JPH01301871A - Method for detecting end point of dry etching - Google Patents

Abstract

PURPOSE:To conveniently measure the end point of etching of a sample by measuring the potential change of the sample to be etched in plasma. CONSTITUTION:A cathode potential measuring circuit 101 is connected to a wire connecting a high-frequency power source 106, a matching circuit 105, and a cathode 102 in an etching device, and the potential of the sample to be etched is measured. In a three-layer resist, for example, the cathode potential increases after the impression of a high-frequency power and is kept almost constant until the etching of the upper resist is finished. After the etching of the upper resist, the cathode potential increases and further increases when the etching of the lower resist is finished, and the end point of etching is detected. The cathode potential measuring circuit 101 consists of a capacity for measuring the DC potential of the sample 103 to be etched, a coil, a rectifier, a resistance, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to dry etching technology, and more particularly to a method for detecting the end point of dry etching using plasma.

[Conventional technology]

Conventionally, as a method of detecting the end point of dry etching using plasma, there is a method of detecting the end point using a change in the intensity of plasma emission.

[Problem to be solved by the invention]

The above-mentioned etching end point detection method using changes in plasma emission intensity is a method in which the plasma state during etching is observed by emission analysis and applied to detect the etching end point. Plasma light emission is a phenomenon caused by active gas species present in plasma, and research on plasma light emission has been developed as a plasma diagnostic technique using spectrum analysis.

The plasma emission spectrum depends on the reaction gas and reaction products in the plasma, and the etching reaction can be determined 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 detected. A method that utilizes this technique is a method for detecting the etching end point based on plasma emission intensity.

In order to detect the end point of etching using such a method, it is necessary to know the wavelength at which the emission intensity changes as etching progresses. That is, it is essential to consider in advance the emission wavelength that accurately reflects the fluctuations of active species in the plasma caused by the completion of etching, and this method lacks simplicity. There are also cases where no suitable plasma emission is present. Furthermore, in order to carry out this method, it is necessary to provide an etching device with a window for performing emission spectroscopy, and a spectroscopic device, a light-receiving element, and its driving circuit are also required, which are expensive.

[Means for Solving the Problems] The method of detecting the end point of dry etching using plasma according to the present invention detects the end point of etching from the potential change of the sample to be etched.

Unlike the conventional plasma emission method, which requires a wavelength for monitoring to be selected in advance, this potential measurement does not require such advance preparation and can be easily carried out in the same way as normal voltage measurement.

Further, the circuit for measuring the potential can be a rectifier circuit, which can separate and measure the DC component that is synthesized into a high frequency, and is inexpensive.

〔Example〕

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

FIG. 1 is a block diagram of a parallel plate type dry etching apparatus for implementing the present invention.

A cathode voltage measuring circuit 101 is connected to the connecting line between the high frequency power supply 106 and the matching circuit 105 and the cathode 102 to measure the potential of the etching sample. The cathode voltage measuring circuit 101 is shown as an example of a rectifier circuit consisting of a diode, a capacitor, and a coil, but any circuit that can measure a DC potential included in high frequencies may be used.

[Example 1] FIG. 2 shows an example of detecting the etching end point when etching the organic film under the three-layer resist using the above-mentioned dry etching apparatus equipped with the cathode potential measuring circuit. The three-layer resist used here includes an ordinary novolac resist with a thickness of 0.5 μm as the upper resist layer 203, and a coated oxide film 202 with a thickness of 1500 mm as the intermediate layer. The lower organic film 201 has a three-layer structure shown in FIG. 2(b), which is made of a novolak resist having a thickness of 2 μm and which has been baked at 250° C. for 90 minutes. The upper resist 203 is patterned by a phosphorography process, and the intermediate coated oxide film 202 is patterned by an etching process using the upper resist 203 as a mask.

Using this upper resist layer 203 and the intermediate layer as a mask,
Etching of the lower organic film 201 was performed.

Oxygen is used as the etching gas, and the flow rate is 20 sccm.
Etching was performed under the conditions of a pressure of 10 mTorr and a high frequency power of 600 W. Figures 2(b) and (c) show the changes in cathode potential after etching for 0 hours, 1 hour, and 2 hours in Figure 2(a) in this case.
, (d). The cathode potential increases after application of high frequency power and reaches approximately 250V. Thereafter, the voltage remains almost constant until the etching of the upper resist 203 is completed, and increases to about 340 V after the etching of the upper resist 203 is completed. When etching of the lower layer resist is completed, the voltage rises to about 400V, and the etching end point is detected.

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

[Example 2] FIG. 3 is an example of detecting the end point of etching by measuring cathode voltage when polysilicon etching is performed using the above-mentioned apparatus. The polysilicon was doped with phosphorus and etched to a thickness of 4000 mm. A resist with a thickness of 1.2 μm was used for the mask. Further, 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 sec and 30 sec.

Etching pressure is 3 OmTorr high frequency power 200W
Etching was carried out under these conditions. The cathode potential is
During etching, the voltage is constant at approximately 170V, and at the end point it is 160V.
The etching end point was detected.

〔Effect of the invention〕

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

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus for implementing the present invention in a parallel plate type dry etching apparatus, and FIGS. 2 and 3 are examples of detecting the etching end point obtained in organic film etching and polysilicon etching, respectively. , Figure 2(a)
and Fig. 3 are diagrams 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), respectively. 101... Cathode voltage measurement circuit, 102...
... Cathode, 103 ... Etching sample, 104
... Anode, 105 ... Matching circuit, 10
6... High frequency power supply, 107... Vacuum exhaust device, 108... Reaction gas introduction pipe, 201...
... lower layer organic film, 202 ... coated oxide film, 203 ... upper layer resist, 204 ...
·substrate. Agent Patent Attorney Uchihara Uchihara Figure 1 (b) (C) (Figure Z)

Claims (1)

[Claims] 1. In a dry etching process using plasma,
A method for detecting the end point of dry etching, characterized in that the end point of etching is detected based on a potential change of a sample to be etched. 2. A dry etching device using plasma is equipped with a capacitor, a coil, and a coil for measuring the DC potential of the sample to be etched.
2. The method for detecting the end point of dry etching according to claim 1, characterized in that a circuit including a rectifier, a resistor, etc. is provided, and the etching end point is detected using a change in potential of the circuit. 3. Claim No. 3, characterized in that a device is added to the etching apparatus to process the electric signal obtained from the measurement circuit mentioned above and automatically detect the end point of etching, and the etching apparatus is automatically controlled by the signal. The method for detecting the end point of dry etching according to item 2.