JP3491470B2 - Dry etching method and method for manufacturing liquid crystal display device - Google Patents

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 and, more particularly, to an etching gas effective for patterning a metal chromium thin film with high accuracy.

[0002]

2. Description of the Related Art Wet etching is generally used as a method for etching a metal chromium thin film. This is because the etching rate is high, the area can be easily increased, the management is relatively simple, and the mass productivity is high.

On the other hand, the metal chromium thin film has a different film quality depending on the film forming method and film forming conditions, and the etching rate and the patterning characteristics differ depending on the film quality difference. For example, when forming a metal chromium thin film by a method of performing sputtering in an inert gas atmosphere such as argon with a target of metal chromium, the lower the pressure of the argon gas, the larger the crystal grains of metal chromium in the thin film grow, The specific resistance of the thin film is low. However, since the crystal grains become large, the etching rate decreases, the patterning shape becomes rough, and the patterning accuracy also decreases.

As described above, the specific resistance of the metal chromium thin film and the patterning property are in a contradictory relationship, and if the importance is placed on reducing the specific resistance, patterning accuracy cannot be obtained.

Further, in the above metal chromium thin film,
Even if the sputtering conditions are the same, the film quality of the metallic chromium thin film is very unstable because the composition of the target surface may change over time.

[0006]

In the film formation of the metal chromium thin film described above, the etching rate is difficult to control because it is often carried out under the film forming conditions that place importance on the specific resistance. In wet etching, which is usually performed at times, the etching amount is adjusted by controlling the etching time.Therefore, etching residue may occur due to insufficient etching, or side etching may occur due to excessive etching, resulting in pattern thinning. There is a problem that occurs frequently.

As a solution to this problem, photolithography,
There is a method of repeating the wet etching process twice. However, this method has a problem that the number of steps is doubled, which impairs mass productivity.

Further, when a step is formed on the underlayer of the metal chromium thin film, the etching liquid permeates along the step during the patterning of the metal chromium, and the metal etches between the metal chromium thin film and the underlayer. There is a problem that the pattern of the chromium thin film is eroded or, in an extreme case, the pattern is broken.

In order to solve each of these problems, a dry etching method was examined. For dry etching of the metal chromium thin film, a mixed gas of chlorine gas and oxygen gas is usually used. As an etching method, there are reactive ion etching (hereinafter, simply referred to as “RIE”) and plasma etching (hereinafter, simply referred to as “PE”). Since the reaction rate of RIE mode etching for a metal chromium thin film is extremely slow at 300 Å / min or less, it is realistic to perform it in PE mode.

In this dry etching, the metallic chromium is first converted to chromium oxide, and since this chromium oxide is reacted with chlorine to be vaporized, it is necessary to always use oxygen gas. Has the effect of ashing the resist used as a mask,
There is a problem that the resist pattern is thinned by the oxygen gas, which makes it difficult to obtain patterning accuracy and causes patterning variations.

Therefore, the present invention is to solve the above-mentioned problems, and the problem is that in a method of patterning a metal chromium thin film by dry etching, rapid processing can be performed without sacrificing patterning accuracy. Moreover, it is to obtain a practical method with little variation in patterning.

[0012]

Means for Solving the Problems The means taken by the present invention to solve the above-mentioned problems are to dry the metal chrome according to a predetermined pattern of the mask by dry etching with a mask formed on the surface of the metal chrome. In a dry etching method of etching by using an etching gas composed of at least a ternary system of chlorine gas, oxygen gas and CH ₄ , when the flow rate ratio of the chlorine gas to the etching gas is 7: 4, The dry etching method is characterized in that the flow rate ratio of CH ₄ is set to a range of less than 7: 0.75.

Furthermore, in a dry etching method of etching the metal chromium according to a predetermined pattern of the mask by dry etching with a mask formed on the surface of the metal chromium, at least chlorine gas, oxygen gas and CH ₃ OH are used. When an etching gas of a three-component system is used and the flow rate ratio of the chlorine gas to the etching gas is 7: 4, the flow rate ratio of the CH ₃ OH to the etching gas is set to a range less than 7: 0.75. It is characterized by

According to these means, in addition to chlorine gas and oxygen gas, an organic gas of CH ₄ or CH ₃ OH is mixed for etching, thereby improving the etching rate without impairing the patterning property. be able to.

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

In addition, the liquid crystal display device of the present invention has a metal chromium layer on at least one substrate, and dry-etches the metal chromium into a predetermined pattern on the mask in a state where a mask is formed on the surface of the metal chromium. According to the method of manufacturing a liquid crystal display device, the metal chromium is dry-etched by the dry etching method.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic structure of a dry etching apparatus used in the dry etching method according to the present invention. This dry etching apparatus is a parallel plate type apparatus and is capable of uniformly processing the surface of a substrate having a relatively large area.

In this apparatus, the upper electrode 11 and the lower electrode 12 are arranged in parallel inside the vacuum container 10 so as to face each other at a predetermined interval. Both the upper electrode 11 and the lower electrode 12 have flat plate surfaces, and the lower lower electrode 12
The substrate 20 is set on the plate surface of.

The upper electrode 11 is connected to a high-frequency power source 13 arranged outside the vacuum container 10, and 13.56 M
A high frequency electric potential (AC electric potential) of Hz is applied. A ground potential is supplied to the vacuum container 10 and the lower electrode 12 via the wiring 14.

A gas introduction pipe 15 connected to a gas supply system (not shown) is connected to the upper electrode 11. The gas supply system is configured to draw out gases at predetermined flow rates from gas cylinders containing a plurality of types of gases, mix the gases, and supply the gases, for example, by appropriately adjusting the flow rates of the gases via a mass flow controller. It is configured so that it can be supplied. The gas introduced into the upper electrode 11 is supplied into the vacuum container 10 from the shower head-shaped bottom surface portion 11 a having a large number of openings in the upper electrode 11. By forming the upper electrode 11 in this way, the uniformity of etching can be improved.

An exhaust pipe 16 connected to a gas exhaust system (not shown) (for example, a vacuum pump) is connected to the vacuum container 10. A known pressure control system is provided so that the pressure in the vacuum container 10 during processing can be controlled to be substantially constant by the exhaust from the exhaust pipe 16.

This embodiment is a method used in the step of patterning a metallic chromium thin film formed on the substrate 20. As a case of forming a metal chromium thin film on the substrate 20, as shown in FIG. 2, when one electrode layer is formed of Cr for forming an MIM element on the element side substrate of an active matrix type liquid crystal panel, There is.

In this case, the substrate 20 is made of transparent non-alkali glass, and Ta is deposited on the surface of the substrate 20 by sputtering by several hundred Å, and a base layer (not shown) made of Ta oxide is formed by thermal oxidation. .) Is formed.
This underlayer is for improving the adhesion between the substrate 20 and the upper layer described below.

Next, Ta is deposited again by sputtering to a thickness of about 2 to 3,000 liters, and patterned by a normal photolithography method to form the wiring layer 21. The wiring layer 21 is integrally provided with a first electrode portion 21a protruding for each pixel region on the substrate 20 which is the element side substrate. Further, the wiring layer 21 and the first electrode portion 21a
A thin insulating film (not shown) having a thickness of about 500Å is formed on the surface of the substrate by anodization.

Next, a chromium metal thin film having a thickness of about 800 Å is deposited on the insulating film by a sputtering method so as to partially cover the first electrode portion 21. The dry etching apparatus shown in FIG. 1 is used to pattern the metal chromium thin film. The metal chrome thin film is formed by patterning the electrode portion 22a that overlaps the first electrode portion 21a so as to intersect with the first electrode portion 21a and the electrode portion 22a.
2 with a pixel contact portion 22b extending from and extending from a.
Second electrode layer 22 formed in a plane pattern as shown in FIG.
Becomes

Finally, the pixel contact portion 22 of the second electrode layer 22.
The transparent electrode 23, which is a pixel electrode, is formed of ITO (indium tin oxide) so as to overlap with b.

In order to pattern the second electrode layer 22 by etching the metal chromium thin film shown in FIG. 2, a resist is applied on the surface of the substrate 20 and exposed, and the portion where the second electrode layer 22 is formed is resist-coated. Etching is performed using this resist as a mask.

In this case, the portion where the first electrode portion 21a and the second electrode layer 22 are laminated via the insulating film is the joint surface S (hatched portion) shown in FIG. 2, and the area of this joint surface S is the MIM element. It becomes the joint area of. Therefore, the area of the joint surface S is M
This is an important factor that determines the characteristics of the IM device. For example, the area of the junction surface S determines the junction capacitance of the MIM element, and as a result, the ratio between the liquid crystal capacitance and the MIM capacitance is determined, the ON resistance of the MIM element is determined, and the writing characteristic to the pixel electrode is determined. .

The area of the bonding surface S of the MIM element is the first
It is determined by the pattern shape of the electrode portion 21a and the pattern shape of the second electrode layer 22. Therefore, the patterning accuracy of the second electrode layer 22 and the variation in the pattern are MI.
It directly affects the accuracy and variation of the characteristics of the M element.

Next, the etching process in the patterning process of the second electrode layer 22 will be described. This etching process is performed using the dry etching apparatus shown in FIG. In this case, the etching gas introduced into the vacuum chamber 10 is usually a mixed gas of chlorine gas and oxygen gas for etching metallic chromium. Oxygen ions and chlorine ions activated by the introduction of this mixed gas are generated, the reaction represented by the following formula occurs with respect to the metal chromium thin film, and the etching action proceeds.

Cr + XO ^2- → CrO _X ... CrO _X + (2-X) O ^2- + 2Cl ⁻ → CrO ₂ Cl ₂ ↑ ... That is, metallic chromium is activated oxygen ions as shown in the formula. It reacts to form chromium oxide, and this chromium oxide is vaporized by reacting with activated oxygen ions and chlorine ions as shown in the formula.

Here, as shown in the above equations and, oxygen is indispensable for the etching reaction, but there is a problem that this oxygen ashes the ordinary resist layer and thins the resist during etching. . The ashing action on the resist lowers the patterning accuracy of the metal chrome thin film, and causes variations in the pattern of the second electrode layer for each pixel in the liquid crystal panel and eventually variations in the characteristics of the MIM element, which causes display unevenness. There is a point.

In the present embodiment, in order to solve the above problems, etching is performed by further adding an organic gas to the mixed gas. Table 1 below shows the etching conditions when dry etching is performed by adding various organic gases to a mixed gas of chlorine gas and oxygen gas. here,
The mode is PE mode.

[0042]

[Table 1]

In Table 1 above, the power is 1800 W,
The gap between the electrodes is 100 mm, the temperature of the upper electrode 11 is 20 ° C. except for the sample number 20, and the sample number 20 is 55 ° C. The temperature of the lower electrode 12 is 20 for all sample numbers.
℃. In addition, the total flow rate of all gases is approximately 1200 to 16
It is 00 cc / min.

Table 2 below shows the in-plane uniformity of the etching rate, the amount of side etching, and the amount of etching for the samples in Table 1 above.

[0045]

[Table 2]

As described above, it is understood that the etching rate may be improved by adding an organic gas to chlorine gas and oxygen gas. Especially in methanol (CH ₃ OH) and methane (CH ₄ ), sample numbers 7 and 2 can be adjusted by adjusting the flow rate of the organic gas.
As shown in 0, the etching rate can be increased by about 15 to 33% while maintaining the uniformity of the side etching amount and the etching amount.

Of the above, CO and CHF ₃ are effective in reducing the amount of side etching. H ₂ 0 has some effect in reducing the amount of side etching, but it is not preferable because it lowers the etching rate.

Generally, when etching is performed only with chlorine gas and oxygen gas, the etching rate can be increased by increasing the oxygen gas. However, when the oxygen gas amount is increased, the resist covering the metal chromium thin film is ashed to form a pattern. And the patterning property is impaired. Therefore, there is a problem that there is a trade-off between the improvement of the etching rate and the patterning property because it is necessary to suppress the oxygen gas amount to some extent.

On the other hand, in this embodiment, by using the etching gas in which the organic gas is mixed in addition to the chlorine gas and the oxygen gas, the etching rate can be increased without increasing the oxygen gas. There is. As the type of organic gas, a molecular gas containing hydrocarbon can improve the etching rate without deteriorating the patterning property. For example, paraffin hydrocarbons (CH ₄ , C ₂ H ₆ , C ₃ H ₈ , ...)
Alcohol _{(CH 3 OH, C 2 H} 5 OH, C 3 H 7 O
H, ...) Of these, especially the methyl group (CH
Organic gas with ₃ ) is effective.

Since the above organic gas selectively produces organic deposition on the surface of the resist, ashing of the resist is suppressed and deterioration of the patterning property is limited. If the ashing of the resist is appropriately performed, the metal chromium thin film is patterned so that its side wall has a forward tapered shape, so that the coverage of the upper pixel electrode and the like can be enhanced and the pattern break can be prevented. In particular, since an organic gas containing hydrocarbon forms a hydrocarbon thin film on the surface of the resist, the ashing action of the resist can be prevented, the patterning accuracy can be improved, and the patterning variation can be reduced.

With respect to the effect of adding the above organic gas, when the other etching conditions are kept substantially constant, the etching rate is low when the addition amount is small, and there is a peak of the etching rate when the addition amount is increased. On the contrary, as the amount is increased, the etching rate decreases. The addition amount of the organic gas corresponding to the peak area of the etching rate varies depending on other etching conditions such as the type of organic gas, the flow rates of chlorine gas and oxygen gas, and the gas pressure.

In Table 1 above, the gas pressure and the chlorine gas flow rate are kept substantially constant, and the flow rate ratio between the oxygen gas and the organic gas is changed under the condition that the total flow rate of the oxygen gas and the organic gas is also kept substantially constant. Etching.

As a result, for example, sample Nos. 4 to 4 in Table 1 above
When the flow rate of the organic gas is increased under the condition of No. 6, as shown in FIG.
As shown in, there is a peak of the etching rate with respect to the flow rate of the organic gas. Similarly, sample number 7 in Table 1 above
When the flow rate of the organic gas is increased under the condition of 10
As shown in FIG. 4, there is also an etching rate peak.

As described above, as shown in FIG. 3 and FIG.
In this embodiment, the etching rate can be improved by adjusting the flow rate of the organic gas without deteriorating the patterning property.

[0055]

As described above, the present invention has the following effects.

According to the first aspect, the etching rate can be improved without impairing the patterning property by performing the etching by mixing the organic gas in addition to the chlorine gas and the oxygen gas.

According to the second aspect, since the hydrocarbon film is formed on the mask of metallic chromium by mixing the organic gas containing hydrocarbon, it is possible to prevent the mask from being eroded. Patterning accuracy can be improved.

According to the third aspect, by using the organic gas having a methyl group, it is possible to achieve both improvement of etching rate and securing of patterning property.

According to the seventh aspect, especially the side etching amount is reduced and the patterning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram showing an apparatus configuration for carrying out a dry etching method according to the present invention.

FIG. 2 is a graph showing a planar structure on an element substrate of a liquid crystal panel that performs a dry etching method according to the present invention.

FIG. 3 is a graph showing a relationship between a flow rate ratio of an organic gas (methyl alcohol) and an etching rate in the dry etching method according to the present invention.

FIG. 4 is a graph showing a relationship between a flow rate ratio of an organic gas (methane) and an etching rate in the dry etching method according to the present invention.

[Explanation of symbols]

10 vacuum container 11 Upper electrode 12 Lower electrode 13 High frequency power supply

Continuation of the front page (56) References JP-A-6-230557 (JP, A) JP-A-4-247619 (JP, A) JP-A-6-181189 (JP, A) JP-A-3-33848 (JP , A) JP 58-19476 (JP, A) JP 51-50244 (JP, A) JP 61-256728 (JP, A) JP 50-119575 (JP, A) JP 55-89474 (JP, A) JP-A-50-80082 (JP, A) JP-A-53-136966 (JP, A) JP-A-61-270827 (JP, A) JP-A-51-90274 (JP, A) A) JP-A-60-148123 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23F 4/00 G02F 1/13 H01L 21/3065

Claims (3)

(57) [Claims] 1. A dry etching method in which a mask is formed on the surface of metal chromium, and the metal chromium is etched according to a predetermined pattern of the mask by dry etching, wherein at least 3 of chlorine gas, oxygen gas and CH ₄ are used. An etching gas composed of a component system is used, and the flow rate ratio of the chlorine gas to the etching gas is 7
When pair 4 is used, the CH for the etching gas is used.
_4. A dry etching method, characterized in that the flow rate ratio of ₄ is within a range of less than 7: 0.75. 2. A dry etching method of etching metal chromium in accordance with a predetermined pattern of the mask by dry etching with a mask formed on the surface of metal chromium, wherein at least chlorine gas, oxygen gas and CH ₃ OH are used. An etching gas composed of a three-component system is used, and the flow rate ratio of the chlorine gas to the etching gas is 7
When pair 4 is used, the CH for the etching gas is used.
A dry etching method characterized in that a flow rate ratio of ₃ OH is set to a range less than 7: 0.75. 3. A liquid crystal display device having a metal chrome layer on at least one substrate, wherein the metal chrome is etched according to a predetermined pattern of the mask by dry etching with a mask formed on the surface of the metal chrome. 3. The method for manufacturing a liquid crystal display device according to claim 1, wherein the metallic chromium is dry-etched by the dry etching method according to claim 1.