JP3625376B2 - Wafer grinding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer grinding method and apparatus used in a wafer grinding process, particularly in a semiconductor manufacturing process.
[0002]
[Prior art]
FIG. 8 is a conceptual diagram illustrating conventional grinding of a wafer. Conventionally, the main surface of the semiconductor wafer 1 is covered with a protective tape 2 so as not to be damaged after the circuit elements and the like are formed on the main surface. Thereafter, the back surface of the wafer 1 is ground while being held by a wafer holding mechanism (not shown), so that the thickness becomes the minimum necessary.
[0003]
This backside grinding of the wafer 1 is important for improving the switching characteristics of the transistor elements. Recently, since it is used for a memory for a card or the like, a grinding process for the back surface of the wafer may be required only for the purpose of thinning. As described above, the required thickness of the wafer (thickness necessary for making the product) varies depending on the product.
[0004]
Before the back surface of the wafer 1 is ground, the wafer 1 has a back surface and an end surface, such as a dotted line 101, for example. That is, in order to prevent the end surface of the wafer 1, that is, the peripheral portion (edge) from being chipped or broken during conveyance, the end surface around the wafer is generally rounded.
[0005]
However, as shown in the enlarged view of FIG. 9, when the back surface 101 of the wafer 1 is ground as shown by the arrow, the end surface 102 around the wafer is partly cut and a rounded portion 103 is generated. To do. As a result, it becomes a cause of increasing the chipping and cracking of the peripheral portion of the wafer during subsequent wafer transport. In particular, if the rounded portion 103 is acute and touches at the time of conveyance, there is a problem of causing a decrease in product yield.
[0006]
[Problems to be solved by the invention]
In this way, conventionally, after the process of grinding the back surface of the semiconductor wafer, the end surface around the wafer is partially cut to generate a rounded portion, and the peripheral edge of the wafer is chipped, cracked, and eventually into the wafer. This increases the possibility of causing cracks and reduces the product yield.
[0007]
The present invention takes the above-mentioned circumstances into consideration, and the problem is that a method for grinding a wafer in which rounding is surely made in a continuous portion of the ground portion and the peripheral portion of the wafer according to grinding of the back surface of the semiconductor wafer. And providing an apparatus.
[0008]
[Means for Solving the Problems]
The method for grinding a wafer according to the present invention includes a step of protecting a main surface of a semiconductor wafer on which circuit elements are formed so as to realize a predetermined function, and the semiconductor wafer is supported on the main surface side and exposed on the back surface and the end surface. a step of, the end face of the semiconductor wafer such that the semiconductor wafer has a rounded end surface portion of the semiconductor wafer in response to the request thickness simultaneously grinding the entire back surface of the semiconductor wafer until any required thickness characterized by comprising the step of grinding.
[0011]
The wafer grinding apparatus according to the present invention also includes a first grinding surface that moves while being substantially parallel to the surface of the semiconductor wafer and contacts the entire one surface of the semiconductor wafer while rotating, and the entire first surface. The second grinding surface includes an end curved surface that is substantially perpendicular to the first grinding surface and reflects a rounded shape on the end surface of the semiconductor wafer, which is arbitrarily required for grinding. Equipped with a grinding wheel
Grinding one end of the semiconductor wafer until the semiconductor wafer has an arbitrary required thickness, and simultaneously grinding the end face of the semiconductor wafer so that the end face of the semiconductor wafer has a roundness according to the required thickness. And
[0012]
In the method of the present invention, when grinding the back surface of the semiconductor wafer after the circuit elements are formed on the main surface, the end surface of the semiconductor wafer is ground so that the end surface portion of the semiconductor wafer according to the required thickness has an appropriate roundness. To do.
[0013]
In the apparatus of the present invention, in order to realize the above-described method, the second grinding wheel having a recess reflecting the round shape on the end surface of the semiconductor wafer, which has an arbitrary required thickness by the back surface grinding, or the first grinding An integral grinding wheel including a second grinding surface continuous from the surface is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a conceptual diagram illustrating a wafer grinding method and apparatus according to a first embodiment of the present invention. The semiconductor wafer 1 has a circuit element already formed on its main surface so as to realize a predetermined function. After the main surface of the wafer 1 is covered and protected with a protective tape 2, for example, a substantial wafer grinding process is started.
[0015]
The main surface side of the wafer 1 is held by, for example, a vacuum suction chuck 3, and the back surface side and the end surface are exposed. Dotted lines 101 and 102 indicate the back surface and end surface of the wafer 1 before grinding, respectively. Thereafter, the entire back surface of the semiconductor wafer is ground by the surface grinding grindstone 4 until the wafer 1 has an arbitrary required thickness, that is, the wafer 1 has a required thickness. Before or after the step of grinding the entire back surface of the wafer 1, the end surface portion of the wafer 1 is ground by the end surface grinding wheel 5 so that the end surface of the wafer 1 is rounded according to the required thickness.
[0016]
The wafer 1 is rotated about the center of the wafer, and the grinding wheel 4 for surface grinding moves at least substantially parallel to the surface of the wafer 1 (arrow 41). Preferably, the grinding wheel 4 for surface grinding is brought into contact with the entire back surface of the wafer 1 while rotating in a direction opposite to the rotation direction of the wafer 1.
[0017]
Since the wafer 1 is made to have a predetermined required thickness by back surface grinding, the end grinding wheel 5 has a cylindrical shape provided with a recess 51 that realizes roundness of the end surface of the wafer 1 according to the required thickness. Be prepared. This end grinding wheel 5 grinds the end surface portion of the wafer 1 while moving toward the center of the wafer 1 as indicated by an arrow 52 along with the rotation.
[0018]
FIG. 2 is an enlarged view showing the vicinity of the wafer end face and the end face grinding wheel 5 similar to FIG. The same parts as those in FIG. The recess 51 has, for example, an arc shape whose cross section is less than a semicircle. When the radius of the arc is Rmm, it satisfies that R ≧ X / 2 with respect to the required thickness Xmm of the wafer 1 after the back grinding of the wafer 1. By defining one such condition for the recess 51, the end surface of the wafer after the backside grinding of the wafer 1 can be configured to continuously have an appropriate roundness.
[0019]
When the grinding of the end surface of the wafer 1 is performed before the step of grinding the entire back surface of the wafer 1, the portion below the lower curved surface of the concave portion 51 of the grinding wheel 5 for edge grinding is rounded to reflect the cylindrical shape. It can be shaved (11). However, the portion 11 is a portion that is removed later by grinding the entire back surface of the wafer 1. Therefore, the roundness of the end face adapted to the required thickness of the wafer 1 is realized as planned.
[0020]
When the grinding of the end surface of the wafer 1 is performed after the step of grinding the entire back surface of the wafer 1, the end surface of the wafer 1 is ground to reflect only the shape of the recess 51 of the grinding wheel 5 for end surface grinding. The roundness of the end face of the wafer 1 adapted to the thickness is realized.
[0021]
It can be said that the condition of the distance Dmm between the upper edge and the lower edge of the arc shape of the concave portion 51 of the end surface grinding wheel 5 is D ≧ X. However, the grinding accuracy in the planar direction has a margin more than matching the required thickness of the desired wafer so that it can be adequately handled even when slight variations occur in the thickness (required thickness) of the processed wafer. It is desirable to have a different shape.
[0022]
That is, if ΔX is considered as a variation in required thickness, it may be considered that D> X + ΔX. For this reason, the grinding wheel 5 for end face grinding can finely adjust the grinding amount (whetstone feed amount) to the wafer end face by a moving mechanism (not shown) to adjust the required shape.
[0023]
Although not shown, when the wafer 1 has an orientation flat and it is necessary to grind the end face of the orientation flat, the orientation flat of the wafer 1 whose rotation has stopped is separated from the above-mentioned wafer peripheral end face grinding. Then, the end surface grinding wheel 5 may be moved in parallel while being rotated so as to be uniformly contacted with the orientation flat for grinding.
[0024]
According to such an implementation method and embodiment, the end surface of the wafer 1 is rounded in accordance with the required thickness, and there is no acute angle portion, so that the occurrence of cracking and chipping of the wafer due to conveyance or the like can be suppressed.
[0025]
Note that the main surface side of the wafer 1 is held by, for example, the vacuum suction chuck 3 at the time of grinding. However, the present invention is not limited to this, and the main surface side is placed on a table so that the entire back surface of the wafer 1 is viewed from above. Is ground with the rotated surface grinding wheel 4 to have an arbitrary required thickness. The end surface portion of the wafer 1 may be ground so that the end surface of the wafer 1 is rounded before or after the step of grinding the entire back surface of the wafer 1 is performed.
[0026]
Further, depending on the end face shape of the wafer 1 before end face grinding, even if the recess shape cross section of the end face grinding grindstone 5 is not rounded, it may be processed so as not to have an acute angle portion. In such a case, the concave shape cross section of the grindstone 5 for end face grinding may be, for example, trapezoidal. That is, at the time of grinding, a trapezoidal corner is not reflected, and a wafer end face that takes advantage of the shape (round shape) of the end face of the wafer 1 before end face grinding is realized.
[0027]
FIG. 3 is a conceptual diagram for explaining a wafer grinding method and apparatus according to a second embodiment of the present invention. FIG. 4 is an enlarged view showing the vicinity of the wafer end face of FIG. These figures correspond to FIGS. 1 and 2, respectively. The difference from the first embodiment is the configuration of the grindstone 5 for end face grinding. Here, the end face grinding wheel 6 will be described in a cross-sectional view. The other parts are the same as those in the first embodiment described above, and are therefore denoted by the same reference numerals.
[0028]
The end surface grinding wheel 6 is characterized in that it can cope with a change in the required thickness of the wafer 1 to some extent. The grindstone 6 for end surface grinding is deformed by adjusting the length of a cylindrical portion extending between both curved surfaces forming the concave portion, reflecting the shape of the concave portion reflecting the round shape of the end surface portion of the semiconductor wafer. Can do. Thereby, the end surface portion of the wafer can be ground to some extent according to the required thickness of the semiconductor wafer to be changed.
[0029]
More specifically, the grindstone 6 for end face grinding has one curved surface 61 that forms a recess, the other curved surface 62, and a cylindrical portion 63 extending therebetween, and the length of the cylindrical portion 63 is arbitrary. A variable mechanism 65 for adjusting the length is included.
[0030]
In accordance with the required thickness of the wafer 1, the degree to which the cylindrical portion 63 extended on the one curved surface 61 is exposed to the concave surface by fine adjustment of the feed screw or the like by the variable mechanism 65 in advance is set. Thus, it has a structure which can change the recessed part shape of a grindstone. Thereby, end face grinding according to the required thickness of the wafer having a higher degree of freedom than the first embodiment becomes possible.
[0031]
The cylindrical portion 63 may be configured to extend on either the one curved surface side or the other curved surface side of the grindstone. Further, it is desirable that the concave shape has a continuous arc shape substantially less than at least a semicircle when the curved surface 61 is combined with the curved surface 61 and the cylindrical surface 63 is eliminated. However, when a problem arises in the strength of the grindstone due to processing, the curved surface 61 and the curved surface 62 have different arcs.
[0032]
Accordingly, the shape of the end surface grinding is adjusted by protruding the cylindrical portion 63 to some extent, and the end surface grinding grindstone 6 moves toward the center of the wafer 1 with its rotation, as in the first embodiment. The end surface portion of the wafer 1 is ground.
[0033]
It can be said that the condition of the required thickness Xmm of the wafer 1 and the distance Dmm between the upper edge and the lower edge of the concave portion of the grindstone 6 for end face grinding is D ≧ X. Since the concave shape of the grindstone can be changed, even when slight variations occur in the thickness (required thickness) of the wafer after processing due to the grinding accuracy in the planar direction, it can be sufficiently handled. Considering the variation ΔX of the required thickness X, the adjustment may be made by D> X + ΔX.
[0034]
In addition, when the wafer 1 has an orientation flat and it is necessary to grind the end face of the orientation flat, along with the orientation flat of the wafer 1 whose rotation is stopped separately from the wafer peripheral end face grinding as described above, What is necessary is just to grind evenly by contacting the orientation flat by moving the grindstone 6 for end surface grinding in parallel.
[0035]
According to such an implementation method and embodiment, the end face of the wafer 1 is rounded in conformity with the required thickness of the wafer 1 according to the change of the required thickness, and there is no acute angle portion. Can prevent cracking and chipping.
[0036]
FIG. 5 is a conceptual diagram for explaining a wafer grinding method and apparatus according to a third embodiment of the present invention. The semiconductor wafer 1 has a circuit element already formed on its main surface so as to realize a predetermined function. After the main surface of the wafer 1 is covered with, for example, the tape 2 and protected, a substantial wafer grinding process is started.
[0037]
The main surface side of the wafer 1 is held by, for example, a vacuum suction chuck 3, and the back surface side and the end surface are exposed. Thereafter, in the present invention, the entire back surface of the wafer 1 is ground until the wafer 1 has an arbitrary required thickness, and at the same time, the end surface of the wafer 1 is ground so that the end surface portion of the wafer 1 is round according to the required thickness. The object is achieved by the body grinding wheel 7.
[0038]
The integrated grinding wheel 7 is shown in a sectional view in FIG. The first grinding surface 71 that contacts the entire back surface of the wafer 1 while moving and rotating while remaining substantially parallel to the surface of the semiconductor wafer 1 and the end surface of the wafer 1 that has an arbitrary required thickness by grinding the entire back surface The 2nd grinding surface 72 which comprises the end curved surface which continued in the perpendicular direction from the 1st grinding surface 71 reflecting the round shape of this is included. The wafer 1 rotates in the direction opposite to the rotation direction of the integrated grinding wheel 7 around the center thereof and comes into contact with the integrated grinding wheel 7 so that the back surface and the end surface are ground together.
[0039]
FIG. 6 shows an enlarged view of the second grinding surface 72. When the radius constituting the end curved surface at the second grinding surface 72 is Rmm, R ≦ X / 2 is satisfied with respect to the required thickness Xmm after the back surface grinding of the wafer 1. By defining in this way, it is possible to prevent an acute angle portion from appearing on the end face of the wafer 1 when the grinding of the wafer 1 is completed.
[0040]
That is, at the end face of the wafer 1, at least the ground corner on the back side has a radius R. Also, the corners on the surface side partially leave roundness before grinding.
[0041]
Here, when the end surface of the wafer 1 is ground, the grinding is advanced so that the outermost periphery of the end surface of the wafer 1 does not substantially come out of the outermost peripheral point P1 of the grinding surface. In addition, it is preferable that the center of rotation of the wafer 1 and the center of rotation of the integral grinding wheel 7 are substantially coincident with each other, but this is not always necessary, and offset from the beginning of grinding. May be.
[0042]
According to such an implementation method and embodiment, the end surface of the wafer 1 is rounded in accordance with the required thickness, and there is no acute angle portion, so that the occurrence of cracking and chipping of the wafer due to conveyance or the like can be suppressed.
[0043]
FIG. 7 is a modification of the second grinding surface 72. A wall portion 721 that is substantially perpendicular to the first grinding surface 71 extends upward from the end curved end surface. Depending on the required thickness of the wafer 1, a flat surface reflecting the wall portion 721 from the second grinding surface 72 appears so as to be connected to a corner on the wafer 1 surface side.
[0044]
At this time, with respect to the end face of the wafer 1, the corner on the back surface side of the wafer 1 has a uniform roundness reflecting the second grinding surface 72, and the corner on the front surface side of the wafer 1 has a roundness of the wafer that has been rounded before grinding. This means that an angle larger than a right angle is left (even if a portion of the roundness of the wafer that is crushed before grinding is not left, the portion does not become smaller than the right angle). After all, the end face of the wafer 1 can be eliminated from an acute angle portion, and has a roundness that can be adapted to the required thickness. Thereby, generation | occurrence | production of the crack of a wafer by conveyance etc. and a chip can be suppressed.
[0045]
In addition, FIG. 7 has a slope 722 that tapers from the end of the wall portion 721 toward the upper edge. By having the inclined surface 722, a slight margin can be given to the accuracy of guiding the wafer 1.
[0046]
The inclined surface 722 is not a portion that substantially grinds the end surface of the wafer. Finally, the radius R of the second grinding surface 72 and the dimension of the wall portion 721 must be set so that grinding is not performed so that the end surface of the wafer reflects the inclined surface 722. Further, a configuration in which the wall portion 721 is not provided in FIG.
[0047]
As described above, according to the method and apparatus for collectively grinding the back surface and the end surface of the wafer, the flat surface portion has a shape that sufficiently satisfies the required accuracy such as the degree of balance, and the gentle arc-shaped portion is the end surface of the wafer. It is possible to grind the part and finally use the part of the round shape originally applied to the wafer itself, and finally process it into a shape without an acute angle part.
[0048]
In each of the embodiments described above, the processing method has been described in which the wafer is horizontally installed. However, the processing may be performed in the vertical direction, or may be a method in which the wafer is turned upside down and the planar grindstone is moved from above.
[0049]
【The invention's effect】
As described above, according to the present invention, when grinding the back surface of the semiconductor wafer after the circuit elements are formed on the main surface, the end surface portion of the semiconductor wafer according to the required thickness has an appropriate roundness. To provide a method and apparatus for grinding a wafer so that an appropriate roundness can be surely made at least in a continuous portion of a back surface-cutting portion and a wafer peripheral portion before, or after or simultaneously with the step of grinding a back surface of a semiconductor wafer. it can.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating a wafer grinding method and apparatus according to a first embodiment of the present invention.
2 is an enlarged view showing the vicinity of the wafer end face in FIG. 1; FIG.
FIG. 3 is a conceptual diagram illustrating a wafer grinding method and apparatus according to a second embodiment of the present invention.
4 is an enlarged view showing the vicinity of the wafer end face in FIG. 3;
FIG. 5 is a conceptual diagram illustrating a wafer grinding method and apparatus according to a third embodiment of the present invention.
6 is an enlarged view of a part of a grinding surface having the configuration of FIG.
FIG. 7 is a conceptual diagram showing a modification of the shape of the grinding surface according to the third embodiment.
FIG. 8 is a conceptual diagram for explaining conventional grinding of a wafer.
FIG. 9 is an enlarged view showing a state of a wafer end surface portion after the wafer grinding step.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer 2 ... Protective tape 3 ... Vacuum adsorption chuck 4 ... Surface grinding wheel 5, 6 ... End surface grinding wheel 7 ... Integrated grinding wheel

Claims (7)

A step of protecting a main surface of a semiconductor wafer on which circuit elements are formed in order to realize a predetermined function;
Regarding the semiconductor wafer, supporting the main surface side and exposing the back surface and the end surface;
Grinding the entire back surface of the semiconductor wafer until the semiconductor wafer has an arbitrary required thickness, and simultaneously grinding the end surface of the semiconductor wafer so that the end surface of the semiconductor wafer has a roundness according to the required thickness; A method for grinding a wafer, comprising: Using an integral grindstone for grinding the entire back surface and the end surface of the semiconductor wafer, it is moved while being substantially parallel to the semiconductor wafer surface while rotating, and contacts the entire back surface and the end surface of the semiconductor wafer. The wafer grinding method according to claim 1, wherein: 3. The method of grinding a wafer according to claim 2, wherein the semiconductor wafer is ground while rotating in a direction opposite to a rotation direction of the grindstone. The first ground surface that moves while being substantially parallel to the surface of the semiconductor wafer and contacts the entire one surface of the semiconductor wafer while rotating, and the semiconductor having an arbitrary required thickness by grinding the entire one surface A grinding wheel constituted by a second grinding surface including an end curved surface that is substantially perpendicular to the first grinding surface and reflects a rounded shape on an end surface of the wafer;
  Grinding one end of the semiconductor wafer until the semiconductor wafer has an arbitrary required thickness, and simultaneously grinding the end face of the semiconductor wafer so that the end face of the semiconductor wafer has a roundness according to the required thickness. Wafer grinding equipment. 5. The wafer grinding apparatus according to claim 4, further comprising a rotation drive mechanism that holds the other surface of the semiconductor wafer and rotates the semiconductor wafer about the semiconductor wafer in a direction opposite to a rotation direction of the grinding wheel. 6. The radius Rmm of the end curved surface of the second grinding surface is R ≦ X / 2 with respect to a required thickness Xmm after grinding of one surface of the semiconductor wafer. Wafer grinding equipment. 6. The wafer grinding apparatus according to claim 5, wherein the grinding wheel has an inclined surface having a tapered shape from an end of the second grinding surface toward an upper edge portion.

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