JPH0587943U - End point detector for dry etching equipment - Google Patents

Abstract

(57) [Summary] [Purpose] The light intensity is automatically adjusted to shorten the light intensity adjustment time. A light amount adjusting plate 4 having a light passage hole 19 for continuously changing the light amount according to a rotational displacement is installed in the light amount adjusting section A, and an output signal of the light intensity-electrical signal converting element 7 is a set output of a setter 12. The light amount adjusting plate 4 to the motor 9 so that
The automatic control system 8 for controlling the rotation is provided, and the output of the light intensity-electrical signal conversion element 7 is switched from the automatic control system 8 to the electric signal processing device 16 by the changeover switch 13 when they match.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an end point detector that detects an etching end point of a dry etching apparatus which is one of semiconductor manufacturing apparatuses.

[0002]

[Prior Art]

 FIG. 4 is a diagram illustrating the configuration of an example of a conventional end point detector. In this conventional example, as shown in FIG. 4, the light quantity of the plasma light of the dry etching apparatus 1 is adjusted by the light quantity adjusting section A, and only the light of a specific wavelength is extracted by the optical filter 6 from the light quantity adjusted light.

Since the intensity of the light of the specific wavelength is converted into an electric signal by the photomultiplier tube 7, the electric signal is input to the microprocessor 16 to obtain the change amount of the light intensity and the etching end point is determined. However, in the light quantity adjustment A, one of a plurality of perforated plates 20A to 20D having light passage holes 19 having different diameters is artificially selected and set, and the light quantity introduced into the photomultiplier tube 7 becomes appropriate. As described above, these perforated plates 20A to 20D are artificially converted.

The reason for converting the perforated plates 20A to 20D will be described. FIG. 5 is a diagram showing the relationship between the intensity (light energy) of light input to the photomultiplier tube and the output current of the photomultiplier tube. The range indicated by the triangle in Fig. 5a shows the range of change in the intensity of light that can be processed by the microprocessor 16 of the end point detector, and it depends on the configuration of the end point detector (characteristics of parts used and how they are used). Change. The slope of the straight line a ₁ is determined by the magnitude of the voltage applied to the photocathode of the photomultiplier tube 7 and the die note.

The range shown by b in FIG. 5 is a range of change in the intensity of the target light (usually, the specific wavelength is selected by the optical filter 6) when etching is performed under certain conditions (when the end point is detected). .. The range indicated by c in FIG. 5 does not fall within the range indicated by the triangle in FIG. 5a, and therefore cannot be processed by the microprocessor 16.

In order for the microprocessor 16 to be able to process all changes in the light intensity in the range shown in FIG. 5B, the range shown in FIG. 5A should be shifted to the right in FIG. It is sufficient to shift the range indicated by b to the left.

The former is difficult to realize because it is uniformly determined by the characteristics of the photomultiplier tube 7 and the performance of the components. The latter is easy because the intensity of light can be reduced. The reason for selectively converting the plurality of perforated plates 20A to 20D in FIG. 4 is to shift the range indicated by b in FIG. 5 to the left.

[0008]

[Problems to be solved by the device]

 Thus, conventionally, the plurality of perforated plates 20A to 20D have been artificially converted according to changes in the intensity of light. Further, since the size of the hole 19 is discontinuous, such as 2 mm, 1 mm, 0.5 mm ..., The range also changes stepwise, and the amount of light input to the photomultiplier tube can be continuously adjusted. Can not.

[0009]

[Means for Solving the Problems]

 In order to solve the above problems, the end point detector of the present invention adjusts the light quantity of plasma light of the dry etching apparatus 1 by a light quantity adjusting unit A as shown in FIG. Only the light is extracted by the optical filter 6, the intensity of the light of the specific wavelength is converted into an electrical signal by the optical intensity-electrical signal conversion element 7, and this electrical signal is input to the electrical signal processing device 16 to change the optical intensity. In the end point detector of the dry etching apparatus for determining the etching end point, the light amount adjusting plate 4 having the light passing hole 19 for continuously changing the light amount according to the rotational displacement is installed in the light amount adjusting A, The above-mentioned light intensity-an automatic control system 8 for controlling the rotation of the light quantity adjusting plate 4 by a motor 9 so that the output signal of the electric signal converting element 7 matches the set output of the setting device 12 is provided. Electric The output of the signal converting element 7 a structure for switching the changeover switch 13 to the electrical signal processing device 16 from the automatic control system 8.

[0010]

[Work]

 The plasma light of the dry etching apparatus 1 passes through the light passage hole 19 of the light quantity adjusting plate 4 of the light quantity adjusting unit A, and the light quantity is adjusted at that time. Only the light of the specific wavelength is extracted by the optical filter 6 from the light of which the light amount is adjusted, and the intensity of the light of the specific wavelength is converted into an electric signal by the light intensity-electric signal conversion element 7.

The motor 9 is driven by the automatic control system 8 to control the rotation of the light quantity adjusting plate 4 so that this electric signal matches the set output of the setting device 12, and when it matches, the motor 9 is stopped and the light quantity adjusting plate is stopped. 4 is stopped. The light having a specific wavelength is extracted by the optical filter 6 from the amount of light that has passed through the light passage hole 19 of the light amount adjusting plate 4 at the time of stop, that is, the amount of light that is proportional to the rotational displacement.

The light intensity of the specific wavelength is converted into an electric signal by the light intensity-electric signal conversion element 7. The electric signal is switched by the changeover switch 13 from the automatic control system 8 to the electric signal processing device 16 to obtain a change in the light intensity, and the end of etching of the dry etching device 1 is determined.

[0013]

【Example】

 FIG. 1 (A) is an explanatory perspective view showing the structure of an embodiment of the end point detector of the present invention, FIG. 1 (B) is a block diagram showing the structure of its automatic control system, and FIG. 2 is a light quantity adjusting plate of the present invention. FIG. In FIG. 1, 1 is a dry etching device, 2 is a case (dark box), 3 is a light entrance formed in this case 2, 4 is a light quantity adjusting plate installed in the light quantity adjusting section A in the case 2, and rotational displacement is performed. In accordance with the above, there is a light passage hole 19 that continuously changes the light amount (see FIG. 2).

Reference numeral 5 is an optical fiber for transmitting the light whose amount of light has been adjusted through the light passage hole 19 of the light amount adjusting plate 4, 6 is an optical filter for extracting light of a specific wavelength from the optical fiber 5, and 7 is A photomultiplier tube for converting the intensity of light of a specific wavelength into an electric current, 8 is an automatic control system, 9 is a DC motor driven by this automatic control system, 10 is the rotation of this DC motor 9, and is a light quantity adjusting plate 4 This is a rotary transmission mechanism that uses belts, pulleys, etc. to transmit to the rotating shaft of the.

Reference numeral 11 denotes a current-voltage conversion amplifier that converts an electric signal (current) of the photomultiplier tube 7 into a voltage, and 14 compares an output voltage of the amplifier 11 with a set voltage set by a setter 12. Then, 15 is a comparator for outputting the difference voltage, 15 is a motor drive circuit for driving the DC motor 9 by inputting the output difference voltage, and 13 is the output voltage of the current-voltage conversion amplifier 11 from the comparator 14 side. This is a changeover switch for switching and inputting to the processor 16 side and for shutting off the output to the DC motor 9 of the motor drive circuit 15.

FIG. 3 is an explanatory diagram of a feedback control system in the automatic control system of the present invention. Reference numeral 17 denotes a PI amplifier for outputting the output differential voltage of the comparator 14 when there is an output differential voltage, and reference numeral 18 denotes a transfer for inputting the output voltage of the PI amplifier 17 to input a feedback voltage to the comparator 14. Is a function. The transfer function 18 is the drive of the DC motor 9, the rotation of the light quantity adjusting plate 4, and the change of the input light quantity of the photomultiplier tube 7, and the output voltage of the transfer function 18, that is, the feedback voltage becomes the input of the comparator 14.

The operation of the present embodiment having the above configuration will be described. The set value by the setting device 12 is generally the center value of the range in which the intensity signal (electrical signal) of the light processed by the microprocessor 16 changes, and is 2.5 V if the range is 0 to 5 V, for example. .. The voltage applied to the photocathode of the photomultiplier tube 7 and the dynode is set near the center of the application range, and the control operation is started.

The plasma light of the dry etching apparatus 1 passes from the light inlet 3 to the light passage hole 19 of the light quantity adjusting plate 4 of the light quantity adjusting unit A, and the light quantity is adjusted at that time. The light of which the amount of light is adjusted passes through the optical fiber 5, and only the light of the specific wavelength is extracted from the optical filter 6, and the intensity of the light of the specific wavelength is converted into a current by the photomultiplier tube 7.

This current is converted into a voltage by the current-voltage conversion amplifier 11 of the automatic control system 8, and this voltage and the voltage set by the setting device 12 are compared by the comparator 14, and the difference voltage thereof is used to drive the motor. The direct current motor 9 is driven by the input to the circuit 15, and the light quantity adjusting plate 4 is rotated via the rotation transmission mechanism 10. The amount of light passing through the light passage hole 19 can be changed by rotating the light amount adjusting plate 4.

As a result, the output current of the photomultiplier tube 7 changes, and the output voltage of the current-voltage conversion amplifier 11 changes. Until this output voltage matches the set voltage, in other words, until the output voltage difference of the comparator 14 becomes zero, the light quantity adjusting plate 4 is rotated by the DC motor 9, and when it matches, the DC motor 9 is stopped. The light amount adjusting plate 4 is stopped and the control operation is completed.

When the control operation is completed, the amount of light input to the photomultiplier tube 7 becomes appropriate, so that the output current thereof is converted into a voltage by the current-voltage conversion amplifier 11, and this voltage is changed by the changeover switch 13. The automatic control system 8 switches and inputs to the microprocessor 16 to obtain a change in the light intensity, and the end of etching of the dry etching apparatus 1 is determined.

The operation of the feedback control system will be described in detail with reference to FIG. The output current of the photomultiplier tube 7 is converted into a voltage by the current-voltage conversion amplifier 11, and the set voltage and the feedback voltage are compared by the comparator 14. If there is a difference, the difference voltage is transmitted to the transfer function 18 by the PI amplifier 17. The output voltage of the transfer function 18, that is, the feedback voltage is input to the comparator 14, and this operation continues until the output of the PI amplifier 17 becomes zero.

When the output of the PI amplifier 17 becomes zero and the control operation ends, the amount of light input to the photomultiplier tube 7 becomes appropriate, so that the output of the current-voltage conversion amplifier 11 as described above. The voltage is input to the microprocessor 16 by the changeover switch 13, and the etching end point detection processing is started.

Conventionally, a plurality of perforated plates 20A to 20D having light passage holes 19 having different diameters were manually converted and the amount of light input to the photomultiplier tube 7 was artificially adjusted. In the embodiment, the adjustment can be performed automatically, the parts replacement work can be eliminated, and the adjustment time of the light quantity input to the photomultiplier tube 7 can be greatly shortened.

Table 1 shows the result of comparing the light amount adjustment times of the conventional device and the present invention.

[0026]

[Table 1] As is apparent from Table 1 above, the conventional light amount adjustment time was 75 minutes, but in the present invention, it was possible to reduce it to 15 minutes.

[0027]

[Effect of the device]

 As described above, according to the present invention, the light quantity adjusting plate A is provided with the light quantity adjusting plate 4 having the light passage hole 19 for continuously changing the light quantity according to the rotational displacement, and the output of the light intensity-electrical signal converting element 7 is provided. An automatic control system 8 is provided to control the rotation of the light quantity adjusting plate 4 by the motor 9 so that the signal matches the set output of the setting device 12. When the signals match, the output of the light intensity-electrical signal conversion element 7 is output from the automatic control system 8. Since the electric signal processing device 16 is configured to be switched by the changeover switch 13, the amount of light input to the light intensity-electrical signal conversion element 7 can be automatically adjusted, and not only the parts replacement work is unnecessary. The time for adjusting the amount of light input to the light intensity-electrical signal conversion element 7 can be greatly shortened.

[Brief description of drawings]

FIG. 1A is an explanatory perspective view showing the configuration of an embodiment of an end point detector of the present invention. (B) is a block diagram showing the configuration of the automatic control system.

FIG. 2 is a front view of a light amount adjusting plate according to the present invention.

FIG. 3 is an explanatory diagram of a feedback control system in the automatic control system of the present invention.

FIG. 4 is a structural explanatory view of an example of a conventional end point detector.

FIG. 5 is a diagram showing the relationship between the intensity of light (light energy) input to the photomultiplier tube and the output current of the photomultiplier tube.

[Explanation of symbols]

 1 Dry Etching Device 2 Case (Dark Box) 3 Light Inlet 4 Light Quantity Control Plate 5 Optical Fiber 6 Optical Filter 7 Light, Intensity-Electrical Signal Converter (Photomultiplier Tube) 8 Automatic Control System 9 (DC) Motor 10 Rotation Transmission Mechanism 11 Current-voltage conversion amplifier 12 Setting device 13 Changeover switch 14 Comparator 15 Motor drive circuit 16 Electric signal processing device 17 PI amplification unit 18 Transfer function 19 Light passage hole

Claims (1)

[Scope of utility model registration request] 1. The amount of plasma light of a dry etching device (1) is adjusted by a light amount adjusting section (A), and only light of a specific wavelength is extracted by an optical filter (6) from the light amount adjusted light. The light intensity of the wavelength is converted into an electric signal by the light intensity-electrical signal conversion element (7), the electric signal is input to the electric signal processing device (16) to obtain the change in the light intensity, and the etching end point is determined. In the end point detector of the dry etching apparatus, a light passage hole (19) for continuously changing the light amount according to the rotational displacement in the light amount adjustment (A).
Is installed, and the light intensity adjusting plate (4) is set so that the output signal of the light intensity-electrical signal converting element (7) matches the set output of the setting device (12). )
An automatic control system (8) for controlling rotation by means is provided, and at the time of coincidence, the output of the light intensity-electrical signal conversion element (7) is switched from the automatic control system (8) to the signal processing device (16) by a switch (13). The end point detector of the dry etching system configured to switch with.