufacturing process flow explaining the present invention in detail, Fig. 2 is a cross-sectional view showing a manufacturing process flow explaining a conventional technique, and Fig. 3 is a cross-sectional view showing a reduction in interfacial impurity concentration due to annealing. It is a diagram. DESCRIPTION OF SYMBOLS 1... Wafer 2... Contact area, 3... SO2 film,... BSG, 6... Contact hole, 7. 9...S3N (film, 1...A (aluminum)

Claims (2)

[Claims] (1) Si_3 on one side of the wafer including the inner surface of the contact hole
A process of growing the N_4 film, an anisotropic etching process that leaves only the Si_3N_4 film on the side walls of the contact hole, a process of forming a polysilicon layer on one side of the wafer and filling the contact hole with this polysilicon, a process of removing the polysilicon inside the contact hole. a step of isotropically etching the polysilicon layer leaving only the silicon layer; a step of ion-implanting impurities into the polysilicon layer within the contact hole; a step of annealing the ion-implanted region after forming an out-diffusion prevention film; 1. A method for manufacturing a semiconductor device, comprising the steps of: forming an Al film after removing the protective film; etching the Al film to leave an aluminum wiring region. (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.