JP2018174310A - Protective film agent for dicing - Google Patents

Abstract

Disclosed is a dicing protective film agent that can prevent a debris from being generated by processing with a high energy laser and can suppress generation of processing burrs even if the workpiece has a relatively low mechanical strength. . A dicing protective film agent comprising a water-soluble resin and a laser light absorber, wherein at least one of the laser light absorbers is surface-treated with an inorganic oxide. [Selection] Figure 4

Description

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

  A wafer formed in a semiconductor device manufacturing process is a laminate in which an insulating film and a functional film are laminated on the surface of a semiconductor substrate such as silicon, and is partitioned by grid-like division planned lines called streets. Each partitioned area is a semiconductor chip such as an IC or LSI.

  A plurality of semiconductor chips can be obtained by cutting the wafer along this street. In an 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 partitioned 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 and laser diodes. These optical devices are widely used in electrical equipment.

  Such cutting along the street of the wafer has been performed by a cutting device called a dicer in the past. However, in this method, since the wafer having a laminated structure is a highly brittle material, when the wafer is cut and divided into semiconductor chips or the like by a cutting blade (cutting edge), scratches or chips are generated, or the chip surface is There has been a problem that an insulating film necessary for the formed circuit element is peeled off. For this reason, at present, prior to cutting with a cutting blade, laser light is irradiated along the street to form a groove in accordance with the width of the cutting blade (cutting edge), and then cutting with the blade is performed. Widely adopted.

  However, when laser light is irradiated along the street of the wafer, the laser light is absorbed by, for example, a silicon substrate and converted into thermal energy. Silicon vapor or the like is generated due to melting, thermal decomposition, or the like of silicon due to the thermal energy. As a result, silicon vapor or the like is condensed and attached to the chip surface. Such a phenomenon (debris) greatly reduces the quality of the semiconductor chip.

  In order to solve the problem caused by debris, in Patent Document 1 and Patent Document 2, a protective film made of a water-soluble resin containing a light absorber matched to the wavelength of the laser is formed on the processed surface of the wafer, and the protective film A processing method for irradiating a laser beam via a laser beam has been proposed.

JP 2005-150523 A JP 2006-140311 A

  In the processing by the laser, short pulse laser irradiation capable of irradiation with higher energy is performed in order to reduce the thermal damage of the workpiece as much as possible while increasing productivity.

On the other hand, the mechanical strength of the workpiece tends to decrease with the reduction of the dielectric of the interlayer insulating film such as the passivation layer. When this high energy laser is used, a phenomenon occurs in which silicon vapor is generated by the thermal decomposition of the substrate by the laser beam, and the protective film around the irradiation spot is destroyed at the same time. Then, debris adheres to the part to be processed where the protective film is lost due to destruction, which causes a decrease in productivity.
Further, as a result of the high energy laser passing through the protective film and reaching the workpiece, a high processing burr may occur at the processing site. From this point, sufficient productivity may not be obtained.

  The present invention is a dicing protective film agent that can suppress the delamination of the passivation film, the generation of debris, the generation of processing burr, etc., even when a workpiece having low mechanical strength is processed by a high energy laser. And a method for processing a wafer using the protective film agent for dicing.

  The object of the present invention has been achieved by the following.

(1) A dicing protective film agent comprising a water-soluble resin and a laser light absorber, wherein at least one of the laser light absorbers is surface-treated with an inorganic oxide.
(2) The protective film agent for dicing according to (1), wherein at least one of the laser light absorbers is titanium oxide or zinc oxide surface-treated with an inorganic oxide.
(3) The protective film agent for dicing according to (1) or (2), wherein the inorganic oxide is silicon oxide, aluminum hydroxide, or zirconium oxide.
(4) The protective film agent for dicing according to any one of (1) to (3), which comprises an antifoaming agent.
(5) The protective film agent for dicing according to any one of (1) to (4), which contains an antibacterial agent.
(6) A wafer processing method using the protective film agent for dicing according to any one of (1) to (5).

  According to the present invention, even when a workpiece having low mechanical strength is processed with a high-energy laser, delamination of a passivation film, generation of debris, generation of processing burr, and the like can be suppressed. A film agent and a wafer processing method using the protective film agent for dicing can be provided.

The perspective view which shows the semiconductor wafer processed by the processing method of the wafer using the protective film agent of this invention. FIG. 2 is an enlarged cross-sectional view of the semiconductor wafer shown in FIG. 1. Explanatory drawing which shows one Embodiment of the protective film formation process in the processing method of the wafer concerning this 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. 3. The perspective view which shows the state by which the semiconductor wafer in which the protective film was formed was supported by the cyclic | annular flame | frame via the protective tape. The perspective view of the principal part of the laser processing apparatus which implements a laser beam irradiation process in the processing method of the wafer concerning this invention. The block diagram which shows simply the structure of the laser beam irradiation means with which the laser processing apparatus shown by FIG. 6 is equipped. The simplification figure for demonstrating the condensing spot diameter of a laser beam. Explanatory drawing of the laser beam irradiation process in the processing method of the wafer concerning this invention. Explanatory drawing which shows the laser beam irradiation position about the laser beam irradiation process in the processing method of the wafer concerning this invention. The principal part expanded sectional view of the semiconductor wafer which shows the laser processing groove | channel formed in the semiconductor wafer by the laser beam irradiation process in the processing method of the wafer concerning this invention. The principal part expanded sectional view of the semiconductor wafer which shows the state which removed the protective film coat | covered on the surface of the semiconductor wafer by the protective film removal process in the processing method of the wafer concerning this invention. The principal part perspective view of the cutting device for enforcing the cutting process in the processing method of the wafer concerning the present invention. Explanatory drawing of the cutting process in the processing method of the wafer concerning this invention. Explanatory drawing which shows the state by which a semiconductor wafer is cut along a laser processing groove | channel by the cutting process in the processing method of the wafer concerning this invention.

≪Protective film agent for laser dicing≫
The protective film agent for laser dicing (hereinafter, also simply referred to as “protective film agent”) contains a laser light absorber together with a water-soluble resin. The laser light absorber includes a laser light absorber that is surface-treated with an inorganic oxide as at least one kind thereof. For this reason, the protective film formed on the wafer surface by applying and drying this protective film agent exhibits a low transmittance for laser light. As a result, the thermal decomposition of the substrate is suppressed, and the passivation film can be effectively prevented from peeling off.
Hereinafter, essential or optional components contained in the protective film agent for laser dicing will be described.

<Water-soluble resin>
The water-soluble resin is a base material for a protective film formed using a protective film agent. The type of 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, polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymer), polyvinylpyrrolidone, polyacrylamide, poly (N-alkylacrylamide), polyallylamine, poly (N-alkylallylamine), partially amidated polyallylamine, poly ( Diallylamine), allylamine / diallylamine copolymer, polyethylene oxide, methylcellulose, ethylcellulose, hydroxypropylcellulose, polyacrylic acid, polyvinyl alcohol polyacrylic acid block copolymer, polyvinyl alcohol polyacrylic acid ester block copolymer, polyglycerin, etc. Can be mentioned. These can also be used individually by 1 type and can also be used in combination of 2 or more type.
Here, “water-soluble” means that 0.5 g or more of a solute (water-soluble resin) is dissolved in 100 g of water at 25 ° C.

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

Commercially available water-soluble resins can be used as these water-soluble resins. These water-soluble resins are, for example, Kuraray Co., Ltd., Nippon Synthetic Chemical Industry Co., Ltd., Nippon Vinegar Poval Co., Ltd., Denka Co., Ltd., Nippon Shokubai Co., Ltd., Nitto Bo Medical Co., Ltd., Seiko PMC Available from Sekisui Chemical Co., Ltd., Shin-Etsu Chemical Co., Ltd.
A water-soluble resin having a relatively high degree of polymerization or molecular weight is slightly inferior in water washing. However, it is possible to avoid a decrease in water washability by using a plasticizer described later in combination.
Content in the protective film agent of water-soluble resin is not specifically limited in the range which does not inhibit the objective of this invention. Although depending on the type of the water-soluble resin, the content of the water-soluble resin is 20% by mass or more and 90% by mass with respect to the mass of the solid content of the protective film agent for laser dicing, from the viewpoints of coating properties and drying properties. The following is preferable, and 40 mass% or more and 80 mass% or less are more preferable.

<Laser light absorber>
At least one of the laser light absorbers is surface-treated with an inorganic oxide. Here, the laser light absorber is usually fine particles having an inorganic oxide on the surface thereof. That is, the laser light absorber is a fine particle composed of an inorganic oxide present on the surface of the laser light absorber and core particles that hold the inorganic oxide on the surface.
The aspect of retaining the inorganic oxide in the laser light absorber is not particularly limited. The inorganic oxide may be scattered on the surface of the core particle, or the entire surface or substantially the entire surface of the core particle may be coated in a layered manner.
In the laser light absorber, the material of the core particles is not particularly limited as long as the laser light absorber has the desired laser light absorption characteristics. The material of the core particles is typically an inorganic oxide of a different type from the inorganic oxide retained on the surface of the laser light absorbent fine particles. Specifically, the material of the core particles is preferably titanium oxide or zinc oxide.
That is, as the laser light absorber, titanium oxide fine particles or zinc oxide fine particles that hold inorganic oxides other than titanium oxide and zinc oxide on the surface thereof are preferable.

  When the core particle is a fine particle having photocatalytic activity such as a titanium oxide fine particle or a zinc oxide fine particle, an inorganic oxide is held on the surface of the fine particle of the laser light absorbent, whereby the laser light is applied to the fine particle of the laser light absorbent. The photocatalytic ability (the property of transferring energy to the periphery) of titanium oxide or zinc oxide can be suppressed while absorbing water. For this reason, it is possible to ensure the temporal stability of the protective film agent without polluting the processed part.

As the titanium oxide fine particles, either a rutile type or an anatase type can be used. The average primary particle diameter and average secondary particle diameter of the titanium oxide fine particles are not particularly limited as long as the object of the present invention is not impaired. The average primary particle size is preferably 1 nm to 100 nm, more preferably 5 nm to 80 nm, and still more preferably 10 nm to 60 nm. The average secondary particle diameter is preferably 40 nm or more and 1 μm or less. The rutile type is preferred from the viewpoint of stability over time.
The zinc oxide fine particles are not particularly limited as long as the object of the present invention is not impaired. 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 from the viewpoint 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 are within the above range, sufficiently high laser light absorption performance with a wide specific surface area, and in the protective film agent It is easy to achieve both stable dispersion over time of the laser light absorber.
The average secondary particle diameter is preferably 15 nm or more and 1 μm or less, and 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 processing a microscope observation image with image analysis software and determining the equivalent circle diameter of the primary particles. The average primary particle diameter is calculated, for example, as an average value of equivalent circle diameters of primary particles of 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 meter.

The surface treatment that retains the inorganic oxide on the surface of the core particle that constitutes the laser light absorber is effective in terms of improving the affinity of the laser light absorber for the water-soluble resin and the stability over time of the entire protective film. It is. In particular, such surface treatment is extremely effective when the core particles constituting the laser light absorber are titanium oxide particles or zinc oxide particles. Examples of such surface treatment include surface treatment using an oxide such as aluminum, silicon, and zirconium as the inorganic oxide. In particular, surface treatment using silicon oxide as the inorganic oxide is preferable.
As a result of the surface treatment, the amount of the inorganic oxide retained on the surface of the laser light absorber is preferably 0.5% by mass or more and 30% by mass or less, and preferably 1% by mass or more and 20% by mass with respect to the mass of the laser light absorber. More preferably, it is more preferably 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 absorber can be measured by fluorescent X-ray analysis.

  Titanium oxide surface-treated with an inorganic oxide can be obtained as a commercial product. Commercially available products include R38L, R62N, D-918, STR-40-LP, GT-10W2, etc. (above, manufactured by Sakai Chemical Industry Co., Ltd.), AMT-100, MT-05, MT-100AQ, MT-100WP. , TKP-101 etc. (above, manufactured by Teika Co., Ltd.), TTO-S-3, TTO-V-3, TTO-W-5 etc. (above, manufactured by Ishihara Sangyo Co., Ltd.) and the like.

  Zinc oxide surface-treated with an inorganic oxide can be obtained as a commercial product. Commercially available products include FINEX-50S-LP2, FINEX-50W, FINEX-50W-LP2, FINEX-33W-LP2, FINEX-30S-LPT, DIF-3W4, DIF-AQL-33W, etc. Co., Ltd.), ZnO-610Si (4) G, ZnO-510SID, SIH10-ZnO-510SID, etc. (above, manufactured by Sumitomo Osaka Cement Co., Ltd.).

  The content of the laser light absorber is not particularly limited as long as the object of the present invention is not impaired. The content of the laser light absorber is preferably 10% by mass or more and 80% by mass or less based on the mass of the solid content of the protective film agent, and is 20% by mass or more from the viewpoint of prevention of film peeling at the time of laser irradiation and applicability. More preferably, it is 60 mass% or less.

<Other additives>
In addition to the water-soluble resin and the laser light absorber, other compounding agents can be dissolved in the protective film agent 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.

  Preservatives include benzoic acid, butyl paraben, ethyl paraben, methyl paraben, propyl paraben, sodium benzoate, sodium propionate, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl alcohol 2-phenoxyethanol, phenylmercuric nitrate, thimerosal, metacresol, lauryldimethylamine oxide or combinations thereof can be used.

  It is preferable to use a preservative not only from the viewpoint of preserving the protective film agent but also from the viewpoint of reducing the load of processing the waste liquid after the wafer cleaning. In general, a large amount of washing water is used for washing the wafer. However, in the process using the above-described protective film agent, there is a concern about propagation of germs in the waste liquid due to the water-soluble resin contained in the protective film agent. Therefore, it is desirable that the waste liquid derived from the process using the protective film agent is treated separately from the waste liquid derived from the process not using the protective film agent. However, when preservatives are included in the protective film agent, the growth of miscellaneous bacteria due to the water-soluble resin is suppressed, resulting in the waste liquid derived from the process using the protective film agent and the process not using the protective film agent. The waste liquid to be treated can be treated similarly. For this reason, the load of a wastewater treatment process can be reduced.

  Surfactant has, for example, antifoaming properties during production of protective film agent, dispersion stability of fine particles of laser light absorber including core particles such as titanium oxide fine particles and zinc oxide fine particles, and coatability of protective film agent. Used to enhance. In particular, it is preferable to use a surfactant from the viewpoint of defoaming properties during the production of the protective film.

  In the wafer manufacturing process, the protective film is generally formed by spin coating a protective film agent. However, in a protective film containing particles, irregularities that are likely to be caused by bubbles are likely to occur around the particles when the coating film is dried. In order to suppress the occurrence of such irregularities, it is preferable to use an antifoaming agent such as a surfactant.

  As the surfactant, a water-soluble surfactant can be preferably used. As the surfactant, any of nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used. The surfactant may be a silicone type. Nonionic surfactants are preferred from the standpoint of detergency.

  The plasticizer is used, for example, as an antifoaming agent for the protective film agent or for enhancing the water washability of the protective film after laser processing. In particular, when a high molecular weight water-soluble resin is used, a plasticizer is preferably used.

Such a plasticizer is preferably a water-soluble low molecular weight compound. Examples of the plasticizer include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, ethanolamine, and glycerin. These plasticizers can be used alone or in combination of two or more.
The amount of the plasticizer used is not particularly limited as long as the object of the present invention is not impaired. Typically, the plasticizer is used in such an amount that the desired defoaming is achieved or does not cause phase separation with the water-soluble resin after coating and drying. For example, it is good to set it as the range of 10 mass% or less with respect to water-soluble resin, especially 5 mass% or less.

In the preparation of the solution-type protective film agent, water is mainly used as a solvent. 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, or the like can be used.
The solid content concentration of the protective film agent is not particularly limited as long as the object of the present invention is not impaired. The solid content concentration is preferably 5% by mass or more and 30% by mass or less, for example.

≪Wafer processing method≫
Hereinafter, a wafer processing method using the above-described protective film agent will be described.
The above-described protective film agent is applied to, for example, a processed surface of a wafer on which a plurality of semiconductor chips are formed. Next, the protective film is formed by drying the coating film. A protective film formed using a protective film agent is applied so that a groove is formed (laser dicing) by irradiating a predetermined position on the processing surface with laser light through this protective film.

  The shape of the processed surface of the wafer is not particularly limited as long as desired processing can be performed on the wafer. Typically, the processed surface of the wafer has a large number of irregularities. And the recessed part is formed in the area | region equivalent to a street. The thickness of the protective film (thickness after drying of the protective film agent) is determined by the laser beam cutting position, taking into account the intrusion of debris into the protective film formed on the uneven wafer surface and the removal time after washing with water after processing. The upper side (typically on the street) is preferably about 0.1 μm to 5 μm, more preferably 0.5 μm to 3 μm.

  Hereinafter, with reference to the drawings, processing by laser dicing using the above-described protective film agent will be described as a preferable aspect of wafer processing for a semiconductor wafer including a plurality of semiconductor chips partitioned by lattice streets.

  FIG. 1 shows a perspective view of a semiconductor wafer processed in accordance with the present invention. FIG. 2 shows an enlarged cross-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 laminated body 21 in which an insulating film and a functional film for forming a circuit are laminated is provided on a surface 20a of a semiconductor substrate 20 such as silicon. In the stacked 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 streets 23 formed in a lattice shape. In the illustrated embodiment, the insulating film forming the stacked body 21 is an SiO ₂ film, an inorganic film such as SiOF or BSG (SiOB), or a polymer film such as polyimide or parylene. It consists of a low dielectric constant insulator film (Low-k film) made of an organic film.

  Before performing laser processing along the streets 23 of the semiconductor wafer 2 described above, first, a protective film is formed on the surface 2a which is the processed surface of the semiconductor wafer 2 using the protective film agent described above.

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

  The semiconductor wafer 2 is placed on the chuck table 41 so that the front surface 2a is exposed (the back surface is in contact with the chuck table 41). Next, by dropping the liquid protective film agent from the nozzle 42 onto the center of the surface of the semiconductor wafer 2 while rotating the chuck table 41, the liquid protective film agent flows to the outer peripheral portion by centrifugal force. In this way, the surface of the semiconductor wafer 2 is coated with the protective film agent.

  The liquid protective film agent is dried by heating appropriately. As a result, as shown in FIG. 4, a protective film 24 having a thickness of, for example, about 0.1 μm to 5 μm (thickness on the street 23) is formed on the surface 2a of the semiconductor wafer 2.

  After the protective film 24 is formed on the front surface 2a of the semiconductor wafer 2 in this manner, the protective tape 6 attached to the annular frame 5 is attached to the back surface of the semiconductor wafer 2 as shown in FIG. Is done.

Next, the surface 2 a (street 23) of the semiconductor wafer 2 is irradiated with laser light through the protective film 24. This laser light irradiation process is performed using the laser processing apparatus shown in FIGS.
The laser is preferably an ultraviolet laser having a wavelength of 100 nm or more and 400 nm or less from the viewpoint of intensity. Further, a YVO4 laser having a wavelength of 266 nm, 355 nm or the like, and a YAG laser are preferable.

  The laser processing apparatus 7 shown in FIGS. 6 to 8 includes a chuck table 71, laser light irradiation means 72, and imaging means 73. The chuck table 71 holds a workpiece. The laser beam irradiation means irradiates the workpiece held on the chuck table 71 with the laser beam. The imaging unit images the workpiece that is held on the chuck table 71.

  The chuck table 71 is configured to suck and hold a workpiece. The chuck table 71 is moved in a machining feed direction indicated by an arrow X and an index feed direction indicated by an arrow Y in FIG.

  Further, as shown in FIG. 7, the laser beam irradiation means 72 includes a cylindrical casing 721 arranged substantially horizontally. In the casing 721, a pulse laser beam oscillation means 722 and a transmission optical system 723 are disposed. The pulse laser beam oscillation means 722 is composed of a pulse laser beam oscillator 722a and a repetition frequency setting means 722b. The pulsed laser beam oscillator 722a is a YAG laser oscillator or a YVO4 laser oscillator. The repetition frequency setting means 722b is attached to the pulse laser beam oscillator 722a.

  The transmission optical system 723 includes an appropriate optical element such as a beam splitter. A condenser 724 is attached to the tip of the casing 721. The condenser 724 houses a condenser lens (not shown). The condenser lens is composed of a combination lens that may be in a known form. The laser light oscillated from the pulsed laser light oscillation means 722 reaches the condenser 724 via the transmission optical system 723. Next, the laser beam is irradiated from the condenser 724 to the workpiece held on the chuck table 71 with a predetermined focused spot diameter D.

As shown in FIG. 8, when the pulse laser beam having a Gaussian distribution is irradiated through the objective condenser lens 724 a of the condenser 724, the condensed spot diameter D is expressed by the following formula:
D (μm) = 4 × λ × f / (π × W)
(Wherein, λ is the wavelength (μm) of the pulsed laser beam, W is the diameter (mm) of the pulsed laser beam incident on the objective condenser lens 724a, and f is the focal length (mm) of the objective condenser lens 724a. )
It is prescribed by.

  In the illustrated embodiment, the image pickup means 73 attached to the tip of the casing 721 constituting the laser light irradiation means 72 may be a normal image pickup device (CCD) that picks up an image with visible light. In addition, the imaging unit 73 may be configured by an infrared illumination unit, an optical system, an imaging element (infrared CCD), and the like. The infrared illumination means irradiates the workpiece with infrared rays. The optical system captures infrared rays irradiated by the infrared illumination means. The image sensor (infrared CCD) outputs an electrical signal corresponding to the infrared rays captured by the optical system. The imaging unit 73 sends the captured image signal to a control unit (not shown).

  The laser beam irradiation process performed using the laser processing apparatus 7 mentioned above is demonstrated with reference to FIG. 6 and FIGS.

  In the laser light irradiation step, first, the semiconductor wafer 2 is exposed on the chuck table 71 of the laser processing apparatus 7 shown in FIG. 6 described above so that the side on which the protective film 24 is formed (the back surface is on the chuck table 71). The semiconductor wafer 2 is sucked and held on the chuck table 71. In FIG. 6, the illustration of the annular frame 5 to which the protective tape 6 is attached is omitted. The annular frame 5 is held by appropriate frame holding means disposed on the chuck table 71.

  As described above, the chuck table 71 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging means 73 by a moving mechanism (not shown). After the chuck table 71 is positioned immediately below the image pickup means 73, an alignment operation for detecting a processing region to be laser processed of the semiconductor wafer 2 is executed by the image pickup means 73 and a control means (not shown).

  The imaging unit 73 and a control unit (not shown) perform alignment of the laser light irradiation position. The alignment includes pattern matching for aligning the street 23 formed in a predetermined direction of the semiconductor wafer 2 and the condenser 724 of the laser beam irradiation means 72 that irradiates the laser beam along the street 23. This is done by executing image processing.

  The alignment of the laser beam irradiation position is similarly performed on the street 23 formed on the semiconductor wafer 2 and extending at right angles to the predetermined direction. At this time, a basically opaque protective film 24 is formed on the surface 2 a where the streets 23 of the semiconductor wafer 2 are formed. Even in this case, it can be imaged with infrared rays and aligned 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 beam irradiation position is performed. After the alignment, as shown in FIG. 9A, the chuck table 71 is moved to the laser light irradiation region where the condenser 724 of the laser light irradiation means 72 is located, and one end of the predetermined street 23 (in FIG. 9). (Left end) is positioned directly below the condenser 724 of the laser beam irradiation means 72.

  The chuck table 71 and the semiconductor wafer 2 are moved at a predetermined feed speed in the direction indicated by the arrow X1 in FIG. 9A while irradiating the pulse laser beam 725 from the condenser 724. 9B, when the irradiation position of the laser beam irradiation means 7 reaches the position of the other end of the street 23 (the right end in FIG. 9), the irradiation of the pulsed laser beam 725 is stopped. At the same time, 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 perpendicular to the direction of the arrow X1 in FIG. 9A and parallel to the surface direction of the surface of the semiconductor wafer 2 (index feed direction). 10 μm to 20 μm. Then, while irradiating the pulse laser beam 725 from the laser beam irradiation means 7, the chuck table 71 and the semiconductor wafer 2 are moved at a predetermined feed speed in the direction indicated by the arrow X2 in FIG. 9B. When the chuck table 71 and the semiconductor wafer 2 reach the position shown in FIG. 9A, the irradiation of the pulse laser beam 725 is stopped and the movement of the chuck table 71 and the semiconductor wafer 2 is stopped.

  While the chuck table 71 and the semiconductor wafer 2 are reciprocatingly moved, the semiconductor wafer 2 is irradiated with pulsed laser light 725 with the focal point P near the upper surface of the street 23 as shown in FIG.

The laser beam irradiation process is performed, for example, under the following processing conditions.
Laser light source: YVO4 laser or YAG laser
Wavelength: 355nm
Repetition frequency: 50 kHz to 100 kHz
Output: 0.3W to 4.0W
Condensing spot diameter: φ9.2 μm
Processing feed rate: 1 mm / second or more and 800 mm / second or less

  By performing the laser beam irradiation process described above, as shown in FIG. 11, a laser processed groove 25 is formed along the street 23 in the stacked body 21 including the street 23 on the surface of the semiconductor wafer 2.

  When the laser processed groove 25 reaches the semiconductor substrate 20, the stacked body 21 is removed. In such a laser beam irradiation step, when the pulsed laser beam 725 is irradiated to the stacked body 21 including the streets 23 through the protective film 24, the thermal decomposition of the stacked body 21 and the semiconductor substrate 20 (or the thermal decomposition thereof). Prior to the thermal decomposition of the protective film 24 occurs. 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 absorption ability.

  After the processing start point is formed on the protective film 24 as described above, or almost simultaneously with the formation of the processing start point, the stacked body 21 and the semiconductor substrate 20 are processed by irradiation with the pulse laser beam 725. For this reason, the protective film 24 is unlikely to peel off due to the pressure due to the vapor of the thermal decomposition product of the stacked body 21 and the semiconductor substrate 20. Further, debris can be effectively prevented from adhering to the peripheral portion of the semiconductor chip 22 due to such peeling of the protective film 24.

  Also, the adhesion of the protective film 24 to the wafer surface 20a (the surface of the semiconductor chip 22) is high. For this reason, the protective film 24 hardly peels off during processing or the like. Therefore, the problem of debris adhesion due to peeling of the protective film 24 is also effectively avoided.

  As shown in FIG. 11, the debris 26 adheres to the surface of the protective film 24 by forming the protective film 24. For this reason, the debris 26 does not adhere to the semiconductor chip 22. As a result, it is possible to effectively avoid the deterioration of the quality of the semiconductor chip 22 due to the adhesion of the debris 26. And the height of the burr | flash accompanying the process groove | channel 25 can also be reduced.

  As described above, when the laser beam irradiation process is executed along the predetermined street 23, the semiconductor wafer 2 held on the chuck table 71 is indexed and moved by the street interval in the direction indicated by the arrow Y (indexing process), and again. The laser beam irradiation process is performed.

  After performing the laser beam irradiation process and the indexing process for all the streets 23 extending in the predetermined direction in this way, the semiconductor wafer 2 held on the chuck table 71 is rotated by 90 degrees to move in the predetermined direction. The laser beam irradiation process and the indexing process are executed in the same manner as described above along each street 23 extending at a right angle. Through these steps, the laser processing grooves 25 can be formed in all the streets 23 formed in the semiconductor wafer 2.

  Next, the protective film 24 covered on the surface 2a of the semiconductor wafer 2 is removed. In this protective film removal step, as described above, since the protective film 24 is formed of a protective film agent containing a water-soluble resin, the protective film 24 can be washed away with water (or warm water) as shown in FIG. .

  At this time, the debris 26 on the protective film 24 generated in the laser light irradiation step described above is also flowed together with the protective film 24. In this way, the protective film 24 can be removed very easily.

  After removing the protective film 24 as described above, a cutting process is performed in which the semiconductor wafer 2 is cut along the laser processed grooves 25 formed on the streets 23 on the semiconductor wafer 2. As shown in FIG. 13, this cutting step can be performed using a cutting device 8 that 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 streets 23 and divided into individual semiconductor chips 20. In the cutting process, cutting is performed while supplying cutting water (pure water). Therefore, the protective film 24 is removed by the supplied cutting water without providing the protective film removing process described above independently. You can also. That is, the cutting process may also serve as the protective film removing process.

  In the above, the wafer processing method was demonstrated based on embodiment. The protective film agent and the wafer processing method according to the present invention can be applied to various laser processing of other wafers, for example, can be applied to the division of optical device wafers.

The specifications of the laser beam machine used in the following examples are as follows.
Laser light source: YVO4 laser or YAG laser
Wavelength: 355nm
Repetition frequency: 50 kHz to 100 kHz
Output: 0.3W to 4.0W
Condensing spot diameter: φ9.2 μm
Processing feed rate: 1 mm / second or more and 800 mm / second or less

Example 1
Protective film agents A, B, C, and D having the following composition were prepared. In addition, to each of the prepared protective film agents, 0.06 g of EnviroGem AD01 (produced by Air Products AIR PRODUCTS) as an antifoaming agent and 0.1 g of paraben as an antibacterial agent were added.

<Protective film agent A>
Water-soluble resin: 10 g (polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 300)
Laser light absorber: 8 g (silica surface-treated titanium oxide TTO-W-5 (Ishihara Sangyo Co., Ltd.))
Water: 80g

<Protective film agent B>
Water-soluble resin: 10 g (polyvinylpyrrolidone K-90)
Laser light absorber: 8 g (silica surface-treated titanium oxide TTO-W-5 (Ishihara Sangyo Co., Ltd.))
Water: 80g

<Protective film agent C>
Water-soluble resin: 10 g (polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 300)
Laser light absorber: 8 g (silica surface-treated zinc oxide FINEX-33W-LP2 (manufactured by Sakai Chemical Industry Co., Ltd.))
Water: 80g

<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: 80g

<Comparative protective film agent X>
Water-soluble resin: 10 g (polyvinyl alcohol having a saponification degree of 88% and a polymerization degree of 300)
Laser light absorber: 8 g (titanium oxide TKS-203 without surface treatment (manufactured by Teika))
Water: 80g
No antifoaming agent or preservative was added to the protective film agent X.

(Example 2)
The above protective film agents A to D were applied to a 150 μm thick silicon wafer having a 20 nm thick SiO ₂ passivation layer with a spinner to form a coating film. The coating film was dried, and protective films were formed at intervals of 0.5 μm from 0.5 μm to 2.5 μm in thickness on the street. The protective film was uniformly formed at all levels. Next, the silicon wafer on which the protective film was formed was mounted on a laser processing machine having the above specifications, and after laser processing, the protective film was washed away with pure water, and the periphery of laser scanning was observed.

  At all levels, there was no peeling of the passivation layer at the edge part, the burr height was low, and the adhesion of debris to the periphery could not be observed. Further, the processing width was equal to the laser spot diameter without being affected by the thickness of the coating film. Table 1 shows the evaluation results at a thickness of 1.5 μm on the street.

<Evaluation>
Unless otherwise noted, the evaluation was performed in an environment of 23 ° C. and 55% RH.
Debris: ○ Adhesion cannot be confirmed.
Δ: Slightly adhered, but usable.
× Adhered to the extent that it cannot be used.

Peeling: ○ Occurrence of film peeling cannot be confirmed.
△ Part of the film is peeled off.
× Film peeling has occurred.

Burr height: x The level at a thickness of 1.5 μm on the street of the protective film agent X was taken as x.
△ Slightly lower than X.
○ Much lower than X.

Transmittance: A protective film having a thickness of 1.5 μm was prepared on a glass substrate, and the transmittance at 355 nm was measured with an integrating sphere spectrophotometer.
○ Transmittance 35% or less
△ Transmittance over 35% to 50%
× Transmittance> 50%

(Example 3)
Example 2 The same evaluation was performed by setting the thickness of the protective film agent A on the street to 0.2 μm. The results are shown in Table 1 (A2). Moreover, the antifoamer and antiseptic | preservative were not added to the protective film agent A of Example 2, and the thickness on a street was 1.5 micrometers and performed the same evaluation (A3). The results are shown in Table 1.

(Comparative Example 1)
In the above-mentioned protective film agent A, a titanium oxide TKS-203 (manufactured by Teika Co., Ltd.) not surface-treated with an inorganic oxide described in JP-A-2005-150523 is used as a water-soluble laser light absorber, and the protective film agent X And the same evaluation as in Example 2 was performed. The film thickness was 1.5 μm. A slight surface roughness was visually observed. When the periphery of laser scanning was observed in the same manner as in Example 1, debris and film peeling were also observed, and the burr height was large. The results are shown in Table 1.

Example 4
The antiseptic effect was evaluated as follows. The protective film agent A and the protective film agent X were evaluated using the collected waste liquids. Specifically, three types of general bacteria, heterotrophic bacteria, and fungi were inoculated into 1 mL of the collected waste liquid and then cultured at 35 ° C. for 48 hours. After the cultivation, the number of colonies generated was confirmed for each of the three types of bacteria. The total number of colonies of the three types of bacteria was 15 for the protective film agent A and 900 or more for the protective film agent X.

2: Semiconductor wafer 20: Substrate 21: Laminate 22: Semiconductor chip 23: Street 24: Resin coating 25: Laser processing groove 26: Cutting groove 3: Spin coater 5: Annular frame 6: Protection tape 7: Laser processing device 71 : Chuck table of laser processing apparatus 72: laser beam irradiation means 8: cutting apparatus 81: chuck table of cutting apparatus 82: cutting means

Claims (6)

  A dicing protective film agent comprising a water-soluble resin and a laser light absorber, wherein at least one of the laser light absorbers is surface-treated with an inorganic oxide.   2. The protective film agent for dicing according to claim 1, wherein at least one of the laser light absorbers is titanium oxide or zinc oxide surface-treated with an inorganic oxide.   The protective film agent for dicing according to claim 1 or 2, wherein the inorganic oxide is silicon oxide, aluminum hydroxide, or zirconium oxide.   The protective film agent for dicing according to any one of claims 1 to 3, comprising an antifoaming agent.   The protective film agent for dicing according to any one of claims 1 to 4, comprising an antibacterial agent.   The wafer processing method using the protective film agent for dicing of any one of the said Claims 1-5.

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