JPS6028233A - Monitor device for etching - Google Patents

Abstract

PURPOSE:To improve yield by identifying the states of reflection of each point on a wafer changing as an etching progresses as picture signals by an image sensor, scanning each point on the wafer in succession and monitoring the state of etching in the wafer from the changes of the picture signals. CONSTITUTION:Upper and lower electrodes 3 and 2 are arranged in an etching chamber 1, both side walls thereof each have window glass 4a, 4b, and voltage from a high-frequency power supply 5 is applied to these electrodes. A wafer 6 is placed on the electrode 2, CCl4 gas is introduced into the chamber 1, and the surface of the wafer 6 is etched. Beams from a laser 7 are projected to the surface of the wafer 6 through a mirror 9 controlled by a lens 8 and a drive 10 and the window glass 4a at that time, and reflected beams from the surface of the wafer are projected to a monitor device 100 through the window glass 4b, a deflection foucs optical system 11 and an image sensor 12. Accordingly, the differences of etching at the initial stage and in mid course are compared with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to dry etching, and more particularly to an etching monitoring device that enables in-process monitoring of the progress of etching within a wafer. It is something.

[Background of the invention]

Conventionally, it has been difficult to quantitatively understand the etching mechanism and the distribution of plasma during multiple discharges, and there are still many points that have not been elucidated.

We have been considering the measurement of internal uniformity distribution during etching as providing one solution to the investigation of the above-mentioned problems.

To measure the internal uniformity distribution of the wafer by etching, after etching, take the wafer out of the etching chamber, remove the photoresist, and then measure the level difference in the etched area of the wafer (7) using an interference microscope. was. This method can accurately and in detail measure any position within the wafer, but it also measures the etching progress at each point on the wafer, which corresponds to the distribution of plasma during etching, that is, the uniformity distribution within the wafer. It was not possible to monitor it in-process (during the etching process).

Therefore, a demand has arisen for monitoring the etching progress within a wafer during etching in-process and in a simple manner.

On the other hand, there are promising methods in which the etching process is directly monitored by optical means. We considered observing the wafer during etching with a TV camera from directly above, but adding structural changes to the upper etching electrode would change the plasma discharge situation, resulting in problems such as the plasma not being generated evenly or the wafer being etched again. Since the gas flow was not uniform, a drawback appeared in that the etching uniformity distribution within the wafer deteriorated. Furthermore, when optically observing the wafer surface during etching, it was found through experiments that the illumination light irradiating the wafer and the light reflected from the wafer surface were scattered and affected by plasma discharge light. Therefore, it has become necessary to select a light source and illumination system that are not affected by plasma discharge light.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to monitor the etching uniformity distribution within the wafer in-process by capturing the etching progress status that changes from time to time at each point on the wafer using video signals during etching. To provide an etching monitor device capable of performing the following steps.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention uses an image sensor to capture the reflection state of each point on the wafer, which changes as the etching progresses, as an image signal, and if necessary, rotates the wafer during etching. Each point on the wafer is sequentially scanned, and the etching uniformity distribution within the wafer is monitored in-process during the etching process from changes in image signals.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a configuration diagram according to an embodiment of the present invention.

1 is the etching chamber, 2 is the lower electrode, 6 is the upper electrode, 4g
, 4b is a window glass 5 is a high frequency power supply, 6 is a weno, 7 is a laser.

8 is a lens, 9 is a mirror, 10 is a mirror drive device, 11
12 is an image sensor, and 100 is a monitor device. Here, the deflection focusing optical system 11 is connected to the wafer 6.
This is an optical system that forms a surface pattern image on the image sensor 12.

FIG. 2 is a plan view of the wafer 6 placed on the lower electrode 2 in an arbitrary direction (l), in which 6a is the stripe line for dicing, 6b is the circuit pattern part, and 6C is the wafer 1. It shows the scanning direction of the laser beam that passes through the center and is irradiated by the laser 7. Further, 81 to S12 indicate intersections between the laser irradiation scanning line 6C and the stripe line 6a.

FIG. 3 is a diagram showing a part of a cross section of the wafer 6. As shown in FIG. 51 is the substrate material SL, and 52 is the base material 8 ich.
3 is a material M to be etched, and 54 is a photoresist film. The photoresist film 54 is a mask, 9, A15
Etch 3. A shows the state before the start of etching, B shows the state in the middle of etching, and C shows the state where the etching of M53 has been completed and the base material Sigh52 is being etched.

FIG. 4 shows an internal configuration diagram of the monitor device 100.
14 is an A/D converter, 13 is a timing circuit that drives the image sensor 12 and gives timing for starting conversion of the A/D converter 14, 15 is a memory circuit, and 16 is a characteristic opposite to that of the A/D converter 14. 17 is a signal display device.

FIG. 5 shows the video signal output from the image sensor 12 that changes as etching progresses.
, a + b r C correspond to etching processes A, B, and C in FIG. 6, respectively.

Next, the operation of the present invention will be explained in detail with reference to FIGS. 1 to 5.

The etching chamber 1 is supplied with an etching gas (for example, CC'4 t 5Dcc) from a gas supply device (not shown).

/min) and maintained at a constant pressure (for example, 9 pa) by an exhaust device (not shown).

For example, 15-56 MI (z * 40
When the OW specific output high frequency electrode is applied between the lower electrode 2 and the upper electrode 3, plasma discharge is generated and the surface of the wafer 6 is etched. This is dry etching and is a well-known fact.

In parallel with the above-mentioned etching, a laser beam emitted from a laser 7 installed outside the etching chamber 1 is reflected by a mirror 9 through a lens 8, and the wafer 6 being etched is passed through a window glass 4a attached to the etching chamber 1. irradiate the center of the surface. The mirror removing drive device 10 causes the mirror 9 to swing at a required period, and the laser beam is scanned one-dimensionally on the wafer surface on a straight line passing through the center of the wafer, as shown at 60 in FIG.

The reflected light of the laser beam irradiated onto the surface of the wafer 6 also passes through the window glass 4 in the opposite path to that described above, passes through the entire deflection and focus optical system 11, and reaches the image sensor 12. The deflection focusing optical system 11° has a function of forming images having different focal lengths, and forms an image of the surface pattern of the wafer 6 on the image sensor 12.

The image sensor 12 receives a clock signal from the timing circuit 13 and receives an image signal (fifth
a r b + e) is output to the signal display device 17.

As the etching progresses, the surface of the wafer is shown in Figure 3 A-+.
B-) I/I is masked with photoresist 54 as shown in C.
-AI +53 of the part without 1 is being worked and added.

Since the stripe line 6a for dicing on the wafer 6 is a portion not masked by the photoresist film 54, the material to be etched AJ53 is etched during the etching process, the base material SiO is exposed, and the reflectance of the surface changes significantly. .

On the other hand, since the circuit pattern portion 6b surrounded by the stripe line 6a is masked with the photoresist film 54 at a ratio of about 40, even if it is etched, there is little change in the reflectance of the surface.

Therefore, the intersection point 51eS 2 + between the laser irradiation scanning line 6C on the wafer 6 and the wafer stripe line 6a...
In S12, the etching progress in Fig. 6 A-)B-+
Along with C, the image signal is as shown in Fig. 5 a→l) −+ C
The circuit pattern portion 6b changes as shown in Fig. 5a-+ depending on the location on the etching progress.
The level fluctuates like b-+C.

On the other hand, the image signal of the surface pattern of the wafer 6 at the time of starting the etching discharge is converted into a digital value by the A/D converter 14 at the timing of the timing signal from the timing circuit 13, although it varies depending on the change in the image signal during the etching process. The digital value is input to the storage circuit 15 and stored at the timing of the conversion end signal from the A/D converter. Furthermore, this digital value is returned to an image signal by a D/A converter 16 having characteristics opposite to those of the A/D converter 14, and a signal display device 17 displays an image signal ( The waveform shown in FIG. 5a) continues to be output.

The above two image signals, namely, the image signal of the wafer surface at the start of the etching discharge (Fig. 5 a) and the image signal during the etching process (which changes as shown in Fig. 5 a r b + c) are constantly output as signals. By displaying and observing on the display device 17, the progress of etching can be monitored in-process.

For example, at the time of etching in FIG. 5C, the peak value at the center of the wafer is lower than the peak value at the periphery of the wafer, so etching progresses faster at the periphery. You can understand it while doing so.

Although we have only discussed image signals for one scan on the wafer, if necessary, the wafer can be rotated and the irradiation scan line on the wafer can be
By moving c and outputting an image signal in synchronization with the rotation of the wafer, it is possible to obtain the progress of etching at any position on the wafer, making it possible to monitor the uniformity distribution within the wafer in-process.

〔Effect of the invention〕

As explained above, according to the present invention, the progress of etching within a wafer during etching can be monitored in-process, so it is possible to measure the distribution of etching uniformity during etching. This has the effect of being able to grasp the plasma distribution state during discharge.

If the plasma distribution state during discharge is known, it will be possible to create a more stable etching life state by controlling the etching gas flow rate, etching pressure, and output of the high-frequency power supply.
This has a significant effect on improving wafer product yield.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram according to an embodiment of the present invention. FIG. 2 is a plan view of the wafer and its shape showing the scanning direction. FIG. 3 is a diagram showing a part of the cross section of the wafer, which explains changes as etching progresses. 4 is an internal configuration diagram of the monitor device, and FIG. 5 is a waveform diagram of an image signal representing changes in the pattern image on the wafer surface as etching progresses. 1...Paper etching chamber, 6...Wafer, 7...Laser, 9...Mirror, 10...Mirror drive device,
DESCRIPTION OF SYMBOLS 11... Deflection focus optical system, 12... Image sensor, 13... Timing circuit, 14... A/D converter, 15... Memory circuit, 16... D/A converter,
17...Signal display device. Representative Patent Attorney Akio Takahashi S Figure 1 Figure 2 Figure 3 (E3) (C)

Claims (1)

[Claims] 1. The wafer being etched is continuously scanned one-dimensionally with light incident in a predetermined direction, and the reflected light obtained in the opposite direction to the incident direction is guided to an image sensor through a deflection focusing optical system. - In a device that displays an image signal of a surface pattern, it constantly outputs an image signal of the wafer surface pattern at the start of etching discharge, and also outputs an image signal of the wafer surface pattern corresponding to the etching progress status during etching, and An etching monitor device characterized by displaying two image signals so that they can be constantly compared.