JP2008244020A - Dry etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining method of a ZnO film having high precision and high safety. <P>SOLUTION: A dry etching method has: a process for performing the pattern formation of resist on a member to be etched made of a substance containing zinc oxide; and a process for etching the member to be etched by gas containing reducing gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for processing a zinc oxide film, and more particularly, to a method for dry etching a zinc oxide film formed on a substrate.

  Zinc oxide (ZnO) has features such that the raw material is inexpensive, harmless to the environment and the human body, and the film forming method is simple. Further, since it is transparent and conductive, it is used as a material for transparent electrodes such as liquid crystal displays.

  The ZnO film is a material whose demand is increasing in this way, and various processing methods have been developed. Conventionally, a wet etching method using an HF aqueous solution or the like has been used for processing the film. This is because it was difficult to adapt to the dry etching method because the ZnO film has the property of being excellent in plasma resistance.

  However, in the processing method using the wet etching method, the etching of the base material isotropically proceeds, and therefore, when the etching depth is deep, an undercut is generated in which the corrosion reaches the lower portion of the resist. As a result, the processing accuracy deteriorates, and there is a problem that it is difficult to perform high-precision fine processing. In addition, the wet etching method has a problem that an equipment such as a water tank filled with an etching solution is required.

  With respect to these problems, Patent Document 1 discloses a dry etching technique for removing a thin film made of ZnO or a substance containing ZnO with HF or a gas containing HF. With dry etching technology, there is no problem of undercutting, fine processing is possible, and processing accuracy is excellent.

  However, the HF gas used in the technology has a problem that it is corrosive and toxic, corrodes a metal and is harmful to the human body. In addition, since the equipment for processing is corrosive to HF gas, there arises a problem that a corrosion-resistant material must be used.

Japanese Patent Laid-Open No. 04-196218

  In view of the above problems, the present invention provides a highly accurate and safe ZnO film processing method.

  The invention according to claim 1 includes a step of patterning a resist on a member to be etched made of a substance containing zinc oxide, and a step of etching the member to be etched using a gas containing a reducing gas. The dry etching method characterized by the above.

  The invention according to claim 2 relates to the dry etching method according to claim 1, wherein the reducing gas is hydrogen gas.

  According to a third aspect of the present invention, the zinc oxide contains an impurity, and the element of the impurity is selected from B, Al, Ga, In, Zn, H, an alkali metal element, or a group IV element such as Si or Ge. 3. The dry etching method according to claim 1, wherein the dry etching method comprises any one of the above or a combination thereof.

  According to the first aspect of the present invention, the method includes a step of patterning a resist on a member to be etched made of a substance containing zinc oxide, and a step of etching the member to be etched using a gas containing a reducing gas. Therefore, it is possible to provide a dry etching method which can be finely processed and is excellent in accuracy, and equipment such as a water tank for etching is not required as in the wet etching method. In addition, since a reducing gas is used for etching, it is possible to provide a dry etching method with higher safety as compared with fluorine gas having high corrosiveness.

  According to the second aspect of the present invention, since the reducing gas is hydrogen gas, there is no corrosiveness and no toxicity to the human body, so that a highly safe dry etching method can be provided.

  According to the invention of claim 3, zinc oxide contains an impurity, and the element of the impurity is selected from B, Al, Ga, In, Zn, H, an alkali metal element, or a group IV element such as Si, Ge. Therefore, the conductivity of the zinc oxide film can be effectively improved, and the stability of the zinc oxide crystal system can be expected.

  Hereinafter, preferred embodiments of the dry etching method according to the present invention will be described. FIG. 1 is a schematic process diagram showing the steps of the dry etching method according to the present invention. As an object of the dry etching method according to the present invention, for example, a substrate with a ZnO film in which a ZnO film 2 is formed on a substrate 1 as shown in FIG.

  The material of the substrate 1 can be arbitrarily selected from metals, alloys, ceramics, plastics, and the like that are generally used as substrates in the fields of the electronics industry, the printing plate manufacturing field, the mechanical micromachining field, and the like. Examples thereof include aluminum, tungsten, titanium, cobalt, iron, silicon and alloys thereof, silicon nitride, gallium-arsenic, titanium oxide, silicon oxide, glass and the like, and silicon is particularly preferably used.

The ZnO film 2 formed on the substrate 1 is a member to be etched, is substantially transparent to visible light, and is a relatively inexpensive material. The ZnO film 2 can contain impurities.
Hereinafter, the ZnO film 2 made of zinc oxide containing impurities will be described. The impurities described here are for controlling the properties of ZnO as a semiconductor. More specifically, impurities are added to the semiconductor in a predetermined amount for the purpose of controlling the conductivity type, electrical resistance, etc. of the semiconductor. . Hereinafter, adding an impurity to a semiconductor (zinc oxide) is referred to as doping.
As the impurity element doped into the ZnO film 2, any one selected from B, Al, Ga, In, Zn, H, an alkali metal element, a group IV element such as Si, Ge, or a combination thereof is used. It can be suitably used. Thereby, electrons (carriers) that can move freely in the crystal of the ZnO film 2 are formed. Thus, by doping, the improvement of conductivity and the stability of the crystal system of zinc oxide due to weather resistance can be expected.

  FIG. 1B shows a state in which the resist 3 is patterned. As shown in FIG. 1B, a resist 3 is applied on the ZnO film 2, and the resist 3 is patterned by an electron beam drawing method.

  FIG. 1C is a view showing a state where the ZnO film 2 is dry etched by the dry etching method according to the present invention. As shown in the figure, the portion of the ZnO film 2 that is not covered with the resist 3 is removed and etched according to the pattern of the resist 3. As an apparatus for performing dry etching, any apparatus can be used as long as it is a heat treatment apparatus capable of atmospheric gas replacement. An object to be etched is placed in the chamber of the apparatus, and hydrogen gas, which is a reaction gas, is sent into the member to be etched. As the flow rate of this hydrogen gas, a small amount of several sccm (550 to 700 ° C.) is sufficient. Moreover, the temperature in hydrogen gas atmosphere is 650 degrees C or less, Preferably, it is 550-650 degreeC. The etching time varies depending on the temperature, but for example, it is performed at 600 ° C. for 1 to 2 minutes. The etching time can be adjusted by temperature, the flow rate of hydrogen gas, and the like.

FIG. 2 is a graph showing changes in the resistance value of the ZnO film in a hydrogen atmosphere and an air atmosphere.
In the figure, the vertical axis represents the resistance value of the ZnO film, the horizontal axis represents the temperature in the atmosphere, the black square in the figure represents the resistance value in a hydrogen atmosphere, and the black circle represents the resistance value in an air atmosphere. Show. The resistance value of the ZnO film in a hydrogen atmosphere is constant up to around 400 ° C., and increases rapidly at 550 ° C. or higher. The resistance value is not described above 650 ° C. This is because the resistance value could not be measured because the ZnO film sublimated completely when it exceeded 650 ° C. and no longer existed. Thus, it was confirmed that the ZnO film began to sublime at 550 ° C. to 650 ° C. in a hydrogen atmosphere. On the other hand, although the resistance value of the ZnO film at 650 ° C. or higher in an air atmosphere increased rapidly as the temperature rose, the film was present and the resistance value could be measured. From this, it was found that the ZnO film does not sublime in an air atmosphere even at 650 ° C. or higher.

  The ZnO film processing method according to the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of the gist.

Hereinafter, an example is given and the dry etching method concerning the present invention is explained in full detail.
First, a ZnO film is formed on the surface of a glass substrate. For the film formation, a ZnO sintered body containing 4 wt% gallium (Ga) as an evaporation raw material was used.

First, in a vacuum chamber of the film forming apparatus, a glass substrate was held by a holding member, and a Ga4 wt% -containing ZnO sintered body was loaded in a hearth.
Next, the inside of the vacuum chamber is evacuated to a vacuum degree of 10 ⁻⁷ torr (1.33 × 10 ⁻⁵ Pa), the glass substrate is raised to 200 ° C. with a heater, and then transferred at a speed of 2.3 mm / sec. Was started.
Subsequently, a plasma beam was generated from a plasma gun using a pressure gradient type dc arc plasma, and this plasma beam was incident directly on the hearth by a magnet ring provided around the hearth.
Through the above steps, the ZnO sintered body containing Ga 4 wt% was sublimated, and a ZnO film was formed on the glass substrate.

  Next, a resist was applied on the formed ZnO film, and this resist was patterned by an electron beam drawing method. Dry etching was performed on the patterned substrate with the ZnO film under the following conditions.

Various conditions for dry etching are shown below.
Etching gas: Hydrogen gas 99.999% or more Gas flow rate: 0 to 200 sccm (600 ° C.)
Temperature: 650 ° C
Process pressure: Atmospheric pressure or Etching time under reduced pressure at atmospheric pressure: 3 minutes The case where the gas flow rate is 0 sccm is when the substrate with the ZnO film is sealed with hydrogen gas for processing.

  As a result of dry etching under the above conditions, the etching process proceeded by sublimation of ZnO in a hydrogen gas atmosphere. Thereby, the ZnO film was etched according to the resist pattern.

  In the above embodiment, dry etching was performed at 650 ° C. for 3 minutes, but the etching time is appropriately adjusted in accordance with the etching target in the range of 30 seconds to 5 minutes. Moreover, it is also possible to carry out on the conditions of 600 degreeC and 1-2 minutes. Further, it can be carried out at 550 ° C. for 3 hours. Moreover, although the case where the glass substrate was used was demonstrated in the said Example, it is not limited to this in this invention, A silicon substrate, a plastic substrate, etc. can be used similarly.

  As described above, according to the present invention, a highly safe dry etching method for a ZnO film can be provided. Further, there is no deterioration in accuracy as in the wet etching method, and facilities such as a water tank are not required.

  The present invention can be suitably used when performing various types of processing of a ZnO film.

It is a schematic process drawing which shows the process of the dry etching method which concerns on this invention. It is the figure which showed transition of the resistance value of the ZnO film | membrane in a hydrogen atmosphere and an air atmosphere.

Explanation of symbols

1 Substrate 2 ZnO film 3 Resist

Claims (3)

Patterning a resist on a member to be etched made of a substance containing zinc oxide;
And a step of etching the member to be etched using a gas containing a reducing gas.   The dry etching method according to claim 1, wherein the reducing gas is hydrogen gas.   The zinc oxide contains an impurity, and the element of the impurity is selected from B, Al, Ga, In, Zn, H, an alkali metal element, a group IV element such as Si, Ge, or the like. The dry etching method according to claim 1 or 2, comprising a combination.

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