JPH03230523A - Dry etching method and equipment - Google Patents

Abstract

PURPOSE:To highly precisely control an etching shape with excellent reproducibility by combining, in order, a discharging state under such conditions as to allow stable start of discharge and a discharging state under such conditions as to allow stable continuation of discharge. CONSTITUTION:When a switch of a controlling circuit 6 is turned on in the state that etching gas is introduced at a speed to obtain a desired pressure inside a chamber 1, an electromagnetic valve 3 for exhausting is firstly closed. The pressure inside the chamber 1 is gradually increased, and a signal of the pressure in the chamber 1 is transmitted to the controlling circuit 6 from a vacuum gauge 4. The controlling circuit 6 receives said signal, drives a high frequency power supply so as to obtain the previously set output power, and simultaneously opens the valve 3. Discharge is quickly started; the pressure inside the chamber 1 is returned to a specified value; etching is progressed. Hence a processing shape can highly precisely be controlled, and excellent dry etching performance can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a dry etching method and apparatus for etching a substrate by performing discharge in a chamber in the manufacturing process of semiconductor integrated circuits.

[Conventional technology]

Regarding the etching gas used in conventional dry etching, chlorine-based gas is said to be effective when etching GaAs substrates, but the etch rate is very slow at 0.1 μm per minute for InP substrates. However, since the sublimation temperatures of InBr and InC1 are almost the same, it has been found that if bromine gas, which is also a halogen-based material, is used, etching can be performed at an order of magnitude faster rate than when chlorine gas is used.

FIG. 4 shows a schematic diagram of a conventional dry etching apparatus.

According to the conventional dry enching method, it is very difficult to adjust the flow rate of the enching gas introduced into the chamber half using a mass flow controller if the enching gas is bromine, which is highly corrosive. be.

Therefore, the flow rate of the etching gas is fixed. Subsequently, the output of the high frequency power source 8 and the etching time are determined in advance according to the desired etching shape. As for the operating procedure, first, the sample substrate 12 is set in the chamber 7 and the chamber 7 is evacuated.

Next, etching gas is introduced into the channel half, and discharge is started under predetermined conditions to perform etching.

[Problems to be Solved by the Invention] Although it is extremely difficult to control the etching shape due to the receding effect of the mask, it is possible to control the etching shape by realizing a competitive state in which the chemical etching effect and the physical etching effect are in an appropriate ratio. It is thought that it will become easier. However, when using bromine gas, the internal pressure to achieve the optimal etching shape must be lower than the pressure required to start the discharge, but in the conventional configuration, the internal pressure at the start of the discharge and the internal pressure during etching must be lower than the pressure required to start the discharge. cannot be controlled separately.

Therefore, if etching is performed at a high internal pressure at the start of discharge, the effect of chemical etching will increase, making it impossible to obtain the desired shape. Conversely, discharge cannot occur at an internal pressure that allows the optimal etching shape to be obtained. In particular, when etching an InP substrate using a bromine gas, the etching rate is high, so it is necessary to control the etching time in units of several seconds. This poses a problem in that it is quite difficult to control the etching shape with high precision due to instability at the start of discharge.

An object of the present invention is to provide a dry etching method and apparatus that can control the etched shape with high precision and good reproducibility.

[Failure to solve the problem]

The dry etching method and apparatus of the present invention control the discharge state by changing either the chamber internal pressure or the high-frequency power output, so that the discharge state 1 is set under conditions in which discharge can be stably started; The present invention is characterized in that dry enching is performed by sequentially combining discharge state 2 under conditions in which discharge can be continued stably.

[Effect]

According to the configuration of the present invention, the discharge state is controlled by changing either the chamber internal pressure or the high-frequency power output, and the discharge state B1 is set under conditions that allow stable discharge to start, and the discharge is stabilized. Discharge state 2 under conditions that can continue to
By combining these in sequence, discharge can be stably started and the etched shape can be controlled with high precision and good reproducibility.

[Example] An example of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 2 shows the characteristics regarding the pressure inside the chamber and the discharge current at a certain constant power supply voltage. That is, if the chamber internal pressure is P2 or less, it is quite difficult to start discharge, and if the chamber internal pressure is P2 or more, discharge can be easily started. Moreover, once the discharge is started, the discharge state can be maintained as long as the chamber internal pressure does not fall below P1. For example, assume that the conditions necessary to obtain a desired etched shape are the chamber pressure and output indicated by point A. Discharge cannot be started under this condition. Therefore, first, the pressure inside the chamber is maintained at 12 or more, and discharge is started in that state. Subsequently, the pressure is reduced to the point indicated by point A, and etching is performed for an arbitrary period of time.

FIG. 1 is a schematic diagram of the apparatus in this embodiment. The operating procedure when using this device will be explained. This device consists of a chamber 1, a high frequency power source 2 for discharging, an exhaust electromagnetic valve 3 for controlling the internal pressure of the chamber 1, and a chamber 1 for controlling the internal pressure. A vacuum gauge 4 for measurement, and a solenoid valve 3 for exhaust and a high frequency electric a2 based on a signal from the vacuum gauge 4.
It is composed of a control circuit 6 that can control.

In the initial state, the exhaust electromagnetic valve 3 is open, and etching gas is introduced at a rate such that the chamber 1 reaches a desired pressure. When the control circuit 6 is turned on in this state, the exhaust solenoid valve 3 is first closed. Then, the pressure inside the chamber 1 gradually increases, and a signal is transmitted from the vacuum gauge 4 to the control circuit 6 indicating that the pressure inside the chamber 1 is 22 or more as shown in FIG. When the control circuit 6 receives the signal, it drives the high frequency power source 2 with a preset output and simultaneously opens the exhaust electromagnetic valve 3. The discharge starts immediately, and then the pressure inside the chamber 1 reaches the second level.
Etching is performed by returning the pressure to the point shown in the figure.

Actually, the internal pressure was raised to 15 mTorr at the start of discharge, and then lowered to 3 mTorr for etching.

FIG. 3 shows a case where the side surface is etched in a vertical shape. Figure 3 (a) shows when discharging is performed with the internal pressure at 15 mTorr, and Figure 3 (b) shows when the internal pressure is reduced to 15 mTorr.
This is a case in which discharge was started by raising the torque to r and then lowering it to 3 mTorr, and it was clearly possible to realize a more accurate etched shape in the latter case.

In this embodiment, the discharge state is controlled by changing the pressure inside the chamber 1, but the same effect can be obtained even if the discharge state is controlled by changing the output of the high frequency type tA2.

〔Effect of the invention〕

As described above, according to the dry etching method and apparatus of the present invention, by sequentially combining the discharge state B1 under the conditions in which the discharge can be started stably and the discharge state 2 under the conditions in which the discharge can be continued stably, , it is possible to eliminate the instability of the discharge state at the start of discharge, and to realize excellent dry etching performance in which the machined shape can be controlled with high precision.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a dry etching apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram regarding the pressure inside the chamber and the discharge current at a certain power supply voltage, and FIG. Etching shape in the example,
FIG. 4 is a schematic diagram of a conventional dry etching apparatus. 1.7...Chamber, 2.8...High frequency power supply, 3
・・Exhaust solenoid valve, 6・control circuit/6

Claims (2)

[Claims] (1) In a dry etching method in which an etching gas is introduced into a vacuum chamber and a discharge is generated using a high frequency power source to physically or chemically etch the sample substrate,
By controlling the discharge state by changing either the chamber pressure or the high-frequency power output, discharge state 1 is a condition in which discharge can be started stably, and discharge condition 1 is a condition in which discharge can be stably continued. A dry etching method in which etching is performed in combination with state 2. (2) In a dry etching device that introduces an etching gas into a vacuum chamber and uses a high frequency power source to generate discharge to physically or chemically etch the sample substrate,
By controlling the discharge state by changing either the chamber pressure or the high-frequency power output, discharge state 1 is a condition in which discharge can be started stably, and discharge condition 1 is a condition in which discharge can be stably continued. A dry etching apparatus characterized by comprising means for sequentially combining state 2.