JPS5927406A - Method of forming thin film by sputtering - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a method of forming a thin film by sputtering,
Indium oxide (IngO) has particularly low resistance film characteristics.
The present invention relates to a method for forming a transparent conductive film based on a) by sputtering with good reproducibility.

(b) Prior Art and Problems Conventionally, a method using reactive sputtering has been used to form a transparent conductive film made of indium oxide (Inρa) or tin oxide (In, 08, etc. to which about 1 to 10% of 8nO- is added). This formation method involves mixing several lθ% of an inert gas such as argon (Ar) and oxygen (O8) gas, and placing a metal made of an In-8n alloy for the cathode in the mixed gas atmosphere. A target and a substrate mounting table serving as an anode supporting a substrate to which a transparent conductive film is to be applied are placed facing each other, and the substrate surface is covered with a shutter first.
In this state, a predetermined discharge pressure is applied between both electrodes to perform press spattering to knock out the adsorbed residual gas on the electrodes and vessel walls to maintain the purity of the discharge gas. A transparent conductive film mainly composed of In and 08 is deposited on the substrate by sputtering.

However, in the method of forming a transparent conductive film by reactive sputtering as described above, the surface of the metal target is oxidized during sputtering, and 1r,,o, are formed. Since the surface oxide layer is formed thickly, only the oxide layer on the target surface is sputtered at a low group N voltage, and the sputtered film is formed with high resistance. Therefore, when the discharge voltage is increased to a certain extent, the target metal is sputtered together with the oxide layer, and the sputtered film becomes insufficiently oxidized and is formed to have a low resistance, but there is a phenomenon in which the transmittance decreases. Therefore, in order to form a transparent conductive film with low resistance and good transmittance, sputtering conditions are limited to a very narrow range between the above two sputtering condition ranges, and this sputtering condition is limited to the oxidation of the target surface. Since it is necessary to change the sputtering conditions depending on the conditions, there is a drawback that the transparent conductive film cannot be obtained with good reproducibility using the same sputtering conditions.

A transparent conductive film originally made of InBOl or the like uses electrons from the donor level due to oxygen vacancies in the film to contribute to conduction as carriers, so a transparent conductive film formed by sputtering is not a complete oxide film. However, there is a problem that low resistance cannot be obtained unless there is a certain degree of oxidation deficiency, and if there is excessive oxidation deficiency, the transmittance decreases, and the film properties of both low resistance and transmittance are There is a need for a method that can easily and reproducibly obtain a transparent conductive film that satisfies the following requirements.

(C) Purpose of the Invention In order to overcome the above-mentioned conventional drawbacks, the present invention focuses on the fact that the surface condition of the metal target at the initial stage of sputtering greatly affects the sputtering conditions. To provide a novel method for forming a thin film that can stably and reproducibly form a transparent conductive film having film characteristics of low resistance and good transmittance by once keeping the surface state clean and free of oxides. (d) Structure of the Invention According to the present invention, a metal target serving as a uniform electrode body in a container containing a predetermined gas, and the other metal target disposed opposite to the metal target. A required sputtering voltage is applied between the electrode body and the substrate mounting table supporting the substrate, and the surface of the metal target is sputter etched in advance before depositing a thin film on the substrate by sputtering. This is achieved by providing a method for forming a thin film by sputtering, which is characterized in that a clean metal surface is exposed.

(e) Examples of the invention Examples of the forming method according to the invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of a reactive sputtering apparatus applied to the method of forming a thin film by sputtering according to the present invention. In the figure, l is a base that communicates with an exhaust system such as a vacuum pump (not shown) through its exhaust hole 2, and a removable Pelger-type container 8 is mounted on the base 1 to form an airtight chamber. are doing. Moreover, in the container 8,
For example, a metal target 4 that is an alloy of In and 8N in a predetermined ratio and serves as a cathode, and a substrate 6 to which a transparent conductive film is to be deposited.
A substrate mounting table 5 serving as an anode supporting the substrates is arranged parallel to each other and facing each other. 7 is an Ar gas introduction pipe for introducing high-purity argon (Ar) gas into the container 8 via a pressure reducing valve, and 8 is also a reactive gas, for example, an inert gas such as Ar gas and oxygen gas of about several 10%. This is a reactive gas introduction pipe that introduces mixed reactive gases. In order to form a transparent conductive film mainly made of In808 on the substrate 6 using such an apparatus, first, the inside of the container 8 is evacuated to a predetermined degree of vacuum, and then the Ar gas introduction tube 7 is High purity argon gas is introduced and the shutter 9 is closed.
By applying a predetermined discharge voltage between the metal target 4 and the metal target 4 to perform sputtering, the surface of the metal target 4 is etched, and oxides, Inρ8, etc. formed on the surface of the metal target 4 are removed, resulting in a clean metal surface. expose. Next, after exhausting the Ar gas in the container 8, the reactive gas is introduced from the reactive gas introduction pipe 8, and the conventional press sputtering is performed to knock out the impurity adsorbed residual gas in the container 8 and cause a reaction. It maintains the purity of the gas and stabilizes the discharge voltage. After that, the shutter 9 is opened and a predetermined amount of air is released from the DC power source 10 between both electrodes. ! By performing main sputtering by applying pressure, a transparent conductive film having desired film characteristics can be easily formed on the substrate 6 on the anode side without changing the gas pressure of the reactive gas or sputtering conditions such as discharge voltage. A membrane can be applied. Figure 2 shows the release rate in the above sputtering process. ! It is a diagram showing changes in pressure. First, a predetermined discharge voltage is applied to high-purity Ar.
When the surface of the metal target 4 is sputter-etched with gas, as the oxide film on the surface of the target 4 is removed, the discharge voltage increases as shown by curve C, and the original constant number 1N [A value of pressure] of the metal target 4 increases. become. By continuing to perform pre-sputtering under the condition of such a steady discharge voltage, a uniform thin oxide film is formed on the surface of the target 4, and secondary electrons are emitted from the oxide film, so that the discharge voltage is indicated by a curve. and stabilized at the B value. When such a discharge voltage state is reached, the predetermined discharge %1IEil! By performing the main sputtering using pressure, a transparent conductive film having desired film characteristics can be deposited on the substrate by a stable discharge voltage as shown by curve E. Therefore, as mentioned above, before each sputtering, the surface of the metal target 4 is sputter-etched, and the surface of the metal target 4 is always kept in a clean state with no oxide film at the start of sputtering, thereby reducing the resistance and increasing the transmittance. It becomes possible to form a transparent conductive film with good reproducibility under the same sputtering conditions.

(f) Effects of the Invention As is clear from the above explanation, according to the method for forming a thin film by sputtering according to the present invention, sputtering is performed with the surface of the metal target always kept in a clean state without oxidation at the initial stage of sputtering. Therefore, a thin film made of a transparent conductive film with desired film characteristics can be easily formed under the same sputtering conditions without changing the sputtering conditions.
Moreover, it has the advantage that it can be formed with good reproducibility, and the manufacturing yield of the thin film is significantly improved. Furthermore, the present invention is extremely advantageous in application not only to the formation of transparent conductive thin films made of 1n1108 etc. as explained in this embodiment, but also to the formation of thin films such as various metal oxide films by sputtering using a metal target. It produces excellent effects.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view showing an embodiment of an apparatus applied to the method of forming a thin film by sputtering according to the present invention, and FIG. 2 is a discharge discharge during the period from sputter etching to main sputtering in the sputtering process according to the present invention. FIG. 3 is a diagram showing changes in voltage. In the drawing, 1 is a base, 3 is a Pelger type container, 4 is a metal target, 5 is a substrate mounting table, 6 is a substrate, 7 is a high-purity argon gas introduction tube, 8 is a reactive gas introduction tube, and 9 is a shutter. show. Representative Patent Attorney Sada Igata - Figure 1 Figure 2 → Gin 1'1il (minute)

Claims (1)

[Claims] A required sputtering voltage is applied between a metal target serving as 10,000 electrode bodies in a container containing a predetermined gas and a substrate mounting table supporting a substrate serving as the other electrode body placed opposite to the metal target. A method for forming a thin film by sputtering, characterized in that, before depositing the thin film on the substrate by sputtering, the surface of the metal target is sputter etched in advance to expose a clean metal surface.