JPH0214518A - Detection of etching end point - Google Patents

Abstract

PURPOSE:To detect an etching end point by measuring a parameter to be changed in order to control a constant pressure. CONSTITUTION:A measured value by a pressure gauge 3 used to measure a pressure inside a chamber 2 is taken in an automatic pressure control device 5; an opening and shutting degree of a butterfly valve 4 is changed by an output signal from the automatic pressure control device 5; the pressure of the chamber 2 is kept constant. A detection device 6 used to detect the opening and shutting degree of the butterfly valve (variable conductance valve) as an analog electric signal is installed; the analog electric signal is converted into a digital signal by using an A/D converter 7; the signal is read out by a computer 8. Since a change in the opening and shutting degree of the butterfly valve at the time near an etching end point becomes steep, the computer 8 processes the digital electric signal, detects a peak of its differential value and judge the end point.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for detecting the end point of etching using a dry etching apparatus used for manufacturing ICs, LSIs, etc.

(Prior art) Conventionally, methods for detecting the end point in dry etching include: (1) I'A simple method
of end-poir+L determi
-natton for plasma etchin
g JM 几, 1Htch+aan etal, J.
Vac, Sci, Technol,, Vol, 1? , N
o, 6 Nov, / Dec1980 PP, 1378~
1381 (2) “Submicron lithography” supervised by Susumu Namba
There are some disclosed in Science Forum PP, 362-363, and they are shown below.

■Emission spectroscopy: Uses changes in the emission spectrum of plasma.

■Reflected light analysis method uses changes in plasma reflected from two substrates.

■Gas analysis method: Analyze gas using a quadrupole gas analyzer and use changes in its composition.

(2) Impedance measurement method: Using changes in the self-bias voltage Voc (direct 2it voltage) on the cathode.

■Using pressure measurement method 2 and changes in response pressure.

The pressure measurement method (pressure change method), which is the closest technology to the present invention, will be described below.

The pressure measurement method is disclosed in the above document (1). This pressure measurement method is a method in which the indicated value of the pressure gauge changes before and after the end point of etching, and this change is used to detect the end point of etching.

A. In the constant pressure control system: (1) In the case of resist etching using OX gas, the gas supply amount (etchant consumption) is small during etching and large near the end point. Also, the exhaust amount (product N)
On the contrary, is large during etching and small near the end point.

(2) In the case of polysilicon etching with cz2 gas, the gas supply amount (etchant consumption is large during etching and small near the end point. Also, exhaust!!l (amount of product) is, conversely, It is small during etching, and large near the end point.

In addition, in the constant pressure control method, there are a method of changing the gas flow rate and a method of changing the displacement amount. When controlling the gas supply amount, the displacement amount is kept constant, and conversely, the displacement amount is controlled B. In some cases, the gas supply amount should be kept constant.

B. When the constant pressure control method is not used, (1) In the case of resist etching with 0 g gas, the etching is large during etching and small near the end point.

(2) C1, case of polysilicon etching with gas It is small during etching, and large near the end point.

In this way, the presence or absence of the object to be etched affects the pressure and can be used to detect the end point.

Figure 5 shows the conventional pressure measurement method A for detecting the end point of photoresist.
An example is shown in which the method B and emission spectrometry are used together.

0 with barrel type etching equipment that does not have constant pressure control.
The photoresist on the glass substrate was removed under the conditions of □, 140SCCM, and 300-. As is clear from Figure 0, in which a Villany vacuum gauge is used, both the pressure measurement method and the emission spectrometry method show that the visual just-enching method is approximately defeated.

(Problems to be Solved by the Invention) However, the end point detection method described above has the following drawbacks and is not technically satisfactory. That is, (1) Emission spectrometry, gas analysis: requires expensive analysis equipment.

(2) Reflected light analysis method: Targets such as Cr are extremely limited.

(3) Impedance measurement method: small change in Voc,
Detection is uncertain.

(4) Pressure measurement method: This method cannot be used with dry etching equipment that performs constant pressure control because the pressure, which is an indicator for end point detection, does not change. It is an object of the present invention to provide a simple and highly versatile method for detecting the end point of etching by eliminating the disadvantages of limitation of target, uncertainty, and inability to apply constant pressure control.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method for detecting the end point of etching using a dry etching apparatus that performs constant pressure control. The measured value is converted from an analog signal to a digital signal, the converted digital signal is read into a computer, and the digital signal is monitored to detect the end point of etching.

(Function) According to the present invention, in a dry etching apparatus that performs constant pressure control, the gas flow rate or displacement amount, which is a parameter to be changed in order to perform constant pressure control, is measured, and these measured values are converted from an analog signal to a digital signal. The converted digital signal is read into a computer, the digital signal is monitored, and, for example, the peak of its differential value is detected to detect the end point of etching.

Whether to monitor the gas flow rate or the exhaust volume is determined by monitoring the gas flow rate if the parameter to be changed for constant pressure control is the gas flow rate, or monitoring the exhaust volume if that parameter is the exhaust volume. Select.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an etching end point detection system showing an embodiment of the present invention.

In this figure, a parallel plate type dry etching Wtl is equipped with a chamber 2, and the pressure inside the chamber 2 is controlled to be kept constant during dry etching. For this purpose, the pressure gauge 3 that measures the pressure inside the chamber 2 and the measured value by the pressure gauge are input into the automatic pressure control device 5, and the degree of opening and closing of the butterfly valve 4 is changed according to the output signal from the automatic pressure control device 5. By doing so, the pressure in the chamber 2 is kept constant.

In this embodiment, the etching end point is detected using the displacement as a parameter, and a detection device 6 is provided to detect the opening/closing degree of the butterfly valve (variable conductance pulp) as an analog electrical signal. The electrical signal is converted into a digital signal by an A/D converter 7, and the digital signal is read into a computer 8.

The computer 8 processes the digital electrical signal and determines the end point by detecting the peak of its differential value.

Therefore, a detection device 6 that detects the opening/closing degree of the butterfly valve as an analog electrical signal using FIGS. 2 and 3.
will be explained below.

FIG. 2 is a block diagram of a detection device for detecting the opening/closing degree signal of a butterfly valve.
The disc 19 is driven by the motor 2o.
By changing the angle of the ring 18 (the degree of opening and closing of the butterfly valve), the conductance is changed. Therefore, in the present invention, a drive transfer shaft 22 is attached to the drive shaft 21 of the disc 19, and the movement of the drive shaft 21 (the opening/closing degree of the butterfly valve) is transmitted to the driven transfer shaft 23 by the belt 24. Since the driven wheel 23 is directly connected to the variable resistor 25, the degree of opening and closing of the butterfly valve is converted into the resistance value of the variable resistor 25.

This variable resistor 25 is incorporated into an analog electrical signal generation circuit, as shown in FIG. That is, this analog electrical signal generation circuit includes a constant voltage power supply 26 and a fixed resistor R.
827, consisting of variable resistance Rv 28, fixed 1 resistance L2
7> Variable resistor Rv Set as 28, and set variable resistor 2
5, the variable resistor Rv 28 changes, and an output voltage v0 proportional to the value of the variable resistor can be taken out as an output signal representing the degree of opening and closing of the butterfly valve.

Actually, as shown in FIG. 1, the novolac photoresist 10 coated on the Si wafer 9 is used as the target for detecting the end point of etching, and the Si wafer 9 coated with the novolac photoresist 10 is placed on the etching electrode 1llO. ,0. Flowing at 50SCCM, the pressure was increased to 100
The automatic pressure controller, 5, was set to maintain mTorr, and 200 W of high frequency power was applied.

FIG. 4 shows the relationship between the change in the degree of opening and closing of the butterfly valve during etching and the end point of etching as determined by visual inspection.

As is clear from this figure, novolak resist 10
As begins to disappear, the opening of the butterfly valve begins to increase, and at the end point it begins to saturate.

This change in the degree of opening and closing of the butterfly valve is input into the computer 8 as described above, and the signal corresponding to the degree of opening and closing of the butterfly valve is monitored. When the differential value shows a peak, this is detected and the end point is determined. Make a judgment.

That is, since the change in the degree of opening and closing of the butterfly valve at time T near the end point of etching becomes steep, this is detected as the peak of the differential value to determine the end point.

By measuring the degree of opening and closing of the butterfly valve 4 in this manner, the end point of etching can be determined.

Next, a case will be described in which the end point of etching is determined by measuring the gas flow rate.

FIG. 6 is a block diagram of an end point detection system showing another embodiment of the present invention.

In the figure, a barrel type dry etching device 30 has a chamber 31 as a mechanism to keep the pressure constant during etching.
It is equipped with a pressure gauge 32 that measures the pressure of the chamber 31, and an automatic pressure control device 34 that uses the measured value of the pressure gauge 32 to control a mass flow controller 33 and keeps the pressure of the chamber 31 constant by changing the gas flow rate. are doing.

The barrel type dry etching apparatus 30 also includes an A/D converter that converts the measured gas flow rate (analog electrical signal) output from the mass flow controller 33 into a digital electrical signal in order to detect the end point of etching. 35, and a combiator 3G that processes the digital electrical signal and detects the end point by detecting the peak of its differential value. A novolak photoresist 38 coated on a Si wafer 37 was used as a target for detecting the end point of etching. A Si wafer 37 coated with a novolac photoresist 38 is placed in the chamber 31, the automatic pressure controller 34 is set to maintain the pressure at I Torr with 0□ gas flowing, and the high frequency power is set at 50 Torr.
0W was applied. The measured value of increase/decrease in the 0□ gas flow rate after application of high frequency power was processed by the computer 36 to determine the end point of etching.

In addition, in the combiator 8, as a means for determining the end point of etching, although not shown, the amount of change in the opening/closing degree of the butterfly valve and the end point of etching are stored in advance in a ROM (not shown) controlled by a CPU (central processing unit). A correspondence table is stored for each etching target, and the amount of change in the output signal of the opening/closing degree of the butterfly valve in real time during actual etching is stored in a RAM (not shown), and the data in the ROM is read out. The end point of etching can be determined by comparing the two.

Furthermore, the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, in a dry etching apparatus that performs constant pressure control, the end point of etching is determined by measuring the parameters changed for constant pressure control. Since it has been made possible to detect this, in dry etching equipment that performs constant pressure control,
The end point of etching can be detected with a simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an etching holly point drainage system showing an embodiment of the present invention, Fig. 2 is a configuration diagram of a butterfly valve opening/closing degree signal detection device, Fig. 3 is an analog electric signal generation circuit diagram, and Fig. 4 The figure shows the relationship between the change in the degree of opening and closing of the butterfly valve during etching and the visually observed end point of etching. Figure 5 shows an example in which pressure measurement method A and emission spectrometry method B are used in combination to detect the end point of conventional photoresist. Figure shown, No. 6
The figure is a configuration diagram of an end point detection system showing another embodiment of the present invention. 1... Parallel plate type dry etching device, 2.31.
...Chamber, 3, 32...Pressure gauge, 4...Butterfly valve, 5,34...Automatic pressure control device, 6...
・Detection device, 7.35...A/D converter, 8,3
6... Computer, 9,37... St wafer, 1
0.38...Novolak photoresist, 11...
Etching electrode, 18...ring, 19...disk,
20... Motor, 21... Drive shaft, 22... Drive roller, 23... Driven transfer, 24... Belt, 25...
... Variable resistor, 30... Barrel type dry etching device, 33... Mass flow controller. Patent applicant Oki Electric Industry Co., Ltd.

Claims (4)

[Claims] (1) In an etching end point detection method using a dry etching apparatus that performs constant pressure control, (a) the value of a parameter to be changed in order to perform constant pressure control is measured, and (b) the measured value is converted from an analog signal to a digital signal. (c) reading the converted digital signal into a computer; (d) monitoring the digital signal to detect the end point of etching. (2) The etching end point detection method according to claim 1, characterized in that an exhaust amount is used as the parameter. (3) The etching end point detection method according to claim 1, characterized in that a gas flow rate is used as the parameter. (4) detecting the peak of the differential value of the digital signal;
2. The etching end point detection method according to claim 1, wherein the etching end point is detected.