JPH0343772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma etching apparatus used in the manufacture of semiconductor devices, and particularly to a plasma etching apparatus that controls the etching rate of a sample to be etched during etching and improves the reliability of the etching process. The present invention relates to a plasma etching apparatus that can improve etching performance and significantly improve the manufacturing yield of semiconductor devices.

[Conventional technology]

In the manufacture of semiconductor devices, device patterns are becoming increasingly finer. Therefore, it is important to improve the accuracy in the etching process for forming device patterns. In the conventional wet etching method using a solution such as an acid, no improvement in accuracy can be expected in principle. Therefore, in place of the wet etching method, the dry etching method has recently started to become popular. A typical dry etching method is a plasma etching method. The general configuration of a plasma etching apparatus for this purpose is shown in FIG. Here, a reaction gas is allowed to flow into the etching chamber 1 from the reaction gas inlet 5 and is evacuated from the exhaust port 6 with a vacuum pump to maintain the pressure inside the etching chamber 1 at a predetermined pressure. This pressure range is
10 ^-2 to 10 ^-1 Torr is common. When a sample 4 to be etched is placed on the sample electrode 3 and a high frequency voltage is applied from a high frequency power supply 7 between the counter electrode 2 and the sample electrode 3, a glow discharge occurs between the two electrodes and plasma is generated. The sample 4 to be etched is etched by the active atoms and ions in this plasma. Note that either the sample electrode 3 or the counter electrode 2 is often used with earth potential.

Such conventional devices have several drawbacks, one of which is instability in the etching rate. If the etching speed is unstable, the processing time required for etching cannot be determined.
This causes insufficient etching or excessive etching.
Another drawback is that when multiple etched samples are plasma-etched at once, the etching speed differs for each individual etched sample, and although some etched samples are underetched, others Etched samples have problems such as excessive etching, i.e.
The disadvantage is that the etching rate is not uniform. In Fig. 1, the sample to be etched 4 is 3
Although the case of two is shown as an example, the same problem occurs even in the case of one. That is, since the etching rate is not uniform even within one sample to be etched, there is a drawback that, for example, although the central portion of the sample to be etched is under-etched, the peripheral portion may be over-etched.

Insufficient etching causes short circuits between device patterns, while excessive etching causes disconnection of device patterns and damage to the underlying substrate, both of which significantly reduce the manufacturing yield of semiconductor devices.

[Problem to be solved by the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, to control the etching rate of the sample to be etched during etching, and thereby to improve the reliability of the etching process.
It is an object of the present invention to provide a plasma etching apparatus that can significantly improve the manufacturing yield of semiconductor devices.

[Means to solve the problem]

To this end, in the present invention, during etching of the sample to be etched, the etching rate or the amount corresponding to the etching rate is converted into an electrical signal,
Based on this electrical signal, the etching rate of the sample to be etched can be controlled during etching.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings. In FIG. 2, counter electrodes 17, 18 and 19 are arranged corresponding to samples to be etched 14, 15 and 16, and sensors 20, 21 and 22 are installed on each counter electrode 17, 18 and 19. sensor 20,
Signals from 21 and 22 are sent to drive mechanism 2, respectively.
3, 24 and 25. drive mechanism 23,
24 and 25 amplify each sensor signal from the sensors 20, 21 and 22 and compare it with a reference voltage signal to generate a feedback signal, and the counter electrodes 17,
Support rods 26, 27 and 28 connected to sensors 18 and 19 are individually moved upward or downward in response to each signal from sensors 20, 21 and 22. By moving the counter electrodes 17, 18 and 19 independently upward or downward to change the distance between them and the sample electrode 3, the electric field strength of the high frequency power source 7 can be adjusted to By changing the plasma density on the surface of each etched sample 14,
Etching speeds 15 and 16 can be maintained at the same and predetermined value to improve uniformity. These sensors 20, 21 and 22 have the function of converting the etching rate or a quantity corresponding to the etching rate into an electrical signal.

A known sensor can be used as the sensor. An example is shown below. First, there is a sensor that detects a specific wavelength during plasma emission. for example
When etching Al using CCl ₄ as a reaction gas, a sensor capable of detecting the 261.1 nm wavelength caused by AlCl is available from BJCurtis, HJBrunner: J.
Electrochem.Soc., 125829 (1978). The emission intensity at this wavelength of 261.4 nm corresponds to the AlCl concentration in the plasma, that is, the etching rate. A sensor that detects such a specific wavelength is effective not only for etching Al using CCl ₄ but also for etching Si or Si ₃ N ₄ using CF ₄ -based reactive gas. A spectrometer may be used as the sensor structure, or a simple combination such as an optical filter that transmits only a specific wavelength and a photodiode may be sufficient.

Other sensors include mass spectrometers and their combinations with ion energy analyzers. As a sensor used with a mass spectrometer, for example, there is a sensor that detects the peak velocity of SiF ₃ ⁺ (M/l=85) generated when SiO ₂ is etched with a CF ₄ -based reaction gas. (M.Oshima: Japan.J.Appl.
Phys., 17579 (1978)). By detecting this peak intensity, the etching rate can be determined. Furthermore, there are those that utilize laser interference (JABondur, WRCase, HAClark;
Electrochemistry.Society. Spring Meeting
Abstract, No. 303 (1978)). This is SiO ₂ , Si ₃ N ₄
This sensor measures the film thickness of polycrystalline Si, etc. using laser interferometry, and can detect etching speed from changes in film thickness over time.

In addition to the above, there are sensors using ellipsometry, sample temperature measurement, and the like.

FIG. 3 shows an embodiment in which the etching rate within one sample 50 to be etched can be locally controlled.
It is divided into three ring-shaped electrodes 2 and 43, and support rods 44, 45 and 46 and sensors 47, 48 and 49 are attached to each ring-shaped electrode 41, 42 and circular electrode 43.
are provided respectively. Even in the case of such a configuration, the distance between the sample to be etched 50 and the counter electrodes 41, 42, and 43 can be independently controlled in the same manner as in the example shown in FIG. A predetermined uniform etching rate can be maintained over the entire surface.

The present invention is not limited to the example described above, but can, for example, combine the examples shown in FIGS. At the same time, the etching rate can be controlled uniformly and to a predetermined level. Furthermore, the number of sensors and feedback circuits does not need to be the same as the number of counter electrodes; for example, one
By scanning a plurality of sample surfaces to be etched with a laser beam, the number of sensors can be reduced to one. In addition to making the etching rate uniform, it is also possible to independently control the etching rate to any desired value among multiple samples to be etched, or to control the etching rate at each location within the plane of a single sample to be etched. You can also control the speed as you like. It is also possible to program the etching speed according to the etching time, and for example, to control the etching speed at any desired value at the beginning of etching and near the end of etching. It goes without saying that the sensor used in the present invention can also be used to determine the end point of etching.

〔effect〕

As explained above, according to the present invention, in plasma etching, the etching rate can be controlled between multiple etched samples or at each part of one etched sample during etching of the etched sample. , a high-quality device pattern can be obtained, and the manufacturing yield of semiconductor devices can therefore be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional plasma etching apparatus, FIG. 2 is a cross-sectional view showing an embodiment of the plasma etching apparatus of the present invention, and FIG. 3 is a perspective view showing an example of the electrode structure in the plasma etching apparatus of the present invention. be. 1... Etching chamber, 2... Counter electrode, 3...
Sample electrode, 4... Sample to be etched, 5... Reaction gas inlet, 6... Exhaust port, 7... High frequency power supply,
14, 15, 16...Sample to be etched, 17,
18, 19... counter electrode, 20, 21, 22...
Sensor, 23, 24, 25... Drive mechanism, 26,
27, 28... Support rod, 41, 42, 43... Counter electrode, 44, 45, 46... Support rod, 47, 4
8, 49...sensor, 50...sample to be etched.

Claims (1)

[Claims] 1. A reactive gas is flowed into and exhausted from an etching chamber having a sample electrode on which one or more samples to be etched are placed, and a counter electrode that faces each sample to be etched, so that the etching chamber is kept at a constant temperature. A plasma etching apparatus that etches the sample to be etched using gas plasma generated by applying a high frequency voltage between the sample electrode and the counter electrode while maintaining the degree of vacuum within a range, The counter electrode facing the sample to be etched is constituted by a concentric electrode divided into a plurality of parts, and a means for detecting an etching rate of the sample to be etched or an amount corresponding to the etching rate during etching of the sample to be etched. By converting the etched sample into an electric signal and independently changing the distance between the sample electrode and each electrode of the plurality of concentric electrodes based on the electric signal, each part in the plane of the sample to be etched is 1. A plasma etching apparatus characterized in that the etching rate in the etching process is controlled during etching of the sample to be etched.