JPS58130281A - Dry etching device - Google Patents

Abstract

PURPOSE:To enable detection of point of time of completion of etching by detecting pressure change in the reaction chamber keeping gas introduced to and discharged from the reaction chamber under constant condition. CONSTITUTION:The titled device consists of a gas introducing system that introduces reaction gas, a reaction chamber 22 connected to the gas introducing system, a measuring section that measures pressure in the chamber 22, and a gas flow controlling section that keeps the quantity of reaction gas introduced to and discharged from the chamber 22 constant. A pressure measuring element 23 is provided between the gas introducing system and the chamber 22 in above- mentioned gas flow controlling section, and the quantity of discharge gas is regulated by a valve 24. Pressure change in the reaction chamber 22 in which etching is performed is detected by a pressure measuring element 25 provided between the chamber 22 and the discharge system, and utilized for detecting termination.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry etching apparatus used for microfabrication of semiconductor devices, and particularly to an apparatus capable of detecting the end point of etching based on pressure changes.

Recently, with the miniaturization and higher density of semiconductor devices, the conventional wet etching method has been replaced by a dry etching method.

The most common types are R,1,E, (Reactive
This method is called "tone etching", and etching is performed using plasma and ions generated by high-frequency discharge.

Compared to conventional wet etching methods, these dry etching methods have a small selectivity ratio (etching speed of the object to be etched to the etching speed ratio of the substrate) to the substrate, which is about 1 to 10 at most. Damage to the base after etching is a problem. In addition, although dry etching was originally introduced for the purpose of fine etching, it is not always possible to etch the same pattern as the resist pattern, and it is not always possible to etch in the same way as the resist pattern. Sometimes they are etched. This phenomenon is particularly noticeable after the object to be etched has been etched in accordance with the resist pattern.

Therefore, in dry etching, it is necessary to accurately detect the end point of etching to prevent damage to the underlying layer and side etching as described above.

Until now, as end point detection methods, electrode voltage method, mass spectrometry, dual emission spectrometry, etc. are known and have been well studied.

However, it cannot be said that these detection methods have achieved sufficient results yet, and a method such as a combination of multiple end point detection methods is required for determination.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a dry etching apparatus capable of detecting the end of etching with good reproducibility from pressure changes in a reaction chamber in which dry etching is performed.

That is, the present invention detects the pressure change in the reaction chamber corresponding to the progress of etching while keeping the gas introduced into and discharged from the reaction chamber constant, and detects the end point of etching.

Hereinafter, the configuration of the present invention will be explained with reference to the drawings.

Figure 1 shows R, 1, E, CCX introduced into the reaction chamber of the device.
4 shows the pressure change in the reaction chamber when dry etching the Afi alloy with a constant gas amount. In the figure, when high frequency electrons are applied at 11 hours, the pressure increases and then gradually decreases. At time t2, the pressure drops rapidly. This large change in pressure at time t2 corresponds to the start of etching of the A2 alloy film, as determined by spectroscopic analysis and electrode voltage measurements. Thereafter, the pressure does not change much, but gradually increases as the etching progresses. At time t3, the pressure increase saturates, which corresponds to the endpoint in other endpoint detection methods. At time t4, the high frequency power was turned off, so the pressure was slowly approaching its initial value. In this way, if the flow rate of gas introduced into and exhausted from the reaction chamber is kept constant, a pressure change of 5 bases can be obtained with good reproducibility, so the end point time t3 can be estimated from the pressure change, and the method of measuring the pressure change can also be used to detect the end point. It can be used as a method.

However, this method of detecting the end point by pressure measurement requires that the amount of gas introduced and the amount of gas exhausted be kept constant before, during and after etching. here,
In order to control the flow rate of gas introduced into the reaction chamber, it is possible to measure the pressure inside the reaction chamber and maintain a constant flow rate passing through the reaction chamber. Change is impossible. In other words, since the gas flow rate introduced into the reaction chamber is independently controlled by the mass flow controller, when there is no high-frequency discharge, the exhaust volume can be kept constant by keeping the pressure inside the reaction chamber constant. Like during high frequency discharge,
If there are differences in the number and energy of gas component particles, the amount of gas introduced and exhausted will change even if the pressure in the reaction chamber is kept constant.

Hereinafter, an embodiment according to the present invention will be described in which the gas introduction and discharge into the reaction chamber are made constant.

(Example 1) FIG. 2 shows an example in which a pressure measuring element for controlling gas introduction is provided between the gas introduction system and the reaction chamber. In the figure, reference numeral 21 denotes a mass 70-controller for controlling the amount of etching gas introduced.

Between the reaction chamber 22 and the mass flow controller 21,
A pressure measuring element 23 for adjusting the displacement is provided to control the throttle valve 24.

A pressure probe 26 used for end point detection is provided between the reaction chamber 22 and the throttle valve 240, and its signal is connected to the control section 26 and pen recorder 27.

Next, the operation of this etching apparatus will be explained.

Etching gas is controlled by a mass flow controller 21 and introduced into the reaction chamber 22 . The displacement amount is adjusted by opening and closing the throttle valve 24 in accordance with the increase or decrease in the pressure value measured by a pressure measuring element 23 provided between the gas introduction system and the reaction chamber 22. Before the high-frequency discharge, the pressure measuring element 23 on the 7 Beno F flow side of the reaction chamber 22 and the pressure measuring element 25 on the downstream side
are in a proportional relationship, but under high frequency discharge, the two are no longer in a corresponding relationship.

The pressure change in the reaction chamber 22 corresponding to etching is
2 and the exhaust system. The pressure value from the pressure probe 26 is input to the control unit 26, recorded in the pen recorder 27, and simultaneously used for end point detection.

In the apparatus according to this embodiment, the amount of gas introduced into and exhausted from the reaction chamber is related to the presence or absence of high-frequency discharge and can be kept constant, so the pressure inside the reaction chamber, which changes in response to etching, can be accurately controlled. It can be taken out.

(Embodiment 2) FIG. 3 shows an example of extracting the pressure difference between the gas introduction system and the reaction chamber and between the reaction chamber and the exhaust system. In the figure, pressure measuring elements 32 and 33 are provided at both ends of a reaction chamber 31. Once the flow rate is maintained at a constant level by the gas introduction controller 34, the throttle valve 36 is adjusted to maintain the constant flow rate before applying high frequency discharge and etching. Once adjusted, the throttle valve 35 is fixed. When etching starts, the output difference between the measuring tip 32 and the measuring tip 33 is inputted to the control section 36, and this result is sent to the recorder 3.
7, and the end point is detected from this result. This configuration makes it possible to cancel out slight changes in the gas introduction amount, leakage amount, and exhaust amount by using two probes 32 and 33. Note that the pressure measuring element 32 on the gas introduction side hardly shows any change in pressure even during etching.

As mentioned above, the difference between the two pressure probes is detected while the gas introduction and exhaust amount is kept constant, so even if the gas introduction amount, leakage amount, and exhaust amount change, the end point detection will not be affected. There are few problems.

(Example 3) In another example, the pressure difference before and after the reaction chamber is measured with one pressure probe and used to detect the end point, and this example is shown in FIG. In the figure, the pressure difference before and after the reaction chamber 41 is detected by a pressure measuring element 42 of 9 degrees. Since this pressure measuring element 42 outputs the pressure difference on both sides of the reaction chamber 41, even a slight pressure difference can be measured without being affected by temperature or the like.

However, since it is structurally weak against large pressure differences, it is protected by attaching opening/closing pulp 43 and 44 to both ends. A pressure probe 46 attached to the reaction chamber 41 is used to open and close the opening/closing pulps 43 and 44.

When the pressure exceeds a certain level, the opening/closing pulps 43 and 44 close.
It will be done. The pressure probe 44 is also used for adjusting and controlling the throttle valve 46 before discharge and etching. This throttle valve 46 is not controlled during etching. The gas introduction controller 47 is controlled to introduce a certain amount of gas into the reaction chamber 41. As mentioned above, with this configuration, pressure changes due to small changes in flow rate, leakage amount, and displacement amount are not included in the pressure difference signal of the probe 42. Here, the output of the pressure probe 42 is controlled by the control section 48.
The result is recorded in the recorder 49.

(Example 4) 1o - The example shown in Figure 6 measures the pressure in a constant chamber 611 placed in parallel with the reaction chamber, and uses this result to keep the flow rate of gas introduced into and discharged from the reaction chamber constant. It is.

In the figure, a measurement chamber 53 having a pressure probe 52 is provided in parallel with a reaction chamber 61. The gas flow rate introduced into the measurement chamber 53 is 1/n of the control value of the gas flow rate controller 540 of the reaction chamber 61 (n is an arbitrary value - set and fixed in advance. For example, the volume ratio of the reaction chamber 51 and the measurement chamber 56 is one guideline.) is controlled by the gas flow rate controller 66. The pressure probe 56 attached to the reaction chamber 51 is not used to control the exhaust flow rate, but is used only for the purpose of detecting pressure changes within the reaction chamber 61. pressure 1
111 constantor 62 outputs a preset pressure difference and opens and closes throttle valves 57 and 58. At this time, a signal multiplied by 1/m is input in advance to the throttle valve 68 on the measurement chamber 53 side so that the pressures in the measurement chamber 63 and reaction chamber 51 are equalized.

This value of m is unique to the device, and once determined, there is no need to change it. This operation is necessary to control the amount of exhaust gas 11 in the reaction chamber 51 using the pressure in the measurement chamber 63.

With the above configuration, it is possible to obtain a pressure signal from the pressure probe 63 of the measurement chamber 63 for comparison, which is completely independent of the etching reaction and high-frequency discharge, and the throttle valve 58 is controlled by this signal to control the displacement of the reaction chamber 51. It is something to control.

As described above, in the dry etching apparatus according to the present invention, the amount of gas introduced into and exhausted from the reaction chamber can be kept constant regardless of the presence or absence of high-frequency discharge. can be extracted with high precision.

(Example 5) In each of the above examples, the gas flow rate was controlled to be constant during etching, but if the gas flow rate was set to be constant before the start of etching, it would be possible to The pressure in the reaction chamber before and after etching can be kept constant without having to adjust the gas exhaust. However, this method results in some loss of accuracy.

(Example 6) FIG. 6 shows R, 1. E shows an example of the device. In the same figure, 61 is gas introduction 1], CF
CF CCf12F2. CCR4, BC43゜4
'38' NF3. SF6 etc.) flows into the etching chamber 62 while being kept at a constant amount by a flow controller. The inlet to the etching chamber 62 has a large number of pipes 63.
It is designed to allow gas to flow uniformly over the entire surface of the wafer. 64 is an electrode connected to a high frequency power source 66, on which the wafer is placed. Note that the pressure in the etching chamber 62 is measured by a capacitance manometer 66. Reference numeral 67 is an adjustment chamber that controls the exhaust amount by adjusting the pressure and flow rate. Reference numeral 68 is a flow meter, which is used to measure the amount flowing through the adjustment chamber 67. 69 is a throttle valve that connects the etching chamber 62 and the adjustment chamber 67;
is a throttle valve that connects the adjustment chamber 6a and the exhaust pump. The throttle valve 69 is mainly operated manually and is kept constant at 13" during etching. The throttle valve 7o is controlled by the output from a flow meter 68 or a capacitance manometer 71. 72 is connected to the exhaust system. The exhaust pump is a mechanical booster pump.

A regular turbo pump or the like is used. The following three modes can be selected for controlling the throttle valve 70.

The first method is to use only a flow meter for control, in which the exhaust flow rate is the detected quantity and the opening/closing angle of the throttle valve is the controlled quantity.

For example, if the exhaust flow rate is set to a constant value, the throttle valve will rotate in the closing direction if the exhaust flow rate is greater than that flow rate value. If there is less, the throttle valve can be opened. The second mode is a method in which only the vacuum degree needle is used for control, and the degree of vacuum in the adjustment chamber 67 is used as the detected amount, and the opening/closing angle of the throttle valve 7° is used as the controlled amount. There are two methods for setting the degree of vacuum: one is to set it to a constant value in advance, and the other is to set it so that the difference in the degree of vacuum between the etching chamber 62 and the inside of the etching chamber is always zero. In the method of setting the pressure to a constant value, the throttle pulp 70 is quickly opened and closed so that the degree of vacuum in the adjustment chamber 67 becomes constant, but in the method of setting the pressure difference with the etching chamber 62 to zero, it is not set manually in advance. The throttle valve is opened or closed only if the mismatch occurs for a time greater than or equal to the pressure time delay caused by the throttle valve 69. In the third mode, both the degree of vacuum and the exhaust flow rate are detected quantities, and the controlled quantity is the opening and closing of the throttle valve. In the first stage, the vacuum gauge 7
Determine the exhaust flow rate value so that 1 becomes the set value. In the second stage, the throttle valve 70 is adjusted so that the exhaust flow rate reaches the set value.
control. However, if the degree of vacuum in the adjustment chamber 67 changes from the initial setting beyond the change range of the degree of vacuum due to etching, the exhaust flow rate is reset so as to maintain the initial degree of vacuum.

As described above, with the configuration according to this embodiment, it is possible to grasp the pressure change inside the etching chamber while independently setting the gas inflow amount and the gas exhaust amount. This device can accurately measure the increase in particle temperature within the system due to the generation of ions and plasma by high-frequency discharge, and the decrease in the particle temperature within the system due to the disappearance of ions and plasma by an etching reaction.

As described above, according to the present invention, changes in the pressure in the etching reaction chamber can be detected with good reproducibility, so that the end of etching can be easily determined.

[Brief explanation of the drawing]

FIG. 1 shows R according to the present invention, 1. E is a diagram showing the pressure change in the reaction chamber of the apparatus, FIG. 2 is a configuration diagram of the first embodiment of the present invention in which a pressure measuring element is provided between the gas introduction system and the reaction chamber, and FIG. 3 is a diagram of the first embodiment of the present invention. FIG. 4 is a configuration diagram in which pressure probes are provided before and after the reaction chamber in the second embodiment, and FIG. 6th
The figure is a configuration diagram of a fourth embodiment of the present invention in which pressure is measured in a measurement chamber juxtaposed with a reaction chamber, and FIG. 6 is a configuration diagram of a sixth embodiment of the present invention equipped with a flow meter and a vacuum needle. Show the diagram. 23.32, 43, 54.55... Pressure measuring element on gas inlet side, 22.31.41.51.62 Etching chamber, 25.33.44.57.58... Pressure measurement on gas discharge side Child, 53...Pressure measurement chamber.

Claims (4)

[Claims] (1) A gas introduction part into which a reaction gas is introduced, and a reaction chamber connected to this gas introduction part and which performs an etching process;
The device is equipped with a measuring section for measuring the pressure inside the reaction chamber, a gas exhaust section connected to the reaction chamber, and a gas flow control section for keeping constant the amount of reaction gas introduced into and discharged from the reaction chamber. Dry etching equipment with special features. (2) The dry etching apparatus according to claim 1, wherein the gas flow rate control section includes a pressure measuring element provided between the gas introduction section and the reaction chamber. (3) The dry etching apparatus according to claim 2, wherein the measuring section is provided between the exhaust section and the reaction chamber. (4) The dry etching apparatus according to claim 1, wherein the gas flow rate control part consists of a measurement chamber juxtaposed to the reaction chamber and a probe for measuring the pressure in the measurement chamber. .