JPH02210825A - Plasma etching method and equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma etching method and apparatus, and particularly to a plasma etching method and apparatus suitable for two-stage etching processing of samples such as semiconductor element substrates. It is.

[Conventional technology]

As a technique for performing a two-stage etching process on a substrate as a sample using plasma, for example, Japanese Patent Application Laid-Open No. 62-30891
A method is known in which a substrate is subjected to a two-stage etching process mainly using microwaves, using only high-density ions and neutral radicals generated by plasma confinement, as described in the above publication.

[Problem to be solved by the invention]

When a sample is subjected to two-stage etching using plasma as in the prior art described above, the second-stage etching is performed after confirming that the first-stage etching has been completed. The end point of such an etching process is normally determined by an end point detection technique using emission spectroscopy.

In other words, when performing a two-stage etching process on a sample using plasma, the end point of the first stage etching process is determined by emission spectroscopy, and then the plasma generation control parameters are changed in accordance with the second stage etching process. Then, a second stage etching process is performed using plasma generated by changing the plasma generation control parameters.

However, in such a case, changing the plasma generation control parameter causes a change in plasma density, that is, a change in plasma emission intensity.

As a result, a problem arises in that an erroneous operation occurs in determining the end point of the first stage etching process, and the second stage etching process cannot be performed satisfactorily.

During this period, the sample is not subjected to two-stage etching process,
This problem also occurs in sample etching processing where it is necessary to change plasma generation control parameters during the sample etching process.

Further, such a problem occurs conspicuously in the etching process of a sample in which, for example, the etching area of a contact hole or the like is small, so that the change in the plasma emission intensity for determining the end point of the etching process is small.

Note that the above-mentioned prior art does not take any consideration to such problems.

A main object of the present invention is to provide a plasma etching apparatus and apparatus that can satisfactorily perform an etching process on a sample that requires changing plasma generation control parameters during the etching process on the sample.

[Il! Means to solve the problem]

The above main purpose is to improve the plasma etching method by changing the plasma generation control parameters during the plasma etching process of the sample and further etching the sample, and the process of further etching the sample when the parameters are changed. and a step of determining the etching end point corresponding to a change in iK. This is achieved by comprising means for changing the production control parameter of , and means for determining the kneeing end point in response to a change in the emission intensity of the plasma when the M parameter is changed.

[For production]

Two-stage etching is usually performed to reduce selectivity to the substrate or damage to the substrate. Therefore, in the end point determining means, the problem can be solved by shifting the timing of the plasma fluctuation due to the parameter change in the second stage and the end point determining time.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In Figure 1, 1 is a vacuum vessel, 2 is a cathode, and 3 is 1
An anode nozzle that constitutes a node and is connected to an etching gas supply device; 4 is a wafer as a sample; 5 is a cover; 6 is a window provided in the vacuum container 1; through this window, plasma light is detected. It is taken into the container 7.

8 is an RFM transmitter, which applies an RF voltage to the cathode 2; The cathode 2 and the vacuum vessel l are insulated with a suitable insulating material. Reference numeral 9 denotes a vacuum evacuation system, which is capable of evacuation from the vicinity of the cathode. A magnet 10 is placed above one node, is attached to a turntable 13, and can be rotated by a motor ν.

Figure 1g2 shows the relationship between etching gas and pressure when etching the insulating film of the contact hole using the magnetic field reactive ion etching apparatus shown in Figure 1. It shows the relationship between the taper angle of the contact hole, the selection ratio with respect to the base 81, and the pressure,
(b) shows the relationship between emission intensity and pressure at RF powers soow and soow.

As can be seen from Figure 2 (a), in order to increase the taper angle of the etching shape in order to improve the coverage during film formation of the M wiring in the first step, it is necessary to perform the process at a high pressure location. Desirably, in order to increase the selectivity with respect to the base 8i, it is desirable to perform the treatment in a place with low pressure. Therefore, if etching is performed in two steps, with high pressure until overetching and low pressure during overetching, a large taper angle and a high selectivity with respect to the underlying layer 8i can be obtained.

As shown in FIG. 2(b), when the pressure is lowered, the plasma density is lowered, and the emission intensity is accordingly lowered. During two-stage etching in which the pressure is varied, this change in emission intensity and the gradual completion of etching may overlap with the change in emission intensity at 4 o'clock, causing a malfunction in detecting the end point. In this embodiment, parameters are changed so as to eliminate such changes in emission intensity. That is, as the pressure decreases, the RF
Increase the power (from point A to point B in Figure 2 (b))
Emission intensity can be kept almost constant.

Although the RF power was varied in this embodiment, similar effects can often be obtained by varying the amount of etching gas used.

A second embodiment of the present invention is shown in FIGS. 3-5.

This example uses the above-mentioned magnetic field reactive ion etching gt.
! This is an example in which the error in determining the end point due to the change in 5-51 light intensity due to the pressure drop when performing two-stage etching of an oxide film using the method of the corner.

Figure 3 is etching! This shows the control system of the kit, including the pressure adjustment mechanism 15. The output of the light emission detector 7 is input to the microcomputer 14 which controls the gas supply @il 11 and the discharge system control circuit 16.

The control shown in FIG. 4 is performed within the microcomputer 14. First, it is determined whether kneeing is in the second stage. This determination is made by setting the required time based on the known etching speed and performing time management. When the set time has elapsed, the parameter (pressure) is lowered from the state shown in FIG. 5(b) and the second stage of etching begins.

Next, after waiting until the pressure stabilizes (in Fig. 4, the elapse of the stabilization time is determined), the end point determination software is activated. The etched shape at the start of the end point determination is shown in FIG. 5(C), and the etched shape at the end is shown in FIG. 5(d).

According to this example, when starting the end point determination, there is still a slight amount of the insulating film left to be etched, and the etching is not affected by the change in the emission intensity due to the pressure reduction due to the two-step etching. It is possible to determine the end point without errors in normal overetching.

A third embodiment of the present invention will be described using FIG. 6. 6th
The figure shows an RF bias controlled magnetic field microwave plasma etching apparatus. Etching gas is introduced into the vacuum chamber 4, and the microwave electric field generated by the magnetron Z and the magnetic field generated by the magnetic field coil are applied to generate plasma, and the radicals and ions in the plasma are used to etch the wafer. etching. RF3i on sample stage I
The shaker is connected and a negative bias voltage is generated on the sample stage. Therefore, the etched shape of the wafer can be controlled by the action of ion energy. The gas pressure in the vacuum container is maintained at a predetermined value by evacuating the gas from the exhaust point by the vacuum exhaust system 4.

Hereinafter, another embodiment of the present invention will be described in which a gate material and an M wiring material are etched in two stages using the etching apparatus described above.

When etching gate materials and M wiring with μ-wave plasma, it has been found that high bias provides high etching speed and anisotropy, while low bias provides high selectivity (with respect to the underlying 8402) and low damage. There is. On the other hand, when the bias voltage is changed, the emission intensity also decreases slightly. Therefore, by compensating for the decrease in the generated intensity when changing the bias voltage by increasing the μ-wave power, the decrease in the emission intensity can be suppressed and the end point can be determined without error.

Further, the gas flow rate may be changed in order to improve the selectivity with the substrate. In this case as well, changes in emission intensity can be compensated for by changing the μ-wave power.

〔Effect of the invention〕

According to the present invention, it is possible to maintain the advantages of two-stage etching in terms of etching characteristics, and to avoid errors in end point determination due to changes in plasma density during two-stage etching.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a block diagram and etching characteristic diagram of an etching apparatus according to an embodiment of the present invention, and FIGS. 3 to 5 are a control circuit and a control flow for illustrating a second embodiment of the present invention. 65A is a diagram showing the configuration of an etching apparatus according to a third embodiment of the present invention. 7... Luminescence detector, 8, 28... RF
3! Shaker, 11... Gas supply device, 14...
... End point determination means, Takumi ... Pressure adjustment mechanism, 16
...discharge system control circuit, 17...mask, edict...oxide film, 19...ski board,
2... Magnetron O! Figure A2 Flash F

Claims (1)

[Scope of Claims] 1. A step of performing a two-stage etching process on the sample by changing the parameters of the plasma during the plasma etching process of the sample, and responding to a change in the emission intensity of the plasma when the parameters are changed. A plasma etching method comprising the step of determining an etching end point. 2. The plasma etching method according to claim 1, wherein the time when the emission intensity of the plasma changes due to the change of the parameter and the time when the etching end point determination is performed are shifted. 3. The plasma etching method according to claim 2, wherein the etching end point determination is performed after the emission intensity of the plasma becomes stable due to the change of the parameters. 4. performing a two-stage etching process on the sample by changing the main parameters of the plasma during the plasma etching process of the sample; and compensating for changes in the emission intensity of the plasma when the main parameters are changed; A plasma etching method comprising: determining an etching end point based on a compensated change in plasma emission intensity. 5. The plasma etching method according to claim 4, wherein a change in the emission intensity of the plasma when the parameter is changed is compensated for by changing another parameter different from the parameter. 6. The plasma etching method according to claim 5, wherein the parameter is etching gas pressure, and the other parameter is power required for discharge or etching gas flow rate. 7. The plasma etching method according to claim 5, wherein the parameter is high frequency power applied to the sample, and the other parameter is microwave power required for microwave discharge. 8. The plasma etching method according to claim 5, wherein the parameter is an etching gas flow rate and the other parameter is microwave power required for microwave discharge. 9. A step of performing a two-stage etching process on the sample by changing the parameters of the plasma during the plasma etching process of the sample, and a process of over-etching the sample after the emission intensity of the plasma becomes stable due to the change of the parameters. A plasma etching method characterized by: 10. In a two-stage etching method for an oxide film using plasma, the first stage is performed at a pressure that creates a shape with a large taper angle, and the second stage is performed at a lower pressure to select the underlying silicon. A plasma etching method characterized by improving the ratio. 11. The plasma etching method according to claim 10, wherein the first stage is processed at a pressure of 5 to 10 mTorr, and the second stage is processed at a pressure of 0.5 to 2 mTorr. 12. means for converting etching gas into plasma under reduced pressure, and means for changing the plasma generation control parameters during etching processing of a sample using the plasma;
A plasma etching apparatus characterized by comprising means for determining an etching end point corresponding to a change in the plasma generation intensity when the parameter is changed. 13. The plasma etching apparatus according to claim 12, wherein the etching end point determination means is a means for performing the etching end point determination after the emission intensity of the plasma becomes stable due to the change of the parameters. 14. means for converting etching gas into plasma under reduced pressure; means for changing main parameters for controlling the plasma generation during etching processing of a sample using the plasma; and light emission intensity of the plasma when changing the main parameters. 1. A plasma etching apparatus comprising: means for compensating for changes in plasma emission intensity; and means for determining an etching end point based on the compensated change in plasma emission intensity. 15. The plasma etching apparatus according to claim 14, wherein said plasma emission intensity change compensation means and means for compensating by changing another parameter different from said main parameter.