JP2021197482A - Processing method of workpiece, method for manufacturing workpiece with protective film, and protective film agent for laser dicing - Google Patents

Abstract

To provide a method for manufacturing a workpiece with a protective film which reduces the burning of a device during laser processing, and a protective film agent for laser dicing to be applied to the workpiece.SOLUTION: A processing method for processing a workpiece 11 with a laser beam includes a protective film coating step of applying, to one surface (front surface 11a) of a workpiece, a protective film agent 25 for laser dicing which is composed of a solution in which a water-soluble resin, an organic solvent, and a light absorber are at least dissolved in a protective film forming device 30, and in which the light absorber includes a benzophenone derivative having two or more hydroxyl groups as a substituent and having no substituent other than the hydroxyl group, and covering one side with a protective film 27 having thickness of 3.8 μm or more, and a machined groove forming step of irradiating the entire surface along a scheduled division line 13 via the protective film 27 with a laser beam having a wavelength absorbed by the workpiece from above the workpiece to form a laser machined groove on the workpiece in a laser processing device.SELECTED DRAWING: Figure 5

Description

The present invention is a method for processing a workpiece in which a protective film agent for laser dicing is applied on one surface of the workpiece and then the one surface is irradiated with a laser beam to form a laser processing groove. The present invention relates to a method for manufacturing a work piece with a protective film coated with a protective film agent for laser dicing, and a protective film agent for laser dicing applied to the work piece.

Electronic devices such as mobile phones and personal computers are equipped with device chips equipped with devices such as electronic circuits. In order to manufacture a device chip, for example, it is manufactured by dividing a workpiece such as a silicon wafer on which a device is formed.

More specifically, a plurality of scheduled division lines are set on the surface of the workpiece, and devices such as ICs (Integrated Circuits) are formed in each region partitioned by the plurality of scheduled division lines. Device chips are manufactured by dividing the workpiece along each scheduled division line.

For example, a laser processing device is used to divide the workpiece. The laser processing apparatus includes a chuck table that sucks and holds the workpiece, and a laser beam irradiation unit arranged above the chuck table. When processing a work piece with a laser processing device, first, the back surface side of the work piece is sucked and held by a chuck table.

Next, the laser beam irradiation unit irradiates the surface side of the workpiece with a laser beam having a wavelength absorbed by the workpiece. The work piece is ablated by irradiating the laser beam along the planned division line. However, during laser machining, the melt of the work piece may become debris and scatter and adhere to the surface of the work piece, degrading the quality of the device chip after division.

Therefore, by forming a protective film made of a water-soluble resin, a light absorber, etc. on the surface of the workpiece before laser processing the workpiece, debris directly adheres to the surface of the workpiece. It is known to prevent (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-140311

However, there is a problem that the device formed on the surface side of the workpiece is burnt due to the laser beam being scattered by the debris or the like scattered by the laser processing. In particular, when the device is a solid-state image sensor such as a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, if the device is burnt, the performance of the device is greatly affected.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce burning of the device during laser processing.

According to one aspect of the present invention, it is a method for processing a work piece by processing a work piece with a laser beam, which comprises a solution in which a water-soluble resin, an organic solvent, and a light absorber are at least dissolved. The light absorber contains a benzophenone derivative having two or more hydroxyl groups as a substituent and having no substituent other than the hydroxyl group, and a protective film agent for laser dicing is applied on one surface of the workpiece. A protective film coating step of coating the one side with a protective film having a thickness of 3.8 μm or more, and a laser beam having a wavelength absorbed by the workpiece from above the workpiece. Provided is a method for processing a work piece, comprising a work groove forming step of irradiating the one surface through the protective film to form a laser machined groove on the work piece.

Preferably, in the protective film coating step, the protective film agent for laser dicing having an absorbance at a wavelength of 355 nm (absorbance converted into a 200-fold diluted solution) of 0.25 or more per 1 cm of optical path length is applied to the workpiece. Apply on one side.

According to another aspect of the present invention, the method for producing a workpiece with a protective film comprises a solution in which a water-soluble resin, an organic solvent, and a light absorber are at least dissolved, and the light absorber is composed of a solution. , A preparatory step for preparing a protective film agent for laser dying containing a benzophenone derivative having two or more hydroxyl groups as a substituent and having no substituent other than the hydroxyl group, and the protective film agent for laser dying. Provided is a method for producing a work piece with a protective film, comprising a protective film coating step of coating one side of the work piece with a protective film having a thickness of 3.8 μm or more. To.

Preferably, in the protective film coating step, the protective film agent for laser dicing having an absorbance at a wavelength of 355 nm (absorbance converted into a 200-fold diluted solution) of 0.25 or more per 1 cm of optical path length is applied to the workpiece. Apply on one side.

According to still another aspect of the present invention, it is a protective film agent for laser dicing applied to a work piece by irradiating it with a laser beam to process the work piece, and is a water-soluble resin and an organic solvent. And a solution in which the light absorber is at least dissolved, and the light absorber contains a benzophenone derivative having two or more hydroxyl groups as a substituent and having no substituent other than the hydroxyl group. A protective film agent for laser dying is provided.

Preferably, the absorbance at a wavelength of 355 nm (absorbance converted into a 200-fold diluted solution) is 0.25 or more per 1 cm of the optical path length.

The protective film agent for laser dying according to one aspect of the present invention is composed of a water-soluble resin, an organic solvent, and a solution in which at least a light absorber is dissolved, and the light absorber is composed of two or more hydroxyl groups as substituents. It contains a benzophenone derivative having a group and having no substituent other than a hydroxyl group. By using such a light absorber, the absorbance of the protective film agent for laser dicing at a wavelength of 355 nm can be increased as compared with a conventional light absorber such as ferulic acid. Therefore, it is possible to reduce the burning of the device during laser processing.

Further, a protective film for laser dicing containing the light absorber is applied on one surface of the workpiece, and the one surface is covered with a protective film having a thickness of 3.8 μm or more, whereby the protective film is 3 It is possible to reduce the burning of the device during laser processing as compared with the case where the thickness is less than 8.8 μm.

It is the first graph which shows the number of places where the burn occurred with respect to the absorbance and the film thickness. 2 is a second graph showing the number of burned areas with respect to absorbance and film thickness. FIG. 3A is a perspective view of the workpiece, and FIG. 3B is a partially enlarged cross-sectional view of the workpiece. It is a perspective view of a frame unit. FIG. 5A is a diagram showing a protective film coating process, and FIG. 5B is a partially enlarged cross-sectional view of a workpiece with a protective film. It is a perspective view of the workpiece with a protective film. It is a figure which shows the machined groove formation process. It is a flow chart of the processing method of a work piece.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a protective film agent for laser dicing (hereinafter referred to as a protective film agent) according to the present embodiment will be described. The protective film agent is composed of a solution in which a water-soluble resin, an organic solvent, and a light absorber are at least dissolved.

Examples of the water-soluble resin include polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose (ethyl cellulose). hydroxypropyl cellulose, polyacrylic acid, poly-N-vinylacetamide, polystyrene sulfonic acid, special nylon, phenolic resin, methylolmelamine Resin), polyglycerin, and their graft polymers (eg, polyvinyl alcohol grafted with polyvinylpyrrolidone). One of the above-mentioned materials may be used alone, or two or more kinds of materials may be used in combination.

Further, a water-soluble resin that responds to an external stimulus (for example, temperature) may be used. By using such a water-soluble resin, it is possible to control the viscosity such that the viscosity is high when the temperature is high and the viscosity is low when the temperature is low. Therefore, for example, after forming a protective film containing a water-soluble resin on a work piece at a high temperature, laser processing is performed on the protective film and the work piece, and after laser processing, the temperature of the protective film is adjusted. By lowering the temperature and giving the protective film fluidity, the protective film can flow into the machined groove.

Commercially available polyvinylpyrrolidone (PVP) has different viscosities depending on the molecular weight, and is K-17, K-25, K-30, K-40, K-50, K-60, K-80, K-85, K. They are grouped by K values such as -90, K-120, ... K-300. The K value has a viscosity characteristic value that correlates with the molecular weight, and is calculated by applying the relative viscosity value (25 ° C.) measured by a capillary viscometer to the fikencher's formula.

In order to produce a protective film agent that can cover one side of the work piece with a protective film having a thickness of 3.8 μm or more using PVP, when used alone, K-40 or more and K-80 or less. Is preferable, and K-50 or more and K-60 or less are more preferable.

When PVPs having a small K value such as K-17, K-25, and K-30 are used, a relatively large amount of PVP is required. In addition, it has been confirmed by the applicant's experiment in this case that discoloration of the protective film agent occurs when K-30 is used.

On the other hand, when PVP having a large K value such as K-80, K-85, K-90 is used, the viscosity of the protective film agent becomes high and it becomes difficult to feed the liquid. In order to realize smooth liquid feeding of the protective film agent, the viscosity (mPa · s) at 25 ° C. is preferably 400 or less, and more preferably 300 or less.

Therefore, in consideration of various points such as the amount used, discoloration, liquid feeding, etc., it is used alone to prepare a protective film agent capable of covering one side of the work piece with a protective film having a thickness of 3.8 μm or more. In the above case, it is preferable to use PVP of K-40 or more and K-80 or less, and more preferably K-50 or more and K-60 or less.

As long as there is no problem in the amount used, discoloration, liquid feeding, etc., two or more types of PVPs having different K values may be used in combination. For example, a combination of a large amount of K-25 and a small amount of K-90 or a combination of a large amount of K-50 and a small amount of K-90 may be used.

Further, some commercially available polyvinyl alcohols (PVA) have different degrees of polymerization, such as 300, 500, 1700, 2000, ... 3000. The higher the degree of polymerization, the higher the viscosity of the protective film agent. Therefore, in order to prepare a protective film agent capable of covering one side of the work piece with a protective film having a thickness of 3.8 μm or more in consideration of liquid feedability, the degree of polymerization of PVA is 300 or more and 500 or less. It is preferable, and about 300 is particularly preferable.

In addition, commercially available PVA has a degree of saponification such as complete saponification (98 mol% or more), intermediate saponification (92 mol% or more and 97 mol% or less), and partial saponification (70 mol% or more and 89 mol% or less). The PVA preferably has a saponification degree of 89 mol% or less, and more preferably a saponification degree of 82 mol% or less, from the viewpoints of solubility, stability of the protective film agent during storage, and the like.

The organic solvent has a function of dissolving a substance such as a light absorber. Examples of the organic solvent include alcohols, esters, alkylene glycol monoalkyl ethers, alkylene glycols, and alkylene glycol monoalkyl ether acetates. As the alkylene glycol monoalkyl ether, propylene glycol monomethyl ether is used, but propylene glycol monomethyl ether (PGME) is preferable. As the organic solvent, only one of these may be used, or two or more of these (for example, PGME, isopropyl alcohol, etc.) may be used in combination.

In addition, the organic solvent can reduce the surface tension of the protective film agent, and has a function of reducing coating unevenness when the protective film agent is spin-coated on a work piece, an antiseptic function of the protective film agent, and the like. Have. The amount used is not particularly limited, but in consideration of safety, resistance of the adhesive layer of the dicing tape, and the like, 20 wt% or less of the weight of the protective film agent is preferable, and 15 wt% or less is more preferable.

The protective film agent contains pure water. There is no particular problem even if tap water is used, but considering the ion exchange treatment after mixing, it is preferable to use pure water.

Further, an additive may be mixed in the protective film agent. As the additive, for example, ascorbic acid, trimethylolpropane (TMP) and the like are used. Ascorbic acid has a function of improving the color stability of ferulic acid.

TMP has a relatively high solubility in water, and even if it is dissolved in a large amount, it does not easily affect the physical properties such as the viscosity of the protective film agent. Further, TMP has functions such as improvement of washability of the protective film, suppression of carbonization of the protective film during laser ablation, and improvement of the film thickness of the protective film.

By using TMP, which is a solid plasticizer, the protective film can be formed by spin-coating the protective film on the work piece, as compared to the case where glycerin, which is a liquid plasticizer, is used. Can be thick and hard. If a predetermined amount of TMP is used, glycerin or the like may be further added as an additive.

Next, the light absorber will be described. The light absorbers are dihydroxybenzophenone (eg, 2,2'-dihydroxybenzophenone (2,2'-Dihydroxybenzophenone), 2,4-dihydroxybenzophenone (2,4-Dihydroxybenzophenone), 2,4'-dihydroxybenzophenone (2, 4'-Dihydroxybenzophenone), 3,4-dihydroxybenzophenone (3,4-Dihydroxybenzophenone), 4,4'-dihydroxybenzophenone (4,4'-Dihydroxybenzophenone), trihydroxybenzophenone (eg, 2,3,4-tri) Hydroxybenzophenone (2,3,4-Trihydroxybenzophenone), 2,4,4'-Trihydroxybenzophenone (2,4,4'-Trihydroxybenzophenone), 2,4,6-Trihydroxybenzophenone (2,4,6-Trihydroxybenzophenone) )), Tetrahydroxybenzophenone (eg, 2,2', 4,4'-Tetrahydroxybenzophenone (2,2', 4,4'-Tetrahydroxybenzophenone), 2,3,4'-Tetrahydroxybenzophenone (2) , 3,4,4'-Tetrahydroxybenzophenone)), pentahydroxybenzophenone (eg, 2,2', 3,4,4'-pentahydroxybenzophenone (2,2', 3,4,4'-Tetrahydroxybenzophenone)), And as a substituent such as hexahydroxybenzophenone (for example, 2,3,3', 4,4', 5'-hexahydroxybenzophenone (2,3,3', 4,4', 5-Hexahydroxybenzophenone)). It is a benzophenone derivative having two or more hydroxyl groups and having no substituent other than the hydroxyl group.

The solubility in pure water is 9.1 g / L for 2,4-dihydroxybenzophenone, 13.2 g / L for 2,3,4-trihydroxybenzophenone, and 3 for 2,4,6-trihydroxybenzophenone. It is .1 g / L, 2,2', 4,4'-tetrahydroxybenzophenone is 8.8 g / L, and 2,3,4,4'-tetrahydroxybenzophenone is 15.1 g / L. On the other hand, ferulic acid is 0.7 g / L.

Some benzophenone derivatives have a substituent other than a hydroxyl group, and some have a hydroxyl group and other substituents, but they have two or more hydroxyl groups as substituents and have a substituent. Compared to those having no substituent other than the hydroxyl group (that is, those having only two or more hydroxyl groups as substituents), the absorption spectrum shifts to the shorter wavelength side, and the protective film agent is used at a wavelength of 355 nm. There are problems such as difficulty in obtaining high absorbance, the need to use a large amount of light absorber as a protective film agent in order to obtain high absorbance, and low solubility in water. ..

As the light absorber, a benzophenone derivative having only two or more hydroxyl groups as a substituent may be used alone, but the benzophenone derivative alone is sufficient for detecting the coating state of the protective film by fluorescence. It is difficult to obtain fluorescence intensity. Therefore, in order to detect the coating state of the protective film by fluorescence, caffeic acid, chlorogenic acid, etc., which emit strong fluorescence by ultraviolet irradiation, may be mixed with a benzophenone derivative and used.

The applicant of this case uses ferulic acid, which is conventionally known as a light absorber in a protective film agent, when a benzophenone derivative having only two or more hydroxyl groups as a substituent is used as a light absorber of the protective film agent. It has been found that the absorbance at a wavelength of 355 nm can be increased as compared with the case of using (ferulic acid).

This is because the benzophenone derivative having only two or more hydroxyl groups as a substituent has an absorption spectrum on the long wavelength side and has high solubility in water as compared with ferulic acid, so that it can be used in a large amount. Because it is. As described above, the applicant of the present case has found that the absorbance at a wavelength of 355 nm can be increased, which is effective in reducing the burning of the device.

(Manufacturing method of protective film agent)
The method for producing the protective film agent is not particularly limited, but for example, after preparing a solution in which a light absorber is dissolved in an organic solvent, the solution is mixed with a separately prepared water-soluble resin and an aqueous solution in which an additive is dissolved. do. The mixing may be carried out at room temperature or while heating. Dissolution and mixing should be performed with stirring.

(Treatment of protective film agent)
After mixing, it is preferable to carry out an ion exchange treatment. Although the reason is unknown, it has been confirmed by the experiment of the applicant of this case that the ion exchange treatment is superior in the color stability of the liquid after 6 months. Further, it is preferable to pass through a filtration filter after the ion exchange treatment.

(PH of protective film agent)
By the ion exchange treatment, the pH of the protective film agent becomes 4 or less. From the viewpoint of antiseptic, the pH is preferably 4 or less, but the pH may be 4 or more by using a pH adjusting agent such as triethanolamine.

Table 1 below shows the composition of 100 g of the protective film, the viscosity at 25 ° C., the conditions for applying the protective film to the workpiece, and the thickness of the protective film formed on the workpiece. (Experimental Example 1 to Experimental Example 3). Similarly, Table 2 shows the composition of 100 g of the protective film agent, the viscosity at 25 ° C., the protective film agent, the application conditions of the protective film agent, and the thickness of the protective film (experiment from Experimental Example 4). Example 7).

In Tables 1 and 2, FA is ferulic acid, DHBP is 2,4-dihydroxybenzophenone, and THBP is 2,2', 4,4'-tetrahydroxybenzophenone. Also, AA is ascorbic acid. As the PVA, one having a degree of polymerization of 300 and a degree of saponification of 78.5 mol% or more and 81.5 mol% or less was used.

(Experimental Procedure) In each experimental example, a frame unit was first formed by attaching the back surface side of a rectangular plate-shaped workpiece having a length of 23 mm and a width of 35 mm to a dicing tape attached to an annular frame. Next, the side of the dicing tape opposite to the workpiece was held by the spinner table, and the spinner table was rotated at the rotation speed shown in the column of application conditions. Then, after supplying a liquid protective film agent at a predetermined value of 1.0 ml / sec or more and 2.0 ml / sec or less on the surface of the rotating workpiece, the protective film is applied to the entire surface side by using centrifugal force. The agent was applied, and a protective film having the thickness shown in the column of film thickness was formed on the surface of the workpiece.

After the protective film was formed, the surface side of the workpiece was irradiated with a laser beam (5 lines at approximately equal intervals in the vertical direction and 4 lines at approximately equal intervals in the horizontal direction). A plurality of scheduled division lines are set on the surface of the workpiece in a grid pattern, and a solid-state image sensor (device) is formed in each of the rectangular regions surrounded by the scheduled division lines.

A laser machined groove was formed by irradiating a laser beam along each scheduled division line. As the laser beam, a pulsed laser beam having a wavelength of 355 nm, a repetition frequency of a predetermined value in the range of 200 kHz to 1000 kHz, and a pulse width of a predetermined value in the range of 3 ps to 30 ps was used (ps means picosecond). ).

The spot diameter of the focused spot of the laser beam on the surface of the workpiece was set to a predetermined length of 2 μm to 5 μm. Further, the peak output of the laser beam was set to a predetermined value of 1.0 W to 5.0 W, and the machining feed rate was set to a predetermined value in the range of 200 mm / sec to 600 mm / sec.

After forming the machined grooves along all the planned division lines, the number of burns generated on the entire surface side of the work piece was counted using a microscope. FIG. 1 is a first graph showing the number of burned areas with respect to absorbance and film thickness. The vertical axis is the absorbance and the horizontal axis is the film thickness (μm).

(Absorbance at 355 nm) An ultraviolet-visible spectrophotometer (UV-2700, manufactured by Shimadzu Corporation) was used for the measurement of the absorbance at 355 nm. In the measurement, first, the protective film agent shown in each experimental example was diluted 200-fold with pure water, and the diluted solutions were enclosed in quartz prismatic cells, and the absorption spectrum was measured. The optical path length was 1 cm. In this way, the absorbance at a wavelength of 355 nm per 1 cm of optical path length of a 200-fold diluted solution of each protective film agent was measured.

(Film thickness) In Experimental Examples 1 to 3, the film thickness of the protective film changed from 1.0 μm to 2.0 μm. On the other hand, as shown in Experimental Example 4, by increasing the amount of PVA, the film thickness could be doubled as compared with Experimental Example 2 even when applied under the same conditions as in Experimental Example 2. Further, by combining PVA having a degree of polymerization of 300 and TMP, the viscosity at 25 ° C. was 400 mPa · s or less even if the amount of PVA was increased, and smooth liquid feeding was possible.

By the way, in Experimental Example 5, Experimental Example 6 and Experimental Example 7, the number of rotations of the spinner table per unit time was gradually increased, and the protective film agent was continuously applied in three stages. That is, after applying for the first time at the first rotation speed, applying for the second time at the second rotation speed larger than the first rotation speed, and further applying for the second time at the second rotation speed, the second rotation speed is larger than the second rotation speed. It was applied only for the third time at a rotation speed of 3. As a result, the film thickness could be increased as compared with Experimental Example 1 to Experimental Example 4.

As shown in FIG. 1, in Experimental Example 1 in which the film thickness of the protective film is 1.0 μm and the absorbance of the protective film agent is 0.19, the number of burns (that is, the total number of burn marks generated on all devices) is 50. That's all. Further, in Experimental Example 2 having a film thickness of 2.0 μm and an absorbance of 0.25, the number of burns was 50 or more.

As shown in Experimental Examples 2 and 5, FA can be dissolved up to about 1.0 g in the configuration of 100 g of the protective film agent, but if FA exceeds 0.4 g, color stability and the like deteriorate. , 0.4 g or more is not preferable. Therefore, considering the solubility of FA and the color stability of the protective film agent, when FA is used as the light absorber, the absorbance at a wavelength of 355 nm per 1 cm of the optical path length of the 200-fold diluted solution should be 0.25 or more. Have difficulty.

In Experimental Example 3 having a film thickness of 2.0 μm and an absorbance of 0.19, the number of burns was 30 or more. On the other hand, in Experimental Example 4 having a film thickness of 3.8 μm and an absorbance of 0.82, the number of burns was 7.

In Experimental Example 5 having a film thickness of 6.8 μm and an absorbance of 0.25, the number of burns was 10. In Experimental Example 6 having a film thickness of 6.8 μm and an absorbance of 0.82, the number of burns was changed from 0 to 1.

Further, in Experimental Example 7 having a film thickness of 6.8 μm and an absorbance of 0.91, the number of burns was changed from 0 to 1. It should be noted that the fact that the number of burns is 0 to 1 means that there is only one delicate trace of whether or not it can be said to be burnt, and in this case, it can be said that the work piece is not burnt. ..

As can be seen from the comparison between Experimental Examples 1, 2, 3 and 5 (light absorber is FA) and Experimental Examples 4, 6 and 7 (light absorber is DHBP or THBP), two or more substituents are used. By using a light absorber containing a benzophenone derivative having only a hydroxyl group, the absorbance of the protective film agent at a wavelength of 355 nm can be increased as compared with a conventional light absorber such as ferulic acid.

There is no experimental result in which the absorbance per 1 cm of the optical path length is 0.25 using a protective film agent containing DHBP or THBP. However, considering that there is a correlation between the concentration and the absorbance, when the absorbance is 0.25 and the film thickness is 6.8 μm by adjusting the concentration of DHBP or THBP, it is the same as Experimental Example 5. It can be estimated that equivalent or better results can be obtained.

That is, when a light absorber containing a benzophenone derivative having only two or more hydroxyl groups as a substituent is used and the absorbance per 1 cm of the optical path length of the protective film agent is set to 0.25 or more, the burn that occurs in the device The number of can be reduced. Further, when the absorbance per 1 cm of the optical path length of the protective film agent is 0.82 or more or 0.91 or more, the number of burns can be further reduced.

Comparing Experimental Examples 1 to 3 with Experimental Examples 4 to 7, it can be said that the number of burns can be reduced by setting the thickness of the protective film to 3.8 μm or more. In particular, when Experimental Example 5 and Experimental Examples 4, 6 and 7 are compared, a light absorber containing a benzophenone derivative having only two or more hydroxyl groups as a substituent is used, and the thickness of the protective film is determined. It is more effective to make it 3.8 μm or more.

As described above, a protective film agent containing a benzophenone derivative having only two or more hydroxyl groups as a substituent is applied on one surface of the workpiece, and the one side is covered with a protective film having a thickness of 3.8 μm or more. By coating, it is possible to reduce the burning of the device during laser processing as compared with the case where the protective film is less than 3.8 μm.

Further, using a benzophenone derivative having only two or more hydroxyl groups as a substituent as a light absorber, the absorbance per 1 cm of the optical path length of the protective film agent is 0.82 or more, and the thickness of the protective film is 6. By setting the thickness to 8 μm or more, the burning of the device can be almost eliminated (see Experimental Examples 6 and 7). If the protective film is too thick, laser processing itself becomes difficult, so the thickness of the protective film is preferably 15 μm or less.

Table 3 below shows the composition of 100 g of the protective film, the viscosity at 25 ° C., the conditions for applying the protective film to the workpiece, and the thickness of the protective film formed on the workpiece. (Experimental Examples 8 to 10). Similarly, Table 4 shows the composition of 100 g of the protective film agent, the viscosity at 25 ° C., the application conditions of the protective film agent, and the thickness of the protective film (Experimental Examples 11 to 13).

(Experimental Procedure) In each of the experimental examples shown in Tables 3 and 4, first, a rectangular plate-shaped workpiece having a length of 22 mm and a width of 32 mm was used to form a protective film in the same manner as in the experimental procedures of Tables 1 and 2. It was formed and then laser machined (7 lines at approximately equal intervals in the vertical direction and 4 lines at approximately equal intervals in the horizontal direction). Also in the work piece, a solid-state image sensor (device) is formed in each of the rectangular regions surrounded by the planned division lines.

After forming the machined grooves along all the planned division lines, the number of burns generated on the entire surface side of the work piece was counted using a microscope. FIG. 2 is a second graph showing the number of burned areas with respect to absorbance and film thickness. The vertical axis is the absorbance and the horizontal axis is the film thickness (μm).

(Asorbance) The absorbance was measured under the same conditions as in Experimental Examples 1 to 7. (Film thickness) In Experimental Examples 8 to 10, the film thickness of the protective film was 1.0 μm. On the other hand, as shown in Experimental Example 11, by dissolving PVP K-50 in the protective film agent, the viscosity is not significantly improved as compared with the case of using PVP K-90, and the conditions are the same. The film thickness could be quadrupled as compared with the coated Experimental Example 8.

By the way, in Experimental Example 12 and Experimental Example 13, the number of revolutions per unit time of the spinner table is gradually increased, and the protective film agent is continuously applied in three stages as compared with Experimental Example 11. , The film thickness could be further increased.

As shown in FIG. 2, in Experimental Example 8 in which the film thickness of the protective film is 1.0 μm and the absorbance of the protective film agent is 0.19, the number of burns (that is, the total number of burn marks on the workpiece) is 252. It became. Further, in Experimental Example 9 having a film thickness of 1.0 μm and an absorbance of 0.43, the number of burns was 213.

In Experimental Example 10 having a film thickness of 1.0 μm and an absorbance of 0.85, the number of burns was 152. On the other hand, in Experimental Example 11 having a film thickness of 4.0 μm and an absorbance of 0.98, the number of burns was 67.

In Experimental Example 12 having a film thickness of 5.5 μm and an absorbance of 0.98, the number of burns was 40, and in Experimental Example 13 having a film thickness of 7.0 μm and an absorbance of 0.98, the number of burns was 0 to 1. It became an individual.

As can be seen from the comparison between Experimental Example 8 (light absorber is FA) and Experimental Examples 9 to 13 (light absorber is THBP), light containing a benzophenone derivative having only two or more hydroxyl groups as a substituent. It can be said that by using an absorbent, the absorbance of the protective film agent at a wavelength of 355 nm can be increased as compared with a conventional light absorber such as ferulic acid.

As described above, in Experimental Examples 8 to 13, the absorbance per 1 cm of the optical path length of the protective film agent was set to 0.43 or more by using a light absorber containing a benzophenone derivative having only two or more hydroxyl groups as a substituent. In that case, it was confirmed that the number of burns generated in the device could be reduced. Further, when the absorbance per 1 cm of the optical path length of the protective film agent is 0.85 or more or 0.98 or more, the number of burns can be further reduced.

Comparing Experimental Examples 8 to 10 with Experimental Examples 11 to 13, the thickness of the protective film is set to 4.0 μm or more, more preferably 5.5 μm or more, and further preferably 7.0 μm or more. It can be said that the number of burns can be reduced.

Further, using a benzophenone derivative having only two or more hydroxyl groups as a substituent as a light absorber, the absorbance per 1 cm of the optical path length of the protective film agent is 0.98 or more, and the thickness of the protective film is 7.0 μm. By doing so, it is possible to almost eliminate the burning of the device (see Experimental Example 13).

Next, a method of processing the workpiece 11 using the protective film agent will be described. First, the shape of the workpiece 11 will be described. FIG. 3A is a perspective view of the workpiece 11. The workpiece 11 has a substantially disk shape.

The surface (one surface) 11a side of the workpiece 11 is partitioned by a plurality of scheduled division lines (streets) 13 that intersect each other so as to be orthogonal to each other, and each of the partitioned regions is divided into devices such as a solid-state image sensor. 15 is provided. FIG. 3B is an enlarged cross-sectional view of a part of the workpiece 11.

The workpiece 11 has a wafer 21 mainly made of silicon (Si). A functional region that is a part of the functional element is formed on one surface side of the wafer 21 (corresponding to the surface 11a side of the workpiece 11).

A laminate 23 made of an inorganic compound or the like is formed on the functional region. The functional region of the laminate 23 and the wafer 21 constitutes a functional element, and the above-mentioned device 15 is composed of a plurality of functional elements. As shown in FIG. 3B, the portion of the device 15 is a convex portion protruding upward from the portion of the scheduled division line 13.

Next, an example of a processing method of the workpiece 11 for processing the workpiece 11 with a laser beam will be described. Note that FIG. 8 is a flow chart of a processing method for the workpiece 11. First, the protective film agent 25 (see FIG. 5A) is prepared (preparation step S10).

As described above, the protective film agent 25 contains a benzophenone derivative having only two or more hydroxyl groups as a substituent, and the absorbance at a wavelength of 355 nm (absorbance converted to a 200-fold diluted solution) is 0.25 per 1 cm of optical path length. That is all. The absorbance is more preferably 0.82 or more, 0.91 or more, or 0.98 or more per 1 cm of the optical path length.

After the preparation step S10, the frame unit 31 is formed (frame unit forming step S20). The frame unit forming step S20 may be performed before the preparation step S10. FIG. 4 is a perspective view of the frame unit 31.

The frame unit 31 has a metal annular frame 17. The annular frame 17 has an opening with a diameter larger than that of the workpiece 11. The workpiece 11 is arranged inside the opening of the annular frame 17, and is integrated with the annular frame 17 via the dicing tape 19.

The dicing tape 19 is, for example, a laminated body composed of a base material layer and an adhesive layer. The base material layer is formed of, for example, a polyolefin resin having a thickness of 5 μm or more and 200 μm or less. Further, the adhesive layer is formed of, for example, an ultraviolet curable resin.

In the frame unit forming step S20, for example, the front surface 11a side of the workpiece 11 and one surface of the annular frame 17 are placed on a flat table, and the back surface 11b side of the workpiece 11 and the annular frame 17 are added. A rectangular dicing tape 19 is attached to the surface.

Then, the dicing tape 19 is cut into a circle with a predetermined diameter equal to or greater than the inner diameter of the annular frame 17 and equal to or less than the outer diameter. As a result, the frame unit 31 is formed. After the frame unit forming step S20, the protective film coating step S30 is performed.

FIG. 5A is a diagram showing a protective film coating step S30. In FIG. 5A, the annular frame 17 and the dicing tape 19 are omitted. In the protective film coating step S30, for example, the protective film forming apparatus 30 is used.

The protective film forming apparatus 30 has a spinner table 32 that sucks and holds the back surface 11b side via the dicing tape 19. The spinner table 32 is connected to a rotation drive source (not shown) such as a motor, and rotates about a straight line substantially parallel to the vertical direction as a rotation axis.

A disk-shaped porous plate (not shown) is provided on the upper surface side of the spinner table 32. The porous plate is made of a porous member and is connected to a suction source (not shown) such as an ejector. When the suction source is operated, the surface of the porous plate functions as a holding surface for holding the workpiece 11.

Above the spinner table 32, a nozzle 34 for injecting a liquid protective film agent 25 toward the holding surface is arranged. The nozzle 34 is connected to a source (not shown) of the protective film agent 25 via a flow path (not shown).

In the protective film coating step S30, first, the workpiece 11 is placed on the spinner table 32 so that the back surface 11b side faces downward. Next, the back surface 11b side is sucked and held by the spinner table 32. After that, the rotation drive source is operated to rotate the spinner table 32 at a predetermined rotation speed.

In this state, the liquid protective film agent 25 is applied to the surface 11a of the workpiece 11 from the nozzle 34. The protective film agent 25 spreads uniformly on the surface 11a due to centrifugal force. After that, the supply of the protective film agent 25 is stopped, and the protective film agent 25 is dried. As a result, the protective film 27 (see FIGS. 5 (B), 6 and the like) that covers the surface 11a side is formed.

In the protective film coating step S30, for example, the protective film agent 25 is applied at a predetermined rotation speed for a predetermined time. However, as described above, the protective film agent 25 may be continuously applied in a plurality of stages by increasing the rotation speed stepwise over time. By applying the protective film agent 25 in a plurality of stages, the protective film 27 can be formed thicker than in the case where the protective film agent 25 is applied at a predetermined rotation speed.

FIG. 5B is an enlarged cross-sectional view of a part of the workpiece 11 with the protective film 27. Note that FIG. 5B shows a case where the upper surface of the protective film 27 is formed flat so as to absorb the step of the recess between the two devices 15. However, the protective film 27 may be formed to have a constant thickness so as to imitate the unevenness of the surface 11a.

In order to reduce the burning of the device 15, the thickness of the protective film 27 is preferably 3.8 μm or more, more preferably 4.0 μm or more or 5.5 μm or more, and 6.8 μm or more or 7 It is more preferably 1.0 μm or more. However, if the protective film 27 is too thick, laser processing itself becomes difficult, so the thickness of the protective film 27 is preferably 15 μm or less.

FIG. 6 is a perspective view of the workpiece 11 with the protective film 27 manufactured through the preparation step S10, the frame unit forming step S20, and the protective film coating step S30. In addition, S10, S20 and S30 constitute a method for manufacturing a workpiece 11 with a protective film 27.

After the protective film coating step S30, the workpiece 11 is machined by the laser machining apparatus 40 to form a laser machined groove (machined groove forming step S40). FIG. 7 is a diagram showing a machined groove forming step S40 for forming the laser machined groove 33. In FIG. 7, the annular frame 17 and the dicing tape 19 are omitted.

In the machined groove forming step S40, the laser machined device 40 is used. The laser machining apparatus 40 has a chuck table 42 that sucks and holds the back surface 11b side of the workpiece 11. Since the chuck table 42 has the same porous plate, suction source, etc. as the spinner table 32, detailed description thereof will be omitted.

A drive unit (not shown) for rotationally driving the chuck table 42 is provided below the chuck table 42. Further, below the drive unit, an X-axis moving mechanism (not shown) for moving the chuck table 42 along the X-axis direction and a Y-axis moving mechanism (not shown) for moving the chuck table 42 along the Y-axis direction. ) And are provided.

Above the chuck table 42, a laser beam irradiation unit 50 that irradiates a pulsed laser beam is provided. The laser beam irradiation unit 50 irradiates a laser beam having a wavelength absorbed by the workpiece 11. When the workpiece 11 is silicon, the wavelength of light absorbed by the workpiece 11 is, for example, 355 nm.

The laser beam irradiation unit 50 has a casing 52 having a substantially cylindrical shape. A head portion 54 is fixed to the tip portion of the casing 52. The pulsed laser beam emitted from a laser oscillator (not shown) such as a YAG laser oscillator or a YVO ₄ laser oscillator is emitted from the head portion 54 toward the holding surface of the chuck table 42.

The laser beam emitted from the head portion 54 has a predetermined value having a wavelength of 355 nm or more and 1064 nm or less, and a repetition frequency having a predetermined value in the range of 100 kHz to 50,000 kHz. As in the above experimental example, the repetition frequency may be a predetermined value in the range of 200 kHz to 1000 kHz.

The pulse width of the laser beam is set to a predetermined value in the range of 10 fs or more and 500 ps or less (note that fs means femtosecond). Considering the stability of the oscillator and the high output, it is preferable to set the pulse width to a predetermined value in the range of 3 ps or more and 30 ps or less as in the above experimental example.

By the way, when the pulse width of the laser beam is on the nanosecond order, the shape of the laser machining groove 33 is distorted due to the heat generated during machining, and the thermal effect is compared with the case where the pulse width is on the picosecond order. There is a problem that a region is formed and the bending resistance is lowered, and there is a problem of growth debris that debris after processing adheres to the workpiece 11 and grows with the passage of time.

On the other hand, by setting the pulse width of the laser beam to the picosecond order, it is possible to irradiate the laser beam with a high peak output in a short time as compared with the case where the pulse width is on the nanosecond order. It is possible to solve the problems of the shape of 33, the area affected by heat, and the problem of growth debris.

However, when the peak output of the laser beam is high, the energy of the laser beam scattered by the debris soared during the laser processing is also high, so that the burn caused by the scattered light of the laser beam becomes a problem.

On the other hand, as described above, the use of the protective film agent 25 can reduce the burning of the device 15. That is, it can be said that the protective film agent 25 is particularly effective when the workpiece 11 is processed with a laser beam having a pulse width on the order of picoseconds (or femtoseconds).

However, even when the workpiece 11 is laser-processed with a laser beam having a pulse width on the order of nanoseconds, it is needless to say that the use of the protective film agent 25 has the effect of reducing the burning of the device 15.

The output of the laser beam shall be a predetermined value in the range of 0.3 W or more and 100.0 W or less. As in the above experimental example, the predetermined value may be set in the range of 1.0 W or more and 5.0 W or less. The spot diameter of the light-collecting spot has a predetermined length of 1 μm or more and 100 μm or less, but may be a predetermined length of 2 μm or more and 5 μm or less as in the above-mentioned experimental example.

An image pickup unit 56 facing the holding surface is provided at a position adjacent to the head portion 54. The image pickup unit 56 includes a light source unit (not shown) that irradiates visible light, an image pickup element (not shown) that captures the reflected light from the workpiece 11, and a collection for condensing the reflected light on the image pickup element. It has an optical lens.

In the machined groove forming step S40, first, the workpiece 11 is placed on the chuck table 42 so that the surface 11a faces up. Next, the back surface 11b side is sucked and held by the chuck table 42. At this time, the head portion 54 and the image pickup unit 56 are located above the workpiece 11.

After that, the image pickup unit 56 is used to image the scheduled division line 13. Then, based on the imaging result, the chuck table 42 is rotated by a predetermined angle so that the scheduled division line 13 is parallel to the X-axis direction.

Next, the head portion 54 and the chuck table 42 are relatively moved in the X-axis direction while irradiating the surface 11a from the head portion 54 via the protective film 27 with a laser beam. For example, the chuck table 42 is moved in the X-axis direction at a predetermined machining feed rate in the range of 20 mm / sec or more and 2000 mm / sec or less using an X-axis moving mechanism.

The machining feed rate may be a predetermined value in the range of 200 mm / sec or more and 600 mm / sec or less as in the above experimental example. Further, when machining using a polygon mirror, the machining feed rate may be set to a predetermined value in the range of 500 mm / sec or more and 5000 mm / sec or less.

The protective film 27 and the workpiece 11 are ablated along the scheduled division line 13 to form a laser machined groove 33. The laser-machined groove 33 of the present embodiment is a so-called half-cut groove, and is formed to a predetermined depth that does not reach the back surface 11b from the front surface 11a.

After forming the laser machining groove 33 along all the scheduled division lines 13 along one direction, the chuck table 42 is rotated 90 degrees, and all the scheduled division lines 13 along the other direction orthogonal to one direction are formed. The laser processing groove 33 is formed along the above.

After forming the laser machined groove 33 along all the scheduled division lines 13, the laser machined groove 33 is etched by using a plasma etching apparatus (not shown) to divide the workpiece 11 into a plurality of device chips. .. In plasma etching, the surface 11a side is protected by the protective film 27.

In this example, a benzophenone derivative having only two or more hydroxyl groups as a substituent is used as a light absorber. As a result, the absorbance of the protective film agent 25 at 355 nm can be increased as compared with the conventional light absorber such as ferulic acid. Therefore, it is possible to reduce the burning of the device 15 in the machined groove forming step S40. Of course, in addition to the wavelength of 355 nm, even in the case of a wavelength of 532 nm, for example, having a high absorbance and a thickness of 3.8 μm or more has an effect of reducing the burning of the device 15.

Further, the protective film agent 25 containing the light absorber is applied on the surface 11a of the workpiece 11, and the surface 11a side is covered with the protective film 27 having a thickness of 3.8 μm or more, whereby the protective film is formed. Burning of the device 15 in the machined groove forming step S40 can be reduced as compared with the case where 27 has a thickness of less than 3.8 μm (see Experimental Examples 4, 6, 7, 11, 12 and 13 described above).

Further, a benzophenone derivative having only two or more hydroxyl groups as a substituent is used as a light absorber, the absorbance per 1 cm of the optical path length of the protective film agent 25 is set to 0.82 or more, and the thickness of the protective film 27 is set to 0.82 or more. By setting the value to 6.8 μm or more, the burning of the device 15 can be almost eliminated (see Experimental Example 6 above).

When the absorbance is 0.96 or more and the thickness is 6.8 μm or more (see Experimental Example 7 above), or when the absorbance is 0.98 or more and the thickness is 7.0 μm or more (see above). (See Experimental Example 13) can also almost eliminate the burning of the device 15.

After the machined groove forming step S40, the frame unit 31 is conveyed to a cleaning device (not shown) by a transfer arm (not shown), and the surface 11a side of the workpiece 11 is cleaned by the cleaning device (cleaning step S50). In the cleaning step S50, cleaning water (for example, pure water) is sprayed onto the workpiece 11, and the protective film 27 is removed together with the debris (washing removal).

As the cleaning method, it is preferable to use two-fluid cleaning, high-pressure cleaning and the like. The water may be at room temperature or may be heated. If it is difficult to remove the protective film 27 only by washing with water, the protective film 27 may be removed by treatment with plasma or the like. As a result, the laser machining of the workpiece 11 is completed.

In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention. For example, after forming the laser machined groove 33 along all the scheduled division lines 13, the protective film 27 is removed by a cleaning device, and then the laser machined groove 33 is cut by a cutting device. The workpiece 11 may be divided into a plurality of device chips.

By the way, in the machined groove forming step S40 for forming the laser machined groove 33, a plurality of workpieces 11 are formed by forming the laser machined groove 33 (so-called full-cut groove) to a predetermined depth reaching from the front surface 11a to the back surface 11b. It may be divided into device chips of.

In addition, although the spin coating method has been described above, a spray (ultrasonic wave, electrostatic spray) coating method, a dip coating method, an inkjet method, or the like may be used in addition to the spin coating method. Further, the protective film agent 25 coated on the surface 11a may be irradiated with light from a xenon flash lamp to dry and solidify the protective film agent 25 (xenon flash method).

The device 15 may be an IC (Integrated Circuit) or an LSI (Large Scale Integration). Also in this case, by protecting the surface 11a side on which the device 15 is formed with the protective film 27, damage to the device 15 during laser processing can be reduced.

11: Work piece 11a: Front surface 11b: Back surface 13: Scheduled division line 15: Device 17: Circular frame 19: Dicing tape 21: Wafer 23: Laminated body 25: Protective film agent 27: Protective film 30: Protective film forming device 31 : Frame unit 32: Spinner table 33: Laser processing groove 34: Nozzle 40: Laser processing device 42: Chuck table 50: Laser beam irradiation unit 52: Casing 54: Head portion 56: Imaging unit

Claims (6)

It is a processing method of the workpiece that processes the workpiece with a laser beam.
It is composed of a water-soluble resin, an organic solvent, and a solution in which at least a light absorber is dissolved, and the light absorber has two or more hydroxyl groups as a substituent and has a substituent other than the hydroxyl group. A protective film coating step of applying a protective film agent for laser dicing containing a benzophenone derivative that does not exist on one surface of the workpiece and covering the one surface side with a protective film having a thickness of 3.8 μm or more. ,
A processing groove forming step of irradiating one surface of the workpiece with a laser beam having a wavelength absorbed by the workpiece from above the workpiece through the protective film to form a laser-machined groove in the workpiece. A method for processing a workpiece, which comprises. In the protective film coating step, the protective film agent for laser dicing having an absorbance at a wavelength of 355 nm (absorbance converted to a 200-fold diluted solution) of 0.25 or more per 1 cm of optical path length is applied onto one surface of the workpiece. The method for processing a workpiece according to claim 1, wherein the work piece is coated. It is a method of manufacturing a workpiece with a protective film.
It is composed of a water-soluble resin, an organic solvent, and a solution in which at least a light absorber is dissolved, and the light absorber has two or more hydroxyl groups as a substituent and has a substituent other than the hydroxyl group. A preparatory step for preparing a protective film agent for laser dicing containing a benzophenone derivative that does not exist,
It is characterized by comprising a protective film coating step of applying the protective film agent for laser dicing on one surface of a work piece and covering the one surface side with a protective film having a thickness of 3.8 μm or more. A method for manufacturing a workpiece with a protective film. In the protective film coating step, the protective film agent for laser dicing having an absorbance at a wavelength of 355 nm (absorbance converted to a 200-fold diluted solution) of 0.25 or more per 1 cm of optical path length is applied onto one surface of the workpiece. The method for producing a workpiece with a protective film according to claim 3, wherein the work piece is coated. A protective film for laser dicing that is applied to a work piece by irradiating it with a laser beam.
It is composed of a solution in which a water-soluble resin, an organic solvent, and a light absorber are at least dissolved.
The light absorber is a protective film agent for laser dicing, which comprises a benzophenone derivative having two or more hydroxyl groups as a substituent and having no substituent other than the hydroxyl group. The protective film agent for laser dicing according to claim 5, wherein the absorbance at a wavelength of 355 nm (absorbance converted to a 200-fold diluted solution) is 0.25 or more per 1 cm of the optical path length.

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