JP4564393B2 - Finishing method of semiconductor solid piece - Google Patents

Description

  The present invention relates to a semiconductor solid piece finishing method, and more particularly to a semiconductor solid piece finishing method for a semiconductor solid piece group on a protective sheet divided along a dicing line.

  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). Patent Document 1 discloses a method of polishing a semiconductor solid having a predetermined thickness by polishing a surface opposite to the circuit forming surface of a wafer, that is, a back grinding process for reducing the thickness of the wafer and a dicing process using a blade that rotates at high speed. A technique for obtaining a piece is disclosed.

  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 so-called stress relief.

  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, such as dry polishing, mechanical polishing, wet etching, and dry etching, to the backgrinding process, grinding damage due to grinding is removed, and the bending strength can be further improved. It has been announced 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). In addition, the amount of dry polishing removed and the bending strength (ball resistance) In other words, it is disclosed that 2 μm removal is recommended.
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 dicing 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, it is desirable to obtain sufficient bending strength by performing dicing by machining. It is. 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.

  Therefore, the present inventor has found that the MAX value of the bending strength increases as the removal amount increases to 2 μm with respect to the relationship between the dry polishing removal amount and the bending strength disclosed in Non-Patent Document 1. It was noted that the MIN value hardly increased. This indicates that there is a limit in the conventional stress relief operation and there is a cause that has not been removed yet. Regarding the relationship between the removal amount and the bending strength disclosed in Non-Patent Document 1, when the removal amount exceeds 2 μm, the MAX value of the bending strength slightly decreases, but the predetermined thickness obtained by dicing and back grinding is used. When the change in the MIN value of the bending strength was observed while increasing the amount of removal by plasma etching from the back surface side to about 6 μm per semiconductor solid group, the MIN value of the bending strength increased.

  As a result of repeated examinations in various respects, the plasma treatment performed from the back side of the semiconductor solid piece group reaches the side of each semiconductor solid piece, that is, the surface where mechanical dicing was performed. , Knowing that the damage that seems to have occurred deeper than the back-grinded back surface, that is, microcracks and processing distortions, has been removed, and the resistance exceeds the removal amount of 2 μm disclosed in Non-Patent Document 1. It seems that the decrease in the bending strength is caused by excessive thinning of the wafer and others.

  An object of the present invention is to provide a finishing method that can increase the strength of a semiconductor solid piece that has been diced by machining based on the above-described new knowledge.

In order to achieve the above object, the semiconductor solid piece finishing method of the present invention is directed to a semiconductor solid piece group on a protective sheet divided along a dicing line, and the dicing side surfaces thereof are processed. At least the machined surface including the damaged area is removed by etching. The machined surface is a dicing side surface of the semiconductor solid piece and a back surface subjected to the grinding process, and the machined surface is etched by the dicing process. The main feature is that the removal amount is larger than the removal amount obtained by etching the machined surface by grinding from the back surface .

  In such a configuration, the etching process is performed on the machined surface of the semiconductor solid piece group on the protective sheet, and as a result of dicing machining with high productivity, damage areas such as microcracks and processing distortion are deeply formed on the side surface. However, since the etching process is performed so as to remove the damaged area of the machined surface including at least the side surface, as in the conventional case in which only stress relief for back grinding is taken into consideration, the large and deep generated on the side surface due to dicing machining. No damage area remains.

Also, the machined surface is, because it is a dicing processed side and grinding processed back surface of the semiconductor solid piece, the etching process is carried out that both simultaneously, for damage zone removal aspect, the removal of the back The required amount may be exceeded, and it is only necessary to prevent excessive thinning.

Furthermore, since the etching process sets the interval between the semiconductor solid pieces to be larger than usual, even if it is performed by randomly irradiating plasma from the back side of the semiconductor solid piece group, it is a machined surface formed into a groove shape by dicing. Etching to the side surface is easy to reach, and the etching process there can be promoted, and the overall etching rate is reduced.

  However, the removal amount by plasma treatment of the machined surface by dicing can be made larger than the removal amount by plasma treatment of the machined surface by grinding from the back surface to further reduce the etching rate.

  For this purpose, the etching process may be performed by increasing the plasma irradiation rate between the semiconductor solid pieces from the back side of the semiconductor solid group to the semiconductor solid pieces rather than the back side of the semiconductor solid pieces. Plasma treatment that increases the amount of removal on the machined surface by dicing without increasing the amount of removal on the machined surface by grinding by increasing the concentration on the machined surface by dicing Are achieved simultaneously.

  The removal amount by plasma treatment of the machined surface by dicing is preferably 4 μm or more, and the removal amount by plasma treatment of the machined surface by grinding is preferably 1 to 2.5 μm.

  By adopting highly productive machining for dicing, there is no damage area due to this, and a solid semiconductor piece with higher strength than before can be obtained.

  A method for finishing a semiconductor solid piece 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.

  The present embodiment is directed to a group of semiconductor solid pieces 90 on a backgrinding protective sheet 89 as shown in FIG. 4A divided along dicing lines, and includes at least dicing side surfaces thereof. Damage areas h1 and h2 as shown in FIG. 4B are removed from the processed surfaces 90a and 90b by etching using an etching apparatus 86 as shown in FIG. 4A. Such a semiconductor solid piece 90 is formed by dividing the semiconductor wafer 4 as shown in FIG. 1 by performing a dicing process as shown in FIG. 2 and a grinding process as shown in FIG.

  As shown in FIG. 1, semiconductor circuits 18 arranged in a substantially matrix form are formed on the surface 3 of the semiconductor wafer 4, and substantially lattice-shaped dicing lines 17 are set so as to partition the semiconductor circuits 18. ing. At the time of dicing, a dicing protection sheet 23 as shown in FIG. 2 is attached to the back surface 2 of the semiconductor wafer 4, and the semiconductor wafer 4 is sucked and held by the suction holding surface 27 of the chuck table 9 on the dicing protection sheet 23 side. In this state, while the dicing line 17 and the disk-shaped blade 10 are sequentially aligned based on the detection of the dicing line 17, the formation of the groove 1 from the surface 3 side by the disk-shaped blade 10 rotating at high speed is laterally performed. Repeat the direction and the vertical direction to finish the vertical and horizontal dicing. At this time, the cutting depth is controlled so that the groove 1 does not reach the back surface 2 and is deeper than the thickness of the semiconductor solid piece 90 after the division. This is so-called half-cut dicing.

  Next, the dicing protection sheet 23 is peeled off from the back surface 2 and a back grinding protection sheet 89 is attached to the front surface 3 as shown in FIG. 3, and the semiconductor wafer 4 is attached to the back grinding chuck 96 on the back grinding protection sheet 89 side. Then, the back surface 2 is ground by the grinder 97 to expose the groove 1 and is divided into individual semiconductor solid pieces 90 having a predetermined thickness. This is so-called back grinding, and as a result, the semiconductor solid 90 group to be finished in the present embodiment is formed on the back grind protective sheet 89 with the machined surfaces 90a and 90b on the side and back surfaces. Is done.

  An example of the case where the etching process in the etching apparatus 86 for finishing the semiconductor solid 90 group is plasma etching will be described. On the lower electrode 84 provided in the chamber 82 shown in FIG. Then, the semiconductor solid 90 group is transferred together with the backgrinding protective sheet 89 to start the processing. Specifically, first, the chamber 82 is closed and evacuated to a predetermined pressure. When the pressure reaches the predetermined pressure, a predetermined amount of fluorine-based gas such as fluorine sulfide gas is introduced. Next, plasma 76 is generated by applying a voltage between the upper electrode 85 and the lower electrode 84, and the machined surfaces 90a and 90b exposed to the plasma atmosphere of each semiconductor solid piece 90 are etched by plasma irradiation. The damage areas h1 and h2 are removed. However, the etching process is not limited to the plasma process, and can be performed by other etching techniques such as chemical etching and wet etching.

  Thus, the plasma processing is performed on the machined surfaces 90a and 90b of the semiconductor solid piece 90 group on the backgrinding protective sheet 89, so that the machined surface 90a is obtained by performing machining with high productivity. Even if the damage area h1 such as microcrack or processing distortion is deeply formed on the side surface, the plasma etching process is performed so as to remove the damaged areas h1 and h2 on the machined surfaces 90a and 90b including at least the side surface as described above. Thus, unlike the conventional case in which only stress relief for back grinding is considered, a deep and large damage area h1 due to machining of dicing does not remain on the side surface. Therefore, a highly productive machining process is employed for dicing, and there is no damage area h1 due to this, and a solid semiconductor piece 90 having higher strength than the conventional one can be obtained.

  As described above, the machined surfaces 90a and 90b are the dicing side surface and the grinded back surface of the semiconductor solid piece 90, and due to the difference in the type of machining, the damage area h1, Although there is a difference in h2, specifically, where h1> h2, both plasma treatments are performed at the same time, but in order to remove the damage area h1 on the side surface, the removal amount of the damage area h2 on the back surface is The required amount may be exceeded, and it is only necessary to prevent excessive thinning. However, the overall etching rate is increased.

  Therefore, if the plasma treatment is performed by randomly irradiating the plasma 76 from the back surface 2 side of the semiconductor solid 90 group, the plasma can easily reach the side surface which is the machined surface 90a formed with the groove 1 by dicing. The plasma treatment can be promoted. For this purpose, as shown by phantom lines in FIG. 4, plasma may be generated by performing gas injection from nozzles 101 whose injection ports are randomly directed, or appropriate plasma disturbing means may be provided. Alternatively, or in addition to this, plasma treatment of the machined surface 90a can be promoted even if the intervals between the semiconductor solid pieces 90 to be finished, that is, the dicing width and the width of the groove 1 are made larger than usual. Further, the back grinding protective sheet 89 may be expanded without changing the dicing width. As a result, the overall etching rate can be reduced. Further, each divided unit portion by dicing of the semiconductor wafer 4 can be thinned every other unit as shown by phantom lines in FIG. 5 to particularly increase the interval between the semiconductor solid pieces 90, and the plasma on the machined surface 90a. It is suitable for facilitating the treatment and reducing the etching rate. In this case, the semiconductor solid piece 90 tends to be trapezoidal as shown by the broken line in FIG. 5 as a result of promoting the processing of the machined surface 90a even in the plasma processing. It can be used effectively. However, the semiconductor circuit 18 is not formed in the division unit portion to be thinned.

  However, in accordance with the relationship of h1> h2, the removal amount by plasma processing of the machining surface 90a by dicing should be larger than the removal amount by plasma processing of the machining surface 90b by grinding processing from the back surface 2. Thus, the etching rate can be further reduced. For this purpose, the plasma treatment may be performed with the irradiation rate from the back surface 2 side of the semiconductor solid piece 90 group between the semiconductor solid pieces 90 higher than the back surface 2 of the semiconductor solid piece 90, as shown in FIG. Plasma is generated while gas is preferentially flowing out along the grooves 1 between the semiconductor solid pieces 90 through nozzles and jet nozzles by a mesh-like shower tube 102 or the like substantially along the dicing grooves 1 as shown in FIG. As shown in FIG. 7, the lower electrode 84 has a mesh shape substantially corresponding to the dicing groove 1, or both the upper electrode 85 and the lower electrode 84 have a mesh shape substantially corresponding to the dicing groove 1 as shown in FIG. Plasma treatment is performed by preferentially irradiating plasma between the solid pieces 90, and the concentration of plasma on the machined surface 90a by dicing is more concentrated than the machined surface 90b by grinding. By increasing only the required ratio, the plasma processing that achieves a sufficient removal amount on the machined surface 90a by dicing without simultaneously increasing the removal amount on the machined surface 90b by grinding is achieved simultaneously. Can do.

  According to the inventor's experiment, a semiconductor wafer having a thickness of 625 μm is diced to a depth of 70 μm to form a semiconductor solid piece 90 having a thickness of 50 μm on the machined surfaces 90a and 90b from the back surface 2 side. As shown in FIG. 8, when the removal amount of the machined surface 90a, which is the side surface of the semiconductor solid piece 90, exceeds 3.5 μm, the MIN value of the strength of the semiconductor solid piece 90 increases. It is suitable as 4 micrometers or more. However, about 1 to 2.5 μm is sufficient for removing the damaged area h2 in the back grinding process. Of course, when backgrinding is performed by etching, such consideration for the back surface 2 of the semiconductor solid piece 90 is unnecessary, and the etching for the back surface 2 can be omitted. In order to etch only the side surfaces, it is necessary to take care not to reach the back surface of the semiconductor solid piece 90 and less than the required thickness. In addition, when the backgrinding is performed to some extent and then the etching process is performed to finish the division, it is necessary to consider that the damage area h2 does not remain and the thickness does not fall below a predetermined thickness.

1 is a plan view of a semiconductor wafer used in an embodiment of the present invention. It is sectional drawing which shows the state which performs the mechanical dicing process on the semiconductor wafer of FIG. It is sectional drawing which shows the state which performs a back grinding process after the dicing process of FIG. It is sectional drawing of the etching apparatus which shows the state which performs a plasma etching process after the dicing process of FIG. 3, and explanatory drawing of a semiconductor solid piece. It is principal part sectional drawing of the etching apparatus which shows another example of a plasma etching process. It is principal part sectional drawing of the etching apparatus which shows the other example of a plasma etching process. It is principal part sectional drawing of the etching apparatus which shows another example of a plasma etching process. It is a graph which shows the experimental result about the relationship between the removal amount by etching, and bending strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Groove 2 Back surface 3 Front surface 4 Semiconductor wafer 7 Grinder 10 Disc type blade 14 Lower electrode 15 Upper electrode 17 Dicing line 90 Semiconductor solid piece 90a, 90b Machined surface 76 Plasma 86 Etching device 89 Back grinding protective sheet 101 Nozzle 102 Shower tube

Claims (4)

Intended for semiconductor solid piece group on the protective sheet which has been divided along dicing lines, the damage zone of the back of working the semiconductor solid piece group dicing the side and grinding of when removed by an etching process, the dicing A method for finishing a semiconductor solid piece , wherein a removal amount by side surface etching processing is larger than a removal amount by back surface etching processing by grinding from the back surface . 2. The method for finishing a semiconductor solid piece according to claim 1, wherein a removal amount by side surface etching processing by the dicing processing is 4 μm or more . The semiconductor solid piece finishing method according to claim 2 , wherein a removal amount of the back surface by the grinding process is 1 to 2.5 μm . The semiconductor solid piece according to any one of claims 1 and 2 , wherein the etching treatment is performed by increasing a plasma irradiation rate between the semiconductor solid pieces from the back side of the semiconductor solid piece group to the semiconductor solid pieces rather than the back side of the semiconductor solid pieces. Finishing method.

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