JPH02140608A - Measuring instrument for surface shape - Google Patents

Abstract

PURPOSE:To make a measurement in high accuracy over a long term without using a high accuracy scanning mechanism by providing an inclined angle sensor, scanning means, scanning position detecting means, reflection mirror, attitude angle sensor, and correction means. CONSTITUTION:By the inclined angle sensor 14, the inclined angle for the surface of a test sample 12 is detected in the manner of irradiating the test sample with a laser beam and receiving the reflected light. The sensor 14 is moved in the direction vertical to the surface of the test sample 12 by the scanning means consisting of a rail 20, carriage 22, feed screw 24, stepping motor 26, etc. The scanning position for the sensor 14 is detected by the scanning position detecting means consisting of a rotary encoder 28, position sensor 30, position coordinate counter 32, etc. The reflection mirror 34 is arranged on either a side board 18 at the fixed side or the sensor 14. The attitude angle sensor 36 is arranged on the other side either the side board 18 or the sensor 14, by which the attitude angle for the sensor 14 is detected in the manner of irradiating the reflection mirror with the light and receiving the reflected light. The detected inclined angle is corrected by the correction means in the manner of utilizing the detected attitude angle and the detected position.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention Examples of means for solving the problems and their effects Embodiment 1 (Figs. 1 to 4) 2nd Embodiment (Figure 5) 3rd Embodiment (Figure 6) Expanded Effects of the Invention [Summary] It relates to a surface profile measuring device for measuring the shape of the surface of a sample, and is particularly suitable for surface processing of semiconductor wafers, magnetic disks, etc. Regarding the surface profile measuring device that measures the waviness shape of the sample surface, the purpose is to enable high-precision measurement over a long period of time without using a high-precision scanning mechanism. an inclination sensor that detects the inclination of the sample surface by irradiating the sample with reflected light; a scanning device that moves the inclination sensor relative to the stage at right angles to the sample surface; A surface profile measuring device comprising a scanning position detection means for detecting a relative scanning position of a sensor, and measuring the shape of the sample surface using the scanning position and the inclination. a light reflecting means installed on either one of the inclination angle sensors), and a stage installed on the other side of the fixed side or the movable body, which irradiates the light reflecting means with light and moves by receiving the reflected light. or an attitude angle sensor that detects the attitude angle of the inclination angle sensor, and a correction means that corrects the detected inclination angle using the detected attitude angle and the detected position;
and configure it.

[Industrial Field of Application] The present invention relates to a surface shape measuring device for measuring the shape of a sample surface, and particularly relates to a surface shape measuring device for measuring the undulation shape of a planar surface of a sample such as a semiconductor wafer or a magnetic disk. .

[Prior Art] For example, in a magnetic disk device, it is necessary to bring the recording/reproducing head close to the magnetic disk surface by 0.1 to 0.2 μ■, so the amplitude of the waviness on the magnetic disk surface is about the same as this distance. In some cases, the recording/reproducing head may collide with the surface of the magnetic disk and malfunction. Furthermore, if the surface of the semiconductor wafer has large undulations, defocus will occur during circuit pattern exposure, resulting in a decrease in yield. Therefore, it is necessary to control this surface shape during the manufacturing process.

Since the angle of inclination of this waviness is extremely small, usually about 10 to 20 seconds or less, a highly accurate surface shape measuring device is required.

As a surface shape measuring device, for example, Japanese Patent Application Laid-Open No. 62-1276
As disclosed in Publication No. 18, a laser beam from an inclination sensor is irradiated onto the sample surface, and while the inclination sensor is moved at right angles to the irradiation direction, the reflected light is received by the inclination sensor to detect the sample surface. There is a configuration that detects the inclination angle of the sensor, detects the position of the inclination sensor, and measures the waviness of the sample surface using the detected inclination angle and position.

[The problem that the invention tries to solve! g] However, since it is necessary to detect the inclination of the sample surface with high precision, an extremely high-precision scanning mechanism must be manufactured to prevent the attitude of the inclination sensor from changing due to scanning by the inclination sensor, which increases the cost of the device. Becomes high.

In addition, since there is always a sliding part in the scanning mechanism, and it is necessary for the tilt angle sensor to scan smoothly, there is a clearance in this sliding part, which may cause the tilt angle sensor to wobble during scanning, or cause the device to Long-term use causes mechanical deformation that prevents high-precision measurement of surface topography.

SUMMARY OF THE INVENTION In view of these problems, an object of the present invention is to provide a surface shape measuring device that can perform high-precision measurements over a long period of time without using a high-precision scanning mechanism.

[Means for Solving the Problems and Their Effects] In order to achieve this object, the first invention provides an inclination angle that detects the inclination angle of the sample surface by irradiating the sample surface with a laser beam and receiving the reflected light. A sensor, scanning means for moving the inclination sensor perpendicular to the sample surface, and scanning position detection means for detecting the scanning position of the inclination sensor, and detecting the shape of the sample surface using the scanning position and the inclination angle. A surface shape measuring device for measuring a surface profile includes a light reflecting means installed on either the fixed side or the inclination sensor, and a light reflecting means installed on the other side of the fixed side or the inclination sensor. The apparatus includes an attitude angle sensor that receives reflected light and detects an attitude angle of the inclination angle sensor, and a correction means that corrects the detected inclination angle using the detected attitude angle and the detected position.

As shown in Fig. 4, when the surface inclination angle of the sample is θ and the attitude angle of the inclination angle sensor is α, the angle formed by the emitted light of the attitude angle sensor and its reflected light is 2α, and the angle formed by the emitted light of the attitude angle sensor is 2α. The angle between the emitted light and its reflected light is 2(θ+α). Therefore, by dividing the difference between the two by 2, the surface inclination θ can be obtained,
Errors in measuring the surface inclination due to rattling of the scanning mechanism of the inclination sensor during scanning, deformation of the guide guiding the inclination sensor, etc. are eliminated.

Therefore, there is no need to use an extremely high-precision tilt angle sensor scanning mechanism as in the past, and moreover, high-precision measurement over a long period of time is possible.

Even if the attitude angle α and surface inclination θ include offset values, these do not change due to movement of the inclination sensor, so
There is no particular problem in the resulting surface shape since the straight lines are simply superimposed, and if necessary, a well-known electrical offset adjustment device that is included in general measuring instruments may be provided.

The inclination sensor may be moved relative to the sample, and in the second invention, the inclination sensor is fixed, the stage that holds the sample is moved, the attitude angle sensor is installed on one of the fixed side and the stage, and the attitude angle sensor is installed on the other side. A light reflecting means is installed in the stage, and the light emitted from the attitude angle sensor is irradiated onto the reflecting means, and the reflected light is received by the attitude angle sensor to detect the attitude angle of the stage.

The other points are the same configuration as the first invention.

Since the operation of the second invention can be easily understood from the operation of the first invention, the explanation thereof will be omitted.

[Example] Hereinafter, the present invention will be described in detail based on the drawings.

(1) First example FIG. 1 shows the basic mechanical configuration of the surface profile measuring device.

On the stage IO is the sample to be measured, such as a magnetic disk or semiconductor wafer! 2 is placed. Sample I
An inclination sensor I4 is disposed above 2 and facing each other. This tilt angle sensor 14 has a structure similar to that of an optical pickup used in a CD player or the like, except that it does not have various servo control systems and the diameter of the optical spot is larger than that of a normal optical pickup. The laser beam emitted from the inclination sensor I4 is convergently irradiated onto the sample 12, and the reflected light is returned to the inclination sensor 14 and detected by the four-division photodiode in the inclination sensor 14, and the detection signal is sent to the inclination measurement circuit 16. The inclination angle of the surface of the sample 12 with respect to a plane orthogonal to the irradiated laser beam is measured.

A lower end of a side plate 18 is fixed to one end of the stage IO at a right angle to the stage IO, and one end of a rail 20 is fixed to an upper end of the side plate 18 at a right angle to the side plate 18. A carriage 22 is attached to the rail 20 so as to be slidable in its longitudinal direction. A feed screw 24 is threaded through the carriage horn 22 in the sliding direction of the carriage 22. One end of the feed screw 24 is connected to a rotating shaft of a geared chipping motor 26 fixed to the side plate 18. The carriage 22 includes the above-mentioned inclination sensor I4.
is fixed, and when the geared stepping motor 26 rotates the feed screw 24, the inclination sensor 14 determines the laser irradiation direction from the sample! 2 and move in the left and right direction in Figure 1.

The amount of rotation of the geared chipping motor 26 is detected by a rotary encoder 28 whose rotating shaft is connected to the rotating shaft of the geared chipping motor 26 . Further, the initial position of the carriage 22 is detected by a position sensor 30 attached to the rail 20. The output pulse of the rotary encoder 28 is the position coordinate abup down counter 32.
The counted value is cleared by the detection signal of the position sensor 30.

A reflecting mirror 34 is fixed to the rail 20 at right angles to the side surface of the inclination sensor I4 on the side plate 18 side, and an attitude angle sensor 36 is mounted on the side plate 18 opposite to this reflecting mirror 34 with its front axis perpendicular to the reflecting mirror 34. It is fixed.

This attitude angle sensor 36 has a polarizing beam splitter 40.17 in front of the laser diode 38, as shown in FIG.
A collimating lens 44 is arranged via a four-wavelength plate 42,
A two-split photodiode 46 is arranged on the side of the polarizing beam splitter 40. The laser light emitted from the laser diode 38 is collimated by the collimating lens 44, and all of it is collimated by the polarizing beam splitter 40.1.
It passes through the 74-wavelength plate 42 and is reflected by the reflecting mirror 34, and the 1
The light passes through the 74-wavelength plate 42, is reflected by the polarizing beam splitter 40, and is received by the two-split photodiode 461.

The configuration of the attitude angle sensor 36 is similar to the inclination angle sensor 14, but the attitude angle sensor 36 is different in that the inclination angle sensor 14 emits convergent light, whereas the attitude angle sensor 36 emits parallel light.

As shown in FIG. 4, when the surface inclination angle of the sample 12 is θ and the attitude angle of the inclination angle sensor 14 is α, the angle formed by the emitted light of the attitude angle sensor 36 and its reflected light is 2α, and the inclination angle The angle between the emitted light from the sensor 14 and its reflected light is 2(θ
+α). Therefore, by dividing the difference between the two by 2, the surface inclination angle θ is obtained, and errors in measuring the surface inclination angle due to rattling of the carriage 22 with respect to the rail 20 or deformation of the rail 20 during scanning can be eliminated.

Next, the circuit configuration of the surface shape measuring device will be explained based on FIG.

The two-split photodiode 46 is composed of photodiodes 46a and 46b, and a light spot SP is formed on the surface thereof by light irradiation across both photodiodes 46a and 146b. The signals photoelectrically converted by the photodiodes 46a and 46b are amplified by amplifiers 48A and 48B to become signals A and B, respectively. Signals A and B are subtractor 5
0 and an adder 52 to create signals (A-B) and (A+B). These signals are supplied to a divider 54 to form a signal (A − B )/
(A + B) is created and supplied to the attitude angle calculation circuit 56. The signal (A − B)/(A + B) is determined by the attitude angle α and the position coordinate X of the tilt angle sensor 14, and the attitude angle calculation circuit 56
+B) and the position coordinate X to calculate this attitude angle α as a correction value. The attitude angle α is (A − B )/(A
+B) and position coordinates X to create table R.
The output may be caused by addressing the OM. The attitude angle α and the signal (θ+α) output from the inclination measurement circuit 16 are supplied to a subtracter 60 to obtain the inclination O, and then supplied to an integrator 64. The integrator 64 is configured from the position coordinate measuring circuit 32
The surface height is determined by integrating this inclination angle θ. The surface height and position coordinates X are supplied to a recorder 66, and the surface shape of the sample 12 is recorded.

(2) Second Embodiment FIG. 5 shows an optical system of an integrated tilt angle/attitude angle sensor according to a second embodiment.

In this second embodiment, contrary to the first embodiment, the reflecting mirror 34 is a side plate serving as a fixed side! 8, and the attitude angle sensor is integrated with the tilt angle sensor on the moving side.

The tilt angle sensor includes a laser diode 38, a collimating lens 44, a polarizing beam splitter 40, and a quarter wavelength plate 42A.
and an objective lens 68 are arranged in this order with their respective optical axes coincident, and a four-split photodiode 70 is arranged on the side of the polarizing beam splitter 40. Further, the attitude angle sensor includes a 1/4 wavelength plate 42 arranged on the side of the polarizing beam splitter 40 and on the opposite side of the 4-split photodiode 70 via the polarizing beam splitter 40A, and a 2-split photodiode placed above the polarizing beam splitter 40A. 38
are arranged and configured.

In the above configuration, the laser light emitted from the laser diode 38 is collimated by the collimating lens 44 and split into two parts by the polarizing beam splitter 40, one of which passes through the wavelength plate 42A and the objective lens 68, and then onto the sample 12. The reflected light returns to the objective lens 68, is collimated, passes through the 174-wave plate 42A, and the entire luminous flux is reflected by the polarizing beam splitter 40 and sent to the 4-split photodiode 7.
A light spot is formed on 0. The signal on this four-part photodiode 70 is processed to measure the surface inclination of the correction section of sample (2).

On the other hand, the other parallel light beam split into two by the polarizing beam splitter 40 passes through the polarizing beam splitter 40A and the quarter-wave plate 42, and is reflected by the reflecting mirror 34 again! All of the light is reflected by the polarizing beam splitter 40A through the /4 wavelength plate 42, and a light spot is formed on the two-split photodiode 46. The processing of the output signal of the two-split photodiode 46 is the same as in the first embodiment.

(3) Third embodiment FIG. 6 shows the attitude angle measuring optical system of the third embodiment.

On the side of the tilt angle sensor I4, there is a right-angled isosceles triangular prism-shaped reflection, if! 34A and 34B are fixed with their slopes facing each other. On the other hand, an attitude angle sensor 36A is fixed to the side plate 18. This attitude angle sensor 36A includes a laser diode 38, a collimating lens 44 and a
A split photodiode 46 is provided, and the laser light emitted from the laser diode 38 is passed through a collimating lens 44.
It is turned into a V row, reflected, and deflected downward by l134A,
Then, it is returned to the attitude angle sensor 36A by the reflector 34B and the 2
The light is received by the split photodiode 46. Tilt sensor I4
When the attitude angle changes, the output signal value of each photodiode of the two-part photodiode 46 changes, and the attitude angle α is determined in the same manner as in the first embodiment.

(3) Expansion Note that the present invention includes various other modifications.

For example, in each of the above embodiments, a case has been described in which the stage 10 is fixed and the inclination sensor I4 is moved, but conversely, the inclination sensor I4 is fixed and the stage IO is moved, and the attitude angle sensor is used to measure the attitude angle of the stage 10. It may be configured to detect.

Further, the tilt angle sensor may have the configuration described in the above-mentioned publication, and if the light emitted from the tilt sensor is made into a parallel light beam, it can be used as an attitude angle sensor.

[Effects of the Invention] As explained above, according to the surface shape measuring device according to the present invention, there are no problems such as rattling of the scanning mechanism of the inclination sensor or the stage while scanning the inclination angle sensor or the deformation of the guide that guides the inclination sensor or the stage. Since the measurement error of the surface inclination is removed, there is no need to use a conventional extremely high-precision scanning mechanism, and it has the excellent effect of enabling high-precision measurement over a long period of time. This is largely aimed at reducing the cost of equipment, facilitating maintenance, and improving the quality and yield of semiconductor wafers through accurate surface shape inspection.

[Brief explanation of the drawing]

1 to 4 relate to the first embodiment of the present invention, in which FIG. 1 is a mechanical basic configuration diagram of the surface shape measuring device, FIG. 2 is a diagram showing the attitude angle measuring optical system, and FIG. 3 is a diagram showing the attitude angle measuring optical system. A circuit diagram of the surface shape measuring device, and FIG. 4 is an explanatory diagram of surface inclination measurement value correction. FIG. 5 is a diagram showing an optical system of an integrated tilt angle/attitude angle sensor according to a second embodiment of the present invention. FIG. 6 is a diagram showing an attitude angle measuring optical system according to a third embodiment of the present invention. In the figure, IO is the stage 12, the sample 14, the inclination sensor 16, the inclination measurement circuit 20, the rail 22, the carriage 24, the feed screw 26, the geared chipping motor 28, the rotary encoder 30, the position sensor 32, the position coordinate counter 34.34A134B is a reflector 36.36A is an attitude angle sensor 40.40A is a polarizing beam splitter 42.42A is a 1C wavelength plate 44, a collimating lens 46 is a 2-split photodiode 48A, 48B is an amplifier 50, a subtracter 52, an adder 54 is a divider The instrument 56 is an attitude angle calculation circuit 64 is an integrator 66 is a recorder attitude angle λ・1 constant optical system Fig. 2 Surface profile measuring device Fig. 1 Fig. 1 Integrated tilt/attitude angle sensor optical system

Claims (1)

[Claims] 1) An inclination sensor (14) that irradiates a sample surface with a laser beam and receives the reflected light to detect the inclination angle of the sample surface; and the inclination sensor is moved perpendicularly to the sample surface. scanning means (20 to 26); scanning position detection means (20 to 26) for detecting the scanning position of the inclination sensor;
28 to 32), and measures the shape of the sample surface using the scanning position and the tilt angle, the surface shape measuring device comprising: The light reflecting means (34, 34A, 34B) is installed on the other side of the fixed side (18) or the tilt angle sensor (14), and the light reflecting means is irradiated with light and the reflected light is received to measure the tilt angle. Attitude angle sensor (3) that detects the attitude angle of the sensor
6, 36A); and correction means (56, 60) for correcting the detected inclination angle using the detected attitude angle and the detected position. 2) An inclination sensor (14) that irradiates the surface of a sample held on a stage with a laser beam and detects the inclination of the sample surface by receiving the reflected light; and a scanning device that moves the stage perpendicular to the irradiation direction. and a scanning position detection means for detecting a scanning position of the stage, the surface profile measuring device measuring the shape of the sample surface using the scanning position and the inclination angle, the surface profile measuring device comprising: a light reflecting means installed on one side; and an attitude angle sensor installed on the fixed side or the other side of the stage, which irradiates the light reflecting means with light and receives the reflected light to detect the attitude angle of the stage. A correction means for correcting the detected inclination angle using the detected attitude angle and the detected position.