JP2002134451A - Manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional constitutions, where a warpage is produced in a wafer by the thermal distortion and the difference in linear expansion coefficients of nitride films in the heat treatment process of a semiconductor element region forming process, and as the thickness of the wafer is reduced in recent times, many cracking damages of wafers caused by the warpages are produced in wafers, whose finished thicknesses are not thicker than 150 μm in a B/G grinding process. SOLUTION: Grooves are formed on dicing streets used in an assembly process by etching in a plasma treatment. Using such a constitution, a tensile stress causing a warpage is divided and the warpage is reduced before a B/G grinding process, so that the tightness between a table and a wafer can be improved; and even if the finished thickness of the wafer is thinner than the conventional thickness, defects produced by wafer crackings and damages can be significantly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device which prevents wafer damage during back grinding of a thin film wafer.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, after a semiconductor element region is formed on a wafer, the wafer is attached to a sheet so as to have a desired finished thickness, and B / G grinding is performed.

FIG. 5 shows a conventional method of manufacturing a semiconductor device.

An oxide film and a nitride film 12 are deposited on the surface of a one conductivity type silicon semiconductor substrate 11, a predetermined base region surface is exposed by etching, and a reverse conductivity type impurity is ion-implanted and then diffused to form a base region 13. I do.

A predetermined emitter region portion on the surface of the base region 13 is exposed again by etching, an impurity of one conductivity type is attached, and then diffused to form an emitter region 14.

[0006] Contact holes are provided in the base region 13 and the emitter region 14, and a metal is adhered thereto and etched into a desired electrode shape to form a base electrode 17 and an emitter electrode 18.

The back surface of the semiconductor substrate 11 is subjected to B / G grinding to a desired finished thickness of, for example, 150 μm or 200 μm, and a metal is attached to the back surface by vacuum evaporation to form a collector electrode (not shown).

[0008]

In recent years, there has been an increasing demand for thinner packages, and in order to cope with the demand, it is desired to further reduce the thickness of wafers and to manufacture semiconductor devices with high efficiency and low loss.

However, if B / G grinding is performed so that the finished thickness of the wafer is thinner than the current mainstream of 150 μm, there is a problem that wafer cracking occurs frequently. This is because the warpage of the wafer increases due to the difference in the thermal expansion and the coefficient of linear expansion of the nitride film in each heat treatment step.
Adhesion to the vacuum chuck is weakened by grinding, and cracks occur due to the wafer fluttering up and down during grinding, particularly at the periphery of the wafer, and cracks also occur during MPC work due to weak adhesion to the vacuum chuck.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a method of manufacturing a semiconductor device having a desired finished thickness by grinding a back surface of a wafer after a semiconductor element region is formed. The dicing street portion is etched by plasma processing to 1 to 10 μm.
By providing a groove having a depth of not more than one, the warpage of the wafer is reduced, and the adhesion between the vacuum chuck and the wafer during B / G grinding is increased to greatly reduce damage defects.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to the present invention is directed to a method of manufacturing a semiconductor device having a desired finished thickness by grinding a back surface of a wafer after forming a semiconductor element region.
The grinding is performed by providing a groove in the dicing street.

An embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 is a sectional view of a wafer after a semiconductor element region is formed.

An oxide film and a nitride film 2 are deposited on the surface of a one conductivity type silicon semiconductor substrate 1, a predetermined base region surface is exposed by etching, and a reverse conductivity type impurity is ion-implanted and then diffused to form a base region 3. I do.

A predetermined emitter region portion on the surface of the base region 3 is again exposed by etching, an impurity of one conductivity type is attached, and then diffused to form an emitter region 4.

Contact holes are provided in the base region 3 and the emitter region 4, a metal is adhered, a mask is formed with a resist film 5 so as to have a desired electrode shape, and etching is performed to form a base electrode 7 and an emitter electrode 8. . Thereafter, the next process is performed while the resist film 5 is left.

FIGS. 2 and 3 show a process of B / G grinding by forming a groove along a dicing street which is a feature of the present invention.

FIG. 2 shows that the mask of the resist film 5 is provided on the entire surface of the semiconductor substrate so that the dicing street 9 is exposed, and the semiconductor substrate is etched by plasma processing.
A groove 10 having a depth of 1 to 10 μm is provided on the dicing street 9.

The provision of the groove 10 can greatly reduce wafer cracking. This is presumed to be because the tensile stress, which is a cause of warpage generated in the wafer, is divided by the groove 10 due to the difference in the thermal expansion and the coefficient of linear expansion of the nitride film in each heat treatment step.

Since the dicing street 9 is a region for individually dividing (dicing) the semiconductor element in a later assembling process, providing the groove 10 at this stage has no effect. However, the depth of the groove 10 is 1 μm
The thickness is preferably 10 μm or more and 10 μm or less.

FIG. 3 shows that the resist film is removed and the back surface is B / G
This shows the step of grinding.

The resist film 5 on the front surface is removed, a protective sheet is put on the front surface, and the back surface of the semiconductor substrate 1 is B / G ground to a desired finished thickness. As described above, since the tensile stress, which is a cause of warpage, is divided by the groove 10 provided in the dicing street 9, the difference in the coefficient of linear expansion of the nitride film and the heat in each heat treatment step are formed in the step of forming the semiconductor element region. B / G even if the wafer is warped due to distortion
This warpage can be reduced before grinding.

As a result, the adhesiveness between the B / G grinding table and the wafer is improved, and even if the finished thickness of the wafer is made thinner than before, wafer cracking and defects due to damage can be greatly reduced.

Thereafter, a metal is adhered to the back surface by vacuum evaporation to form a collector electrode (not shown).

The feature of the manufacturing method of the present invention is that plasma etching is performed on
After providing a groove of μm, B / G grinding is performed.

Due to the groove 10, even if the wafer is warped due to a difference in linear expansion coefficient of the nitride film or thermal distortion in each heat treatment step in the process of forming the semiconductor element region up to now, the warpage is not affected. The tensile stress which is the cause is divided, and the warpage can be reduced before B / G grinding.

Accordingly, the adhesiveness between the B / G grinding table and the wafer is improved, and even if the wafer is ground so that the finished thickness of the wafer becomes thinner than before, the wafer cracking and defects due to damage can be greatly reduced.

Here, the reason why the depth of the groove 10 is set to 1 to 10 μm will be described with reference to a table of wafer cracking defective rates shown in FIG. This table is obtained by measuring the defect rate for each finished thickness of the wafer by changing the depth of the groove 10 due to the plasma etching.

First, as shown in FIG.
In this example, the defect rate at a wafer finished thickness of 120 μm is about 1%, but when no groove is provided (0 μm), the defect rate at a wafer finished thickness of 120 μm increases. this is,
If the depth of the groove 10 is less than 1 μm, the tensile stress cannot be sufficiently divided. In this state, if the B / G grinding is performed and the metal deposition applied to the back surface further increases the warp, the thickness of the finished wafer is reduced. This is because the mechanical strength of the wafer is reduced due to the thinner.

That is, when the groove 10 is shallower than 1 μm, there is no problem with the thickness of 150 μm, which is currently the mainstream. However, as the wafer becomes thinner, cracks occur everywhere on the wafer.

On the other hand, when the depth of the groove 10 is 10 μm, the wafer finished thickness is 120 μm and the defect rate is less than 1%, but when the depth of the groove 10 is 15 μm, the wafer finished thickness is reduced.
The defect rate at 130 μm or less increases. This is because when the wafer is warped, a crack is generated from the groove 10 itself,
When the water at the time of B / G grinding enters the adhesive in the gap between the sheet and the groove 10 to be bonded in the B / G grinding step, the sheet is peeled off, and the wafer cannot be fixed at the time of grinding, so that cracks occur frequently. Also, by providing a large number of deep grooves 10 in the wafer, the strength of the wafer is reduced,
This is because defects such as cracks generated during handling during metal deposition on the back surface increase.

The depth of the groove 10 is 2 μm and 5 μm.
In this example, the result that the wafer defect rate is 0% is obtained.

From the above, it can be said that the depth of the groove 10 for preventing the wafer crack is preferably 1 to 10 μm.

[0034]

According to the present invention, by performing B / G grinding after forming a groove by performing plasma etching on the dicing street, defects due to wafer cracking and damage can be greatly reduced.

After forming the semiconductor element region, grooves are formed by etching the dicing streets by plasma processing. Even if the wafer is warped due to the difference in the coefficient of linear expansion of the nitride film and the thermal strain in each heat treatment step in the process of forming the semiconductor element region up to now, even if the wafer is warped, the tensile stress causing the warp is generated. , And warpage can be reduced before B / G grinding.

Therefore, the adhesion between the B / G grinding table and the wafer is improved, and even if grinding is performed so that the finished thickness of the wafer is smaller than in the past, defects due to wafer cracking and damage can be significantly reduced.

Specifically, if the plasma etching amount (depth) is 1 to 10 μm, the wafer finished thickness is 120 μm.
However, the effect of about 1% is obtained even if the wafer cracking defect rate is large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view for explaining the method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is a cross-sectional view for describing the method for manufacturing a semiconductor device according to the present invention.

FIG. 4 is a conceptual diagram illustrating a method for manufacturing a semiconductor device according to the present invention.

FIG. 5 is a cross-sectional view for explaining a conventional method for manufacturing a semiconductor device.

Claims (3)

[Claims] 2. A method of manufacturing a semiconductor device, comprising: forming a semiconductor element region; and grinding the back surface of the wafer to a desired finished thickness by providing a groove in a dicing street and performing the grinding. Method. 2. The method according to claim 1, wherein the groove is formed deeper than an impurity diffusion region of the semiconductor element by plasma etching. 3. The method for manufacturing a semiconductor device according to claim 2, wherein the depth of the groove is provided to be 1 μm or more and 10 μm or less.