JPH0673569A - Dry etching method for transparent electrode film - Google Patents

Abstract

PURPOSE:To enable the formation of fine patterns of transparent electrode films even if there are level differences on a ground surface by adopting a second stage in which the amts. of the org. gas for preventing adhesion and reducing gas to be supplied are increased in the method for evaporating In and Sn as org. matter. CONSTITUTION:An indium oxide film 1' contg Sn is deposited by sputtering evaporation at a prescribed thickness nearly over the entire surface of a quartz substrate 3 on which the electrodes 2 of a prescribed thickness are formed. A resist film 4 is then patterned and formed by photolithography on the film 1', and thereafter, the substrate 3 is inserted into a device, such as parallel flat plate type plasma etching device. H2 is then supplied as a reducing gas, CH4 as an org. gas for evaporation, and CH3OH as an org. gas for preventing the adhesion of a reactional product by cracking the reactional by-product generated by an evaporation reaction. These gases are supplied to the film 1' to etch the film 1' by as much as the thickness part corresponding to 80% of the film thickness. In succession, the flow rate of the CH3OH or H2 is increased and the remaining film 1' is etched at 100% overetching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for a transparent electrode film for patterning a transparent electrode film on a liquid crystal display device.

[0002]

2. Description of the Related Art The above-mentioned transparent electrode film is made of indium oxide (ITO) containing Sn and is difficult to dry-etch. For this reason, conventionally, pattern formation has been performed using the wet etching method. This wet etching method has a large line width shift in etching of 1 to 2 μm, which is within an allowable range in the conventional liquid crystal display device, but in recent years, it has become unacceptable as the liquid crystal display device becomes finer. Came.
Therefore, the line width shift in etching is ± 0.1 μm.
It has been required to use a dry etching method which can be controlled.

In the dry etching method for the transparent electrode film, similar to the wet etching method, a method of etching by halogenating with a gas such as hydrogen halide, and a method of vaporizing an organic substance by using an organic gas are vaporized. There is a method of etching by doing so. The former method uses a halogen gas that is highly corrosive and unstable, so that the safer latter method is becoming mainstream. The latter method will be described more specifically. In in a transparent electrode film made of indium oxide containing Sn was used.
And a vaporizing organic gas that vaporizes Sn into an organic compound and vaporizes, and a reducing gas that decomposes a reaction by-product generated by the vaporization reaction to promote the vaporization reaction are supplied to the transparent electrode film to react. .

[0004]

However, even in the case of the latter method described above, when the transparent electrode film is formed on the base having a step, the transparent electrode film on the step also has a step portion. Since it is formed, the portion along the stepped portion of the transparent electrode film is hardly etched due to the interference by the reaction by-product. For this reason, there is a problem that an etching residue is generated along the step portion of the transparent electrode film and a fine pattern cannot be formed.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to form a transparent electrode film with a fine pattern even if there is a step on the base, and further, the quality and thickness of the transparent electrode film vary. It is an object of the present invention to provide a dry etching method for a transparent electrode film that can control etching even if there is.

[0006]

A method for dry etching a transparent electrode film according to the present invention comprises: a vaporizing organic gas for vaporizing In and Sn into an organic compound in a transparent electrode film made of indium oxide containing Sn; A reducing gas that decomposes the reaction by-product generated by the reaction to promote the vaporization reaction, and an adhesion-preventing organic gas that prevents the reaction by-product from adhering to the transparent electrode film are applied to the transparent electrode film. The first step of supplying and reacting, and the supply amount of the adhesion preventing organic gas and / or the reducing gas are increased from the first step, and the vaporizing organic gas, the reducing gas and the adhesion preventing organic gas are transparent. Second reaction by supplying to electrode film
And the steps for achieving the above object. The first and second steps are performed while monitoring the cathode drop voltage of the etching apparatus in the etching apparatus, and the timing of transition from the first step to the second step is determined by the change in the cathode drop voltage. You can

[0007]

The present inventors have found that in the step portion of the transparent electrode film,
As a result of detailed examination of the situation where etching is hindered, the following findings were obtained.

The reaction by-product is produced by plasma polymerization with an organic gas. Also, on the surface of the transparent electrode film,
Since oxygen is supplied from the transparent electrode film, there is a phenomenon that this reaction by-product does not adhere. Therefore, by preventing the generation of reaction by-products and positively removing the etching residue, it is possible to prevent the etching from being disturbed in the step portion of the transparent electrode film. In order to prevent the formation of reaction by-products, it is effective to use organic substances containing oxygen such as alcohols. Further, in order to positively remove the etching residue, it is effective to switch the etching conditions before the etching of the transparent electrode film is completed.

In the present invention, in addition to the first step of supplying the vaporizing organic gas, the reducing gas, and the adhesion preventing organic gas to the transparent electrode film to react them, the adhesion preventing organic gas and / or the reducing gas. The supply amount of is increased from the first step,
The second step is adopted in which the vaporizing organic gas, the reducing gas and the adhesion preventing organic gas are supplied to the transparent electrode film and reacted. This prevents the formation of reaction by-products and positively prevents etching residues.

Furthermore, the inventors of the present invention, when performing etching of the transparent electrode film, the cathode drop voltage (V
When the waveform of (DC) was monitored, it was discovered that a variation point was found in the waveform of VDC during etching.
This mutation point appears in both the condition (the condition of the first step) that does not increase the adhesion preventing organic gas and / or the reducing gas and the condition (the condition of the second step) that the increased amount. Further, it was confirmed that the mutation point appeared in common under the above two conditions before the etching of the transparent electrode film on the flat portion was almost completed.

It is considered that the variation point of the VDC waveform is a universal phenomenon that appears due to the combination of the gas composition used for etching and the ITO film.

In the present invention, the change in the VDC waveform is used as the switching timing between the first step and the second step, so that the switching can be appropriately performed. Therefore, the transparent electrode film can be etched with high reliability, and it is possible to perform fine pattern formation of the transparent electrode film and reliable etching without generating etching residues.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 2 is a plan view showing an example of a transparent electrode film formed by using the present invention. In the transparent electrode film 1, an indium oxide film containing Sn is formed on almost the entire surface of the quartz substrate 3 on which the electrodes 2 ...
A pattern is formed by etching the indium oxide film using the dry etching method of the present invention. This transparent electrode film is patterned on a base having a step.

Next, the pattern formation of this transparent electrode film will be described.

First, as shown in FIG. 1A, the thickness is about 4
An indium oxide film 1 ′ containing Sn is vapor-deposited to a thickness of 1200 Å on the substantially entire surface of the quartz substrate 3 on which the electrode 2 having a thickness of 000 Å is formed, by a sputtering method.

Next, as shown in FIG. 1B, a resist film 4 is formed on the indium oxide film 1'by patterning by photolithography.

Then, the quartz substrate 3 is inserted into an etching device such as a parallel plate type plasma etching device, and the indium oxide film 1'is prepared under the conditions of STEP 1 in Table 1.
Of 960 angstroms corresponding to 80% of the film thickness are etched.

Specifically, H ₂ is used as a reducing gas for separating In and Sn contained in the indium oxide film 1 ′ from the bonded state with oxygen, and CH ₄ is used as a vaporizing organic gas for vaporizing it as an organic compound. As shown in FIG. 1 (c), CH ₃ OH is used as an organic gas for adhesion prevention that decomposes a reaction byproduct generated by the vaporization reaction, for example, a methane-based polymer, and prevents the adhesion of the reaction byproduct. To
It was supplied to the indium oxide film 1 ′. The flow rate of CH ₄ is 45 SCCM, the flow rate of H ₂ is 75 SCCM, the flow rate of CH ₃ OH is 5 SCCM, and the pressure inside the etching apparatus is 2
0 mTorr and high frequency power (RF power) were 200 W (first step).

Then, at an appropriate time before the end of etching, as shown in STEP 2 of Table 1, the flow rate of CH ₃ OH, which is an organic gas for adhesion prevention, is changed from 5 SCCM to 10 S.
The remaining indium oxide film 1 ′ (240 Å) is etched with 100% overetching while increasing the CCM and the other conditions to be the same as STEP 1 (second step).

[0021]

[Table 1]

Further, the resist 4 is chemically removed,
The transparent electrode film 1 is obtained.

With respect to the transparent electrode film 1 obtained as described above, it was checked whether or not the residue of the indium oxide film 1 ′ remained at the bottom of the step portion. As shown in FIG. 2, the check was performed by applying a voltage of 0 to 20 V to the transparent electrode film with a current measuring device 5 and judging the current value at that time.
As a result, when the etching is performed to the end only under the conditions of STEP 1 and the additional etching corresponding to the film thickness of 50% is performed, the current value at the time of applying 20 V is 200 to 300 p.
Although it was A, after the condition of STEP 1, STEP
When etching was performed under the condition of 2, the current value when 20 V was applied could be 20 pA. This value (20
pA) is a value that is considered to be the completion of etching, and it can be seen that the indium oxide film 1 ′ at the location to be removed was completely removed by etching.

(Embodiment 2) In Embodiment 2, unlike Embodiment 1, etching is performed by increasing the flow rate of the reducing gas at an appropriate time before the end of etching. Specific steps will be described below.

First, as in the first embodiment, the thickness is about 4000.
An indium oxide film 1'containing Sn is vapor-deposited to a thickness of 1200 angstrom on substantially the entire surface of the quartz substrate 3 on which the angstrom electrode 2 is formed, and a resist film 4 is patterned on the indium oxide film 1 '.

Thereafter, the quartz substrate 3 is inserted into an etching apparatus such as a parallel plate type plasma etching apparatus, and the indium oxide film 1'is prepared under the conditions of STEP 1 in Table 2.
Of 960 angstroms corresponding to 80% of the film thickness are etched. Specifically, H ₂ is used as a reducing gas that separates In and Sn contained in the indium oxide film 1 ′ from the bonded state with oxygen, and CH ₄ is used as a vaporizing organic gas that is vaporized into an organic compound. As shown in FIG. 1 (c), CH ₃ OH is used as an adhesion preventing organic gas that decomposes a reaction by-product generated by the reaction, for example, a methane-based polymer, and prevents the reaction by-product from adhering. It was supplied to the indium film 1 ′. In addition, CH
The flow rate of ₄ is 45 SCCM, the flow rate of H ₂ is 75 SCCM, C
The flow rate of H ₃ OH was 5 SCCM, the pressure inside the etching apparatus was 20 mTorr, and the high frequency power (RF power) was 200 W (first step).

Then, at an appropriate time before the etching is finished, as shown in STEP 2 of Table 2, the flow rate of H ₂ as a reducing gas is increased from 75 SCCM to 100 SCCM to leave the remaining indium oxide film 1 '. Etch (240 Å) with 100% overetch. At this time, the flow rate of CH _{4 as} the vaporizing organic gas is changed from 45 SCCM to 20 SCCM so that the total supply amount of the vaporizing organic gas and the reducing gas is the same as STEP 1.
Is reduced to (second step).

[0028]

[Table 2]

Further, the resist 4 is chemically removed,
The transparent electrode film 1 is obtained.

In the transparent electrode film 1 obtained as described above, it was checked in the same manner as in Example 1 whether or not the residue of the indium oxide film 1'was left at the bottom of the step portion.
As a result, when the etching is performed to the end only under the conditions of STEP 1 and the additional etching corresponding to the film thickness of 50% is performed, the current value at the time of applying 20 V is 200 to 300 p.
Although it was A, after the condition of STEP 1, STEP
When etching was performed under the condition of 2, the current value when 20 V was applied could be 30 pA. This value (30
pA) is also a value that is considered to be the completion of etching, and it can be seen that the indium oxide film 1 ′ at the portion to be removed was completely removed by etching. (Third Embodiment) In the first and second embodiments, the second step is performed by increasing the supply amount of the adhesion preventing gas and / or the reducing gas from an appropriate time before the etching is completed. The first step has a higher etch rate (250 Å / min) than the second step, and the line width shift due to side etching is small. Therefore, in order to improve the pattern accuracy of the transparent electrode film, the first
It is necessary to increase the amount of etching by the process of (1) as much as possible. However, when all the transparent electrode film on the flat portion is removed by etching, the reaction by-products start to adhere to the stepped portion of the transparent electrode film, and the process is switched to the second step to remove the adhesion preventing gas and / or the reducing gas. Even if the supply amount is increased, the reaction by-product is prevented from adhering and the step portion of the transparent electrode film is not etched. Therefore, it is necessary to switch from the first step to the second step before the transparent electrode film on the flat portion is completely removed by etching, and the switching timing is important. In order to set this switching timing, the time taken to remove the transparent electrode film on the flat portion by etching may be calculated from the film thickness and the etching rate of the transparent electrode film, but there are variations in the film quality and film thickness of the transparent electrode film. On the other hand, it may be difficult to improve the controllability of etching. For example, if the first step is too short, the pattern accuracy cannot be improved as described above. Also,
When the flat portion of the transparent conductive film is completely removed by etching in the first step, the reaction by-product adheres to leave a residue on the step portion as described above, resulting in a short circuit between patterns. Occurs. Therefore, in this embodiment, when the transparent electrode film is etched, the VD of the etching device is
The waveform of C was monitored to determine the timing of switching from the first step to the second step.

First, it was confirmed at what point in time the VDC waveform variation point appeared, as follows.

First, an indium oxide film containing Sn is formed on the quartz substrate 3 by sputtering to a thickness of 120.
It is vapor-deposited to 0 angstrom, and a resist film 4 is patterned thereon by photolithography. Here, a repeating pattern having a size of 25 μm × 25 μm was formed with a space between the patterns of 3 μm.

This quartz substrate 3 was placed in an etching device such as a parallel plate type plasma etching device, and the indium oxide film was etched under the conditions of STEP 1 in Table 2 above. At this time, VDC obtained from the etching device
Was monitored to obtain a waveform having a mutation point as shown in FIGS. 3 (a) and 3 (c).

Similarly, the quartz substrate 3 in which the resist film 4 is patterned and formed on the indium oxide film is inserted into an etching apparatus, and the indium oxide film 1'is etched under the conditions of STEP 2 in Table 2 above. Figure 3
Waveforms having mutation points were obtained as shown in (b) and (d).

The above two conditions (STEP 1 and STE)
According to P2), etching was performed while monitoring the change of VDC, and the etching process was stopped at the time when a variation point of the waveform of VDC appeared, and in the case of the condition of STEP 1, the etching amount was 760 Å, Depending on the conditions, the etching amount was 720 Å.

From the above results, it is understood that the etching removal of the transparent conductive film is not completely completed at the time when the VDC mutation point is obtained. Therefore, it can be seen that even if the first step is switched to the second step after the mutation point appears, it is sufficient to prevent the reaction by-product from adhering to the step portion.

By the way, it is desirable to increase the etching amount in the first step as much as possible in order to improve the pattern accuracy. Therefore, the conditions under which the etching amount in the first step is increased as much as possible and no residue is generated in the step portion of the transparent electrode film were confirmed as follows.

First, as in the first embodiment, the thickness is about 4000.
An indium oxide film 1'containing Sn is vapor-deposited to a thickness of 1200 angstrom on substantially the entire surface of the quartz substrate 3 on which the angstrom electrode 2 is formed, and a resist film 4 is patterned on the indium oxide film 1 '. Here, a repeating pattern having a size of 25 μm × 25 μm was formed with a space between the patterns of 3 μm.

This quartz substrate 3 was placed in an etching apparatus such as a parallel plate type plasma etching apparatus, and the indium oxide film 1'was etched under the conditions of STEP 1 in Table 2 above. Here, the thickness of the indium oxide film is 6
Etching was carried out by measuring the time so as to remove a portion corresponding to 0 to 80% by etching (first step). Also,
At this time, when a change in VDC was simultaneously monitored, a waveform as shown in FIG. 1 (e) was obtained.

Then, under the conditions of STEP 2 in Table 2 above,
The remaining indium oxide film 1 ′ was removed by etching with 50% overetching (second step).

A voltage was applied to the two transparent conductive films patterned as described above to check the presence or absence of a short circuit between wirings. The result is shown in FIG. In addition, as a comparative example, overetching was performed using only the conditions of STEP1.
The ones etched at 0% are shown at the same time. As can be understood from this figure, in the first step, 60 to 80% of the film thickness of the indium oxide film was removed by etching, and there was no short circuit between patterns and no etching residue at the step portion. Etching can be performed. For example, the one with 60% removed has a current value of 1 when 20 V is applied.
0 to 30 pA, 70% removed has a current value of 30 to 80 pA when 20 V is applied, and 80% removed has a current value of 20 to 80 pA that is 30 to 80 pA. It is below 100 pA. On the other hand, in the case where only the first step is performed, the flat portion is completely removed and the reaction by-product adheres to the step portion. Therefore, it is considered that the etching of the step portion is hindered, a residue is generated, and the leak current between the wirings becomes large. For example, the current value when 20 V was applied was 230 pA to 1 nA.

From the above, by removing about 60 to 80% of the film thickness of the indium oxide film in the first step and removing the rest in the second step, no residue is generated in the step portion. I understand.

In the first step, when a portion corresponding to 60 to 80% of the film thickness of the indium oxide film was removed by etching, the change in VDC was simultaneously monitored, and a waveform as shown in FIG. 1 (e) was obtained. Obtained. In this figure, the mutation point is 7
A portion corresponding to 0% appears in the vicinity of being removed by etching.
Since this point is within the range in which no residue is present in the stepped portion as described above, this mutation point is changed from the first step to the second step.
It can be seen that it can be used to determine the timing of switching to the process.

In the pattern formation of the transparent conductive film shown in FIG. 2, VDC was monitored, and when the variation point appeared, the condition of STEP 1 was switched to the condition of STEP 2 and etching was performed. No good wiring was obtained. In Examples 1 to 3 above, the supply amount of the adhesion preventing organic gas or the reducing gas is increased to perform the second step, but the supply amounts of both the adhesion preventing organic gas and the reducing gas are increased. You may.

[0045]

As is apparent from the above description, according to the present invention, it is possible to prevent the etching inhibition on the transparent electrode film portion along the step portion of the transparent electrode film, and to prevent the residue along the step portion of the transparent electrode film. Will never remain. Therefore, the transparent electrode film can be formed with a fine pattern, and a high-density and high-definition liquid crystal display device can be realized. In addition, the present invention combines the conventional high-speed etching and the etching for removing residues, has a processing capability with a good productivity level, and has high reliability. The timing of switching between the first step and the second step can be determined by monitoring the change in the cathode drop voltage of the etching apparatus, and the etching can be performed against variations in the film quality and film thickness of the transparent electrode film. Controllability can be improved, and reliable etching and fine pattern formation can be performed.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a dry etching method of the present invention.

FIG. 2 is a plan view showing an example of a transparent electrode film obtained by the present invention.

3 (a) to 3 (e) are diagrams showing changes in VDC in Example 3. FIG.

FIG. 4 is a diagram showing a current between wiring patterns according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent electrode film 1'Sn containing indium oxide film 2 Electrode 3 Quartz substrate 4 Resist

Claims (2)

[Claims] 1. An organic gas for vaporization for vaporizing In and Sn as an organic compound in a transparent electrode film made of indium oxide containing Sn, and a reaction by-product generated by the vaporization reaction are decomposed to accelerate the vaporization reaction. A reducing gas, and a first step of reacting the transparent electrode film with an adhesion-preventing organic gas for preventing the reaction by-product from adhering to the transparent electrode film; and A second step of increasing the supply amount of the gas and / or the reducing gas from the first step, and supplying the vaporizing organic gas, the reducing gas and the adhesion preventing organic gas to the transparent electrode film to cause a reaction; A method of dry etching a transparent electrode film including. 2. The first and second steps are carried out in an etching apparatus while monitoring a cathode drop voltage of the etching apparatus, and a change in the cathode drop voltage causes a transition from the first step to the second step. Claim 1 which determines timing
5. The method for dry etching a transparent electrode film according to [4].