JPH0723548B2 - Dry etching end point detection method - Google Patents

Description

The present invention relates to a dry etching technique, and more particularly to a dry etching end point detection method using plasma.

[Conventional technology]

Conventionally, as an endpoint detection method for dry etching using plasma, there is an endpoint detection method that uses a change in the intensity of plasma emission.

[Problems to be Solved by the Invention]

The above-mentioned etching end point detection method using the change in plasma emission intensity is applied to detect the etching end point by observing the plasma state during etching by its emission analysis. Plasma emission is a phenomenon caused by active gas species existing in plasma, and the study of plasma emission has been developed as a plasma diagnostic technique by spectrum analysis. The plasma emission spectrum depends on the reaction gas and reaction products in the plasma, and the etching reaction is observed by observing the temporal change in the emission intensity of a specific wavelength, that is, the emission intensity of a specific substance present in the plasma. Changes in products or reactive species can be known. The method utilizing this technique is a method for detecting the etching end point based on the plasma emission intensity.

In order to detect the etching end point using such a method, it is necessary to know the wavelength at which the emission intensity changes with the progress of etching. That is, it is indispensable to examine in advance the emission wavelength that accurately reflects the fluctuation of the active species in the plasma caused by the end of etching, which is not convenient. Also, there may be no suitable plasma emission. Further, in order to carry out this method, it is necessary to provide the etching device with a window portion for performing emission spectroscopy, and further, a spectroscopy device, a light receiving element and a driving circuit thereof are required, which is expensive.

[Means for Solving the Problems]

The dry etching end point detection method using plasma according to the present invention detects the etching end point from the potential change of the sample to be etched.

This potential measurement can be easily performed without any preparation in advance, unlike the conventional plasma emission method, in which it is necessary to select the wavelength for monitoring in advance, and without any change from the usual voltage measurement. In addition, the circuit for measuring the electric potential can separate and measure the DC component that is synthesized at high frequency.
For example, a rectifier circuit is good and inexpensive.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is an apparatus configuration diagram for carrying out the present invention in a parallel plate type dry etching apparatus. High frequency power supply 106
The cathode voltage measuring circuit 101 is connected to the connection line between the matching circuit 105 and the cathode 102, and the potential of the etching sample is measured. A rectifier circuit including a diode, a capacitor, and a coil is shown as an example of the cathode voltage measuring circuit 101, but any circuit capable of measuring a DC potential included in a high frequency may be used.

Example 1 FIG. 2 shows an example of detecting the etching end point when the three-layer resist lower layer organic film etching is performed in the above-described dry etching apparatus having the cathode potential measuring circuit. The three-layer resist used here is a normal novolac resist having a thickness of 0.5 μm as the upper layer resist 203 and a thickness of 150 as the intermediate layer.
0 Å coated oxide film 202, lower organic film 201 has a thickness of 2 μm
It has a three-layer structure shown in FIG. 2 (b), which is composed of a novolak resist baked at 250 ° C. for 90 minutes. The upper layer resist 203 is patterned by a lithography process, and the coated oxide film 202 of the intermediate layer is patterned by an etching process using the upper layer resist 203 as a mask.

Using the upper resist 203 and the intermediate layer as a mask, the lower organic film 201 was etched.

Oxygen is used as etching gas, flow rate 20 sccm, pressure 10
Etching was performed under the condition of mTorr high frequency power of 600 W. FIGS. 2 (b), 2 (c) and 2 (d) show the changes in the cathode potential after etching for 0 hour, 1 hour and 2 hours in FIG. 2 (a). The cathode potential rises after applying high-frequency power and reaches about 250V. After that, it is almost constant until the etching of the upper layer resist 203 is completed, and after the etching of the upper layer resist 203, it rises to about 340V. When the etching of the lower layer resist is completed, the voltage rises to about 400 V and the etching end point is detected.

In addition to the measurement example of the cathode potential, FIG. 2 shows a diagram schematically showing the etching state of the three-layer resist. After applying a high frequency, the three-layer resist changes from FIG. 2 (b) to upper layer resist etching completion FIG. 2 (c) and lower organic film etching completion FIG. 2 (d), and the cathode potential changes accordingly. It changes to about 250V, 340V, 400V.

[Embodiment 2] FIG. 3 is an example of detecting the etching end point by measuring the cathode voltage when polysilicon etching is performed using the above-described apparatus. Polysilicon is phosphorus-doped, and a film having a thickness of 4000 Å was etched. A 1.2 μm thick resist was used for the mask. The base is a thermal oxide film. As the etching gas, for example, a mixed gas of sulfur hexafluoride and carbon difluoride dichloride was used, and the respective flow rates were set to 20 sccm and 30 sccm. Etching pressure is 30mTorr
Etching was performed under the condition of high frequency power of 200W. The cathode potential was constant at about 170 V during etching and dropped to 160 V at the end point, and the end point of etching was detected.

〔The invention's effect〕

As described above, according to the present invention, by measuring the potential of the sample to be etched in plasma, the change in the layer structure of the sample can be known and the etching end point can be detected.

[Brief description of drawings]

FIG. 1 is an apparatus configuration diagram for carrying out the present invention in a parallel plate type dry etching apparatus, and FIGS. 2 and 3 are examples of detection of etching end points obtained in organic film etching and polysilicon etching, respectively. , Fig. 2 (a)
And FIG. 3 is a diagram showing changes in voltage, FIG. 2 (b),
(C) and (d) are cross-sectional views of the sample showing the etching state at each time point in FIG. 2 (a). 101 ... Cathode voltage measuring circuit, 102 ... Cathode, 103 ... Etching sample, 104 ... Anode, 105 ... Matching circuit, 106 ...
High-frequency power source, 107 ... vacuum exhaust device, 108 ... reaction gas inlet tube, 201 ... lower organic film, 202 ... coating oxide film, 203 ...
… Upper layer resist, 204… Substrate.

Claims (3)

[Claims] 1. A dry etching process using plasma, wherein a DC voltage included in a high frequency voltage applied to a cathode on which a sample to be etched is placed is taken out, and the end of etching is detected by a change in the DC voltage. And a method for detecting the end point of dry etching. 2. The direct current voltage receives the high frequency voltage,
The end point detection method for dry etching according to claim 1, wherein the measurement is made by a measuring circuit including a capacitor, a coil, a rectifier and a resistor. 3. A device for processing an electric signal obtained from the measuring circuit and automatically detecting an etching end point is added to the etching device, and the etching device is automatically controlled by the signal. 2. The method for detecting the end point of dry etching according to 2.