JPH1064884A - Etching device and etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the damage of a base caused by overetching by detecting the strength of the interference light between the light reflected at the surface of a treatment film out of the lights generated by plasma and the light reflected at the interface between the treatment film and the base, and detecting the etching rate, based on the ripple cycle of the detected strength. SOLUTION: A part of the light generated by plasma 7 is reflected at the surface of an SiO2 film 12, and a part of the other permeates an SiO2 film 12, and is reflected at the interface between the SiO2 film 12 and the base 11. Then, the light reflected at the surface of the SiO2 film 12 and the light reflected at the interface between the SiO2 film 12 and the base are made to interfere with each other, and this interference light is passed through a tube 5, and only the light of wavelength of about 483nm is passed through a filter 6, and it is detected with a light detector 3. The cyclic ripple of this detected light is outputted to a controller 8, and this controller 8 detects the etching rate, based on the ripple cycle. Hereby, the damage of the base by overetching can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a semiconductor device.
The present invention relates to an etching apparatus and an etching method for detecting an etching rate or an etching end point in a plasma etching process used for manufacturing a CD (liquid crystal display) or the like.

[0002]

2. Description of the Related Art A plasma etching apparatus is used for manufacturing a semiconductor device, a liquid crystal display (LCD), and the like. Usually, in a process using a plasma etching apparatus, an etching end point is detected using a plasma emission analysis type etching end point detecting apparatus in order to prevent under-etching and over-etching.

In a plasma emission analysis type etching end point detection apparatus, a detection window made of transparent glass is provided in a part of a chamber of the etching apparatus, and a specific wavelength of plasma emission emitted from the detection window to the outside of the chamber is provided. Is detected by a photodetector, and the etching end point is detected by utilizing the fact that the intensity of the light of the specific wavelength suddenly changes due to the exposure of the base.

FIG. 5 shows the etching time on the horizontal axis.
The vertical axis shows the signal voltage value output from the photodetector.
And SiO on the silicon substrate_TwoWhen etching the film
FIG. 5 is a diagram showing a change over time of the output of the photodetector. example
For example, as shown in FIG. _TwoEtch the film
The signal voltage output from the photodetector is constant during
But SiO_TwoWhen the film etching is completed,
The pressure drops. Therefore, the signal voltage decreases and the threshold
The point at which Vth is crossed is detected as the etching end point.
Can be. In this case, the etching rate changes
Also, as shown in FIGS. 6 and 7, the intensity of light of a specific wavelength changes.
This specific wavelength
The end point of etching can be detected by the change in light intensity
Can be.

In Japanese Patent Application Laid-Open No. H4-297028, a light source such as a laser is provided outside a chamber of an etching apparatus, and a parallel beam is incident from the light source into the chamber.
There is disclosed an etching rate monitor that detects interference light between light reflected on the surface of a resist on a semiconductor wafer and light reflected on an SiO ₂ film being etched to detect an etching rate.

[0006]

However, the conventional plasma emission analysis type end point detecting apparatus has the following drawbacks. That is, the etching rate fluctuates due to fluctuations in the gas pressure in the chamber of the etching apparatus, fluctuations in the high-frequency power applied to the plasma, and the like,
The emission intensity of the plasma fluctuates. Therefore, the signal voltage value output from the photodetector may fluctuate even while the processing film is being etched. For example, as shown in FIG. 8, when the signal voltage value changes due to a change in gas pressure, high-frequency power, or the like, it may be erroneously detected that the base is exposed at a point indicated by an arrow A in the figure. is there. Especially,
If the signal voltage value is low due to particles generated by etching adhering to the detection window or the detection window being etched, erroneous detection is more likely to occur. For this reason, the conventional plasma emission analysis type etching end point detection apparatus does not have satisfactory reliability of the detection result.

Further, in the conventional plasma emission analysis type end point detection apparatus, the output of the photodetector does not change unless the base is exposed by etching, so that the base may be etched or damaged. Furthermore, the conventional plasma emission analysis type end point detection device only detects a decrease in the intensity of light of a specific wavelength due to exposure of the base, and cannot detect the etching rate during etching.

On the other hand, the etching rate monitor disclosed in Japanese Patent Application Laid-Open No. H4-297028 requires a light source, such as a laser, for outputting a parallel beam outside the chamber. It is necessary to provide the light receiving unit in such a way as to avoid the problem, and the structure of the device is complicated. Further, it is necessary to adjust the optical axis of the light source and the optical axis of the light receiving unit. Further, it is extremely difficult to detect the etching rates of different portions on the wafer, such as the central portion and the peripheral portion of the wafer, due to the structure of the apparatus.

An object of the present invention is to provide an etching apparatus and an etching method which have a simple structure and can detect an etching rate or an etching end point with high accuracy.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an etching apparatus for detecting an etching rate or an etching end point when a processing film on a base is etched by plasma etching. A light reflected on the surface of the light detection unit for detecting the intensity of interference light between the light reflected on the interface between the processing film and the base, and a periodic change in the output of the light detection unit. A control unit for detecting an etching rate or an etching end point based on the fluctuation cycle.

Another object of the present invention is to provide an etching method for detecting an etching rate or an etching end point when a processing film on a base is etched by plasma etching. Detecting the intensity of the interference light between the light reflected by the light source and the light reflected at the interface between the base and the processing film, and detecting the etching rate or the etching end point based on the period of the fluctuation of the intensity of the interference light. The problem is solved by an etching method characterized in that

Further, the above object is an etching method for detecting an etching end point when etching a processing film on an underlayer by plasma etching, wherein light generated by plasma is reflected on the surface of the processing film. And the intensity of the interference light between the reflected light and the light reflected at the interface between the base and the processing film, and the etching rate is determined based on the period of the change in the intensity of the interference light, and the initial value of the processing film is determined. The problem is solved by an etching method characterized in that the remaining etching time is obtained from the film thickness and the etching rate.

The operation of the present invention will be described below. In the present invention, of the light generated by the plasma, the light detecting unit detects interference light between light reflected on the surface of the processing film and light reflected on the interface between the processing film and the base. The intensity of the interference light is related to the thickness of the processing film, and the intensity of the interference light periodically fluctuates as the thickness of the processing film decreases by etching. Therefore, the etching rate can be known by measuring the period of the intensity of the interference light. Further, in the present invention, since the etching rate can be known as described above, if the film thickness of the processing film is known in advance, the time until the etching end point can be known.
Thereby, it is possible to avoid damaging the base by over-etching. In addition, even if the output of the photodetector temporarily fluctuates due to fluctuations in gas pressure, fluctuations in high-frequency power, and other noises before etching is completed, it should be distinguished from fluctuations due to a decrease in film thickness. Therefore, erroneous detection of the etching end point can be reliably avoided.

Further, in the present invention, since light emission by plasma is used, there is no need to provide a light source outside the chamber of the plasma etching apparatus, and the structure of the apparatus is relatively simple.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a plasma etching apparatus according to an embodiment of the present invention. Electrodes 9 and 1 are provided in chamber 1 of the plasma etching apparatus.
0 are arranged facing each other in the vertical direction. The electrode 9 is supplied with high-frequency power from a high-frequency power supply 14, and the processing substrate 2 such as a wafer or an LCD substrate is mounted on the electrode 9. On the other hand, the electrode 10 is a disk-shaped member, and has a hole 10a at the center. This electrode 1
0 is connected to ground.

The chamber 1 is connected to a gas supply device (not shown) for supplying a predetermined gas into the chamber 1 and an exhaust pump (not shown) for exhausting the inside of the chamber. A detection window 4 made of transparent glass is provided at the center of the upper wall of the chamber 1. An etching rate or etching end point detection unit is attached to the upper part of the chamber 1. The etching rate or etching end point detection unit includes a cylindrical portion 5 erected at a position matching the detection window 4 of the chamber 1, a photodetector 3 mounted on the upper portion of the cylindrical portion 5, and a photodetector 3 And a control unit 8 for detecting an etching rate based on the output of the controller and detecting an etching end point. The length of the cylindrical portion 5 is set to be sufficiently larger than the diameter. For example, the length of the cylindrical portion 5 is set to about 10 times the inner diameter. Further, a black paint is applied to the inner wall surface of the cylindrical portion 5 in order to reduce light reflection. Further, an optical filter 6 for selectively transmitting light having a wavelength of 483 nm is provided at an upper portion inside the cylindrical portion 5.

As the photodetector 3, a photodiode or a photomultiplier tube is used according to the wavelength and intensity of the light to be detected. In the plasma etching apparatus provided with the etching rate or etching end point detecting unit configured as described above, the processing substrate 2 is mounted in the chamber 1,
After the inside of the chamber 1 is evacuated by the exhaust pump, a gas such as C ₂ F ₆ is supplied into the chamber from the gas supply unit to maintain the pressure in the chamber at about 1 Torr. Then, high frequency power is supplied to the electrode 9 from the high frequency power supply 14. As a result, plasma 7 is generated between the electrodes 9 and 10, and the processing substrate 2
The upper SiO ₂ film is etched. At this time, light having a wavelength of about 350 to 1100 nm is generated by the plasma 7.

FIG. 2 is a schematic diagram showing the processing substrate 2.
Some of the light generated by the plasma 7 is reflected by the surface of the SiO ₂ film 12, the other part is reflected at the interface between the SiO ₂ film 12 and the underlying 11 passes through the SiO ₂ film 12. Then, the light reflected on the surface of the SiO ₂ film 12 and the SiO ₂
The light reflected at the interface between the film 12 and the base 11 interferes,
This interference light passes through the cylindrical portion 5, and only light having a wavelength of about 483 nm passes through the filter 6 and is detected by the photodetector 3. In this case, since the ratio between the inner diameter and the length of the cylindrical portion 5 is set to be sufficiently large, as shown in FIG.
Only the light that is reflected perpendicularly to the surface of the processing substrate 2 at the central portion reaches the photodetector 3, and the light that is obliquely incident on the cylindrical portion 5 is absorbed inside the cylindrical portion 5.

As the SiO ₂ film 12 on the processing substrate 2 is etched and its thickness decreases, the intensity of the interference light periodically changes. The cycle of the intensity of the interference light is related to the wavelength of the light and the etching rate. That is, in FIG. 2, the refractive index of the wavelength of incident light lambda _0, SiO ₂ film 12 n, the thickness of the SiO ₂ film 12 d, the wavelength of light in the SiO ₂ film 12 λ ₁ (= λ ₀ / N), the SiO ₂ film 12
The condition under which the light reflected on the surface of FIG. ₂ and the light reflected on the interface between the SiO ₂ film 12 and the base 11 interfere with each other and the light intensity becomes the strongest is expressed by the following equation (1). You. 2d = mλ ₁ (1) where m is an arbitrary integer.

By substituting λ ₁ = λ ₀ / n into this equation (1), the thickness d of the SiO ₂ film 12 at the time when the intensity of the interference light becomes maximum is obtained as shown in the following equation (2). become. d = mλ ₀ / 2n (2) On the contrary, the light reflected on the surface of the SiO ₂ film 12 and the SiO _2
The condition under which the intensity of the interference light with the light reflected at the interface between the _second film 12 and the underlayer 11 becomes the weakest is expressed by the following equation (3). The _{2d = mλ 1 + (λ 1} /2) ... (3) the thickness d of the SiO ₂ film when the intensity of the equation (3) to by substituting λ ₁ = λ ₀ / n interference light becomes weakest When asked,
Equation (4) below is obtained. d = (mλ ₀ / 2n) + λ ₀ / 4n (4) In FIG. 3, the horizontal axis represents the etching time, the vertical axis represents the signal voltage value, and the change of the signal output from the detector 3 with respect to time. FIG. As shown in FIG. 3, the signal voltage value output from the detector 3 periodically fluctuates as the film thickness of the processing film decreases, and the signal voltage value becomes constant when the base is exposed. The etching rate can be known from the period T1 of the signal voltage value, the wavelength of light, and the refractive index of the processing film. Further, assuming that the initial film thickness of the processing film is constant, the number of signal peaks generated until the end of etching is constant regardless of the etching rate, so before detecting the predetermined number of peaks. Even if the output of the detector temporarily changes due to a change in gas pressure, a change in high-frequency power, or other noise, it can be distinguished from a change in output due to a decrease in film thickness. Thereby, erroneous detection of the etching end point can be reliably prevented.

For example, even if the processing conditions are the same,
If a large amount of particles adhere to the chamber,
Since the etching rate decreases, the etching rate decreases.
Can be used as a guide for the maintenance of the etching equipment.
You. FIG._TwoActually remove the membrane
Ching, SiO_TwoThe light reflected on the surface of the film
SiO_TwoThe intensity of the interference light with the light reflected at the interface with the film is detected.
FIG. 9 is a waveform chart showing the result of measurement over time by the output device 3;
You. However, the filter used for the measurement is wavelength λ.₀Is 48
It selectively transmits 3 nm light. This place
In this case, the period T of the intensity of the interference light was 20 seconds. At this time
The etching rate is approximately as shown in the following equation (5).
It becomes 499.6 nm / min. Where λ ₀Is a wave of light
Long, n is SiO_TwoThe refractive index of the film.

R _E = (λ ₀ /2n)×(60/T)={483/(2×1.45)}/(60/20)=499.6 (5) Since the number of peaks is 5 and the cycle of the light emission intensity is 20 seconds, the control unit monitors the number and cycle of the peaks, and even if the etching end point is detected before the number of peaks is 5 or more, noise or the like may be detected. It is determined that the etching is not the end point of the etching, and the etching may be continued. After the number of peaks has passed five times, when the signal voltage value becomes constant, the etching end point is set.
Alternatively, a point at which a certain period of time has passed after the peak of the signal voltage value has passed five times may be set as the etching end point. Further, the time until the underlayer is exposed from the etching rate and SiO ₂ may be calculated, and the time when the time has elapsed may be set as the etching end point.

Further, in this embodiment, since the etching rate can be detected, if the thickness of the processing film is known, the time required for etching can be known. Can always be left at a constant thickness. Further, even when the refractive index of the processing film is unknown, if the thickness of the processing film is known, the etching end point can be detected as follows. That is,
First, a sample substrate having a processing film formed of the same material as the processing film to be etched is prepared. Then, after measuring the thickness of the processed film of the sample substrate, the processed film of the sample substrate is subjected to an etching process, and the output of the photodetector at that time is examined. Then, the relationship between the thickness of the processing film and the output cycle of the photodetector is determined in advance. Thus, if the actual thickness of the processing film is known, the number of periodic fluctuations of the output of the photodetector until the underlayer is exposed can be determined, so that the etching end point can be detected.

[0024] Incidentally, in the above embodiment has described the case of applying the present invention to the etching of the SiO ₂ film on the silicon substrate, thereby etching the invention in the etching of the SiO ₂ film on the silicon substrate The present invention is not limited to the detection of the rate or the end point of the etching.
ospho-Silicate Glass film and BPSG (Boron-doped)
It can also be applied to etching of (silicate glass) film.

Further, in the above-described embodiment, a case has been described where the etching rate or etching end point detecting section is provided only above the central portion of the silicon substrate, but, for example, above the peripheral portion of the silicon substrate. Also provided an etching rate or etching end point detection unit, by these etching rate or etching end point detection unit,
It is also possible to detect a difference in etching rate between the central part and the peripheral part of the substrate.

[0026]

As described above, according to the method of the present invention, of the light generated by the plasma, the interference light between the light reflected on the surface of the processing film and the light reflected on the interface between the processing film and the base. Since the periodic variation of the intensity of the light is detected and the etching rate or the etching end point is detected based on the period of the intensity of the interference light, the etching end point can be detected with high accuracy. Therefore, the accuracy of the etching end point detection is improved, and the reliability is improved.

Further, according to the apparatus of the present invention, the periodic fluctuation of the intensity of the interference light between the light reflected on the surface of the processing film and the light reflected on the interface between the processing film and the substrate is utilized by utilizing the light emission by the plasma. Since the etching rate or the etching end point is detected based on the above, a light source such as a laser is not required, and the etching rate or the etching end point can be detected with a relatively simple structure with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a processing substrate.

FIG. 3 is a diagram illustrating a change with time of a signal output from a detector.

FIG. 4 is a waveform diagram showing a result of temporally measuring the intensity of interference light when a SiO ₂ film on a silicon substrate is etched by a detector.

FIG. 5 is a diagram showing a temporal change in output of a photodetector when a SiO ₂ film on a silicon substrate is etched in a conventional plasma emission analysis type etching end point detecting apparatus.

FIG. 6 is a diagram showing a temporal change in the output of a photodetector when the etching rate is reduced in a conventional plasma emission analysis type etching end point detection apparatus.

FIG. 7 is a diagram showing a change over time in the output of a photodetector when the etching rate is increased in a conventional plasma emission analysis type etching end point detection apparatus.

FIG. 8 is a diagram showing a drawback of a conventional plasma emission analysis type etching end point detecting device.

[Explanation of symbols]

1 chamber 2 substrate 3 optical detection unit 4 detects the window 5 the cylindrical part 6 filter 7 Plasma 8 controller 9, 10 electrode 11 base 12 SiO ₂ film

Claims (6)

[Claims] 1. An etching apparatus for detecting an etching rate or an etching end point when etching a processing film on an underlayer by plasma etching, wherein, of light generated by plasma, light reflected on the surface of the processing film; A light detection unit for detecting the intensity of interference light between light reflected at the interface between the processing film and the base; detecting a periodic change in the output of the light detection unit; and etching rate based on the change cycle. Or a control unit for detecting an etching end point. 2. The photodetector comprises: a tubular portion which is provided upright on an etching chamber and through which light reflected on the surface of the processing film and light reflected on an interface between the processing film and the base are passed. A photodetector attached to an upper portion of the cylindrical portion; and a filter disposed closer to the chamber than the photodetector and selectively transmitting light of a specific wavelength among light passing through the cylindrical portion. The etching apparatus according to claim 1, wherein the etching apparatus comprises: 3. The control unit detects an etching rate from a periodic change of the light detection unit, and detects an etching end point from an initial film thickness of the processing film and the etching rate. The etching apparatus according to claim 1, wherein 4. The method according to claim 1, wherein the control section detects an etching end point when the number of periodic fluctuations of the output of the light detection section reaches a predetermined number. An etching apparatus as described in the above. 5. An etching method for detecting an etching rate or an etching end point when etching a processing film on a base by plasma etching, wherein light reflected by the surface of the processing film out of light generated by plasma. Detecting the intensity of interference light with light reflected at the interface between the underlayer and the processing film, and detecting an etching rate or an etching end point based on a cycle of a change in the intensity of the interference light. Etching method. 6. An etching method for detecting an etching end point when etching a processing film on a base by plasma etching, wherein light reflected by the surface of the processing film among light generated by plasma; Detecting the intensity of the interference light between the light reflected at the interface between the base and the processing film, obtaining the etching rate based on the period of the change in the intensity of the interference light, and determining the initial film thickness of the processing film and the etching. An etching method characterized by determining a remaining etching time from a rate.