JP7316730B2 - Workpiece processing method - Google Patents

Description

The present invention relates to a method of processing a semiconductor wafer having dividing lines set on its front surface and a metal film laminated on its back surface.

Conventionally, for example, as disclosed in Patent Document 1, for a semiconductor wafer having a metal film formed on the back surface, a cutting step of forming a cutting groove on the front surface with a cutting blade, and a protective film covering the front surface and the cutting groove. A processing method is known that includes a film forming step, a laser processing step of irradiating a laser beam onto a metal film to divide the wafer and the metal film, and a protective film removing step of removing the protective film by cleaning.

According to this processing method, the metal debris generated by irradiating the metal film with the laser beam adheres to the protective film and can be removed together with the protective film, thereby preventing the debris from remaining on the device side.

JP 2018-78162 A

However, it was confirmed that it is difficult to form a protective film on the inner wall surface of the cut groove, partly because the groove width of the cut groove is narrow and the protective agent does not sufficiently penetrate into the cut groove.

Here, it is conceivable that the use of a low-viscosity protective agent facilitates penetration of the protective agent into the cut grooves.

However, in the case of a protective agent with low viscosity, it is difficult to form a sufficiently thick protective film layer on the surface of the wafer, and the protective film dissolves or peels off at the edge of the cut groove, exposing the wafer surface. However, there is a risk that metal debris will adhere to the exposed portion.

If metal debris adheres to the exposed portion in this way, there is a risk of damaging the side surface of the chip (the inner wall surface of the cutting groove) or the device on the surface.

In view of the above problems, the present invention proposes a novel technique for protecting the side surface (the inner wall surface of the cut groove) and the surface of the chip with a protective film layer.

According to one aspect of the invention,
A method for processing a workpiece having a dividing line set on the front surface and a metal film laminated on the back surface,
a groove forming step of forming a groove not reaching the metal film along the dividing line in the surface of the workpiece;
a first protective film forming step of, after performing the groove forming step, forming a first protective film covering the surface of the workpiece and the inner wall surface of the groove with a first protective agent having a viscosity that penetrates into the groove; ,
a second protective film forming step of forming a second protective film covering at least the surface of the workpiece with a second protective agent after performing the first protective film forming step;
After performing the second protective film forming step, a laser beam having a wavelength that is absorptive to the workpiece is irradiated along the groove from the surface side of the workpiece to divide the metal film. and a machining step.

Further, according to one aspect of the present invention,
The viscosity of the second protective agent shall be higher than the viscosity of the first protective agent.

According to one aspect of the invention,
It is assumed that the first protective agent and the second protective agent are the same.

According to one aspect of the invention,
After performing the laser processing step, the method further includes a removing step of removing the first protective film and the second protective film.

According to the configuration of the present invention, the surface of the workpiece and the inner wall surface of the groove can be reliably protected by the double protective film, and the metal debris generated by laser processing can be prevented from the surface of the workpiece and the inner wall surface of the groove. can be prevented from adhering to

It is a figure which shows the semiconductor wafer as an example of the to-be-processed object processed by this invention. It is a figure explaining the example of the processing apparatus for implementing a surface side groove|channel formation step. (A) is a cross-sectional view of a workpiece after grooves are formed; (B) is a diagram explaining a surface hydrophilization step. FIG. 4 is a cross-sectional view of a workpiece covered with a first protective film; It is a partial side sectional view of a protective film formation apparatus. (A) is a cross-sectional view of a workpiece covered with a second protective film. (B) is a diagram illustrating a state in which a laser processed groove is formed by a laser processing step. It is a figure explaining a laser processing step. FIG. 4B is a cross-sectional view of the workpiece after the protective film removal step; (A) is a diagram showing an example of forming a double protective film with the same protective agent. (B) is a diagram showing an example in which laser-processed grooves are formed in (A).

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a semiconductor wafer as an example of a workpiece to be processed according to the present invention.

The surface 1a of the wafer 1 is partitioned by a plurality of dividing lines 3 (streets) that cross each other, and devices 5 such as ICs (Integrated Circuits) and LSIs (Large-Scale Integrated Circuits) are formed in each area. there is By dividing the wafer 1 along the dividing line 3, it is planned to singulate into individual device chips.

A metal film 21 made of copper (Cu), aluminum (Al), or the like is formed on the back surface 1 b of the wafer 1 . The metal film 21 is used, for example, as an electrode, a heat sink, or the like.

The back surface 1 b of the wafer 1 is adhered to the adhesive layer on the upper side of the tape 7 . A ring-shaped frame 9 is attached to the adhesive layer of the tape 7 so as to surround the wafer 1, and the wafer unit 11 is formed by integrating the wafer 1 and the frame 9 together.

The present invention can also be applied to wafers on which devices are not formed on the surface.

The following steps are performed using the above wafer 1 as a workpiece.
<Surface groove formation step>
As shown in FIGS. 2 and 3A, grooves 30 are formed in the front surface 1a of the wafer 1 along the lines 3 to be divided, and have a depth that does not reach the metal film 21. As shown in FIG.

In this embodiment, as shown in FIG. 2, the grooves 30 are formed by cutting along the planned division lines 3 with a cutting blade 66 that rotates at high speed. In addition to forming the grooves 30 (cut grooves) by cutting with the cutting blade 66, the grooves may be formed by irradiating a laser beam.

As shown in FIG. 3A, the device 5 is formed on the front surface 1a of the substrate 1k of the wafer 1, and the metal film 21 is formed on the back surface 1b of the substrate 1k of the wafer 1. is adhered to the tape 7.

As shown in FIG. 3A, the grooves 30 are formed in the thickness direction of the substrate 1k of the wafer 1 and are formed along the dividing lines 3, and the devices 5 are arranged between the grooves 30. It is designed to be

The thickness of the uncut portion of the substrate 1k at the bottom surface 30b of the groove 30 is not particularly limited, but it is preferable to leave the uncut portion of about 30 to 50 μm in consideration of handling in subsequent steps.

<Surface hydrophilization step>
Following the surface side groove forming step, as shown in FIG. 3(B), it is preferable to carry out surface hydrophilization treatment.
Specifically, the front surface 1a of the wafer 1 is irradiated with ultraviolet rays having wavelengths of 184 nm and 254 nm from the ultraviolet irradiator 46 simultaneously or sequentially. Ultraviolet rays with a wavelength of 184 nm decompose the waiting oxygen to form an ozone layer. The generated ozone is decomposed by ultraviolet rays with a wavelength of 254 nm to generate active oxygen. The generated active oxygen acts on the surface 1a of the workpiece 1 to improve hydrophilicity. At the same time, organic compounds such as oil adhering to the surface 1a also become H ₂ O, CO ₂ , NO, etc., and are volatilized and removed from the surface 1a of the wafer 1 .

As the ultraviolet irradiation body 46, for example, a low-pressure mercury lamp having two peaks at wavelengths of 184 nm and 254 nm, or an LED lamp having wavelengths of 184 nm and 254 nm, respectively, can be used. Moreover, the hydrophilization treatment may be performed by plasma irradiation instead of ultraviolet irradiation. A mixed gas of argon and water gas can be used as the plasma generating gas.

<First protective film forming step>
Next, as shown in FIGS. 4 and 5, a first protective film forming step is performed to form the first protective film 41 on the front surface 1a of the wafer 1. Next, as shown in FIGS.

In FIG. 4, the surface 1a of the wafer 1 and the surface of the device 5 are covered with the first protective film 41, and the inner wall surface 30a and the bottom surface 30b of the groove 30 are covered with the first protective film 41. shown to be

FIG. 5 is a partial side cross-sectional view of a protective film forming apparatus 50 for forming the first protective film 41. As shown in FIG.
The protective film forming apparatus 50 includes a spinner table mechanism 54 and a liquid receiving mechanism 56 arranged to surround the spinner table mechanism 54 .

The spinner table mechanism 54 includes a spinner table (holding table) 58 that sucks and holds the wafer 1, a support member 60 that supports the spinner table 58, an electric motor 62 that rotationally drives the spinner table 58 via the support member 60, is configured with

The spinner table 58 is provided with clamps 44. When the spinner table 58 is rotated, these clamps 44 swing due to centrifugal force to clamp and hold the annular frame 9 shown in FIG.

The liquid receiving mechanism 56 includes a liquid receiving container 56a and a cover member 56b attached to the support member 60. The protective film receives liquid such as cleaning liquid and drains the liquid through a discharge path (not shown). is configured to be discharged.

A first protective agent discharge nozzle 70 for discharging the first protective agent 40 is provided in the space surrounded by the liquid receiving container 56a. The first protective agent discharge nozzle 70 is formed at the tip of a substantially L-shaped arm 71 , and the other end of the arm 71 is swung by an electric motor 72 . The arm 71 is connected to a protective film supply source 75 through a protective film supply path 73 and an open/close control valve 74 .

Using the protective film forming apparatus 50 configured as described above, when the wafer 1 is rotated at a predetermined speed and the first protective agent 40 is discharged toward the center of the wafer 1, centrifugal force causes the first protective film to move radially. The protective agent 40 spreads and the entire surface 1a of the wafer 1 is coated with the first protective agent 40 (spin coating).

In addition, in the process of spreading the first protective agent 40, the first protective agent 40 enters the groove 30, and as shown in FIG. coated with

The first protective agent 40 for forming the first protective film 41 is, for example, a water-soluble liquid resin such as PVP (polyvinylpyrrolidone) or PVA (polyvinyl alcohol).

Here, the viscosity of the first protective agent 40 is preferably set to a value that allows it to reliably penetrate into the grooves 30. For example, a value between 1 cP and 20 cP can be selected. is 8 cP.

<Second protective film forming step>
Next, as shown in FIG. 6(A), a second protective film is formed to form a second protective film 42 as a second layer on the first protective agent 41 formed on the surface of the wafer. carry out the steps;

As shown in FIG. 5, the protective film forming apparatus 50 described above contains a second protective agent for forming the second protective film 42 (FIG. 6A) in addition to the first protective agent ejection nozzle 70. A second protective agent ejection nozzle 80 is provided for ejection.

The second protective agent discharge nozzle 80 is formed at the tip of a substantially L-shaped arm 81 , and the other end of the arm 81 is swung by an electric motor 82 . The arm 81 is connected to a protective film supply source 85 through a protective film supply path 83 and an open/close control valve 84 .

After completing the above-described first protective film forming step, the first protective agent discharge nozzle 70 is retracted to the standby position by rotating the arm 71 by the electric motor 72, and the arm 81 is rotated by the electric motor 82. , the second protective agent discharge nozzle 80 is positioned above the wafer 1 .

Then, when the wafer 1 is rotated at a predetermined speed and the second protective agent is discharged toward the center of the wafer 1, the second protective agent spreads radially due to the centrifugal force, as shown in FIG. 6(A). Then, the surface of the first protective film 41 is covered with the second protective film 42 .

The second protective agent for forming the second protective film 42 is, for example, a water-soluble liquid resin such as PVP (polyvinylpyrrolidone) or PVA (polyvinyl alcohol).

Here, the viscosity of the second protective agent for forming the second protective film 42 is preferably set higher than the viscosity of the first protective agent for forming the first protective film 41. For example, from 40 cP to A value between 80 cP can be chosen, one example being 60 cP.

By using the second protective agent having a high viscosity in forming the second protective film 42 in this manner, a protective film having a sufficient thickness can be formed on the surface of the device 5 .

In addition, since the viscosity of the second protective agent increases, the second protective agent does not enter the groove 30 as shown in FIG. 6(A). are already covered with the first protective film 41 and are in a protected state.

<Laser processing step>
FIG. 7 shows a laser processing unit 90 for carrying out the laser processing step, in which a laser beam is emitted from a condenser 92 along the groove 30. As shown in FIG.

As shown in FIG. 6A, a laser beam 94 is irradiated into the groove 30, and the substrate 1k of the wafer 1 remaining below the bottom surface 30b of the groove 30 and the metal film 21 absorb the laser beam 94. The laser-processed grooves 32 are formed by destroying the grooves. The focal position of the laser beam 94 is set at a position corresponding to the substrate 1k of the wafer 1 remaining below the bottom surface 30b of the groove 30 and the metal film 21. FIG.

As shown in FIG. 6B, the irradiation of the laser beam 94 also removes the second protective film 42 covering the groove 30 to open the groove 30 and form the opening 30m. At this time, there is concern that the protective film may be dissolved or peeled off at the edge portion 30n around the opening 30m, but since the second protective film 42 has a sufficient thickness, the wafer surface and devices are exposed and exposed It is possible to prevent metal debris from adhering to the part where the

Furthermore, even if the second protective film 42 is dissolved or peeled off, the wafer surface and devices can be protected by the first protective film 41 inside. In this way, it is possible to doubly protect the wafer surface and devices.

<Protective film removal step>
In addition to the first and second protective agent ejection nozzles 70 and 80, the protective film forming apparatus 50 shown in FIG. is ejected and the wafer 1 is rotated to remove the first and second protective films 41 and 42 covering the wafer 1 and the devices 5 .

As described above, as shown in FIG. 8, the wafer 1 in which the protective film is removed and the devices 5 are exposed can be formed. Then, using the substrate 1k and the laser-processed grooves 32 formed in the metal film 21 as division starting points, it becomes possible to singulate into chips by an expanding process or the like performed later.

In the above embodiment, as shown in FIG. 6A, the surface of the wafer 1 is covered with the first and second protective films 41 and 42 using protective agents having different viscosities. As shown in FIGS. 9A and 9B, the laser-processed groove 32 may be formed after the protective films 43, 43 of the same type are double coated.

In this case, the same protective agent is supplied to the surface of the wafer twice, and both the first protective agent and the second protective agent enter the grooves 30 . This makes it possible to cover the inner wall surface 30a and the bottom surface 30b of the groove 30 in a double manner.

The present invention can be implemented as described above.
That is, as shown in FIGS. 1 to 8,
A method for processing a workpiece (wafer 1) in which a dividing line 3 is set on the front surface 1a and a metal film 21 is laminated on the back surface 1b,
a groove forming step of forming grooves 30 that do not reach the metal film 21 along the dividing lines 3 on the surface 1a of the workpiece;
a first protective film forming step of forming a first protective film 41 covering the surface 1a of the workpiece and the inner wall surface of the groove 30 with a first protective agent having a viscosity that penetrates into the groove 30 after performing the groove forming step; ,
After performing the first protective film forming step, a second protective film forming step of forming a second protective film 42 covering at least the surface 1a of the workpiece with a second protective agent;
After performing the second protective film forming step, a laser beam 94 having a wavelength that is absorptive to the workpiece is irradiated along the groove 30 from the surface 1a side of the workpiece to divide the metal film 21. and a machining step.

According to the above processing method, the surface of the workpiece and the inner wall surface of the groove can be reliably protected with a double protective film, and the metal debris generated by laser processing can be prevented from the surface of the workpiece and the inner wall surface of the groove. can be prevented from adhering to

Also, the viscosity of the second protective agent is assumed to be higher than that of the first protective agent.

As a result, as shown in FIGS. 6A and 6B, the thick second protective film 42 can be formed by the highly viscous second protective agent. and the device 5 can be reliably protected.

Also, the first protective agent and the second protective agent are the same.

Thereby, as shown in FIGS. 9(A) and 9(B), the protective films 43, 43 of the same kind can be coated in double. Here, by setting the viscosity of the protective film to be used so that it easily penetrates into the groove 30, a double protective film can be reliably formed even in the groove 30, and the inner wall surface 30a of the groove 30 can be formed. can be reliably protected.

Moreover, after performing the laser processing step, the method further includes a removing step of removing the first protective film 41 and the second protective film 42 .

This makes it possible to remove the protective film and perform a subsequent division step or the like.

1 wafer 1a front surface 1b back surface 1k substrate 3 division line 5 device 21 metal film 30 groove 30a inner wall surface 30b bottom surface 30m opening 30n edge portion 32 laser processing groove 41 first protective film 42 second protective film 50 protective film forming device 54 Spinner table mechanism 70 First protective agent discharge nozzle 80 Second protective agent discharge nozzle 90 Laser processing unit 92 Concentrator 94 Laser beam

Claims (4)

A method for processing a workpiece having a dividing line set on the front surface and a metal film laminated on the back surface,
a groove forming step of forming a groove not reaching the metal film along the dividing line in the surface of the workpiece;
a first protective film forming step of, after performing the groove forming step, forming a first protective film covering the surface of the workpiece and the inner wall surface of the groove with a first protective agent having a viscosity that penetrates into the groove; ,
a second protective film forming step of forming a second protective film covering at least the surface of the workpiece with a second protective agent after performing the first protective film forming step;
After performing the second protective film forming step, a laser beam having a wavelength that is absorptive to the workpiece is irradiated along the groove from the surface side of the workpiece to divide the metal film. A method of processing a workpiece, comprising: a processing step; the viscosity of the second protective agent is higher than the viscosity of the first protective agent;
2. The method of processing a workpiece according to claim 1, wherein: the first protective agent and the second protective agent are the same;
2. The method of processing a workpiece according to claim 1, wherein: further comprising a removing step of removing the first protective film and the second protective film after performing the laser processing step;
4. The method for processing a workpiece according to any one of claims 1 to 3, characterized in that: