JPH1041283A - Method and apparatus for detecting etching end point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably detect the etching end point. SOLUTION: In the case of dry etching of a tungsten silicide/polycrystalline Si structure or polycrystal Si/silicon oxide structure, the emission at 337nm in wavelength is monitored to detect the etching point of a tungsten silicide film 25 or polycrystal Si film 24 from a great change of the emission light intensity. The emission at 405nm wavelength may be monitored at the same time to detect the etching end point by using both the emissions at 405nm and 337nm in wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an end point of etching and an apparatus for detecting an end point of etching, and is particularly suitable for application to etching of high melting point metal silicide, polycrystalline silicon, or the like.

[0002]

2. Description of the Related Art With the increase in the density of semiconductor integrated circuits, wiring has been increasingly miniaturized, and the proportion of wiring processing technology in the manufacturing process of semiconductor integrated circuits has been increasing.

In order to achieve the miniaturization of the wiring, various devices have been tried in a semiconductor manufacturing apparatus.
Of these, the detection of the end point of the etching in the dry etching apparatus is particularly important in controlling the processing of the tungsten silicide / polycrystalline silicon structure for forming the gate electrode and controlling the thickness of the underlying gate oxide film.

Conventionally, the end point of dry etching for processing a gate electrode having a tungsten silicide / polycrystalline silicon structure has been detected as follows. That is, a halogen-based etching gas is usually used during dry etching for processing the above-described gate electrode. During this etching, WCl _x and WB are mainly contained in the reaction chamber as reaction products of the wiring material and the etching gas.
Compounds such as r _x , SiCl _x , and SiBr _x are generated. Then, out of the light emission due to the excitation of these compounds in the plasma, the light emission of 405 nm wavelength (SiC
luminescence due to the Si—Cl bond of l _x )
The light emission intensity was converted to a voltage value, and the change was used to detect the end point of the etching.

[0005]

However, in the above-mentioned conventional method for detecting the end point of etching, the reaction conditions at the time of etching, specifically, the etching area, the atmosphere in the reaction chamber (depending on the atmosphere of the etching performed immediately before). ), The amount of SiCl _X generated varies, and therefore, there is a drawback that the end point cannot be detected stably because it is easily affected by the reaction conditions at the time of etching.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an etching end point detecting method and an etching end point detecting device capable of stably detecting an etching end point to solve the above-mentioned problems.

[0007]

In order to solve the above-mentioned problems, the present inventor has proposed a method of dry-etching a tungsten silicide / polycrystalline silicon structure or a polycrystalline silicon / silicon oxide structure using a halogen-based etching gas. The changes in the emission intensities of various wavelengths observed in the above were examined in detail. As a result, although not completely identified at this time, the emission of a wavelength of approximately 337 nm observed when etching a tungsten silicide film, a polycrystalline silicon film, a silicon oxide film, or the like is reduced to other wavelengths such as 405 nm. It has been found that there is an extremely large difference in light emission intensity between the films compared to light emission, and that when the layered structure of these films is etched, the light emission intensity changes greatly when the interface between these films is exposed. Then, in order to stably detect the end point of the etching, it was concluded that monitoring of the light emission having a wavelength of about 337 nm was the most effective, and the present invention was devised.

That is, in order to achieve the above object, a first aspect of the present invention is an etching end point detecting method for detecting an etching end point by monitoring light emission during etching. The present invention is characterized in that the end point of the etching is detected by monitoring the light emission of the wavelength.

According to a second aspect of the present invention, there is provided an etching end point detecting apparatus for detecting an etching end point by monitoring light emission during etching, by monitoring light emission having a wavelength of about 337 nm. An end point is detected.

In the present invention, the material to be etched is:
Silicon or a silicon compound. Here, silicon may be any of polycrystal, single crystal, or amorphous. The silicon compound may be silicon germanium (SiGe), silicon nitride (SiN), or the like, in addition to a high melting point metal silicide such as tungsten silicide.

In the present invention, from the viewpoint of more accurately detecting the end point of the etching, it is preferable that the
In addition to the emission at the wavelength of m, the emission at the wavelength of about 405 nm is also monitored, and the end point of the etching is detected using the emission at the wavelength of about 337 nm and the emission at the wavelength of about 405 nm.

In the present invention configured as described above, the end point of the etching is detected by monitoring the light emission having a wavelength of about 337 nm.
When etching progresses and the interface between different films is exposed, the light emission intensity changes significantly. The large change in the light emission intensity is hardly influenced by the reaction conditions at the time of etching. Therefore, the end point of the etching can be detected more stably as compared with the related art by setting the end point of the etching when the light emission intensity largely changes.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

First, a dry etching apparatus used in this embodiment will be described. FIG. 1 shows this dry etching apparatus.

As shown in FIG. 1, in this dry etching apparatus, a lower electrode 3 on which a semiconductor substrate 2 to be processed is mounted and an upper electrode 4 parallel to the lower electrode 3 are provided in a reaction chamber 1. Have been. A high-frequency power source 6 is connected to the upper electrode 4 via a capacitor 5, and the lower electrode 3
Is connected to a high frequency power supply 8 via a capacitor 7. The inside of the reaction chamber 1 is evacuated by a vacuum evacuation system (not shown). Further, an etching gas is introduced into the reaction chamber 1 through a gas line 9. Reference numerals 10, 11, and 12 indicate mass flow controllers (MFCs) for controlling flow rates.

In this dry etching apparatus, an etching end point detecting device 13 is attached to the reaction chamber 1. This etching end point detecting device 13 has a wavelength of 337 nm.
And a photodetector (not shown) capable of monitoring both emission at 405 nm and at 405 nm.

Next, an etching method according to this embodiment will be described. Here, as an example, MOSL
An etching method for forming a gate electrode of a MOSFET in the manufacture of an SI will be described.

That is, in this embodiment, first, as shown in FIG. 2A, the surface of the silicon substrate 21 is selectively oxidized to form the field silicon oxide film 2.
After the formation of 2 and isolation between the elements, a gate silicon oxide film 23 is formed by oxidizing the surface of the active region surrounded by the field silicon oxide film 22. Next, for example, chemical vapor deposition (Chemical Vapor Deposition,
After a polycrystalline silicon film 24 is formed on the entire surface by a CVD method, impurities are doped into the polycrystalline silicon film 24 by an ion implantation method or a thermal diffusion method to reduce the resistance. Next, for example, a tungsten silicide film 25 is formed on the polycrystalline silicon film 24 by a sputtering method or the like. Thereafter, a resist pattern 26 for forming a gate electrode is formed on the tungsten silicide film 25 by lithography.

Next, after the silicon substrate 21 is placed on the lower electrode 3 in the reaction chamber 1 of the dry etching apparatus shown in FIG.
₂ ) is supplied at a flow rate of, for example, 60 sccm. At the same time, the inside of the reaction chamber 1 is, for example, 3 mTorr.
The pressure is maintained at r. Then, the upper electrode 4 and the lower electrode 3
A high-frequency power of, for example, 10 W is applied between them to generate discharge, thereby exciting the etching gas to generate plasma, and etching the tungsten silicide film 25. Thereby, as shown in FIG. 2B, the tungsten silicide film 25 is etched into the same shape as the resist pattern 26.

At this time, the tungsten silicide film 25
The end point of the etching is detected by monitoring the emission at the wavelengths of 337 nm and 405 nm simultaneously with the start of the etching, and detecting a change in the emission intensity.

That is, FIG. 3 shows a change in the intensity of light emission at wavelengths of 337 nm and 405 nm as the etching proceeds. The horizontal axis in FIG. 3 represents the etching time in seconds, and the vertical axis represents the voltage value representing the light emission intensity. Also, in FIG. 3, for reference, 400 nm, 410 nm, 43
The measurement results of the emission intensity at wavelengths of 0 nm and 450 nm are also shown. FIG. 4 is a graph in which the baseline of the emission intensity graph of each wavelength in FIG. 3 is made constant (normalized) to make it easier to see the change in emission intensity.

As shown in FIGS. 3 and 4, 337 nm
The light emission intensity at the wavelength of starts to increase rapidly near the etching time after about 60 seconds, and reaches a peak at about 90 seconds. This is because the tungsten silicide film 25
Is etched to expose the underlying polycrystalline silicon film 24. As can be seen from FIGS. 3 and 4, the change in the emission intensity at a wavelength of 337 nm in the vicinity of 90 seconds is significantly larger than the emission intensity at any other wavelength. Therefore, by monitoring the light emission intensity at the wavelength of 337 nm and setting the end point of the etching when the light emission intensity changes greatly, the end point of the etching of the tungsten silicide film 24 can be detected stably and accurately.

Strictly speaking, there is a certain degree of freedom as to which point of the above-mentioned change curve of the light emission intensity at the wavelength of 337 nm is used as the end point of the etching, but this generally depends on the process used. Can be determined arbitrarily.

On the other hand, the emission intensity at a wavelength of 405 nm, which is conventionally used for detecting the end point of etching, starts to decrease from the vicinity where the etching time exceeds about 60 seconds. 33
The change in the emission intensity at the wavelength of 7 nm is an ascending waveform, whereas the change in the emission intensity at the wavelength of 405 nm is a falling waveform. By comparing the changes in the emission intensity at these two wavelengths, The end point of the etching of the tungsten silicide film 25 can be detected more accurately.

After the tungsten silicide film 25 is etched as described above, the polycrystalline silicon film 24 is subsequently etched. At this time, the processed shape of the polycrystalline silicon film 24 by etching is improved. For this purpose, the etching gas is changed from Cl ₂ to, for example, Cl _2.
+ HBr. Then, using this etching gas, the polycrystalline silicon film 24 is etched as shown in FIG. 2C.

The end point of the etching of the polycrystalline silicon film 24 is detected by using the change of the light emission intensity at the wavelength of 337 nm, or similarly to the detection of the end point of the etching of the tungsten silicide film 25. The change of the light emission intensity is performed in combination.

As described above, according to this embodiment,
Tungsten silicide film 25, polycrystalline silicon film 2
4. There is a large difference in light emission intensity between the gate silicon oxide films 23. When the interface between these films is exposed, light emission at a wavelength of 337 nm where the light emission intensity changes greatly is monitored. Since the end point of the etching of the tungsten silicide film 25 and the polycrystalline silicon film 24 is detected at the time of the completion of the etching, the end point of the etching can be detected more stably and accurately than the conventional method of detecting the end point of the etching using the light emission of 405 nm wavelength. Can be done. Further, in addition to the emission at the wavelength of 337 nm,
By monitoring the emission at a wavelength of 405 nm and comparing them to detect the end point of the etching, the end point of the etching can be detected more accurately.

As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. .

For example, the numerical values, etching gas, and the like listed in the above-described embodiment are merely examples, and different numerical values, etching gas, and the like may be used as needed. Specifically, the etching gas for the tungsten silicide film 25 is C ₂ instead of Cl _2.
l ₂ + HBr, Cl ₂ + HBr + O ₂ or the like may be used. The etching gas for the polycrystalline silicon film 24 may be Cl ₂ + HBr + O ₂ or a gas to which a fluorine-based gas (CF ₄ , SF _6, etc.) is added.

In the above-described embodiment, FIG.
However, this dry etching apparatus is merely an example, and another dry etching apparatus using a different reaction chamber configuration, gas supply method, number and type of high-frequency power supply, and vacuum evacuation method is used. You may.

Furthermore, in the above-described embodiment, the case where the present invention is applied to etching for forming a gate electrode of a MOSFET has been described. It can be applied to etching for forming a pattern composed of.

[0032]

As described above, according to the present invention, the end point of the etching is detected by monitoring the light emission having a wavelength of about 337 nm, so that the end point of the etching can be detected stably. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a dry etching apparatus used in an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining an etching method according to an embodiment of the present invention.

FIG. 3 is a graph showing a change in emission intensity with an etching time for explaining detection of an etching end point in an etching method according to an embodiment of the present invention.

FIG. 4 is a graph in which the baseline in the graph shown in FIG. 3 is fixed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction chamber, 13 ... Etching end point detection apparatus
21: silicon substrate, 24: polycrystalline silicon film, 25: tungsten silicide film, 26:
Resist pattern

Claims (5)

[Claims] 1. An etching end point detecting method for detecting an etching end point by monitoring light emission during etching, wherein the etching end point is detected by monitoring light emission having a wavelength of about 337 nm. A method of detecting an end point of etching. 2. The method according to claim 1, wherein the material to be etched is silicon or a silicon compound. 3. The light emission of a wavelength of about 405 nm is also monitored, and the light emission of a wavelength of about 337 nm and the light emission of the
2. The method for detecting an end point of etching according to claim 1, wherein the end point of the etching is detected in combination with emission at a wavelength of nm. 4. An etching end point detecting device for detecting an etching end point by monitoring light emission during etching, wherein the etching end point is detected by monitoring light emission having a wavelength of about 337 nm. An end point detecting device for etching. 5. The light emission of a wavelength of approximately 405 nm is also monitored, and the light emission of a wavelength of approximately 337 nm and the light emission of a wavelength of approximately
5. The etching end point detecting device according to claim 4, wherein the etching end point is detected in combination with emission at a wavelength of nm.