JP6286256B2 - Wafer marking / grinding apparatus and wafer marking / grinding method - Google Patents

Description

  The present invention relates to a wafer marking / grinding apparatus and a wafer marking / grinding method, and more particularly to a wafer marking / grinding apparatus for forming a mark indicating a crystal orientation of a semiconductor wafer on a wafer and a wafer marking / grinding method using the apparatus. .

  Conventionally, in order to improve the productivity of IC, LSI, etc., the effective area of the semiconductor wafer is reduced. Instead of orientation flat (orientation flat) to indicate the crystal orientation of the semiconductor wafer, Notches, which are small notches formed, have been used.

However, when the notch is used as a method for indicating the crystal orientation of the semiconductor wafer, there arises a problem that processing distortion when the notch is formed tends to remain on the wafer, and a problem that the semiconductor wafer easily breaks based on the notch. .
Therefore, in recent years, a method has been developed in which a mark is formed on a wafer with a laser using the notch as a reference, the mark is used as a mark indicating the crystal orientation of the wafer, and then the notch is removed by chamfering grinding.

The manufacturing method of a notchless wafer uses a wafer marking / grinding method as shown below.
(1) Chamfer the outer cylinder of the ingot,
(2) The crystal orientation of the ingot is measured to form a notch at a predetermined crystal orientation,
(3) Thereafter, the ingot is sliced into a disk shape to cut out the wafer,
(4) forming a mark at a position of a predetermined crystal orientation on the wafer surface;
(5) Chamfering the wafer to remove the notch,
(6) A notchless wafer is manufactured by removing processing distortion of the wafer by etching.

  As a method for manufacturing a notchless wafer using such a wafer marking / grinding method, Patent Document 1 discloses that a shallow notch extending in the axial direction of an ingot is engraved at a predetermined crystal orientation position in a peripheral surface polishing step. A method of manufacturing a notchless wafer, wherein a crystal orientation mark is engraved by laser marking at a predetermined position on a wafer sliced from a notch as a reference, and then the notch is removed by chamfering processing to form a perfect circular wafer Is disclosed.

  As a result, the engraving position of the crystal orientation mark is determined based on the notch, so that it is possible to manufacture a notchless wafer without subjecting each wafer to an X-ray diffractometer as in the prior art.

JP-A-10-256106

  However, in the conventional wafer marking / grinding method disclosed in Patent Document 1, chamfering is performed with another apparatus after forming a mark on the wafer, so that highly accurate mark forming and chamfering are difficult. It was. More specifically, when mark formation and chamfering are performed by another apparatus, in the mark formation, the center position of the wafer is measured and calculated, and mark formation is performed based on this and the notch. When the wafer is transferred to the apparatus, the center position of the wafer measured and calculated by the mark forming apparatus is not taken over, and therefore the wafer center is remeasured and recalculated by the chamfering apparatus.

  In this case, measurement and calculation of the center of the wafer is performed with different equipment, so there will always be variations and the same result will not be obtained, so processing will be performed based on the center position of the different wafer, making high-precision processing difficult. It was.

  Alternatively, some chamfering devices recognize a mark formed by a wafer marking / grinding device as a reference. In this case, variation due to a difference in recognition criteria occurs.

For example, the conventional wafer marking / grinding method disclosed in Patent Document 1 has a problem that the position of the mark from the outer periphery of the wafer after chamfering varies from wafer to wafer.
In view of the actual situation, the present invention intends to provide a wafer marking / grinding apparatus and a wafer marking / grinding method capable of reducing variations in wafer processing.

The above problems can be solved by the following inventions.
That is, the wafer marking / grinding apparatus of the present invention comprises a wafer positioning means for positioning the wafer from the outer periphery of the wafer, a holding means for holding the wafer positioned by the wafer positioning means and having a notch formed on the outer periphery, A mark is formed at a predetermined position on the wafer surface determined on the basis of the notch position detected by the notch detection means on the notch detection means for detecting the notch and the holding means on which the wafer is placed. And a marking means for rotating the wafer while maintaining the center of rotation of the wafer on the holding table on which the marking is performed as a center, and grinding and removing the outer periphery of the wafer including the notch. Features.
As a result, grinding is performed by rotating the wafer while maintaining the center of rotation of the wafer on the holding table on which the marking has been performed as the center, so that the position of the center of rotation of the wafer is the same during both marking and grinding. Mark forming processing and wafer chamfering processing can be performed.

The wafer marking / grinding apparatus of the present invention further comprises holding means for holding the wafer by the marking means, and holding means for holding the wafer by the grinding means, which is different from the holding means, The main feature is that it has a wafer transfer means for transferring the wafer while maintaining the center position of the wafer between the holding means of the marking means and the holding means of the grinding means.
Accordingly, since the wafer can be transferred while maintaining the center position of the wafer between the holding means of the marking means and the holding means of the grinding means, the same center position of the wafer can be used in both the marking means and the grinding means. Processing can be performed based on the above. Therefore, in the wafer after peripheral grinding, it is possible to suppress variations in mark positions between the wafers.

Further, the wafer marking / grinding method of the present invention includes a wafer positioning step for positioning the wafer from the outer periphery of the wafer, and a holding device that holds the wafer that is positioned in the wafer positioning step and has a notch formed on the outer periphery. A notch detecting step for detecting the notch, and a predetermined position on the wafer surface determined on the basis of the notch position detected by the notch detecting step on the holding means on which the wafer is placed. A marking step for forming a mark, and a grinding step for grinding and removing the outer periphery of the wafer including the notch by rotating the wafer while maintaining the rotation center of the wafer on the holding table on which the marking has been performed as a center. This is the main feature.
As a result, grinding is performed by rotating the wafer while maintaining the center of rotation of the wafer on the holding table on which the marking has been performed as the center, so that the position of the center of rotation of the wafer is the same during both marking and grinding. Mark forming processing and wafer chamfering processing can be performed.

Furthermore, in the wafer marking / grinding method of the present invention, the wafer holding step for holding the wafer using the holding means in the marking step and the holding means different from the holding means are used to hold the wafer in the grinding step. A wafer holding step for transferring the wafer while maintaining the center position of the wafer between the marking step holding means and the grinding step holding means. It is a feature.
Accordingly, since the wafer can be transferred while maintaining the center position of the wafer between the holding means of the marking means and the holding means of the grinding means, the same center position of the wafer can be used in both the marking means and the grinding means. Processing can be performed based on the above. Therefore, in the wafer after peripheral grinding, it is possible to suppress variations in mark positions between the wafers.

  Provided are a wafer marking / grinding apparatus and a wafer marking / grinding method capable of reducing variations in wafer processing.

It is a schematic block diagram for demonstrating the structure of a chamfering part. It is a block diagram of one Embodiment of a control means. It is explanatory drawing which shows the wafer shape after etching a round-shaped wafer (roundness 1 micrometer). It is explanatory drawing which shows the shape after the etching of the wafer ground by the chamfer. It is a schematic block diagram for demonstrating the structure of a mark formation part. It is explanatory drawing for demonstrating the notch position and mark position on a wafer. It is a schematic plan view of a wafer. It is a schematic plan view of a wafer. It is a block diagram of an example of a center position calculation means. It is the top view which showed the center of a wafer, the center of a holding means, and the center calculated | required by calculation. It is the top view which showed the center of a wafer, the center of a holding means, and the center calculated | required by calculation. It is an example of the information (grinding condition information) regarding the difference in the etching rate depending on the crystal orientation of the wafer. It is explanatory drawing for demonstrating grinding (chamfering) of the wafer by a grindstone. It is a flowchart which shows the mark formation to the conventional wafer, and the flow of outer periphery grinding. It is a flowchart which shows the flow of embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. Here, in the drawing, portions indicated by the same symbols are similar elements having similar functions. In the present invention, when the range of values is expressed using “to”, the values of both the boundaries are included in the range.

<Configuration>
The wafer marking / grinding apparatus according to the present invention includes a wafer positioning unit that positions the wafer from the outer periphery of the wafer, a holding unit that holds the wafer that is positioned by the wafer positioning unit and has a notch formed on the outer periphery, and the notch Marking for forming a mark at a predetermined position on the wafer surface determined on the basis of the notch position detected by the notch detection means on the holding means on which the wafer is placed And a grinding means for rotating the wafer while maintaining the center of rotation of the wafer on the holding table on which the marking has been performed as a center, and grinding and removing the outer periphery of the wafer including the notch. The

  The wafer positioning means is a means for determining and setting the position where the wafer is set on the holding means. For example, the wafer positioning means may be composed of a center position calculating means and a wafer mounting means, which will be described later, but is not limited thereto. It is an apparatus for setting and positioning an appropriate wafer position according to the purpose of the apparatus.

  The holding means is an apparatus for holding the wafer, and includes a vacuum chuck or the like, which will be described in detail later. The notch detection means is an apparatus for detecting a notch formed on the wafer, and a laser detector or the like can be employed, which will be described later.

  The marking means is an apparatus for forming a mark on a wafer, and a laser irradiator or the like can be used. This will also be described later. The grinding means is a device for grinding the outer periphery of the wafer, and a rotating grinding wheel or the like can be adopted. This will also be described later.

  The wafer marking / grinding apparatus of the present invention can be separately provided with a holding means for holding the wafer in the marking means and a holding means for holding the wafer in the grinding means. In this case, it is necessary to have wafer transfer means for transferring the wafer while maintaining the center position of the wafer with each holding means.

  As the wafer transfer means, it is possible to employ an apparatus normally used for transferring a wafer and a wafer mounting means described later. An apparatus normally used for transporting a wafer can be composed of an arm that can vacuum-suck a wafer and a step motor that moves the arm in the X-axis direction, Y-axis direction, and Z-axis direction, but is not limited to this. Instead, various commercially available wafer transfer apparatuses can be used.

  The wafer marking / grinding apparatus of the present invention may have the following configuration. That is, the wafer marking / grinding apparatus of the present invention includes a mark forming part for forming a mark on the wafer, a chamfering part for grinding the outer periphery of the wafer, a center position calculating means for calculating the center position of the wafer from the outer shape of the wafer, A holding unit for holding the wafer and a wafer mounting unit for mounting the wafer on the holding unit may be provided.

  Further, at least the chamfered portion includes the holding unit, and the wafer mounting unit holds the wafer so that the center of the wafer whose center position is calculated by the center position calculating unit coincides with the center of the holding unit. It may be placed on the means. Here, the center of the holding means is the center of rotation when the holding means is rotated. Hereinafter, the chamfered portion and the mark forming portion will be described with reference to the drawings.

(1) Chamfered part The chamfered part which comprises the wafer marking and grinding apparatus of this invention is demonstrated with reference to drawings. FIG. 1 is a schematic configuration diagram for explaining the configuration of the chamfered portion.

  As shown in FIG. 1, the chamfered portion 10 constituting the wafer marking / grinding apparatus of the present invention includes a holding rotating means 12 for holding and rotating the wafer 1, a grinding means 14 for grinding the outer periphery of the wafer 1, and a grinding means. The moving means 16 for moving the grinding means 14 from the outer peripheral edge of the wafer 1 toward the center of the wafer 1 and the control means 18 for controlling the moving means 16 are mainly moved. It is prepared for.

  The holding and rotating means 12 can be composed of a holding means 12 a that holds the wafer 1 and a rotating means 12 b that rotates the wafer 1. The holding means 12 a can fix the wafer 1 by adopting means usually used for fixing the wafer.

  For example, the wafer 1 can be sucked and fixed by vacuum suction, or can be fixed by mechanically sandwiching it with a jig or the like, but is not limited thereto. The rotating means 12b can be constituted by a motor, for example, and the wafer 1 can be rotated by rotating the holding means 12a.

  The grinding means 14 can be composed of, for example, a grindstone 14a and a grindstone rotating means 14b. However, it is not limited to this, and it may be composed only of the grindstone 14a. Further, when the grindstone rotating means 14b is used, the rotation direction of the grindstone may be the same direction as the rotation direction of the wafer 1 or may be the reverse direction (in FIG. 1, the reverse rotation direction is indicated by an arrow). ).

  Further, only the grindstone 14a rotates to grind the wafer 1, and the rotating means 12b may be used only for directing the portion of the outer periphery of the wafer 1 to be ground toward the grindstone 14a. This may be determined as one of appropriate conditions in setting the grinding conditions for the wafer 1.

  The moving means 16 is for making the grinding means 14 relatively close to and in contact with the wafer 1 to chamfer the wafer 1 (peripheral grinding). For example, a stepping motor, a ball screw, It can be composed of a moving table. In FIG. 1, the moving means 16 is connected to the grinding means 14 and described to move the grinding means 14, but the moving means 16 is connected to the holding and rotating means 12 and moves the holding and rotating means 12. It is also possible to adopt a configuration that allows

  The control means 18 is constituted by, for example, a computer or a control LSI, and grinds the wafer 1 by controlling at least the movement means 16 among the holding rotation means 12, the grinding means 14, and the movement means 16. At this time, the control means 18 is based on the information on the difference in the etching rate depending on the crystal orientation of the wafer 1 in the wafer etching step performed after the chamfering step, and from the portion of the outer periphery of the wafer 1 where the etching rate is fast. In this case, the wafer 1 is ground by controlling the grinding means 14 so that the wafer 1 becomes a perfect circle after the etching by grinding more portions with a low etching rate. Here, it is preferable that the control unit 18 controls not only the moving unit 16 but also the holding and rotating unit 12 in association with the control of the moving unit 16, and not only the moving unit 16 but also the holding and rotating unit 12 and the grinding unit 14. Is most preferably controlled in association with the moving means 16.

  One embodiment of the control means 18 will be further described with reference to FIG. FIG. 2 is a block diagram of an embodiment of the control means. The control means 18 can be configured mainly including a CPU (Central Processing Unit) 20, a memory 22, and an input means 24. An external storage device 26 may be further provided.

  As the input means 24, what is normally used as an input means of a computer, such as a keyboard and a mouse, can be employed. As the external storage device 26, a hard disk drive, a CDROM drive, a DVDROM drive, a smart media drive, or the like that is normally used as an external storage device of a computer can be employed.

  Information regarding the difference in the etching rate depending on the crystal orientation of the wafer 1 (hereinafter referred to as grinding condition information) is set in the control means 18. The control means 18 stores the grinding condition information input from the input means 24 in the memory. 22 or the external storage device 26. Here, the setting of the grinding condition information to the control means 18 is not performed by inputting from the input means 24 but by setting a storage medium storing the grinding condition information in the external storage device 26. Alternatively, the grinding condition information may be input from the outside to the memory 22 or the external storage device 26 by infrared communication, Wi-Fi communication, other wireless communication, or wired communication.

  Further, the input information (grinding condition information) regarding the difference in etching rate depending on the crystal orientation of the wafer 1 may be, for example, the etching rate for each crystal orientation of the wafer, or the etching rate for each crystal orientation of the wafer. Or a ratio of the amount to be ground for each crystal orientation of the wafer. In other words, any information regarding the grinding conditions may be used as long as the shape of the etched wafer becomes a perfect circle by etching the ground wafer based on these conditions.

  Next, the difference in etching rate depending on the crystal orientation of the wafer 1 will be described with reference to FIGS. FIG. 3 is an explanatory view showing the shape of the wafer after etching. FIG. 3 is an explanatory view showing a wafer shape after etching a round-shaped wafer (roundness of about 1 μm), and FIG. 4 is an explanatory view showing a shape after etching of the wafer ground by the chamfered portion. . In any case, for the sake of easy understanding, the features of the wafer shape are exaggerated and not shown in the scale.

  As shown in FIG. 3, the roundness of the wafer 30 after chamfering is about 1 μm, but the roundness of the wafers 32 and 34 after etching deteriorates to about 10 μm. The reason is that, since the etching rate varies depending on the crystal direction of the wafer, a large crystal direction with a high etching rate is etched, and a low crystal direction with a low etching rate is etched.

  The wafer shapes after etching indicated by the wafers 32 and 34 show an example. The shape of the wafer after etching differs depending on the type of etchant used and the cutting direction of the wafer, that is, depending on which crystal orientation the outer periphery of the wafer has been cut from the ingot.

  Next, a description will be given with reference to FIG. Since the wafer 40 ground by using the chamfered portion 10 of the wafer marking / grinding apparatus of the present invention is ground with a small crystal direction with a high etching rate and ground with a large crystal direction with a low etching rate, a grinding process (chamfering) is performed. After completion), the roundness is about 10 μm. By etching the wafer 40, a round wafer 42 (roundness of about 1 μm) can be manufactured.

  The shape of the wafer 40 ground by using the chamfered portion 10 of the wafer marking / grinding apparatus of the present invention shown in FIG. 4 is shown exaggerating the features ignoring the scale in order to show the features of the shapes in an easy-to-understand manner. is there. Further, the shape of the wafer 40 shown in FIG. 4 is an example, depending on the type of etching solution used and the cutting direction of the wafer, that is, depending on which crystal orientation the outer periphery of the wafer is cut from the ingot. Come different.

  Thus, since the chamfered portion 10 of the wafer marking / grinding apparatus of the present invention has means for storing grinding condition information, in other words, the storage means for storing grinding condition information is provided. Therefore, based on this grinding condition information, the control means 18 can grind the wafer by controlling at least the moving means 16 so that the wafer 40 becomes a perfect circle after etching.

  Returning to FIG. 1, an example of specific control of the control means 18 based on the grinding condition information will be described. Based on information about which crystal direction of the outer periphery of the wafer 1 is directed to the grinding means 14, the control means 18 moves toward the center of the wafer so that a large amount can be ground in the crystal direction to be ground. The moving means 16 is controlled to move less so that less is moved in the crystal direction to be ground.

  Which crystal direction of the outer periphery of the wafer 1 is directed to the grinding means 14 can be determined by detecting the position of the notch of the wafer 1, for example, and is formed based on the position of the notch described later. This can be known by recognizing the position of the mark on the wafer 1.

  Further, when the crystal orientation of the wafer is recognized once by recognizing the position of the notch or the mark, for example, a rotary encoder is installed in the holding and rotating means 12, or a stepping motor is used in the rotating means 12b. Thus, the rotation angle of the wafer 1 can be known in real time, and from this, it can be known which crystal orientation of the wafer 1 is directed toward the grinding means 14.

(2) Mark formation part Next, the mark formation part which comprises the wafer marking and grinding apparatus of this invention is demonstrated with reference to FIG. FIG. 5 is a schematic configuration diagram for explaining the configuration of the mark forming unit. The mark forming unit 50 forms a mark 56 on the surface of the wafer 51, a holding rotation means 52 for holding and rotating the wafer 51, a notch detection means 54 for detecting the position of the notch 53 of the wafer 51, and the surface of the wafer 51. And a marking means 58 for the purpose.

  The holding and rotating means 52 can be constituted by a holding means 52 a that holds the wafer 51 and a rotating means 52 b that rotates the wafer 51. The holding means 52 a can fix the wafer 51 by adopting means usually used for fixing the wafer.

  For example, the wafer 51 can be sucked and fixed by vacuum suction, or can be fixed by mechanically sandwiching it with a jig or the like, but is not limited thereto. The rotating means 52b can be constituted by a motor, for example, and the wafer 51 can be rotated by rotating the holding means 52a.

  Here, the holding and rotating means 52 of the mark forming unit 50 may be configured separately from the holding and rotating means 12 shown in FIG. 1 or may be the same body. When configured as a separate body, a transfer means for moving the wafer 51 held by the holding rotation means 52 to the holding rotation means 12 shown in FIG. 1 is required.

  In the case where the mark forming unit 50 is configured as a separate body, it is necessary that the mark forming unit 50 includes a center position calculating unit described later. The reason for this will also be described later.

  Returning to FIG. 5, the notch detection means 54 is usually used to detect the notch position of the wafer, such as an optical sensor such as a laser sensor or a mechanical sensor that mechanically detects the notch position. Although a sensor can be used, it is preferable to use a laser sensor that can detect a notch position with high accuracy without contact. The notch detection means 54 shown in FIG. 5 is a transmissive laser sensor, and detects the notch position depending on whether or not the lower light receiving unit 57 receives the laser beam emitted from the upper laser irradiation unit 55.

  The marking unit 58 is configured by, for example, a laser irradiation apparatus, and forms a mark at a predetermined position on the surface of the wafer 51 determined based on the notch position detected by the notch detection unit 54. Here, in FIG. 5, the position of the notch 53 of the wafer 51 and the position of the mark 56 formed by the marking means 58 are drawn so as to be nearly 180 degrees apart. It is only drawn and it is actually preferable to form it near the notch 53.

  The position of the mark to be formed will be further described with reference to FIG. FIG. 6 is an enlarged schematic plan view of a wafer for explaining notch positions and mark positions on the wafer. FIG. 6 is an enlarged plan view showing a part of the wafer, but the scale is exaggerated for easy understanding.

  As shown in FIG. 6, a notch 53 having a notch shape is formed at the outer peripheral end of the wafer 51 in a predetermined crystal orientation. The mark 56 formed by the marking means 58 is on a straight line 66 that is deviated from the line segment 62 connecting the center 60 of the wafer 51 and the notch 53 by a predetermined angle θ (indicated by symbol 64) in the circumferential direction of the wafer 51. It is formed. This angle θ is being studied in a direction that is internationally unified at 5.0 ° ± 0.1 ° according to the international standardization process.

  The mark 56 is formed on the straight line 66 at a position away from the center 60 of the wafer by a predetermined distance. Thereby, the mark 56 is formed at a position close to the center 60 by a certain distance from the outer periphery of the wafer after the chamfering process by the grinding means 14 shown in FIG. 1 performed after the process of forming the mark 56. it can. Alternatively, the mark 56 can be formed at a position close to the center 60 by a certain distance from the outer peripheral position 68 of the wafer after the etching process.

  Whether the mark 56 is formed at a certain distance from the wafer outer peripheral position 68 after the etching process or the mark 56 is formed at a certain distance from the outer peripheral position of the wafer after the chamfering process is selected in the present invention. The mark 56 can be formed in this way, but it is preferable to form the mark 56 at a certain distance from the outer peripheral position 68 of the wafer after the etching process.

  As a result, a mark is formed at a position that is closer to the center of a certain distance from the outer peripheral position in all the finally manufactured wafers. When performing a semiconductor manufacturing process such as a photolithography process using this wafer, this mark is formed. Since the mark 56 can be easily detected, the positioning of the wafer using the mark 56 can be easily and accurately performed.

  In the conventional apparatus, it is impossible to form the mark 56 so as to be a certain distance from the outer peripheral position of the wafer after the chamfering process or after the etching process. The reason is as follows. That is, in the conventional apparatus, the mark forming part 50 exists as an apparatus different from the chamfered part 10.

  Therefore, (A) the algorithm for determining the center position of the wafer from the outer shape of the wafer that is separated from the perfect circle before the chamfering process is an apparatus that performs laser marking (mark forming unit) and an apparatus that performs chamfering (chamfering unit). (B) Even if the same algorithm is used for the laser marking device and the chamfering device, it is always necessary to find the center position of the wafer again after moving the wafer between devices. Variations in the mark position from the outer periphery of the wafer after the chamfering process occur due to errors and variations included in the obtained wafer center position.

  Furthermore, since the conventional chamfering apparatus cannot perform chamfering considering the shape after the etching process, the outer periphery of the wafer varies away from the perfect circle shape after the chamfering process due to the difference in the etching rate for each crystal orientation, The mark positions from the outer periphery of the wafer after the etching process were increasingly varied.

This will be further described with reference to FIG. FIG. 7 is a schematic plan view of the wafer. A solid line indicated by symbol 70 is a line indicating the outer periphery of the wafer before chamfering. A broken line indicated by a symbol 72 is a line indicating the outer periphery of the wafer after chamfering or etching. As shown in FIG. 7A, a conventional laser marking apparatus calculates a wafer center C ₁ 74 from the outer periphery 70 of the wafer before chamfering. Next, with the center C ₁ 74 as a reference, marking is performed by a laser at a position away from the notch 53 by a predetermined angle θ and at a predetermined distance L from the center C ₁ 74 to form a mark 56.

Referring to FIG. 7B, the wafer is then transferred to a chamfering apparatus, which is another apparatus, where the center of the wafer is calculated again with reference to the outer periphery 70, but for the reason described above. The center thus obtained is C ₂ 76 which is slightly shifted from C ₁ 74. Apparatus for performing chamfering performs chamfered wafer so as to have a predetermined radius r the center C ₂ 76 as the center of the circle, then for performing etching, after chamfering, or from the outer periphery of the wafer after etching to the mark 56 The distance is (r + M) -L.

The relative position of _where the _C 1 _74, and _C 2 76, the distance M between the _C 1 74 and _C 2 76 will differ for each wafer would vary for each wafer. For this reason, the distance (r + M) −L from the outer periphery 72 of the wafer after chamfering or etching to the mark 56 varies from wafer to wafer.

FIG. 7B shows an example in which C ₁ 74, C ₂ 76, and the mark 56 are on the same straight line, but the distance from the outer periphery to the mark 56 is not on the same straight line. The variation is the same.

Next, the case of the present invention will be described with reference to FIG. FIG. 8 is a schematic plan view of the wafer. A solid line indicated by symbol 70 is a line indicating the outer periphery of the wafer before chamfering. A broken line indicated by a symbol 72 is a line indicating the outer periphery of the wafer after chamfering or etching. The wafer marking / grinding apparatus of the present invention includes a center position calculating means for calculating the center position of the wafer from the outer periphery of the wafer, and as shown in FIG. 8A, the outer periphery of the wafer before chamfering by the center position calculating means. From 70, the center C ₀ 80 of the wafer is calculated. Next, with the center C ₀ 80 as a reference, marking is performed with a laser at a position away from the notch 53 by a predetermined angle θ at a predetermined distance L from C ₀ 80 to form a mark 56.

At this time, the mark 56 may be formed at a position close to C ₀ 80 by a predetermined distance from the outer peripheral position after chamfering the wafer (after wafer outer peripheral grinding) or the outer peripheral position after etching the wafer. It is calculated and calculated as possible. Specifically, in the wafer marking / grinding apparatus of the present invention, since laser marking and chamfering of the wafer are performed by the same apparatus, setting of how to chamfer the outer periphery of the wafer (how many radii of the wafer become) Information on setting of chamfering, setting of chamfering so as to form an outer periphery in consideration of the shape after etching, and the like.

  Therefore, the wafer marking / grinding apparatus of the present invention is based on this information, that is, based on the shape of the wafer after chamfering or after etching, in other words, the wafer after chamfering or after etching. By predicting the shape, L can be calculated so that the distance from the outer periphery of the wafer after chamfering or etching is a predetermined distance, and laser marking can be performed based on this L.

Referring to FIG. 8B, the wafer is then chamfered in the same apparatus. The chamfering is performed so as to have a predetermined radius r with the same center C ₀ 80 as in the laser marking as the center of the circle. As described above, in the present invention, since the laser marking and chamfering are performed based on the same wafer center C ₀ 80, the distance from the outer periphery 72 of the wafer after chamfering or etching to the mark 56 is r−. L.

  Here, since r and L do not vary depending on the wafer, the distance from the outer periphery of the wafer after chamfering or etching to the mark 56 is constant without variation between the wafers. Whether the distance from the outer periphery of the wafer after chamfering to the mark 56 is constant or whether the distance from the outer periphery of the wafer after etching to the mark 56 is constant is set in the wafer marking / grinding apparatus of the present invention. You can choose to accomplish either.

(3) Center position calculation means Next, the center position calculation means used in the present invention will be described. The center position calculating means mainly includes a wafer outer periphery measuring unit that measures the outer periphery of the wafer and an arithmetic unit that calculates the center position of the wafer from data related to the outer periphery of the wafer measured by the wafer outer periphery measuring unit. .

  A wafer sliced from an ingot has a shape close to a circular shape but is not a perfect circular shape. The center position calculating means measures the outer periphery of the incomplete circular wafer by the wafer outer peripheral portion, and based on the measurement result, the arithmetic unit obtains the center of the circle approximated to the outer periphery of the wafer as the center of the wafer. .

  This will be described with reference to FIG. FIG. 9 is a configuration diagram of an example of the center position calculation means. As shown in FIG. 9, the wafer outer periphery measuring unit mainly includes a laser sensor 92 that measures the outer periphery of the wafer 90 and an arithmetic unit 94. The holding and rotating means 12 including the holding means 12a for holding the wafer 90 and the rotating means 12b for rotating the wafer 90 is the same as that used at the time of laser marking or used at the time of wafer outer periphery grinding. It is preferable to do this, but the wafer outer periphery measurement unit may have a separate body without sharing.

  Here, in the wafer marking / grinding apparatus of the present invention, the holding and rotating means 96, 52, and 12 are used in a step of obtaining the center of the wafer, a step of performing laser marking, and a wafer outer periphery grinding step. Although it is preferable to use the same holding and rotating means in all these steps in order to reduce the error of the center position, the effects of the present invention can be achieved by performing as follows.

  That is, as one embodiment, the center position of the wafer is calculated by the center position calculation means, and the center of the holding means and the center of the wafer that share the wafer for which the center position is calculated by the wafer grinding apparatus and the mark forming unit are The wafer is placed on the holding means by the placing means so as to match.

  As a result, laser marking and wafer outer periphery grinding can be performed in a state where the center of the wafer and the center of the holding device coincide with each other. Therefore, by performing laser marking and wafer outer periphery grinding on the basis of the center of the holding device. Since each machining can be performed with the exact same position as a reference, machining with less error is possible. Here, the center of the holding means is the rotation center of the holding means. Since the center of the wafer holding and rotating coincides with the center of the wafer, both the laser marking and the wafer outer peripheral grinding are highly accurate. Can be done.

  As another embodiment, the mark forming unit includes the center position calculating means, so that the laser marking is performed based on the wafer center (and the notch position of the wafer) calculated by the center position calculating means, and then the mounting means Then, the wafer is placed on the holding means so that the center position of the wafer calculated by the center position calculating means matches the center position of the holding means of the wafer grinding apparatus.

  Thus, since the wafer can be ground in a state where the center of the wafer and the center of the holding means (the rotation center of the holding means) coincide with each other, the wafer is ground by using the center of the holding means as a reference. This is equivalent to processing with the center as the reference. Eventually, both the laser marking and the wafer grinding can be performed with the center of the wafer as the reference, so both can be processed with high accuracy.

  The laser sensor 92 includes a laser transmission unit 92a and a laser reception unit 92b. The outer peripheral portion of the wafer 90 held and rotated by the holding and rotating means 96 is inserted between the laser transmitter 92a and the laser receiver 92b. Thereby, the laser sensor 92 measures the length of D over the entire circumferential direction of the wafer 90. Here, the holding and rotating means 96, the holding means 96a, and the rotating means 96b can be the same as the holding and rotating means 12, the holding means 12a, and the rotating means 12b shown in FIG. To do.

  The calculation unit 94 calculates radius data over the entire circumferential direction of the wafer 90 from the distance (design value + correction value) E between the center of the holding unit 96 a and the laser sensor 92 and the length D measured by the laser sensor 92. Calculate as D + E. Here, regarding the correction value, the difference between the master data and the measurement result can be used as the correction value.

  Further details will be described with reference to the drawings. 10 and 11 are plan views showing the center of the wafer, the center of the holding means, and the center of the wafer obtained by calculation. As shown in FIG. 9, the center position calculation means measures D + E over the entire circumference of the wafer 90 while rotating the wafer 90. Thereby, the arithmetic unit 94 calculates the temporary radius (D + E) of the wafer at each rotation angle (for example, each rotation angle from the notch 53 with respect to the notch 53) θ.

  However, as shown in FIG. 10A, the center α of the wafer 90 and the center β (rotation center) of the stage, which is the holding means 96a, do not necessarily coincide with each other and are shifted as shown in FIG. Eccentric. For this reason, the temporary radius (D + E) (indicated by the symbol 104) at each rotation angle calculated by the calculation unit 94 varies without being a constant value.

  Next, the calculation unit 94 obtains coordinates (X, Y) on the outer periphery of the wafer from the angle θ and the temporary radius (D + E). If the outer circumference of the wafer can be approximated by a circle, the coordinates of the center of the wafer can be calculated if the coordinates of three or more different points on the outer circumference of the wafer are known. Therefore, the arithmetic unit 94 uses the least square method to calculate the center coordinates of the wafer. The radius of the wafer is calculated.

  The center coordinate γ of the wafer calculated at this time is shifted in the direction of the notch 53 due to the influence of the notch 53 as shown in FIG. Therefore, the calculation unit 94 extracts the smallest point (indicated by symbol 106) among the distances (radius) of each angle from the wafer center coordinate γ to the outer periphery of the wafer.

Referring to (a) of FIG. 11, next, the extracted minimum radius (indicated by symbol 106) +10 μm is obtained on the left and right of the notch 53 (indicated by symbol 110). Then, the calculation unit 94 obtains the angle θ _{3 of the} notch 53 by (θ ₁ −θ ₂ ) / 2. The calculation unit 94 deletes the two obtained θ ₃ portions, that is, the range of 2θ ₃ as the notch 53, and obtains the center coordinates of the wafer again. As a result, as shown in FIG. 11B, the center coordinate γ obtained by calculation coincides with the center coordinate α of the wafer.
Note that the method of obtaining the center of the wafer is not limited to the above method, but may be obtained by any other commonly used method.

(4) Wafer Perimeter Grinding (Chamfering) Control Method Next, an example of a grinding control method of the wafer grinding apparatus according to the present invention will be described with reference to the drawings. FIG. 12 is an example of information (grinding condition information) regarding the difference in etching rate depending on the crystal orientation of the wafer. As shown in FIG. 12, the grinding condition information can be indicated by a measured value of the wafer radius after etching in a range of 360 degrees from the predetermined reference position (one round of the wafer).

  As shown in this figure, the grinding condition information is not necessarily directly related to the crystal orientation of the wafer, but if the condition for each angle of the wafer is indicated, it is eventually equivalent to the information for each crystal orientation of the wafer. become. Also, regarding the information on the difference in etching rate, the etching rate can be changed if the radius for each angle of the wafer after etching is shown as shown in FIG. 12 without directly expressing the difference in etching rate itself. It is equivalent to expressing the difference itself. Therefore, in the present invention, the information (grinding condition information) regarding the difference in the etching rate depending on the crystal orientation of the wafer can be made into a perfect circle after etching by grinding the wafer outer periphery based on the information. It shall contain all information.

  As an example, if the target radius r after etching is 225 mm, as shown in FIG. 12, r = 225.005 mm at 20 ° and 50 °, which is larger than the target radius by 5 μm. . The control means 18 (FIG. 1) performs grinding by as much as 5 μm at 20 ° and 50 ° based on the grinding condition information as shown in FIG.

  More specifically, referring to FIG. 1 and FIG. 13 (an explanatory diagram for explaining the grinding (chamfering) of a wafer with a grindstone), the control means 18 controls the cutting amount of the grindstone 14a, and the angle 20 of the wafer 1 is controlled. When the angle is 50 ° or 50 °, the control is performed so as to cut by about 5 μm.

  In addition, when the angle is 100 ° from FIG. 12, it is smaller than the target radius by about 5 μm after the etching. Therefore, the control means 18 controls based on the grinding condition information as shown in FIG. 12 so that the cutting depth of the grindstone 14a is reduced by about 5 μm when the angle is 100 °. By grinding on the basis of the grinding condition information in this way, a perfect circle wafer having a desired radius after etching can be manufactured.

<Embodiment>
Next, the prior art and embodiments of the present invention will be described. FIG. 14 is a flowchart showing a flow of conventional marking (mark formation on a wafer) and peripheral grinding (chamfering).

  As shown in FIG. 14, conventionally, by detecting the outer shape of the wafer, the center of the wafer is calculated, and the position of the notch is also detected (step S1). Next, marking is performed based on the calculated wafer center and notch position (step S2). After that, the wafer is transferred (step S3) and installed in a peripheral grinding machine, which is a separate device, and the outer shape of the wafer is detected by this device (step S4) to calculate the center of the wafer, and the calculated wafer center Peripheral grinding is performed with reference to. For this reason, since the processing is performed based on the wafer center calculated separately for marking and outer periphery grinding, the position of the reference wafer center is different, and the processing accuracy is deteriorated.

  A first embodiment and a second embodiment of the present invention will be described with reference to FIG. FIG. 15 is a flowchart showing the flow of the embodiment of the present invention. The first embodiment of the present invention is a wafer marking / grinding apparatus in which the holding means used in the marking means and the holding means used in the grinding means are the same.

  The operation in the first embodiment will be described with reference to FIG. In the first embodiment, the center position calculating unit detects the outer shape of the wafer to calculate the center position of the wafer, and also detects the notch position of the wafer (step S1). Next, the wafer is transported (step S2), and the wafer placing means places the wafer on the holding means so that the center of the wafer coincides with the center of the holding means (step S3).

  Here, as the wafer mounting means, an apparatus normally used for transporting and placing the wafer can be used. For example, the wafer is lifted and moved by an arm that vacuum-sucks the wafer surface and placed on the holding means. Can be placed. At this time, the suction arm or the holding means is moved, adjusted, and placed by the XY stage so that the center of the wafer and the center of the holding means coincide with each other.

  Next, marking is performed with reference to the center of the holding means and the notch (step S4). After the marking, the outer periphery grinding is performed with the center of the holding means (the rotation center of the holding means) as a reference while the wafer is placed on the same holding means (step S5). Thereby, since marking and outer periphery grinding are performed on the basis of the center of the same holding | maintenance means, the highly accurate process with no dispersion | variation in the relationship between a marking position and the outer periphery position after grinding can be performed.

  Next, a second embodiment of the present invention will be described with reference to FIG. 2nd Embodiment is a case where the holding means which performs marking differs from the holding means which performs outer periphery grinding. The center position calculating means detects the outer shape of the wafer to calculate the center position of the wafer, and also detects the notch position of the wafer (step S1).

  Next, marking is performed using the calculated center position of the wafer as a reference (step S2). At this time, since the center position of the wafer does not coincide with the center position of the holding means used in the marking, the center of the holding means cannot be used as a reference.

  Thereafter, the wafer is transported (step S3), and the wafer placing means places the wafer on the holding means used for the outer periphery grinding so that the center of the wafer coincides with the center of the holding means (step S4). Since the wafer mounting means is the same as that of the first embodiment, description thereof is omitted.

  Then, the wafer is ground on the basis of the center of the holding means (step S5). As described above, also in the second embodiment, the marking and the outer periphery grinding are performed based on the center position of the wafer calculated by the center position calculating means, so that the marking position and the outer periphery position after the grinding are determined. High-precision machining can be performed with no variation in the relationship.

<Appendix>
The wafer marking / grinding apparatus according to the present invention can also include the following inventions and features.

The wafer marking / grinding apparatus of the present invention comprises a holding means for holding a wafer having a notch formed therein, a rotating means for rotating the holding means, a wafer placing means for placing the wafer on the holding means, A center position calculating means for calculating the center position of the wafer from the outer periphery of the wafer; a notch detecting means for detecting the notch; and a predetermined surface of the wafer determined on the basis of the position of the notch detected by the notch detecting means. Marking means for forming a mark at a position, and grinding means for grinding the outer periphery of the wafer with reference to the center of the holding means on which the wafer is placed by the wafer placing means, The placing means places the wafer so that the center of the wafer calculated by the center position calculating means and the center of the holding means coincide with each other. Placed on the holding means, and the marking means is a center position of the wafer calculated by the center position calculating means, or a center position of the holding means on which the wafer is placed by the wafer placing means. The main feature is that a mark is formed at a predetermined position on the wafer surface as a reference.
As a result, the marking means and the grinding means end up with the same reference, that is, the wafer processing based on the center of the wafer calculated by the center position calculation means, so it is possible to perform highly accurate mark forming processing and wafer chamfering processing. become.

In the wafer marking / grinding apparatus according to the present invention, the marking means predicts an outer peripheral position after being ground by the grinding means, and the wafer is determined based on the predicted outer peripheral position and the notch position. A mark is formed at a predetermined position on the surface, and the grinding means mainly grinds the outer periphery of the wafer so that the wafer has a predetermined size and shape after the marking means forms the mark. It is a feature.
Thereby, the marking means predicts the outer peripheral position after outer peripheral grinding of the wafer, and forms a mark at a position set with reference to the predicted outer peripheral position and the position of the notch. Variation in mark positions between wafers can be suppressed.

Further, in the wafer marking / grinding apparatus according to the present invention, the marking means predicts the outer peripheral position after being ground by the grinding means with reference to the center position of the wafer obtained by the center position calculating means, A mark is formed at a predetermined position on the wafer surface determined on the basis of the predicted outer peripheral position and the position of the notch, and the grinding unit is configured to calculate the center position calculating unit after the marking unit forms the mark. The main feature is that the outer periphery of the wafer is ground so that the wafer has a predetermined size and shape on the basis of the center position of the wafer obtained by the above.
Accordingly, the outer peripheral position after grinding is predicted, and the mark is formed with reference to the predicted outer peripheral position, so that variation in the mark position with respect to the outer peripheral position after grinding can be suppressed.

Furthermore, the wafer marking / grinding apparatus of the present invention is characterized in that the marking means forms a mark inside a predetermined distance from the predicted outer peripheral position.
Thereby, a mark can be formed inside a predetermined distance from the outer periphery after chamfering without variation between wafers. On the other hand, in the prior art, it was impossible to form marks without variation between wafers at a predetermined distance from the outer periphery of the wafer after chamfering. The reason for this is that, during marking (formation of forming a mark is also referred to as marking), since the chamfering of the outer periphery of the wafer is not performed, the wafer shape is greatly deviated from a perfect circle. For this reason, even if marking is performed at this time, the peripheral position of the wafer changes due to the change in the peripheral shape of the wafer in the subsequent chamfering process. As a result, the distance from the outer periphery to the mark varies from wafer to wafer.

The notchless wafer manufacturing method of the present invention is a notchless wafer manufacturing method, a wafer holding step of holding a notched wafer by a holding means, a rotating step of rotating the holding means, Detected by the wafer placing step of placing the wafer on the holding means, a center position calculating step of calculating the center position of the wafer from the outer periphery of the wafer, a detecting step of detecting the notch, and the detecting step. A mark forming step of forming a mark at a predetermined position on the wafer surface determined with reference to the position of the notch, and the center of the holding means on which the wafer is placed by the wafer placing step. A grinding step of grinding the outer periphery of the wafer, and in the wafer placing step, the center of the wafer calculated by the center position calculating step The wafer is placed on the holding means so as to coincide with the center of the holding means, and in the mark forming step, the center position of the wafer calculated by the center position calculating means or the wafer mounting position is set. The main feature is that a mark is formed at a predetermined position on the surface of the wafer with reference to the center position of the holding means on which the wafer is placed by the placing means.
As a result, both the mark formation process and the grinding process are performed based on the same reference, that is, the center of the wafer calculated by the center position calculation process. Therefore, highly accurate mark formation and wafer chamfering can be performed. It becomes possible.

Further, in the notchless wafer manufacturing method of the present invention, in the mark forming step, the outer peripheral position after being ground by the grinding means is predicted based on the center position of the wafer obtained in the center position calculating step. Forming a mark at a predetermined position on the wafer surface determined based on the predicted outer peripheral position and the position of the notch, and in the grinding step, after the mark forming step forms the mark, the center is formed. The main feature is that the outer periphery of the wafer is ground so that the wafer has a predetermined size and shape with reference to the center position of the wafer obtained in the position calculating step.
As a result, the outer peripheral position after grinding is predicted, and the mark is formed with reference to the predicted outer peripheral position, so that variations in the position of the mark with respect to the outer peripheral position after grinding can be suppressed.

Furthermore, the notchless wafer manufacturing method of the present invention is characterized in that, in the mark forming step, a mark is formed inside a predetermined distance from the predicted outer peripheral position.
Thereby, a mark can be formed inside a predetermined distance from the outer periphery after chamfering without variation between wafers. On the other hand, in the prior art, it was impossible to form marks without variation between wafers at a predetermined distance from the outer periphery of the wafer after chamfering. The reason for this is that, during marking, since the outer periphery of the wafer is not chamfered, the wafer shape is greatly deviated from a perfect circle. For this reason, even if marking is performed at this time, the peripheral position of the wafer changes due to the change in the peripheral shape of the wafer in the subsequent chamfering process. As a result, the distance from the outer periphery to the mark varies from wafer to wafer.

DESCRIPTION OF SYMBOLS 1 ... Wafer, 10 ... Chamfering part, 12 ... Holding rotation means, 12a ... Holding means, 12b ... Rotating means, 14 ... Grinding means, 14a ... Grinding wheel, 14b ... Grinding wheel rotating means, 16 ... Moving means, 18 ... Control means, 20 ... CPU, 22 ... memory, 24 ... input means, 26 ... external storage device, 30 ... wafer, 32 ... wafer, 34 ... wafer, 40 ... wafer, 42 ... wafer, 50 ... mark forming unit, 51 ... wafer, 52 ... holding and rotating means, 52a ... holding means, 52b ... rotating means, 53 ... notch, 54 ... notch detecting means, 55 ... laser irradiation part, 56 ... mark, 57 ... light receiving part, 58 ... marking means, 60 ... center, 62 ... line segment, 66 ... straight line, 68 ... wafer outer periphery position, 70 ... outer periphery, 72 ... outer periphery after chamfering or etching, 90 ... wafer, 92 ... laser sensor, 92a ... laser transmitter, 92 ... laser receiver unit, 94 ... arithmetic unit, 96 ... holding and rotating means, 96a ... holding unit, 96b ... rotating means

Claims (2)

The center position of the wafer is obtained from the outer periphery of the wafer having a notch formed on the outer periphery, and the rotation center position of the holding means that holds and rotates the wafer coincides with the center position of the wafer to hold the wafer. and a wafer positioning means for positioning the,
And notch detection means for detecting the previous Symbol notch,
On said holding means said wafer is held, marking forming marks in a predetermined position of the wafer surface to be determined and the rotation center position of the holding means and the detected notch position by the notch detecting means as a reference Means,
Grinding means for grinding and removing the outer periphery of the wafer;
Equipped with a,
The grinding means grinds the wafer held by the holding means with reference to the rotation center position of the holding means, or the center position of the wafer is transferred from the holding means to another holding means. A wafer marking / grinding apparatus characterized in that the wafer moved so as to coincide with the rotation center position of the wafer is ground on the basis of the rotation center position of the other holding means . The center position of the wafer is obtained from the outer periphery of the wafer having a notch formed on the outer periphery, and the rotation center position of the holding means that holds and rotates the wafer coincides with the center position of the wafer to hold the wafer. and a wafer positioning step for positioning the,
A holding step of holding the wafer positioned in the wafer positioning step in said holding means,
A notch detection step for detecting the notch;
In the wafer on the holding means is held, marking forming marks in a predetermined position of the wafer surface to be determined and the rotation center position of the holding means and has been notch position detected by the notch detection step based Steps,
A grinding step for grinding and removing the outer periphery of the wafer;
Equipped with a,
In the grinding step, the wafer held by the holding means is ground with reference to the rotation center position of the holding means, or the center position of the wafer is transferred from the holding means to another holding means. A wafer marking / grinding method, characterized in that the wafer moved so as to coincide with the rotation center position is ground with reference to the rotation center position of the other holding means .

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