JP2012138462A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently inhibit, without using a special device, cracks and chipping of a semiconductor wafer with a rear face being ground.SOLUTION: A semiconductor device manufacturing method comprises a step of forming an oxide film 4 by selectively oxidizing a circumferential part of a semiconductor wafer 2 on a rear face side (rear face circumference 1) after grinding the rear face, and a step of removing the oxide film 4 by etching. Accordingly, a portion from the rear face 5 to a circumference 6 of the semiconductor wafer 2 can be beveled.

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  In general, a semiconductor wafer used in various semiconductor devices such as a semiconductor package is thinned by back surface grinding in order to reduce the height (thinner thickness) of the semiconductor device.

  However, when the semiconductor wafer is thinned by backside grinding, cracks and chipping (chipping) are likely to occur at the periphery. The thinner the semiconductor wafer, the sharper the cross-sectional shape of the end face, and the easier it is to crack or chip.

  As techniques for suppressing such cracks and chips, there are those described in Patent Documents 1 and 2.

  In the technique of Patent Document 1, cracking and chipping are suppressed by finishing the back surface grinding before the angle formed between the end surface and the back surface of the semiconductor wafer becomes an acute angle.

  In the technique of Patent Document 2, cracking and chipping are suppressed by rounding the end surface of the semiconductor wafer after the back surface grinding with a special grinding machine. The grinding machine of Patent Document 2 has a dome-shaped rotating body and a grindstone provided on the inner peripheral surface of the rotating body, and rounds the end surface of the semiconductor wafer with the grindstone.

JP 2001-15395 A Japanese Patent Laid-Open No. 10-41259

However, in the technique of Patent Document 1, since the end surface and the back surface of the semiconductor wafer are not continuous curved surfaces, and there are corners that are obtuse at their boundaries, it is possible to sufficiently suppress cracking and chipping. Have difficulty.
Further, the technique of Patent Document 2 requires a special grinding machine for rounding the end face of the semiconductor wafer.

  Thus, it has been difficult to sufficiently suppress the cracking and chipping of the back-ground ground semiconductor wafer without requiring a special apparatus.

The present invention includes a step of forming an oxide film by selectively oxidizing the back surface side of the peripheral portion of the semiconductor wafer after back surface grinding,
Removing the oxide film by etching;
A method for manufacturing a semiconductor device is provided.

According to this method for manufacturing a semiconductor device, an oxide film is formed by selectively oxidizing the back surface side of the peripheral portion of the semiconductor wafer after the back surface grinding, and the oxide film is removed by etching to thereby remove the back surface of the semiconductor wafer. The chamfering of the site | part from a peripheral part can be performed. Thereby, the corner | angular part of the boundary of a back surface and a peripheral part can be eliminated, and it can be set as a continuous curved surface from a back surface to a peripheral part. Therefore, compared with the case where a corner | angular part exists in the boundary of a back surface and a peripheral part, the stress concentration to the boundary part can be suppressed. Therefore, it is possible to sufficiently suppress the cracking and chipping of the peripheral portion of the semiconductor wafer.
That is, it is possible to sufficiently suppress cracking and chipping of the back-ground ground semiconductor wafer without requiring a special device.

  According to the present invention, it is possible to sufficiently suppress cracking and chipping of a back-ground ground semiconductor wafer without requiring a special apparatus.

It is a sectional side view showing a series of processes of a manufacturing method of a semiconductor device concerning an embodiment. It is a figure for demonstrating the process of inject | pouring oxygen ion.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  FIG. 1 is a side cross-sectional view showing a series of steps of a method for manufacturing a semiconductor device according to an embodiment.

  The manufacturing method of the semiconductor device according to the present embodiment includes a step of forming the oxide film 4 by selectively oxidizing the back surface side (back surface peripheral portion 1) of the peripheral portion of the semiconductor wafer 2 after back surface grinding, and the oxide film. 4 is removed by etching. Details will be described below.

First, as shown in FIG. 1A, a semiconductor wafer 2 whose back surface is ground is prepared. The semiconductor wafer 2 is, for example, a silicon wafer.
Here, the semiconductor wafer 2 has its peripheral edge (bevel part) 6 chamfered in advance before the back surface grinding is performed. This chamfering process is performed, for example, such that the inclination angle gradually changes from the front surface 9 of the semiconductor wafer 2 to the peripheral edge portion 6. Similarly, the back surface of the semiconductor wafer 2 (FIG. 1A). The inclination angle is gradually changed from the back surface before back surface grinding (not shown in FIG. 2) to the peripheral edge portion 6.
However, as shown in FIG. 1A, as a result of the back surface grinding, corner portions 7 are formed at the boundary between the back surface 5 and the peripheral edge portion 6.

  Next, as shown in FIG. 1B, a resist 3 is formed on the back surface 5 of the semiconductor wafer 2 to form a mask. Here, the resist 3 is formed so that the peripheral portion of the back surface 5 (the back surface peripheral portion 1) is exposed. More specifically, the resist 3 is preferably formed such that the position of the outer peripheral edge 3 a is located closer to the end of the semiconductor wafer 2 than the boundary 8 between the surface 9 and the peripheral edge 6. The resist 3 can be formed, for example, by applying a photosensitive organic film to the back surface 5 and exposing and developing.

Next, oxygen ions are implanted from the back surface 5 side of the semiconductor wafer 2. This oxygen ion implantation is performed using the resist 3 as a mask. For this reason, oxygen ions are selectively implanted into the rear surface peripheral edge portion 1.
Here, when oxygen ions are implanted, by gradually decreasing the ion implantation energy from the outer periphery of the semiconductor wafer 2 toward the center, the portion closer to the center of the semiconductor wafer 2 is shallower and the portion closer to the outer periphery of the semiconductor wafer 2 is closer. Deeply implant oxygen ions.

  FIG. 2 is a diagram for explaining a process of implanting oxygen ions. 2A is a side view of the semiconductor wafer 2 at the time of oxygen ion implantation, FIG. 2B is a diagram showing the back side of the semiconductor wafer 2 into which oxygen ions are implanted, and FIG. FIG. 5 is a diagram showing a profile of oxygen ion implantation depth at the peripheral edge of a semiconductor wafer 2 into which is implanted. In FIG. 2A, the resist 3 is not shown.

  As shown in FIG. 2A, oxygen ions are implanted into the back surface peripheral portion 1 of the semiconductor wafer 2 by implanting oxygen ions through a mask 10 in which slits 11 are formed at positions corresponding to the back surface peripheral portion 1. Do by. By rotating the semiconductor wafer 2 in a plane parallel to the plate surface during ion implantation, oxygen ions can be implanted in a ring shape along the peripheral edge 1 of the back surface (see FIG. 2B). Here, by gradually changing the implantation energy of oxygen ions in the radial direction of the semiconductor wafer 2 (by gradually decreasing the ion implantation energy from the outer periphery of the semiconductor wafer 2 toward the center), the energy near the center of the semiconductor wafer 2 is increased. Oxygen ions can be implanted as shallow as possible, and deeper as the portion near the outer periphery of the semiconductor wafer 2 (FIG. 2C).

  Next, the semiconductor wafer 2 is annealed. As a result, the portion where the oxygen ions are implanted in the semiconductor wafer 2, that is, the back surface peripheral portion 1 is selectively oxidized, and the oxide film 4 is selectively formed on the back surface peripheral portion 1 (FIG. 1C). Here, as shown in FIG. 1C, the oxide film 4 is shallower toward the center of the semiconductor wafer 2 and deeper toward the outer periphery of the semiconductor wafer 2.

As described above, in the present embodiment, the oxide film 4 is formed in a state in which a portion other than the peripheral portion (back surface peripheral portion 1) on the back surface 5 of the semiconductor wafer 2 is covered with the mask (resist 3).
The oxide film 4 is formed by selectively implanting oxygen ions into the back surface side (back surface peripheral portion 1) of the peripheral portion 6 of the semiconductor wafer 2 and back surface side (back surface peripheral portion 1) of the peripheral portion 6. And thermal oxidation by annealing.
The step of implanting oxygen ions is performed such that the portion closer to the center of the semiconductor wafer 2 has a smaller oxygen ion implantation depth.

  Next, the resist 3 is removed.

Next, as shown in FIG. 1 (d), the oxide film 4 is removed by etching, thereby chamfering a portion from the back surface 5 to the peripheral edge portion 6 of the semiconductor wafer 2. Thereby, the corner 7 at the boundary between the back surface 5 and the peripheral edge portion 6 is eliminated, and a continuous curved surface is formed from the back surface 5 to the peripheral edge portion 6.
Since the oxide film 4 is shallower toward the center of the semiconductor wafer 2 and deeper toward the outer periphery of the semiconductor wafer 2, the oxide film 4 can be easily removed to easily remove the peripheral edge 6 of the semiconductor wafer 2. Can be formed in a rounded shape.
This etching is preferably highly isotropic etching (isotropic etching). By performing highly isotropic etching, it is easy to form a continuous curved surface from the back surface 5 to the peripheral edge portion 6, and the corner portion 7 can be eliminated more reliably. This etching can be, for example, wet etching.
This etching may be performed by immersing the entire semiconductor wafer 2 in the etching solution, or by immersing only the peripheral portion 6 (including the back surface peripheral portion 1) of the semiconductor wafer 2 in the etching solution. good.
Here, the chamfering by removing the oxide film 4 is performed by using an etching solution in which the oxide film 4 (that is, silicon oxide) has a higher etching rate than the semiconductor wafer 2 (that is, mainly silicon). Can be done.

  Since the corner 7 can be eliminated by chamfering in this way, stress concentration can be suppressed as compared with the case where the corner 7 exists. Therefore, it is possible to sufficiently suppress the cracking and chipping of the peripheral edge portion 6 (particularly the back surface peripheral edge portion 1) of the semiconductor wafer 2.

According to the embodiment as described above, the step of forming the oxide film 4 by selectively oxidizing the back surface side (back surface periphery 1) of the periphery 6 of the semiconductor wafer 2 after back grinding, and the oxide film 4 And removing by etching. Therefore, it is possible to chamfer the part from the back surface 5 to the peripheral edge 6 of the semiconductor wafer 2. Thereby, the corner | angular part 7 of the boundary of the back surface 5 and the peripheral part 6 can be eliminated, and it can be set as a continuous curved surface from the back surface 5 to the peripheral part 6. FIG. Therefore, compared with the case where the corner portion 7 exists at the boundary between the back surface 5 and the peripheral edge portion 6, the stress concentration at the boundary portion can be suppressed. Therefore, it is possible to sufficiently suppress cracks and chipping of the peripheral edge 6 of the semiconductor wafer 2.
That is, it is possible to sufficiently suppress the cracking and chipping of the back-ground semiconductor wafer 2 without requiring a special device.

  In the technique of Patent Document 1, since the back surface grinding is finished before the angle between the end surface and the back surface of the semiconductor wafer becomes an acute angle, the semiconductor wafer may not be processed to a desired thickness. On the other hand, in the present embodiment, at the stage of FIG. 1A, the angle formed between the end surface (peripheral portion 6) of the semiconductor wafer 2 and the back surface 5 may be an acute angle. It can be thinned until it is thick.

DESCRIPTION OF SYMBOLS 1 Back surface peripheral part 2 Semiconductor wafer 3 Resist 3a Outer peripheral edge 4 Oxide film 5 Back surface 6 Peripheral part 7 Corner | angular part 8 Boundary 9 Surface 10 Mask 11 Slit

Claims (5)

Forming an oxide film by selectively oxidizing the back side of the peripheral edge of the semiconductor wafer after back grinding; and
Removing the oxide film by etching;
A method for manufacturing a semiconductor device, comprising: The step of forming the oxide film includes
Selectively implanting oxygen ions into the back side of the peripheral edge of the semiconductor wafer;
Thermally oxidizing the back surface side of the peripheral portion by annealing;
The method of manufacturing a semiconductor device according to claim 1, wherein:   3. The method of manufacturing a semiconductor device according to claim 2, wherein the step of implanting oxygen ions is performed such that a portion closer to the center of the semiconductor wafer has a shallower depth of implantation of the oxygen ions.   The method for manufacturing a semiconductor device according to claim 1, wherein isotropic etching is performed in the step of removing the oxide film by etching. The step of forming the oxide film includes
5. The method of manufacturing a semiconductor device according to claim 1, wherein the method is performed in a state where a portion other than the peripheral portion on the back surface of the semiconductor wafer is covered with a mask.

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