JPS58204558A - Wiring method - Google Patents

Abstract

PURPOSE:To obtain a good electric contact in an ultrafine electrode window by etching and opening a window at an interlayer insulating film on aluminum wirings with CF4 gas, treating it with O2 plasma, coating high melting point metal on the window, heating it. CONSTITUTION:After an SiO2 film 3 and a photoresist 4 are superposed on aluminum wirings 2 on an Si substrate 1, a window 5 is opened at the film 3 by a reactive sputter etching method of a parallel flat plate with gaseous CF4, fluoride polymer produced at the aluminum on the window 5 is ashed and removed. Then, Ti 6, Al 7 are continuously deposited. Wirings are formed by dry etching of CCl4, with the resist mask, the mask 4 is removed, heated in N2 gas, Ti is diffused in aluminum, the wirings 7 are conducted. According to this configuration, a good electric contact connection can be formed in the ultrafine electrode window.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for multilayer interconnection of integrated circuits, and in particular to a method for obtaining good electrical contact with AI.

A1 is a good Wt conductor next to Au, has good microfabricability, and is inexpensive, so it is used as a wiring metal for semiconductors, integrated circuits, and the like. However, when Al is treated with moisture in the air or water, an alumina layer of several hundred amperes is formed on the surface, and since alumina is non-conductive, contact resistance is large when metals are simply brought into contact. Therefore, in an integrated circuit, an interlayer insulating film S10. By opening through holes in the alumina layer with a buffered hydrofluoric acid solution and forming mulch wiring through high melting point metals such as C, %Ti, Mo, etc., and heat-treating at about 300°C or higher, the high melting point metals will form in the alumina layer. The contact resistance is 1ΩΩ and good conductivity can be obtained even with a small through hole of several μm square.

・However, with buffered hydrofluoric acid solution, the side etching is too thick (not suitable for high integration. Therefore, in order to reduce the side etching and accurately open through holes of several μm square, reactive sputter etching using CF4 gas is used. Although I made an opening and wired it as described above, I found that I could not obtain the same good conduction.Even with heat treatment, the contact resistance decreased slowly and had large variations.In order to ensure the opening, I tried dry etching. This tendency becomes more pronounced as the time increases.

In order to investigate the reason why it is difficult to obtain conductivity, we investigated the A1 surface under the through pole by Auger analysis after dry etching for a long time, and found that F%C was found on the A1 surface.
It was found that there were deposits such as , OlH, etc. At is CF
Since it is not etched by the gas, it is thought that the photoresist used as a mask when opening the 8i0t is reacted and polymerized by the CF4 gas, which is deposited on the At. It appears to be preventing its spread.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a wiring method that can obtain good electrical contact with AI even if the contact area is as small as several μm square.

After forming an A1 wiring on a substrate and forming an interlayer insulating film on the entire surface including the AI wiring, opening a predetermined portion of the interlayer insulating film on the A+ wiring by dry etching using a carbon fluoride gas; A high-melting point metal is applied to the opening by saponium plasma treatment, and wiring is formed.',Ill,',',l.

A wiring method that includes a heating process.

Examples of this @ Ming will be described below with reference to the drawings.

1 to 7 are diagrams for explaining one embodiment of the present invention. As shown in Fig. 1, AI was deposited to a thickness of 0.3 μm on the 8i substrate 1 whose entire surface was covered with a Si nitride film, and CCl4 dry etching was performed using a photoresist film mask.
1 wiring 2 is formed, the photoresist film is removed, and 1fiiO,3 is deposited on the entire surface as an interlayer insulating film with a thickness of 0.
．． A photoresist film 4 with an open pattern 5 of 2 μm square as shown in FIG. 3 is formed by vapor phase growth of 4 μm, and as shown in FIG. 8i0. An opening 5 is provided in J[3, and as shown in FIG. The gas pressure was changed to 200 mtorr.

The fluorinated polymer produced on the photoresist film 4 and the At of the opening 5 is incinerated and removed using a high frequency power of 100 W for about 10 minutes.
As shown in Figure 6, Ti6 and At7 were successively deposited to a thickness of 0.21 μm and 0.5 μm, and as shown in Figure 7,
) Lz &
The wiring can be made electrically conductive by diffusing heat into the t.

The resistance value of 2 μm μm through hole is several tens of Ω before heat treatment.
Although it varies from Ω to Ω, it becomes less than 10 after heat treatment at 350°C for about 15 minutes. As an example of a product heat-treated at 350°C, 100 points per wafer (
The resistance value measured for two wafers was 0.32±0.
．． 12J] (95% distribution limit) Tearing, resistance value, and variation are both extremely small. In addition, when the photoresist film is opened with CF4 and the photoresist film is removed with a stripping solution, the resistance is several ohms to several tens of ohms after heat treatment at 350°C, and heat treatment for one hour or more is required to reduce the resistance to 10 or less. , the through-hole resistance decreases more slowly.

According to the present invention, even if the through hole is as small as 2 μm square, the through hole resistance is 10 or less, and both the resistance value and the variation are small, which is a value that could not be obtained in the past. The effect is clear.

In the examples, CF was used as the carbon fluoride gas, but C
It may be HF, c, ps, C5F'a, etc.

Further, in the embodiment, the oxygen plasma treatment was performed using the same reactive sputter etching to form the openings, but general cylindrical plasma etching may be used.

[Brief explanation of drawings]

1 to 7 are diagrams for explaining in detail the present invention for obtaining electrical contact with AI. In the figure, l is an insulated substrate, 2 is a first layer AI wiring, and 3 is an interlayer insulating film sio.
,, 4 is a photoresist film, 5 is an opening (through hole),
6 is a high melting point metal, and 7 is a second layer AI wiring.

Claims (1)

[Claims] After forming an AI wiring on a substrate and forming an interlayer insulating film on the entire surface including the A1 wiring, opening the interlayer insulating film at a predetermined portion on the AI wiring by dry etching using fluorocarbon thread gas, A wiring method that includes the steps of applying oxygen plasma treatment, depositing a high melting point metal on the opening, forming wiring, and heating.