JPS638187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry etching apparatus for etching a substrate to be processed in a gas discharge.

In the manufacturing process of electronic components such as semiconductor integrated circuits,
A dry etching method is employed in which etching is performed in a gas discharge using a resin pattern formed by optical photolithography as a mask to form a desired pattern on a substrate to be processed. In this case, the conventional method of determining whether or not etching of the substrate to be processed has been completed is to visually observe discoloration of the substrate surface when the base of the substrate is exposed after etching. There is a problem in that not only the judgment becomes uncertain depending on the shape of the pattern formed by the processing and the material to be processed, but also that the operator has to continuously monitor the progress of etching. One method of solving these problems and determining the end point of etching the substrate to be processed is to observe changes in the light emission of the gas discharge using a photoelectric element such as a phototransistor. However, the method of simply observing the luminescent color of discharge,
Depending on the material to be etched of the substrate to be processed, changes in the color of the gas discharge emission may hardly be observed.
For example, in the case of etching an aluminum film by carbon tetrachloride gas discharge, it is almost impossible to detect the difference between whether the aluminum is etched or not using a photoelectric element such as a phototransistor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry etching apparatus that can clearly determine the end point of etching for almost any material to be etched.

The principle of the present invention is to spectrally analyze the excitation light of atoms emitted from the substrate to be treated that are mixed into the discharge atmosphere or of radicals containing those atoms generated by chemical reactions, and to observe changes in the intensity of this specific spectrum. The purpose is to determine when etching of a substrate to be processed is completed.

The present invention will be explained in detail below using the drawings.

FIG. 1 shows a first embodiment of the present invention, in which the etching apparatus main body 11 includes plate-shaped electrodes 13 and 15 arranged in a vacuum container 12, and an insulator 16 that insulates one electrode 13 from the apparatus main body. , an etching gas inlet 17 connected to an etching gas introduction system (not shown), and an exhaust port 18 connected to an exhaust pump system (not shown). placed next to each other. The emission spectrum observation system has 2 observation windows made of quartz glass.
1. A condenser lens 22 made of quartz glass, a monochromator 23, a photomultiplier tube 24, a DC amplifier 25,
It consists of 26 recorders.

The electrode 13 of the etching apparatus having such a configuration
Power is applied to the high frequency power supply 31 connected to 15,
Etching gas discharge is generated between the electrodes, and the discharge luminescence is passed through a viewing window 21 attached to the container 12 and a condensing lens 22, and is separated into spectra by a monochromator 23.
The obtained spectrum is set to a voltage level that is easy to observe using a photomultiplier tube 24 and a DC amplifier 25, and is recorded using a recorder 26. FIG. 2 shows the emission spectrum during discharge when carbon tetrachloride was introduced as an etching gas, with no substrate to be processed. FIG. 3 shows the emission spectrum when an aluminum plate is placed on the electrode 13 as the substrate 14 to be processed, and both figures were measured by continuously changing the spectral wavelength of the monochromator 23. In this case, the electrode area is 1200cm ² , the carbon tetrachloride pressure is 0.05Torr, and the aluminum substrate area is
The 40cm ² high frequency power density was 0.25W/cm ² . The main changes in the emission spectrum depending on the presence or absence of an aluminum substrate to be etched are shown in Figure 3A.
This is the spectrum that occurs when aluminum in the locations shown in ~E is etched, and A
is the spectrum of Alcl radical with wavelength 261.6nm,
B and C are Al spectra with wavelengths of 308.2 nm and 309.3 nm, respectively, D and E are with wavelengths of 394.4 nm, respectively,
This is an Al spectrum at 396.2nm. In general, compounds having three or more atoms have a wide spectral line width and a small peak intensity, so their spectra are not suitable for monitoring etching.

Figure 4 shows the observation wavelength of monochromator 23.
This is a record of the change in luminescence intensity over time when a glass substrate of 50 mm x 50 mm and 1.6 mm thick was fixed at 261.6 nm and coated with aluminum to a thickness of 1 μm. The discharge time on the horizontal axis in the figure indicates the elapsed time from the start of discharge at a predetermined high-frequency power. Point P in the figure is the point when the discoloration of the aluminum surface is visually confirmed and etching has started, and point Q is the point when a part of the substrate to be processed has finished etching and the underlying glass surface is exposed. R indicates the point at which the aluminum film on the glass substrate is completely etched away and the underlying glass surface is completely exposed. In this way, visual observation of the substrate to be processed and
The intensity changes of the AlCl radical emission spectra showed a clear correspondence, and similar correspondences were obtained for other aluminum atomic spectra. Therefore, when etching a substrate to be processed, the etching process can be sufficiently monitored by monitoring changes in a predetermined spectral intensity instead of monitoring the state of the surface of the substrate to be processed. In Figure 4, we observed temporal changes in the spectra related to the material of the etched film.As the etching progresses and the underlying layer of the film to be etched is exposed and begins to be etched, the temporal changes in the spectra related to the material of the underlying layer are observed. can also be observed.

Another embodiment of the invention is shown in FIG. 11 in the diagram
19, 21 to 25 are the same as those in the first embodiment shown in FIG.
(hereinafter referred to as a determination circuit) is connected to a high frequency power source 32 that can control opening and closing of power supply. The determination circuit 28 has a function of calculating and determining the output of the DC amplifier 25, and performs differential calculations on the output of the amplifier 25 to determine the point at which the temporal decrease in the output voltage of the amplifier 25 becomes zero. It also has the function of generating a reference signal at the end of etching, and has a built-in timer. In practical etching processing, it is appropriate to perform some over-etching in order to remove the slight amount of processing material remaining on the underlying surface of the processing substrate, and after generating a reference signal, a timer is set. After the time has elapsed, a signal is sent to the high frequency power source 32 to cut off the power of the power source and stop the discharge 19. Further, in order to avoid errors in judgment due to instantaneous fluctuations in emission spectrum intensity due to instability of discharge, it is preferable to provide a noise removal circuit in the determination circuit 28. In this way, the etching process on the substrate to be processed can be carried out reliably without operator supervision.

The present invention is not limited to determining the end point of etching treatment of an aluminum film as described in the above embodiments.
It is obvious to those who work with optical spectra that a similar implementation method can be applied to etching films other than aluminum by observing atomic spectra or diatomic radical spectra specific to various materials.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention,
Figure 2 is an emission spectrogram of carbon tetrachloride gas discharge, Figure 3
The figure is a discharge emission spectrogram during etching treatment of an aluminum plate in a carbon tetrachloride gas discharge.
The figure shows a record showing the time course of the spectral intensity at a wavelength of 261.6 nm, and FIG. 5 shows an explanatory diagram showing another example. In the figure, 1 is the etching device main body, 1
2 is a vacuum container, 13 is an electrode, 14 is a substrate to be processed,
15 is a counter electrode, 16 is an insulator, 17 is an etching gas inlet, 18 is an exhaust port, 19 is an etching gas discharge, 21 is a viewing window, 22 is a condensing lens, 23 is a monochromator, and 24 is a photomultiplier. 25 is a DC amplifier, 26 is a recorder, 28 is an end determination circuit, and 31 and 32 are high frequency power sources.

Claims (1)

[Claims] 1. An apparatus for etching an aluminum substrate to be processed by discharging an etching gas in a vacuum container, and an apparatus for etching an aluminum substrate to be processed by discharging an etching gas in a vacuum container, and a method for controlling the spectrum of molecules of an aluminum compound among the emission spectra of the material to be processed generated during the etching process. a detector for detecting a change; an etching completion determination circuit having a function of processing the output of the detector and generating a reference signal at the end of etching and having a built-in timer; A high-frequency power source is provided to control switching on and off of power supply to the etching processing apparatus in conjunction with the circuit, and the etching completion determination circuit controls the etching process after an arbitrary time set by a timer has elapsed after the reference signal is generated. A dry etching device characterized in that a discharge stop signal is sent to a high frequency power source. 2. The dry etching apparatus according to claim 1, wherein the etching completion determination circuit is provided with a noise removal circuit.