JPH02239620A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To machine a Cu thin-film finely by heating the temperature of a substrate at 250 deg.C or more and conducting reactive ion etching (RIE) by using a gas containing carbon and chlorine. CONSTITUTION:A silicon oxide film 4 is grown on a semiconductor substrate 2 composed of silicon, a Cu thin-film 6 is deposited onto the film 4, a silicon oxide film 8 is formed onto the thin-film 6, and resists 10 are shaped, Cl included in the reaction gas of RIE reacts with Cu at that time, and CuCl2 (a copper chloride) is formed on the surface of the Cu thin-film 6 on the substrate 2, but a substrate temperature is set at 250 deg.C or more in this case, thus desorbing CuCl2 formed, then accelerating etching. Since 6 included in the reaction gas has action in which the sidewall of the Cu thin-film 6 exposed by etching at the same time as the progress of the etching of the Cu thin-film 6, the Cu thin- film 6 is etched vertically. Accordingly, the fine wiring layer of the Cu thin-film 6 can be formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device by etching a copper (hereinafter referred to as Cu) thin film deposited on a substrate. Regarding the method. 3. Detailed Description of the Invention [Summary] This invention relates to a method of manufacturing a semiconductor device, particularly a method of manufacturing a semiconductor device in which a copper thin film adhered to a substrate is etched, and anisotropic etching of a copper thin film is performed to produce a semiconductor device [conventional method]. [Technology] In recent years, as semiconductor devices have become more highly integrated, interconnections have become increasingly finer. At the same time, electromigration and stress migration in Aj (aluminum) or AJ alloys such as AjCu or AjSi, which have been widely used as electrode wiring materials, have become a problem. Therefore, Cu is attracting attention as a wiring material that has excellent resistance to electromigration and stress migration. By the way, Cu is a difficult material to etch. This is because copper bromide and copper chloride are generated during etching using a bromine gas such as HBr or a chlorine gas such as CCj4, but etching does not proceed due to their low vapor pressure. are doing. For example, as shown in FIG. 3, CCj . Cu was deposited on the semiconductor substrate 2 through silicon oxide WA4 by the RIB (reactive ion etching) method using
Even if an attempt is made to selectively etch the thin film 6 using the patterned silicon oxide II$8 as a mask, CuCj 214 is generated on the exposed surface of the Cu thin film 6 at room temperature, thereby inhibiting the progress of etching. For this reason, conventionally, as shown in Figure 4,
The Cu wiring layer was formed by ion milling using Ar (argon) gas. That is, the Cu thin film 6, which is masked by a silicon oxide film 8 patterned in the same manner as shown in FIG. 3, is bombarded with neutral Ar atoms 16 to physically scrape it off.

However, in this ion milling method, as is clear from FIG. 4, the 6ftlJ wall of the Cu thin film is not etched vertically but takes on a tapered shape. Therefore, etching is difficult in areas where the wiring spacing is narrow, and there is a risk of short-circuiting, as shown in section A, for example. In this way, CuffM46 by ion milling method
It was difficult to form a fine wiring layer depending on the etching method. Another problem is that the etching rate is slow. In addition, for RIE of Cu film, 5 m
It has been reported that etching was performed using Torr Ar/5m TOrr CCJ 4 at a temperature of 225°C (G.C. Schwartz a
ndP. M, Schaible, J of Ele.
ctrochei. Soc. , Vol. 130, No.
8, 1777, (1983)》. However, according to the inventor's experiments, at a temperature of 225°C, CuCj2 generated on CuW4 does not separate, and C
It was not possible to perform uH etching. [Problems to be Solved by the Invention] As described above, although the Cu thin film has excellent electromigration resistance and stress migration resistance, it has the problem that it is difficult to properly etch it. There is. That is, finding an appropriate etching method has been a challenge for utilizing Cu thin films as wiring materials for semiconductor devices.

Therefore, an object of the present invention is to provide a method for manufacturing a semi-drying film that can be used as a wiring material for semiconductor devices by anisotropically etching a Cu thin film. [Means for Solving the Problem] The above problem is to provide a method for manufacturing a semiconductor device in which a thin copper film deposited on a substrate is etched.
This is achieved by a method for manufacturing a semiconductor device characterized by heating to 50° C. or higher and performing reactive ion etching using a gas containing carbon and chlorine. [Function] In the present invention, CJ (chlorine) contained in the RIH reaction gas reacts with Cu, and CuCj2 is formed on the surface of the Cu thin film on the substrate.
(Copper chloride) is generated, but at this time the substrate temperature is
By setting the temperature above 0°C, this generated CuC
j2 separates and etching progresses. In addition, as the etching progresses on the Cu thin film, C (carbon) contained in the reaction gas is removed from the Cu exposed by the etching.
The Cu thin film is etched vertically to protect the sidewalls of the thin film. [Example] The present invention will be specifically described below based on an illustrative example. FIG. 1 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. For example, on the semiconductor outer substrate 2 made of silicon, the thickness is 400 mm.
Grow 0 silicon oxide WA4.

Then, on this silicon oxide film 4, a Cu thin film 6 with a thickness of 1 μm is deposited by the DC magnetron battering method. Further, on this Cu thin film 6, a silicon oxide film 8 with a thickness of 5,000 wafers is formed by RF bias sputtering. Next, a patterned resist 10 is formed using a phosphorography technique (see FIG. 1(a)). Next, using the resist 10 as a mask, the CF. Silicon oxide 1m using! Patterning is performed by selectively etching 8 (see FIG. 1(b)), and then the resist 10 is removed (see FIG. 1(c)).

Next, the Cu thin film is etched using the patterned silicon oxide film 8 as an etching mask. First, the manufacturing equipment used for this etching will be explained with reference to FIG. The vacuum chamber 20 is equipped with an inflow port 22 through which a reaction gas flows, and an exhaust port 24 connected to a vacuum pump to reduce the pressure inside the vacuum chamber 20. Further, the upper electrode of the vacuum chamber 20 is grounded, and the lower electrode! The poles are connected to RF via matching box 26.
It is connected to an oscillator 28 to generate plasma using high frequency power.

Also, inside the vacuum chamber 20, there is a wafer table 32 on which the wafer 30 is placed, and a quartz plate 3 on which the wafer 30 is fixed.
4 are provided. And this wafer table 3
A heater 36 is installed inside the wafer 2 to heat the wafer 30. Further, a thermocouple 38 and a fluorescent thermometer 40 are provided, and the thermocouple 38 is connected to the wafer table 32.
A fluorescence thermometer 40 measures the temperature of the wafer from a fluorescent material 42 attached to the back surface of the wafer 30 via an optical fiber 44.
It is designed to measure each of the 30 substrate temperatures.
Further, the wafer table 32 is provided with an opening 46 through which gas can be injected or evacuated. CCJI. (carbon tetrachloride) at 20 sccm and N2
(Nitrogen) was flowed for 200 sec, and the internal pressure was 0.014
The pressure is reduced to Torr to generate plasma, and the plasma is heated to a temperature of 350° C. to form a Cu thin film 6 on the semiconductor substrate 2.
The Cu thin film 6 is brought into contact with CCj. Reacts with Cl to form Cu thin rI! ! 6 Generate CuCj2 on the surface. At this time, since the temperature is as high as 350° C., the vapor pressure of CuCJ becomes high and it separates from the surface of the Cu thin film 6. Therefore, the reaction continues and the etching of the Cu thin WA6 progresses. Also, CCJ. C adheres to the side wall of the Cu thin WA6 exposed by etching to form a carbon film 12, so this carbon JI12 acts as a protective film and the Cu thin WA6 side wall is exposed by etching.
The lateral etching of 19!6 does not proceed. Therefore C
Anisotropic etching is performed to vertically etch the U thin film 6 (see FIG. 1(d)). After removing the silicon oxide film 8 serving as an etching mask, the Cu thin film 6 used as a wiring layer is etched. (see FIG. 1(e)).

As described above, according to this embodiment, when the substrate temperature of the semiconductor substrate 2 is heated to 350° C., ccn. By performing RIB using N2, the CuCj* generated on the surface of the Cu thin film 6 is removed, and the etching of the Cu thin WA 6 progresses. It is possible to prevent the etching from progressing in the lateral direction of the Cu thin film 6 by attaching the Cu thin film 6. By performing anisotropic etching in this manner, the Cu thin WA6 can be microfabricated. By using the Cu thin WA6 thus formed as a wiring layer with a submicron pattern, it is possible to achieve high integration of semiconductor devices having wiring layers with excellent electromigration resistance and stress migration resistance, and it is possible to achieve industrial It will be extremely useful. In this example, the substrate temperature was set to 350°C.
However, any temperature that is sufficient to separate CuCj2 from the surface of the Cu thin [l6] is sufficient. According to the inventor's experiments, this requires a temperature of 250°C or higher. And above temperature 3
The best results were obtained at 50°C. Furthermore, although there is no particular upper limit to this temperature, it is desirable that it be around 450°C, considering the effect on the semiconductor device. In addition, CCj. and N2 were used, but CCj . For example, instead of CF. Any gas containing carbon and chlorine, such as a mixed gas of N and Cj1, may be used, and other inert gases may be used instead of N. However, Ar
N2 has the advantage that it does not have such an adverse effect, whereas N2 damages the exposed base of the Cu thin film. [Effects of the Invention] As described above, according to the present invention, reactive ion etching using a gas containing carbon and chlorine is performed at a substrate temperature of 250° C. or higher to remove Cu* deposited on a substrate.
By anisotropically etching m, Cuffll
lfiAI [l processing can be performed. This allows Cu, which has excellent resistance to electromigration and stress migration, to be used as a wiring material for semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a manufacturing apparatus used in an embodiment of the present invention, and FIGS. 3 and 4 are respectively FIG. 2 is a diagram for explaining a conventional method of manufacturing a semiconductor device. In the figure, 2... Semiconductor substrate, 4.8... Silicon oxide film, 6... Cu thin film, 10... Resist, 12...・・Carbon film, 14・----・CuCj . , 16...
- Neutral Ar atom, 20... Vacuum chamber, 22... Inlet, 24... Exhaust port, 26... Matching box, 28...・・・
・RF oscillator, 30...Wafer, 32...Wafer table, 34...Quartz plate, 36...Heater, Fig. 2

Claims (1)

[Claims] A method for manufacturing a semiconductor device in which a copper thin film deposited on a substrate is etched, comprising heating the substrate to a temperature of 250° C. or higher and performing reactive ion etching using a gas containing carbon and chlorine. A method for manufacturing a semiconductor device, characterized by performing the following steps.