JP2003273079A - Resist ashing method of chrome mask and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to remove efficiently only a resist preventing change in properties of a chrome film and etching thereto, when the resist is removed from blanks prior to exposure and those posterior to exposure and development by means of dry ashing using O<SB>2</SB>gas. <P>SOLUTION: A resist ashing method, in which a resist film (70) is removed from the blanks formed with a light shielding chrome film (66) and the resist film (70) in a glass substrate (30), wherein by using O<SB>2</SB>gas as a reactive gas the resist film (70) is removed, changing the distance of the glass substrate (30) from a plasma source (12) and a driving voltage of the plasma source (12) with a glass substrate temperature kept less than a certain degree. The glass substrate (30) temperature is detected by means of a sensor (60) provided in a holding table (28) of the glass substrate (30) or the like, whereby the distance of the glass substrate (30) from the plasma source (12) and the driving voltage of the plasma source may be controlled so that the temperature may be kept less than a certain degree. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry ashing method and an apparatus for removing a resist film from a chromium mask used for manufacturing an LSI or the like.

[0002]

2. Description of the Related Art In the manufacture of an LSI (semiconductor integrated circuit), a liquid crystal display (LCD), a printed circuit board or the like, a pattern is transferred by lithography onto a flat substrate such as a silicon substrate, a glass substrate or a resin substrate. As the photomask used at this time, a photomask (hard mask) in which a light-shielding film of chromium (Cr) is formed on a glass substrate is used along with the miniaturization of patterns.

The reflectance of a single layer of metallic chromium is 40 to 50%.
Therefore, if a pattern is transferred using this mask, multiple reflection occurs with the projection exposure surface, and the imaging characteristics are degraded. Therefore, a two-layer type in which an interference film of chromium oxide (CrO) is formed on the surface of a chromium film (chrome light shielding film) is also used. In the mask for reduction exposure,
In order to reduce multiple reflection between the back surface of the mask (reticle) and the illumination system, a three-layer type in which a chromium oxide interference film is formed on the back surface of the chromium film is also used.

A resist (etching resist) is applied to the surface of the chromium film or the chromium oxide film thus formed on the glass substrate. Those in this state are called blanks (mask blanks, blanks). The blanks are exposed to a pattern, developed, and then the chromium film is etched. After this etching, the resist film (also referred to as a resist) is further removed to form a photomask.

[0005]

For removing the resist (peeling and cleaning), a chemical method using an acid obtained by adding hydrogen peroxide solution (H ₂ O ₂ ) to concentrated sulfuric acid (H ₂ SO ₄ ) is conventionally used. Is used. However, this method may change the surface of the chromium film due to the use of a strong acid, and the management is troublesome.

Therefore, it has been conventionally proposed to perform dry ashing in which the resist is made into a gas and exhausted. For example, it is a method using oxygen plasma or UV-ozone.
However, chromium has the property of being easily etched when the temperature rises, and even if it is an oxygen simple substance gas (O ₂ gas), it is easily etched when the chromium temperature exceeds 100 ° C. FIG. 6 shows an etching rate (mm / min, the thickness etched in 1 minute in mm) when chromium is etched using O ₂ simple substance gas. Etching Rate, E
/ R).

In order to keep the chromium film at a constant temperature (for example, 100 ° C.) or lower, the glass substrate may be brought into close contact with a holding table whose temperature is controlled at a constant temperature. That is, it is conceivable to use the holding table as a chiller. However, if the entire surface of the glass substrate is brought into close contact with the holding table, fine scratches may occur, which is not desirable.

The present invention has been made in view of such circumstances, and when the resist is removed from the blanks before exposure and after exposure / development by dry ashing using O ₂ gas, deterioration or etching of the chromium film is performed. A first object of the present invention is to provide a method of resist ashing of a chrome mask, which makes it possible to remove only the resist efficiently while preventing the above.

A second object of the present invention is to provide a chrome mask resist ashing apparatus used directly for carrying out this method.

[0010]

Means for Solving the Problems A first object according to the invention, in the resist ashing process for removing the plasma dry ashing a resist film from a blank to form a chromium light-shielding film and a resist film on a glass substrate, O ₂ Resist ashing of chrome mask characterized by removing the resist film while keeping the glass substrate temperature below a certain temperature while changing the distance from the plasma source of the glass substrate and the driving power of the plasma source by using the gas as a reaction gas. Method.

The temperature of the glass substrate is detected by a sensor provided on a holder for the glass substrate, and the distance of the glass substrate from the plasma source and the driving power of the plasma source can be controlled so as to keep the temperature below a certain level. it can.

The plasma source is a surface plasma (Surface Wave P) in which O ₂ gas is excited by a microwave through a quartz plate.
lasma, SWP) can be used. In this case, the O ₂ gas flow rate is 100 sccm (Standard cubic centimete
r) With the internal pressure of the vacuum vessel set to 15 Pa, the glass substrate can be separated from the quartz plate and ashed while the microwave power supply output is gradually or continuously reduced from 3000 Watts to 500 Watts. Glass substrate is 100
It is better to ash while keeping the temperature below ℃.

A second object of the present invention is to provide a chromium mask resist ashing apparatus for removing a resist film from a blank formed by forming a chromium light-shielding film and a resist film on a glass substrate. A vacuum container having a gas flow control valve for controlling the flow rate of the reaction gas supplied to the plasma generation unit, a plasma drive source for plasma-discharging the reaction gas in the plasma generation unit, and exhaust from the reaction chamber. And an evacuation pump for decompressing the inside of the vacuum container, a holder for holding the glass substrate in the reaction chamber so that the glass substrate can move up and down, and a reaction gas while exhausting the inside of the vacuum container while supplying the reaction gas into the vacuum container. While the plasma is discharged, the temperature of the glass substrate is controlled by changing the height of the holding table and the output of the plasma driving source. Resist ashing apparatus chromium mask, characterized in that it comprises a controller for plasma dry ashing a resist film having a chromium mask in the reaction chamber while maintaining below a constant temperature, and is achieved by.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view mainly showing the structure of a vacuum container of a resist ashing apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 10 is a vacuum container, the inside of which is a cylindrical plasma generating part 12 and the bottom thereof is a cylindrical reaction chamber 14. Plasma generator 1
A quartz plate 18, which is a dielectric, is fitted on the upper wall of 2.

A microwave 22 is guided from a microwave oscillator 24 to the upper surface of the quartz plate 18 by a waveguide 20. That is, surface waves are excited on the lower surface of the quartz plate 18 by microwaves leaking from holes (slot antennas) formed in the waveguide 20, and plasma is generated in the plasma generator 12 by the electric field (surface wave plasma, SW
P).

The plasma generating portion 12 has a smaller diameter than the reaction chamber 14, and its wall area is reduced to reduce the influence of the wall surface condition on the reaction. A reaction gas such as O ₂ gas can be supplied to the plasma generation unit 12 through the reaction gas introduction hole 26. A holding table 28 is provided in the reaction chamber 14 so as to be movable up and down, and a glass substrate 30, which is an object to be ashed, is held on the holding table 28. The holding table 28 is point-supported on the lower surface of the peripheral edge of the glass substrate 30 so that the lower surface of the pattern forming region of the glass substrate 30 is not scratched.

A horizontal annular straightening plate 32 is fixed to the inner surface of the reaction chamber 14, and an exhaust hole 34 is provided below the straightening plate 32.
Is open. A large number of small holes 34 are formed in the straightening vane 32 at equal intervals in the circumferential direction to stabilize the flow of the reaction gas in the reaction chamber 14.

Next, the operation of this device will be described. Glass substrate 3 which is an object to be processed to which an etching resist is attached
0 indicates a vacuum container 1 by a loading device (not shown).
0 is carried in and held on the holding table 28. A reaction gas of O ₂ gas is supplied from the reaction gas supply hole 26 while the substrate is held on the holding table 28.

On the other hand, the inside of the vacuum vessel 10 is depressurized by exhausting air from the exhaust hole 36. In this state, the microwave oscillator 24 is activated to guide the microwave to the plasma generator 12. Microwave takes advantage of the industrial microwave for example 2.45GH _z.

In this case, the reactive gas (O ₂ ) is turned into plasma, and the active oxygen radicals (O ^* ) generated by turning into plasma react with the resist which is the organic film. By this reaction, the resist becomes CO ₂ , CO, H ₂ O, etc. and is exhausted from the exhaust hole 36.

FIG. 2 is an overall configuration diagram of the ashing apparatus using the above-mentioned vacuum container, FIG. 3 is a diagram showing a chrome mask manufacturing process, FIG. 4 is an operation flow chart of this apparatus, and FIG. 5 is a substrate temperature according to this embodiment. It is a figure which shows the change of. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will not be repeated.

In FIG. 2, reference numeral 50 is an elevator for raising and lowering the holding table 28. Oxygen gas (O ₂ ) as a reaction gas is supplied from the supply source 52 through the flow control valve 54 to the reaction gas introduction hole 26 provided on the wall surface of the plasma generation unit 12.

A dry pump 56 is connected to the exhaust hole 36 provided in the lower portion of the reaction chamber 14. Vacuum container 10
The internal pressure is detected by a vacuum gauge (VG, Vacuum Gauge) 58. The holding table 28 supports the lower surface of the peripheral edge of the glass substrate 30, and a sensor 60 for detecting the temperature of the glass substrate 30 is attached to this supporting portion.

62 is a controller, which is a CPU 64,
It is composed of various interfaces. The controller 62 controls the ashing process of the glass substrate 30 (see FIG. 1) as described above.

Next, the manufacturing process of the chrome mask will be described with reference to FIG. A glass substrate 30 such as quartz glass is cleaned and prepared (FIG. 3A), and chromium (Cr) is provided on the upper surface thereof.
Is formed by sputtering or vapor deposition. A chromium oxide film 68 may be formed on the surface of the chromium film 66 (FIG. 3B). An etching resist 70, which is a photosensitive polymer material, is applied onto the chromium film 66 or the chromium oxide 68 by, for example, a spin coating method. As a result, blanks, which are mask substrates before patterning, are formed (FIG. 3C).

A pattern is formed on this blank (FIG. 3D). This pattern formation is performed by exposure and development by, for example, electron beam drawing or laser drawing. The resist 70 used here causes a chemical reaction with an electron beam or a light beam used for drawing (exposure) to form a mask pattern on the blank. By utilizing the difference in solubility and the difference in dissolution rate of the exposed portion caused by the development, the resist 68 on the portion other than the pattern to be left as the chromium film is removed.

The glass substrate 30 in this state, that is, the glass substrate 30 on which the pattern has been exposed and developed is wet-etched, for example (FIG. 3E). The etchant used here may be, for example, a ceric ammonium nitrate-based one also called Kodak specification. As a result of such etching, the portions of the chromium film 66 and the chromium oxide film 68 which are unnecessary for the pattern are removed.

The glass substrate 30 which has been etched is held on the holding table 28 in the vacuum container 10 shown in FIGS. 1 and 2, and the resist 70 is dry-ashed (FIG. 3).
(F)). In this ashing, the controller 6
2 indicates that the glass substrate 30 has a constant temperature, for example, 100 ° C.
The plasma source driving power and the height of the holding table 28 are controlled so as not to exceed the limit.

FIG. 4 is a flow chart of this ashing operation, and FIG.
FIG. 4 is a diagram for explaining changes in the substrate temperature. When the controller 62 enters this ashing process (FIG. 4, step S100), first, the reaction gas (O ₂ ) flow rate control valve 54
The opening degree is controlled and the exhaust pump 56 exhausts air (step S102).

The flow rate of O ₂ gas is a set value (for example, 100 s).
When the degree of vacuum in the vacuum container 10 detected by the vacuum gauge 58 is stabilized at a set value (for example, 15 Pa) (step S104), the controller 62 activates the microwave oscillator 24, and the CPU 64 causes the CPU 64 to operate. The elapsed time t after the start of operation of the oscillator 24 is measured (step S106).

The controller 62 reduces the output of the oscillator 24 as the elapsed time t increases, and the holding table 2
Lower 8 That is, until the elapsed time (that is, discharge time) t becomes t ₁ = 5 minutes, the oscillator output (microwave power) is set to P = P ₀ (= 3000) Watt,
The upper surface of the glass substrate 30 is set to a start position x, that is, a position x where G is the distance between the upper surface of the glass substrate 30 and the lower surface of the quartz plate 18. When the elapsed time t reaches t = t ₁ (= 5 minutes) (step S108), the oscillation output is changed to P = P ₁ (= 200).
0) Set to Watt and lower the holding table 28 by 20 mm (step S110).

Until the end time t = t _E (= 20 minutes) is reached (step S112), t is t ₂ (= 10 minutes),
Every time t ₃ (= 15 minutes), the oscillation output is changed to P = P ₂ (= 10
00), P = P ₃ (= 500) Watt, and the holding table 28 is lowered by 40 mm and 60 mm (steps S114, S108, S110, S112). When t = t _E (= 20 minutes) (step S11)
2), ashing is completed (step S116).

FIG. 5 shows the glass substrate 3 when the oscillation output P and the height of the holder 28 are changed with the passage of time.
The result of having measured the temperature change of 0 is shown. From FIG. 5, it was found that the substrate temperature T never exceeded 100 ° C. Therefore, it was found that the chrome film 66 or the chrome oxide film 68 was not etched by the ashing. Further, it can be seen from FIG. 6 that only Cr can ash at 100 ° C. or lower.

In this embodiment, the oscillation elapsed time t of the oscillator is
Although the oscillation output P and the height of the holding table 28 are both controlled by measuring the time, the present invention predicts the temperature rise based on the detected temperature of the substrate 30 and predicts the oscillation output P and the holding table 2.
The height of 8 may be controlled. In this case, the sensor 60 provided on the substrate supporting portion of the holding table 28 that supports the glass substrate 30 at a point.
Thus, the temperature of the substrate can be detected. The controller 62 may control one of the oscillation output P and the height of the holding table 28.

[0035]

As described above, according to the inventions of claims 1 to 4, O
_{(2) When} dry ashing the resist of the chromium mask using the gas as the reaction gas, change the driving power of the plasma source and the distance from the glass substrate to the plasma source so that the temperature of the glass substrate does not exceed a certain temperature. Therefore, it is possible to remove only the resist while preventing the chromium film and the chromium oxide film from being altered or etched.

According to the inventions of claims 5 to 7, there is provided an ashing device used directly for carrying out the method.

[Brief description of drawings]

FIG. 1 is a view showing a vacuum container of a microwave plasma ashing device used for carrying out the present invention.

FIG. 2 is a diagram showing an overall configuration of an ashing device.

FIG. 3 is a diagram showing a chrome mask manufacturing process.

FIG. 4 is an operation flow chart of the method of the present invention.

FIG. 5 is a diagram showing changes in substrate temperature.

FIG. 6 is a diagram showing temperature dependence of chromium etching rate.

[Explanation of symbols]

10 vacuum container 12 Plasma generator 14 Reaction chamber 26 Reaction gas supply hole 28 holding table 30 glass substrate (processing object) 36 Exhaust hole 50 elevator 60 sensor 62 controller 66 chrome film 68 Chromium oxide film 70 Resist

Claims (7)

[Claims] 1. A resist ashing method for removing a resist film from a blank formed by forming a chrome light-shielding film and a resist film on a glass substrate by plasma dry ashing, wherein O ₂ gas is used as a reaction gas, and the distance from the plasma source of the glass substrate and While changing the driving power of the plasma source,
A method for resist ashing a chromium mask, which comprises removing the resist film while keeping the temperature of the glass substrate below a certain temperature. 2. The resist ashing of the chromium mask according to claim 1, wherein the temperature of the glass substrate is detected, and the distance from the plasma source to the glass substrate and the driving power of the plasma source are controlled so as to keep the detected temperature below a certain temperature. Method. 3. The plasma dry ashing is performed by using a plasma excited by an O ₂ gas supplied to the inside of a vacuum container with a microwave introduced from the outside through a quartz plate, and a microwave power output from 3000 Watt to 500 Watt.
The resist ashing method for a chrome mask according to claim 1, wherein the ashing is performed while gradually lowering to Watt and separating the glass substrate from the quartz plate. 4. The method of resist ashing a chromium mask according to claim 1, wherein the ashing is performed while maintaining the temperature of the glass substrate at 100 ° C. or lower. 5. A vacuum container having a plasma generation part and a reaction chamber thereunder, in a chromium mask resist ashing device for removing a resist film from a blank formed by forming a chromium light-shielding film and a resist film on a glass substrate. A gas flow rate control valve for controlling the flow rate of the reaction gas supplied to the generation unit, a plasma drive source for plasma-discharging the reaction gas in the plasma generation unit, and an exhaust for exhausting the reaction chamber to reduce the pressure in the vacuum container. A pump, a holding table for holding the glass substrate in the reaction chamber so that the glass substrate can be raised and lowered, and a plasma discharge of the reaction gas while exhausting the inside of the vacuum container while supplying the reaction gas into the vacuum container. Reaction by keeping the temperature of the glass substrate below a certain temperature by changing the height of the plasma and the output of the plasma drive source. A chrome mask resist ashing apparatus comprising: a controller for performing plasma dry ashing of a chrome mask resist film in a room. 6. The plasma driving source includes a quartz plate which is an upper wall of a vacuum container, a microwave oscillator, and a waveguide which guides the microwave output from the microwave oscillator from the outside of the vacuum container to the quartz plate. The chrome mask resist ashing apparatus according to claim 5, further comprising: 7. The holding table supports the lower edge of the glass substrate, and a sensor for detecting the temperature of the glass substrate is attached to the holding table, and the controller keeps the temperature detected by the sensor below a certain temperature. 7. The chrome mask resist ashing apparatus according to claim 5, wherein the height of the holding table and the output of the plasma driving source are changed.