JPH07105370B2 - Backside processing method for semiconductor wafer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a back surface processing method for a semiconductor wafer in a semiconductor manufacturing process.

<Prior Art> Conventionally, in the general manufacturing process of semiconductors such as diodes and transistors, as shown in the process diagram of FIG. 4 (a), a sandblast or a grindstone is applied to the back surface of a semiconductor wafer made of silicon. It has been practiced to reduce the thickness of a semiconductor wafer by performing a grinding process by, for example, and to finish the back surface of the semiconductor wafer to be smooth by etching and to form a metal layer on the smooth back surface.

At this time, since the processing pattern 31, ... As shown in FIG. 5 is already formed on the surface 30a of the semiconductor wafer 30,
A surface protection treatment is performed to avoid the influence of the back surface treatment. As the first method of such surface protection treatment, as shown in the procedure in FIG. 4 (b), a method of using a protective sheet and forming a resist film, and the second method is As shown in FIG. 4 (c), a method of forming a resist film twice is known. 6 (a) and 6 (b) are side views showing the semiconductor wafer 30 in a state in which these methods have been carried out, and the reference numeral 32 in FIG. 6 (a) is a protective sheet, and FIG. Symbols in Figure (b)
33 is a resist film.

Next, each of the methods for processing the back surface of such a semiconductor wafer will be described.

In the first method, first, the surface 30 of the semiconductor wafer 30 is
After attaching the protective sheet 32 made of plastic to a, the back surface 30b is ground, and the protective sheet 32 is removed after the grinding is completed. Next, the semiconductor wafer 30
After forming a resist film 33 capable of preventing the invasion of the etching solution on the front surface 30a, etching treatment is performed in a liquid phase or a vapor phase to finish the back surface 30b to be smooth, and then the resist film 33 is removed. Then, after removing the resist film 33, the back surface of the semiconductor wafer 30 is subjected to a vapor deposition process.
A metal layer is formed on 30b.

The reason why the protective film 32 is peeled off and the resist film 33 is formed before the etching process is as follows. That is, in general, the surface 30a of the semiconductor wafer 30
Then, as shown in FIG. 5, the dividing grooves 34, ... Forming the processing patterns 31, .. reach the peripheral edge of the semiconductor wafer 30. Protective sheet 32 attached to the semiconductor wafer surface 30a
Since the dividing grooves 34, ... Of the adhesive 35 have a very small size, it is impossible to fill and seal the dividing grooves 34 ,. Therefore, if the etching treatment is performed with the protective sheet 32 attached before the back surface grinding process attached to the semiconductor wafer front surface 30a, the etching solution, a so-called etchant, is generated from the divided grooves 34, ... Opened in the peripheral edge of the semiconductor wafer 30. Inconveniences such as invasion and erosion of the processing patterns 31 ,. In order to prevent such an inconvenience from occurring, the protective sheet 32 must be peeled off, and the resist film 33 must be formed thick to fill the openings of the dividing grooves 34, ....

In addition, in the second method, the surface 30 of the semiconductor wafer 30 is
After the resist film 33 is formed on a, the back surface 30b is ground, the resist film 33 damaged by the grinding is once removed, and the resist film 33 is formed again.
Next, after performing a liquid phase or gas phase etching process to finish the back surface 30b of the semiconductor wafer 30 to be smooth,
The resist film 33 is removed. After removing the resist film 33, the back surface 30b of the semiconductor wafer 30 is subjected to a vapor deposition process to form a metal layer.

<Problems to be Solved by the Invention> As described above, in any of the first and second back surface processing methods, the protective sheet 32 is peeled off to form the resist film 33 every time the semiconductor wafer 30 is etched. Alternatively, since it is necessary to re-form the resist film 33, the back surface processing of the semiconductor wafer 30 is troublesome and the productivity is low. Moreover, thin semiconductor wafers
Since the resist film 33 must be formed thick in order to obtain acid resistance with respect to 30, workability was also poor in this respect.

In view of such conventional problems, an object of the present invention is to provide a method for processing the back surface of a semiconductor wafer, which can save the labor required for the surface protection processing and improve the productivity.

<Means for Solving Problems> In order to achieve such an object, the present invention leaves a smooth surface portion on which a processing pattern is not formed around the surface of a semiconductor wafer, and a protective sheet is provided on the surface. After sticking and covering the entire surface, the back surface of the semiconductor wafer is ground, and the back surface is finished smooth by etching while the protection sheet is stuck to the front surface, and the protection is performed from the front surface. After peeling the sheet, a metal layer is formed on the back surface.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a semiconductor wafer processing step diagram, FIG. 2 is a plan view of a semiconductor wafer to be processed, and FIG. 3 is a side view of a semiconductor wafer in a state where surface protection processing is performed. Reference numeral 10 in FIGS. 2 and 3 denotes a semiconductor wafer made of silicon or the like, and the surface 10 of the semiconductor wafer 10
a has a number of machining patterns 12, which are divided by dividing grooves 11 ,.
, And the smooth surface portion 13 on which the processing pattern is not formed is left around the surface 10a. Also,
Reference numeral 14 in FIG. 3 is a protective sheet for protecting the surface 10a of the semiconductor wafer, which is made of plastic having acid resistance.

Next, the processing of such a semiconductor wafer 10 will be sequentially described based on the process diagram of the back surface treatment shown in FIG. 1A and the process diagram of the surface protection treatment of FIG. 1B.

First, a protective sheet 14 is attached to the front surface 10 of the semiconductor wafer to cover the entire surface so that the processing patterns 12, ... Formed on the front surface 10a of the semiconductor wafer 10 are not adversely affected by the back surface processing. After that, the back surface 10b of the semiconductor wafer 10 is ground by sandblasting or a grindstone to reduce its thickness.

Next, with the protective sheet 14 still attached to the front surface 10a of the semiconductor wafer, an etching process in a liquid phase or a vapor phase is performed to finish the back surface 10b of the surface smooth. At this time,
Since the dividing grooves 11, ... Formed on the surface 10a of the semiconductor wafer 10 do not reach the peripheral edge of the surface 10a, the peripheral edge is sealed by the protective sheet 14, and the etchant enters the semiconductor wafer surface 10a and the processing pattern 12 is formed. It does not adversely affect, ....

After completion of this etching process, the protective sheet 14 is peeled off, and the semiconductor wafer back surface 10b is formed by a vapor deposition process.
A metal layer is formed on.

If an adhesive sheet made of an ultraviolet curable resin is used as the protective sheet 14 in the above description, the adhesive 15 portion is cured by irradiation with ultraviolet rays, so that the semiconductor wafer 10
The protective sheet 14 can be peeled off very easily. Therefore, there is no inconvenience that the semiconductor wafer 10 breaks when peeling. Also, the surface 10a
The smooth surface part 13 where the processing pattern 12, ... Is not formed around the
Since it is possible to manufacture the semiconductor wafer 10 having the above, only by changing the pattern mask used in the processing pattern forming step, there is no need to change the manufacturing step, and it can be easily carried out. Further, such a semiconductor wafer 10 is to be divided in the next process, but since this division is performed after being positioned on the surface 10a with a dicing saw or the like with reference to the dividing grooves 11, ... There is no problem even if the smooth surface portion 13 is formed around the surface 10a.

<Effects of the Invention> As described above, according to the present invention, since the protective sheet is attached to the semiconductor wafer having the smooth surface portion in which the processing pattern is not formed around the surface, the surface of the semiconductor wafer is etched during the etching process on the back surface thereof. Since the etchant does not enter, the etching treatment can be performed with the protective sheet attached before the grinding process. Therefore, it is not necessary to peel off the protective sheet to form a thick resist film or to re-form the resist film, so that the labor required for the surface protection treatment can be omitted and the productivity can be improved.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a process diagram of a semiconductor wafer processing, FIG. 2 is a plan view of a semiconductor wafer to be processed, and FIG. It is a side view of the semiconductor wafer in the implemented state. Also, the fourth
1 to 6 show a conventional example, FIG. 4 is a processing step diagram of a semiconductor wafer, FIG. 5 is a plan view of a semiconductor wafer, and FIG. 6 is a side surface of a semiconductor wafer in a state where surface protection processing is performed. It is a figure. 10 ... Semiconductor wafer, 10a ... Semiconductor wafer surface, 10b
…… Surface of semiconductor wafer, 12 …… Processing pattern, 13 ……
Smooth surface, 14 …… Protective sheet.

Claims (1)

[Claims] 1. A smooth surface portion on which a processing pattern is not formed is left around the front surface of a semiconductor wafer, a protective sheet is attached to the surface to cover the entire surface, and then the back surface of the semiconductor wafer is ground. And, after the protective sheet is adhered to the front surface, the back surface is finished to be smooth by an etching process, and after the protective sheet is peeled from the surface, a metal layer is formed on the back surface. Backside processing method for semiconductor wafer.