JP3348305B2 - Pattern forming method of chromium-based material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a pattern on a chromium-based material. This type of technique can be used, for example, for forming a photomask used when manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In general, a photomask is formed by forming a chromium-based material film having excellent light-shielding properties on a transparent substrate such as glass or quartz and processing it into a fine pattern. In such a case, a technique of wet-etching a chromium-based material using a patterned resist film as a mask has been used, but with this technique, the dimensional variation between the finished chromium-based material pattern and the resist pattern has been used. The difference was large, miniaturization could not be realized, and dimensional controllability was not always good.

For this reason, it has been considered to apply a dry etching technique using an etching gas. However, an electron beam resist material suitable for high-precision microfabrication has poor dry etching resistance and is a bottleneck for practical use. Was.

For example, poly [2,2,2-trifluoro, which is a material having a skeleton containing a halogen atom, is used.
[Ethyl-α-chloroacryl] as a main component is a positive electron beam resist material (such as that referred to as EBR-9) itself, which is a material suitable for high-precision fine processing, but has low dry etching resistance. , chromium-containing material is practically like may resist disappears tinged difficult before being etched.

Therefore, the present applicant has already carried out dry etching with a mixed gas containing chlorine, oxygen and hydrogen (for example, a mixed gas of chlorine gas, oxygen gas and wet air or wet nitrogen gas), and A technique for achieving good high-precision fine processing even with a resist material having low dry etching resistance has been proposed (Japanese Patent Laid-Open No. 3-3).
3848).

[0006]

However, in the above proposal, for example, chlorine gas 160 SCCM,
A mixed gas composed of 40 SCCM of oxygen gas and 160 SCCM of wet air is used. This is because the flow rate of the wet air is about 0.44 of the whole. At this ratio, when this is applied to the photomask pattern forming technology, there is a limit to the improvement of the in-plane line width uniformity even if other conditions are controlled. As a similar wet air flow rate ratio,
In the case where the chlorine gas 40 SCCM, the oxygen gas 160 SCCM, and the wet air 165 SCCM are selected and executed (wet air ratio: about 0.45), the in-plane line width uniformity that can be realized is 1.75 μm line width (photo mask In terms of the semiconductor device to be processed, 0.35μ
3σ = 0.08 μm for a 16 MSRAM or 64 MDRAM class with m dimensions). This did not satisfy the line width uniformity of 0.05 μm required for a device mask of this class, and was an obstacle to the establishment of high-precision device process technology.

Recently, as a light-shielding film used for a photomask, a two-layer chromium film (for example, 300% chromium oxide / 750% chromium oxide) is used as a light-shielding film to be processed, because of the need for lowering stress, improving acid resistance, and reducing reflection. However, the same problem as described above arises in this case.

To improve the in-plane line width uniformity, wet etching which has been used for a long time may be employed. However, original problems such as defective defects such as missing defects occur again. In the case of a two-layer chromium film, there is a problem that the profile is deteriorated due to the undercut of the lower layer chromium and the cleaning property is thereby deteriorated. That is, in the case of a two-layer chromium film, as shown in FIG. 5, when the lower Cr film 2 and the upper chromium oxide film 3 on a substrate 1 made of quartz or the like are wet-etched, an undercut occurs in the lower Cr film 2 as shown in the figure. However, inconveniences such as contamination or chemical solution remaining therein occur. After all, wet etching technology is not a solution.

[0009]

An object of the present invention is to solve the above-mentioned problems, and to pattern a chromium-based material using a positive-type electron beam resist capable of high-precision and fine processing. Pattern processing can be realized, and furthermore, processing uniformity within the surface to be processed can be improved, accurate and reliable fine processing can be achieved, and contamination problems such as adhesion of foreign substances due to cleaning are small. It is intended to provide a forming method.

[0010]

According to a first aspect of the present invention, there is provided a chromium-based material pattern forming method for etching a chromium-based material using a positive electron beam resist to form a pattern. Chlorine gas,
A mixed gas of oxygen gas and air containing moisture or nitrogen gas containing moisture is used, and the water in the mixed gas is used.
Content of air containing nitrogen or nitrogen gas containing moisture .
A method for forming a pattern of a chromium-based material, characterized by being in the range of 600 to 0.720, thereby achieving the above object.

The invention according to claim 2 of the present application is the method for forming a pattern of a chromium-based material according to claim 1, wherein the positive-type electron beam resist is made of a material having a skeleton containing a halogen atom. Thus, the above object is achieved.

The invention according to claim 3 of the present application is the method for forming a pattern of a chromium-based material according to claim 1, wherein the positive electron beam resist is made of a material having a skeleton containing a fluorine atom. Thus, the above object is achieved.

According to a fourth aspect of the present invention, the positive electron beam resist has a fluorine atom-containing skeleton having a substituent containing a chlorine atom. It is a forming method, thereby achieving the above object.

According to the invention of claim 5 of the present application, the positive type electron beam resist is made of poly [2,2,2-trifluor.
The pattern forming method for a chromium-based material according to claim 1, wherein the above object is achieved.

According to the invention of claim 6 of the present application, the pattern of the chromium-based material according to claim 1, wherein the positive-type electron beam resist has at least an acrylic component as a homopolymerization component or a copolymerization component. It is a forming method, thereby achieving the above object.

The invention according to claim 7 of the present application is the chromium-based resist according to claim 1, wherein the positive-type electron beam resist has, as a homopolymerization component or a copolymerization component, a component providing a PMMA polymer. A method for forming a pattern of a material, which achieves the above object.

The invention according to claim 8 of the present application is the method according to any one of claims 1 to 7, wherein the chromium-based material is a material containing chromium or chromium oxide. Thus, the above object is achieved.

According to a ninth aspect of the present invention, the chromium-based material has a laminated structure of a chromium-based material film, and the chromium-based material pattern forming method according to any one of claims 1 to 7, wherein Thus, the above object is achieved.

The invention according to claim 10 of the present application is the method according to any one of claims 1 to 7, wherein the chromium-based material has a chromium oxide / chromium structure or a chromium oxide / chromium / chromium oxide structure. And a method for forming a pattern of a chromium-based material, thereby achieving the above object.

[0020]

[0021]

[0022]

According to the present invention , when a pattern is formed by etching a chromium-based material using a positive electron beam resist, chlorine gas, oxygen gas, and water are used as etching gases.
Air containing moisture or nitrogen gas containing moisture (hereinafter
Using a mixed gas of sometimes referred to as the hydrogen-oxygen gas "), air or moisture containing the moisture of the mixed gas
When the content rate of the contained nitrogen gas is in the range of 0.600 to 0.720, the in-plane uniformity is remarkably improved.

FIG. 1 shows a simulation of in-plane uniformity when a chromium-based material on a substrate surface is etched using a 5-inch square substrate based on experiments at a plurality of points and an experiment design method. In the case of point A in the range of the present invention in which the flow rate ratio of the hydrogen-containing / oxygen gas (here, wet air is used) in the mixed gas for etching is 0.657, the etching uniformity is obtained. The characteristic is 38.000 nm in line width, whereas at point B (flow ratio 0.521) which is out of the range of the present invention, 51.667 n
At points m and C (flow rate ratio: 0.452), it was 54.333 nm.

Specifically, when the data of FIG. 1 is taken, the etching gas component at the point A is chlorine gas / oxygen gas /
Wet air = 25/100/240 SCCM,
At point B, chlorine gas / oxygen gas / wet air = 30/12
0/215 SCCM, and at a point C, chlorine gas / oxygen gas / wet air = 40/160/165 SCCM.

In the invention of the present application, the mechanism of action for setting the ratio of the hydrogen-containing / oxygen gas in the mixed gas for etching to the above range is not necessarily clear, but at least the ratio is centered at about 0.66. The above range (particularly in the above experiment, 220 to 260 SCC in a total flow rate of 365 SCCM)
It is experimentally clear that when the ratio is in the range of M), the etching uniformity can be remarkably improved.

[0026]

Next, embodiments of the present invention will be described with reference to the drawings. However, needless to say, the present invention is not limited by the embodiments.

Example 1 In this example, the present invention was applied to pattern formation of a chromium-based material on a light transmitting substrate for forming a photomask.

First, the structure of a general photomask will be described. As shown in FIG. 2A, the structure of the photomask includes a structure in which Cr, which is a chrome-based light-shielding material 2, is provided on a light-transmitting substrate (quartz) 1, which is a light-transmitting portion. As shown in FIG. 2B, a two-layer Cr substrate with a low-reflection film of a substrate (quartz) 1 / chrome-based light-shielding material (Cr) 2 / chrome-based light-shielding material (chromium oxide CrOx) 3 is used. is there.

In recent photomasks (reticles), the amount of pattern position shift due to film stress is reduced by lowering the stress.
The structure shown in FIG. 2 (b) has been increasingly adopted because of its excellent acid resistance, improvement of reticle surface cleanliness, and reduction of light reflection between a wafer and a reticle in a stepper. Also in this example, a chromium-based material pattern was formed for forming the photomask having the structure shown in FIG.

FIG. 3 shows an example of the configuration of an etching apparatus used in this embodiment. This device is a parallel plate type RIE device composed of an upper electrode 4 and a lower electrode 5, and a high frequency power supply 6 (13.56 MHz) is connected between the electrodes 4 and 5.

Cl ₂ which is a gas used for etching,
O ₂ and hydrogen-containing / oxygen gas (wet air or wet nitrogen, etc.) are respectively introduced from different supply sources by gas introduction pipes 71 to 73, mixed in the introduction pipe 7, and then mixed with the upper electrode 4. From the gas supply port provided in the reaction chamber 8
Supplied within. The flow rates of the respective gases are independently controlled by controllers (mass flow controllers) installed in the supply pipes 71, 72, 73 of the respective gases.
Gas pressure during etching, control is control by the adjusting the exhaust rate in opening degree of the installed valve in the middle of the exhaust pipe. RF power (W) as an etching parameter
Pressure (Pa) Gas flow electrode temperature at each electrode interval (6) Etching time and the like can be changed by software (program), and setting can be made by changing the conditions of two or more steps for one processing.

In this embodiment, when dry etching is performed using the above-described etching apparatus shown in FIG. 3, first, a photomask substrate 9 having a resist pattern after development and post-bake, which is an object to be etched, is placed on a lower electrode. Put on 5

Next, Cl ₂ , O
₂ and in this embodiment, a mixed gas of wet air is introduced. Here, a square with a side of 5 inches and a thickness of 0.0
A 9-inch quartz mask substrate was used as a substrate to be processed. Cl ₂ 25 SCCM, O ₂ 100 SCC as etching gas
M, wet air (air containing saturated steam at 25 ° C)
A mixed gas of 240 SCCM is introduced into the reaction chamber 8, the gas pressure in the reaction chamber 8 is set to 160 mTorr, and the distance between the upper electrode 4 and the lower electrode 5 is set to 130 mm.

Thereafter, a high-frequency voltage (RF power 150 W) is applied between the upper electrode 4 and the lower electrode 5 to convert the introduced gas into plasma. This plasma etches the upper chromium-based light-shielding material 3 (chromium oxide; see FIG. 2B) that is exposed on the photomask 9 and is not covered with the resist. The lower chromium-based light-shielding material 2 (chromium), which is the lower layer of chromium oxide, which is the upper chromium-based light-shielding material 3
Also, etching can be performed continuously under the same conditions.

As a result, a processing line width of 1.75 μm and a single line of 110 mm square, 3σ = 0.05 μm were achieved. This satisfies the required accuracy of the 0.35 μm device reticle.

In this embodiment, as the electron beam resist material, a positive type electron beam resist EBR-9 was used.
(2,2,2-trifluoroethyl-α-chloroacrylate; manufactured by Toray Industries, Inc.). As the thickness of the chromium-based light-shielding material film and the thickness of the electron beam resist film, the thickness at the time of forming a general photomask was adopted.

In this embodiment, a wet air supply device 20 as shown in FIG. 4 was used. This wet air supply device 20 is obtained by injecting water 22 into a container 21,
A wet air outlet pipe 24 and an air inlet pipe 25 are attached to the lid 23. The lid portion 23 is in close contact with the container 22, and when air is introduced into the container from the air introduction tube 25 having an end below the water surface, high-humidity air is led out from the wet air outlet tube 24. The wet air outlet pipe 24 is connected to the wet air inlet pipe 73 (see FIG. 3). Therefore, when the inside of the reaction chamber 8 is evacuated, the inside of the container 22 is depressurized and the required wet air is discharged. Is supplied to the inside of the reaction chamber 8.

According to the present embodiment, the composition ratio of the etching gas is selected to be chlorine gas (Cl ₂ ) / oxygen gas (O ₂ ) / hydrogen-containing / oxygen gas (wet air) = 25/100/240. In-plane line width uniformity is improved (1.75 μm)
The accuracy required for devices with m-line width of 3σ = 0.035 µm) and 0.35 µm is improved by using a two-layer chrome film (chromium oxide /
This can be achieved by dry etching using a (chromium) substrate (of course, this is also possible with a single-layer chromium film).

As described above, since dry etching can be performed using a two-layer chromium film that is advantageous in the photolithography process, the problem of insufficient missing or undercut when wet etching is employed can be avoided.

The cross-sectional shape of the two-layer chromium without undercut has high cleanliness and can significantly reduce the adhesion of foreign matter after reticle cleaning.

Example 2 In the same manner as in the above example, a quartz mask substrate having a square of 6 inches on a side and a thickness of 0.25 inches was etched by the apparatus shown in FIG. The etching gas is Cl ₂ 25S
CCM, O ₂ 100SCCM, wet air 240SC
A mixed gas of CM was used. This is introduced into the reaction chamber 8,
In this embodiment, the gas pressure in the reaction chamber 8 is set to 140 mTorr,
The distance between the upper electrode 4 and the lower electrode 5 is set to 100 mm. Thereafter, a high-frequency voltage (RF power: 180 W) is applied between the upper electrode 4 and the lower electrode 5, and the introduced gas is turned into plasma. This plasma etches chromium oxide, which is the upper chromium-based light-shielding material, and then continuously etches Cr, which is the lower chromium-based light-shielding material.

As a result, the processing line width is 1.75 μm, and a single line has a size of 110 mm square and 3σ = 0.035 μm.
Was achieved. This satisfies the accuracy of a 0.25 μm device reticle.

In this embodiment and the first embodiment, when the size and thickness of the substrate to be etched are changed, it is not necessary to change the hardware in the same apparatus. This is an example in which the etching rate and the selection ratio are optimized.

Further, both Examples 1 and 2 show conditions under which etching can be performed with good uniformity while minimizing damage to the edge portion of the chromium oxide layer due to poor electron beam resist profile and small influence of dry etching properties. .

Comparative Example Here, for comparison, Cl ₂ 40 SCCM, O ₂ 160
The operation was performed in the same manner as in Example 1 except that a mixed gas of SCCM and 165 SCCM of wet air was used. As a result, the uniformity of the processing was σ =
While 0.035, σ was about 0.046.

Embodiment 3 In this embodiment, instead of wet air, wet N
₂ (nitrogen) was used. That is, in the apparatus shown in FIG. 4 used in Example 1, by supplying nitrogen to the air introduction pipe 25, wet N ₂ containing saturated steam at 25 ° C. was supplied. Others were performed similarly to Example 1. According to this embodiment, effects similar to those of the first embodiment were obtained.

Embodiment 4 In this embodiment, PMMA was used as a positive electron beam resist.
A system resist and a PMMA copolymer resist were used. Others were the same as Example 1. Thus, even when the PMMA-based resist material was used, the same effect as in Example 1 was obtained.

[0048]

According to the present invention, when patterning a chromium-based material using a positive-type electron beam resist, good pattern processing can be realized without any problem with respect to the resistance of the resist, and the pattern within the surface to be processed can be realized. Processing uniformity can be improved, and fine processing with high precision and good quality can be effectively achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the content ratio of hydrogen-containing / oxygen gas in an etching gas and etching uniformity.

FIG. 2 is a cross-sectional view showing a structure of a photomask as a workpiece.

FIG. 3 is a diagram illustrating a configuration example of an etching apparatus used in the embodiment.

FIG. 4 is a configuration diagram showing a wet air supply device used in the embodiment.

FIG. 5 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

 Reference Signs List 1 light transmitting substrate 2 chromium-based material (chromium) 3 chromium-based material (chromium oxide)

Claims (10)

(57) [Claims] In a method of forming a pattern of a chromium-based material by etching a chromium-based material using a positive electron beam resist, chlorine gas, oxygen gas, and moisture are used as etching gases.
With a mixed gas of nitrogen gas containing air or moisture comprising, nitrogen containing air or water including the water content of the mixed gas
A method for forming a pattern of a chromium-based material, wherein the content of the elemental gas is in the range of 0.600 to 0.720. 2. The method according to claim 1, wherein the positive type electron beam resist is made of a material having a skeleton containing a halogen atom. 3. A positive electron beam resist comprising a material having a skeleton containing a fluorine atom.
3. A pattern forming method for a chromium-based material according to item 1. 4. The method for forming a pattern of a chromium-based material according to claim 1, wherein the positive electron beam resist has a fluorine atom-containing skeleton having a substituent containing a chlorine atom. 5. The method according to claim 1, wherein the positive electron beam resist is poly [2,
2,2-trifluoroethyl-α-chlo
2. The method for forming a pattern of a chromium-based material according to claim 1, wherein 6. The method for forming a pattern of a chromium-based material according to claim 1, wherein the positive electron beam resist has at least an acrylic component as a homopolymerization component or a copolymerization component. 7. The method for forming a pattern of a chromium-based material according to claim 1, wherein the positive electron beam resist has a component that gives a PMMA-based polymer as a homopolymerization component or a copolymerization component. 8. The pattern forming method for a chromium-based material according to claim 1, wherein the chromium-based material is a material containing chromium or chromium oxide. 9. The method according to claim 1, wherein the chromium-based material has a layer structure of a chromium-based material film. 10. A pattern forming method for a chromium-based material according to claim 1, wherein the chromium-based material has a chromium oxide / chromium structure or a chromium oxide / chromium / chromium oxide structure. .