JP7364217B2 - polishing equipment - Google Patents

Description

The present invention relates to a polishing device.

Conventionally, silicon wafers sandwiched between the upper and lower surface plates, wafers with oxide films formed on the surface, SOI wafers, SiC wafers, other semiconductor wafers, glass wafers, quartz glass wafers, crystal wafers, sapphire 2. Description of the Related Art Polishing apparatuses for polishing the surfaces of workpieces such as wafers and ceramic wafers are known (for example, see Patent Document 1). This polishing apparatus has a thickness measuring device that measures the shape of the workpiece being polished in real time through a hole that passes through the upper surface plate. This thickness measuring device irradiates a workpiece being polished with measurement light and measures the shape of the workpiece based on the reflected light reflected from the front and back surfaces of the workpiece.

Japanese Patent Application Publication No. 2015-47656

By the way, in the shape measuring device of the conventional polishing apparatus, the light intensity of the irradiation light, which is the measurement light immediately before being irradiated onto the workpiece, is set to be constant when measuring the shape of the workpiece. On the other hand, the materials of the workpieces vary as described above, and the impurity concentrations also differ from workpiece to workpiece. Therefore, depending on the material of the workpiece, impurity concentration, etc., it may not be possible to obtain reflected light suitable for measuring the shape of the workpiece, and the shape of the workpiece may not be measured appropriately.

The present invention has been made in view of the above problem, and an object of the present invention is to provide a polishing apparatus that can appropriately measure the shape of a workpiece regardless of the material, impurity concentration, etc. of the workpiece.

In order to achieve the above object, the polishing apparatus of the present invention rotates the workpiece and the surface plate relative to each other, and polishes the workpiece with a polishing pad attached to the surface plate. It includes a polishing machine body that polishes a workpiece, and a shape measuring device that measures the shape of the workpiece based on reflected light obtained by reflecting measurement light irradiated onto the workpiece from the front and back surfaces of the workpiece. Furthermore, the shape measuring instrument detects interference signals between the laser light source that emits the measurement light, the first reflected light obtained by reflecting off the surface of the workpiece, and the second reflected light obtained by reflecting off the back surface of the workpiece. It has a measuring part that links the reflected intensity, which is the strength of the interference signal, and the resistivity of the workpiece, and by comparing the reflected strength information input from the measuring part with the database, the resistance of the workpiece can be determined. The resistivity recognition unit includes a resistivity recognition unit that recognizes the resistivity, and a light amount control unit that controls the amount of irradiation light that is the measurement light immediately before irradiating the workpiece based on the resistivity recognized by the resistivity recognition unit. .

The shape measuring device included in the polishing apparatus of the present invention controls the amount of irradiation light, which is measurement light immediately before irradiating the workpiece, based on the resistivity of the workpiece. Here, the resistivity of the workpiece differs depending on the material of the workpiece, impurity concentration, etc. Therefore, by controlling the amount of irradiation light based on the resistivity of the workpiece, the amount of irradiation light can be switched depending on the material, impurity concentration, etc. of the workpiece. Therefore, the shape of the workpiece can be appropriately measured regardless of the material, impurity concentration, etc. of the workpiece.

1 is an overall configuration diagram schematically showing a polishing apparatus of Example 1. FIG. FIG. 3 is an explanatory diagram showing the positional relationship between a sun gear, an internal gear, and a carrier plate in Example 1. FIG. 1 is a block diagram showing the configuration of a shape measuring instrument according to a first embodiment. FIG. FIG. 2 is an explanatory diagram showing an example of a cross-sectional shape line drawn by the shape measuring device of Example 1. FIG. 2 is a table showing the relationship among the voltage applied to the light amount control unit, the amount of light transmission of measurement light, the amount of attenuation, and the amount of irradiation light in the polishing machine of Example 1. 5 is a flowchart showing the flow of workpiece shape measurement processing executed in the polishing apparatus 1 of the first embodiment. FIG. 3 is an explanatory diagram showing an example of reflection intensity detected when a high resistance workpiece is irradiated with measurement light. FIG. 3 is an explanatory diagram showing an example of reflection intensity detected when a low resistance workpiece is irradiated with measurement light. FIG. 3 is an explanatory diagram showing an example of reflection intensity detected when a high resistance workpiece is irradiated with measurement light from a laser light source with degraded optical output performance. FIG. 7 is a diagram showing an example of workpiece thickness information drawn when a high-resistance workpiece is irradiated with irradiation light with a large amount of light. FIG. 7 is a diagram showing an example of thickness information of a workpiece drawn when a low-resistance workpiece is irradiated with irradiation light having a large amount of light; FIG. 7 is a diagram showing an example of workpiece thickness information drawn when a high-resistance workpiece is irradiated with light with a small amount of light. FIG. 7 is a diagram illustrating an example of workpiece thickness information drawn when a low-resistance workpiece is irradiated with irradiation light with a small amount of light.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing the polishing apparatus of this invention is demonstrated based on Example 1 shown in drawing.

(Example 1)
Hereinafter, the overall configuration of the polishing apparatus 1 of Example 1 will be described based on FIGS. 1 and 2.

The polishing apparatus 1 of Example 1 can be used to polish silicon wafers, wafers with an oxide film formed on the surface, SOI wafers, SiC wafers, other semiconductor wafers, glass wafers, quartz glass wafers, crystal wafers, sapphire wafers, ceramic wafers, etc. This is a double-sided polishing device for polishing both the front and back surfaces of a thin plate-shaped workpiece W. As shown in FIG. 1, the polishing apparatus 1 includes a polishing machine main body 10, a shape measuring device 20, a memory 30, a display 40, and a polishing control section 50.

As shown in FIG. 1, the polishing machine main body 10 includes a lower surface plate 11, an upper surface plate 12, a sun gear 13 located at the center of the lower surface plate 11, and a lower surface plate 11 arranged concentrically about an axis L1. It has an internal gear 14 arranged so as to surround the outer periphery of the board 11. The lower surface plate 11, the sun gear 13, and the internal gear 14 are connected to a drive source (not shown) via drive shafts 17a, 17b, and 17c, respectively, and are rotationally driven.

The upper surface plate 12 is fixed to a rod 16 via a support stud 16a and a mounting member 16b attached to the upper surface, and moves up and down as the rod 16 expands and contracts. At the center of the polishing machine body 10, a drive shaft 17d is arranged that stands up along the axis L1 and has a driver 18 at its upper end. A groove (not shown) is formed on the outer peripheral surface of the driver 18, with which a hook 12b provided on the upper surface plate 12 engages. The upper surface plate 12 rotates integrally with the driver 18 as the drive shaft 17d is rotationally driven by a drive source (not shown).

The carrier plate 15 is arranged between the lower surface plate 11 and the upper surface plate 12, and meshes with the sun gear 13 and the internal gear 14, as shown in FIG. The carrier plate 15 rotates (revolutions) around the axis L1 while rotating due to the rotation of the sun gear 13 and the internal gear 14.

The work W is placed in the work holding hole 15a of the carrier plate 15. Then, the carrier plate 15 rotates and revolves while being sandwiched between the polishing pad 11a attached to the rotating lower surface plate 11 and the polishing pad 12a attached to the rotating upper surface plate 12, and the work W is held between the polishing pad 11a and the polishing pad 12a attached to the rotating upper surface plate 12. Polishing is performed using the polishing pad 12a.

Furthermore, a measurement hole 19 is formed in the upper surface plate 12 . This measurement hole 19 is fitted with a window member 19a that passes through the upper surface plate 12 and the polishing pad 12a and transmits the measurement light X emitted from the shape measuring device 20 (see FIG. 3).

The shape measuring device 20 is a laser measuring device that measures the shape of the workpiece W using a spectral interference method, which will be described later. In this shape measuring instrument 20, a probe 22 is attached to the upper surface plate 12, and rotates together with the upper surface plate 12.

The memory 30 is a storage device in which data can be read and written by the shape measuring device 20 and the polishing control section 50. The memory 30 includes, for example, an HDD, an EEPROM, an FeRAM, a flash memory, and the like. This memory 30 stores information on the shape of the workpiece W measured by the shape measuring device 20, and the like.

Based on a display command from the polishing control unit 50, the display 40 displays information on the shape of the workpiece W currently being polished, the fact that polishing of the workpiece W has been determined to be stopped, and the like. The display 40 includes, for example, a CRT (Cathode Ray Tube) display, a liquid crystal display, an organic EL (electro-luminescence) display, etc., and is attached to the polishing machine main body 10, for example. This display 40 has a screen (not shown) that can be viewed by the operator of the polishing machine main body 10.

The polishing control section 50 includes a control calculation section 51 including a CPU (Central Processing Unit), a sub-memory 52, an input device 53, and the like. The polishing control unit 50 performs control calculations based on the program stored in the sub-memory 52 and the processing target of the workpiece W, polishing conditions, polishing environment information, etc. input by the operator of the polishing machine body 10 via the input device 53. A control command is output from the section 51. Thereby, various operations of the polishing machine main body 10 are controlled. In addition, the control calculation unit 51 predicts the transition of the workpiece shape based on the information on the shape of the workpiece W being polished measured by the shape measuring device 20, and changes the timing of polishing conditions of the workpiece W according to the prediction result. and the polishing end timing.

Hereinafter, the detailed configuration of the shape measuring device 20 of the first embodiment will be explained based on FIGS. 3 to 5.

As shown in FIG. 3, the shape measuring device 20 includes a laser light source 21, a probe 22, a measuring section 23, a light amount control section 24, and a resistivity recognition section 25, and measures the workpiece W using a spectral interference method. Measure the surface shape of In the spectral interference method, first, measurement light X (see FIG. 3) emitted from the laser light source 21 is irradiated onto the workpiece W through the probe 22 and the window member 19a of the measurement hole 19 of the upper surface plate 12. Then, a first reflected light Y (see FIG. 3) obtained by reflecting this measurement light X on the front surface Wα of the workpiece W, and a second reflected light Y obtained by reflecting this measurement light X on the back surface Wβ of the workpiece W. Z (see FIG. 3) is received by the probe 22. The probe 22 converts the received light into an electrical signal and inputs it to the measuring section 23 . Subsequently, the measurement unit 23 detects an interference signal generated by an interference phenomenon between the first reflected light Y and the second reflected light Z, and calculates the thickness of the workpiece W from the frequency of the detected interference signal. Furthermore, the measuring section 23 calculates the cross-sectional shape of the workpiece W based on the thickness of the workpiece W, and uses the result as a measurement result.

Here, the laser light source 21 has a semiconductor laser which is an element that oscillates a laser by passing a current, and emits the measurement light X from this semiconductor laser. Measurement light X output from the laser light source 21 is guided to the probe 22 via the optical fiber cable 21a. Note that the light output of the laser light source 21 changes as it deteriorates over time or malfunctions due to the period of use, conditions of use, improper attachment to equipment, or the like.

The probe 22 has a collimator function that adjusts the measurement light X emitted from the laser light source 21 into parallel light and irradiates it, and is attached to the tip of the optical fiber cable 21a. Further, the probe 22 converts the received light into an interference signal using a built-in photoelectric conversion element. The interference signal converted by the probe 22 is input to the measurement unit 23 via wireless communication or the like. Here, the probe 22 has a first reflected light Y obtained by reflecting the measuring light X on the front surface Wα of the work W, and a second reflected light Z obtained by reflecting the measuring light X on the back surface Wβ of the work W. and receive light respectively.

The measuring unit 23 measures the cross-sectional shape of the workpiece W based on the frequency of the signal generated by interference between the first reflected light Y and the second reflected light Z, and displays a drawing of the shape of the workpiece W indicating the measurement result on the display 40. Display. The measurement section 23 includes a shape measurement section 23a and a drawing generation section 23b.

The shape measurement unit 23a detects an interference signal generated by the interference phenomenon based on the electrical signals of the first reflected light Y and the second reflected light Z transmitted from the probe 22. Then, in the shape measurement section 23a, the frequency of the detected interference signal is analyzed by Fourier transform or the like to obtain a frequency signal, and the thickness of the workpiece W is calculated from the frequency of this frequency signal. Note that generally, the higher the frequency, the thicker the thickness. The thickness information of the workpiece W is input to the drawing generation section 23b.

The drawing generation section 23b calculates the cross-sectional shape of the workpiece W based on the thickness information of the workpiece W input from the shape measurement section 23a. Then, the drawing generation unit 23b obtains a cross-sectional shape line T1 as shown in FIG. 4 from the calculation result of the cross-sectional shape of the workpiece W. This cross-sectional shape line T1 is a shape drawing showing the cross-sectional shape of the workpiece W, and is obtained every time the cross-sectional shape of the workpiece W is calculated. Thereby, by arranging the cross-sectional shape lines T1 obtained for the same workpiece W in chronological order, the transition of the shape change of the workpiece W can be shown. Further, the cross-sectional shape line T1 at the end of polishing of the workpiece W indicates machining result information that is the final workpiece shape of the workpiece W.

Further, the drawing generation unit 23b outputs a control command to display the cross-sectional shape line T1 on the display 40, and the cross-sectional shape line T1 is displayed on the display 40. Thereby, the operator of the polishing machine main body 10 can grasp the cross-sectional shape of the workpiece W being polished by checking the display content on the display 40. Here, the calculation accuracy of the cross-sectional shape of the workpiece W increases as the calculation accuracy of the thickness information of the workpiece W increases.

The light amount control unit 24 is a mechanism that controls the light amount of the irradiation light X′, which is the measurement light X outputted from the laser light source 21 and immediately before being irradiated onto the workpiece W, while maintaining the wavelength. The light amount control unit 24 of the first embodiment includes a variable optical attenuator 24a interposed in the middle of the optical fiber cable 21a, a voltage control unit 24b that controls the analog output voltage applied to the variable optical attenuator 24a, have. The variable optical attenuator 24a is a device that variably attenuates and adjusts the intensity (optical power) of the measurement light X transmitted through the optical fiber cable 21a. Further, the voltage control section 24b controls the analog output voltage applied to the variable optical attenuator 24a according to the resistivity of the workpiece W input from the resistivity recognition section 25. The light amount control section 24 controls the transmission amount (attenuation amount) of the measurement light X by applying the voltage controlled by the voltage control section 24b to the variable optical attenuator 24a. Here, the variable optical attenuator 24a reduces the amount of transmission of the measurement light X and increases the amount of attenuation of the measurement light X as a higher voltage is applied. Further, as the transmission amount (attenuation amount) of the measurement light X changes, the light amount of the irradiation light X' changes. Therefore, adjusting the attenuation amount (transmission amount) of the measurement light X is synonymous with controlling the light amount of the irradiation light X'. Note that the smaller the amount of transmitted measurement light X, the greater the amount of attenuation, and the smaller the amount of irradiation light X'.

The voltage control unit 24b increases the voltage applied to the variable optical attenuator 24a as the resistivity of the work W increases. That is, when the resistivity of the workpiece W is high, the light amount control unit 24 reduces the amount of light transmitted and reduces the amount of irradiation light X'. On the other hand, the voltage control unit 24b lowers the voltage applied to the variable optical attenuator 24a as the resistivity of the workpiece W decreases. For this reason, the light amount control unit 24 increases the amount of light transmission and increases the amount of irradiation light X' when the resistivity of the workpiece W is low. In this way, the light amount control unit 24 changes the light amount of the irradiation light X' based on the resistivity of the workpiece W. The relationship between the voltage applied to the variable optical attenuator 24a, the amount of light transmission and attenuation of the measurement light X, and the amount of the irradiation light X' is as shown in FIG.

The resistivity recognition unit 25 recognizes the resistivity of the workpiece W to be subjected to shape measurement, and outputs the recognized resistivity of the workpiece W to the light amount control unit 24 . Here, the resistivity recognizing unit 25 recognizes the resistivity of the workpiece W based on the peak intensity of the interference signal intensity (reflection intensity) of the first reflected light Y and the second reflected light Z detected by the measuring unit 23. do. That is, the resistivity recognition unit 25 has a database in which the detection pattern of the peak intensity of the reflection intensity created in advance is linked to the resistivity. Then, the resistivity of the workpiece W is estimated and recognized by comparing the information on the reflection intensity inputted from the measurement unit 23 with the database. Note that if the material, impurity concentration, etc. of the workpiece W are known before polishing the workpiece W, the operator of the polishing machine main body 10 uses the input device 53 of the polishing control unit 50 to select the known workpiece. Information such as the material of W is input to the resistivity recognition section 25. The resistivity recognition unit 25 may recognize the resistivity of the workpiece W from information input via the input device 53.

Furthermore, the resistivity recognition unit 25 includes a light source performance detection unit 25a that monitors the reflection intensity detected by the measurement unit 23 to detect light output performance that changes due to aging, malfunction, etc. of the laser light source 21. The light source performance detection unit 25a detects the light output performance of the laser light source 21 by comparing, for example, the initial intensity value and the monitoring value, or the moving average value of the initial intensity value and the monitoring value. The reflected light to be monitored may be any of the first reflected light Y, the second reflected light Z, or the interference signal of the first reflected light Y and the second reflected light Z. Furthermore, when detecting the optical output performance, the detection accuracy of the optical output performance of the laser light source 21 can be improved by monitoring the degree of smoothness of the noise floor in addition to the strength of the peak intensity. Note that the "noise floor" refers to the value of the noise level other than the peak waveform among the detected values of the detected reflection intensity. Then, the resistivity recognition section 25 outputs the light output performance of the laser light source 21 detected by the light source performance detection section 25a to the light amount control section 24. The light amount controller 24 may correct the voltage applied to the variable optical attenuator 24a based on the optical output performance of the laser light source 21 detected by the light source performance detector 25a. Further, the light source performance detection unit 25a can also detect the light output performance of the laser light source 21 by monitoring a signal obtained by performing spectroscopy or the like after laser oscillation instead of the reflection intensity.

Hereinafter, each step of the workpiece shape measurement process executed in the polishing apparatus 1 of the first embodiment will be explained based on the flowchart shown in FIG. 6.

In step S1, a current is applied to the laser light source 21 to cause the semiconductor laser to oscillate a laser to emit measurement light X, and the process proceeds to step S2. At this time, the workpiece W to be polished is set in the polishing machine main body 10 in advance.

In step S2, following the emission of the measurement light X in step S1, the workpiece W is irradiated with the measurement light X via the probe 22, and the process proceeds to step S3. Here, the measurement light X emitted from the probe 22 is irradiated through the window member 19a attached to the measurement hole 19. Note that at this time, the light amount control section 24 does not apply a voltage to the variable optical attenuator 24a. Therefore, the workpiece W is irradiated with the measurement light X that is not affected by the light amount control section 24.

In step S3, following the irradiation of the measurement light X in step S2, first reflected light Y obtained by reflecting the measurement light X on the front surface Wα of the workpiece W and measurement light The second reflected light Z thus obtained is received by the probe 22, and the process proceeds to step S4. Here, the probe 22 transmits the received reflected light signal to the measuring section 23.

In step S4, following the reception of the first and second reflected lights Y and Z in step S3, the measurement unit 23 measures the intensity (reflection intensity) of the interference signal of the first reflected light Y and second reflected light Z. It is detected and the process proceeds to step S5. Here, the measurement unit 23 inputs information on the detected reflection intensity to the resistivity recognition unit 25.

In step S5, following the detection of the reflection intensity in step S4, the resistivity recognition unit 25 automatically recognizes the resistivity of the workpiece W based on the input peak intensity of the reflection intensity, and proceeds to step S6. . Here, the resistivity of the workpiece W is recognized by comparing the detection pattern of the reflection intensity with a database created in advance that links the reflection intensity and the resistivity. Further, the recognized resistivity of the workpiece W is input to the light amount control section 24.

That is, when a high-resistance work W having a high resistivity is irradiated with the measurement light X, a relatively high peak intensity is detected as shown surrounded by a dashed line A in FIG. 7A. On the other hand, when the measurement light X is irradiated onto a low-resistance workpiece W having a low resistivity, a relatively low peak intensity is detected, as shown surrounded by a dashed-dotted line B in FIG. 7B. In this way, the peak intensity of the detected reflection intensity differs depending on the resistivity (high or low) of the workpiece W. Therefore, the resistivity recognition unit 25 can recognize the resistivity of the workpiece W based on the height of the peak intensity of the reflection intensity detected by the measurement unit 23. Note that, for example, an S/N ratio (signal-to-noise ratio) or an S/B ratio (signal-to-background ratio) can be used as an index for determining the level of the peak intensity of the reflection intensity. Moreover, the height of the peak intensity may be determined by other methods.

Further, in this step S5, the light source performance detection section 25a monitors the reflection intensity detected in step S4, and detects the light output performance of the laser light source 21. Here, if the optical output performance of the laser light source 21 becomes low due to the influence of aging, etc., even if the workpiece W with the same resistivity is irradiated with the measurement light X with the same output setting value, the initial intensity The peak intensity decreases and the noise floor α becomes smoother compared to the value. For example, FIG. 7C shows the reflection intensity when a high-resistance work W is irradiated with the measurement light X from the laser light source 21 with low optical output performance. In this case, the peak intensity decreases and the noise floor α becomes smoother compared to the initial intensity value shown in FIG. 7A.

In step S6, following the recognition of the resistivity in step S5, the light amount control unit 24 controls the amount of irradiation light X' according to the resistivity of the workpiece W, and the process proceeds to step S7. That is, the light amount control section 24 applies a voltage corresponding to the resistivity of the workpiece W input from the resistivity recognition section 25 to the variable optical attenuator 24a. Thereby, the light amount control unit 24 controls the amount of transmission of the measurement light X passing through the optical fiber cable 21a, and the light amount of the irradiation light X' is controlled according to the resistivity of the workpiece W. Here, for example, when the resistivity of the workpiece W is high (high resistance), by applying a relatively high voltage to the variable optical attenuator 24a, the amount of transmission of the measurement light X is reduced, and the irradiation light X' is Reduce the amount of light. Furthermore, when the resistivity of the workpiece W is low (low resistance), by applying a relatively low voltage to the variable optical attenuator 24a, the amount of transmitted measurement light X is increased, and the amount of irradiation light X' is also reduced. Do more.

In step S7, following the light intensity control of the irradiation light X' in step S6, the shape measurement of the workpiece W is performed, and the process proceeds to the end. Thereby, when measuring the shape of the workpiece W, the workpiece W is irradiated with the irradiation light X' whose light amount is controlled according to the resistivity of the workpiece W.

Hereinafter, the workpiece shape measurement function of the polishing apparatus 1 of Example 1 will be explained.

In the polishing apparatus 1 of the first embodiment, when the cross-sectional shape of the workpiece W being polished by the polishing machine main body 10 is measured by the shape measuring device 20, steps S1, S2, S3, S4, and S4 of the flowchart shown in FIG. The process of step S5 is performed in order. That is, when the workpiece W is set in the polishing machine main body 10, first, the laser light source 21 emits the measurement light X, and the workpiece W is irradiated with the measurement light X through the probe 22 and the window member 19a. Then, the first reflected light Y and the second reflected light Z are received by the probe 22 and transmitted to the measuring section 23 . The measurement unit 23 detects the intensity (reflection intensity) of the interference signal between the first reflected light Y and the second reflected light Z, and inputs information on the detected reflection intensity to the resistivity recognition unit 25 . Then, the resistivity recognition unit 25 automatically recognizes the resistivity of the workpiece W by comparing the input reflection intensity detection pattern with a database created in advance that links the reflection intensity and resistivity. .

Subsequently, the process of step S6 in the flowchart of FIG. 6 is performed, and the light amount of the irradiation light X' is controlled according to the resistivity of the workpiece W. That is, the light amount control section 24 applies a voltage corresponding to the resistivity of the workpiece W recognized by the resistivity recognition section 25 to the variable optical attenuator 24a. The variable optical attenuator 24a controls the amount of transmitted measurement light X according to the applied voltage, and as a result, the light amount control section 24 can control the amount of irradiation light X'. At this time, the light amount controller 24 may correct the voltage applied to the variable optical attenuator 24a based on the optical output performance of the laser light source 21 detected by the light source performance detector 25a. Then, the process advances to step S7, and the shape measurement of the workpiece W is performed.

Here, the accuracy of shape measurement of the workpiece W is determined depending on the amount of measurement light (irradiation light X') irradiated onto the workpiece W and the resistivity of the workpiece W. That is, when the workpiece W having a high resistance is irradiated with the irradiation light X' having a large amount of light, as shown in FIG. 8A, the variation ΔW in the thickness information of the workpiece W becomes large, and it is difficult to obtain a highly accurate cross-sectional shape line T1. is difficult. However, when the workpiece W with a low resistance is irradiated with the irradiation light X' with a large amount of light, the variation ΔW in the thickness information of the workpiece W can be suppressed as shown in FIG. 8B, and the highly accurate cross-sectional shape line T1 can be You can ask for it.

On the other hand, when irradiating a workpiece W with a high resistance with a small amount of irradiation light X', the variation ΔW in the thickness information of the workpiece W can be suppressed, as shown in FIG. The drawing accuracy of the shape line T1 can be improved. However, when a low-resistance workpiece W is irradiated with the irradiation light X' with a small amount of light, as shown in FIG. 8D, the variation ΔW in the thickness information of the workpiece W increases, making it difficult to obtain a highly accurate cross-sectional shape line T1. becomes difficult. Note that if the variation ΔW in the thickness information of the workpiece W is large, not only will it be impossible to obtain the cross-sectional shape line T1 with good accuracy, but also the cross-sectional shape line T1 may not be drawn or the cross-sectional shape line T1 may be incorrect. Sometimes it happens.

On the other hand, in the polishing apparatus 1 of the first embodiment, the light amount control unit 24 provided in the middle of the optical fiber cable 21a through which the measurement light X is transmitted according to the resistivity of the workpiece W, as described above, A voltage corresponding to the resistivity of is applied to the variable optical attenuator 24a. Accordingly, the amount of transmission of the measurement light X is controlled, and the amount of the irradiation light X' is controlled. As a result, the workpiece W can be irradiated with the irradiation light X' with an amount of light corresponding to the resistivity of the workpiece W. For example, a high-resistance workpiece W can be irradiated with the irradiation light X' with a reduced amount of light. The shape of the workpiece can be measured, or the shape of the workpiece can be measured by irradiating the low-resistance workpiece W with the irradiation light X' having a large amount of light.

That is, the light amount of the irradiation light X' is appropriately adjusted for each material, impurity concentration, etc. (resistivity) of the workpiece W so that the signal received by the probe 22 is in an optimal signal state. Thereby, the accuracy of the measurement results can be improved and the shape of the workpiece can be measured appropriately. By appropriately measuring the workpiece shape, it is possible to improve the polishing accuracy of the workpiece W, improve the yield of polishing the workpiece W, and improve the processing recipe necessary for modifying the shape of the workpiece W. You can choose accurately. Furthermore, by accurately measuring the shape of the workpiece W during the polishing process, it becomes possible to omit measurement of the workpiece shape after the polishing process, and it becomes possible to improve productivity.

Note that the shape measuring device 20 of the polishing apparatus 1 of the first embodiment adjusts the light amount of the irradiation light X' according to the resistivity of the workpiece W while maintaining the wavelength of the single laser light source 21. Therefore, it is completely different from, for example, a method that includes a plurality of light sources and switches these light sources according to the type of film formed on the surface of the workpiece W.

In the first embodiment, as shown in FIG. 5, when the resistivity of the workpiece W is high, a relatively high voltage is applied to the variable optical attenuator 24a, and when the resistivity of the workpiece W is low, a relatively high voltage is applied to the variable optical attenuator 24a. A relatively low voltage is applied to the variable optical attenuator 24a. Therefore, in the light amount control unit 24, when the resistivity of the workpiece W is high, the light amount of the irradiation light X' is made smaller than when the resistivity of the workpiece W is low.

Thereby, the light intensity of the irradiation light X' can be controlled to a light intensity that allows the shape of the workpiece to be appropriately measured according to the resistivity of the workpiece W. Therefore, the shape of the workpiece can be accurately measured, and it is possible to prevent the occurrence of a measurement error or a workpiece W whose shape cannot be measured.

Further, in the first embodiment, the resistivity recognition unit 25 recognizes the resistivity of the workpiece W based on the intensity (reflection intensity) of the interference signal of the first reflected light Y and the second reflected light Z, and The resistivity of W is output to the light amount control section 24. Then, the light amount control section 24 changes the magnitude of the voltage applied to the variable optical attenuator 24a according to the resistivity of the workpiece W output from the resistivity recognition section 25.

Thereby, the resistivity of the workpiece W can be automatically measured, and the amount of irradiation light X' can be smoothly controlled in accordance with the resistivity of the workpiece W. Therefore, errors in measuring the shape of the workpiece are less likely to occur, and the shape of the workpiece can be measured more appropriately.

Further, in the first embodiment, the light output performance of the laser light source 21 is detected by the light source performance detection unit 25a based on the reflection intensity. In this case, when controlling the light intensity of the irradiation light X' according to the resistivity of the workpiece W in the light intensity control section 24, it is possible to correct it according to the light output performance of the laser light source 21, thereby improving the measurement accuracy of the workpiece shape. Further improvements can be made.

Furthermore, in the polishing apparatus 1 of Example 1, the first reflected light Y obtained by reflecting the measuring light X on the front surface Wα of the workpiece W, and the first reflected light Y obtained by reflecting the measuring light X on the back surface Wβ of the workpiece W. 2. The measuring section 23 determines the thickness of the workpiece W from the frequency of the interference signal generated by the interference phenomenon with the reflected light Z, and measures the shape of the workpiece W based on the determined thickness of the workpiece W. That is, the shape measuring device 20 measures the surface shape of the workpiece W using a so-called spectral interference method.

As a result, unlike the case where, for example, a lamp is used as a light source that emits the measurement light and the shape of the workpiece is measured by analyzing the spectrum of the reflected light when the measurement light from the lamp is reflected by the workpiece, the measurement light It is possible to increase coherence and improve signal detection accuracy.

Although the polishing apparatus of the present invention has been described above based on Example 1, the specific configuration is not limited to this example. Changes and additions to the design are permitted as long as they do not deviate.

In the shape measuring device 20 of the first embodiment, an example is shown in which the light amount control section 24 includes the variable optical attenuator 24a and the voltage control section 24b. However, the light amount control section 24 is not limited to this, and may be capable of controlling the light amount of the irradiation light X', which is the measurement light X immediately before being irradiated onto the workpiece W. Therefore, for example, the light amount control unit 24 may be configured by an ND (Neutral Density) filter or a polarization adjuster interposed in the middle of the optical fiber cable 21a, each having a control unit, or by a polarization adjuster. The light amount control unit 24 may be configured by a switch or the like that can change the output. Here, the ND filter is a filter that reduces only the amount of light by uniformly absorbing the light that passes through it. Further, the polarization adjuster is a device that adjusts the polarization state of the measurement light X transmitted within the optical fiber cable 21a, for example by applying stress to the optical fiber cable 21a from the outside. Alternatively, the light amount control section 24 may be formed by combining a plurality of mechanisms such as a variable optical attenuator and an ND filter.

In the first embodiment, an example was shown in which the probe 22 of the shape measuring device 20 was attached to the upper surface plate 12, but the present invention is not limited to this. For example, the measurement light X may be emitted from an optical head installed above the upper surface plate 12. In this case, a plurality of measurement holes are formed along the circumferential direction of the upper surface plate 12, and the measurement light X is irradiated each time the measurement hole comes directly below the optical head as the upper surface plate 12 rotates. Note that the lower surface plate 11 may be provided with a measurement hole, and the measurement light X may be irradiated onto the lower surface of the workpiece W from below the lower surface plate 11 to measure the shape of the workpiece.

In the first embodiment, the resistance of the workpiece W is determined by the resistivity recognition unit 25 based on the peak intensity of the reflection intensity detected by the measurement unit 23 and information such as the material of the workpiece W inputted via the input device 53. An example of automatically recognizing the rate was shown. However, the present invention is not limited to this, and if the resistivity of the workpiece W is known in advance before polishing the workpiece W, the resistivity of the workpiece W that has already been determined via the input device 53 of the polishing control unit 50, etc. may be input directly to the light amount control section 24. Further, even in this case, the light source performance detection unit 25a detects a change in the light output performance of the laser light source 21 based on a change in the peak intensity of the reflection intensity. Then, the voltage applied to the variable optical attenuator 24a may be corrected based on the optical output performance of the laser light source 21.

That is, the resistivity recognition section 25 and the light source performance detection section 25a may be provided independently. The polishing apparatus may include only one of the resistivity recognition section 25 and the light source performance detection section 25a, or it may not have both the resistivity recognition section 25 and the light source performance detection section 25a, and the polishing apparatus may have an input by an operator. The amount of irradiation light may be controlled based on the determined workpiece resistance value.

Further, in the first embodiment, the laser light source 21 is an example of an element capable of outputting infrared laser light, but the present invention is not limited to this. For example, as the laser light source 21, one that outputs white light may be used.

In addition, in Example 1, as a method of measuring the shape of the workpiece W, the reflected light is converted into an interference signal, and the frequency signal obtained from the intensity of the interference signal is analyzed by frequency analysis such as Fourier transform. Although an example has been shown in which the shape of the workpiece W being polished is measured from the frequency analysis results, the present invention is not limited thereto. For example, the shape of the workpiece W may be measured using optical constant analysis, color analysis, fitting analysis, etc., or a combination of these methods.

Moreover, although the polishing apparatus 1 of the first embodiment has the lower surface plate 11 and the upper surface plate 12 and is a double-sided polishing apparatus capable of simultaneously polishing both surfaces of the workpiece W, the present invention is not limited thereto. For example, the present invention can be applied to a single-sided polishing apparatus that polishes only one side of the workpiece W.

Furthermore, the work W to be polished by the polishing apparatus 1 of Example 1 is not limited to a silicon wafer or a wafer with an oxide film formed on the surface, but may be made of a material that transmits the laser light that serves as the measurement light. It is fine as long as it is. That is, the work may be made of a resin such as vinyl chloride or PET, as long as it can transmit laser light.

In the polishing apparatus 1 of the first embodiment, an example is shown in which the shape measuring device 20 includes a laser light source 21, a probe 22, a measuring section 23, a light amount control section 24, and a resistivity recognition section 25. . Here, the probe 22 is attached to the upper surface plate 12, but the laser light source 21, measurement section 23, light amount control section 24, and resistivity recognition section 25 may be mounted on the polishing machine main body 10. , it may be installed separately from the polishing machine main body 10. Further, the polishing control section 50, the shape measuring device 20, or the resistivity recognition section 25 may be managed remotely via a computer network. In this case, the polishing control section 50, shape measuring device 20, or resistivity recognition section 25 corresponding to each of the plurality of polishing machine bodies 10 can be centrally managed, contributing to stable operation of the production line. can do.

1 Polishing device 10 Polishing machine main body 11 Lower surface plate 12 Upper surface plate 19 Measuring hole 20 Shape measuring device 21 Laser light source 22 Probe 23 Measuring section 23a Shape measuring section 23b Drawing generation section 24 Light amount control section 24a Variable optical attenuator 24b Voltage control section 25 Resistivity recognition unit 25a Light source performance detection unit

Claims (4)

A polishing device that rotates a workpiece and a surface plate relative to each other and polishes the workpiece with a polishing pad attached to the surface plate,
A polishing machine body for polishing the workpiece, and a shape measuring device for measuring the shape of the workpiece based on reflected light obtained by irradiating the workpiece with measurement light and reflecting the measurement light from the front and back surfaces of the workpiece. and,
The shape measuring device includes a laser light source that emits the measurement light;
a measurement unit that detects an interference signal between a first reflected light obtained by reflecting on the front surface of the workpiece and a second reflected light obtained by reflecting on the back surface of the workpiece;
It has a database that links the reflection intensity, which is the intensity of the interference signal, and the resistivity of the workpiece, and by comparing the reflection intensity information input from the measurement unit with the database, the resistance of the workpiece can be determined. a resistivity recognition unit that recognizes the resistivity;
a light amount control section that controls the amount of irradiation light that is measurement light immediately before irradiating the workpiece based on the resistivity recognized by the resistivity recognition section ;
A polishing device characterized by having: The polishing device according to claim 1,
The polishing apparatus is characterized in that the light amount control unit reduces the amount of the irradiation light when the resistivity of the workpiece is high than when the resistivity of the workpiece is low. In the polishing apparatus according to claim 1 or 2,
The shape measuring device includes a light source performance detection section that detects light output performance of the laser light source based on the reflection intensity.
A polishing device characterized by: The polishing apparatus according to any one of claims 1 to 3,
The light amount control unit includes a variable optical attenuator that adjusts the intensity of light for each wavelength, an ND filter that evenly absorbs the passing light, and a polarization adjuster that adjusts the polarization state of the light. have at least one
A polishing device characterized by: