JP2006294855A - Method and device for back grinding semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lighten stress relief processing by improving grinding marks in back grinding. <P>SOLUTION: Stress relief processing is lightened by changing a plurality of contact conditions or/and performing grinding in parallel such that grinding marks occurring in correspondence with contact conditions of the rotating grinder and a rotating semiconductor wafer are compounded in different directions or/and in two types or more of pattern when the rear surface of the semiconductor wafer is ground with the rotating grinder and then back ground. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backgrinding method and apparatus for grinding a back surface of a semiconductor wafer to reduce the thickness.

  In recent years, with the miniaturization and high density of packages mounted on computers and mobile phones, devices in the package are also required to be miniaturized and thinned, so that semiconductor wafers having a thickness of 100 μm or less are used. A technique is known in which the opposite surface of the circuit formation surface is removed by machining to make it thin (for example, see Patent Document 1). In Patent Document 1, a surface of the wafer opposite to the circuit forming surface, that is, the back surface is ground to reduce the thickness of the wafer, and by dicing using a blade that rotates at high speed, a semiconductor solid having a predetermined thickness is obtained. A technique for obtaining a piece is disclosed.

  In a normal process, back grinding is performed on a semiconductor wafer before dicing, and the semiconductor wafer after back grinding is subjected to full-cut dicing from the surface and divided into semiconductor solid pieces. On the other hand, in the DGB process, a semiconductor wafer that has been half-cut diced from the front surface is thinned by applying backgrinding that grinds from the back surface until reaching the groove by half-cut dicing. It is divided.

  In addition, in Patent Document 1, in the dicing process by machining, it is easy to be damaged at the time of cutting, and a decrease in the processing yield is unavoidable, whereas when performing both the back grinding process and the dicing process by etching, Since thinning takes time, the microcrack layer generated by machining is first processed by plasma processing the machined surface of a semiconductor wafer that has been thinned to some extent by removing the opposite side of the circuit formation surface by machining. Discloses a technique for performing a so-called stress relief process for removing the stress.

  In addition, for plasma dicing, mask formation, plasma dicing, mask removal, and microcrack removal are each performed with a single plasma processing apparatus, reducing equipment costs, improving production efficiency, and transferring wafers. There is also known a technique for avoiding the damage caused by (see, for example, Patent Documents 2 and 3).

Furthermore, by adding stress relief processing such as dry polishing, mechanical polishing, wet etching, and dry etching to the backgrinding process, grinding damage due to grinding can be removed and the bending strength can be further improved. It has been publicized on the net that the back surface can be mirror-finished, the amount of warpage can be reduced, and the bending strength can be improved (for example, see Non-Patent Document 1).
JP 2002-93752 A JP 2004-172364 A JP 2004-172365 A URL: http: www. disco. co. jp / solution / library / streef. html

  By the way, the reason why semiconductor wafer backgrinding depends on plasma processing is that the processing time is long and it is difficult to improve productivity. Therefore, as disclosed in Non-Patent Document 1, dicing is performed by machining to provide sufficient bending strength. Is desired.

  However, electronic cards that contain a circuit board with a semiconductor chip mounted in the card case are not only small PC cards used for expanding the functions of personal computers, but also smaller and thinner, mobile phones. SD cards (for example, Patent Documents 7 and 8) used for memories such as memory-type portable music players, high-definition video cameras, and 3D game consoles are known, and miniSD cards that are smaller and thinner are also provided. The size is, for example, 21.5 mm × 20 mm × 1.4 mm (Japanese Patent Laid-Open Nos. 2003-76440 and 2004-21964). In such a background, the semiconductor chip is thinned to about 50 μm and easily breaks, and the finish processed as described in Non-Patent Document 1 still has insufficient strength. For this reason, it is necessary to perform the stress relief process more sufficiently, and the processing time tends to be longer.

  Therefore, the present inventor has disclosed the semiconductor wafer in such a manner that arc-shaped grinding marks extending radially from the central portion to the periphery are shown on the semiconductor wafer illustrated in accordance with the explanation of the stress relief operation in Non-Patent Document 1. Paying attention to the fact that long grinding marks that are relatively deep and clear and have the same orientation remain on the backgrinding surface, various experiments were conducted and studies were repeated. As a result, it is known that stress tends to concentrate on such grinding traces and cause damage, and it is necessary to satisfy the removal amount enough to erase such grinding traces for sufficient stress relief processing. It has been found that this is one of the causes of the long processing time.

  The object of the present invention is to provide a semiconductor wafer back grinding method and apparatus capable of improving the grinding marks during back grinding and increasing the strength of the semiconductor wafer after back grinding based on such new knowledge. It is to provide.

In order to achieve the above object, the semiconductor wafer backgrinding method of the present invention is a semiconductor wafer backgrinding method in which the back surface of the semiconductor wafer is ground by a rotating grinding tool,
Change the contact condition into multiple or parallel so that two or more kinds of grinding traces generated in accordance with the contact condition between the rotating grinding tool and the rotating semiconductor wafer during grinding It is characterized by grinding.

  In such a configuration, a rotating grinder is brought into contact with the back surface of the rotating semiconductor wafer to grind the back surface of the semiconductor wafer. By utilizing the relationship that enables the grinding tool to change the contact condition of the grinding tool to the backside of the semiconductor wafer, or to combine and grind the grinding marks so that two or more different orientations and patterns are combined. It is possible to eliminate the fact that the grinding traces that can be originally formed into long streaks overlap and divide in various places depending on the direction and pattern, and the grinding roots are elongated independently. .

  For this purpose, as one method, a grinding mark that contacts one side of a rotating semiconductor wafer with a rotating grinding tool and extends in the same direction with respect to the rotation direction of the semiconductor wafer in an arc shape extending from the center of the semiconductor wafer to the outer periphery. Of the semiconductor wafer by performing two types of grinding at the same time or in parallel, that is, grinding for changing the contact condition for generating a grinding mark that reverses the direction of rotation of the semiconductor wafer relative to the rotation direction of the semiconductor wafer. It is only necessary to combine two types of grinding marks whose directions are reversed with respect to the rotation direction, and processing under conventional contact conditions is performed only at different times or in parallel so that the direction of the grinding marks is reversed. A pattern is obtained in which arc-shaped grinding marks whose directions are opposite to each other are overlapped at many places and divided into a fine mesh.

  Such two kinds of grinding at different times can be performed by shifting the contact position of one grinder to the semiconductor wafer from one side of the semiconductor wafer to the other side.

  In addition, two parallel grinding operations are performed by bringing two grinding tools into contact with each other at different positions on the semiconductor wafer so as to form arc-shaped grinding marks whose directions are reversed with respect to the rotation direction of the semiconductor wafer. Can do.

  Grinding by contacting multiple grinding tools with different orientations and patterns at the same time or at different times to grind the grinding tool in contact with the semiconductor wafer to form grinding traces with different orientations and patterns. In the further configuration formed by the above, it is easy to obtain a finer pattern in which a number of types of grinding marks are combined.

  In order to achieve the method as described above, several apparatuses are suitable as follows.

  As one of them, a grinding station for holding and rotating a semiconductor wafer on the front surface side for grinding processing on the back surface side, and a rotating grinding tool on the back surface of the semiconductor wafer rotated at this grinding processing station are brought into contact with each other. A semiconductor wafer backgrinding apparatus comprising a grinding means for grinding and backgrinding, and grinding marks generated in accordance with contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding are: There is provided a semiconductor wafer back grinding apparatus comprising control means for changing a contact condition between a semiconductor wafer and a grinding tool into a plurality so that two or more different orientations or patterns are combined.

  In addition, as another device, a grinding wafer station that holds and rotates a semiconductor wafer on the front surface side for use in grinding on the back surface, and a grinding tool that rotates on the back surface of the semiconductor wafer that is rotated at this grinding processing station are contacted. A semiconductor wafer backgrinding apparatus comprising a grinding means for grinding and backgrinding, and grinding marks generated in accordance with contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding However, in order to combine two or more different orientations or patterns, a pair of grinding stations and grinding means having different contact conditions between the semiconductor wafer and the grinding tool are sequentially subjected to back grinding for the same semiconductor wafer. There is a semiconductor wafer backgrinding device characterized in that it is prepared to perform.

  In addition, as another apparatus, a grinding station that holds and rotates a semiconductor wafer on the front side for grinding on the back side, and a grinding tool that rotates on the back side of the semiconductor wafer that is rotated in this grinding station are contacted. A semiconductor wafer backgrinding apparatus comprising a grinding means for grinding and backgrinding, and grinding marks generated in accordance with contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding However, in order to combine two or more different orientations or patterns, a single grinding station is combined so that multiple grinding tools having different contact conditions with respect to the semiconductor wafer in this grinding station can be operated at different times or in parallel. There is a semiconductor wafer backgrinding device characterized in that.

  According to the semiconductor wafer backgrinding processing method and apparatus of the present invention, grinding is performed while leaving fine grinding marks that are overlapped and divided in a plurality of directions or patterns, and as in the case of grinding marks that extend independently. Since stress is not concentrated on the semiconductor wafer, the strength of the semiconductor wafer is improved, the stress relief process is reduced, and the productivity can be increased without a decrease in strength. Moreover, according to the said apparatus, such a method can be achieved automatically and stably according to a program.

  A semiconductor wafer backgrinding processing method and apparatus according to an embodiment of the present invention will be described below with reference to the drawings for understanding of the present invention. However, the following description is a specific example of the present invention and does not limit the scope of the claims.

  In the present embodiment, as shown in FIG. 1, the semiconductor wafer 4 in which the grooves 1 are formed vertically and horizontally by the half-cut dicing from the surface 3 along the dicing line on the back grind dig protective sheet 9, or not shown in the figure. For a semiconductor wafer that is not to be processed, back grinding is performed by applying a grinder 7 as a grinding tool to the back surface 2 side of the semiconductor wafer and grinding to reduce the thickness. As a result, the half-cut dicing can be divided into semiconductor solid pieces simultaneously with thinning. Moreover, in the case of non-dicing, it is divided into semiconductor solid pieces by full-cut dicing after thinning by back grinding. For such back grinding, a grinding device 8 as shown in FIG. 5 is used. As shown in FIG. 1, the grinding apparatus 8 carries out a back grinding process by unloading the semiconductor wafer 4 having the back grinding protective sheet 9 bonded to the surface 3 from the cassette 41 by the loading / unloading mechanism 43. The subsequent semiconductor wafer 4 is stored in the cassette 42. The backgrinding process is performed in a state of being adsorbed on the four chuck tables 47 to 50 provided on the turntable 51.

  The four chuck tables 47 to 50 are installed at equal intervals in the circumferential direction of the turntable 51, set around the turntable 51, the wafer receiving position facing the cassette 41, and the rough grinding facing the grinder 61 for rough grinding. A semiconductor wafer that is intermittently rotated one step at a time to a grinding position, a finish grinding position that faces the grinder 7 for finish grinding, and a wafer take-out position that faces the cassette 42, and is centered while stopping at each position. 4 is received, and rough grinding, finish grinding, and take-out are sequentially performed, and this is repeated.

  Therefore, at the wafer receiving position, the semiconductor wafer 4 taken out from the cassette 41 onto the centering table 44 by the carry-in / out mechanism 43 and centered is sequentially stopped at the wafer receiving position by the transport mechanism 45. It is conveyed to ˜50 and is supported by suction. Further, at the wafer take-out position, the polished semiconductor wafer 4 on the chuck tables 47 to 50 that sequentially stop there is transferred to the cleaning unit 54 by the transfer mechanism 46 for cleaning, and the polishing cleaned by the cleaning unit 54 is performed. The finished semiconductor wafer 4 is stored in the cassette 42 by the carry-in / out mechanism 43.

  Further, in the rough grinding position, the grinder 61 for rough grinding is supported by the lower end of the spindle 59 of the rough grinding mechanism 52 via the mounter 60 and is rotationally driven, and is sucked and supported by the chuck tables 47 to 50 and rotated. The surface 2 is slidably contacted from above to perform rough grinding. Further, at the finish grinding position, the finish grinding grinder 7 is rotationally driven and supported by the lower end of the spindle 66 of the finish grinding mechanism 53 via the mounter 67, and after rough grinding which is sucked and supported by the chuck tables 47 to 50. The grinding processing station 101 is configured to perform finish grinding by sliding contact with the back surface 2 of the semiconductor wafer 4 from above, and the back grinding process is started at the rough grinding position and applied to the semiconductor wafer 4 at the finish grinding position. Finish the backgrinding process.

  The semiconductor wafer 4 after finish grinding stored in the cassette 42 is transported to the plasma etching device 16 by the transport device 70 with the back grinding protective sheet 9 attached, and plasma etching from the back surface 2 side is performed. A stress relief process for removing the processing strain layer is performed by the process.

  However, when the semiconductor wafer before dicing is the target, the stress relief process is performed after full-cut dicing. The series of backgrinding operations as described above are automatically and stably performed according to the program including the control means 100 alone provided in the grinding apparatus 8 shown in FIG. 5 or the cooperation with the control means of another apparatus. Done.

  Here, each of the grinder 61 for rough grinding and the grinder 7 for finish grinding is applied to one side portion of the back surface 2 of the semiconductor wafer 4 rotating in the direction indicated by the arrow A as shown in FIGS. As shown in FIG. 1 with respect to the back surface of the semiconductor wafer 4 to be brought into contact while rotating in the direction indicated by the arrow B, and for the purpose of discharging grinding scraps and preventing overload due to wide area contact. Grinding is performed with a slight edge contact from the periphery on one side radial line of the semiconductor wafer 4 to a position slightly beyond the central portion. For example, as shown in FIG. 1, the direction of inclination at this time is brought into contact with a clearance angle that is inclined forward or backward with respect to the rotation direction A of the semiconductor wafer 4.

  In order to reduce the time required for backgrinding, rough grinding is performed with a coarse grindstone and a large depth of cut, while finish grinding is performed with a fine grindstone and a small depth of cut. Since the surface roughness is finely finished to a predetermined range, there is no grinding mark at the time of rough grinding, or even if it remains, it is of the finish grinding level. However, rough grinding is not particularly essential. In any case, a grinding mark 71 as shown in FIG. 2 remains on the back surface 2 of the semiconductor wafer 4 after the conventional back grinding process as described above. It takes time to increase the amount of removal by stress relief until this is erased.

  Therefore, in the present embodiment, particularly, the finish grinding in the back grinding process is performed as follows. Contact conditions such that two or more kinds of grinding marks 71 generated in correspondence with the contact conditions between the grinder 7 which is a rotating grinding tool at the time of grinding and the back surface 2 of the rotating semiconductor wafer 4 are combined in different directions and patterns. Is changed into a plurality of or combined and ground. Such change and combination of contact conditions can be implemented in various ways. In this way, when the rotating finish grinding grinder 61 is brought into contact with the back surface 2 of the rotating semiconductor wafer 4 for grinding, the back surface 2 has an orientation and a pattern according to the contact conditions at the time of grinding in FIG. By utilizing the relationship that the grinding marks 71 and the like as illustrated can be made, the contact conditions of the grinder 7 with respect to the back surface 2 of the semiconductor wafer 4 can be changed into a plurality or combined and ground, as shown in FIG. As shown in FIG. 3, the grinding marks 71 are generated so that two or more different orientations and / or different patterns are combined such that the directions of the grinding marks 71 are reversed with each other in the rotation direction A of the semiconductor wafer 4 as shown in FIG. It is done. Accordingly, the grinding traces 71 that can be originally formed in a streak shape are overlapped and divided at various places depending on the direction and pattern, and the grinding traces 71 are elongated independently as shown in FIG. Can be resolved. As a result, stress does not concentrate as in the case of the grinding mark 71 as shown in FIG. Therefore, it is possible to reduce the stress relief process and increase the productivity without reducing the strength.

  For example, in the example shown in FIG. 3, an arc shape extending from the center of the semiconductor wafer 4 to the outer periphery by bringing the grinder 7 rotating in the B direction into contact with one side radius of the semiconductor wafer 4 rotating in the A direction as indicated by a virtual line. Grinding that causes the grinding traces 71 to be generated in the same direction, and grinding that is changed to a contact condition in which the direction of the grinding traces 71 is in contact with the other one side radius indicated by a solid line that is reversed with respect to the rotation direction A of the semiconductor wafer 4. And the grinding mechanism moving table 102 shown in FIG. 5 or the movement of the finish grinding mechanism 53 alone is used, for example, with the shift of the distance S in the diameter line direction of the grinder 7. Or a combination of the chuck table and the grinder 7 at two separate positions. As a result, the processing under the conventional contact conditions is reversed at the same time or in parallel so that the direction of the grinding mark 71 is reversed with respect to the rotation direction A of the semiconductor wafer 4. The arc-shaped grinding marks 71 are overlapped at many places to obtain a pattern that is divided into a fine mesh as shown in FIG.

  On the other hand, in the example shown in FIG. 4, the two grinding operations are performed in parallel by two grinders 7 on one chuck table with two finish grinding mechanisms 53 provided side by side. Also by this, a fine mesh pattern of grinding marks 71 as shown in FIG. 3 is obtained.

  Further, in the example shown in FIGS. 3 and 4, a planetary motion mechanism is adopted in which the rotation center of the semiconductor wafer 4 or the grinder 7 in the A and B directions is rotated in the C and D directions. Polishing can be performed while combining the operations, or polishing can be performed while combining the reciprocating movement in the diameter line direction E. In such a combined operation, the formation position of the grinding mark 71 is continuously displaced in the combined operation direction. As a result, the composite state of the grinding traces 71 whose directions are reversed with respect to each other is obtained in a complicated manner, and a composite pattern with a finer and more even distribution can be obtained. The strength is further increased, and the stress relief process is further increased as the strength is increased. It can be reduced and the time is shortened. Further, as the rotational speed of the finish grinding grinder 61 with respect to the rotational speed of the semiconductor wafer 4 is increased, the pitch of the grinding marks 71 becomes finer, which is suitable for increasing the strength. Further, contact conditions according to various relative movement conditions including changes in the rotation direction of the semiconductor wafer 4 and the grinder 7 other than these and the positional relationship of the rotation centers, that is, on the same axis or in which direction the deflection is made. You can also use the difference.

  In short, a plurality of grinding tools such as a grinder 7 that performs grinding by contacting with the semiconductor wafer 4 so as to form grinding traces 71 of different orientations and patterns are provided in contact with each other for grinding or rough grinding mechanism 52. And the finish grinding mechanism 53 are contacted at different times and ground to form a plurality of grinding marks 71 having different orientations and patterns, thereby forming a number of types of grinding marks 71. A composite pattern can be obtained, and as the number of types increases, it becomes easier to obtain a grinding trace 71 having a finer pattern and a more uniform pattern, and the strength can be further increased to further reduce the stress relief process.

  In addition, in order to perform a plurality of grindings for forming the grinding marks 71 having different directions and patterns at different times, in order to make the depths of the grinding marks 71 formed by them uniform, it is substantially the same in the final stage of finishing. It is necessary to take into consideration such as grinding sequentially in time. However, it can also be performed sequentially throughout the entire process of finish grinding. However, when grinding is performed in parallel, these considerations are unnecessary, and only one finish grinding position is sufficient.

  The backgrinding processing method and apparatus of the present invention can be practically used for thinning a semiconductor wafer, and can cope with a decrease in strength due to grinding marks.

It is sectional drawing which shows one process state which grind | polishes on the one side radial line of the semiconductor wafer with the back grinding process method which concerns on embodiment of this invention. It is a top view which shows the processing state of FIG. FIG. 2 is a plan view showing one processing state in which polishing is performed by shifting the processing position from one processing state of FIG. 1 to the other one-side radial line of the semiconductor wafer. FIG. 4 is a plan view showing a machining state in which one machining state in FIGS. 1 and 2 and one machining state in FIG. 3 are simultaneously performed. It is a perspective view of the grinding device used for the back grinding process of this Embodiment.

Explanation of symbols

2 Back surface 3 Front surface 4 Semiconductor wafer 7 Grinder 100 Control means 101 Grinding station 102 Grinding mechanism moving table

Claims (8)

A semiconductor wafer backgrinding method for grinding a backside of a semiconductor wafer with a rotating grinding tool,
Change the contact condition into multiple or parallel so that two or more types of grinding traces generated in response to the contact condition between the rotating grinding tool and the rotating semiconductor wafer during grinding A method for backgrinding a semiconductor wafer, characterized in that grinding is performed. Grinding that generates a grinding trace that contacts the one side of the rotating semiconductor wafer with the rotating grinding tool and extends in the same direction with respect to the rotation direction of the semiconductor wafer in an arc shape extending from the center of the semiconductor wafer to the outer periphery, Two types of grinding are performed at the same time or in parallel, and the grinding is performed by changing the contact conditions so as to be reversed with respect to the rotation direction of the semiconductor wafer. 2. The method of backgrinding a semiconductor wafer according to claim 1, wherein grinding marks are combined. 3. The semiconductor wafer back grinding process according to claim 2, wherein the two types of grinding are performed at different times by shifting the position of contact of one grinder to the semiconductor wafer from one side of the semiconductor wafer to the other side. Method. The two kinds of grinding are performed simultaneously by bringing two grinding tools into contact with each other at different positions on the semiconductor wafer so as to form arc-shaped grinding marks whose directions are reversed with respect to the rotation direction of the semiconductor wafer. 3. A method for backgrinding a semiconductor wafer according to 2. Grinding by contacting multiple grinding tools with different orientations or patterns by contacting multiple grinding tools simultaneously or at the same time to form grinding traces with different orientations or patterns on a semiconductor wafer. A semiconductor wafer backgrinding method. Back grinding by grinding and grinding a grinding station that holds and rotates the semiconductor wafer on the front side for grinding on the back side and a grinding tool that rotates on the back side of the semiconductor wafer that is rotated at this grinding station A semiconductor wafer backgrinding processing apparatus comprising a grinding means for processing,
Multiple contact conditions between the semiconductor wafer and the grinding tool are used so that two or more types of grinding traces corresponding to the contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding are combined in two or more different directions or patterns. A backgrinding apparatus for semiconductor wafer, characterized by comprising a control means for changing to a semiconductor device. Back grinding by grinding and grinding a grinding station that holds and rotates the semiconductor wafer on the front side for grinding on the back side and a grinding tool that rotates on the back side of the semiconductor wafer that is rotated at this grinding station A semiconductor wafer backgrinding processing apparatus comprising a grinding means for processing,
The contact conditions between the semiconductor wafer and the grinding tool are different so that two or more kinds of grinding traces corresponding to the contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding are combined in different directions or patterns. A semiconductor wafer back grinding apparatus comprising a set of a grinding processing station and a grinding means so as to sequentially perform back grinding on the same semiconductor wafer. Back grinding by grinding and grinding a grinding station that holds and rotates the semiconductor wafer on the front side for grinding on the back side and a grinding tool that rotates on the back side of the semiconductor wafer that is rotated at this grinding station A semiconductor wafer backgrinding processing apparatus comprising a grinding means for processing,
This grinding station is arranged in one grinding station so that two or more kinds of grinding traces generated in accordance with the contact conditions between the rotating grinding tool and the rotating semiconductor wafer during grinding are combined in two or more different directions or patterns. A semiconductor wafer backgrinding apparatus comprising a plurality of grinding tools having different contact conditions with respect to the semiconductor wafer in combination so as to work at different times or in parallel.

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