JP2001077098A - Etchant and manufacture of thin film pattern by use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal thin film pattern with a gently tapered edge without forming a metal thin film into a multilayered structure, by a method wherein a phosphoric acid aqueous solution, an acetic acid aqueous solution, and a nitric acid aqueous solution all prescribed in concentration are mixed together so as to meet a specific formula in volume. SOLUTION: A volume A of 85% phosphoric acid aqueous solution, a volume B of 90% acetic acid aqueous solution, and a volume C of 70% nitric acid aqeous solution are mixed together so as to meet these formulas, 0.2<=A÷(B+C)<=0.6, 0.04<=C÷(A+B+C)<=0.2, to obtain an etching liquid. When an etching liquid of the above composition is used, a photoresist is shrunk when patterning is carried out, so that an etching liquid penetrates through an interface between a photoresist and a metal thin film 102 covered with the photoresist at a part along the outline of the resist pattern 104. Therefore, the edge of a thin film pattern obtained by patterning gets tapered in cross section as its upper side is preferentially etched.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an etchant used for patterning a thin film by wet etching, and a method for manufacturing a thin film pattern using the same. In particular, the present invention relates to an etchant for obtaining an array substrate used for a liquid crystal display device and other flat display devices and a method for producing a thin film pattern, and more particularly to a method for forming a thin film transistor on an array substrate.

[0002]

2. Description of the Related Art In various fields, a thin film pattern is formed by patterning a thin film formed on a substrate using a resist pattern such as a resin.

In the following, a description will be given by taking, as an example, a thin film pattern for forming a thin film transistor on an array substrate of an active matrix display device.

A light transmission type active matrix type liquid crystal display device is most commonly used as an active matrix type display device. An array substrate constituting such an active matrix display device has a plurality of signal lines (data lines) and scanning lines (gate lines) arranged in a grid on a transparent insulating substrate such as a glass plate. A thin film transistor (TFT) as a switching element for each pixel is arranged near each intersection.

The TFT on the array substrate is made of amorphous silicon.
Generally, a semiconductor film such as (a-Si: H) is used as an active layer.In recent years, however, as an active layer, polycrystalline silicon (poly) which can secure higher electron mobility than amorphous silicon is used. -Si) has been attempted. As a laminated structure of a TFT, an inverted staggered TFT in which a gate insulating film is provided over a scanning line serving as a gate electrode, and a semiconductor film and source / drain electrodes are provided thereon is often used.

In an inverted stagger type TFT, when forming a thin film pattern of a scanning line, an end surface forming an edge (contour) of the thin film pattern is formed to have a sufficiently gentle slope with respect to the substrate surface. There is a need. That is, it is necessary that the edge of the thin film pattern has a sufficiently small taper angle (the angle between the end face and the substrate surface) in a cross section perpendicular to the substrate surface. This is because if the edge of the thin film pattern is not tapered, the coverage with the gate insulating film is insufficient at the edge, and insulation failure is likely to occur.

The method of patterning a metal thin film is roughly classified into a method of performing wet etching and a method of performing dry etching. In the case of performing patterning by wet etching, the method of performing etching is less than the method of performing dry etching. The apparatus is simple, the processing capacity per unit time can be increased, and uniform etching over a large area can be expected.
For this reason, wet etching is frequently used for manufacturing a thin film pattern on an array substrate for a flat display device.

As a method of manufacturing a thin film pattern having a tapered edge, Japanese Patent Application Laid-Open Nos. 4-372934 and 9-064366 disclose a method of patterning a metal thin film by wet etching. Is disclosed as a multilayer metal thin film composed of a plurality of metal layers having different etching rates.

More specifically, aluminum (Al) is formed on a substrate.
After depositing a film and a molybdenum (Mo) film in this order, etching is performed with a mixed acid consisting of phosphoric acid, acetic acid, nitric acid and water. The etching rate of the upper Mo layer is
Since the etching rate is higher than the etching rate of the lower Al layer, during etching, as the upper layer is drawn inward from the contour of the resist pattern, the tapered end surface is sufficiently gentle with respect to the substrate surface. An edge is formed.

[0010]

However, according to the manufacturing method of the prior art described above, in order to make the edge of the thin film pattern made of metal sufficiently gently tapered, a multilayer metal film made of two kinds of metals is required. It is necessary to
For this reason, when a metal film is formed by sputtering or the like, two types of metal targets are required, so that the material cost increases, and a plurality of film forming apparatuses are required, which causes an increase in cost and a decrease in productivity. .

The present invention has been made in view of the above problems, and a method of manufacturing a thin film pattern forming an array substrate or the like used for a liquid crystal display device or other flat display device, and an etching solution for forming a thin metal film with a multilayer structure. It is an object of the present invention to provide an etching solution and a manufacturing method which can make the edge of the obtained thin film pattern tapered sufficiently.

[0012]

According to the first aspect of the present invention, there is provided an etching solution comprising 85% of the capacity A in an etching solution comprising phosphoric acid, acetic acid, nitric acid and water used for producing a thin film pattern on a substrate. Phosphoric acid aqueous solution, 90% of capacity B
If an acetic acid aqueous solution and a 70% nitric acid aqueous solution having a capacity C are mixed, the following formulas (1) and (2) are satisfied.

0.2 ≦ A ÷ (B + C) ≦ 0.6 (1) 0.04 ≦ C ÷ (A + B + C) ≦ 0.2 (2) According to the present invention, even if the metal thin film is not a multilayer film, The edge of the obtained thin film pattern can be made sufficiently smooth and tapered. Therefore, as compared with the case where the metal thin film is a multilayer film, material and apparatus costs can be reduced and productivity can be improved.

According to a second aspect of the present invention, there is provided a method of manufacturing a thin film pattern from a thin film deposited on a substrate using an etching solution comprising phosphoric acid, acetic acid, nitric acid and water. The liquid is 8 volume A
5% phosphoric acid aqueous solution, 90% acetic acid aqueous solution of volume B, and
If a 70% nitric acid aqueous solution having a capacity C is mixed, the following formulas (1) and (2) are satisfied.

0.2 ≦ A ÷ (B + C) ≦ 0.6 (1) 0.04 ≦ C ÷ (A + B + C) ≦ 0.2 (2)

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention
An example of manufacturing a thin film pattern on an array substrate for an active matrix type liquid crystal display device using as switching elements will be described with reference to FIGS.

FIG. 1 is a schematic longitudinal sectional view for explaining a manufacturing process of an array substrate according to an embodiment, centering on manufacturing of a thin film pattern of a scanning line. FIG. 2 is a schematic longitudinal sectional view of the etching apparatus used in this embodiment.

First, the basic structure of the completed array substrate will be described with reference to FIG.

An array substrate for an active matrix type liquid crystal display device has scanning lines 105 arranged substantially in parallel and at equal intervals on a transparent insulating substrate 101 made of glass or the like, and scanning lines substantially orthogonal to the scanning lines 105. A signal line 116 electrically insulated from the scanning line 105 by a gate insulating film covering the scanning line 105, and an ITO (Indium) disposed for each matrix-shaped section formed by the scanning line 105 and the signal line 116.
A pixel electrode made of Tin Oxide) and an inversely staggered TFT 117 that is arranged near an intersection between the scanning line 105 and the signal line 116 and switches a signal input from the signal line 116 to the pixel electrode.

The scanning line 105 is made of an Al alloy containing 2 mol% (atomic%) of neodymium (Nd) (hereinafter abbreviated as Al-Nd alloy). On the scan line 105, a semiconductor film 109 made of an amorphous silicon (a-Si: H) film or the like is formed via a gate insulating film 108 made of silicon oxide (SiOx) or silicon nitride (SiNx). Have been.

On the semiconductor film 109, a channel protective film 113 is formed in a region corresponding to the channel portion of the TFT 117. The n ⁺ type a-Si: H is formed so as to sandwich the island-shaped channel protective film 113 from both sides. A contact layer 114 made of a semiconductor thin film is formed. A source electrode 111 and a drain electrode 112 are formed on the contact layer 114, and the drain electrode 112 is electrically connected to the signal line. The source electrode 111 and the drain electrode 112 and the back channel portion of the TFT 117 are covered with the protective insulating film 115.

Further, since the illustrated embodiment is an array substrate for a liquid crystal display device, a pixel electrode 110 made of ITO or the like electrically connected to the source electrode 111 is formed.

Next, an etching apparatus 200 used for forming a thin film pattern of the scanning line 105 will be described with reference to FIG.

The etching apparatus 200 includes a first etching chamber 210, a second etching chamber 220, and a washing chamber 230.
Is an in-line processing system directly connected to

The first etching chamber 210 performs etching until a thin film pattern is formed along the contour of the resist pattern 104, that is, until just etching. On the other hand, the second etching chamber 220
In the above, etching is further performed to remove the remaining undesired film. As described above, the productivity is improved by the in-line processing in which the two etching chambers 210 and 220 are directly connected.

As shown in FIG.
0, 220 and the washing room 230 have substantially the same structure,
An inner tank 203 for storing an etching solution or cleaning water is provided. These etching chambers 210 and 220 and the washing chamber 23
The lower half of 0 forms an outer tub 204 that houses the inner tub 203.

A transport roller 207 for holding the substrate 100 from above and below and moving it in the horizontal direction is provided in the inner tank 203.
Is provided, and a plurality of shower nozzles 206 are provided above the inner bath 203. These shower nozzles 206
Are arranged so that an etching solution or cleaning water is sprayed substantially uniformly over the array substrate (hereinafter simply referred to as a substrate) 100 being manufactured and conveyed. Further, when the etching roller or the like is sprayed on the substrate, and when the substrate 100 is subsequently immersed in the etching liquid or the like, the transport roller 207 is rotated in the rotation direction to uniformly spread the etching liquid or the like over the entire surface of the substrate 100. The switching (reversal) is repeated so that the substrate is reciprocated in small increments.

An entrance shower 208 for spraying an etching solution onto the substrate 100 is provided between the substrate insertion port 201 of each of the etching chambers 210 and 220 and the inner bath 203. The width of the liquid ejection port of the entrance shower 208 is larger than the width of the substrate 100 to be processed, and is configured so that the etching liquid is uniformly distributed over the entire surface of the substrate 100. In this manner, the etching target Al-
The reaction between the Nd alloy and the mixed acid as the etchant is made as uniform as possible in the plane of the substrate 100.

On the other hand, an air knife 209 is provided between the substrate outlet of each of the etching chambers 210 and 220 and the inner tank 203 to blow off the etchant on the substrate 100.

Although not shown in the drawing, in the present embodiment, the first etching chamber 210 is provided with an EPM (End point Monitor) for detecting the point of just etching. The EPM, for example, when detecting just etching of a metal thin film, continuously monitors the amount of reflected light, and captures a rapid change in the amount of reflected light when the thin film is removed and the base of the substrate is exposed. In such a case, for example, a point in time when the amount of reflected light becomes equal to or less than a predetermined amount of light is determined as just etching. The determination of the time of the just etching may be performed based on the amount of change in the reflected light amount, that is, the differential value. Alternatively, when the substrate 100 is of a transmission type, the change in the transmitted light amount may be captured.

The structure of the second etching chamber 220 and the washing chamber 230 is substantially the same as the first etching chamber 210 except that the EPM is not provided.

First and second etching chambers 210 and 220
Is an aqueous mixed acid solution (water-containing mixed acid) having the following composition.

If a volume (volume) of an 85% aqueous phosphoric acid solution A, a 90% aqueous acetic acid solution of volume B, and a 70% aqueous nitric acid solution of volume C are mixed, the following equations (1) and (2) are obtained. Fulfill.

0.2 ≦ A ÷ (B + C) ≦ 0.6 (1) 0.04 ≦ C ÷ (A + B + C) ≦ 0.2 (2) In the above description, the expression is in conformity with the convenience of the mixing operation.
Needless to say, this specifies the composition of the resulting mixed acid solution. For example, 10% instead of 90% acetic acid aqueous solution
Even if 0% acetic acid (glacial acetic acid) is used and a 60% aqueous nitric acid solution is used instead of the 70% aqueous nitric acid solution, the final composition may be within the range specified above.

When the composition of the etching solution is as described above, the photoresist used for patterning shrinks. Therefore, the photoresist and the metal thin film covered with the photoresist are formed along the contour of the resist pattern 104. The etchant penetrates into the interface between the first and second substrates. Therefore, the edge of the thin film pattern obtained by patterning is preferentially etched on the upper surface side to form a tapered cross section. In particular, the taper angle θ can be set to 45 ° or less, preferably 30 ° or less.

The etchant used in this example was heated to 40 ° C. in each case.

Next, the manufacturing process of the array substrate of the embodiment will be described with reference to FIGS. 1 (a) to 1 (d) in order.

FIG. 1A shows a state before the etching for forming the thin film pattern of the scanning line 105, that is, a state where the metal thin film 102 and the resist pattern 104 are formed on the transparent insulating substrate 101. .

More specifically, an Al—Nd alloy is deposited on a glass substrate having a size of 360 × 465 mm by sputtering to a thickness of 300 nm, and then a photoresist is applied. Is formed.

Any photoresist can be used as long as it has contractility to the above-mentioned etching solution, and a general acrylic photocurable resin can be suitably used.

FIG. 1B shows a resist pattern 104.
This shows a state at the time when the etching in the first etching chamber 210 reaches the just etching after the formation. Until it almost matches the contour of the resist pattern 104,
The metal thin film 102 is patterned.

First, the substrate 100 is put into the first etching chamber 210 through the substrate insertion port 201, and is passed through the entrance shower 208 for spraying the etching solution having the above composition.
The substrate 100 passes through the entrance shutter 202, is drawn into the inner tank 203 by the transport roller 207, and when the whole is drawn into the inner tank 203, the substrate 100 is drawn from the shower nozzle 206 disposed above the inner tank 203. Spraying of the etchant is started. Etching is performed for 9 seconds in this state. Thereafter, the inner tank 203 is filled with an etching solution over 6 seconds while continuously performing etching by spraying,
The substrate 100 is immersed in the etching solution.

When the substrate 100 is completely immersed in the etching solution, the supply of the etching solution is stopped, and the immersion is continued until the above-mentioned EPM determines that the etching is just etching. In this embodiment, the time from complete immersion to just etching is 110 to 1
15 seconds.

After completion of the etching up to the just etching, the substrate 100 is taken out on the liquid surface,
To extrude from the inner tank 203 to the discharge side. Then, the etching solution attached to the substrate 100 is removed by passing through the air knife 209, and then is sent to the second etching chamber 220.

FIG. 1C shows the second etching chamber 220.
Shows the state at the time when the further etching in step is completed.

In the second etching chamber 220, which operates in the same manner as the first etching chamber 210, first, etching is performed by spraying an etching solution for 9 seconds, and then the substrate is converted into the etching solution over 6 seconds while the etching solution is being sprayed. Soak.
When the substrate is completely immersed in the etching solution, the application of the etching solution is stopped, and the etching in this immersion state is performed for 50 to 60% of the immersion time in the first etching chamber.
, For 55 to 70 seconds.

Since the shrinkage of the photoresist due to the etching solution does not proceed beyond a certain amount, the taper angle of the edge of the obtained thin film pattern gradually increases as the etching time is made longer than the time until the just etching. According to repeated experiments, if the immersion etching time in the second etching chamber is 70% or less of the immersion etching time until the just etching in the first etching chamber, the taper angle should be 45 ° or less. Was completed.

After the completion of the etching in the second etching chamber, the substrate is taken out on the liquid surface, and the substrate is transferred to the washing chamber in the same manner as in the transfer from the first etching chamber to the second etching chamber. After washing with pure water in a washing room, drying was performed.

FIG. 1D shows a state in which the photoresist covering the thin film pattern of the scanning line 105 is removed.
The end face 105a of the thin film pattern of the scanning line 105 is
In a cross section perpendicular to the 00 plane, 3
Makes a 0 ° taper angle.

FIG. 1E shows a state after the completion of the array substrate. Hereinafter, with reference to this drawing, the outline of the manufacturing process from the formation of the thin film pattern of the scanning line 105 to the completion of the array substrate will be described.

First, a 350 nm-thick SiOx film and a 50 nm-thick SiONx film are successively deposited on the obtained thin film pattern of the scanning line 105 by the CVD method. In a reaction chamber (chamber), a-Si having a thickness of 50 nm for forming the semiconductor film 109:
H, and the film thickness 33 for forming the channel protective film 113
Continuous deposition of 0 nm SiNx.

After the substrate 100 is taken out of the CVD reaction chamber, a photoresist is applied again, exposure is performed by a back exposure technique using the thin film pattern of the scanning line 105 as a mask, and a predetermined mask pattern (photo After exposure using a mask, development is performed, and an island-shaped channel protective film 113 is formed through wet etching with hydrofluoric acid and peeling of a photoresist.

Next, the exposed surface of the semiconductor film 109 is treated with hydrofluoric acid so that a good ohmic contact can be obtained. Subsequently, a low-resistance semiconductor film 114 made of n ⁺ a-Si: H having a thickness of 50 nm and containing phosphorus as an impurity is deposited by a CVD method. Then, exposure and development are performed using a predetermined mask pattern, dry etching is performed by a CDE (chemical dry etching) method using a mixed gas of carbon tetrafluoride (CF ₄ ) and oxygen (O ₂ ), and photoresist is removed. By performing peeling, a pattern of the semiconductor film 109 to be a channel portion of the TFT is formed. On this, ITO is deposited by sputtering, and through a series of steps of coating, exposing and developing, etching, and removing the photoresist, the pixel electrode 110 is formed.
It was created.

Thereafter, a film thickness of 25
Molybdenum (Mo) layer with a thickness of 350 nm and aluminum
An (Al) layer and a 50 nm-thick molybdenum (Mo) layer are deposited in this order. Then, the signal line 116 and the source electrode 1 are exposed and developed by using a predetermined mask pattern.
11 and a resist pattern for the drain electrode 112 are formed, and then wet etching is performed using a mixed acid composed of phosphoric acid, nitric acid, acetic acid, and water as an etching solution.
The three-layer metal film of o, Al and Mo is patterned at once.

Further, the low-resistance semiconductor film 114 remaining on the channel protective film is removed by dry etching using the source and drain electrodes as a mask. This dry etching is performed by a PE (plasma etching) method using a mixed gas consisting of sulfur hexafluoride (SF ₆ ), hydrogen chloride (HCl), oxygen (O ₂ ), and helium (He). Then, the photoresist is removed.

Subsequently, silicon nitride (SiN
x) after the deposition, exposure using a predetermined mask pattern,
And development, sulfur hexafluoride (SF ₆ ), nitrogen (N ₂ ),
After dry etching by a PE method using a mixed gas of helium (He) and oxygen (O ₂ ) and peeling of a photoresist, a protective insulating film 115 was formed.
An array substrate as shown in (e) is completed.

As described above, according to the method for manufacturing a thin film pattern of the present embodiment, the obtained thin film can be formed without forming the metal thin film 102 for forming the scanning lines 105 into a laminated structure including a plurality of metal layers. The end face 105a of the pattern can be a sufficiently gentle slope with respect to the substrate surface. Accordingly, it is possible to sufficiently suppress the occurrence of insulation failure due to a defect of the insulating film covering the scanning line 105 while improving the productivity and reducing the material cost.

In the above-described embodiment, an example was described in which an Al-Nd alloy was used as the conductive thin film for forming the scanning line 105. However, metal aluminum or another aluminum alloy may be used. Further, a metal molybdenum or a molybdenum alloy such as a molybdenum-tungsten alloy (Mo-W) may be used.

In the above embodiment, a film made of amorphous silicon (a-Si: H) is used as the semiconductor film, but it is made of polycrystalline silicon (poly-Si) or microcrystalline silicon. It may be a film.

[0060]

According to the etching solution of the present invention and the method of manufacturing a thin film pattern using the same, the edge of the obtained thin film pattern can be formed without forming the thin film into a laminated structure composed of a plurality of layers having different etching rates. A sufficiently gentle taper shape can be obtained. Therefore, compared to the case where the thin film has a laminated structure, the productivity can be improved and the material cost can be reduced, and the manufacturing cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view for explaining a manufacturing process of an array substrate according to an embodiment. FIG. 1A shows a state before etching for forming a thin film pattern of a scanning line. FIG. 1B shows a state at the time when just etching is reached. FIG. 1C shows a state when the thin film pattern of the scanning line is completed in this way. FIG. 1D shows a state when the photoresist on the thin film pattern is peeled off. Also, in FIG. 1 (e),
This shows the state after the completion of the array substrate.

FIG. 2 is a schematic longitudinal sectional view of an etching apparatus used in the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Array substrate being manufactured 101 Glass substrate 102 Metal thin film (Al-Nd) 104 Resist pattern 105 Scan line 105 a End surface of scan line 200 Etching device 202 Entrance shutter 203 Inner tank 206 Shower nozzle on inner tank 207 Transport roller 208 Entrance shower 209 Air knife 210 First etching chamber 220 Second etching chamber 230 Rinse chamber

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01L 29/78 617K F term (Reference) 5F043 AA23 AA24 AA26 BB16 EE07 FF03 GG02 GG04 5F110 BB01 CC07 EE03 EE04 EE06 EE23 EE37 EE44 FF02 FF09 FF29 GG02 GG13 GG14 GG15 GG25 HK03 HK04 HK09 HK16 HK22 HK33 HM18 NN03 NN12 NN24 NN35 QQ05 QQ09

Claims (7)

[Claims] 1. An etching solution comprising phosphoric acid, acetic acid, nitric acid and water used for producing a thin film pattern along a resist pattern from a thin film deposited on a substrate, wherein an 85% phosphoric acid aqueous solution having a volume A is used. An etching solution characterized by satisfying the following formulas (1) and (2), assuming that a 90% aqueous acetic acid solution of volume B and a 70% aqueous solution of nitric acid of volume C are mixed. 0.2 ≦ A ÷ (B + C) ≦ 0.6 (1) 0.04 ≦ C ÷ (A + B + C) ≦ 0.2 (2) 2. A method for producing a thin film pattern along a resist pattern from a thin film deposited on a substrate using an etching solution comprising phosphoric acid, acetic acid, nitric acid and water, wherein the etching solution is If a volume A of 85% phosphoric acid aqueous solution, a volume B of 90% acetic acid aqueous solution and a volume C of 70% nitric acid aqueous solution are mixed, the following formulas (1) and (2) are satisfied. Method for producing a thin film pattern. 0.2 ≦ A ÷ (B + C) ≦ 0.6 (1) 0.04 ≦ C ÷ (A + B + C) ≦ 0.2 (2) 3. The method according to claim 2, wherein the edge of the obtained thin film pattern has a taper angle of less than 45 ° in a cross section perpendicular to the substrate surface. 4. The method according to claim 1, wherein the thin film is made of metallic aluminum (Al),
3. The method according to claim 2, wherein the alloy is mainly an aluminum alloy. 5. The method according to claim 2, wherein the thin film is made of metal molybdenum (Mo) or an alloy mainly composed of molybdenum. 6. The method according to claim 2, wherein said thin film has a thickness of 100 to 500 nm. 7. A first etching step for obtaining a pattern having the same contour as the resist pattern from the thin film, and a second etching step for performing over-etching, wherein these steps are performed using the same etching solution and etching temperature. When performed in, the time of the second etching step,
3. The method according to claim 2, wherein the time of the first etching step is 70% or less.