JP2001059193A - Production of x-ray mask, and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for producing an X-ray mask by which the starting point and end point of etching are detected with high precision even in the case the etching area is very small, the reproducibility of the etching in the producing process of the X-ray mask is enhanced, and the formation of patterns high in precision is realized. SOLUTION: The method for producing an X-ray mask comprises at least a stage in which a light receiving means monitoring the light emitting intensity of plasma in an etching chamber is arranged, the light emitting of chemical seed in the plasma is dispersed and detected, the signal of the light emitting intensity of the chemical seed in the plasma is subjected to a set calculating treatment, and the starting point and end point of the etching are discriminated and a stage in which, after the passage of a prescribed time after the starting or end point of the etching, the etching conditions are changed or the etching is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming technique widely used in the manufacture of semiconductor integrated circuits and the like, and more particularly to a technique for forming an integrated circuit pattern on a substrate made of a semiconductor or glass material using X-rays. The present invention relates to a method for detecting a start point and an end point in an etching process in manufacturing an X-ray mask used in so-called X-ray lithography technology and the like, and an etching apparatus using the same.

[0002]

2. Description of the Related Art In the etching of an X-ray absorber in the manufacture of an X-ray mask, the surface of the absorber to be etched is covered with a relatively stable natural oxide film. It takes time to remove, and a time delay occurs before the etching of the absorber film itself starts. This delay time largely depends on the state of the film surface and the state of the plasma. The surface state of the film is slightly different depending on handling in a film forming step, a pattern forming step, and a pre-etching step such as formation of an etching mask. Further, the plasma state is not always the same every time etching is performed.
For this reason, there is a difference in the etching delay time for each wafer, and in the etching controlled by the time, the actual etching time varies, thereby reducing the reproducibility of the etching accuracy. In the etching step, an etching method for changing a plasma state such as a gas condition and power during etching is often used to control a pattern shape. Normally, the conditions are changed and the conditions are switched.However, if there is a variation in the etching start time, the actual etching conditions will be different for each wafer, which is a factor that reduces the reproducibility of the etching accuracy. Had become. Even when performing over-etching, if the end point of etching is not directly detected but is determined by time, the actual over-etch time varies, causing a reduction in the reproducibility of etching accuracy. Under such circumstances, it has been required to directly monitor the start and end of the etching. As a method of detecting the start and end of etching, there are a method of monitoring a signal of mass spectrometry of a reaction product and a method of monitoring light emission from the reaction product, which may be used in an LSI manufacturing process. . The method of monitoring the light emission from the reaction product is, for example, when etching Si on the entire surface of a large substrate such as 6 inches or 8 inches, by monitoring the intensity of the emission wavelength region of the reaction product of Si. Start point and end point were detected. Further, since the amount of the reaction product was large, it was not necessary to increase the detection accuracy. Further, since the conventional reaction product of Si has a small molecular weight, its energy level is dispersed, and its emission spectrum has only a few isolated peaks. in this case,
When the wavelength resolution was rough, the background became large, and the detection accuracy became poor. In the case of a reaction product of Ta, the energy level is fine because the molecular weight is larger than that of Si, and the emission spectrum has many peaks near a certain wavelength. Therefore, when the wavelength resolution is roughened, the sensitivity is improved and the influence of the background is small, so that the detection accuracy is improved and even a small amount of reaction product can be detected. However, in the manufacture of an X-ray mask, the area to be used is about 25 mm square at the center of the wafer, and furthermore, a very small part of the circuit pattern drawn therein is processed. Extremely small compared to the LSI manufacturing process,
It is difficult to monitor a minute change in the plasma state due to the start of etching by mass spectrometry or light emission. For this reason, the actual state is that the etching rate and the required etching time are previously derived using a dummy wafer, and the start and end times of the etching are determined based on the results.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned situation in the prior art, and has as its object to disperse light emission from a plasma during etching to be involved in an etching reaction. By monitoring the change in emission intensity of chemical species with high sensitivity, even if the etching area is small, the start and end points of etching can be detected with high accuracy, and the reproducibility of etching in the manufacturing process of the X-ray mask It is an object of the present invention to provide a method for manufacturing an X-ray mask capable of realizing a highly accurate pattern formation and an apparatus for implementing the same.

[0004]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, in a method for manufacturing an X-ray mask using an etching apparatus using plasma, a light receiving means for monitoring the light emission intensity of the plasma in an etching chamber of the etching apparatus is provided. Detecting the emission intensity signal by dispersing the emission of the chemical species of the chemical species, determining the start point and end point of the etching by performing a set arithmetic processing on the emission intensity signal of the chemical species in the plasma, After the elapse of a predetermined time from the start or end of the process, the method for manufacturing an X-ray mask includes at least a step of changing etching conditions or a step of stopping etching.
The calculation processing of the setting here means, for example, dividing the emission intensity within a predetermined wavelength range of the emission intensity signal of the chemical species in the plasma by the emission intensity of another wavelength for canceling the variation of the plasma itself. Means to increase the accuracy of the starting point and the ending point of the etching. According to a second aspect of the present invention, in the first aspect, there is provided a method of manufacturing an X-ray mask using an optical filter or a spectroscope as a means for dispersing chemical species in plasma. Further, as described in claim 3, in claim 1 or claim 2, a gas containing at least chlorine is used as an etching gas,
And at least tantalum (Ta) as an etching target
The determination of the starting point and the ending point of the etching is performed by using an X-ray absorber including a method of manufacturing an X-ray mask using light emission in a wavelength range of 220 nm to 350 nm in plasma or light emission in a specific wavelength range within the above wavelength range. Is what you do.
According to a fourth aspect of the present invention, in the third aspect, the emission intensity in the wavelength range of 220 nm to 350 nm in the plasma is divided by the emission intensity of another wavelength in the vicinity of the wavelength.
An object of the present invention is to provide a method for manufacturing an X-ray mask including a step of canceling the fluctuation of the plasma itself, improving the S / N (signal / noise) ratio, and increasing the positional accuracy of the etching start and end points. Further, as described in claim 5, the X according to any one of claims 1 to 4
What is claimed is: 1. A plasma etching apparatus for performing a method of manufacturing a line mask, comprising: means for receiving plasma emission in an etching chamber of the etching apparatus; and a specific wavelength of an emission spectrum of a chemical species comprising an etching gas and a reaction product during etching. A spectroscope or an optical filter for extracting light, a means for measuring the emission intensity of the chemical species in the plasma in the etching chamber, and when the emission intensity reaches a predetermined value, determining a start point and an end point of the etching; An X-ray mask manufacturing apparatus having at least means for changing the etching conditions after a predetermined time from the start or end point, or means for stopping the etching.

According to the present invention, means for dispersing and receiving plasma emission is disposed in a plasma etching apparatus, and emission spectrum intensity from chemical species involved in an etching reaction, preferably emission in a wavelength region of 220 nm to 350 nm, or A control unit that monitors the emission intensity of a specific wavelength in the region, determines the start and end points of the etching when the intensity reaches a predetermined value, and changes the etching conditions after a predetermined time or stops the etching. Is used. The present invention relates to a method of manufacturing an X-ray mask by plasma etching as described in claims 1 to 5 above.
By monitoring the change in the emission intensity at a wavelength of 20 nm to 350 nm, the start point and the end point of the etching of the Ta-containing material can be determined with high sensitivity even when the etching area is small. There is an effect that the pattern formation of the mask absorber can be realized with high reproducibility and high accuracy.

FIG. 1 shows chlorine (Cl) as an etching gas.
₂ ) Comparison of plasma emission spectra when etching is not performed and when Ta formed on the entire surface of a 3-inch wafer is etched. When the plasma emission spectrum is longer than 350 nm, the base line becomes slightly higher during etching, but no change is observed in the spectrum pattern. In the region of 350 nm or less, characteristic strong light emission is observed only when Ta is etched. FIG. 2 shows the result of dividing the two spectra to see the emission intensity ratio. 220 nm to 350
It was found that a change in light emission caused by etching was particularly large in the nm region. This is because tantalum (Ta) atoms and tantalum chloride molecules (TaCl, TaC) generated by decomposition of the Ta etching reaction product by plasma.
This indicates that the emission of l ₂ ) appears strongly at a wavelength of 220 nm to 350 nm. Therefore, it has been found that when the etching target is a material containing Ta, by monitoring the light emission during the etching only in this wavelength region, the start point and the end point of the etching can be determined. Also, 220n
In the region of m to 350 nm, since the emission of chlorine itself, which is an etching gas, is weak, the signal of the light receiving means is amplified to increase the sensitivity, so that even when the etching area is small,
It was found that the S / N (signal / noise) ratio was good and light emission from the reaction product could be observed. As described above, according to the method of the present invention for monitoring the light emission intensity in the region of 220 nm to 350 nm, the starting point and the ending point of the etching can be accurately determined. High pattern formation can be realized.

[0007]

Embodiments of the present invention will be described below in more detail with reference to the drawings. <Embodiment 1> FIG. 3 is a schematic view showing an example of the configuration of an ion flow etching apparatus used in the method of manufacturing an X-ray mask according to the present invention. Sample 11 was produced as follows.
2 μm thick on a 4 inch diameter, 2 mm thick Si wafer
Was deposited by a low pressure vapor phase epitaxy method, and a Ta film was deposited thereon by a sputtering method using electron cyclotron resonance plasma to a thickness of 0.4 μm. On top of that, a SiO ₂ film was deposited to a thickness of 0.15 μm by a vapor phase growth method using electron cyclotron resonance plasma. Subsequently, an electron beam resist was applied to a thickness of 0.2 on the SiO ₂ film on the surface.
Spin coating at a thickness of μm, and use an electron beam exposure method.
L (line) and S (space) patterns and isolated patterns of resist having a dimension of 08 μm to 2 μm were formed. Next, the substrate was placed in a reactive ion etching apparatus (not shown), and the SiO ₂ film was etched using a mixed gas of CF ₄ and SF _{6 with} the resist as a mask.
Thereafter, the resist was removed by an ozone ashing apparatus (not shown) to form a SiO ₂ film pattern. Next, using the ion-flow etching apparatus shown in FIG. 3 as the etching gas 4, chlorine (Cl ₂ )
Gas, gas pressure 0.15mTorr (milliTorr), 2.45GH
Etching was performed at a microwave (3) power of 500 W in z and a temperature of the sample 11 of 70 ° C. As for the emission of the plasma, the optical fiber 12 was disposed at a position on the upper surface of the sample 11 at which the plasma could be viewed from the side, and the emission was collected through the quartz window 13. At the end of the optical fiber 12, there is a spectroscope 14, which splits the emitted light and takes its intensity into a computer 15. In the present embodiment, emission at a wavelength of 267 nm was monitored. FIG. 4 shows the time dependence of the emission intensity. It was found that the emission signal intensity increased 70 seconds after the start of the discharge, and that the etching was started. When the etching is steadily progressing, the emission signal intensity shows almost constant intensity. After 7 minutes, the intensity of the light emission signal began to decrease, at which point the Ta etching was completed, indicating that the SiC surface under the Ta etching had been reached. From this, after over-etching for 3 minutes, the discharge was stopped via the control device. In the sample in the present embodiment, the area of the etching target Ta is
Although it was about 4% of the 4-inch wafer, the start and end of etching could be determined with high sensitivity even at about 0.2%. In the present embodiment, the spectroscope 14 has a wavelength resolution of 1.5 n.
m, and a specific wavelength of 267 nm in the range of 220 nm to 350 nm was selected and monitored. However, since the light emission related to Ta etching is widely distributed in the wavelength region, the resolution of the spectroscope was reduced. Also, when the etching area was 0.2%, the start and end could be determined. In addition, as can be seen from FIG.
Means that the resolution is 3
By monitoring only this region, the influence of the background can be reduced, and the etching area is 0.1%.
In the following, the start and end of the etching could be determined. Although the spectroscope 14 is used in the present embodiment, it has been confirmed that the start and end of the etching can be determined even when an optical filter that transmits only light of 220 nm to 350 nm is used instead of the spectroscope 14.

Second Embodiment A sample having an etching area of about 0.5% was manufactured in the same manner as in the first embodiment. This sample was used as an etching gas 4 with a Cl ₂ gas and a gas pressure of 0.15 mTorr using an ion flow etching apparatus shown in FIG.
(Militor) Microwave of 2.45 GHz (3) Etching was performed at a power of 500 W and a temperature of the sample 11 of 70 ° C. At the same time, light emitted during etching was collected through the quartz window 13. The spectroscope 14 uses the wavelength resolution of 1.5 nm to capture changes in emission intensity at 263 nm and 255 nm into a computer, and converts the 263 nm intensity into 25 in real time.
Divide by 5 nm intensity and monitor the intensity ratio. FIG. 5 shows the time dependence of the emission intensity ratio. Ta
Etching started 45 seconds after the start of discharge and was found to be completed in 7 minutes. Thereafter, overetching was performed for 3 minutes, and the discharge was stopped. The method described in this embodiment employs the ratio of the light emission intensities of two wavelengths, so that the fluctuation of the light emission intensity due to the fluctuation of the plasma is canceled, and only the change in the light emission related to the etching is detected with good S / N. did it. In particular, it was effective when the etching area was small and the absolute value of the emission intensity was small.

[0009]

According to the method of manufacturing an X-ray mask by plasma etching of the present invention, 220 nm
By monitoring the change in the emission intensity at a wavelength of ~ 350 nm, the start and end points of the etching of the Ta-containing material can be determined with high sensitivity even when the etching area is small, whereby the pattern formation of the X-ray mask absorber can be performed. There is an effect that can be realized with high reproducibility and high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of manufacturing an X-ray mask according to the present invention, in which chlorine is used as an etching gas and plasma emission is performed when etching is not performed and when Ta formed on the entire surface of a 3-inch wafer is etched. The figure which compared the spectrum.

FIG. 2 is a cross-sectional view illustrating a method of manufacturing an X-ray mask according to the present invention;
7 is a graph showing the relationship between the wavelength and the emission intensity ratio obtained by dividing the emission spectra of the two plasmas shown in FIG.

FIG. 3 is a schematic diagram showing an example of a configuration of an ion flow etching apparatus used for manufacturing the X-ray mask exemplified in the first embodiment of the present invention.

FIG. 4 shows the wavelength of 267.
The figure which shows the etching time dependence of the plasma light emission intensity of 2 nm.

FIG. 5 illustrates a wavelength 263n exemplified in the second embodiment of the present invention.
FIG. 9 is a diagram showing the etching time dependence of the plasma emission intensity ratio obtained by dividing m by a wavelength of 255 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plasma chamber 2 ... Magnet coil 3 ... Microwave 4 ... Etching gas 5 ... ECR plasma 6 ... Ion flow 7 ... Sample table 8 ... Etching chamber 9 ... Exhaust 10 ... Cooling water 11 ... Sample 12 ... Optical fiber 13 ... Quartz window 14 ... Spectroscope (or optical filter) 15 ... Computer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masatoshi Oda 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 2H095 BA10 BB10 BB17 BB18 BB31 BC01 4K057 DA14 DB08 DD04 DE01 DJ03 DM29 DM40 5F004 AA16 BA14 BB14 BD03 CB02 CB15 DA04 DB08 5F046 GD01 GD12 GD15 GD17

Claims (5)

[Claims] An X-ray etching apparatus using a plasma etching apparatus.
In the method for manufacturing a line mask, a step of arranging light receiving means for monitoring the emission intensity of plasma in the etching chamber of the etching apparatus, and detecting an emission intensity signal by dispersing emission of chemical species in the plasma; A step of determining the starting point and the ending point of the etching by performing an arithmetic operation of the setting on the emission intensity signal of the chemical species in the plasma; and a step of changing the etching conditions after a lapse of a predetermined time from the starting or ending point of the etching. Alternatively, X includes at least a step of stopping the etching.
Manufacturing method of line mask. 2. The method for manufacturing an X-ray mask according to claim 1, wherein an optical filter or a spectroscope is used as a means for dispersing the chemical species in the plasma. 3. An etching gas according to claim 1, wherein a gas containing at least chlorine is used as an etching gas and an X-ray absorber containing at least tantalum (Ta) is used as an etching target. The method of manufacturing an X-ray mask, wherein the determination uses light emission in a wavelength range of 220 nm to 350 nm in plasma or light emission in a specific wavelength range within the above wavelength range. 4. The method according to claim 3, wherein the wavelength 22
The emission intensity in the range of 0 nm to 350 nm is divided by the emission intensity of another wavelength in the vicinity of the above-mentioned wavelength to cancel the fluctuation of the plasma itself, to improve the S / N (signal / noise) ratio, A method for manufacturing an X-ray mask, comprising a step of detecting an end point with increased positional accuracy. 5. A plasma etching apparatus for performing the method of manufacturing an X-ray mask according to claim 1, wherein the plasma light is received in an etching chamber of the etching apparatus. A spectroscope or an optical filter for extracting light of a specific wavelength of the emission spectrum of a chemical species composed of an etching gas and a reaction product during etching; and measuring the emission intensity of the chemical species in the plasma in the etching chamber, A means for determining a starting point and an ending point of the etching when the value has reached a predetermined value; a means for changing the etching conditions a predetermined time after the starting or ending point of the etching; or a means for stopping the etching. X-ray mask manufacturing apparatus.