JP2016184711A - Inspection apparatus of semiconductor wafer and automatic inspection method of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection apparatus capable of detecting only a defect on the wafer surface, without being influence by the surface state of an inspection stage, even for a wafer transmitting light.SOLUTION: An inspection apparatus of semiconductor wafer includes an inspection stage, and a wafer mounting jig to be mounted on the inspection stage. The wafer mounting jig has a hollow cylinder as the body, and has a counterbore provided along the inner periphery, on the upper surface side, i.e., the side opposite to the side in contact with the inspection stage, in the sidewall of the cylinder. The counterbore is formed while having a diameter larger than that of a semiconductor wafer becoming an inspection object. When mounting the semiconductor wafer on the bottom face of the counterbore so as to come into contact with the reverse face of the semiconductor wafer, the semiconductor wafer is held while keeping a constant distance between the inspection stage. The constant distance is determined based on the amount of the semiconductor wafer inspection light, reflected on the inspection stage surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor wafer inspection technique.

  In wafer processes for manufacturing semiconductor devices, defect inspection of wafers is performed at any time in the main processes and important processes in the wafer process to identify foreign matters and defects in order to improve wafer quality control and yield. , Actions such as transition management, problem process detection and quick feedback are essential.

  In addition, in a low-quality wafer having a large number of substrate defects, such as a downfall, a triangular defect, and a carrot, which cause a malfunction of the semiconductor device, such as a wide band gap semiconductor wafer such as a silicon carbide (SiC) wafer or a gallium nitride (GaN) wafer. Inspects defects of the wafer itself, and correlates with electrical characteristics through the wafer process to identify defects that cause problems in electrical characteristics. Then, by feeding back the result to the wafer manufacturing process, a substrate manufacturing process in which such a defect does not occur is constructed to improve the wafer quality and the yield.

  Here, in an inspection apparatus for inspecting a defect of a wafer, conventionally, as disclosed in, for example, FIG. 1 of Patent Document 1, automatic conveyance or manual (hand-mounted) conveyance is performed immediately above a flat inspection stage of the inspection apparatus. A wafer is mounted, and inspection is performed by fixing the wafer to an inspection stage by vacuum suction or the like from the back side of the wafer.

  In a general lamp-emitting wafer inspection system, light (visible light) emitted from a light source such as a xenon lamp is incident on a wafer mounted on an inspection stage, the reflected light is detected, and an image is recognized. Is detected.

  A wafer that is opaque to visible light, such as a Si wafer, does not transmit light, so that surface state defects can be detected with high accuracy. However, a wafer that is semi-transparent to visible light, such as a SiC wafer, can be used as an inspection stage. Incident light is transmitted through the SiC wafer mounted directly above, and reflected light from scratches or foreign matters with high reflectivity existing on the surface of the inspection stage is detected, so only defects on the surface of the SiC wafer that should be detected originally are detected. In addition, scratches or foreign matters on the surface of the inspection stage are also detected as defects (pseudo defects). For this reason, the original detection accuracy is lowered, and as a result, feedback accuracy is lowered and a delay is caused to improve the yield.

  The above-described problems are not limited to the lamp light emission type wafer inspection apparatus. For example, the wafer is irradiated with a laser beam having a predetermined wavelength, and the reflected light (scattered light) is detected by a detector. This is a problem that may occur even in a laser type wafer inspection apparatus.

JP 2006-329630 A

  For quick feedback of inspection results and early yield improvement, it is possible to detect only defects on the wafer surface without being affected by the surface state of the inspection stage even for semi-transparent wafers such as SiC wafers. There is a need for defect inspection equipment.

  The present invention has been made in order to solve the above-described problems, and is capable of detecting only defects on the wafer surface without being affected by the surface state of the inspection stage even on a wafer that transmits light. An object is to provide an inspection device.

  A semiconductor wafer inspection apparatus according to the present invention is a semiconductor wafer inspection apparatus for inspecting a defect of a semiconductor wafer by light, and includes an inspection stage and a wafer mounting jig placed on the inspection stage. The wafer mounting jig has a hollow cylindrical body as a main body, and a seat provided along the inner circumference on the upper surface side opposite to the side in contact with the inspection stage on the side wall of the cylinder. The semiconductor wafer is formed so as to have a diameter larger than the diameter of the semiconductor wafer to be inspected, and the back surface of the semiconductor wafer is in contact with the bottom surface of the countersink. By mounting the semiconductor wafer, the semiconductor wafer is held at a constant distance from the inspection stage, and the constant distance reflects light on the inspection stage surface for the inspection of the semiconductor wafer. It is determined on the basis of.

  According to the semiconductor wafer inspection apparatus of the present invention, since the semiconductor wafer is held at a constant distance from the inspection stage, the reflection of light from the surface of the inspection stage becomes zero or negligible. In addition, scratches or foreign matters on the surface of the inspection stage are not detected as pseudo defects, and only defects of the semiconductor wafer that should be detected can be detected accurately. In addition, since the semiconductor wafer is only mounted on the countersink, and vacuum suction is not performed, even when the semiconductor wafer is warped, wafer cracking due to suction failure or stress due to suction, Wafer cracking due to vacuum suction of a thin semiconductor wafer can be prevented.

It is sectional drawing which shows the structure of the wafer mounting jig of Embodiment 1 which concerns on this invention. It is a top view which shows the structure of the wafer mounting jig of Embodiment 1 which concerns on this invention. It is sectional drawing which shows the state which mounted the wafer in the wafer mounting jig of Embodiment 1 which concerns on this invention. It is a top view which shows the state which mounted the wafer in the wafer mounting jig of Embodiment 1 which concerns on this invention. It is a side view which shows the structure of the wafer mounting jig of Embodiment 2 which concerns on this invention. It is a top view of the wafer mounting jig of Embodiment 2 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is a figure explaining the automatic inspection method of Embodiment 3 which concerns on this invention. It is sectional drawing which shows the structure of the wafer mounting jig of Embodiment 4 which concerns on this invention. It is a top view which shows the structure of the wafer mounting jig of Embodiment 4 which concerns on this invention. It is sectional drawing which shows the state which the wafer floated in the wafer mounting jig of Embodiment 4 which concerns on this invention.

<Embodiment 1>
FIG. 1 is a cross-sectional view showing a configuration of a wafer mounting jig 10 used on the inspection stage in the defect inspection apparatus according to the first embodiment of the present invention. FIG. FIG. 3 is a plan view seen from the side opposite to the inspection stage ST, and a cross-sectional view taken along line AA in FIG. 2 corresponds to FIG. In FIG. 2, the inspection stage ST is omitted.

  As shown in FIGS. 1 and 2, the wafer mounting jig 10 has a hollow cylindrical body as a main body, and the side wall 1 of the cylinder is a counterbored portion provided along the inner periphery on the upper surface side. 11 and is arranged so that the lower surface side end surface is in contact with the upper surface of the inspection stage ST. The wafer mounting jig 10 is fixed to the upper surface of the inspection stage ST with, for example, a screw (not shown), but the fixing method is not limited to this. Note that the surface of the inspection stage ST, which is generally made of metal, schematically shows that there are scratches SC, foreign objects FO, and the like as elements that cannot be completely deleted.

  The countersink portion 11 is formed to have a diameter larger than the diameter of the wafer so that the wafer can be mounted, and the wafer is mounted so that the back surface of the wafer is in contact with the bottom surface portion 111 of the countersink portion 11. Thus, the wafer is held in the countersink 11 and the wafer is positioned with an accuracy determined by the dimensional tolerance of the diameter of the countersink 11. Note that the height of the side surface portion 112 of the counterbore portion 11 is set to be equal to or higher than the thickness of the wafer.

  FIG. 3 is a cross-sectional view showing a state in which the wafer WF is mounted on the wafer mounting jig 10, and FIG. 4 is a plan view of the wafer mounting jig 10 viewed from the upper surface side in this state. Here, the wafer WF is intended for wide band gap semiconductor wafers such as SiC wafers and GaN wafers, and these wafers have the property of transmitting part of visible light or laser light of a predetermined wavelength (semi-transmission). doing.

  As shown in FIG. 3, the wafer WF held in the counterbore 11 is not fixed by vacuum suction or the like. In addition, by holding the wafer WF in the counterbore part 11, the region surrounded by the wafer WF and the side wall 1 is in a hollow state, and a constant distance is maintained between the wafer WF and the surface of the inspection stage ST. Yes. An example of this distance is about 500 μm. However, the distance is not limited to this, and the distance may be set such that the reflection amount of light on the surface of the inspection stage ST is as small as possible. It can be large or small.

  In this state, light (visible light) emitted from a light source such as a xenon lamp or laser light having a predetermined wavelength is incident from above the wafer WF, the reflected light is detected, and an image is recognized to detect a substrate defect of the wafer WF. However, the space between the wafer WF and the surface of the inspection stage ST is hollow as described above, and the reflection of light from the surface of the inspection stage ST is zero or negligibly small. The scratch SC or foreign material FO is not detected as a pseudo defect, and only the substrate defect of the wafer WF to be detected can be detected accurately.

  Further, in the wafer mounting jig 10, the wafer WF is only mounted on the bottom surface portion 111 of the countersink portion 11 and is not vacuum-sucked. Therefore, even when the wafer WF is warped, suction failure during vacuum suction or Wafer cracking due to stress due to suction, and wafer cracking due to vacuum suction of a thin wafer can be prevented.

<Embodiment 2>
The wafer mounting jig 10 according to the first embodiment described above may be configured such that the wafer WF can be easily mounted and removed by cutting out a part of the side wall.

  FIG. 5 is a side view showing a configuration of a wafer mounting jig 10A used on the inspection stage in the defect inspection apparatus according to the first embodiment of the present invention. FIG. 6 shows the wafer mounting jig 10A on the upper surface side. FIG. 5 is a plan view seen from the side, and a side view from the direction of arrow Y in FIG. 6 corresponds to FIG. In FIG. 6, the inspection stage ST is omitted. The bottom surface portion 111A and the side surface portion 112A of the counterbore portion 11A are the same as the bottom surface portion 111 and the side surface portion 112 of the wafer mounting jig 10.

  As shown in FIGS. 5 and 6, the wafer mounting jig 10 </ b> A has a notch NP in which a part of the side wall 1 </ b> A is notched with a certain width from the upper surface side end surface to the lower surface side end surface. Since the notch NP completely removes the side wall 1A in the thickness direction (diameter direction), the inner surface of the opposite side wall of the wafer mounting jig 10A can be seen.

  By adopting such a configuration, the following operations are possible when the wafer WF is mounted on the wafer mounting jig 10A. That is, when the vacuum suction surface of the air tweezers is attracted to the back surface of the wafer WF, the wafer WF is transferred onto the wafer mounting jig 10A and mounted on the wafer mounting jig 10A, the air tweezers are adsorbed while the wafer WF is adsorbed. Is inserted into the notch NP from the upper side of the notch NP, and the wafer is mounted so that the position of the air tweezers is finely adjusted so as to be in contact with the bottom surface 111A of the countersink 11A of the wafer mounting jig 10A. Then, when the wafer is held in the counterbore 11A, the vacuum suction of the air tweezers is released, and the air tweezers are extracted through the notch NP. When taking out the wafer WF from the wafer mounting jig 10A, the reverse operation may be performed.

  As described above, by using the wafer mounting jig 10A, the wafer WF can be mounted and taken out through the notch NP, so that a vacuum of a transfer jig such as air tweezers is formed on the front surface (device forming surface) of the wafer WF. Surface contamination due to the suction surface being sucked and the wafer WF being transported can be prevented, and the loading and unloading operations of the wafer WF can be facilitated.

  If such an operation is performed, the distance between the wafer and the surface of the inspection stage ST must be at least larger than the maximum thickness of the vacuum suction portion of the air tweezers.

<Embodiment 3>
In conventional automatic wafer inspection, the wafer to be inspected is vacuum-sucked by an arm-shaped jig from the cassette in which the wafer to be inspected is set, transported onto the inspection stage, and mounted on the inspection stage. . Then, the wafer is inspected by vacuum-sucking a part or the entire surface of the wafer immediately above the inspection stage. Wafer defects detected by this inspection method include pseudo defects due to scratches or foreign matter on the inspection stage, and there is a problem that detection accuracy is low.

  On the other hand, by applying the wafer mounting jig 10A of the second embodiment described above to an inspection apparatus provided with an arm transfer mechanism, the inspection throughput can be improved by automatic transfer of wafers and the inspection stage can be improved. Since a pseudo defect due to scratches or foreign matter is not detected, high detection accuracy can be obtained.

  Hereinafter, the automatic inspection method according to the third embodiment of the present invention will be described with reference to FIGS.

  FIG. 7 is a side view of the wafer mounting jig 10A, and the notch NP is not visible because it is on the left side of the drawing, and is indicated by a broken line. FIG. 8 is a plan view of the state in which the wafer WF is automatically transferred toward the wafer mounting jig 10A as viewed from above, and the wafer WF is mounted on the transfer arm AM having a vacuum suction function. . A vacuum suction unit is provided at the tip of the transfer arm AM, and the back surface of the wafer WF is vacuum-sucked, but the vacuum suction unit is not shown. In addition, the side view from the arrow Z direction in FIG. 8 corresponds to FIG.

  FIG. 9 is a side view of the state in which the wafer WF mounted on the transfer arm AM has been transferred to the wafer mounting jig 10A. The transfer arm AM is located above the notch NP. The transport arm AM is inserted into the notch NP by lowering the transport arm AM.

  FIG. 10 is a side view showing a state in which the transfer arm AM is lowered and inserted into the notch NP, and the wafer WF is held in the countersink 11A. FIG. 11 shows the wafer mounting jig in this state. It is the top view which looked at 10A from the upper surface side.

  As shown in FIGS. 10 and 11, when the wafer WF is held in the countersunk portion 11A, the wafer is positioned with an accuracy determined by the dimensional tolerance of the diameter of the countersink 11A.

  Thereafter, the vacuum suction of the transfer arm AM is released, and the transfer arm AM is extracted through the notch NP. FIG. 12 is a side view showing a state in which the transfer arm AM is extracted and moved through the notch NP. FIG. 13 is a plan view of the wafer mounting jig 10A with the transfer arm AM extracted as viewed from the upper surface side.

  As shown in FIG. 12, the wafer WF held in the counterbore 11A is not fixed by vacuum suction or the like.

  In this state, visible light emitted from a light source such as a xenon lamp or a laser beam having a predetermined wavelength is incident from above the wafer WF, the reflected light is detected, and an image is recognized to detect a substrate defect of the wafer WF. Since the space between the WF and the surface of the inspection stage ST is hollow as described above, the amount of light reflected from the surface of the inspection stage ST is zero or negligibly small. Therefore, only the substrate defect of the wafer WF that should be detected can be accurately detected.

  Further, in the wafer mounting jig 10A, the wafer WF is only mounted on the countersink portion 11, and is not vacuum-sucked. Therefore, even when the wafer WF is warped, suction failure during vacuum suction and stress due to suction are affected. It is possible to prevent wafer cracking due to wafer cracking due to vacuum suction of a wafer having a small thickness.

  When the wafer WF is taken out of the wafer mounting jig 10A after the inspection of the wafer WF is completed, the transfer arm AM is inserted into the notch NP and the wafer WF is vacuum-sucked, and then the operation opposite to that for mounting is performed. To remove the wafer WF.

  Thus, by applying the wafer mounting jig 10A to an inspection apparatus provided with an arm transfer mechanism, the inspection throughput by automatic transfer of the wafer WF is improved.

<Modification>
The wafer mounting jig 10A described above has a configuration in which a part of the side wall 1A is a notch NP that is notched with a constant width from the upper surface side end surface to the lower surface side end surface. For example, a configuration may be adopted in which a part of the wafer WF is removed from the upper surface side end face with a constant width corresponding to the thickness of the wafer WF plus the height at which the transfer arm can be inserted and removed.

  In addition, the wafer mounting jig 10A described above has a configuration in which one notch NP is provided on the side wall 1A. However, when applied to a transport method other than arm transport, such as a belt transport method, A similar notch may be provided at a location facing the notch NP, and the conveyor belt may be provided so as to extend over the two notches. In this case, the transport belt is provided on the inspection stage, but detection of the transport belt is prevented by increasing the distance between the wafer and the inspection stage. Further, the number and arrangement of the notches are not limited as described above, and may be set in accordance with the transport method.

<Embodiment 4>
In the wafer mounting jig 10 according to the first embodiment, when taking out the wafer WF from the wafer mounting jig 10, for example, a method is adopted in which the vacuum suction surface of the air tweezers is adsorbed to the front surface of the wafer WF and taken out. A configuration that facilitates mounting and taking out the wafer WF by providing a mechanism that blows gas to the back surface of the wafer WF to float the wafer WF may be employed.

  FIG. 14 is a cross-sectional view showing a configuration of a wafer mounting jig 10B used on the inspection stage in the defect inspection apparatus according to the third embodiment of the present invention. FIG. 15 shows the wafer mounting jig 10B on the upper surface side. FIG. 14 is a plan view seen from FIG. 14, and a sectional view taken along line BB in FIG. 15 corresponds to FIG. Note that the inspection stage ST is omitted in FIG.

  As shown in FIGS. 14 and 15, the wafer mounting jig 10 </ b> B has a configuration in which a plurality of gas blowing holes OP are provided on the bottom surface portion 111 </ b> B of the countersink portion 11 </ b> B provided on the upper surface side of the cylindrical side wall 1 </ b> B. ing. The side surface portion 112B of the counterbore portion 11B is the same as the side surface portion 112 of the wafer mounting jig 10.

  The plurality of gas blowing holes OP are provided along the circumference of the bottom surface part 111B, and each of the vertical holes 12 provided so as to extend vertically from the bottom surface part 111B toward the inspection stage ST side. An opening is formed. Each of the vertical holes 12 communicates with a horizontal hole 14 provided so as to extend in the diameter direction of the wafer mounting jig 10B inside the side wall 1B.

  Moreover, the gas flow path 13 is provided in the side wall 1B along the circumference of the side wall 1B. The gas flow path 13 is provided at a position near the outer periphery of the side wall 1B on the lower side of the side wall 1B, and communicates with the plurality of lateral holes 14.

  The gas flow path 13 communicates with the gas introduction part 15 inserted in the diameter direction of the side wall 1B from the outside of the side wall 1B, and the gas (air, nitrogen) GS introduced from the gas introduction part 15 is It is configured to blow out from the gas blowing hole OP through the gas flow path 13, the horizontal hole 14 and the vertical hole 12. In addition, the gas flow path 13, the horizontal hole 14, and the vertical hole 12 can be named generically as a gas flow path.

  FIG. 16 is a cross-sectional view showing a state in which the wafer WF is lifted above the wafer mounting jig 10B by the gas GS blown from the gas blowing hole OP. As shown in FIG. 16, the wafer WF is lifted to a position higher than the upper end surface of the side wall 1B, so that a transfer jig such as an air tweezer is inserted from the gap between the side wall 1B and the back surface of the wafer WF. It is possible to vacuum-suck the back surface of the substrate with a conveying jig.

  The above configuration can be used not only when the wafer WF is taken out from the wafer mounting jig 10B but also when it is mounted. That is, the gas GS is blown out from the gas blowing hole OP, the wafer WF whose back surface is vacuum-sucked by the transport jig is transported to above the wafer mounting jig 10B, the vacuum suction of the transport jig is released, After the wafer WF is lifted, the blowing pressure of the gas GS is gradually reduced so that the wafer WF is held in the countersink portion 11B.

  As described above, by using the wafer mounting jig 10B, the wafer WF can be mounted and taken out in a floating state. Therefore, the vacuum suction surface of a transfer jig such as an air tweezer is adsorbed on the front surface of the wafer WF. Surface contamination due to the transfer of the wafer WF can be prevented, and the loading and unloading operations of the wafer WF can be facilitated.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  1, 1A, 1B Side wall, 10, 10A, 10B Wafer mounting jig, 11, 11A, 11B Countersink part, 111, 111A, 111B Bottom surface part, AM transfer arm, OP gas blowing hole, ST inspection stage.

Claims (5)

A semiconductor wafer inspection apparatus for inspecting defects of a semiconductor wafer by light,
Inspection stage,
A wafer mounting jig placed on the inspection stage,
The wafer mounting jig has a hollow cylinder as a main body, and a countersink provided along an inner circumference on an upper surface side opposite to a side in contact with the inspection stage on a side wall of the cylinder. Part
The counterbored portion is formed with a diameter larger than the diameter of the semiconductor wafer to be inspected, and by mounting the semiconductor wafer so that the back surface of the semiconductor wafer is in contact with the bottom surface of the counterbored portion, The semiconductor wafer is held at a certain distance from the inspection stage,
The apparatus for inspecting a semiconductor wafer, wherein the fixed distance is determined based on a reflection amount of light for inspecting the semiconductor wafer on a surface of the inspection stage. The wafer mounting jig is
2. The semiconductor wafer inspection apparatus according to claim 1, further comprising a cutout portion NP cut out from a part of the side wall from an upper surface side end surface to a lower surface side. The notch is
The semiconductor wafer inspection apparatus according to claim 2, wherein the side wall is cut out from an upper surface side end surface to a lower surface side end surface. The wafer mounting jig is
A plurality of gas blowing holes provided in the bottom surface portion of the countersunk portion of the side wall;
The plurality of gas blowing holes are provided along the circumference of the bottom surface portion, each communicating with a gas flow path provided inside the side wall, and from the outside of the wafer mounting jig to the gas flow path. The semiconductor wafer inspection apparatus according to claim 1, wherein the supplied gas is blown out. A semiconductor wafer automatic inspection method using the semiconductor wafer inspection apparatus according to claim 2,
The semiconductor wafer inspection apparatus comprises:
An arm transport mechanism for loading and unloading the semiconductor wafer with respect to the wafer mounting jig placed on the inspection stage;
(A) placing the semiconductor wafer on the transfer arm of the arm transfer mechanism so that the back surface is in contact with the transfer arm and transferring the wafer to above the wafer mounting jig;
(B) lowering the transfer arm so as to be inserted into the notch, and holding the semiconductor wafer in the countersink;
(C) extracting the transfer arm through the notch,
And (d) detecting a defect of the semiconductor wafer by causing light for inspection of the semiconductor wafer to enter from above the semiconductor wafer, detecting the reflected light, and recognizing an image. Automatic inspection method.

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