JP2008179850A - Method and apparatus for depositing amorphous ito film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for depositing an amorphous ITO film by which occurrence of fine crystals is suppressed. <P>SOLUTION: A substrate W is tightly fitted on a stage 3 by a clamp 4 during the film deposition of an amorphous ITO film M. In this state, a refrigerant G is circulated around the substrate stage 3 by a refrigerant circulating means 5 to cool the substrate W to the temperature below the room temperature of a vacuum chamber 2. Thus, it is possible to suppress the occurrence of fine crystals inside the amorphous ITO film M due to the temperature rising of the substrate W. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an amorphous ITO film forming method and an apparatus for forming an amorphous ITO film on a substrate by sputtering.

Conventionally, for example, in a liquid crystal cell (TFT liquid crystal element) used in a liquid crystal display device as a display device, an ITO film which is a transparent electrode is formed as a pixel electrode on a light-transmitting substrate. As such an ITO film, an amorphous ITO film is used as it is, that is, in an as-deposited state. This is because, for example, oxalic acid is used in order to prevent the etching solution from penetrating and damaging the thin film transistor (TFT element) located under the ITO film when the ITO film having a predetermined thickness is subjected to pixel patterning and etching. This is because etching can be performed with a weak acid such as (C ₂ H ₂ O ₄ ).

Such an ITO film is formed by a sputtering method using a sputtering gas having a predetermined pressure in a processing chamber such as a vacuum chamber (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-280127

  However, in the above-described ITO film forming method, microcrystals grow inside as the film thickness increases. This is because the time during which the substrate is exposed to plasma becomes longer with the film thickness, that is, the film formation time, and the substrate surface temperature rises, so that the amorphous ITO film at the substrate interface is polycrystallized to cause microcrystallization.

  Such microcrystals cannot be etched with a weak acid, and when a pixel electrode is etched, a residue of microcrystal aggregates remains in the gaps between pixels, and is electrically connected to an adjacent pixel. Cause continuous bright spots.

  At present, the maximum film thickness at which no residue remains is about 1000 mm, and if there is such a limitation on the film thickness, there is a risk of affecting optical design or prevention of step breakage at contact hole locations. is there.

  The present invention has been made in view of these points, and an object thereof is to provide a method for forming an amorphous ITO film in which generation of microcrystals is suppressed and an amorphous ITO film forming apparatus including the same.

  The present invention is a method for forming an amorphous ITO film on a substrate by sputtering in a processing chamber, wherein the substrate on a substrate stage is placed in the processing chamber during the formation of the amorphous ITO film. It cools below room temperature.

  The present invention also relates to an amorphous ITO film forming apparatus for forming an amorphous ITO film on a substrate by a sputtering method, a processing chamber for forming an amorphous ITO film on the substrate by the sputtering method, and the processing chamber And a cooling unit capable of cooling the substrate on the substrate stage to a room temperature or less in the processing chamber.

  Then, the substrate is cooled to room temperature or lower in the processing chamber while the amorphous ITO film is formed in the processing chamber.

  According to the present invention, it is possible to suppress the generation of microcrystals in the amorphous ITO film as the substrate temperature rises.

  The configuration of the amorphous ITO film forming apparatus according to the first embodiment of the present invention will be described below with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes a film forming apparatus. The film forming apparatus 1 is an insulating substrate as a translucent substrate constituting a liquid crystal display element (liquid crystal cell, TFT element) used in a liquid crystal display device or the like. For example, it is a DC magnetron type sputtering apparatus in which an amorphous ITO film M to be a pixel electrode of a liquid crystal display element is formed on a substrate W such as a glass substrate.

  In the film forming apparatus 1, a substrate stage 3 on which a substrate W is placed is provided in a vacuum chamber 2 as a processing chamber. The substrate stage 3 is a substrate that adheres the substrate W onto the substrate stage 3. A clamp 4 is provided as a close contact means, and a coolant circulating means 5 is provided for cooling the substrate stage 3 by circulating the coolant G through the substrate stage 3. The clamp 4 and the refrigerant circulation means 5 constitute a cooling means 6.

For example, a mixed gas of argon (Ar) gas and water vapor (H ₂ O) is introduced into the vacuum chamber 2 as a sputtering gas. The vacuum chamber 2 is provided with a target (not shown) serving as a sputtering member, a plasma generator (not shown), a transfer device (not shown) for transferring the substrate W, and the like.

  The substrate stage 3 is made of a metal such as stainless steel.

  The clamp 4 presses, for example, the four corners of the substrate W against the substrate stage 3.

  The refrigerant circulation means 5 is configured by connecting a tube 11, which is a refrigerant circulation path provided in the substrate stage 3, to a refrigerator 12 serving as a refrigerant circulation unit disposed outside the vacuum chamber 2.

  As the refrigerant G circulating in the tube 11, for example, helium (He) gas is used, and the substrate W that is in close contact with the substrate stage 3 by the clamp 4 is set below the room temperature of the vacuum chamber 2, for example, 0 ° C. It is possible.

  Although not shown, thin film transistors (TFT elements) that are switching elements of liquid crystal display elements are formed in advance on the substrate W, and an amorphous ITO film M is formed on these thin film transistors.

  Next, a method for forming an amorphous ITO film according to the first embodiment will be described.

  First, the substrate W is brought into close contact with the substrate 4 on the substrate stage 3 in the vacuum chamber 2.

  Next, the amorphous ITO film M is formed on the substrate W in the vacuum chamber 2 by mixing 2 to 3 sccm of water vapor into, for example, 100 sccm of argon gas as the sputtering gas and applying about 4 kW as the sputtering power.

  At this time, the temperature of the substrate W is set to 0 ° C. below the room temperature of the vacuum chamber 2 through the substrate stage 3 by circulating the refrigerant G from the refrigerator 12 in the tube 11.

After the amorphous ITO film M having a desired thickness is formed, the substrate W is unloaded from the vacuum chamber 2, and predetermined pixel patterning is performed on the amorphous ITO film M using a resist. For example, oxalic acid (C ₂ H The pixel gap of the amorphous ITO film M is etched using a weak acid such as ₂ O ₄ ).

  Thereafter, the resist is removed and annealed in a nitrogen atmosphere at, for example, 200 ° C. or higher to polycrystallize the entire amorphous ITO film M to obtain a low-resistance pixel ITO film.

  As described above, in the first embodiment, the substrate W is cooled to the room temperature or lower of the vacuum chamber 2 during the formation of the amorphous ITO film M.

  For this reason, when an amorphous ITO film is formed by a general sputtering method, the time during which the substrate is exposed to plasma becomes longer with the film thickness, that is, the film formation time, and the substrate temperature gradually rises. In contrast to the growth of microcrystals inside the film, in the first embodiment, the temperature rise of the substrate W can be suppressed, and the microcrystals inside the amorphous ITO film M accompanying the temperature rise of the substrate W can be suppressed. Generation can be suppressed, and is particularly useful when obtaining a thick amorphous ITO film M.

  That is, in manufacturing a liquid crystal display element, when etching the amorphous ITO film M, a weak acid is used so as not to affect elements such as a thin film transistor. However, the microcrystals remain without being etched with a weak acid. When the residue is generated as an aggregate and this residue is generated in the pixel gap, adjacent pixels are connected to each other and cause a continuous bright spot. The generation of continuous bright spots can be suppressed, and the yield of liquid crystal display elements can be improved.

  Specifically, a portable liquid crystal display element having a pixel gap of 5 μm is prepared, and the number (1,080) of the number is used as the denominator, and the result of dividing the number of liquid crystal display elements generated by the continuous shop is shown in FIG. In addition, the allowable generation limit of continuous bright spots is about 0.3%. This evaluation method is because it is not easy to examine the presence or absence of residue at each point of the substrate W, and therefore, it is more accurate as an evaluation to be evaluated as an actual image.

  As shown in FIG. 2, in the conventional example in which an amorphous ITO film is formed by a general sputtering method, the film thickness is substantially 0 when the film thickness is 1000 mm or less, and continuous bright spots are gradually generated when the film thickness exceeds this value. In this example, the film thickness limit is 1500% while the film thickness limit is 1500%, whereas in the present example, even when the film thickness is 1500mm, the occurrence rate is 0% and 2000mm. However, it can be seen that the improvement was 0.2%.

  In general, no matter how much the substrate W is cooled, the surface temperature of the substrate W is inevitably increased as the film formation time becomes longer. Therefore, it is necessary to control the temperature of the substrate W within a desired film thickness range. It is. In the liquid crystal display element, since there is no usage method in which the amorphous ITO film M exceeds 2000 mm, sufficient results can be obtained by maintaining the temperature of the substrate W at 0 ° C. as in the present embodiment.

  In addition, by cooling the substrate W by circulating the coolant G through the substrate stage 3 while being in close contact with the clamp 4 on the substrate stage 3, the substrate W can be cooled more reliably to the room temperature or lower of the vacuum chamber 2.

  In the first embodiment, in order to further improve the cooling efficiency, it is conceivable to improve the adhesion between the substrate stage 3 and the substrate W, as in the second embodiment shown in FIG. In addition, as a substrate contact means, an electrostatic chuck 15 that applies a high voltage of the substrate W to generate static electricity on the substrate W and adheres to the substrate stage 3 is used, and a groove portion is formed on the substrate stage 3 instead of the tube 11. 16 may be provided, and the substrate W may be gas-cooled by flowing a coolant G such as helium gas from the coolant circulation portion 17 into the groove portion 16. In this case, it was found that the occurrence rate of the continuous bright spots was 0% even at a film thickness of 2000 mm, which was further improved.

  Further, in each of the above embodiments, the substrate contact means and the refrigerant circulation means can be arbitrarily configured, and the cooling means 6 can also be arbitrarily configured.

  Further, the substrate W may be used for other than the liquid crystal display element.

It is explanatory drawing which shows the film-forming apparatus of the amorphous ITO film | membrane of the 1st Embodiment of this invention. It is a graph which shows the relationship between the film thickness of the amorphous ITO film | membrane in the film-forming method of the amorphous ITO film | membrane with the film formation apparatus of an amorphous ITO film | membrane, and the incidence rate of the continuous bright spot of the liquid crystal display element using a board | substrate. It is explanatory drawing which shows the film-forming apparatus of the amorphous ITO film | membrane of the 2nd Embodiment of this invention.

Explanation of symbols

2 Vacuum chamber as processing chamber 3 Substrate stage 4 Clamp as substrate contact means 5 Refrigerant circulation means 6 Cooling means
15 Electrostatic chuck as a substrate contact means
16 Groove
17 Refrigerant circulation part G Refrigerant M Amorphous ITO film W Substrate

Claims (6)

A method for forming an amorphous ITO film on a substrate by sputtering in a processing chamber,
A method for forming an amorphous ITO film, wherein the substrate on a substrate stage is cooled to a room temperature or less in the processing chamber during the formation of the amorphous ITO film. 2. The amorphous ITO film formation according to claim 1, wherein a coolant is circulated through the substrate stage while the substrate is in close contact with the substrate stage to cool the substrate to a room temperature or less in the processing chamber. Method. The amorphous body according to claim 2, wherein the substrate is cooled to room temperature or less by allowing the substrate to adhere to the substrate stage by an electrostatic chuck while flowing the coolant through a groove provided on the substrate stage. Deposition method of ITO film. An amorphous ITO film forming apparatus for forming an amorphous ITO film on a substrate by sputtering,
A processing chamber for forming an amorphous ITO film on the substrate by the sputtering method;
A substrate stage provided in the processing chamber and on which the substrate is placed;
A film forming apparatus for forming an amorphous ITO film, comprising: a cooling unit capable of cooling the substrate on the substrate stage to a room temperature or less in the processing chamber. Cooling means
Substrate contact means for bringing the substrate into close contact with the substrate stage;
A refrigerant circulating means capable of circulating a coolant through the substrate stage and capable of cooling the substrate that is in close contact with the substrate stage by the substrate close contact means to a room temperature or lower of the processing chamber. 4. The amorphous ITO film forming apparatus according to 4. The substrate contact means is an electrostatic chuck,
The refrigerant circulating means is
A groove provided on the substrate stage;
The amorphous ITO film forming apparatus according to claim 5, further comprising a refrigerant circulation unit that causes the refrigerant to flow in the groove.

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