JPH06342773A - Semiconductor processing monitoring apparatus - Google Patents

Abstract

PURPOSE:To measure damage done to a semiconductor in a process wherein a semiconductor is processed or an insulating film is deposited on a semiconductor by a method wherein a measuring optical system which monitors a reflected light or fluorescence is used as combined with a filter that blocks plasma emission. CONSTITUTION:A reference light 11 emitted from a spectral source 3 is made to irradiate the surface of a semiconductor specimen 2 placed in a plasma device 1, a reflected light 13 is detected by a photodetector 7 and amplified, and the intensity R14 of the reflected light 13 is measured. Then, an excitation light 12 radiated from an Ar laser 4 is turned into pulses by a chopper 5, the pulsed excitation light 12 is made to irradiate a region of the semiconductor specimen 2 irradiated with the reference light 11 to modulate the reflected light 13 in intensity, the intensity change DELTAR15 of the reflected light 13 caused by the excitation light 12 is measured by a lock-in amplifier 9, and a PR signal of DELTAR/R is obtained through a calculator 10. A filter 6 which blocks plasma emission 17 is arranged between the semiconductor specimen 2 and the photodetector 7 in a measuring optical system. By this setup, plasma emission 17, which is hard to separated from the reflected light 13 that impinges an the photodetector 7 in a usual method, can be separated and eliminated, so that only the reflected light 13 can be detected by the photodetector 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor processing step monitor in a semiconductor fine structure forming step, which is indispensable for manufacturing electronic devices and optical devices.

[0002]

2. Description of the Related Art Recently, an optoelectronic integrated circuit (OEIC) in which a GaAs compound semiconductor LSI and an optoelectronic element are integrated and integrated.
R & D is becoming active. Along with this, dry etching or a deposition technique of an insulating film has become more indispensable for device fabrication than ever before in order to miniaturize and integrate the device. These techniques utilize physical sputtering or film deposition action by ions generated by discharge plasma of gas, but generally, when these semiconductors are irradiated with the plasma, the semiconductor surface is damaged (point defects). Occurs, and as a result, there is a problem that semiconductor characteristics are significantly deteriorated. For this reason, it is desired to efficiently find out the condition in which the damage is unlikely to occur by monitoring the treatment process and monitoring the state of introduction of the damage, and to perform the treatment after that.

Conventionally, however, the photoluminescence (PL) method has been used as a non-destructive non-contact measuring method for damaging, but the light emission is weak at a temperature above room temperature,
Also, because of the disturbance of the measurement due to the emission of the plasma itself, the signal / noise ratio is kept low, and therefore no method has been proposed for monitoring the processing conditions. There is still a possibility of improving the signal / noise ratio by increasing the laser intensity for PL excitation, but in this case, alteration of the sample by the laser poses a problem, so it cannot be a realistic method. Absent. As described above, for the miniaturization and integration of elements, it is strongly desired to develop a damage monitoring device to be introduced in the processing step, but a specific method has not been forecast.

Recently, the inventors have applied a photoreflectance method (PR method) for measuring an electric field in the vicinity of a sample surface by using light reflection for use in damage measurement, and have a new feature of nondestructive and noncontact. A method was developed (Proceedings of Autumn 1992 Japan Society of Applied Physics, page 1151). In this method, as shown in FIG. 7, basically, the surface of the sample 2 is irradiated with the reference light 11 from the spectral light source 3, the intensity of the reflected light 13 is measured with respect to the wavelength, and the spectrum is obtained. It has a feature that the damages acting as the non-emission center and the charge compensation center can be measured from the intensity and the peak wavelength. Specifically, the reflected light 13 is detected by the photodetector 7, amplified by the current amplifier 8, and the reflected light intensity R14 is measured. Next, in parallel with this, the excitation light 12 from the Ar laser 4 is pulsed by the chopper 5, and the intensity of the reflected light 13 is modulated by irradiating the region on the sample 2 where the reference light 11 is irradiated, The intensity variation ΔR15 of the reflected light 13 obtained by the excitation light 12 by the laser pulse is measured by the lock-in amplifier 9 and a PR signal of ΔR / R is obtained by the computer.
The above method was applied to the evaluation of the damage introduced into the sample after plasma etching, and the high-sensitivity measurement method of the damage was established. In the above measuring system, even the Ar laser, which is the light source with the highest intensity, has a weak intensity of 1 mW / cm ² , and it can be suppressed to one digit or more lower than the laser intensity in the PL evaluation of a normal semiconductor. did it. As a result, the above problems could be solved and the alteration of the sample surface by the laser could be completely avoided.

[0005]

The PR method is applied to monitor the introduction of damage on the sample surface during plasma processing.
FIG. 2 is a PR spectrum measured during Ar plasma etching of GaAs. For reference, the same figure also shows a PR spectrum in a state where plasma is not formed. Here, for the purpose of removing scattered light due to excitation light on the sample surface, a short wavelength cut filter (a filter that transmits only light having a wavelength of 600 nm or more in the case of Ar laser) used in normal measurement is used. The measurement was carried out while it was on. Compared to the measurement made without Ar plasma, almost no signal was detected in the PR spectrum measured during plasma etching. The cause is related to the above problems. That is, when the PR measurement is performed during plasma etching, the reflected light 13 from the semiconductor sample 2 as shown in the conventional process monitoring apparatus of FIG.
And the strong plasma emission 17 emitted from the vicinity of the sample 2 enter the photodetector 7 at the same time. The plasma emission 17 is a high-intensity emission having a very wide spectrum width.
It becomes difficult to measure the reflected light 13 separately from the plasma emission 17, and the PR signal ΔR / R becomes extremely small. As described above, during the plasma treatment process, P
It has been experimentally revealed that a significant signal cannot be obtained even if the R measurement is performed. Therefore, in order to utilize the PR method as a monitoring device for the introduction of damage in the semiconductor processing process, it is essential to solve the above problems.

It is an object of the present invention to obtain a semiconductor processing step monitoring apparatus using the PR method, by reducing the influence of measurement of reflected light due to plasma emission.

[0007]

The above-mentioned object is to irradiate light on the semiconductor surface and monitor the reflected light or fluorescence during the plasma etching process of the semiconductor or the plasma deposition treatment process of the insulating film on the semiconductor. In a semiconductor processing step monitoring device for monitoring a processing step, a measuring optical system for monitoring the reflected light or fluorescence is combined with a filter for blocking plasma emission. It is achieved by the reflectance method.

[0008]

In order to monitor the semiconductor processing process using plasma, it is necessary to remove the light generated by plasma emission from the measurement optical system. The inventors have found that the above plasma emission 1
In order to clarify whether 7 can be removed, first, the spectrum of the plasma emission 17 was measured. FIG. 3 shows an example of an emission spectrum measurement result generated when GaAs was actually dry-etched by 100 W of Ar plasma. The voltage of the counter electrode 18 in the plasma device 1 is 100V. A broad spectrum is measured over the entire wavelength range of 800 nm or less. In addition, the emission spectrum of hydrogen plasma used in plasma deposition was also measured. As a result, it was found that a spectrum similar to the spectrum shown in FIG. 3 was obtained. From the above results, the removal of light by plasma emission is 800 n
It has been clarified that this is possible by combining filters that transmit light having a wavelength of m or more. PR for GaAs
Since the main peak of the spectrum appears near 870 nm,
By using this filter, the prospect of monitoring in the non-contact and non-destructive process of damaging introduction was obtained. In other words,
Except for semiconductors whose bandgap converted to wavelength is smaller than 800 nm, such as AlGaAs, at least PR
It has been found that the observation of the main peak (EO gap) of the spectrum is sufficiently possible even in plasma.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a semiconductor processing process monitoring apparatus according to the present invention, FIG. 4 is a diagram showing a time change of the amount of damage introduced in a GaAs dry etching process according to the above-described embodiment, and FIG. FIG. 6 is a diagram showing a change with time in introducing damage in the plasma deposition process of the SiO ₂ film on the SiO ₂ film, and FIG. 6 is a diagram showing a PR spectrum monitoring result during the InGaAs dry etching process according to the above-mentioned embodiment.

FIG. 1 shows an example of the configuration of a semiconductor processing process monitoring apparatus according to the present invention. By irradiating the surface of the semiconductor sample 2 installed in the plasma device 1 with the reference light 11 from the spectral light source 3,
The reflected light 13 is detected by the photodetector 7 and amplified by the current amplifier 8 to measure the reflected light intensity R14. Next, Ar
The excitation light 12 from the laser 4 is pulsed by the chopper 5 to irradiate the irradiation region of the reference light 11 on the semiconductor sample 2,
The intensity of the reflected light 13 is modulated, and the intensity change ΔR15 of the reflected light 13 due to the excitation light 12 of the laser pulse is measured by the lock-in amplifier 9, and the computer 10 obtains the PR signal 16 of ΔR / R. In order to eliminate the light emitted from the plasma incident on the photodetector 7 together with the reflected light 13,
The point that a filter 6 is arranged in the measurement optical system between the semiconductor sample 2 and the photodetector 7 is a feature different from the conventional plasma damage monitoring device.

The emission spectrum of the filter 6 is Ar.
Since it is 800 nm or less in plasma and hydrogen plasma, a filter which transmits only light having a wavelength exceeding 800 nm was used. By combining the filter 6 having such a light blocking effect with the measurement optical system,
Conventionally, the plasma emission 17 which has been difficult to separate from the reflected light 13 incident on the photodetector 7 can be separated and eliminated, and only the reflected light 13 can be detected by the photodetector 7.

In this embodiment, GaAs and InGaA are used.
The case of s will be described below. FIG. 4 shows a change in PR signal intensity with plasma etching of Ar.
Since the band edge of GaAs is around 870 nm, a Si detector was used as a detector for reflected light. Here, the PR signal (ΔR / R) was measured at 875 nm. The decrease in PR signal intensity due to plasma etching is clearly observed. It was found that the increase in the PR signal on the long time side was caused by the fact that the initially introduced damage layer was removed by plasma etching. As described above, the process of introducing the damage by plasma etching can be monitored on the spot, and the conditions for suppressing the damage can be efficiently extracted.

FIG. 5 shows changes in the PR signal during plasma deposition of the SiO ₂ film. First, it was found that the PR signal intensity decreases, but unlike the plasma etching, almost no signal recovery is observed. this is,
It was also clarified that in the plasma deposition, the surface damage that was initially introduced is not removed unlike the plasma etching, so that there is almost no recovery of the PR signal.

FIG. 6 shows a PR spectrum during Ar plasma etching of InGaAs. 800n for GaAs
Since it is a filter that transmits light with a wavelength of m or more, it was necessary to use only the peak of the PR spectrum for measurement.
Since InGaAs has a band gap of 1.6 μm, it is possible to measure a PR spectrum over almost all wavelengths. In this measurement, the reflection device irradiates the semiconductor surface with light during the plasma etching process of the semiconductor or the plasma deposition process of the insulating film on the semiconductor, and uses a Ge detector to measure the reflected light or the light intensity. I was there. It was revealed that the spectrum sharply decreased at the beginning of etching and then gradually recovered. The recovery rate is slower than that of GaAs, and it has become clear that in InGaAs, it is more important to optimize the etching conditions in which it is difficult to initially introduce damage.

In this embodiment, GaAs and InG are used.
Although the effects of the semiconductor processing step monitoring apparatus according to the present invention have been described by taking aAs as an example, it is needless to say that the present invention can be widely applied to all semiconductors such as Si and InP.

Further, it is needless to say that the present invention capable of removing plasma emission is extremely effective for methods other than the PR method when the purpose is to monitor the state of the sample in the plasma. Nor.

[0017]

As described above, the semiconductor processing step monitoring apparatus according to the present invention is capable of performing the plasma etching processing of the semiconductor or the plasma deposition processing step of the insulating film on the semiconductor,
A semiconductor processing step monitoring device for monitoring a processing step by irradiating the semiconductor surface with light and monitoring the reflected light or fluorescence, and a filter for blocking plasma emission in a measurement optical system for monitoring the reflected light or fluorescence. By combining these, it is possible to measure the damage that occurs in the processing steps such as semiconductor processing and insulating film deposition during the processing, and this suppresses the damage that causes the deterioration of device performance and reliability. , The process design can proceed efficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a semiconductor processing step monitoring apparatus according to the present invention.

FIG. 2 is a diagram showing an example of PR spectrum measurement during plasma etching.

FIG. 3 is a diagram showing measurement results of spectra in plasma emission.

FIG. 4 is a diagram showing a change over time in the amount of damage introduced in a GaAs dry etching process according to the above-mentioned embodiment.

FIG. 5 is a diagram showing a time change of useless introduction of a plasma deposition process of a SiO ₂ film on GaAs according to the above-mentioned embodiment.

FIG. 6 is a diagram showing a result of monitoring a PR spectrum during an InGaAs dry etching process according to the above example.

FIG. 7 is a diagram showing an example of a plasma device with a conventional plasma damage monitoring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma device 2 Semiconductor sample 3 Spectral light source 6 Filter 7 Photodetector 13 Reflected light 17 Plasma emission

Claims (2)

[Claims] 1. A semiconductor for monitoring a processing step by irradiating the surface of the semiconductor with light and monitoring the reflected light or fluorescence during the processing of plasma etching of the semiconductor or plasma deposition of an insulating film on the semiconductor. In the processing step monitoring device, a semiconductor processing step monitoring device characterized in that a filter for cutting off plasma emission is combined with the measurement optical system for monitoring the reflected light or fluorescence. 2. The semiconductor processing step monitoring apparatus according to claim 1, wherein the reflected light is monitored by a photoreflectance method.