JPS61241923A - Apparatus for monitoring etching hole and trench - Google Patents

Abstract

PURPOSE:To enable monitoring of the size and shape of an etching hole and trench by providing photo-detector means for detecting a specific diffracted light among the diffracted lights reflected from a wafer, and abnormality detector means for detecting etching abnormality from the magnitude of contrast. CONSTITUTION:The laser beam applied onto a wafer 7 reflects, diffracts and interferes according to a regular pattern on the wafer 7, reaches onto a ground glass 27 through a window 6 formed in a low-pressure treatment chamber 1, and diffuses at the surface of the ground glass 27 to be drawn into a first photo-detector 28. On the other hand, the light specularly reflected at the surface of the wafer 7 is taken into a second photo-detector 32 through a half-mirror 26. The etching amount of an etching mask 60 can be monitored by the waveform detected by the second photo-detector 32, and the etching speed ratio can be monitored by comparing the result of the above monitoring with the etching amount of the hole and trench portion obtained from the waveform detected by the first photodetector 28. With this, abnormality in the size and shape of the etching hole and trench can be monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an etching hole/groove monitoring device, and particularly to an etching hole/groove monitoring device suitable for monitoring the dimensions and shape of an etching hole/groove during an etching process. This invention relates to a gutter monitoring device.

[Background of the invention]

In order to achieve high integration of semiconductor devices, the conventional planar element structure is being converted to a three-dimensional element structure.

Therefore, a technique is required to form a groove having a depth of 5 to 5 .mu.m and a width of 1 to 2 .mu.m in the silicon substrate by, for example, dry etching.

The process conditions for drilling holes and forming grooves are difficult to set. However, the process conditions change over time due to subtle changes in the composition of the reaction gas, which is mainly caused by the adsorption of polymers and gases onto the walls of the low-pressure processing chamber due to long-term processing. As a result, the etching shape may become abnormal or the etching rate may change.
It may not be possible to etch to the desired depth. Furthermore, slight fluctuations in reaction gas pressure and applied power can cause abnormalities in the etching results.

Specifically, ■ needle-like protrusions appear on the bottom of the hole/groove, ■ the area around the bottom of the hole/groove is deeply etched, ■ the bottom of the hole/groove becomes narrower, ■ the depth of the hole/groove becomes narrower. Abnormalities such as fluctuations occur.

By the way, as a conventional technology for monitoring abnormalities in holes and grooves, Solid State Science and Technology (S
olirL 5tate 5ciar&zg k Ta
ah-nology) May 1973 issue article [Optical Monitoring Using Grating Test Patterns for Etching Silicon Oxide and Silicon Nitride on Silicon]
f the Etc. of Sin, an
ti Si, N, on Si by tha Uza
ofGrating Te5t PatternJ (
H-P-Klainknacht & H-Maiar
)) introduces a technique in which a diffraction grating is used as a test pattern, and during etching of this diffraction grating pattern, light is irradiated onto the diffraction grating and the amount of etching is measured by the interference of the single reflected diffracted light. . This conventional technique is an excellent technique for monitoring the amount of etching because it is possible to extract a signal with less noise components by providing a test pattern. However, in this conventional technology, the above-mentioned ■～■
It is difficult to monitor abnormalities.

Furthermore, as other prior art, Japanese Patent Application Laid-Open No. 54-17872
There is a technique disclosed in the publication No. However, the technique disclosed in this publication is not necessarily suitable for monitoring abnormalities in the shape of holes and grooves.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an etching hole/groove monitoring device capable of solving the problems of the prior art and monitoring the dimensions and shapes of etching holes/grooves during an etching process without using a test pattern on a substrate. Our goal is to provide the following.

[Summary of the invention]

The present invention provides a laser light source, a means for irradiating the laser light emitted from the laser light source to an arbitrary point on a wafer being processed in a dry etching apparatus, and a means for irradiating the laser light emitted from the laser light source to an arbitrary point on a wafer being processed by a dry etching apparatus; , comprising a light detection means for detecting a specific diffracted light, and an abnormality detection means for determining a contrast from a change in the intensity of the detection light detected by the light detection means and detecting an etching abnormality from the magnitude of the contrast. However, with this configuration, the above object can be achieved reliably.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a dry etching apparatus and an etching hole/groove monitoring apparatus of the present invention attached thereto.

The dry etching apparatus includes a low-pressure processing chamber 1, an anode 2 and a cathode 3 installed therein, a high-frequency power source 4, a control system 5 for the same, and a window 6 formed in the low-pressure processing chamber. It is configured as follows. In addition, the code|symbol 7 shows a wafer.

The embodiment of the etching hole/groove monitoring apparatus shown in FIG. A first photodetector section and a second photodetector 32
, A/D converter, motor control system 35, microcombi island 36, CRT 37, and abnormality indicator 3
8.

The X stage 8 is installed at a position facing a window 6 formed in the low pressure processing chamber 1 of the dry etching apparatus. Further, the X stage 8 is operated to move in the X direction (left and right direction in FIG. 1) by a drive unit having a motor 9 connected to the motor control system 35 and a ball screw lO connected to the motor 9. It has become.

The X stage 1] is installed on one side of the X stage 8, and is directed in the Y direction via a guide block 12 attached to the X stage 1 and a guide rod 13 fixed to the X stage 8. (Vertical direction in Figure 1)
are guided by.

The X stage l] includes a motor 14 connected to a motor control system 35 and a ball screw 15 connected to the motor 14.
and a nut 16 for movement in the Y direction.

The θ stage 17 is rotatably installed on the Y stage 1], and is connected to the motor 1 connected to the motor control system 35.
8, a pinion 19 connected thereto, and a gear 20 provided on the outer periphery of the θ stage F.

A Ha-N-laser or the like is used as the laser light source 21, and this laser light source 21 is installed on one surface side of the θ stage 17. The laser light emitted from this laser light source 21 is reflected by the mirrors 22 and 23, is reflected by the lens cap 25, is reflected by the half mirror 26, and is formed in the low pressure processing chamber 1 through the transparent part of the ground glass 27. The wafer 7 is irradiated through the window 6 .

The glass window 27 is placed on one side of the θ stage 17, facing the window 6 formed in the low pressure processing chamber 1.

The first photodetector side is arranged on one surface side of the ground glass 27, and is configured to detect a specific diffracted light reflected from the wafer 7 and send it to the conversion device of Le. . Further, this first photodetector section is connected to the motor control system 35.
A detection position determination section having a motor 36 connected to the motor 36, a ball screw 3o connected to the motor 36, and an arm 31 connected to the first photodetector floor and screwed to the ball screw 3o allows the It is supported so that the detection position can be adjusted so that specific diffracted light out of the diffracted light reflected from the wafer 7 can be detected.

The second photodetector 32 is arranged on one side of the ground glass 27, and detects the reflected light that is specularly reflected without being diffracted by the surface of the wafer 7, and sends it to the φ conversion device. ing. Note that the second photodetector 32 is connected to a lever 33.
It is fixed to the θ stage 17 via.

The ω converter U photoelectrically converts the specific diffracted light sent from the first photodetector 32 and the reflected light sent from the second photodetector 32, and converts it into a microcomputer. The signal is sent to the beater 36.

The microconbeater 36 calculates the contrast of the change in light intensity from the data sent from the VD converter U, compares the contrast with a threshold value, and when an etching abnormality is detected, displays the CRT 37 and the abnormality indicator 38.
At the same time, a stop signal is sent to the control system 5 of the dry etching apparatus.

The X stage 8 and its drive unit, and the Y stage 11
A means for irradiating the laser light emitted from the laser light source 21 to an arbitrary point on the wafer 7 being processed by the dry etching device, using the drive unit, mirrors 22, 23, lenses u, 25, and half mirror 4. is configured.

Further, the θ stage 17 and its driving section, the first .theta.
Photodetection means for detecting a specific diffracted light out of the diffracted light reflected from the wafer 7 by the second photodetector floor 32 and the detection position determining section of the first photodetector floor. is configured.

Further, the le omega converter 34 and the microcomputer 36 constitute an abnormality detecting means for determining a contrast from a change in the intensity of the detection light detected by the light detecting means and detecting an etching abnormality from the magnitude of the contrast. has been done.

Next, the operation of the embodiment described above will be explained with reference to FIGS.

A wafer 7 to be processed is placed on the anode 2 installed in the low pressure processing chamber 1 of the dry etching apparatus shown in FIG. 1, and then the low pressure processing chamber 1 is set to the processing conditions.

Here, the laser light source 21 is turned on. This laser light source 2
The laser beam emitted from 1 is reflected by a mirror 22゜n, further formed into a parallel beam of about 5 to 10φ by a lens 25, then passes through a half mirror 26 and a transparent part of ground glass 27, and is subjected to low pressure treatment. The light is irradiated onto the wafer 7 through a window 6 formed in the chamber l.

The irradiation position of the laser beam onto the wafer 7 is the X stage 8.
The motor 9 and ball screw lO that constitute the drive section of
Move the X stage 8 through the Y stage 1]
The motor 14 and ball screw 1 that constitute the drive unit of
It can be arbitrarily determined by moving the Y stage 11 via the arrows 5 and 5.

The laser beam irradiated onto the wafer 7 undergoes one reflection, one diffraction, and interference due to the regular pattern on the wafer 7, as will be described in detail later, and is reflected onto the ground glass 27 through the window 6 formed in the low-pressure processing chamber l. reach. This light is diffused by the frosted glass surface.

The light is taken into the first photodetector section.

At that time, the detection position of the first photodetector section is the θ stage 1.
The θ stage 17 is rotated through a motor 18, a pinion 19, and a gear, which constitute a driving section of the 7, and a motor 29, a ball screw (
This can be determined by changing the position of the first photodetector section via the arm 31 and the arm 31, and any light emitted from the window 6 formed in the low-pressure processing chamber IK can be detected.

On the other hand, the light that is specularly reflected without being diffracted by the surface of the wafer 7 is taken into the second photodetector 32 through the half mirror field.

Next, monitoring of etched holes and grooves will be explained by taking as an example the etching process of a semiconductor device provided with a /f tangent shown in FIG.

Generally speaking, when considering a multi-slit diffraction image where the number of slits is N1 and the width d, the light intensity in this case is where, '6 is the central intensity of the diffraction image, t is the pitch of the slits, λ is the wavelength of the light,
b is the distance from the slit to the diffraction image plane, and X is the position on the image plane and the distance to the center of the diffraction image.

In the third factor, the envelope 45 is the intensity distribution of the diffraction image of a single slit with a width d, but from equation (1), the envelope 45 is 0.
(0)K is achieved when the following equation (2) holds true.

X Pain λ #(9θ=-=-・-・...(2) d Also, when the number of slits N is sufficiently large, a sharp peak appears due to multiple interference, but the position of the peak is determined by the following equation (31
Follow.

% formula %) In formulas (2) and (3), folding is an integer, and θ is a diffraction angle.

Therefore, the diffraction patterns of slits having different widths have shapes as shown by curves 46 and 47 in FIG.

At this time, the distance from the center of the diffraction image is defined as X and each curve 46, 4
The area between 7 and 7 indicates the light intensity of each luminous flux.

As can be seen from equation (1), the slit forming the curve 47 has a smaller width and a lower light intensity. However, at the position of point 48 in FIG. 4, the light intensities of the two light beams are about the same. Furthermore, in the region 49, the light intensity of the light beam forming the curve 47 is high.

Now, consider the diffraction image of the pattern shown in FIG. 2 above.

In FIG. 2, focusing on the diffracted lights 40 and 41 in the X direction, the widths dX, , dX are both approximately the same size, so the diffraction images from each pattern have the same shape. Furthermore, since the area of the part without a hole is larger than the area of the hole, and the length rLr of the part without a hole is longer, the 410 diffraction image of the diffracted light reflected from Taisei is
A curve 51 shown in FIG. 5 is smaller overall than the curve 50 of the diffraction image of the diffracted light 4G reflected from the surface.

As a result, the interference contrast is low and etching monitoring is difficult.

On the other hand, in FIG. 2, the diffraction in the Y direction is rLr,
#tLy, but dY is large. Further, the region 39 does not have diffracted light in the Y direction. Therefore, as shown in FIG. 6, the diffracted light 43 due to tr3 (see FIG. 2)
There is an order in which the - curve 52 is smaller than the curve 53 of the diffracted light 42 (see FIG. 2) due to ctr2.

tr, =tY, =1 ttm, dyB =5μm
Calculating the case of , if equation (2) and equation + 31, wind = 3 and corridor = 5 (3rd order diffracted light and 5th order diffracted light) are detected, the contrast will be larger, so more accurate monitoring will be possible. It can be performed.

That is, in the case of having the surface notch shown in FIG.
Of the diffracted light in the Y direction, the third and fifth orders must be detected.

Furthermore, in the case of a complex pattern, it may not be possible to make an analogy based on the pattern on the surface, and it may be necessary to detect all diffraction patterns and select those that cause intensity changes.

By the way, the interference waveform obtained by K as described above basically includes an intensity change due to the interference of the reflected light from the area 39 on the surface of the pattern shown in FIG. 2 and the large beam. Therefore, if the light from Alternative I becomes weaker for some reason,
The contrast of interference intensity changes becomes smaller.

Therefore, as shown in FIG. 7, the maximum 55 and minimum 56 of the change in light intensity are constantly determined, and the most recent one is determined from equation (4) and displayed on the CRT 37 shown in FIG. here,
When Ci becomes abnormally small, substitute 54 (see Figure 2)
You can see that the light intensity has decreased.

This corresponds to fJI, the substitute needle-like protrusion 57 shown in Fig. 8, the 9th
The substitute shape abnormalities 58, 59, or 10th shown in the figure
This refers to an etching abnormality such as increased variation in hole depth as shown in the figure.

Therefore, a tolerance range is determined in advance for needle-like protrusions, abnormalities in the shape of large formations, or variations in hole depth from hole to hole, and the contrast of light intensity changes within this tolerance range is determined, and this contrast is used as a threshold value. When the calculated contrast becomes smaller than the threshold value, an etching abnormality is displayed on the CRT 37t or abnormality display 38 shown in FIG. 1, and at the same time a signal is sent to the control system 5 of the dry etching apparatus to stop the etching process. do.

Furthermore, the detection waveform by the second photodetector 32 causes the first
] It is possible to monitor the amount of etching of the etching mask mark of the pattern shown in the figure.

Furthermore, by comparing this monitoring result with the etching amount of the hole/groove portion determined from the detection waveform by the first photodetector unit, the etching speed ratio of the etching material to the etching mask can be monitored. . In this case as well, an allowable range of the selection ratio α is determined in advance, and when the range is exceeded, an abnormality in etching is displayed and at the same time a signal is sent to the control system 5 of the dry etching apparatus to stop the etching process.

The above method uses an optical interference method that takes advantage of the fact that the depth of holes and grooves changes during etching.

In other words, the following equation (5
) changes in light intensity due to changes in d are detected.

1 = 16 (r, +r4+2 wealth Ca1 (flat))
``...'' (5) where r, 14 are the intensity of the light reflected from the non-perforated surface and the substitute, respectively, λ is the wavelength of the irradiated light, and d is the depth of the hole.

Equation (6) also shows that when the depth d of the hole is constant, changing the wavelength λ causes a change in light intensity.

Therefore, the monitoring of etched holes and grooves explained above is
When etching is not in progress, this can be easily achieved by changing the wavelength of the irradiated light continuously or discretely. That is, the monitoring device of this embodiment can be easily applied not only during etching but also to monitoring abnormalities in etched holes and grooves after etching.

In the present invention, a means for irradiating a laser beam emitted from a laser light source 21 onto an arbitrary point on a wafer 7 being processed by a dry etching apparatus, and a means for irradiating a specific point of diffracted light reflected from the wafer 7 are used. The specific structure of the photodetection means for detecting light and the abnormality detection means for determining the contrast from the intensity change of the detected light detected by the photodetection means and detecting etching abnormalities from the magnitude of the contrast are shown in the drawings. It is not limited to the embodiments, and any device having the desired function may be used.

〔Effect of the invention〕

According to the present invention described above, there is provided a laser light source, a means for irradiating the laser light emitted from the laser light source to an arbitrary point on a wafer being processed in a dry etching apparatus, and a means for irradiating the laser light emitted from the laser light source to an arbitrary point on a wafer being processed by a dry etching apparatus; A light detection means for detecting a specific diffracted light among the diffracted light, and an abnormality detection means for determining the contrast from the intensity change of the detection light detected by the light detection means and detecting an etching abnormality from the magnitude of the contrast. With this, it is possible to detect specific diffracted light that does not contain noise components among the diffracted light generated due to the regularity of the surface of the semiconductor device during the etching process. This method has the advantage of being able to monitor abnormalities in the dimensions and shapes of etched holes and grooves without using test patterns.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing an embodiment of the present invention apparatus, FIG. 2 is a partially enlarged perspective view of a wafer as a sample, FIG. 3 is a diagram showing the light intensity of diffracted light, and FIG. 4 is a diagram showing two Comparison diagram of diffraction images, Figures 5 and 6 are diagrams showing the light intensity of diffracted light, Figure 7 is a diagram showing intensity changes of interference light, Figures 8, 9, and 1
Figure 0 is a diagram showing an example of etching abnormality, and Figure 1 is a partially enlarged perspective view of a wafer as a sample. 1... Low pressure processing chamber of the dry etching device 2... Same anode 5... Same cathode 4... Same high frequency power source 5... Same control system 6... Window 7 formed in the low pressure processing chamber ... Wafer 8 placed in the low-pressure processing chamber ... X stage 9 of the monitoring device, lO ... Motor and ball screw 1 of the drive section of the X stage] ... Y stage 12-3 ... Stage guide block and guide rod 14.15.16...Y stage drive unit motor, ball screw, and nut 17...θ stage 18.19.20...θ stage drive unit motor and pinion and gear 21...laser light source 4, 23...mirror for laser light, 25...lens 26 for laser light...half mirror n...shigarasu...first light detection 29, 30, 31... Motor, ball screw, and arm 32 of the detection position determining section of the first photodetector... Second photodetector U... A/D converter 3
5...Motor control system 36...Microcomputer 37...CRT 38...Abnormality indicator closed 2 Figure 41 Incline 2 匈5 Closed '5 Figure 44 Figure 0123 Hand 5 6 1iJjfr fL'PII: tp tnjll go to S
Figure Closed Figure 6 Figure 8 #'r Order - De7 Figure a Preface Helmet δ Figure Punishment S Diagram

Claims (1)

[Claims] A laser light source, a means for irradiating the laser light emitted from the laser light source to an arbitrary point on a wafer being processed in a dry etching apparatus, and a specific diffracted light among the diffracted lights reflected from the wafer. and an abnormality detection means that determines a contrast from a change in the intensity of the detection light detected by the light detection means and detects an etching abnormality from the magnitude of the contrast. Monitoring device for etched holes and grooves.