JPS63280421A - Method and apparatus for controlling working depth of dry etching - Google Patents

Abstract

PURPOSE:To eliminate the irregularity of working depths even if working conditions are varied by measuring the ion current value of reactive gas ions irradiated to a workpiece during dry etching working, and finishing the work when the accumulated current value arrives at a predetermined value. CONSTITUTION:When an etching work is started, an ion current starts flowing in a working vessel. The current value of the ion current is detected by a current detector 15, and transmitted to an an integrating device 16. The ion current value is integrated by an integrator 20. Accordingly, a signal corresponding to the accumulated value of the ion current values is presented at the output signal line 21 of the integrator 20. The amplitude of the signal increases as the work is continued. When the output signal of the integrator 20 is increased to coincide with the output signal of a reference voltage setter 24, i.e., the value of a predetermined reference signal, a comparator 23 is operated, and a comparison output signal is generated at the comparison output signal line 26. Therefore, the work end relay 29 of a relay driver 27 is operated to finish the etching work.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to dry etching used in the manufacture of semiconductor integrated circuits, and in particular, to maintaining the processing depth appropriately. The present invention relates to a control method and device for the same.

(Prior Art) In the manufacture of semiconductor devices and the like, it is necessary to perform microfabrication of several microns or less on the surface of a workpiece such as a semiconductor thin piece. Normally, such fine processing is carried out using
Dry etching as shown in Japanese Patent No. 4177 is used.

Dry etching is a process in which a magnetic field and microwaves are applied to a sealed container filled with a dilute reactive gas to generate plasma, ionize the reactive gas inside, and generate reactive gas ions. The beam is accelerated under a high electric field and irradiated onto the surface of a workpiece such as a semiconductor thin piece. The irradiated reactive gas ions cause a chemical reaction with the workpiece, such as a semiconductor, and remove the surface by etching.

By the way, when manufacturing semiconductor devices, for example, it is necessary to ensure that the amount removed by etching, that is, the processing depth from the surface of the workpiece, falls within a specified range. If the machining depth is even slightly excessive or insufficient, the resulting product will be defective.

Conventionally, when performing such dry etching, processing conditions such as the concentration of the reactive gas, the degree of vacuum in the processing container, the incident power of the microwave, and the strength of the magnetic field are kept constant. The etching process was performed for a certain period of time.

(Problem to be solved by the invention) However, it is extremely difficult to keep all machining conditions constant during machining, and when one machining condition changes for some reason, other machining conditions remain constant. If this is maintained, a difference will occur in the etching depth. Therefore, in the conventional method, the products obtained are often defective, which is a major cause of a decrease in yield.

The present invention has been made in view of these problems, and its purpose is to minimize variations in machining depth and maintain proper dry etching even when machining conditions change. It is to do so.

(Means for Solving the Problem) In order to achieve this object, the method of the present invention continuously detects the ion current value near the surface of the workpiece during dry etching processing, and detects the detected current value. The processing is completed when the cumulative current value reaches a predetermined value.

Further, the apparatus of the present invention for carrying out the method includes a sensor installed near the surface of the workpiece, a current detector that detects an ion current flowing through the sensor, and ions detected by the current detector. and an integrating device that integrates current values and generates a machining end signal when the cumulative current value reaches a predetermined value.

(Function) During the dry etching process, if various processing conditions such as the concentration of the reactive gas, the degree of vacuum in the processing container, the microwave incident power, and the magnetic field change, the ion current will be affected. The accumulation of these fluctuations appears in the cumulative value of the ion current value. Therefore, by stopping machining when the cumulative current value reaches a predetermined value as described above, even if machining conditions fluctuate during machining, they will eventually be leveled out. This makes it possible to maintain an appropriate machining depth.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

In the figures, FIG. 1 is an overall schematic diagram showing an example of a dry etching apparatus to which the control method according to the present invention is applied, and FIG.
The figure is an electrical circuit diagram of the main parts of a control device that implements the method.

As is clear from FIG. 1, this dry etching apparatus 1 includes a processing container 4 having a closed structure and consisting of an ion generating section 2 at the upper part and a main body section 3 at the lower part. This processing container 4
The interior of the chamber is maintained at a high vacuum by an appropriate vacuum pump (not shown). At the same time, a dilute reactive gas is introduced into the processing container 4 and distributed throughout the interior. A mounting stand 5 is provided inside the main body portion 3, and a workpiece 6 such as a semiconductor thin piece is placed on the mounting stand 5.

The ion generating section 2 and the main body section 3 of the processing container 4 have surrounding walls made of a conductive material, and are electrically insulated by an insulator 7 between them. Further, a net-like electrode 8 is attached to the opening of the main body part 3 that communicates with the ion generating part 2, and the electrode 8 is electrically connected to the surrounding wall of the main body part 3. The surrounding wall of the ion generating section 2 is connected to the high potential side of an external power source 9 that generates a high voltage, and the surrounding wall of the main body section 3 is connected to the low potential side of the external power source 9.

A coil 10 is installed around the outer periphery of the ion generating section 2 to generate a magnetic field therein. In addition, the ion generating section 2
There is a waveguide 1 on the top surface of the
1 is attached via an insulator 12. The microwave is generated within a microwave transmitter (not shown).

In the dry etching apparatus 1 configured as described above, when a voltage is applied to the coil 10, a magnetic field is generated inside the ion generating section 2.

Therefore, when microwaves are introduced into the ion generating section 2, due to the interaction between these magnetic fields and the microwaves,
Plasma is generated inside the ion generating section 2. and,
The reactive gas inside it becomes ionized.

At this time, the high voltage power supply 9 keeps the surrounding wall of the ion generating section 2 at a high potential, and the electrode 8 on the exit side thereof is kept at a low potential, so a high electric field is generated between them. Therefore, the reactive gas ions generated within the ion generating section 2 are accelerated and flow toward the electrode 8 side, pass through the mesh of the electrode 8, and flow into the main body section 3. The high-speed reactive gas ions then reach the workpiece 6, and the surface thereof is etched by chemical action.

The processing speed of such dry etching varies depending on the flow rate and density of reactive gas ions to be irradiated. On the other hand, when reactive gas ions flow in this way, an ion current is generated, and the ion current also has a magnitude corresponding to the flow rate, density, etc. of the ions. Therefore, in the present invention, the processing depth is controlled by detecting the ion current.

That is, a sensor 13 such as a Faraday cup is installed near the surface of the workpiece 6 to detect the current generated due to the flow of ions.

The ion current flowing through this sensor 13 is connected to the connecting wire 14a,
It is designed to be guided to a current detector 15 inserted between 14b and 14b. The ion current value detected by the current detector 15 is sent to an integration device 16. This integration device 16 always calculates the cumulative value of the ion current value during processing, with the value set at zero at the start of processing.

As the reactive gas ions flow toward the workpiece 6, an ionic current flows through the sensor 13 located near the surface of the workpiece 6. The ionic current is
The current flows from the current through the current detector 15 to the connection line 14b.

As shown in FIG. 2, the current detector 15 is formed by a precision resistor 17 and an amplifier 18, both ends of which are connected to connection lines 14a, 14b, respectively. Therefore, when a current flows through the connecting lines 14a and 14b, an electric signal proportional to the current value is generated between the signal lines 19a and 19b connected to both ends of the amplifier 18.

The signal is then sent to the integration device 16.

The integration device 16 includes an integrator 20.

Signal lines 19a and 19b of current detector 15 are connected to the input section of this integrator 20. Therefore, the ion current value detected by the current detector 15 is integrated by the integrator 20, and a signal corresponding to the integrated value, that is, the cumulative current value, is generated on the output signal line 21 of the integrator 2o. The initial value of this integrator 20 is reset to zero by an initialization relay 22 before starting machining. The initialization relay 22 is driven by the processing start control device of the etching apparatus 1.

An output signal line 21 of the integrator 20 is connected to one input of a comparator 23. The output signal line 25 of the reference voltage setter 24 is connected to the other input part of the comparator 23. The reference voltage setter 24 is constituted by a variable voltage setter, and is capable of setting a voltage value corresponding to a desired etching depth in advance. In the comparator 23, these integrators 20
The output signal of the integrator 20 is compared with the output signal of the reference voltage setter 24, and when the output signal of the integrator 20 is larger,
A comparison output signal is generated on the comparison output signal line 26.

This comparison output signal line 26 is connected to an input section of a relay driver 27. In the relay driver 27, upon receiving the input signal, the transistor 28 becomes conductive, and the machining completion relay 29 is driven. When this relay 29 is driven, the processing end control device of the etching apparatus 1 is activated to stop the processing. That is, the integration device 16 generates a machining end signal.

Next, the operation of the thus configured control device will be explained.

When the workpiece 6 is placed in the processing container 4 and a magnetic field and microwaves are generated, the etching process is started as described above. At this time, the processing start signal first resets the integrator 2o of the integration device 16, and then immediately starts the operation of the integrator 2o.

When the etching process is started, an ionic current begins to flow in the processing container 4. The current value of this ion current is detected by a current detector 15 and transmitted to an integration device 16. Then, the ion current value is integrated by an integrator 20. Therefore, a signal corresponding to the cumulative value of the ion current value appears on the output signal line 21 of the integrator 20. The magnitude of this signal increases as processing continues.

The output signal of the integrator 2o increases and the reference voltage setter 24
When the output signal coincides with the value of the predetermined reference signal, the comparator 23 operates and a comparison output signal is generated on the comparison output signal line 26. Therefore, the machining end relay 29 of the relay driver 27 is operated, and the etching process is completed.

In this way, a predetermined amount of reactive gas ions are supplied to the workpiece 6, and the surface thereof is etched to a desired depth.

By the way, if for some reason there is a change in the concentration of the reactive gas, the degree of vacuum in the processing container 4, the microwave incident power, or the strength of the magnetic field during this processing, the processing speed will increase or decrease. However, at that time, the ion current value also increases or decreases in response to an increase or decrease in the processing speed. Therefore, the rate of increase in the cumulative current value obtained by integrating the ion current values changes. That is, variations in machining speed are reflected in the output signal value of the integrator 20.

The cumulative current value is constantly calculated by the integrating device 16, and machining is stopped only when the cumulative current value reaches a value corresponding to the desired amount of machining. The processing end time will be adjusted. Therefore, over-machining or under-machining will not occur, and the machining will be performed to an appropriate depth.

In the above embodiments, the control method according to the present invention is implemented by an electronic control device as shown in FIG. 2, but the method according to the present invention may also be implemented by a computer program or a sequencer program. You can also do it.

FIG. 3 shows a flowchart for performing such program control.

As is clear from this figure, when control starts, the memory is first cleared. Then, the etching process begins. When processing starts, an ionic current is generated, and the current value is measured. The measured value is added to memory.

Next, it is determined whether the value in the memory has reached the reference current value. Since the memorized current value is small immediately after the start of processing, the ion current value is measured again after a short period of time has passed. Then, add the measured value to memory.

In this way, by adding the measured ion current values to the memory one after another, the values are added in the memory, and a cumulative current value is calculated. The cumulative current value increases as processing continues.

Then, when the stored cumulative current value reaches a predetermined reference current value, the machining is stopped and the control is also terminated.

Therefore, by performing program control based on this flowchart, the same effects as in the embodiment shown in FIG. 1.2 can be obtained. In the case of such program control, it is difficult to continuously detect the ion current value due to the limited memory capacity. By shortening the time, sufficiently precise control can be performed.

(Effects of the Invention) As is clear from the above description, according to the present invention, the ion current value of reactive gas ions irradiated to the workpiece is measured during dry etching processing, and the ion current value is Machining is terminated when the cumulative current value reaches a predetermined value, so the concentration of reactive gas,
Even if there are fluctuations in processing conditions such as the degree of vacuum in the processing container, the microwave incident power, or the strength of the magnetic field, the workpiece is irradiated with a predetermined amount of reactive gas ions, and its surface remains at a predetermined depth. It is etched. Therefore, the occurrence of defective products is reduced, yield is improved, and some variations in processing conditions are allowed, so processing costs are also reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an example of a dry etching apparatus to which the dry etching processing depth control method according to the present invention is applied, and FIG. 2 is a main part showing an example of a control device implementing the control method. FIG. 3 is a control flow diagram for implementing the method according to the invention. 1...Dry etching device 4...Processing container 6
...Workpiece 13...Sensor 15.
...Current detector 16... Integration device 20.
...Integrator 23...Comparator 24...
・Reference voltage setting device 27...Relay driver 29...Machining completion relay Fig. 1

Claims (3)

[Claims] (1) During dry etching, in which the surface of the workpiece is etched by irradiating the workpiece surface with reactive gas ions, after the start of processing, the ion current value in the vicinity of the surface of the workpiece is continuously detected, A dry etching process depth control method that calculates the cumulative value of the detected current value and ends the process when the cumulative current value reaches a predetermined value. (2) A sensor installed near the surface of the workpiece that is irradiated with reactive gas ions, a current detector that detects the ion current flowing through the sensor, and integration of the current value detected by the current detector. do,
A processing depth control device for dry etching, comprising: an integrating device that generates a processing end signal when the cumulative current value reaches a predetermined value. (3) The integration device includes an integrator that calculates a cumulative current value by integrating the ion current value detected by the current detector, and a cumulative current value that is calculated by comparing the cumulative current value with a predetermined value. The method according to claim 2, comprising: a comparator that generates a comparison output signal when the comparison output signal exceeds a predetermined value; and a relay driver that receives the comparison output signal and drives a machining completion relay. Dry etching processing depth control device.