JP2003075125A - Thickness measuring method and thickness measuring device of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness measuring device capable of measuring the wafer thickness and a thickness distribution highly accurately, even in the case of a flexible silicon wafer having the thickness of 30-50 μm or in the case of a wafer on which a transparent protective film is laminated. SOLUTION: In this thickness measuring device 1, a measuring object loaded on a loading stand 36 having sucking function is moved onto a measuring stage A where a floodlight means and a pair of optical sensors 10, 10 equipped with a light receiving means equipped with a two-dimensional light receiving element, and a signal processing means are fixed vertically at a passable distance of the measuring object, and a slit beam is floodlighted onto a detection area of the measuring object from the floodlight means, and reflected light from the detection area is received by the two-dimensional light receiving element (CCD) 20, and the thickness, the height or a step of the measuring object in the detection area are calculated by the signal processing means 29 from a second floodlight distribution existing on the near side of the floodlight means among light-receiving quantity distributions on the two-dimensional light receiving element.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a thickness of 20 to 15
The present invention relates to a wafer thickness measuring device capable of measuring the thickness and thickness distribution of a thin flexible wafer having a thickness of 0 μm, and the thickness and thickness distribution of a wafer portion of a thin wafer whose device pattern is protected by a protective resin film.

[0002]

2. Description of the Related Art In manufacturing a semiconductor substrate, the processed substrate is tested and evaluated before proceeding to the next step in the pre-process and post-process in order to easily find out the cause of the manufacturing failure of the obtained semiconductor substrate. To be done. Measuring the thickness of the wafer is one example. As a wafer thickness measuring device, a capacitance type thickness meter is generally used (Japanese Patent Laid-Open No. 5-67660). In general, the thickness of a wafer (substrate) is the thickness of the center point of the substrate, the thickness at nine defined points on two right-angled intersection lines passing through the center point of the substrate, and four intersection lines passing through the center point of the substrate. The thickness distribution showing the cross-sectional shape formed by is measured.

As the diameter of the substrate increases from 200 mm to 300 mm, it has been attempted to print a device pattern up to the vicinity of the peripheral edge of the substrate, for example, up to 1 mm so that more chips can be collected.

A thin substrate having a thickness of 30 to 150 μm, preferably 50 to 120 μm, such as a smart card and a flash memory card, has been proposed and partially put into practical use. Furthermore, the device surface is covered with a protective resin film, the back surface of the substrate is back-ground (back surface grinding), and after cleaning, the ground surface is further polished (JP-A-2000-254857).
No.) substrate and the back surface of the substrate are back-ground (back surface grinding), and after cleaning, the ground surface is further etched.
1-265869), the thickness of the substrate such as a substrate obtained by pasting a wafer whose device surface is protected by a protective resin film on an adhesive tape attached to the frame, and then peeling off the protective resin film. Have also been attempted to measure.

With the capacitance type thickness meter, it is difficult to measure the thickness in the vicinity of 3 mm at the peripheral portion of the wafer, and for a wafer having a diameter of 300 mm, only the thickness range of 295 to 297 mm width can be measured. Further, it has been found that in a flexible wafer or a wafer to which a resin film is attached, an error easily occurs in the wafer thickness measurement.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have developed an optical sensor, which is also called an optical displacement sensor or an optical thickness sensor, used to measure the thickness of a resin film or paper, for measuring the thickness of a substrate. When various optical sensors were examined for use in measurement, it was an optical sensor having a light projecting means, a light receiving means, and a signal processing means, and the light projecting means was a combination of the light projecting means and the light receiving means. A slit beam that is elongated in the direction perpendicular to the direction is projected onto the detection area of the object to be measured, and the light receiving means is a condenser lens that collects reflected light from the detection area. A two-dimensional light receiving element for receiving light through the condenser lens, and the signal processing means is on the side closer to the light projecting means in the received light amount distribution on the two-dimensional light receiving element of the light receiving means. From the second received light distribution to the detection area That the thickness of the measurement object, the optical sensor (JP 2000-28317 comprising signal processing means and calculates the height or level difference, the 2000-9
7629, 2000-97630, 2000-
No. 93634 and 2000-93635),
For example, Z300-S2 (trade name) of OMRON Corporation
Can measure the thickness of both opaque materials and transparent materials, and can measure the thickness of the wafer up to the vicinity of 0.5 mm (29 mm for a 300 mm wafer).
The present invention provides a thickness measuring device which is designed to have a structure suitable for measuring the thickness of a substrate by using this optical sensor.

[0007]

A first aspect of the present invention is an optical sensor having a light projecting means, a light receiving means and a signal processing means, wherein the light projecting means comprises a light projecting means and a light receiving means. Slit beer that is elongated in the direction perpendicular to the arrangement direction of
And a two-dimensional light receiving means for receiving light through the condenser lens for converging the reflected light from the detection area. And a second light projection distribution on the side closer to the light projection means in the received light quantity distribution on the two-dimensional light receiving element of the light receiving means, and the signal processing means sets the detection area in the detection area. A thickness measuring device for measuring the thickness of a wafer, which is an object to be measured, using an optical sensor, which is a signal processing means for calculating the thickness, height, or step of an object to be measured. The apparatus is a measurement stage in which the pair of optical sensors are vertically fixed to a support erected on a moving table provided on the base of the thickness measuring apparatus with a distance that allows the object to be measured to pass therethrough,
A service for moving the moving stage of the measuring stage in the front-back direction.
A disk having a moving mechanism having a bob function, a support pipe having upper and lower fluid passages provided upright in front of the measuring stage, and a fluid passage communicating with the fluid passage of the support pipe at an upper flange portion of the support pipe. -Shaped lower plate is fixed, and a cylindrical support body is fixedly provided on the upper surface of the disk-shaped lower plate, and at least eight notch portions through which the optical sensor can pass are fixedly provided. A disk-shaped frame plate having a passage chamber is fixed to the upper portion of the cylindrical support, and the light projected from the light-projecting section of the optical sensor in the disk-shaped frame plate is the object to be measured. The suction member is laid so that at least four grooves intersect each other at the axis of the disc-shaped frame plate so that the reflected light reaches the optical sensor. The disc-shaped lower plate fluid passage and the disc-shaped frame plate fluid passage chamber are formed by pipes. Through so, the object to be measured vacuum air supply pipe and the compressed air supply pipe to the fluid passage is a tube having a switching valve that is switched is coupled to the support tube mounted stearate -
(However, the axis of the support tube, the axis of the disk-shaped lower plate, the axis of the cylindrical support, and the axis of the disk-shaped frame plate that form the stage for mounting the object to be measured are the same. Existing on a vertical line), and a rotation mechanism having a servo function for horizontally rotating the support tube, and a wafer thickness measuring device.

A second aspect of the present invention is an optical sensor having a light projecting means, a light receiving means and a signal processing means, wherein the light projecting means is arranged in a direction in which the light projecting means and the light receiving means are arranged. A slit beam, which is elongated in the vertical direction, is projected onto a detection area of an object to be measured, and the light receiving means includes a condenser lens that collects reflected light from the detection area, and the condenser lens. And a two-dimensional light receiving element for receiving light via the light receiving means, wherein the signal processing means includes a second light emitting element located on a side closer to the light emitting means in a light receiving amount distribution on the two-dimensional light receiving element of the light receiving means. A mounting base that is supported by a support that can be moved back and forth and rotated using an optical sensor that is a signal processing means that calculates the thickness, height, or step of the measured object in the detection area from the light distribution. Place the object to be measured on and measure it from the light emitting part of the optical sensor. The light is projected to the detection area of the elephant, the reflected light is received by the two-dimensional light receiving element, and it is in the detection area from the second light distribution which is closer to the light projecting means in the received light amount distribution. The present invention provides a wafer thickness measuring method, characterized in that the thickness of an object to be measured is calculated by a signal processing means.

Since the wafer to be measured is placed on the mounting stage and fixed with a vacuum, even if the object to be measured is a thin wafer of 30 to 150 μm, it does not warp. The thickness can be measured with high accuracy. Further, since the mounting base of the object to be measured on the mounting stage is rotationally driven for alignment, and the measuring stage is linearly driven with a servo mechanism, the positioning can be automated and can be performed in advance. ,
If the position where the optical axis of the optical sensor coincides with the axis of the mounting base of the object to be measured is defined as 0 point, the center point position of the wafer in the thickness distribution calculated by the signal processing means of the optical sensor is 0
Since the points coincide with each other, data processing becomes easy.

Further, after the wafer thickness is measured, the wafer can be easily removed from the mounting stage by supplying pressurized air to the fluid passage chamber under the object mounting base.

[0011]

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail below with reference to the drawings. 1 is a plan view of a wafer thickness measuring apparatus equipped with the optical sensor of the present invention, FIG. 2 is a front view of the wafer thickness measuring apparatus, FIG. 3 is a side view of the wafer thickness measuring apparatus, and FIG. 5 is a block diagram showing the configuration of an optical sensor used in FIG. 5, FIG. 5 is a diagram of an application menu of the optical sensor, and FIG. 6 is a diagram showing the distance between the optical sensor and an object to be measured and the relationship between each part. FIG. 7 shows a state in which the thickness of a back-ground wafer is measured using two optical sensors, and FIG. 8 shows a transparent protective resin film attached to the device surface of the back-ground wafer. Two-dimensional light receiving element C of optical sensor
It is a figure which shows the received light amount distribution represented on CD.

The wafer thickness measuring apparatus 1 of the present invention mainly comprises a measuring stage A having a pair of optical sensors, a measuring object mounting stage B, and a measuring stage mounting the measuring object mounting stage. A front-rear moving mechanism C having a servo function of moving to the stage side or moving the measurement stage away from the measurement target mounting stage side, and a servo for rotating the measurement target mounting stage. The rotation mechanism D has a function.

As shown in FIGS. 1, 2 and 3, the measuring stage A is two-dimensionally mounted on a supporting frame 4 fixed to a column 3 standing on a moving table 50 provided on the base 2. A structure is adopted in which the optical sensors 10 and 10 equipped with CCDs are vertically fixed with a distance that allows an object to be measured of the thickness measuring device to pass therethrough.

In the stage B for mounting the object to be measured, a support pipe 31 having upper and lower fluid passages 31a is erected upright through a guide 30 having a cylindrical hollow at the center, and is supported by an upper flange portion 31b of the support pipe. A disc-shaped lower plate 32 having a fluid passage 32a (32b is a plug) communicating with the fluid passage 31a of the pipe is fixed, and a notch through which the optical sensor 10 can pass on the upper surface of the disc-shaped lower plate. Cylindrical support 33 is fixedly provided with at least eight portions 33a, and a disk-shaped frame plate 35 having a fluid passage chamber 35a at the bottom is fixed to the upper part of the cylindrical support, The light projecting portion (light projecting element) 1 of the optical sensor 10 is provided in the disk-shaped frame plate 35.
The light projected from 3 reaches the object to be measured, and the reflected light thereof reaches the two-dimensional light receiving element CCD 20 of the optical sensor 10 so that at least four grooves 36a, 36a ... Eight suction members 36b, 36b ... are laid so as to be formed so as to intersect with each other at the axis O, and the measured object mounting base 3 is provided.
6, the fluid passage 32a of the disc-shaped lower plate and the fluid passage chamber 35a of the disc-shaped frame plate 35 are connected by the pipes 34, 34, and the depressurized air supply pipe 3 is connected to the fluid passage 31a of the support pipe.
Switching valve 3 for switching between 7 and pressurized air supply pipe 38
The tube 40 having the structure 9 is connected via a rotary joint 41.

The axis of the support tube which constitutes the object mounting stage of the object B to be measured, the axis of the disk-shaped lower plate, the axis of the cylindrical support and the disk. The axis of the frame plate lies on the same vertical line Z.

Examples of the material of the suction member 36b forming the object mounting base 36 include a resin sintered body such as poly (tetrafluoroethylene), poly (trifluoromonochloroethylene), nylon, polyacetal or polysulfone. To be This is a molded product having fine voids communicating with each other and having a smooth surface.

Therefore, if the fluid passage 31a of the support pipe 31 is decompressed, the object to be measured placed on the object to be measured mounting base 36 is decompressed (vacuum) and fixed on the mounting base 36. On the contrary, if pressurized air is supplied to the fluid passage 31a of the support tube 31, the measured object placed on the measured object mounting base 36 floats. These eight suction members 36b
Are four sections intersecting with a gap of 0.5 to 3 mm so that the light emitted from the light projecting element of the optical sensor enters the object to be measured and the reflected light reaches the light receiving element of the optical sensor. Is laid so as to form the linear groove 36a.

In order to make the axis O of the wafer to be mounted easily coincide with the axis Z of the mounting table 36, the notch or notch or the register mark (mark) position provided on the wafer is coded to mount the wafer. Therefore, a registration mark (mark) may be provided on the upper surface of the disc-shaped frame plate 35. Further, a wafer centering device (positioning mechanism) may be attached to the mounting stage B.

The moving mechanism C moves the measuring stage A to the side B of the object to be measured or moves the measuring stage A away from the side B of the object to be measured. The moving mechanism C has a structure in which a guide member 50a provided on the lower surface of the moving table 50 moves on rails 51, 51 provided on the base 2. In FIGS. 1, 2 and 3, the screw body 53 screwed into the ball screw 52 is the fixing member 5.
4 is fixed to the lower surface of the moving table 50, and the servo motor 55
The pulley provided on the shaft of the ball screw receives the rotational drive of the ball screw 52 to rotationally drive the ball screw 52 to move the movable table 50 in a linear position. The driving mechanism of the moving table 50 may be driven by a linear motor having a linear servo mechanism or by a hydraulic cylinder.

The mounting base 36 of the stage B for mounting the object to be measured.
In the rotating mechanism D having a servo function for rotating the shaft, a pulley 62 provided on a shaft 60a of a motor equipped with a servo mechanism 61 that outputs a pulse signal for detecting a position drives the rotation of the shaft. The belt 63 transmits the power to the pulley 43 provided below the support tube 31 of the mounting stage A, so that the structure is performed.

As shown in FIGS. 4 and 7, the optical sensor 10 is an optical sensor having a light projecting means 11, a light receiving means 17 and a signal processing means 25. The light projecting means 1
Reference numeral 1 is for projecting an optical beam onto the detection area of the object to be measured 18, which includes a light emitting element 13 such as a light emitting diode or a laser diode driven by a drive circuit 12, and a light emitting element 13. The light emitted from the optical element is converted into parallel light 14, and the light projecting means 11
It has a slit plate 15 and a cylindrical lens 16 each having a slit elongated in a direction (Y-axis direction) perpendicular to the arrangement direction (X-axis direction) with the light receiving means 17. The cylindrical lens 16 further converges the narrow slit-shaped light passing through the slit of the slit plate 15 in the X-axis direction.

The light receiving means 17 has a condenser lens 19 for condensing the reflected light from the detection area, and a two-dimensional light receiving element 20 for receiving light through the condenser lens, for example, a CCD and a CCD driver 21. Is. Two-dimensional light receiving element 20
Is not limited to CCD, and other solid-state imaging device such as BBD or CPD or vidicon imaging tube may be used. In the embodiment, a CCD having 256 pixels × 256 pixels was used.

A CCD driver 21 is connected to the CCD 20 as shown in FIG. 4, and each pixel signal is transferred to the CCD driver 2.
Read by 1. The read signal is amplified by the amplifier 22 and is A / D converted by the A / D converter 23.
It is D-converted and transferred to the image memory 24. The image memory 24 stores the transferred image signal for one screen. The arithmetic processing means 25 is connected to the image memory 24, and the arithmetic processing means 25 has a register and a microcomputer for calculating the peak position, and the peak position is calculated based on the data of the image memory 24. Object to be measured 18
The distance to and the thickness of the detected object of the object to be measured are detected.

A buffer amplifier 26 for outputting a video signal to the outside and a video output terminal 27 are connected to the output terminal of the amplifier 22. These amplifiers 22, A /
D converter 23, image memory 24, and arithmetic processing means 2
5. The buffer amplifier 26 and the signal processing means 29 for calculating the distance to the object to be measured 18, the thickness of the detected object of the object to be measured, and the like, based on the received light amount distribution obtained by the light receiving element 20. .

Image display means 28 is provided at the video output terminal 27.
Is connected, and the operator displays the CCD 2 on the screen of the image display means 28.
The monitor image output from 0 can be seen.

The light receiving element CCD 20 periodically repeats the charge storage time and the charge transfer time, and the charge accumulated during the charge storage time is transferred to the image memory 24. Therefore, the pulse width of the light projection time should be changed. The light emission level (sensitivity) can be adjusted by. Sensitivity adjustment is performed at a high level where the output is linearly obtained within the dynamic range of the CCD, so that the peak position can be accurately detected.

If the peak position can be detected, the position corresponds to the distance to the object to be measured. Therefore, if the distance to the object to be measured is short, the peak is monitored by the image display panel 28. The position moves to the left, and to the right if the distance is short. Therefore, the optical sensor 10 is attached so that when the object to be measured 18 is placed at a predetermined position on the mounting table 36, the reflected light thereof is almost picked up by the monitor at the center of the image. In other words, the measured object 18
The sensor head is fixed so that is at the substantially central position of the CCD. The fact that the light receiving state of the CCD can be confirmed from the image display panel 28 means that when the detected object changes, whether or not the reflected light at a normal level is obtained, and whether or not the mounting position of the optical sensor is appropriate. I can confirm.

If the peak position can be detected, the position corresponds to the distance to the detected object, so that the distance from the peak position to the detected object can be calculated. Fig. 5 shows optical sensor Z300-S2 (trade name) manufactured by OMRON Corporation.
An example of the application menu of is shown. In addition to the distance to the detection object, the step, the thickness of the opaque object, the thickness of the transparent body, the depth of the hole provided in the detection object, the height of the protrusion, and the like can be measured.

FIG. 6 shows an example of measuring the distance to the surface of the opaque detection object 18. Let K be the distance from the center of the light-receiving lens 19 to the projection axis and L be the distance from the intersection of the projection axis and this line segment to the detection object 18, and project from the center of the lens 19 to the CCD. Let D be the line segment parallel to the axis. Also, from the intersection of CCD 20 and line segment D, CCD 2
Let J be the distance to the end of 0 and E be the distance from the end to the imaging position of the reflected light. Since the triangle formed by the reflected light axis, the projected light axis, and the line segment K, and the triangle formed by the reflected light axis, the line segment D, and the line segment connecting these on the light receiving surface of the CCD 20 are similar,
The following relational expression holds. L: K = D: J-E Therefore, the distance L to the detection object 18 is L = K / D /
It is calculated by (JE). In the optical sensor 10, since the distances between the line segments K, D, and J are constants, the distance L from the optical sensor to the detection object 18 is calculated based on E determined by the light reception distribution of the CCD (Japanese Patent Laid-Open No. 2000-2000). -28
317). When the distance from the intersection of L and K to the front surface of the case of the optical sensor 10 is Q, the distance to the object is considered to be LQ.

Therefore, if the distance L ₁ from the optical sensor 10 to the mounting base 36 is known, the thickness t of the object to be measured 18 is measured.
Is calculated as L ₁ -L. The distance L ₁ from the optical sensor 10 to the mounting table 36 can be measured by the optical sensor 10.

FIG. 7 shows an example in which the object to be measured 18 is a device substrate whose back surface is ground. The back surface grinder 18 in which the device surface of the opaque silicon substrate 18a is covered with the transparent protective resin film 18b is placed on the mounting base 36 of the mounting stage B so that the protective resin film 18b side faces upward. Since the protective resin film 18b of the object to be measured 18 is a transparent body, reflected light is simultaneously obtained from the front surface and the back surface thereof, and two parallel peak images shown in FIG. 8 are displayed on the image display panel 28. To be done. Based on the distance between the light receiving patterns, the thickness t of the transparent resin film 18b
₂ is calculated (Japanese Patent Laid-Open Nos. 2000-28317 and 20).
No. 00-97635).

When the object 18 to be measured is a transparent body, the refractive index of the transparent body and the refractive index of air are different. Therefore, in order to display the thickness of the transparent body more accurately, the refractive index n of the transparent body to be measured is displayed. Is known, the value of the refractive index n is stored in advance in the memory of the microcomputer of the arithmetic processing means 25, and the measured thickness t ₂ is corrected (calibrated) to obtain the following equation. The actual thickness t ′ ₂ shown in (1) is calculated (see Japanese Patent Laid-Open No. 2000-28317). t ′ ₂ = t ₂ x {(n ² −sin ² θ) / (1-sin
² θ)} ^{1/2 Further} , the thickness of the transparent body made of the same material having a known thickness T ₀ is measured by the optical sensor 10, and the correction coefficient α is calculated from the measurement result T _i by the formula α = T ₀ / T _i The value α is obtained as a calibration coefficient and is stored in the recording unit of the microcomputer, and the arithmetic processing unit 24 multiplies the thickness t ₂ measured by the optical sensor 10 by the correction coefficient α to obtain the transparent body 18b. The actual thickness may be calculated (calibration).

Opaque silicon substrate 1 of backside grinding machine 18
8a thickness t₁Is the thickness t of the backside grinding machine 18.₀More transparent
Resin film thickness t '_TwoSubtract (t₁= T₀−
t ' _Two) Is required. Thickness of backside grinder 18
t₀Is the distance between the surface of the mounting table 36 and the upper optical sensor 10.
Distance L₀From the transparent resin film surface and the upper optical sensor
It is obtained by subtracting the distance L between the sensors 10.

The optical sensor 10 is commercially available from OMRON Corporation as an optical sensor Z300-2S (trade name). A procedure for measuring the thickness of the backside grinding substrate 18 using the thickness measuring device 1 shown in FIGS. 1, 2 and 3 equipped with two optical sensors Z300-2S will be described below.
The origin return is performed at the position of 0.000 mm where the optical axis of the optical sensor coincides with the axis G of the mounting base 36 of the mounting stage B. Further, the coordinate of the rotation axis G of the mounting table 36 of the mounting stage B is 0.000 degree.

The axis Z of the mounting stage B and the object to be measured 1
An object to be measured (reference detection body) 18 having a known transparent resin film thickness is placed on the mounting table 36 so that the axes of 8 coincide with each other, and the fluid passage 31a of the support tube 31 is vacuum-sucked. The object to be measured 18 is aligned, and then the ball screw 52 is rotationally driven by the servo motor 55 to move the movable table 50 forward to the mounting stage B side, and the optical axis of the optical sensor is changed. It is stopped at a position that coincides with the axis G of the mounting base 36 of the mounting stage B (the position of the measurement stage A shown by a virtual line in FIG. 1).

After turning on the power and selecting the setting from the menu of the optical sensor 10 displayed on the image display panel 28, the upper optical sensor 10 selects the menu of the transparent body thickness and then the CCD.
Any of the modes (1/10/60), for example mode 1
Select 0, select the data transfer rate as normal, and set the measurement area (measurement area for the surface, then the lower right position of the measurement area, upper left position, lower right position of the measurement area for two surfaces). Set.

Then, when the screen for setting the calibration value in consideration of the refractive index of light is displayed, press the ENT key, enter the position of the front surface, and press the ENT key to display two surfaces (the back surface of the transparent resin film). The measurement screen of is displayed and the measurement is performed on the two surfaces. Next, enter the thickness of the transparent resin film and press the ENT key to display the execution confirmation screen, the calibration is set, the screen for confirming the setting contents is displayed, and after confirming the setting contents, select registration.
After confirming the setting contents, OU the measured values on the front and back sides
The setting is completed by assigning it to T1 and OUT2.

For the optical sensor 10 in the lower stage, after selecting the thickness menu, one of the CCD modes (1/10/60), for example, the mode 10 is selected, and the data transfer rate is set.
After selecting the circle, setting the measurement area, inputting the thickness, and confirming the settings, set the measured value of sensor 0 to OUT1.
Then, the measurement value of the sensor 1 is assigned to OUT2 and the setting is completed.

Then, the ball screw 52 is attached to the servomotor 5
In step 5, the rotary table 50 is driven to rotate in the opposite direction, and the movable table 50 is moved backward from the mounting stage B side to the measurement stage A side shown by the solid line in FIG. After releasing the vacuum of the fluid passage 31a of the measurement support tube 31 to return to atmospheric pressure, the fluid passage 31a
Pressurized air is instantaneously supplied into a to raise the reference detection body 18 used for the measurement of the calibration, and the reference detection body 18 is manually removed from the mounting base 36.

The object 18 to be measured whose thickness is to be measured is mounted on the mounting base 36 with the transparent resin film side facing upward so that the axis Z of the mounting stage B and the axis 18 of the object 18 to be measured coincide with each other.
Then, the fluid passage 31a of the support tube 31 is vacuum sucked to align the object 18 to be measured, and then the ball screw 52 is rotationally driven by the servo motor 55 to move the movable table 50. Is moved forward to move the thickness measuring stage A to the mounting stage B side, and is stopped at a position where the optical axis of the optical sensor coincides with the axis G of the mounting base 36 of the mounting stage B. .

When measurement is selected from the menu of the optical sensor 10 displayed on the image display panel 28, according to the measurement program stored in the storage unit of the microcomputer,
The thickness of the object to be measured 18 is automatically measured and calculated. First, the ball screw 52 is rotationally driven by the servo motor 55 to further move the thickness measuring stage A forward,
The optical axis of the optical sensor is slightly outside the rear side outer periphery of the object to be measured 18 mounted on the mounting base 36 of the mounting stage B (1-2
mm), the movable table 50 is stopped, and then the ball screw 5 is moved in accordance with the measurement area defined in the setting menu.
2 is rotated by a servo motor 55 to measure stage A
Are sequentially moved backward, and when the optical axis of the optical sensor is slightly before (1 to 2 mm) from the outer circumference of the front side of the object to be measured 18, the moving table 50 is stopped, and the thickness of one line 300 mm width is measured, Recorded and displayed.

Next, the ball screw 52 is attached to the servomotor 5
5, the measurement stage A is driven to rotate and further moved backward from the mounting stage B side to the measurement stage side A shown by the solid line in FIG. 1 and stopped, and the support tube 31 is turned into a servo motor. 60 in 9
Turn 0 degrees clockwise and stop.

Then, in the same manner as described above, the ball screw 52 is rotationally driven by the servo motor 55, and the thickness measuring stage A is obtained.
Side is moved forward to the mounting stage B side, and the optical axis of the optical sensor is slightly outside the rear side outer periphery of the object to be measured 18 mounted on the mounting base 36 of the mounting stage B (1-2 mm). ), The ball screw 52 is rotationally driven by the servomotor 55 in accordance with the measurement area defined in the setting menu, and the measurement stage A is sequentially moved forward to move the optical sensor. When the optical axis of (1) is slightly before (1 to 2 mm) from the outer circumference of the front side of the object to be measured 18, the measurement is stopped, and the thickness of another line 300 mm width orthogonal to the above line is measured, recorded, and displayed.

Next, the ball screw 52 is attached to the servomotor 5
At 5 it is rotated and driven so as to move away from the mounting stage B side, and is further moved backward to the measurement stage side shown by the solid line in FIG. 1 and stopped.

By this operation, the center thickness of the wafer to be measured and the position thickness (TV9) of the nine wafers are measured. When the cross section of the wafer (the cross-sectional shape of the four points on the wafer) is also programmed, the support 31
The mounting base 3 can be rotated by rotating the
The object to be measured 18 on 6 is rotated by 45 degrees in the counterclockwise direction, and then the ball screw 52 is rotationally driven by the servo motor 55 in the same manner as described above to mount the thickness measuring stage A. The object to be measured 18 is moved forward to the stage B side, and the optical axis of the optical sensor is mounted on the mounting base 36 of the mounting stage B.
When it is slightly outside (1 to 2 mm) from the outer periphery of the rear side, it is stopped, and then the ball screw 52 is rotationally driven by the servo motor 55 according to the measurement area defined in the setting menu, and the measurement step is performed. J is moved forward sequentially, and the optical axis of the optical sensor is slightly in front of the front outer periphery of the object to be measured 18 (1-2
mm), the measurement is stopped, and the thickness of one line 300 mm width different from the above line is measured, recorded and displayed.

Then, the ball screw 52 is attached to the servomotor 5
In step 5, the measurement stage A is moved backwards away from the mounting stage B side, and when the measurement stage A position shown by the solid line in FIG. 1 is reached, the moving table 50 is stopped. Support 3
1 is rotated 45 degrees counterclockwise to rotate the object to be measured 18 on the mounting base 36 90 degrees clockwise, and then the ball screw 52 and the servomotor 55 are rotated in the same manner as described above. Is rotated to move the thickness measuring stage A side forward, and the optical axis of the optical sensor is slightly outside the rear side outer periphery of the object to be measured 18 placed on the mounting base 36 of the mounting stage B ( (1 to 2 mm), and then the ball screw 52 according to the measurement area defined in the setting menu.
Is rotated by a servo motor 55 to sequentially move the measurement stage A forward so that the optical axis of the optical sensor is the object to be measured 1.
When it is slightly before (1 to 2 mm) from the front outer circumference of 8, it is stopped, and another line 300 mm orthogonal to the above line is 300 mm.
The width and thickness are measured and recorded and displayed. Then,
The ball screw 52 is rotationally driven by the servo motor 55 to move the measuring stage A backward to the measuring stage A position shown by the solid line in FIG. 1 and stop. This completes the measurement of the cross section. The program joins the screens at the rotation center O of the object to be measured and displays the average shape of the wafer.
The result can also be output by a printer.

The method of measuring the thickness of each of the laminate of the transparent body and the opaque body as the object to be measured has been described above, but the thickness is measured even if the object to be measured is the transparent body alone or the opaque body alone. Of course you can. Furthermore, it is needless to say that the thickness of each transparent pair can be obtained from the peak-to-peak distance of each peak image even in the case of a multi-layered laminate of transparent bodies (JP-A 2000-2).
8317).

In the thickness measuring method of the embodiment, an example of moving the measuring stage A straight forward and backward to bring it closer to the mounting stage B side or moving it away from the mounting stage B side has been described. The measurement stage A may be set at a fixed position, and the mounting stage B may be moved linearly back and forth to approach the measurement stage A side, or may be moved back and forth away from the measurement stage A side.

[0049]

Since the thickness measuring device 1 of the present invention measures the thickness of the object 18 to be measured by vacuum-fixing the object 18 to be measured on the mounting table 36 having a flat surface, the object 18 is flexible. Even if there is, the object to be measured does not bend on the surface of the mounting table which is the reference surface, so that the thickness can be measured with high accuracy.

The optical sensor 10 is a two-dimensional light receiving element C.
Since the detection points are divided into 10 or 60 lines by using the CD for measurement and the averaged data for each pixel can be output, there is no fluttering of the data. An optical sensor using a one-dimensional light receiving element CCD outputs the flutter on the CCD as it is. Further, the conventional light beam is applied to the detection region, and the distance to the object to be measured is detected based on the light receiving position of the reflected light obtained by the position detection element (PSD) arranged at a certain distance from the detection region. In the optical displacement sensor, when the measured object is a transparent body, the PSD erroneously recognizes the position of the reflected light due to the reflected light from the back surface or the background (here, the mounting table or the silicon wafer) in addition to the reflected light on the front surface. Therefore, it was not possible to measure the accurate distance to the surface,
The thickness measuring device using the two-dimensional light receiving element CCD of the present invention can detect the reflected light on the front surface and the back surface separately, and can measure the thickness with high accuracy.

[Brief description of drawings]

FIG. 1 is a plan view of a wafer thickness measuring apparatus including an optical sensor of the present invention.

FIG. 2 is a front view of a wafer thickness measuring device.

FIG. 3 is a side view of a wafer thickness measuring device.

FIG. 4 is a block diagram showing a configuration of an optical sensor used in the present invention.

FIG. 5 is a diagram of an application menu of the optical sensor.

FIG. 6 is a diagram showing a distance between an optical sensor and an object to be measured and a relationship between respective parts.

FIG. 7 is a diagram showing a state in which the thickness of a wafer whose back surface is ground is measured using two optical sensors.

FIG. 8 is a diagram showing a received light amount distribution represented by a transparent protective resin film attached to a device surface of a wafer whose back surface has been ground, on a two-dimensional light receiving element CCD of an optical sensor.

[Explanation of symbols]

1 Thickness meter 2 bases A measurement stage B mounting stage C Front-rear transfer mechanism D mounting platform rotation mechanism 10 Optical sensor 18 Object to be measured 20 Two-dimensional light receiving element 31 Support tube 36 mounting base 50 mobile platform

Continued front page    F term (reference) 2F065 AA02 AA06 AA20 AA22 AA24                       AA25 AA30 BB02 BB03 BB22                       BB23 CC02 CC19 FF04 FF09                       FF41 FF61 FF65 FF67 GG06                       GG07 GG12 HH03 HH05 HH12                       JJ03 JJ05 JJ08 JJ19 JJ26                       LL08 LL28 MM03 MM04 NN01                       NN15 PP12 PP22 QQ03 QQ24                       QQ26 QQ29 QQ31 QQ42 RR06                       RR09                 4M106 AA01 BA10 CA48 CA50 DH03                       DH12 DH31 DH38 DJ02 DJ04                       DJ06 DJ20 DJ21

Claims (2)

[Claims] 1. An optical sensor having a light projecting means, a light receiving means and a signal processing means, wherein the light projecting means is elongated in a direction perpendicular to a direction in which the light projecting means and the light receiving means are arranged. The slit beam is projected onto the detection area of the object to be measured, and the light receiving means receives the reflected light from the detection area through a condenser lens and 2 through the condenser lens. A two-dimensional light receiving element, and the signal processing means detects from the second light projecting distribution on the side closer to the light projecting means in the received light amount distribution on the two-dimensional light receiving element of the light receiving means. A thickness measuring device for measuring the thickness of a wafer, which is an object to be measured, using an optical sensor that is a signal processing means for calculating the thickness, height, or step of the object to be measured in a region, The thickness measuring device should be placed on a moving table installed on the base of the thickness measuring device. And said pair of optical type object to be measured a sensor support is fixed vertically at a distance that can pass through the measurement stearyl - di, the measurement stearyl - Sa moving the moving stand di in the longitudinal direction -
A moving mechanism having a bob function, a disc having a support pipe having upper and lower fluid passages standing upright in front of the measuring stage, and a fluid passage communicating with the fluid passage of the support pipe at an upper flange portion of the support pipe. -Shaped lower plate is fixed, and a cylindrical support body is fixedly provided on the upper surface of the disk-shaped lower plate, and at least eight notch portions through which the optical sensor can pass are fixedly provided. A disk-shaped frame plate having a passage chamber is fixed to the upper portion of the cylindrical support, and the light projected from the light-projecting section of the optical sensor in the disk-shaped frame plate is the object to be measured. The suction member is laid so that at least four grooves intersect each other at the axis of the disc-shaped frame plate so that the reflected light reaches the optical sensor. The disc-shaped lower plate fluid passage and the disc-shaped frame plate fluid passage chamber are formed by pipes. A stage for mounting an object to be measured (however, a stage for mounting an object to be measured is connected to a pipe having a switching valve for switching between a depressurized air supply pipe and a pressurized air supply pipe in a fluid passage of a support pipe. The axis of the support tube, the axis of the disk-shaped lower plate, the axis of the cylindrical support, and the axis of the disk-shaped frame plate that form the z-axis are on the same vertical line.), And And a rotation mechanism having a servo function for horizontally rotating the support tube. 2. An optical sensor having a light projecting means, a light receiving means and a signal processing means, wherein the light projecting means is elongated in a direction perpendicular to a direction in which the light projecting means and the light receiving means are arranged. The slit beam is projected onto the detection area of the object to be measured, and the light receiving means receives the reflected light from the detection area through a condenser lens and 2 through the condenser lens. A two-dimensional light receiving element, and the signal processing means detects from the second light projecting distribution on the side closer to the light projecting means in the received light amount distribution on the two-dimensional light receiving element of the light receiving means. Using an optical sensor that is a signal processing means that calculates the thickness, height or step of the measured object in the area, mount the measured object on a mounting base that is supported by a support that can be moved back and forth and rotated. On the detection area of the object to be measured from the light emitting part of the optical sensor. Then, the reflected light is received by the two-dimensional light receiving element, and the thickness of the object to be measured in the detection area is determined from the second light projection distribution on the side closer to the light projecting means in the received light quantity distribution. A method for measuring the thickness of a wafer, which is calculated by a signal processing means.