JPH0371657A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a contact of a small diameter and a large height in electrical property by a method wherein impurity ions are implanted into polysilicon in a contact hole, a barrier metal film is formed, moreover an Al film is formed, and an aluminum wiring region is left by etching the Al film and the barrier metal film. CONSTITUTION:A contact hole 6 is filled with polysilicon, only a polysilicon 8 inside the contact hole 6 is left, impurity ions are implanted into the polysilicon 8 in the contact hole 6. Then, a barrier metal film 10 is formed, an Al film 11 is formed, and in succession an aluminum wiring region is left through the etching of the Al film 11 and the barrier metal 10. Thereby, the diffusion of impurity from a boron phosphorus silicate glass(BPSG) 4 and the lateral diffusion at annealing can be prevented by an SiN film 7 formed on the side wall of the contact hole 6, and the solid solution reaction of the Al 11 with the buried polysilicon layer 8 is prevented by the barrier metal 10. By this setup, the aluminum wiring region of a contact section and a polysilicon layer can be prevented from decreasing in conductivity.

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.In a simple contact method using Al sputtering, Al An increase in contact resistance due to a decrease in film thickness, and furthermore, disconnection of Al wiring at step portions is becoming unavoidable.For this reason, a contact method has been developed in which polysilicon is buried in the contact hole prior to Al wiring to improve step coverage. is proposed.

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), which uses a 30ooAW-S
In, film (23), BPSG (boron phosphorus silicate glass, hereinafter referred to as BPSG) with a thickness of 5 mm is formed on the top surface using an atmospheric vapor phase growth apparatus (
The manufacturing process of the bono silicon 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) A contact hole (26) of 0.8 μm Xo, 8 μm, and 1.1 μm deep is opened in the upper surface of the contact region (22) previously formed.

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
The polysilicon (27) is etched and packed as shown in the figure so that only the polysilicon layer (27) inside the contact hole (26) is left behind.

1. After ion implantation of phosphorus ions into the ion-implanted polysilicon layer (27), it was heated at 900°C for 30 minutes in a nitrogen gas atmosphere.
m1n is annealed to have the same conductivity type as the contact region (22) and high conductivity.

5. Al sputtering An Al (aluminum) film (28) of 0.8 μmJv is formed using an Al sputtering device.

6. A1 etch photolithography and Al etching leave an aluminum wiring area (28). Thereafter, 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.

As a result of research conducted by the inventors on this point, the impurity of the opposite conductivity type, boron, is diffused from the BPSG (24) into the bono silicon layer (27) during annealing in Process 4, and is compensated to form the porin 13 layer. The conductivity of the layer (27) decreases, and the polysilicon layer of the aluminum interconnection region (28) and contact hole (26) decreases during annealing in process 6 due to the fact that about one film of Si, which is mixed into Al for other purposes, decreases. (27) and Si nodules (no
It has been clarified that the conductivity of the Al wiring region (28) and the polysilicon layer (27) is reduced.

(...) Problems to be Solved by the Invention The present invention is based on the elucidation of the above-mentioned causes of problems existing in conventional technology, 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 provides a method for solving the problems by forming a
Step of growing isN4 film, S on contact hole side wall
an anisotropic etching step that leaves only the isN4 film;
A process of forming a polysilicon layer on one side of the wafer and filling the contact hole with this polysilicon, a process of isotropically etching the polysilicon layer leaving only the polysilicon in the contact hole, and a process of adding impurities to the polysilicon in the contact hole. This process consists of a series of steps including ion implantation, forming a barrier metal film, forming an Al film, and etching the Al film and barrier metal film to leave an aluminum wiring region.

(,1) The step of covering the side wall of the working contact hole with a Si3N film prevents impurity compensation in the polysilicon layer due to diffusion of impurities of the opposite conductivity type from the BP SG to the buried polysilicon layer. In addition, the process of forming the barrier metal film prevents the solid solution reaction between the Al of the SIJ and the buried polysilicon, reduces the relative impurity concentration of the polysilicon, and reduces the Si nodules in the A1 film and the buried polysilicon layer. Nodule).

(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 nine 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
000-person thick Sins film (3), this SiO2 film (3)
A 0°8 μm x 0.8 insulating film of 8,000 thick poly PSG (4) was formed on the top surface using an atmospheric vapor deposition apparatus using photonography and oxide film etching.
A contact hole (6) with a thickness of 1.1 μm and a depth of 1.1 μm is made.

Note that region (2) is a highly doped contact region specially formed for contact.

2. Si, N, film deposition Si, N, film deposition 50 degrees thick on the entire surface of the wafer (1), including the sidewalls of the contact holes (6), using a low pressure vapor phase epitaxy growth apparatus.
Grow a N4 film (7).

3.5 isN+ Film Etching Anisotropic etching is performed by dry etching such as active ion etching, leaving only the S isN 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, polysilicon (8) is placed so that S i O eyes Jj (5) appear on the surface.
is etched back.

6. Ion implantation acceleration electric field 80 keV, dose amount lXl0” ions/
"Phosphorus" ions are implanted into the polysilicon layer (8) under the condition of "cm".

7. In Figure 1 (7) explaining the barrier metal sputter manufacturing process, a single-layer barrier metal (11) is shown, but a 500λ thick Ti (titanium) film formed by sputtering, and It is preferable to have a two-layer structure such as a 1000-layer thick TiN (titanium nitride) film or TiW (titanium tungsten) film formed on the upper surface.

8. Form an Al (aluminum) film (11) with a thickness of 0.8 μm using an A1 sputtering Al sputtering device.

9. Al and barrier metal etch Photonography and Al and barrier metal etching leave an aluminum wiring region (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 SiBN 4 film on the side wall of the contact hole prevents impurity diffusion from BPSG and lateral diffusion during annealing, thereby improving the conductivity of the polysilicon buried layer. This prevents a decrease in

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 drawings]

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. 1... Wafer 2... Contact area, 3.
...Sio, film, 4...BPSG, 6...contact hole, 9...Si, N4 film, O...barrier metal, 11...Al (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 silicon, a step of ion-implanting impurities into the polysilicon in the contact hole, a step of forming a barrier metal film, a step of forming an Al film, an Al film and a barrier metal film. 1. A method of manufacturing a semiconductor device, comprising the step of leaving an aluminum wiring region by etching. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the step of forming the barrier metal film is a step of forming a Ti film and a TiN film or a TiW film formed on the top surface of the Ti film.