KR20180111677A - Protective film agent for dicing - Google Patents

Abstract

Provided is a dicing protective agent capable of preventing occurrence of processed burrs without producing debris in a process by a high energy laser using an object to be processed with relatively low mechanical strength. To this end, the dicing protective agent contains a water-soluble resin and a laser beam absorbent. At least one kind of the laser beam absorbent is surface-treated with an inorganic oxide.

Description

{PROTECTIVE FILM AGENT FOR DICING}

The present invention relates to a protective film used for laser dicing in which a predetermined region such as a semiconductor wafer is irradiated with a laser beam to perform predetermined processing.

A wafer to be formed in a semiconductor device manufacturing process is a wafer in which a laminate in which an insulating film and a functional film are laminated on the surface of a semiconductor substrate such as silicon is partitioned by a line to be divided in a lattice called a street, Region is a semiconductor chip such as an IC or an LSI.

A plurality of semiconductor chips are obtained by cutting the wafer along this street. In the optical device wafer, a laminate in which a gallium nitride compound semiconductor or the like is laminated on the surface of a sapphire substrate or the like is divided into a plurality of regions by streets. By cutting along this street, the optical device wafer is divided into optical devices such as light emitting diodes, laser diodes, and the like. These optical devices are widely used in electric devices.

Such cutting along the streets of the wafer has been carried out by a cutting apparatus called dicer in the past. However, in this method, since the wafer having a laminated structure is a highly-shinable material, scratches, defects, or the like may occur when the wafer is divided and cut by a cutting blade (cutting edge) into a semiconductor chip or the like, There is a problem that the insulating film required as a circuit element is peeled off. For this reason, at present, there is a method widely known in which a laser beam is irradiated along a street prior to cutting by a cutting blade to prepare a groove matching the width of the cutting blade (cutting edge), and then the cutting is performed by the blade Is adopted.

However, when the laser light is irradiated along the streets of the wafer, the laser light is absorbed by the silicon substrate, for example, and is converted into thermal energy. Silicon vapor or the like is generated due to melting, thermal decomposition or the like of silicon due to its thermal energy. Then, silicon vapor or the like is condensed on the chip surface and adhered thereto. Such a phenomenon (debris) greatly degrades the quality of the semiconductor chip.

In order to solve the problem caused by debris, Patent Document 1 and Patent Document 2 disclose a method of forming a protective film made of a water-soluble resin containing a light absorbing agent matched with the laser wavelength on a processed surface of a wafer, A processing method for irradiating the surface of the substrate is proposed.

Japanese Laid-Open Patent Publication No. 2005-150523 Japanese Laid-Open Patent Publication No. 2006-140311

In the processing by the laser, a short-pulse laser irradiation is performed in which a higher energy can be irradiated in order to reduce heat damage of the workpiece as much as possible while improving productivity.

On the other hand, there is a tendency that the mechanical strength of the workpiece is lowered due to low-temperature heating of the interlayer insulating film such as the passivation layer. When this high-energy laser is used, a phenomenon occurs that silicon vapor is generated by the thermal decomposition of the substrate by the laser light, and the protective film around the irradiation spot is also destroyed at the same time. In addition, debris adheres to the portion to be processed where the protective film is destroyed, which causes the productivity to be lowered.

In addition, a high-energy laser passes through the protective film and reaches the workpiece, resulting in a high machining burr at the machining site. In this respect, sufficient productivity can not be obtained in some cases.

Disclosed is a protective film for dicing capable of suppressing interlayer delamination of a passivation film, occurrence of debris and generation of burrs, even when a workpiece having a low mechanical strength is processed by a high energy laser, And it is an object of the present invention to provide a method of processing a wafer using a protective film for a semiconductor device.

The object of the present invention is achieved by the following.

(1) A protective film for dicing comprising a water-soluble resin and a laser ray absorbent, wherein at least one of the laser ray absorbent is surface-treated with an inorganic oxide.

(2) The protective film for dicing according to (1), wherein at least one species of the laser ray absorbent is titanium oxide or zinc oxide surface-treated with an inorganic oxide.

(3) The protective film for dicing according to the above (1) or (2), wherein the inorganic oxide is silicon oxide, aluminum hydroxide or zirconium oxide.

(4) The protective film for dicing according to any one of (1) to (3), which contains a defoaming agent.

(5) The protective film for dicing according to any one of (1) to (4), which contains an antibacterial agent.

(6) A wafer processing method using the protective film for dicing according to any one of (1) to (5).

According to the present invention, it is possible to provide a protective film for dicing capable of suppressing delamination of a passivation film, generation of debris, generation of processed burrs and the like even when a workpiece having a low mechanical strength is processed by a high energy laser, A processing method of a wafer using a protective film for dicing can be provided.

1 is a perspective view showing a semiconductor wafer processed by a method of processing a wafer using the protective film of the present invention.
Fig. 2 is an enlarged sectional view of the semiconductor wafer shown in Fig. 1. Fig.
Fig. 3 is an explanatory diagram showing one embodiment of a protective film forming step in the method of processing a wafer according to the present invention. Fig.
4 is an enlarged cross-sectional view of a main part of a semiconductor wafer on which a protective film is formed by the protective film forming step shown in Fig.
5 is a perspective view showing a state in which a semiconductor wafer having a protective film formed thereon is supported on an annular frame via a protective tape.
Fig. 6 is a perspective view of a main portion of a laser machining apparatus for performing a laser beam irradiation process in a method of processing a wafer according to the present invention. Fig.
Fig. 7 is a block diagram briefly showing a configuration of laser irradiation means provided in the laser processing apparatus shown in Fig. 6. Fig.
Fig. 8 is a schematic view for explaining the condensed spot diameter of laser light. Fig.
Fig. 9 is an explanatory diagram of a laser light irradiation step in the method of processing a wafer according to the present invention.
Fig. 10 is an explanatory view showing a laser beam irradiation position for a laser beam irradiation step in the method of processing a wafer according to the present invention. Fig.
11 is an enlarged cross-sectional view of a main part of a semiconductor wafer showing a laser machining groove formed in a semiconductor wafer by a laser beam irradiation step in the method of processing a wafer according to the present invention.
12 is an enlarged cross-sectional view of a main part of a semiconductor wafer showing a state in which a protective film coated on the surface of a semiconductor wafer is removed by a protective film removing step in the method of processing a wafer according to the present invention.
Fig. 13 is a perspective view of a main part of a cutting apparatus for carrying out a cutting step in a method of processing a wafer according to the present invention. Fig.
Fig. 14 is an explanatory diagram of a cutting process in the method of processing a wafer according to the present invention. Fig.
Fig. 15 is an explanatory view showing a state in which a semiconductor wafer is cut along a laser machining groove by a cutting process in a wafer machining method according to the present invention. Fig.

«Protection film for laser dicing»

A protective film for laser dicing (hereinafter, simply referred to as a protective film) contains a laser-absorptive material together with a water-soluble resin. The laser light absorbing agent contains at least one kind of laser light absorbing agent which is surface-treated with an inorganic oxide. Therefore, the protective film formed on the surface of the wafer by coating and drying the protective film exhibits a low transmittance to laser light. As a result, thermal decomposition of the substrate is suppressed, and peeling of the passivation film can be effectively prevented.

Hereinafter, essential or optional components contained in the protective film for laser dicing will be described.

≪ Water-soluble resin &

The water-soluble resin is a substrate of a protective film formed using a protective film. The type of the water-soluble resin is not particularly limited as long as it can be dissolved in a solvent such as water and applied and dried to form a film. For example, there may be mentioned polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymer), polyvinyl pyrrolidone, polyacrylamide, poly (N-alkyl acrylamide), polyallylamine, poly Amylamine), partially amidated polyallylamine, poly (diallylamine), allylamine diallylamine copolymer, polyethylene oxide, methylcellulose, ethylcellulose, hydroxypropylcellulose, polyacrylic acid, polyvinyl alcohol polyacrylic acid block copolymer Polyvinyl alcohol polyacrylate block copolymer, polyglycerin, and the like. These may be used alone or in combination of two or more.

Here, water solubility refers to dissolving at least 0.5 g of solute (water-soluble resin) per 100 g of water at 25 ° C.

The protective film formed on the wafer surface is usually removed by water washing after laser processing. For this reason, a water-soluble resin having a low affinity with the surface of the wafer is preferable from the viewpoint of washing property of the protective film. As the water-soluble resin having low affinity with the wafer surface, a resin having only ether bond, hydroxyl group and amide bond as the polar group such as polyvinyl alcohol, polyethylene glycol and polyvinyl pyrrolidone is preferable.

As these water-soluble resins, commercially available water-soluble resins can be used. These water-soluble resins are commercially available, for example, from Kuraray Co., Ltd., Nippon Synthetic Chemical Industry Co., Ltd., Nippon Sakubi Povar Co., Ltd., Denka Co., Ltd., Nippon Catalyst Co., , Seiko PMC Co., Ltd., Sekisui Chemical Co., Ltd., Shin-Etsu Chemical Co., Ltd., and the like.

A water-soluble resin having a relatively high degree of polymerization or a high molecular weight is somewhat inferior in water washability. However, by using a plasticizer to be described later in combination, it is possible to avoid the deterioration of the water washability.

The content of the water-soluble resin in the protective film is not particularly limited within the range not hindering the object of the present invention. The content of the water-soluble resin is preferably 20% by mass or more and 90% by mass or less, more preferably 40% by mass or less, and more preferably 40% by mass or less with respect to the mass of the solid content of the protective film for laser dicing, And more preferably not less than 80% by mass.

≪ Laser light absorbing agent &

The laser light absorber is characterized in that at least one of the laser light absorbers is surface-treated with an inorganic oxide. Here, the laser ray absorbent is usually a fine particle having an inorganic oxide on its surface. In short, the laser light absorber is an inorganic oxide existing on the surface of the laser light absorber and a microparticle composed of core particles holding the inorganic oxide on the surface.

The mode of retaining the inorganic oxide in the laser ray absorbent is not particularly limited. The inorganic oxide may be spotted on the surface of the core particle, and the entire or almost entire surface of the core particle may be covered with a layer.

In the laser ray absorbent, the material of the core particles is not particularly limited as long as the laser ray absorbent has desirable laser ray absorption characteristics. The material of the core particle is typically an inorganic oxide different from the inorganic oxide retained on the surface of the fine particles of the laser ray absorbent. As the material of the core particles, specifically, titanium oxide or zinc oxide is preferable.

In short, the laser light absorber is preferably a titanium oxide fine particle or a zinc oxide fine particle which retains an inorganic oxide other than titanium oxide and zinc oxide on the surface thereof.

In the case where the core particles are fine particles having photocatalytic activity such as titanium oxide fine particles or zinc oxide fine particles, by holding the inorganic oxide on the surface of the fine particles of the laser ray absorbent, the laser light is absorbed into the fine particles of the laser ray absorbent, The photocatalytic function (property of transferring energy to the surroundings) of titanium or zinc oxide can be suppressed. Therefore, it is possible to secure the time-course stability of the protective film without causing contamination of the processed portion.

As the titanium oxide fine particles, rutile type and anatase type can be used. The average primary particle size and the average secondary particle size of the titanium oxide fine particles are not particularly limited within the range not hindering the object of the present invention. The average primary particle diameter is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 80 nm or less, and further preferably 10 nm or more and 60 nm or less. The average secondary particle diameter is preferably 40 nm or more and 1 占 퐉 or less. The rutile type is preferred in terms of time-course stability.

The zinc oxide fine particles are not particularly limited within the range not hindering the object of the present invention. The zinc oxide can be appropriately selected from known zinc oxide fine particles. The average primary particle diameter of the zinc oxide fine particles is preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 100 nm or less in terms of dispersion stability.

When the average primary particle diameter or the average secondary particle diameter of the titanium oxide fine particles and the zinc oxide fine particles is within the above range, the laser light absorbing performance is sufficiently high according to the specific surface area and the laser light absorbing performance It is easy to be compatible with time-dependent dispersion stability.

The average secondary particle diameter is preferably 15 nm or more and 1 占 퐉 or less, more preferably 20 nm or more and 800 nm or less.

The average particle diameter of the titanium oxide fine particles or the zinc oxide fine particles can be measured by the following method.

The average primary particle diameter can be measured by treating the microscopic observation image with image analysis software and obtaining the circle equivalent diameter of the primary particles. The average primary particle diameter is calculated as an average value of circle equivalent diameters of primary particles of, for example, 10 or more, preferably 50 or more.

The average secondary particle diameter can be measured as a volume average particle diameter using a laser diffraction flow distribution system.

The surface treatment for retaining the inorganic oxide on the surface of the core particles constituting the laser ray absorbent is effective in improving the affinity of the laser ray absorbent for the water-soluble resin and the stability over time of the entire protective layer. Particularly, in the case where the core particles constituting the laser ray absorbent are titanium oxide particles, zinc oxide particles or the like, such surface treatment is very effective. As the surface treatment, a surface treatment using an oxide such as aluminum, silicon or zirconium as the inorganic oxide can be mentioned. Particularly, surface treatment using an oxide of silicon as an inorganic oxide is preferable.

As a result of the surface treatment, the amount of the inorganic oxide retained on the surface of the laser ray absorbent is preferably 0.5% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 20% , And particularly preferably from 3% by mass or more and 15% by mass or less.

The amount of the inorganic oxide retained on the surface of the laser light absorbing agent can be measured by fluorescent X-ray analysis.

Titanium oxide surface-treated with an inorganic oxide is commercially available. (Commercially available from Sakai Chemical Industry Co., Ltd.), AMT-100, MT-05, MT-100AQ, MT-100WP and the like, commercially available products such as R38L, R62N, D-918, STR- TTO-S-3, TTO-V-3 and TTO-W-5 (manufactured by Ishihara Industries Co., Ltd.).

Zinc oxide surface-treated with an inorganic oxide can be obtained as a commercial product. (Commercially available from Sakai Chemical Industries Co., Ltd. (trade name) such as FINEX-50S-LP2, FINEX-50W, FINEX-50W-LP2, FINEX-33W-LP2, FINEX-30S-LPT, DIF- ), ZnO-610Si (4) G, ZnO-510SID and SIH10-ZnO-510SID (manufactured by Sumitomo Osaka Cement Co., Ltd.).

The content of the laser ray absorbent is not particularly limited within the range not hindering the object of the present invention. The content of the laser ray absorbent is preferably from 10 mass% to 80 mass% with respect to the mass of the solid content of the protective film, more preferably from 20 mass% to 60 mass% from the viewpoint of film peel- More preferable.

<Other additives>

In addition to the water-soluble resin and the laser ray absorbent, the protective film agent may also dissolve other compounding agents as long as the object of the present invention is not impaired. As other compounding agents, for example, preservatives, surfactants, plasticizers and the like can be used.

Examples of the preservative include benzoic acid, butylparaben, ethylparaben, methylparaben, propylparaben, sodium benzoate, sodium propionate, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl alcohol, 2 - phenoxyethanol, phenyl mercuric nitrate, thimerosal, metacresol, lauryldimethylamine oxide or a combination thereof.

It is preferable to use a preservative not only in terms of the surface of the protective film but also in terms of reducing the load on the treatment of the waste solution after cleaning the wafer. A large amount of washing water is generally used for cleaning the wafer. However, in the process using the above-mentioned protective film agent, there is a fear of propagation of germs in the waste liquid resulting from the water-soluble resin contained in the protective film agent. Therefore, it is preferable that the waste liquid derived from the process using the protective film is treated separately from the waste liquid derived from the process not using the protective film. However, when a preservative is contained in the protective film, since the propagation of the germs caused by the water-soluble resin is suppressed, the waste liquid derived from the process using the protective film and the waste liquid derived from the process using no protective film Can be processed. Therefore, the load of the wastewater treatment process can be reduced.

The surfactant is used, for example, in order to improve dispersion stability of fine particles of a laser ray absorbent containing core particles such as fibrillation, titanium oxide fine particles and zinc oxide fine particles in the production of a protective film, and coatability of a protective film do. In particular, it is preferable to use a surfactant in terms of defoaming property at the time of production of a protective film.

In the wafer fabrication process, a protective film is generally formed by spin-coating a protective film. However, in the protective film containing particles, when the coating film is dried, irregularities appear to be caused by bubbles in the vicinity of the particles are liable to occur. In order to suppress the occurrence of such irregularities, it is preferable to use a defoaming agent such as a surfactant.

As the surfactant, a water-soluble surfactant can be preferably used. As the surfactant, a nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant can be used. The surfactant may be silicon-based. Nonionic surfactants are preferred from the viewpoint of cleansing properties.

The plasticizer is used, for example, as a defoaming agent of a protective film or to improve the washing property of the protective film after laser processing. Especially when a high molecular weight water-soluble resin is used, a plasticizer is preferably used.

As such a plasticizer, a water-soluble low molecular weight compound is preferable. As the plasticizer, for example, ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, ethanolamine, glycerin and the like can be mentioned. These plasticizers may be used alone or in combination of two or more.

The amount of the plasticizer to be used is not particularly limited within the range not hindering the object of the present invention. Typically, a plasticizer is used in an amount such that the desired vesicles are achieved, or in such an amount that does not cause phase separation with the water-soluble resin after application and drying. For example, 10 mass% or less, particularly 5 mass% or less, based on the water-soluble resin.

Water is mainly used as a solvent for preparing a protective film on a solution. However, an organic solvent may be used within a necessary range. For example, methyl alcohol, ethyl alcohol, alkylene glycol, alkylene glycol monoalkyl ether, alkylene glycol monoalkyl ether acetate and the like can be used.

The solid content concentration of the protective film agent is not particularly limited within the range not hindering the object of the present invention. The solid content concentration is preferably 5 mass% or more and 30 mass% or less, for example.

&Lt; Wafer processing method &

Hereinafter, a method of processing a wafer using the above-described protective film will be described.

The above-described protective film is applied to the processed surface of a wafer on which a plurality of semiconductor chips are formed, for example. Subsequently, a protective film is formed by drying the coating film. And a protective film formed by using a protective film is applied so that the formation of grooves (laser dicing) can be performed by irradiating a predetermined position of the processing surface with the laser beam through the protective film.

The shape of the processed surface of the wafer is not particularly limited as long as the desired processing can be performed on the wafer. Typically, the processed surface of the wafer has many irregularities. A recess is formed in the area corresponding to the street. The thickness of the protective film (thickness after drying of the protective film) is preferably set to a value obtained by dividing the thickness of the protective film by the thickness of the protective film formed on the cutting point by the laser light Preferably in the range of 0.1 to 5 mu m, and more preferably in the range of 0.5 mu m to 3 mu m.

Hereinafter, with reference to the drawings, processing by laser dicing using the above-described protective film is described as a preferred embodiment of wafer processing for a semiconductor wafer having a plurality of semiconductor chips partitioned by lattice-shaped streets do.

Fig. 1 shows a perspective view of a semiconductor wafer processed according to the present invention. Fig. 2 shows an enlarged sectional view of a main part of the semiconductor wafer shown in Fig. In the semiconductor wafer 2 shown in Figs. 1 and 2, a laminate 21 is formed on a surface 20a of a semiconductor substrate 20 such as a silicon substrate, on which a functional film for forming a circuit with an insulating film is laminated. In the layered body 21, a plurality of semiconductor chips 22 such as ICs and LSIs are formed in a matrix.

Each semiconductor chip 22 is partitioned by a street 23 formed in a lattice pattern. In the embodiment shown in the drawings, the insulating film forming the layered body 21 may be a SiO ₂ film or an inorganic film such as SiOF or BSG (SiOB), or a polymer film such as a polyimide film or a parylene film And a low dielectric constant insulating film (low-k film) made of an organic material film.

A protective film is formed on the surface 2a as a processing surface of the semiconductor wafer 2 by using the above-described protective film material before laser processing is performed along the street 23 of the semiconductor wafer 2 described above .

In the protective film forming step, as shown in Fig. 3, a protective film is applied to the front surface 2a of the semiconductor wafer 2 by the spin coater 4. Fig. The spin coater 4 is provided with a chuck table 41 and a nozzle 42. The chuck table 41 is provided with suction holding means. The nozzle 42 is disposed above the central portion of the chuck table 41.

The semiconductor wafer 2 is placed on the chuck table 41 so that the surface 2a is exposed (the back surface is brought into contact with the chuck table 41). Subsequently, while the chuck table 41 is rotated, the protective film of liquid phase is dropped from the nozzle 42 to the center of the surface of the semiconductor wafer 2, so that the protective film of liquid phase flows to the outer circumferential portion by centrifugal force. In this manner, the surface of the semiconductor wafer 2 is covered with a protective film.

This liquid protective film is dried by heating appropriately. 4, a protective film 24 having a thickness of, for example, about 0.1 占 퐉 or more and 5 占 퐉 or less (thickness on the street 23) is formed on the surface 2a of the semiconductor wafer 2, for example.

5, after the protective film 24 is formed on the surface 2a of the semiconductor wafer 2 in this manner, a protective tape 24 mounted on the annular frame 5 is formed on the back surface of the semiconductor wafer 2, (6) is adhered.

Next, the surface 2a of the semiconductor wafer 2 (the street 23) is irradiated with a laser beam through the protective film 24. This laser light irradiation step is carried out using the laser processing apparatus shown in Figs. 6 to 8.

The laser is preferably an ultraviolet laser having a wavelength of 100 nm or more and 400 nm or less in terms of intensity. YVO4 lasers such as 266 nm and 355 nm, and YAG lasers are preferable.

The laser machining apparatus 7 shown in Figs. 6 to 8 includes a chuck table 71, a laser beam irradiating means 72, and an image pickup means 73. The chuck table 71 holds the workpiece. The laser light irradiation means irradiates the workpiece held on the chuck table 71 with laser light. The imaging means picks up the workpiece held on the chuck table (71).

The chuck table 71 is configured to suck and hold the workpiece. The chuck table 71 is moved by a moving mechanism (not shown) in the processing feed direction indicated by arrow X and the index feed direction indicated by arrow Y in Fig.

As shown in Fig. 7, the laser light irradiating means 72 includes a cylindrical casing 721 arranged substantially horizontally. In the casing 721, a pulsed laser oscillation means 722 and a transmission optical system 723 are arranged. The pulse laser light oscillating means 722 is constituted by a pulse laser oscillator 722a and a repetition frequency setting means 722b. The pulse laser light oscillator 722a is composed of a YAG laser oscillator or a YVO4 laser oscillator. The repetition frequency setting means 722b is attached to the pulse laser light oscillator 722a.

The transmission optical system 723 includes a suitable optical element such as a beam splitter. A condenser 724 is mounted on the distal end of the casing 721. The condenser 724 accommodates a condenser lens (not shown). The condenser lens is composed of a set lens which is in a known form. The laser light emitted from the pulsed laser light oscillation means 722 reaches the condenser 724 via the transmission optical system 723. [ Then, the laser light is irradiated from the condenser 724 to the workpiece held on the chuck table 71 at a predetermined condensing spot diameter D.

As shown in FIG. 8, when the pulsed laser beam exhibiting the Gaussian distribution is irradiated through the objective condenser lens 724a of the condenser 724, the condensed spot diameter D satisfies the following formula:

D (占 퐉) = 4 占? F / (? W)

(Mm) of the pulsed laser beam incident on the objective condenser lens 724a, f is the focal length (mm) of the objective condenser lens 724a, ))

.

The imaging means 73 mounted on the distal end portion of the casing 721 constituting the laser light irradiating means 72 may be a conventional imaging device (CCD) for imaging by visible light in the illustrated embodiment. Besides, the image pickup means 73 may be constituted by an infrared illumination means, an optical system, an image pickup element (infrared ray CCD) or the like. The infrared illumination means irradiates the work piece with infrared rays. The optical system captures the infrared ray irradiated by the infrared ray illumination means. The imaging device (infrared CCD) outputs an electric signal corresponding to infrared rays captured by the optical system. The image pickup means 73 sends the picked-up image signal to a control means (not shown).

The laser beam irradiation step performed using the above-described laser machining apparatus 7 will be described with reference to Figs. 6 and 9 to 11. Fig.

In the laser light irradiation step, the semiconductor wafer 2 is first placed on the chuck table 71 of the laser machining apparatus 7 shown in Fig. 6 described above so that the side on which the protective film 24 is formed is exposed So as to be brought into contact with the chuck table 71), and the semiconductor wafer 2 is attracted and held on the chuck table 71. In Fig. 6, the illustration of the annular frame 5 on which the protective tape 6 is mounted is omitted. The annular frame 5 is held by a suitable frame holding means formed on the chuck table 71.

As described above, the chuck table 71 with the semiconductor wafer 2 sucked and held is positioned directly below the image pickup means 73 by a moving mechanism (not shown). The chuck table 71 is positioned immediately below the image pickup means 73 and an alignment operation for detecting the machining area of the semiconductor wafer 2 to be laser machined is performed by the image pickup means 73 and the control means .

The imaging means 73 and the control means not shown perform alignment of the laser light irradiation position. Alignment is performed by aligning the concentrator 724 of the laser light irradiating means 72 for irradiating the street 23 with the laser light along the street 23 formed in the predetermined direction of the semiconductor wafer 2 And pattern matching for pattern matching.

Alignment of the laser light irradiation position is similarly performed on the streets 23 formed on the semiconductor wafer 2 and extending at right angles to the predetermined direction. At this time, an opaque protective film 24 is basically formed on the surface 2a of the semiconductor wafer 2 on which the streets 23 are formed. Even in this case, it is possible to take an image by infrared rays and align from the surface.

As described above, the streets 23 formed on the semiconductor wafer 2 held on the chuck table 71 are detected and alignment of the laser light irradiation positions is performed. 9 (a), the chuck table 71 is moved to the laser beam irradiation area where the condenser 724 of the laser beam irradiating means 72 is located, (The left end in Fig. 9) is positioned immediately below the condenser 724 of the laser light irradiating means 72. [

The chuck table 71 and the semiconductor wafer 2 are moved at a predetermined feeding speed in the direction indicated by arrow X1 in Fig. 9A while irradiating the pulsed laser light 725 from the condenser 724 . 9 (b), when the irradiation position of the laser light irradiating means 7 reaches the position of the other end of the street 23 (the right end in Fig. 9), the pulse laser light 725 The irradiation is stopped and the movement of the chuck table 71 and the semiconductor wafer 2 is stopped.

Next, the chuck table 71 and the semiconductor wafer 2 are moved in a direction perpendicular to the direction of arrow X1 in Fig. 9 (a) and parallel to the surface direction of the surface of the semiconductor wafer 2 Index transfer direction) of 10 占 퐉 or more and 20 占 퐉 or less. The chuck table 71 and the semiconductor wafer 2 are rotated at a predetermined feed rate in the direction indicated by arrow X2 in Fig. 9 (b) while irradiating the pulsed laser light 725 from the laser beam irradiating means 7 . When the chuck table 71 and the semiconductor wafer 2 reach the position shown in Fig. 9 (a), the irradiation of the pulsed laser light 725 is stopped and the movement of the chuck table 71 and the semiconductor wafer 2 Is stopped.

Converging point P is aligned in the vicinity of the upper surface of the street 23 and the pulse laser light 725 is focused on the semiconductor wafer 2 while the chuck table 71 and the semiconductor wafer 2 reciprocate, ) Are examined.

The laser light irradiation step is performed under the following processing conditions, for example.

Light source of laser light     : YVO4 laser or YAG laser

       wavelength     : 355 nm

 Repetition frequency: 50 kHz or more and 100 kHz or less

 Output: 0.3 W or more 4.0 W or less

 Condensing spot diameter:? 9.2 탆

 Processing feed rate: 1 ㎜ / second to 800 ㎜ / second

11, the laminated body 21 having the streets 23 on the surface of the semiconductor wafer 2 is irradiated with the laser processing grooves 25 are formed.

When the laser machining groove 25 reaches the semiconductor substrate 20, the stacked body 21 is removed. When the pulsed laser light 725 is irradiated to the laminate 21 having the street 23 through the protective film 24 in the laser light irradiation process as described above, the laminate 21 and the semiconductor substrate 20 Thermal decomposition of the protective film 24 occurs almost simultaneously with (or prior to) thermal decomposition. As a result, film breakage occurs at the portion irradiated with the laser beam. This is because the protective film 24 has a high laser light absorbing ability.

The layered body 21 and the semiconductor substrate 20 are processed by irradiation of the pulsed laser light 725 after the processing starting point is formed in the protective film 24 or almost simultaneously with the formation of the processing starting point. For this reason, peeling of the protective film 24 due to the pressure of the stacked body 21 and the vapor of the thermal decomposition product of the semiconductor substrate 20 is hardly caused. In addition, adhesion of debris to the peripheral edge portion of the semiconductor chip 22 caused by peeling of the protective film 24 can be effectively prevented.

The adhesion of the protective film 24 to the wafer surface 20a (the surface of the semiconductor chip 22) is also high. Therefore, the protective film 24 is not easily peeled off at the time of processing or the like. Therefore, the problem of adhesion of debris due to peeling of the protective film 24 is also effectively avoided.

As shown in Fig. 11, the debris 26 is attached to the surface of the protective film 24 by the formation of the protective film 24. Therefore, the debris 26 is not attached to the semiconductor chip 22. As a result, deterioration of the quality of the semiconductor chip 22 due to the attachment of the debris 26 can be effectively avoided. And the height of the burr adhering to the machining groove 25 can be reduced.

As described above, when the laser light irradiation process is performed along the predetermined street 23, the semiconductor wafer 2 held by the chuck table 71 is moved in the direction of the arrow Y by the distance of the street (Index process), and the laser light irradiation process is performed again.

After the laser light irradiation step and the indexing step are performed on all the streets 23 extending in the predetermined direction in this way, the semiconductor wafer 2 held on the chuck table 71 is rotated 90 degrees , And the laser light irradiation process and the index process are performed along the streets 23 extending at right angles to the predetermined direction. By these processes, the laser processing grooves 25 can be formed in all the streets 23 formed on the semiconductor wafer 2. [

Next, the protective film 24 coated on the surface 2a of the semiconductor wafer 2 is removed. In this protective film removing step, as described above, since the protective film 24 is formed by the protective film containing a water-soluble resin, it is possible to wash the protective film 24 by water (or hot water) have.

At this time, the debris 26 on the protective film 24 generated in the laser light irradiation step described above also flows together with the protective film 24. As described above, the removal of the protective film 24 is also very easy.

After the protective film 24 is removed as described above, a cutting process is performed to cut the semiconductor wafer 2 along the laser processing groove 25 formed on the basis of the street 23 on the semiconductor wafer 2. As shown in Fig. 13, this cutting step can be carried out by using a cutting device 8 which is generally used as a dicing device.

The cutting process is performed along all the laser processing grooves 25 formed based on all the streets 23 on the semiconductor wafer 2. [ As a result, the semiconductor wafer 2 is cut along the laser processing grooves 25 formed in the street 23 and divided into the individual semiconductor chips 20. In addition, in the cutting process, since the cutting is performed while supplying the cutting water (pure water), the protective film 24 can be removed by the supplied cutting water without independently forming the above-described protective film removing step. That is, the cutting process may also serve as a protective film removing process.

The wafer processing method has been described based on the embodiments. The protective film according to the present invention and the wafer processing method can be applied to various types of laser processing of other wafers, and can be applied to, for example, division of optical device wafers.

Example

The specifications of the laser processing machine used in the following examples are as follows.

Light source of laser light     : YVO4 laser or YAG laser

       wavelength     : 355 nm

 Repetition frequency: 50 kHz or more and 100 kHz or less

 Output: 0.3 W or more 4.0 W or less

            Condensing spot diameter:? 9.2 탆

 Processing feed rate: 1 ㎜ / second to 800 ㎜ / second

(Example 1)

Protective films A, B, C and D having the following compositions were prepared. Further, 0.06 g of EnviroGem AD01 (manufactured by Air Products, Inc.) as a defoaming agent and 0.1 g of paraben as an antibacterial agent were added to each protective film preparation thus prepared.

<Protective film A>

Water-soluble resin: 10 g (polyvinyl alcohol having a degree of saponification of 88% and a degree of polymerization of 300)

Laser light absorbing agent: 8 g (silica surface-treated titanium oxide TTO-W-5 (manufactured by Ishihara Industries Co., Ltd.))

Water: 80 g

<Shielding agent B>

Water-soluble resin: 10 g (polyvinylpyrrolidone K-90)

Laser light absorbing agent: 8 g (silica surface-treated titanium oxide TTO-W-5 (manufactured by Ishihara Industries Co., Ltd.))

Water: 80 g

&Lt; Protective film C &

Water-soluble resin: 10 g (polyvinyl alcohol having a degree of saponification of 88% and a degree of polymerization of 300)

Laser light absorber: 8 g (silica surface-treated zinc oxide FINEX-33W-LP2 (manufactured by Sakai Chemical Industry Co., Ltd.))

Water: 80 g

&Lt; Protective film agent D &

Water-soluble resin: 10 g (polyvinylpyrrolidone K-90)

Laser light absorber: 8 g (silica surface-treated zinc oxide FINEX-33W-LP2 (manufactured by Sakai Chemical Industry Co., Ltd.))

Water: 80 g

&Lt; Comparative protective film X &

Water-soluble resin: 10 g (polyvinyl alcohol having a degree of saponification of 88% and a degree of polymerization of 300)

Laser absorbing agent: 8 g (surface-untreated titanium oxide TKS-203 (manufactured by Teika Corporation))

Water: 80 g

No antifoaming agent or preservative was added to the protective film X.

(Example 2)

A first A ~ D of the protective film with a spinner to form a coating film by coating a silicon wafer with a thickness of 150 ㎛ with SiO ₂ passivation layer having a thickness of 20 ㎚. The coating film was dried to form a protective film on the street at intervals of 0.5 占 퐉 from 0.5 占 퐉 to 2.5 占 퐉 in thickness. The protective film was uniformly formed at all levels. Then, the silicon wafer on which the protective film was formed was mounted on a laser processing machine of the above specification, subjected to laser processing, and then the protective film was rinsed with pure water, and the periphery of the laser scanning was observed.

At all levels, there was no peeling of the passivation layer at the edge, the burr height was low, and the adhesion of the debris to the periphery was at an unobservable level. The processing width was not influenced by the thickness of the coating film and was equal to the laser spot diameter. Table 1 shows the evaluation results at a thickness of 1.5 mu m on the street.

<Evaluation>

Unless otherwise noted, evaluation was made in an environment of 23 ° C and 55% RH.

Debris: ○ I can not confirm attachment.

         △ It is slightly attached, but it is usable enough.

         X It is attached so that it can not be used.

Peeling: The occurrence of film peeling can not be confirmed.

         △ Partial film peeling occurs.

         X film peeling occurs.

Burst height: X The level at the thickness of 1.5 mu m on the protective film X was defined as x.

          Slightly lower than? X.

          It is considerably lower than ○ ×.

Transmittance: A protective film having a film thickness of 1.5 mu m was formed on a glass substrate, and the transmittance of 355 nm was measured by an integrating sphere spectrophotometer.

          ○ transmittance less than 35%

          △ Transmittance more than 35% and less than 50%

          × transmittance exceeding 50%

(Example 3)

The thickness of the protective film A of Example 2 on the street was set to 0.2 탆, and the same evaluation was carried out. The results are shown in Table 1 (A2). Further, the same evaluation was carried out (A3), except that the antifoaming agent and the preservative were not added to the protective film A of Example 2 and the thickness on the street was set to 1.5 탆. The results are shown in Table 1.

(Comparative Example 1)

In the protective film A, a protective film X was produced by using titanium oxide TKS-203 (manufactured by Teika Co., Ltd.) which is not surface-treated with an inorganic oxide described in Japanese Patent Application Laid-Open No. 2005-150523 as a water- And the same evaluation as in Example 2 was carried out. The film thickness was set to 1.5 탆. A slight surface roughness was observed with the naked eye. As a result of observing the periphery of the laser scanning in the same manner as in Example 1, debris and film separation were observed, and the burr height was also high. The results are shown in Table 1.

(Example 4)

The preservative effect was evaluated as follows. With respect to the protective film agent A and the protective film agent X, evaluation was carried out using each of the collected waste liquids. Specifically, each of three kinds of general bacteria, heterotrophic bacteria and fungi was inoculated in 1 ml of the collected waste solution, and then cultured at 35 DEG C for 48 hours. After incubation, the number of colonies was confirmed for each of the three bacteria. The total number of colonies of the three kinds of bacteria was 15 for the protective film A and 900 for the protective film X.

2: Semiconductor wafer
20: substrate
21:
22: Semiconductor chip
23: Street
24: Resin coating
25: laser machining groove
26: Cutting groove
3: Spin Coater
5: Frame of the annular
6: Protective tape
7: Laser processing equipment
71: chuck table of laser processing apparatus
72: laser beam irradiation means
8: Cutting device
81: chuck table of cutting device
82: cutting means

Claims (6)

A protective film for dicing comprising a water-soluble resin and a laser ray absorbent, wherein at least one of the laser ray absorbent is surface-treated with an inorganic oxide. The method according to claim 1,
Wherein at least one species of the laser light absorber is titanium oxide or zinc oxide surface-treated with an inorganic oxide. 3. The method according to claim 1 or 2,
Wherein the inorganic oxide is silicon oxide, aluminum hydroxide, or zirconium oxide. 3. The method according to claim 1 or 2,
And a defoaming agent. 3. The method according to claim 1 or 2,
A protective film for dicing comprising an antimicrobial agent. A wafer processing method using the protective film for dicing according to any one of claims 1 to 5.

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