JPS61111525A - Forming method for electrode of semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a tungsten silicide gate electrode for MESFET, which is low resistivity and favorable stability, adhesive, property chemical resistance, accuracy of forming pattern, reliability etc. at high temperature, by a method wherein a metallic alloy film is formed by means that simultaneous spattering to substance of metallic alloy is performed and negative bias is impressed to a semiconductor substrate at the time of spattering. CONSTITUTION:A tungsten target 1 and an Si target 2 are prepared and are impressed with voltage of target bias electrode 6, 6' respectively. A holder 4 is impressed at -10-50V voltage from a holder bias power supply 5. In such a manner, an adhered tungsten silicide film, whose film resistivity is about 20muOMEGAcm, is favorable, and the said film stress is very small tensile stress less than 2X108N/m<2>, then film exfoliation is not happened at all, so warpage of a wafer 3 is small too. Subsequently, an electrode pattern is formed by active ion-etching. In this case, accuracy of forming a photo-resist mask is improved, thus about 1mum thickness electrode pattern is formed accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming an electrode of a semiconductor device, and particularly to a method for forming a high melting point metal alloy electrode.

[Conventional technology]

Refractory metal alloys have properties such as relatively low bulk resistivity, stability at high temperatures, and chemical resistance, so they are used as materials to replace polysilicon in silicon MOS devices, and as materials such as aluminum in GaAs MES devices. As an alternative material, it is beginning to be used as a material for gate electrodes. Film forming methods for high melting point metal alloys for electrode applications include methods such as the blowfish method and chemical vapor deposition method (CVD method).

Among these methods, the simultaneous vapor deposition method has the disadvantage that the step coverage of the film is poor and the electrode is easily broken, and the CVD method has not been used for a long time since its equipment was developed, so it is not generally used. The sputtering method is common.

However, when using an alloy target in the sputtering method, impurities tend to enter during the target manufacturing process, resulting in problems such as increasing the resistivity of the film and reducing device reliability due to radioactive impurities. However, there is a problem in the controllability of the alloy composition ratio of the film. On the other hand, the simultaneous sputtering method makes it possible to manufacture highly pure alloyed metal targets, so there is almost no influence from impurities, and the alloy composition ratio of the film can be easily controlled, making it the most promising application for forming electrodes in semiconductor devices. However, since a large amount of sputtering gas (usually argon) is incorporated into the film, film stress increases. If this film stress is large, especially if it is equal to or greater than the adhesion force of the film, the film may peel off or the substrate may warp, which becomes an obstacle when forming an electrode pattern using normal phosphorography technology. This may cause a decrease in pattern accuracy or even deformation of the substrate. actually,
A tungsten-silicide film with a film thickness of 400A formed by simultaneous sputtering has a thickness of 5 x 10"N/TF?
A certain amount of tensile stress is generated, and the membrane stress is close to the limit of membrane peeling.

[Problem that the invention seeks to solve]

An object of the present invention is to solve the above-mentioned problem that the film stress of a high melting point metal alloy film increases due to simultaneous sputtering,
The object of the present invention is to provide a method for forming electrodes for semiconductor devices, which has low specific resistance, and has good stability at high temperatures, adhesion, chemical resistance, pattern formation accuracy, reliability, etc.

[Means for Solving the Problems] The structure of the present invention is that, in a method for forming an electrode of a semiconductor element having an electrode of a high-melting point metal alloy, constituent materials of the metal alloy are simultaneously sputtered and sputtering is performed on a semiconductor substrate during sputtering. The method is characterized in that the film of the metal alloy is formed by applying a negative bias.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

As an embodiment of the present invention, MESFET tungsten
A method for forming a silicide gate electrode will be described.

First, tungsten silicide is deposited by simultaneous sputtering on the entire surface of a wafer in which an N9 active layer is formed on a GaAs semi-insulating substrate. In the case of conventional simultaneous sputtering, sputtering is performed with the wafer set in a holder kept at ground potential. For this structure,
It has been experimentally confirmed that the film stress of a tungsten silicide film deposited on a wafer exhibits strong tensile stress. Argon gas trapped in the film is thought to be the cause of this stress, so we investigated the film stress when the holder potential was changed, and found that the film stress was has become almost zero.

FIG. 1 is a schematic diagram of a simultaneous sputtering apparatus used in an embodiment of the present invention. In the figure, the holder bias power supply 5, which is the main feature, can apply a voltage of -1OV to -30V to the holder 4. GaAs MES F
Examples of conditions for simultaneous tungsten and silicide sputtering for gate electrode applications in ET include the following conditions. Argon gas pressure is 10□T or rs Sputtering rate of tungsten and silicon is 5:3, holder bias is -2Ov, film thickness is 5ooof The tungsten silicide film deposited under conditions of 0 or more has a layer resistivity of Approximately 20 μΩ steel and good membrane stress of 2 x 10”N
With a very small tensile stress of /yj or less, there is no peeling of the film and the warping of the wafer 3 is small. Next, using the photoresist as a mask, an electrode pattern is formed by 8F gas paste active ion etching. In this case, since the warpage of the wafer 3 is small, the photoresist mask formation accuracy is good, and an electrode pattern of about 1 μm can be formed with high accuracy.

In FIG. 1, a tungsten target 1 and a silicon target 2 are prepared, and voltages from target bias power supplies 6 and 6' are applied to them, respectively. Furthermore, an exhaust pump 7 and an argon gas inlet 8 are provided.

〔Effect of the invention〕

As explained above, according to the present invention, the effect of reducing the film stress of the metal alloy film can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a high melting point metal alloy simultaneous sputtering apparatus used in an embodiment of the present invention. In the same figure, 1...Tungsten target, 2...Silicon target, 3...
...Semiconductor element wafer, 4...-Wafer holder, 5...Holder bias power supply, 6...
・Target Φ bias power supply, 7...-exhaust pump, 8...Argon gas inlet. Agent Patent Attorney Uchihara Voice slip T”:i’:S,
・l Figure 1

Claims (1)

[Claims] In a method for forming an electrode of a semiconductor device having an electrode of a high melting point metal alloy, constituent materials of the high melting point metal alloy are simultaneously sputtered, and a negative bias is applied to the semiconductor substrate during sputtering to form a film of the high melting point metal alloy. 1. A method for forming electrodes of a semiconductor element, the method comprising: forming an electrode of a semiconductor element;