JP2009063334A - Inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device capable of detecting a fine defect of a measuring object. <P>SOLUTION: The device includes a capacitive sensor 15 for measuring a capacitance of the measuring object (a resist film 12 provided on a semiconductor wafer 10), and a length measuring sensor 20 (a measuring light source 21, a light receiving part 22) for measuring a distance between the bottom surface of the measuring object and the capacitive sensor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection apparatus that measures and inspects the capacitance of an object to be measured.

As an apparatus for measuring the capacitance and inspecting the object to be measured, for example, the counter electrode held by an insulator is brought into contact with the film of the object to be measured, and the film thickness of the film is determined from the capacitance at the time of contact. An apparatus for measuring and inspecting is known (Patent Document 1).
Japanese Utility Model Publication No. 58-86507

  The measuring device measures and inspects the capacitance of the object to be measured (film) itself, and measures and inspects the distance between the counter electrode and the object to be measured by the change in capacitance. .

  When the inspection is performed by measuring the distance between the counter electrode and the object to be measured by capacitance, it is assumed that the distance between the bottom surface of the object to be measured and the counter electrode does not change. Only the distance between the surface of the object to be measured and the counter electrode changes, and by capturing this as a change in capacitance, the thickness uniformity of the object to be measured and the change in height of the surface are inspected. Can do. If the measured object itself has warping or undulation, and the distance between the bottom surface of the measured object and the counter electrode changes, the measured capacitance value may be due to warpage of the measured object or the measured object. I don't know if this is due to a change in thickness. For example, when inspecting the uniformity of the thickness of a resist film applied on a semiconductor wafer, if the semiconductor wafer itself is warped or swelled, the measured change in capacitance causes the warpage of the semiconductor wafer. It is not known whether it is due to a change in the film thickness of the resist film. Normally, the change in film thickness is very small compared to the warpage and undulation of the semiconductor wafer itself, and the change in capacitance due to the change in film thickness is also compared to the change in capacitance due to the warpage and undulation of the semiconductor wafer itself. It is very small and buried in the capacitance change due to warpage and waviness of the semiconductor wafer itself.

  That is, in the apparatus that measures and inspects the distance between the counter electrode and the object to be measured by the capacitance, there is a problem that it is difficult to detect a minute defect of the object to be measured.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an inspection apparatus capable of detecting a minute defect of an object to be measured and a semiconductor inspection apparatus including the inspection apparatus.

  The inspection apparatus according to claim 1 of the present invention that achieves the above object includes a capacitance sensor that measures the capacitance of a measurement object, and a gap between the bottom surface of the measurement object and the capacitance sensor. And a length measuring sensor for measuring the distance.

  The inspection apparatus according to claim 2 of the present invention is based on the measurement result of the length measurement sensor so that the distance between the capacitance sensor and the bottom surface of the inspection object is constant. A moving mechanism for moving the capacitance sensor and / or the object to be measured is provided.

  According to a third aspect of the present invention, there is provided an inspection apparatus including a scanning mechanism that scans the capacitance sensor on the object to be measured.

  The inspection apparatus according to claim 4 of the present invention is characterized in that the moving mechanism includes a piezoelectric element that moves the capacitance sensor based on a measurement result from the length measurement sensor.

  A semiconductor inspection apparatus of the present invention is an apparatus for inspecting the surface of a semiconductor wafer, and is characterized by comprising the inspection apparatus according to any one of claims 1 to 4.

  According to the present invention, a minute defect of an object to be measured can be detected.

  An embodiment of an inspection apparatus according to the present invention will be described below with reference to FIGS.

  The inspection apparatus of the present invention is an apparatus for inspecting an object to be measured by capacitance, and FIG. 1 is a schematic side view showing an embodiment in which the inspection apparatus of the present invention is applied to a semiconductor inspection apparatus.

  As shown in FIG. 1, the inspection apparatus according to the present embodiment includes a capacitance sensor 15 that measures the capacitance of a measurement target portion on a semiconductor wafer 10 that is a measurement object, the semiconductor wafer 10, and the capacitance sensor 15. The distance between the capacitance sensor 15 and the semiconductor wafer 10 is made constant based on the measurement result of the length measurement sensor 20 and the sensor head 25 equipped with the length measurement sensor 20 that measures the distance between Are provided with a moving mechanism 30 for moving the sensor head 25, a scanning mechanism 35 for scanning the sensor head 25 on the semiconductor wafer 10, and a control unit 40 for controlling the entire inspection apparatus.

  The semiconductor wafer 10 is mounted on an inspection stage 11 that can rotate during inspection and can move in the vertical direction. For example, a transparent resist film 12 as an object to be measured is applied to the surface of the semiconductor wafer 10, and this inspection apparatus inspects the uniformity of the film thickness of the resist film 12 by measuring capacitance. . The inspection stage 11 is driven by a driving device 13, and this driving device 13 is controlled by the control unit 40, and rotates the inspection stage 11 (see arrow A in FIG. 1) during inspection. Further, the inspection stage 11 can be moved in the vertical direction (see arrow B in FIG. 1) by the driving device 13.

  The capacitance sensor 15 has a counter electrode 16 (see FIG. 2) disposed so as to face the resist film 12 of the object to be measured, and a voltage is supplied from the power source 17 between the counter electrode 16 and the semiconductor wafer 10. In addition, the capacitance of the space between the counter electrode 16 and the measurement location 10a (see FIG. 4) of the semiconductor wafer 10 opposed thereto, that is, the capacitance of the resist film 12 existing in this space is measured. Is done. The measured capacitance value is sent to the control unit 40. Since this electrostatic capacitance value is proportional to the distance between the counter electrode 16 and the resist film 12 on the measurement location 10a of the semiconductor wafer 10 facing the counter electrode 16, a plurality of electrostatic capacitances measured by changing the measurement location 10a. The film thickness uniformity (film thickness variation) of the resist film 12 can be inspected from the capacitance value.

  The length measuring sensor 20 measures a distance L (see FIG. 2) between the length measuring sensor 20 (sensor head 25) and the semiconductor wafer 10, and is directed toward the semiconductor wafer 10, for example, as shown in FIG. A measurement light source 21 that irradiates measurement light, and a light receiving unit 22 that receives reflected light reflected by the surface of the semiconductor wafer 10 that is the interface between the resist film 12 and the semiconductor wafer 10 and also the bottom surface of the resist film 12 due to the irradiation. Prepare. The light receiving position of the reflected light at the light receiving unit 22 varies depending on the distance L as shown by the solid line 22a, the two-dot chain line 22b, and the two-dot chain line 22c in FIG. 3, and the distance L is measured by obtaining this light receiving position. I can do it. An alternate long and two short dashes line 22b indicates a case where the distance L is longer than that indicated by the solid line 22a, and an alternate long and two short dashes line 22c indicates a case where the distance L is shorter than that indicated by the solid line 22a. The output of the light receiving unit 22 is sent to the control unit 40. Even if the measurement light is irradiated to the position of the resist film 12 on the semiconductor wafer 10, if the reflected light reflected by the bottom surface of the resist film 12 is received, the bottom surface of the resist film 12 can be regarded as the surface of the semiconductor wafer 10. The distance L (see FIG. 2) between the length measuring sensor 20 (sensor head 25) and the semiconductor wafer 10 can be measured.

  Since the length measurement sensor 20 is mounted on the sensor head 25 together with the capacitance sensor 15, the distance L between the length measurement sensor 20 and the semiconductor wafer 10, which is a measurement value of the length measurement sensor 20, is a capacitance sensor. It also represents the distance between 15 and the semiconductor wafer 10.

  The moving mechanism 30 is configured by laminating a plurality of piezoelectric elements, for example, piezoelectric elements, and inputs a drive signal from the control unit 40 based on the output of the light receiving unit 22 to move the sensor head 25 in the vertical direction (FIG. 1, FIG. The distance L between the length measuring sensor 20 (capacitance sensor 15) and the semiconductor wafer 10 is kept constant. The piezo element constituting the moving mechanism 30 has a large response frequency of, for example, 3 KHz, and immediately follows even if the distance between the capacitance sensor 15 and the semiconductor wafer 10 changes due to warpage or undulation of the semiconductor wafer 10. The distance L between the capacitance sensor 15 and the semiconductor wafer 10 can be kept constant by moving the sensor head 25 in the vertical direction. The displacement amount of the piezo element itself (the distance by which the sensor head 25 is moved in the vertical direction) is small, but this displacement amount can be increased by stacking a plurality of piezo elements, and the moving mechanism 30 uses this. is doing. Instead of laminating a plurality of piezo elements, the moving mechanism 30 may be configured by combining a piezo element and an enlarging mechanism that enlarges the displacement of the piezo element.

  The scanning mechanism 35 scans the sensor head 25 (capacitance sensor 15) on the semiconductor wafer 10. For example, the scanning mechanism 35 supports the sensor head 25, and the sensor head 25 is a semiconductor through the support 36. A guide rail 37 that guides in the radial direction of the wafer 10 and a drive unit 38 that inputs a drive signal from the control unit 40 and moves the support unit 36 along the guide rail 37 are provided. As shown in FIG. 4, the sensor head 25 (capacitance sensor 15) is rotated by rotating the inspection stage 11 while moving the sensor head 25 (capacitance sensor 15) in the radial direction of the semiconductor wafer 10 by the scanning mechanism 35. 15) can be scanned over substantially the entire surface of the semiconductor wafer 10. Specifically, the sensor head 25 is formed on the entire surface of the resist film 12 on the semiconductor wafer 10 and on the outer peripheral portion (ERB (Edge Bead Removal) and the edge portion of the semiconductor wafer 10) where the resist film 12 is not provided. The (capacitance sensor 15) can be scanned.

  As described above, the control unit 40 inputs the capacitance value measured by the capacitance sensor 15 and also inputs the output of the light receiving unit 22 of the length measurement sensor 20 (measured value of the distance L). A drive signal is output to the moving mechanism 30 so as to be constant, and a drive signal is output to the drive unit 38 of the scanning mechanism 35 and the drive device 13 of the inspection stage 11. The control unit 40 also obtains the uniformity of the film thickness of the resist film 12 based on the capacitance value measured by the capacitance 15 and points out a defective film thickness portion when the film thickness exceeds a preset threshold value. The message is output and displayed on a display device (not shown).

  FIG. 5 is a flowchart showing an example of control contents of the control unit 40.

  A semiconductor wafer 10 to be inspected is placed on an inspection stage 11. When the measurement location 10a (see FIG. 4) of the semiconductor wafer 10 is input to the control unit 40 in step S1, the control unit 40 outputs drive signals to the drive unit 38 of the scanning mechanism 35 and the drive unit 13 of the inspection stage 11, respectively. While the semiconductor wafer 10 is rotated by the inspection stage 11, the sensor head 25 is moved onto the measurement location 10a of the semiconductor wafer 10 by the scanning mechanism 35 to position the sensor head 25 on the measurement location 10a.

  In step S2, the capacitance of the resist film 12 on the measurement location 10a is measured by the capacitance sensor 15. When the capacitance is measured by the capacitance sensor 15, the distance L between the length measurement sensor 20 and the semiconductor wafer 10 is measured by the length measurement sensor 20, and the distance L due to warpage of the semiconductor wafer 10 or the like. When is changed, the sensor head 25 is immediately moved by the moving mechanism 30 to keep the distance L constant. Therefore, the capacitance sensor 15 is kept at a constant distance from the semiconductor wafer 10, and the measured capacitance value is a value corresponding to the thickness of the resist film 12 on the measurement location 10a. This capacitance value is input from the capacitance sensor 15 to the control unit 40, and compared with a threshold value set in advance in step S3. If the capacitance value is outside the threshold value, the process proceeds to step S4. Move on to step 5.

  In step S4, the defective part of the resist film 12 is displayed on a display device (not shown). As the display contents, for example, the location on the semiconductor wafer 10 and whether the film thickness is thicker or thinner than a threshold value are displayed. For the semiconductor wafer 10 in which a defective portion is present, it is removed from the inspection stage 11 and sent to the step of removing the resist film 12. Alternatively, when the inspection is continued for other locations, the process proceeds to step S5.

  In step S5, it is determined whether or not to continue the measurement. If so, the process returns to step S1, the sensor head 25 is positioned at another measurement location 10a, and the film thickness of the resist film 12 is measured again. If not continue, the measurement ends.

  According to the inspection apparatus of the present embodiment, when measuring the capacitance by the capacitance sensor 15, the distance between the length measurement sensor 20 and the semiconductor wafer 10 is measured by the length measurement sensor 20. Even if there is warping or undulation, the distance L between the length measuring sensor 20 and the semiconductor wafer 10 is kept constant by the moving mechanism 30. For this reason, the distance between the capacitance sensor 15 disposed on the sensor head 25 together with the length measuring sensor 20 and the semiconductor wafer 10 is also maintained constant. As a result, the capacitance that is the output of the capacitance sensor 15 is maintained. The value changes only according to the film thickness variation of the resist film 12 and is not affected by the warp of the semiconductor wafer 10 or the like. Therefore, it is possible to accurately inspect the uniformity of the film thickness of the resist film 12.

  Further, as described above, since the length measuring sensor 20 and the capacitance sensor 15 are fixedly arranged together on the sensor head 25, the sensor head 25 is moved by the moving mechanism 30 based on the measurement result of the length measuring sensor 20. If the distance L between the length measuring sensor 20 and the semiconductor wafer 10 is kept constant by moving, the distance between the capacitance sensor 15 and the semiconductor wafer 10 is also kept constant at the same time.

  Further, since the moving mechanism 30 is constituted by a piezo element, the responsiveness is excellent, and the sensor head 25 (capacitance sensor 15) is immediately moved based on the measurement result of the distance L of the length measuring sensor 20. I can do it.

  The inspection apparatus of the present invention is not limited to the one shown in the above embodiment. For example, although the case where only the moving mechanism 30 is driven and the sensor head 25 is moved to maintain the distance L between the length measuring sensor 20 and the semiconductor wafer 10 constant is shown, the present invention is not limited to this. The inspection stage 11 on which the wafer 10 is mounted is moved in the vertical direction by the driving device 13, or the sensor head 25 is moved by the moving mechanism 30 and the inspection stage 11 is moved in the vertical direction by the driving device 13. The distance L between the length measuring sensor 20 and the semiconductor wafer 10 may be kept constant.

  Further, the distance L between the length measurement sensor 20 (capacitance sensor 15) and the semiconductor wafer 10 is kept constant by the movement mechanism 30 based on the measurement result of the length measurement sensor 20, but the movement mechanism is not necessarily limited. It is not necessary to maintain the distance L constant by 30. For example, the capacitance value of the capacitance sensor 15 may be corrected by the measurement result of the length measurement sensor 20. In this case, the moving mechanism 30 is not necessary, and the apparatus can be simplified.

  Further, as the length measuring sensor 20, a case where a type measuring the distance L between the length measuring sensor 20 and the semiconductor wafer 10 based on the light receiving position of the reflected light at the light receiving unit 22 is shown. However, the present invention is not limited to this. For example, a position measurement mark may be provided at an appropriate location on the semiconductor wafer 10 and the distance L may be measured from the mark image formation position (focal position) of a photographing apparatus that photographs the mark. Good.

  Moreover, although the case where the capacitance sensor 15 and the length measurement sensor 20 are configured separately and attached to the sensor head 25 is shown, the capacitance sensor 15 and the length measurement sensor 20 may be configured integrally.

  Moreover, although the case where the sensor head 25 is configured to move in the radial direction (uniaxial direction) of the semiconductor wafer 10 as the scanning mechanism 35 has been shown, the present invention is not limited to this, for example, the sensor head 25 intersects with the uniaxial direction. The sensor head 25 may be scanned so as to meander on the semiconductor wafer 10 so as to move in a direction perpendicular to the other axis.

  Moreover, in the said embodiment, although the case where the inspection apparatus of this invention was applied to the semiconductor inspection apparatus which test | inspects the uniformity of the film thickness of the resist film 12 provided on the semiconductor wafer 10 was shown, it is not limited to this, For example, a semiconductor inspection that inspects an EBR (Edge Bead Removal) portion, an apex (???), or a bevel portion of the semiconductor wafer 10 that is a portion rinsed at the outer peripheral portion of the resist film 12 on the semiconductor wafer 10. It can also be applied to a device. The present invention can also be applied to an inspection apparatus for circuit patterns formed on the semiconductor wafer 10.

It is a schematic side view which shows one Embodiment which applied the inspection apparatus of this invention to the semiconductor inspection apparatus. It is the schematic side view to which the part of the sensor head with which the semiconductor inspection apparatus of FIG. 1 was equipped was expanded. FIG. 3 is an enlarged explanatory view of a length measurement sensor portion in the sensor head of FIG. 2. It is explanatory drawing of the state which scans the sensor head of FIG. 2 on a semiconductor wafer. It is a flowchart which shows an example of the control content of the control part with which the semiconductor inspection apparatus of FIG. 1 was equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor wafer 11 Inspection stage 12 Resist film 13 Drive apparatus 15 Capacitance sensor 16 Counter electrode 20 Length measuring sensor 21 Measurement light source 22 Light-receiving part 25 Sensor head 30 Moving mechanism 35 Scan mechanism 36 Support part 37 Guide rail 38 Drive part 40 Control Part

Claims (5)

A capacitance sensor for measuring the capacitance of the object to be measured;
A length measuring sensor for measuring a distance between a bottom surface of the object to be measured and the capacitance sensor;
An inspection apparatus comprising: The inspection apparatus according to claim 1,
The capacitance sensor and / or the object to be measured are moved based on the measurement result of the length measuring sensor so that the distance between the capacitance sensor and the bottom surface of the object to be measured is constant. An inspection apparatus comprising a moving mechanism. The inspection apparatus according to claim 1 or 2,
An inspection apparatus comprising: a scanning mechanism that scans the capacitance sensor on the object to be measured. The inspection apparatus according to claim 2,
2. The inspection apparatus according to claim 1, wherein the moving mechanism includes a piezoelectric element that moves the capacitance sensor based on a measurement result from the length measurement sensor. An apparatus for inspecting the surface of a semiconductor wafer,
A semiconductor inspection apparatus comprising the inspection apparatus according to claim 1.

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