JP2003249431A - Ashing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ashing unit in which the progress of an ashing process can be monitored simply and accurately. <P>SOLUTION: A high-sensitivity carbon dioxide analyzer 8, such as an atmospheric pressure ionization mass spectrometer of a Fourier transformation type infrared spectrometer, is provided to communicate with an ashing unit processing chamber 7 for a resist film pattern thinning process. The amount of carbon dioxide gas produced from the ashing process is monitored with a high sensitivity, and this facilitates an accurate grasp of the progress of the pattern thinning process. As the result, the progress of pattern thinning by ashing is accurately grasped even when the amount of ashing is quite small (resulting in but a trace of carbon dioxide gas). <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 an improvement of an ashing device used in a pattern forming process in manufacturing a semiconductor device, and more particularly, to an improved ashing device capable of forming a fine pattern by a simple process. Ashing device configuration.

[0002]

2. Description of the Related Art Semiconductor device DRAMs (Dynamic Random
Access Memory) and system LSI circuits (Large-Scal)
In order to improve the performance of an e Integrated Circuit), a technique for forming an extremely fine pattern, which exceeds the limit of the lithographic technology that can be actually used at present, has been studied.
Such techniques include a thinning method for the resist pattern itself formed in the lithography step, a thinning method for the antireflection film used in the lithography step, and a thinning method for the dry etching step. Among these methods, the thinning method using the resist pattern itself has an advantage that it has almost no effect on the subsequent steps.

Therefore, a method has been studied in which a resist pattern formed in a lithography process is miniaturized (thinned) by removing a part of the resist pattern surface (including upper surface and side surface) by ashing treatment.
However, the determination of the processing conditions for that purpose requires a lot of factors, which is very time-consuming. In particular, as compared with the case where the resist film is entirely removed by ashing after pattern processing, the amount of ashing generated in the ashing process in the above-described thinning technique is small, and thus the amount of reaction gas generated is also very small. Therefore, it is extremely difficult to monitor the progress of the ashing process by measuring the reaction gas amount, and thus the monitoring method by measuring the reaction gas amount has not been considered at all.

[0004]

An object of the present invention is to accurately monitor the progress of the ashing process (thinning) when the resist film pattern is miniaturized (thinning) by the above ashing process. The object of the present invention is to provide an improved ashing device configuration so that the labor required for determining ashing processing conditions can be reduced.

[0005]

In order to achieve the above object, the present invention employs the following characteristic device configuration.

That is, according to the present invention, "an ozone ashing treatment apparatus used for removing a part of a resist film pattern surface by ashing treatment under atmospheric pressure, the progress of the ashing treatment is described. For monitoring purposes, there is provided an ashing device characterized in that a carbon dioxide gas amount measuring device for measuring the amount of carbon dioxide gas generated by the ashing process is additionally provided.

As described above, a highly sensitive carbon dioxide gas analyzer is provided as a device for measuring the amount of carbon dioxide gas generated, and the quantitative amount between the thinning amount of the resist film pattern by the ashing process and the amount of carbon dioxide gas generated is provided. If a calibration curve showing the relationship is created in advance, the ashing processing amount can be accurately monitored using this calibration curve, and the required ashing processing amount before ashing processing (required ashing processing time)
Can be determined easily and accurately.

In the above carbon dioxide gas measuring device, the lower limit of the detectable range of the carbon dioxide gas is 50 pp.
It is more desirable that it is m or less. By using such a high-sensitivity measuring device, it is possible to ensure monitoring accuracy with a high ashing processing amount.

A mass spectrometer can be used as the above carbon dioxide gas measuring device, and in particular, atmospheric pressure ionization capable of measuring the above generated carbon dioxide gas by taking in a sample gas under atmospheric pressure. More preferably, a type of mass spectrometer is used. Higher measurement accuracy is ensured by adopting this mass spectrometer (in particular, an atmospheric pressure ionization type mass spectrometer). In the atmospheric pressure ionization mass spectrometer, the sample gas (main component gas + impurity gas) is first ionized by corona discharge under atmospheric pressure, and then the impurity gas is ionized by ion-molecule reaction. It is more preferable to use a stepwise ionization method. As a result, CO2 ions having a mass number of 44 can be selectively monitored with high accuracy.

As the carbon dioxide gas measuring device, a spectroscopic analyzer can be used, and in this case, it is more preferable to use a Fourier transform type infrared spectroscopic analyzer. By adopting such a spectroscopic analysis device (in particular, a Fourier transform type infrared spectroscopic analysis device), higher measurement accuracy is ensured. That is, in the ashing process using ozone as the processing gas, the amount of light emission due to the light emitting action of the generated carbon dioxide gas cannot be measured,
The amount of carbon dioxide gas generated can be measured by utilizing the infrared absorption function (wavelength of about 4.3 μm) of carbon dioxide gas. In particular, by using a Fourier transform type infrared spectroscopic analyzer, higher measurement accuracy can be secured. In order to increase the measurement sensitivity of the Fourier transform infrared spectroscopic analyzer, it is desirable to take a long path (passage path) through which infrared rays to be detected pass.

The objects and configurations of the present invention other than the above, and the functions and effects obtained thereby will be clarified in order in the detailed description of the following embodiments.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings, with reference to Examples.

<Embodiment> FIG. 1 shows a schematic structure of an ashing apparatus according to an embodiment of the present invention. In the ashing apparatus according to the present embodiment, the ozone gas (ashing processing gas) 2 generated by the ozone generator 1 is introduced into the processing chamber 7 and discharged from the nozzle 3 toward the surface of the substrate 4 to be processed. The supply and release of these gases are performed at about atmospheric pressure using only the pressure difference (20-50 mm in water pressure) from the exhaust pressure from the exhaust port 6.

The substrate 4 to be processed is placed on the stage 5,
It is heated by the heating mechanism (not shown) of the stage 5.
Ozone is thermally decomposed on the heated substrate 4 to generate oxygen radicals. The generated oxygen radicals react with the resist film on the surface of the substrate 4 to generate carbon dioxide (CO2) and water (H2 O) as reaction products, and the resist film is gradually removed by ashing from the surface. At this time, if a pattern is formed on the resist film, the resist material is removed by ashing not only from the surface of the resist film pattern but also from the side surface thereof, and the resist film pattern is miniaturized (thinned). Typical processing conditions (for example, supply oxygen flow rate 10 L / min, ozone concentration 5%, and processing temperature 110)
At 500 ° C., a resist film pattern having a thickness of 500 nm (initial line width 120 nm) can be thinned to a line width of 80 nm by ashing treatment for about 3 minutes. The amount of carbon dioxide (CO2) gas generated at this time is about 0.2 CC, and it can be estimated that the content in the supplied oxygen gas is about 1 to 2 ppm.

In this embodiment, the generated carbon dioxide gas (CO2 gas = carbon dioxide gas) amount is used as the gas sampling port 9
It was monitored by a carbon dioxide analyzer 8 installed in communication with the inside of the processing chamber 7 via the. The carbon dioxide analyzer 8 is provided with an exhaust port 10. By exhausting gas through the exhaust port 10, the atmospheric gas in the processing chamber 7 is sucked and collected in the carbon dioxide analyzer 8.

In this embodiment, the carbon dioxide analyzer 8 described above is used.
As a mass spectrometer such as an atmospheric pressure ionization mass spectrometer,
Alternatively, the amount of carbon dioxide gas generated was monitored using a spectroscopic analyzer such as a Fourier transform infrared spectroscopic analyzer. A calibration curve between the monitoring value of the amount of carbon dioxide gas (total amount generated: 0.2 CC in the above example) and the thinning amount of the resist pattern (total removal amount: 40 nm in the above example) was prepared in advance by an experiment, Using this pre-made calibration curve, the ashing processing time for obtaining the desired thinning amount was calculated and determined.

Here, the ashing process step for thinning the resist film pattern will be briefly described with reference to FIG. In FIG. 2, a film to be processed 12 such as a silicon oxide film (SiO2 film) which is a target of lithography processing using a resist film pattern on a Si substrate 11.
Are formed. A resist film pattern 15 is formed on the film to be processed 12 via a reflection preventing film 13 by lithography. In FIG. 2, the resist film pattern 15 is shown as a pattern shape before the thinning process by ashing. The resist film pattern 15 before thinning processing is subjected to thinning processing by ashing to obtain the resist film pattern 14 after thinning processing. That is, by ashing, not only the upper surface of the resist film pattern 15 but also the side surfaces thereof are removed by ashing, and the pattern is thinned. The difference a + b between the pattern width c before the thinning process and the pattern width d after the thinning process is the thinning amount.

As the thinning process by ashing proceeds, carbon dioxide gas (= carbon dioxide) is produced as a reaction product of the reaction between the oxygen radicals produced from the process gas (ozone) and the resist film material containing carbon atoms. (CO2) gas is generated. The generated carbon dioxide gas amount depends on the thinning amount a + b. Therefore, the quantitative relationship between the generated carbon dioxide gas amount and the thinning amount a + b is obtained in advance as a calibration curve, whereby the generated carbon dioxide gas amount is measured (monitored), and the above-mentioned calibration curve is used to measure the above. It is possible to accurately know the thinning amount a + b of.

[0019]

According to the present invention, the ashing process (thinning process) of the resist film pattern, which is conventionally controlled only by the processing time, is managed in real time by measuring the generation amount of carbon dioxide gas (carbon dioxide gas). There are advantages. In addition, there is an advantage that the progress of the pattern thinning processing can be analyzed. Further, it is also effective for analysis and examination of the problem of heat shrinkage of the resist film pattern when the thinning process is performed at a temperature equal to or higher than the thermal history when forming the resist film pattern by lithography.

The shape and size of the resist film pattern,
When the resist film materials, etc. are greatly different, it is not possible to use a single calibration curve in common in all of them, but in such a case, those can be used in advance depending on the change in the resist film pattern configuration. It is possible to prepare a calibration curve that can correspond to the above, and to perform monitoring using the calibration curve that can respond best. Although it depends on the shape and size of the resist film pattern and the resist film removal rate by the ashing removal process (thinning process), in order to perform highly accurate monitoring, the lower limit of detection of the amount of generated carbon dioxide gas is approximately 50 ppm or less. Is desirable.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a schematic configuration of an ashing device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a surface portion of a substrate to be processed for explaining a resist film pattern thinning process step by ashing.

[Explanation of symbols]

1 ... Ozone generator, 2 ... Process gas (ozone gas), 3 ... Nozzle, 4 ...
Substrate to be processed, 5 ... Stage, 6 ...
Exhaust port, 7 ... Processing chamber, 8 ... Carbon dioxide analyzer, 9 ... Gas sampling port, 10
… Exhaust port, 11… Si substrate, 12…
Processed film, 13 ... Antireflection film, 14 ...
Resist film after thinning treatment, 15 ... Resist film before thinning treatment, a + b ... Thinning amount, c ... Pattern width before thinning treatment, d ... Pattern width after thinning treatment.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G059 AA01 AA05 BB16 CC04 DD15                       EE10 HH01 MM01 MM12                 2H096 AA25 LA06 LA16                 5F004 AA01 BA19 BB18 BC07 BC08                       BD01 CB04 DA27 DB26                 5F046 AA17 MA12

Claims (6)

[Claims] 1. An ozone ashing device used to remove a part of a resist film pattern surface by ashing treatment under atmospheric pressure, wherein the ashing treatment is performed to monitor the progress of the ashing treatment. An ashing device characterized by being provided with a carbon dioxide gas amount measuring device for measuring the amount of carbon dioxide gas generated by. 2. The ashing device according to claim 1, wherein the carbon dioxide gas amount measuring device has a lower limit value of a detectable range of the carbon dioxide gas amount of 50 ppm or less. 3. The ashing device according to claim 1, wherein the carbon dioxide gas measuring device is a mass spectrometer. 4. The ashing device according to claim 3, wherein the mass spectrometer is an atmospheric pressure ionization mass spectrometer. 5. The ashing device according to claim 1 or 2, wherein the carbon dioxide gas amount measuring device is a spectroscopic analyzer. 6. The ashing device according to claim 5, wherein the spectroscopic analysis device is a Fourier transform infrared spectroscopic analysis device.