Protective film agent, method for forming a protective film, and method for manufacturing a chip

Abstract

This product provides a protective film agent that prevents turbidity during storage. [Solution] A protective film agent for forming a protective film on one surface of a workpiece before processing the workpiece, comprising a solution containing a water-soluble resin, water, and a light-absorbing agent, wherein the light-absorbing agent has a flavonoid structure, a flavonol structure, or an isoflavone structure, and is contained in an amount of 52.00 parts by mass or more of the light-absorbing agent per 100 parts by mass of the water-soluble resin. The water-soluble resin is, for example, polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose, or polyoxazoline. The light-absorbing agent is, for example, α-glucosylrutin.

Description

TECHNICAL FIELD

[0001] The present invention relates to a protective film agent for forming a protective film on one surface of a workpiece before processing the workpiece, a protective film forming method for forming the protective film on one surface of the workpiece, and a chip manufacturing method for manufacturing chips by forming the protective film on one surface of a workpiece on which a plurality of devices are formed, and then dividing the workpiece along the boundaries of the plurality of devices.

BACKGROUND ART

[0002] Chips of devices such as ICs (Integrated Circuits) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by dividing a workpiece such as a wafer on which a plurality of devices are formed along the boundaries of the plurality of devices.

[0003] Examples of apparatuses used for dividing workpieces include laser processing apparatuses. This laser processing apparatus can partially remove the workpiece by, for example, irradiating the workpiece with a laser beam having a wavelength that is absorbed by the workpiece to cause laser ablation.

[0004] However, when laser ablation occurs in a workpiece, debris may scatter and adhere to the workpiece. In this case, the quality of chips obtained by dividing the workpiece may be degraded. In view of this point, it has been proposed to form a protective film on one surface of the workpiece before irradiating the workpiece with a laser beam (see, for example, Patent Document 1).

[0005] This protective film is formed by applying a protective film agent, which is a solution containing ultraviolet-absorbable α-glucosyl rutin (αGR) as a light absorber, to one surface of the workpiece, and then drying the protective film agent applied to this one surface. Thereby, it is possible to prevent debris from adhering to one surface of the workpiece when the workpiece is irradiated with a laser beam from the one surface side. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-119588 [Overview of the project] [Problems that the invention aims to solve]

[0007] The protective film agent is a solution in which various materials, including not only light absorbers but also water-soluble resins, are dissolved in water, and it may become cloudy during storage. When a protective film is formed from a cloudy protective film agent, its quality may change. In this case, the accuracy of processing the workpiece through the protective film by irradiating it with a laser beam may vary, and its reliability may be compromised.

[0008] In view of this, one aspect of the present invention aims to provide a protective film agent that is less likely to become cloudy during storage. [Means for solving the problem]

[0009] The inventors of the present invention have completed the present invention by discovering that a protective film agent prepared to contain 52.00 parts by mass or more of an absorbent having a flavonoid structure, a flavonol structure, or an isoflavone structure per 100 parts by mass of a water-soluble resin is less prone to turbidity during storage.

[0010] According to one aspect of the present invention, a protective film agent is provided for forming a protective film on one surface of a workpiece before processing the workpiece, the protective film agent being a solution containing a water-soluble resin, water, and a light absorber, wherein the light absorber has a flavonoid structure, a flavonol structure, or an isoflavone structure, and the protective film agent contains 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

[0011] Furthermore, the water-soluble resin is preferably polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose, or polyoxazoline. In addition, the light-absorbing agent is preferably having a flavonoid structure, for example, α-glucosylrutin.

[0012] Furthermore, it is preferable that the protective film agent according to one embodiment of the present invention has a metal impurity content of 100 ppb or less.

[0013] In addition, the protective film agent according to one embodiment of the present invention preferably further contains an antioxidant and / or a plasticizer. In this case, the protective film agent preferably contains 0.005% by mass or more of the antioxidant and 2.5% by mass or more of the plasticizer. Furthermore, the antioxidant is preferably L-ascorbic acid or an ascorbic acid derivative.

[0014] Another aspect of the present invention provides a protective film forming method for forming a protective film on one surface of a workpiece before processing the workpiece, comprising: applying a protective film agent, which is a solution containing a water-soluble resin, water, and a light absorber, to the surface; and forming the protective film by drying the protective film agent applied to the surface, wherein the light absorber has a flavone structure, a flavonol structure, or an isoflavone structure, and the protective film agent contains 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

[0015] According to yet another aspect of the present invention, a method for manufacturing chips is provided, which involves dividing a workpiece on which a plurality of devices are formed along the boundaries of the plurality of devices, and comprising: applying a protective film agent, which is a solution containing a water-soluble resin, water, and a photoabsorbent, to one surface of the workpiece; forming a protective film by drying the protective film agent applied to the one surface; partially removing the protective film by irradiating the workpiece from the side on which the protective film is formed with a pulsed laser beam having a wavelength absorbed by the photoabsorbent along the boundaries, thereby partially exposing the workpiece; and dividing the workpiece into a plurality of chips by performing plasma etching on the workpiece using the partially removed protective film as a mask, wherein the photoabsorbent has a flavone structure, a flavonol structure, or an isoflavone structure, and the protective film agent contains 52.00 parts by mass or more of the photoabsorbent per 100 parts by mass of the water-soluble resin.

[0016] According to yet another aspect of the present invention, a method for manufacturing chips is provided, which involves dividing a workpiece on which a plurality of devices are formed along the boundaries of the plurality of devices, and comprising: applying a protective film agent, which is a solution containing a water-soluble resin, water, and a photoabsorbent, to one surface of the workpiece; forming a protective film by drying the protective film agent applied to the one surface; and partially removing the protective film and the workpiece by irradiating the workpiece from the side on which the protective film is formed along the boundaries with a pulsed laser beam having a wavelength absorbed by the photoabsorbent and the workpiece, respectively, thereby dividing the workpiece into a plurality of chips, wherein the photoabsorbent has a flavonoid structure, a flavonol structure, or an isoflavone structure, and the protective film agent contains 52.00 parts by mass or more of the photoabsorbent per 100 parts by mass of the water-soluble resin.

[0017] Preferably, each of these multiple devices is an image sensor. [Effects of the Invention]

[0018] According to one aspect of the present invention, a protective film agent that is less prone to turbidity during storage is provided. [Brief Description of the Drawings]

[0019] [Figure 1] FIG. 1 is a flowchart schematically showing an example of a protective film forming method for forming a protective film on one surface of a workpiece before processing the workpiece. [Figure 2] FIG. 2(A) is a perspective view schematically showing an example of a workpiece before a protective film agent is applied to one surface thereof, and FIG. 2(B) is a partially enlarged cross-sectional view schematically showing the workpiece shown in FIG. 2(A). [Figure 3] FIG. 3(A) is a perspective view schematically showing the state of the application step, and FIG. 3(B) is a partially enlarged cross-sectional view schematically showing the workpiece after the protective film forming step. [Figure 4] FIG. 4 is a flowchart schematically showing an example of a chip manufacturing method for manufacturing chips by dividing a workpiece. [Figure 5] FIG. 5(A) is a perspective view schematically showing the state of the exposure step, and FIG. 5(B) is a partially enlarged cross-sectional view schematically showing the workpiece after the exposure step. [Figure 6] FIG. 6(A) is a view schematically showing an example of a plasma etching apparatus used in the dividing step, and FIG. 6(B) is a partially enlarged cross-sectional view schematically showing chips manufactured in the dividing step. [Figure 7] FIG. 7 is a flowchart schematically showing another example of a chip manufacturing method for manufacturing chips by dividing a workpiece. [Figure 8] FIG. 8(A) is an optical microscope image showing linear grooves that partially expose the workpiece by penetrating the protective film formed from the protective film agent of the Example, after the workpiece is washed with water to remove the protective film following the formation of the grooves, and FIG. 8(B) is an optical microscope image showing linear grooves that partially expose the workpiece by penetrating the protective film formed from the protective film agent of the Comparative Example, after the workpiece is washed with water to remove the protective film following the formation of the grooves. DETAILED DESCRIPTION OF EMBODIMENTS

[0020] A protective film agent according to one aspect of the present invention is a solution containing a water-soluble resin, water, and a light absorbing agent. The water-soluble resin serves as the main component of the protective film formed by applying this protective film agent to one surface of a workpiece and then drying it. The light absorbing agent absorbs a laser beam having a predetermined wavelength to cause laser ablation in the protective film formed on one surface of the workpiece.

[0021] The water-soluble resin contained in the protective film agent is, for example, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinyl alcohol introduced with a modifying group (e.g., Gohsenolx manufactured by Mitsubishi Chemical Corporation), hydroxypropyl cellulose (HPC), polyoxazoline, polyethylene glycol, polyethylene oxide, methyl cellulose, ethyl cellulose, polyacrylic acid, poly-N-vinylacetamide, polystyrene sulfonic acid, polyester, special nylon, phenol resin, methylol melamine resin, polyglycerin, or a graft polymer thereof (e.g., a product obtained by grafting polyvinylpyrrolidone onto polyvinyl alcohol). The protective film agent may also contain two or more of these water-soluble resins.

[0022] There are several types of commercially available PVA products. These products are classified according to their degree of polymerization and degree of saponification. PVA with a degree of saponification of 98.0 mol% or higher is also referred to as fully saponified. PVA with a degree of saponification of 98.0 mol% or lower but 90.0 mol% or higher is also referred to as intermediate saponified. PVA with a degree of saponification of 90.0 mol% or lower but 78.5 mol% or higher is also referred to as partially saponified. For example, a product with a degree of polymerization of around 500 and a degree of saponification of around 88 is labeled as "PVA 5-88". When using PVA in protective film agents, it is preferable to use a product with a degree of polymerization of 300 to 3000 and a degree of saponification of 90.0 mol% or lower. This is because, if the degree of polymerization of PVA with a degree of saponification of 90.0 mol% or less is less than 300, it becomes difficult to manufacture the protective film agent because a large amount of PVA needs to be mixed in. Furthermore, if the degree of polymerization of the PVA exceeds 3000, the viscosity of the protective film agent becomes high, making it difficult to transport.

[0023] Furthermore, there are several types of PVP products available on the market. These products are classified according to the K value, which is calculated by applying the relative viscosity value (at 25°C) measured by a capillary viscometer to the Fikentscher viscosity formula. For example, products with K values ​​of around 30, around 60, and around 90 are labeled "PVP K-30," "PVP K-60," and "PVP K-90," respectively. Also, products with a K value of around 85, such as those from Nippon Shokubai Co., Ltd., are labeled "PVP K-85N." It is preferable to use PVP with a K value of 50 or higher in protective film agents. This is because if the K value of the PVP is less than 50, it is necessary to mix a large amount of PVP into the protective film agent, making its manufacture difficult and increasing the likelihood of quality changes such as a decrease in viscosity and / or discoloration of the protective film agent.

[0024] Furthermore, there are multiple types of commercially available HPC products. HPC is classified according to its molecular weight. For example, Nippon Soda Co., Ltd. produces HPC with molecular weights of around 40,000, around 100,000, and around 140,000, and these are named "HPC-SSL," "HPC-SL," and "HPC-L," respectively. Similarly, Ashland Co., Ltd. produces HPC with molecular weights of around 80,000, around 95,000, and around 140,000, and these are named "Klucel-E," "Klucel-L," and "Klucel-J," respectively. When using HPC in a protective film agent, it is preferable to use a product with a molecular weight of 80,000 or higher. This is because, if the molecular weight of HPC is less than 80,000, it becomes necessary to mix a large amount of HPC into the protective film, making its manufacture difficult and increasing the likelihood of quality changes such as a decrease in the viscosity of the protective film agent and / or the occurrence of turbidity.

[0025] The water contained in the protective film agent may be tap water or similar, but from the viewpoint of reducing the content of metal impurities such as sodium (Na) in the protective film agent, pure water is preferable.

[0026] The light-absorbing agent contained in the protective film agent has a flavonoid structure, a flavonol structure, or an isoflavone structure. In particular, it is preferable that the light-absorbing agent has a flavonoid structure and further has a sugar chain. For example, this light-absorbing agent is α-glucosylrutin (αGR). Note that the flavonoid portion of αGR is hydrophobic, while the other portions are strongly hydrophilic.

[0027] The protective film agent is prepared to contain at least 52.00 parts by mass of a light absorber per 100 parts by mass of water-soluble resin. This prevents the protective film agent from becoming cloudy during storage. The reason for this is explained below.

[0028] When the amount of water-soluble resin that dissolves in water increases to the point where the amount of light absorbent is less than 52.00 parts by mass per 100 parts by mass of water-soluble resin, the light absorbent, which has strong hydrophilicity overall (e.g., αGR), interacts with the water-soluble resin dissolved in water, making the water-soluble resin more prone to aggregation. On the other hand, when the protective film agent is prepared to contain 52.00 parts by mass or more of light absorbent per 100 parts by mass of water-soluble resin, such aggregation of the water-soluble resin is suppressed, and therefore the resulting turbidity of the protective film agent is also suppressed.

[0029] Furthermore, it is preferable that the protective film agent be prepared to contain 300 parts by mass or less of light absorbent per 100 parts by mass of water-soluble resin. This is because if the protective film agent is prepared to contain more than 300 parts by mass of light absorbent per 100 parts by mass of water-soluble resin, the water-soluble resin and the light absorbent may separate when forming the protective film, which may reduce the accuracy of processing the workpiece through this protective film.

[0030] Furthermore, the protective film agent may contain an organic solvent. For example, the protective film agent may be prepared so that the organic solvent content is 3 to 18% by mass. In this case, aggregation of the water-soluble resin and / or light absorber is suppressed, improving the stability of the protective film agent, and the surface tension of the protective film agent is reduced, making it easier for the protective film agent to be applied to one surface of the workpiece so that the surface becomes flat.

[0031] Examples of this organic solvent include methyl alcohol, ethyl alcohol, isopropyl alcohol, esters, alkylene glycol monoalkyl ethers, alkylene glycols, or alkylene glycol monoalkyl ether acetates. Propylene glycol monomethyl ether (PGME) is preferred as the alkylene glycol monoalkyl ether. Furthermore, the protective film agent may contain two or more organic solvents.

[0032] Furthermore, the protective film agent may also contain an antioxidant. For example, the protective film agent may be prepared so that the antioxidant content is 0.005% by mass or more. In this case, structural changes in the light absorber are suppressed, and its stability is improved. As a result, discoloration of the protective film agent during storage can be suppressed. It is also preferable that the protective film agent be prepared so that the antioxidant content is 0.05% by mass or less. This is because if the protective film agent is prepared so that the antioxidant content exceeds 0.05% by mass, it may become difficult to suppress discoloration of the protective film agent during storage.

[0033] Examples of antioxidants include L-ascorbic acid (ASC) (so-called vitamin C) or ascorbic acid derivatives. Furthermore, the protective film agent may contain two or more antioxidants.

[0034] Furthermore, the protective film agent may also contain a plasticizer. For example, the protective film agent may be prepared so that the plasticizer content is 2.50% by mass or more. In this case, the thickness of the protective film agent applied to one surface of the workpiece increases, and structural changes of the light absorber are suppressed, improving its stability. Furthermore, in this case, the accuracy when processing the workpiece by plasma etching using the protective film formed from the protective film agent as a mask is improved (see Patent Document 1, etc.). In addition, it is preferable that the protective film agent be prepared so that the plasticizer content is 15% by mass or less. This is because if the protective film agent is prepared so that the plasticizer content exceeds 15% by mass, the protective film formed from this protective film agent becomes too soft, which may reduce the accuracy when processing the workpiece through this protective film.

[0035] Examples of this plasticizer include those described in Patent Document 1. Trimethylolpropane (TMP) is preferred as this plasticizer. Furthermore, the protective film agent may contain two or more types of plasticizers.

[0036] In addition to antioxidants and plasticizers, other components may also be included. Examples of other components include other water-soluble light-absorbing agents other than αGR (cinnamic acid compounds, benzophenone compounds, or anthraquinone compounds), basic compounds such as ammonia compounds or amine compounds, acidic compounds such as formic acid or acetic acid, pH adjusters, preservatives, defoamers, surfactants, leveling agents, or UV curing agents (reactive monomers and photopolymerization initiators). Furthermore, the protective film agent may contain two or more of these components.

[0037] The protective film agent is prepared, for example, by filtering a solution obtained by dissolving a water-soluble resin in water and then adding a light-absorbing agent. Furthermore, antioxidants and / or plasticizers may be added to the solution after dissolving the water-soluble resin but before dissolving the light-absorbing agent. In addition, organic solvents may be dissolved in the solution after dissolving the water-soluble resin and light-absorbing agent but before filtering.

[0038] Furthermore, ion exchange may be performed on the solution after all intentionally added components have been dissolved and before filtration. In this case, the content of metal impurities in the protective film agent can be reduced to, for example, 100 ppb or less. As a result, discoloration of the protective film agent during storage can be suppressed.

[0039] Figure 1 is a schematic flowchart illustrating an example of a protective film formation method for forming a protective film on one surface of a workpiece before processing it. In this method, first, a protective film agent is applied to one surface of the workpiece (application step S1).

[0040] Figure 2(A) is a schematic perspective view showing an example of a workpiece (workpiece 11) before a protective film is applied to one surface, and Figure 2(B) is a schematic enlarged cross-sectional view of the workpiece 11. The workpiece 11 is a disc-shaped wafer with an orientation flat 11a formed on its outer edge to indicate the crystal orientation.

[0041] Specifically, the workpiece 11 has a substrate 13 made of silicon (Si) or silicon carbide (SiC), and a portion of the surface (top surface) of the substrate 13 is provided with an impurity region doped with impurities. In addition, a functional layer 15 containing multiple insulating films and multiple conductive films is provided on the surface of the substrate 13.

[0042] Furthermore, the workpiece 11 is divided into multiple regions by streets 17 arranged in a grid pattern. The linearly extending portions of these streets 17 are also called division lines. The device 19 is composed of a portion of the substrate 13 (impurity regions and intrinsic semiconductor regions where no impurities are present) and a portion of the functional layer 15 (insulating film and conductive film) contained within each of the multiple regions.

[0043] In other words, multiple devices 19 are provided on one side of the workpiece 11 in a matrix-like manner, that is, their boundaries extend in a grid-like manner. The functional layer 15 in the region where the devices 19 are provided is slightly thicker than the functional layer 15 of the street 17. That is, the devices 19 are convex portions that protrude slightly above the street 17.

[0044] Furthermore, the workpiece 11 may be integrated with the ring frame via a support member fixed to the other side. This support member is, for example, a tape containing an adhesive layer that adheres to the other side of the workpiece 11. Alternatively, the support member may be a sheet without an adhesive layer. In this case, the workpiece 11 and the support member are fixed together, for example, by heat-pressing.

[0045] Figure 3(A) is a schematic perspective view showing the coating step S1. The coating step S1 is carried out in a spin coater 2. This spin coater 2 is equipped with a chuck table 4 having a circular top surface.

[0046] The underside of the chuck table 4 is connected via a spindle 6 to a rotational drive source (not shown) including a motor. When this rotational drive source is operated, the chuck table 4 rotates around a straight line running vertically through the center of its upper surface as the axis of rotation.

[0047] The chuck table 4 has a frame with a circular recess formed on its upper surface in a plan view, and a disc-shaped porous plate (not shown) fixed in this recess. This porous plate is made of a porous material and can selectively communicate with a suction source (not shown) including an ejector or an air supply source including an air pump via a flow path (not shown) formed in the frame and spindle 6.

[0048] When this channel is connected to a suction source and the suction source is operated, the pressure in this channel becomes negative, and a suction force acts on the space near the top surface of the porous plate. Conversely, when this channel is replaced with an air supply source and the air supply source is operated, the pressure in this channel returns to normal pressure, and the suction force acting on the space near the top surface of the porous plate disappears.

[0049] Above the chuck table 4, a nozzle 8 is provided for supplying the protective film agent 1 toward the vicinity of the center of the upper surface of the porous plate. This nozzle 8 is connected via piping (not shown) or the like to a solution supply source (not shown) which includes a liquid transfer pump and a tank for storing the protective film agent 1.

[0050] In coating step S1, first, the workpiece 11 is placed on the chuck table 4 either directly or via a support member, with one side facing upwards and covering the porous plate. Next, a suction source communicating with the porous plate is activated. This applies a suction force directly or indirectly to the workpiece 11, holding it on the upper surface of the chuck table 4.

[0051] Next, the solution supply source is operated so that the protective film agent 1 is dropped from the nozzle 8 onto one side of the workpiece 11. Then, the rotation drive source is operated so that the chuck table 4 is rotated via the spindle 6. This performs a so-called spin coating, in which the protective film agent 1 is applied to one side of the workpiece 11 so as to cover its entire surface.

[0052] After performing the coating step S1, a protective film is formed by drying the protective film agent 1 applied to one surface of the workpiece 11 (protective film formation step S2). Figure 3(B) is a schematic enlarged cross-sectional view of the workpiece 11 after the protective film formation step S2.

[0053] In this protective film formation step S2, the protective film agent 1 may be air-dried, or the protective film agent 1 may be dried while heating and / or dehumidifying the atmosphere. As a result, a protective film 3 is formed on one surface of the workpiece 11.

[0054] Figure 4 is a schematic flowchart illustrating an example of a chip manufacturing method in which a protective film 3 is formed on one surface of the workpiece 11, and then the workpiece 11 is divided along the street 17 (i.e., the boundary between multiple devices 19) to produce a chip.

[0055] In this method, after performing the coating step S1 and the protective film formation step S2, the protective film 3 is partially removed by irradiating the workpiece 11 with a laser beam from one side, thereby partially exposing the workpiece 11 (exposure step S3). Figure 5(A) is a schematic perspective view showing the exposure step S3, and Figure 5(B) is a schematic partially enlarged cross-sectional view showing the workpiece 11 after the exposure step S3.

[0056] Note that the directions indicated by arrow X (X direction) and arrow Y (Y direction) in Figure 5(A) are perpendicular directions in the horizontal plane, and the direction indicated by arrow Z (Z direction) is perpendicular to the X direction and the Y direction, respectively (vertical direction).

[0057] The exposure step S3 is performed in the laser processing apparatus 10. This laser processing apparatus 10 includes a chuck table 12 having a circular top surface. The chuck table 12 is connected to a rotational drive source (not shown), including a motor, via a spindle (not shown). When this rotational drive source is operated, the chuck table 12 rotates with a straight line along the Z direction passing through the center of its top surface as the axis of rotation.

[0058] The chuck table 12 has a frame with a circular recess formed on its upper surface in a plan view, and a disc-shaped porous plate (not shown) fixed in this recess. This porous plate is made of a porous material and can selectively communicate with a suction source (not shown) including an ejector or an air supply source including an air pump via a flow path (not shown) formed in the frame and spindle.

[0059] When this channel is connected to a suction source and the suction source is operated, the pressure in this channel becomes negative, and a suction force acts on the space near the top surface of the porous plate. Conversely, when this channel is replaced with an air supply source and the air supply source is operated, the pressure in this channel returns to normal pressure, and the suction force acting on the space near the top surface of the porous plate disappears.

[0060] Furthermore, the underside of the chuck table 12 is connected to an X-direction movement mechanism (not shown) and a Y-direction movement mechanism (not shown), each including, for example, a ball screw. When the X-direction movement mechanism is operated, the chuck table 12 moves along the X-direction. When the Y-direction movement mechanism is operated, the chuck table 12 moves along the Y-direction.

[0061] A head 16 of the irradiation unit 14 is provided above the chuck table 12. The irradiation unit 14 has a laser oscillator (not shown). This laser oscillator has, for example, Nd:YAG as the laser medium and generates a pulsed laser beam with a wavelength (e.g., 355 nm) that is absorbed by the absorbent contained in the protective film 3.

[0062] The laser beam is then guided to the head 16 via an optical system including lenses and mirrors housed in the housing 18, and emitted directly downwards from the head 16. The irradiation unit 14 sets the repetition frequency of the laser beam to, for example, 5 kHz to 50,000 kHz, its pulse width to, for example, 10 fs to 300 ns, its output to, for example, 0.01 W to 100.0 W, and its beam width (spot diameter) at the focal point to, for example, 1 μm to 100 μm.

[0063] Furthermore, a camera 20 is provided on the side of the head 16. This camera 20 includes, for example, a light source such as an LED (Light Emitting Diode) that emits light having a wavelength that penetrates the protective film 3, an objective lens, and an image sensor such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and is capable of imaging the area directly beneath it.

[0064] Furthermore, the housing 18 is connected to a Z-axis movement mechanism (not shown), which includes, for example, a ball screw. When this Z-axis movement mechanism is operated, the head 16, housing 18, and camera 20 move along the Z-axis.

[0065] In the exposure step S3, first, the workpiece 11 is placed on the chuck table 12 either directly or via a support member, so that the protective film 3 faces upward and covers the porous plate. Next, the suction source communicating with the porous plate is activated. This applies a suction force directly or indirectly to the workpiece 11, holding it on the upper surface of the chuck table 12.

[0066] Next, the camera 20 captures an image of one side of the workpiece 11. Then, referring to the image formed by this capture, the rotational drive source rotates the chuck table 12 via the spindle so that some of the multiple division lines included in the street 17 are parallel to the X direction, and the remainder are parallel to the Y direction.

[0067] Next, the Z-direction movement mechanism raises and lowers the head 16 together with the housing 18 so that the focal point of the laser beam emitted from the head 16 is positioned at a height corresponding to the height of the protective film 3. Then, the X-direction movement mechanism and / or Y-direction movement mechanism move the chuck table 12 so that a specific division line included in the street 17 is positioned in the X-direction or the opposite direction relative to the head 16 in a plan view.

[0068] Next, while operating the irradiation unit 14 so that a laser beam is emitted from the head 16, the X-direction movement mechanism moves the chuck table 12 along the X-direction so that the laser beam passes from one end to the other in the X-direction of the protective film 3. As a result, laser ablation occurs in the portion of the protective film 3 that is irradiated with the laser beam, and the portion of the protective film 3 that overlaps with the planned division line is removed.

[0069] The above operation is then repeated until laser ablation occurs throughout the entirety of street 17. As a result, the portion of the protective film 3 that overlaps with street 17 is removed, and the workpiece 11 is partially exposed.

[0070] After the exposure step S3 is performed, the workpiece 11 is divided into multiple chips by plasma etching using the protective film 3 as a mask (division step S4). Figure 6(A) is a schematic diagram showing an example of a plasma etching apparatus (plasma etching apparatus 22) used in the division step S4.

[0071] The plasma etching apparatus 22 has a chamber 24 made of a conductive material and grounded. The chamber 24 has an inlet / outlet 24a for loading the workpiece 11 into it and for unloading the workpiece 11 from it.

[0072] The loading / unloading port 24a is provided with a gate valve 26 that can either block or allow communication between the internal space and the external space of the chamber 24. The chamber 24 also has an exhaust port 24b for exhausting its internal space.

[0073] This exhaust port 24b is connected to an exhaust device 30 such as a vacuum pump via piping 28, etc. Furthermore, a support member 32 is provided on the inner surface of the chamber 24, and this support member 32 supports the table 34.

[0074] An electrostatic chuck (not shown) is provided on the top of the table 34. Inside the table 34, a disc-shaped electrode 34a is provided, located below the electrostatic chuck. This electrode 34a is connected to the high-frequency power supply 38 via a matching unit 36.

[0075] Furthermore, a disc-shaped opening is formed in the chamber 24 at a position opposite the upper surface of the table 34, and a gas ejection head 42 is provided in this opening, supported by the chamber 24 via a bearing 40. This gas ejection head 42 is made of a conductive material and is connected to a high-frequency power supply 46 via a matching unit 44.

[0076] Furthermore, a cavity (gas diffusion space) 42a is formed inside the gas ejection head 42. In addition, a plurality of gas outlets 42b are formed in the inner part of the gas ejection head 42 (for example, the lower part) that connect the gas diffusion space 42a with the internal space of the chamber 24. In addition, two gas supply ports 42c and 42d are formed in the outer part of the gas ejection head 42 (for example, the upper part) for supplying a predetermined gas to the gas diffusion space 42a.

[0077] Furthermore, gas supply port 42c is connected via piping 48a, etc., to a gas supply source 50a that supplies, for example, carbon fluoride-based gases such as C4F8 and / or sulfur fluoride-based gases such as SF6. Also, gas supply port 42d is connected via piping 48b, etc., to a gas supply source 50b that supplies, for example, inert gases such as Ar and O2 gas.

[0078] In the splitting step S4, the workpiece 11 is split along the boundaries of multiple devices 19, for example, by the so-called Bosch process. Specifically, first, the workpiece 11 is brought onto the table 34 with the protective film 3, which acts as a mask, facing upwards, while the gate valve 26 connects the internal and external spaces of the chamber 24.

[0079] Next, the workpiece 11 is held by the electrostatic chuck of the table 34. Then, the internal space of the chamber 24 is evacuated by the exhaust device 30 to create a vacuum. Then, isotropic plasma etching, sidewall protective film formation, and anisotropic plasma etching are repeatedly performed alternately until the workpiece 11 is divided along the boundaries of the multiple devices 19.

[0080] Specifically, isotropic plasma etching is performed, for example, by supplying a gas containing SF6 from a gas supply source 50a to the internal space of the chamber 24, and supplying Ar gas from a gas supply source 50b, while providing high-frequency power from a high-frequency power supply 46 to the gas ejection head 42. As a result, the workpiece 11 exposed at the boundaries of multiple devices 19 is isotropically etched by F-based radicals and the like generated in the internal space of the chamber 24.

[0081] Furthermore, the formation of the sidewall protective film is carried out, for example, by supplying a gas containing C4F8 from a gas supply source 50a to the internal space of the chamber 24, and supplying a gas containing Ar from a gas supply source 50b, while providing high-frequency power from a high-frequency power supply 46 to the gas ejection head 42. As a result, CF radicals are deposited on the surface of the workpiece 11 exposed at the boundaries of the multiple devices 19 (specifically, the surface newly exposed by isotropic plasma etching), forming a film containing carbon fluoride.

[0082] Alternatively, the formation of the sidewall protective film may be carried out by supplying a gas containing O2 and Ar from a gas supply source 50b to the internal space of the chamber 24, and then supplying high-frequency power from a high-frequency power supply 46 to the gas ejection head 42. As a result, the material of the workpiece 11 (e.g., substrate 13) exposed at the boundaries of the multiple devices 19 reacts with oxygen ions, and an oxide film is formed on the surface of the workpiece 11.

[0083] Furthermore, anisotropic plasma etching is performed, for example, by supplying a gas containing SF6 from a gas supply source 50a to the internal space of the chamber 24, and supplying Ar gas from a gas supply source 50b, while simultaneously supplying high-frequency power from a high-frequency power supply 38 to an electrode 34a located inside the table 34, and supplying high-frequency power from a high-frequency power supply 46 to a gas ejection head 42. As a result, F-based ions and the like generated in the internal space of the chamber 24 are accelerated toward the table 34, causing the workpiece 11 to be etched anisotropically.

[0084] Figure 6(B) is a schematic, partially enlarged cross-sectional view showing the chips manufactured in the division step S4. When the workpiece 11 is divided along the boundaries of the multiple devices 19, multiple chips 5 are manufactured.

[0085] In addition, in the division step S4, the workpiece 11 may be divided along the boundaries of the multiple devices 19 by performing only anisotropic plasma etching, without performing isotropic plasma etching and forming a sidewall protective film.

[0086] Figure 7 is a schematic flowchart illustrating another example of a chip manufacturing method, in which a protective film 3 is formed on one surface of the workpiece 11, and then the workpiece 11 is divided along the street 17 (i.e., the boundary between multiple devices 19) to produce a chip.

[0087] In this method, after performing the coating step S1 and the protective film formation step S2, the protective film 3 and the workpiece 11 are partially removed by irradiating the workpiece 11 with a laser beam from one side, thereby dividing the workpiece 11 into multiple chips 5 (dividing step S5).

[0088] This splitting step S5 is carried out in the same manner as the exposure step S3, except that it utilizes a laser beam having a wavelength that is absorbed not only by the light absorber contained in the protective film 3 but also by the workpiece 11 (for example, silicon or silicon carbide, which is the material of the substrate 13), and that the focal point is positioned at a height corresponding to the height of the substrate 13. Therefore, a detailed explanation of the splitting step S5 is omitted.

[0089] Furthermore, the structures and methods of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. [Examples]

[0090] The following describes an experiment (Experiment 1) conducted to investigate the susceptibility of protective film agents, which are embodiments of the present invention, to turbidity. In Experiment 1, protective film agents of Examples 1 to 16 were prepared, each containing various materials in the proportions (mass%) shown in Tables 1 to 5 below. The "Light Absorber / Water-Soluble Resin" column in Tables 1 to 4 also shows the ratio of light absorber to water-soluble resin for each of the protective film agents of Examples 1 to 16. For example, the protective film agent of Example 1 contains 128.21 parts by mass of light absorber per 100 parts by mass of water-soluble resin. [Table 1] [Table 2] [Table 3] [Table 4]

[0091] Specifically, a water-soluble resin powder (one or two of the following: polyvinyl alcohol (PVA 5-88) with a degree of polymerization of around 500 and a degree of saponification of around 88; polyvinylpyrrolidone (PVP K-30, 60, 85N, 90) with a K value of around 30, 60, 85, or 90; or hydroxypropyl cellulose (HPC-L) with a molecular weight of around 140,000) was dissolved in water, and then an antioxidant (L-ascorbic acid (ASC)) and / or a plasticizer (trimethylolpropane (TMP)) was added as needed, followed by the addition of a light absorber (α-glucosylrutin (αGR)) to prepare the solution. Then, an organic solvent (propylene glycol monomethyl ether (PGME)) was further dissolved in this solution, and after ion exchange was performed to reduce the metal impurity content to 100 ppb or less, the protective film agents of Examples 1 to 16 were obtained by filtration.

[0092] In addition, protective film agents for Comparative Examples 1 to 6 were prepared, each containing various materials in the proportions (mass%) shown in Tables 5 and 6 below. [Table 5] [Table 6]

[0093] Specifically, a water-soluble powdered resin (PVA 5-88 or PVP K-60) was dissolved in water. Then, an antioxidant (ASC) was added. In addition, a light-absorbing agent (αGR) was dissolved in an organic solvent (PGME). Then, the two solutions, namely the solution containing water, water-soluble resin, and antioxidant, and the solution containing the organic solvent and light-absorbing agent, were mixed, and after ion exchange was performed to reduce the metal impurity content to 100 ppb or less, the mixture was filtered to obtain the protective film agents of Comparative Examples 1 to 6.

[0094] Then, the presence or absence of turbidity in each of the protective film agents of Examples 1-16 and Comparative Examples 1-6 was evaluated immediately after preparation and after storage for one month. This evaluation was performed by combining visual inspection and measurement using a spectrophotometer (Shimadzu UV-2700 UV-Vis spectrophotometer). Specifically, first, the presence or absence of turbidity in each protective film agent was evaluated visually. Then, for protective film agents that were evaluated as having no turbidity visually, if the absorbance at a predetermined wavelength in the visible light range of the absorption spectrum obtained by measuring with a spectrophotometer was above a threshold, it was evaluated as having turbidity; if it was below the threshold, it was evaluated as having no turbidity. Table 7 below shows the results of this evaluation. [Table 7]

[0095] Based on this evaluation, it was found that in Comparative Examples 1 to 6, each of the protective film agents containing 40.29 parts by mass or less of light absorbent per 100 parts by mass of water-soluble resin, turbidity occurred within one month of preparation. However, in Examples 1 to 16, each of the protective film agents containing 52.03 parts by mass or more of light absorbent per 100 parts by mass of water-soluble resin, turbidity did not occur even after one month of storage. Therefore, it is recognized that by preparing the protective film agent to contain 52.00 parts by mass or more of light absorbent per 100 parts by mass of water-soluble resin, the protective film agent becomes less likely to become turbid during storage.

[0096] Next, we will describe an experiment (Experiment 2) conducted to investigate the content of antioxidants that are excellent in improving the stability of protective film agents, which are embodiments of the present invention. In Experiment 2, first, four protective film agents containing antioxidants in the proportions (mass%) shown in Table 8 below were prepared. Specifically, the protective film agent of Example 10 described in Table 3 above, a protective film agent containing various materials in the same proportions as the protective film agent of Example 10 except that it does not contain antioxidants, and a protective film agent containing various materials in the same proportions as the protective film agent of Example 10 except that the antioxidant content is 0.005 mass% or 0.030 mass%. [Table 8]

[0097] For each of the four protective film agents, the initial absorbance to light with a wavelength of 470 nm and the absorbance to light with a wavelength of 470 nm after storage for 1 month, 2 months, 4 months, 6 months, and 9 months while maintaining the ambient temperature at 23°C were measured. The numbers listed in the "1 month storage," "2 months storage," "4 months storage," "6 months storage," and "9 months storage" columns of Table 8 above represent the values ​​obtained by dividing the absorbance at 1 month, 2 months, 4 months, 6 months, and 9 months storage by the initial absorbance, respectively. Based on these measurements, it is considered preferable to prepare the protective film agent to contain 0.005% by mass or more of antioxidant, from the viewpoint of improving the stability of the protective film agent.

[0098] Next, we will describe an experiment (Experiment 3) conducted to investigate the content of plasticizers that are excellent at improving the stability of protective film agents. In Experiment 3, four protective film agents were prepared, each containing various materials in the proportions (mass%) shown in Table 9 below. [Table 9]

[0099] For each of the four protective film agents, the initial absorbance to light with a wavelength of 470 nm and the absorbance to light with a wavelength of 470 nm after one month of storage while maintaining the ambient temperature at 23°C were measured. The numbers listed in the "1 month storage" column of Table 8 above represent the percentage change (%) from the initial absorbance to the absorbance after one month of storage. Based on these measurements, it is considered preferable to prepare the protective film agents to contain 2.5% by mass or more of plasticizer from the viewpoint of improving the stability of the protective film agents.

[0100] The pH of each of the protective film agents in Examples 1 to 16 was between 3.0 and 3.5. From the viewpoint of suppressing bacterial growth in the protective film agent, it is preferable that the pH of the protective film agent be between 2.5 and 4.0. On the other hand, depending on the type of device formed on the workpiece to which the protective film agent is applied, a protective film agent with a pH of 3.0 to 3.5, i.e., a relatively strong acid, may adversely affect the device.

[0101] From the perspective of suppressing adverse effects on the device, the protective film agent may be prepared so that its pH is between 4.0 and 8.0. For example, by adding a pH adjusting agent such as an amine compound or an ammonium compound to each of the protective film agents of Examples 1 to 16, the pH of each protective film agent may be shifted from between 3.0 and 3.5 to 4.0 and 8.0.

[0102] However, if the pH of the protective film agent is between 4.0 and 8.0, bacteria may be more likely to proliferate in the protective film agent. Such bacterial growth can be suppressed, for example, by adding benzoic acid or paraben compounds to the protective film agent.

[0103] Next, we will describe an experiment (Experiment 4) conducted to investigate the quality of the protective film formed from the protective film agent, which is an embodiment of the present invention. In Experiment 4, first, we prepared the protective film agent of Example 11 described in Table 3 above, and the protective film agent of Comparative Example 7, which contains ferulic acid (FA) as the light absorber instead of αGR, and contains various materials in the proportions (mass%) shown in Table 10 below. [Table 10]

[0104] Furthermore, diluted solution A was prepared by diluting the supernatant liquid collected from the protective film agent of Example 11 200 times, and diluted solution B was prepared by diluting the supernatant liquid collected from the protective film agent of Comparative Example 7 200 times. The absorbances of diluted solutions A and B were then measured. This measurement was performed using a UV-2700 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation. Table 11 below shows the absorbances of diluted solutions A and B at a wavelength of 355 nm. [Table 11]

[0105] Then, a protective film (first protective film) was formed by applying the protective film agent of Example 11 to one surface of the workpiece (first workpiece) and drying it, and a protective film (second protective film) was formed by applying the protective film agent of Comparative Example 7 to one surface of the workpiece (second workpiece) and drying it.

[0106] Each protective film was formed using a spin coating method. Specifically, the protective coating agent was supplied to one surface of the workpiece, the workpiece was rotated until the entire surface was covered with the protective coating agent, and then the protective coating agent was dried. The conditions for the spin coating method and the thickness of the formed protective film are shown in Table 12 below. [Table 12]

[0107] Furthermore, by irradiating each protective film with a laser beam having a wavelength absorbed by αGR and FA, linear grooves were formed that penetrated each protective film and partially exposed each workpiece. The processing conditions (laser beam irradiation conditions) at this time were as follows. Beam size: 65 x 5 μm Wavelength: 355nm Output: 5~10W Frequency: 100~1000kHz Feed rate: 500~1000mm / s Number of passes: 10-20 passes

[0108] Figure 8(A) is an optical microscope image showing a groove after the first workpiece has been washed with water to form a straight groove that penetrates the first protective film and partially exposes the first workpiece, and then the first protective film has been removed. Figure 8(B) is an optical microscope image showing a groove after the second workpiece has been washed with water to form a straight groove that penetrates the second protective film and partially exposes the second workpiece, and then the second protective film has been removed.

[0109] Experiment 4 revealed that when a laser beam was irradiated onto a second workpiece to form grooves through a protective film formed from the protective film agent of Comparative Example 7, the portion of the second workpiece near the grooves discolored (see Figure 8(B)). In contrast, when a laser beam was irradiated onto a first workpiece to form grooves through a protective film formed from the protective film agent of Example 11, discoloration of the portion of the first workpiece near the grooves was suppressed (see Figure 8(A)). In other words, based on Experiment 4, it is recognized that the protective film agent of Example 11 can form a higher quality protective film compared to the protective film agent of Comparative Example 7.

[0110] Furthermore, we also evaluated laser burn on workpieces with multiple image sensors formed on one side (specifically, burn on the workpiece due to scattered light during laser processing).

[0111] A protective film (third protective film) was formed by applying the protective film agent of Example 11 to one surface of a workpiece (third workpiece) on which multiple image sensors are formed on one surface and drying it, and a protective film (fourth protective film) was formed by applying the protective film agent of Comparative Example 7 to one surface of a workpiece (fourth workpiece) on which multiple image sensors are formed on one surface and drying it.

[0112] Each protective film was formed using the spin coating method. The conditions for the spin coating method and the thickness of the formed protective films are shown in Table 13 below. [Table 13]

[0113] Furthermore, by irradiating each protective film with a laser beam having a wavelength absorbed by αGR and FA, linear grooves were formed that penetrated each protective film and partially exposed each workpiece. The processing conditions (laser beam irradiation conditions) at this time were as follows. Beam size: 65 x 5 μm Wavelength: 355nm Output: 5~10W Frequency: 100~1000kHz Feed rate: 500~1000mm / s Number of passes: 10-20 passes

[0114] When a laser beam was irradiated onto the fourth workpiece to form grooves through a protective film formed from the protective film agent of Comparative Example 7, many laser burns were observed in the portion of the fourth workpiece near the grooves. In contrast, when a laser beam was irradiated onto the third workpiece to form grooves through a protective film formed from the protective film agent of Example 11, no laser burns were observed in the portion of the third workpiece near the grooves. It is recognized that laser burns on the workpiece can be prevented by forming a protective film from a protective film agent in which the absorbent is αGR and has a high content of αGR (i.e., has high absorbance relative to the wavelength of the laser beam).

[0115] Furthermore, the structures and methods of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. [Explanation of Symbols]

[0116] 1: Protective film agent 2: Spin Coater 3:Protective film 4: Chuck Table 5: Tip 6: Spindle 8: Nozzle 11: Workpiece (11a: Orientation flat) 10: Laser processing equipment 12: Chuck Table 13: Circuit board 14: Irradiation Unit 15: Functional Layer 16: Head 17: Street 18: Housing 19: Device 20: Camera 22: Plasma etching equipment 23: Frame 24: Chamber (24a: Inlet / Outlet, 24b: Exhaust Port) 25: 1st passage 26: Gate valve 27:Protective film 28: Piping 29:Second passageway 30: Exhaust system 31: Tip 32: Support member 34: Table (32a: Electrode) 36: Matching box 38: High frequency power supply 40: Bearing 42: Gas ejection head (40a: Gas diffusion space, 40b: Gas outlet, 40c, 40d: Gas supply port) 44: Matching box 46:High frequency power supply 48a, 48b: Piping 50a, 50b: Gas supply source

Claims

1. A protective film agent for forming a protective film on one surface of a workpiece before processing the workpiece, It is a solution containing a water-soluble resin, water, and a light-absorbing agent. The light-absorbing agent has a flavonoid structure, a flavonol structure, or an isoflavone structure. A protective film agent containing 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

2. The protective film agent according to claim 1, wherein the water-soluble resin is polyvinyl alcohol, polyvinylpyrrolidone, hydroxypropyl cellulose, or polyoxazoline.

3. The light-absorbing agent is a protective film agent according to claim 1, having a flavonoid structure.

4. The protective film agent according to claim 3, wherein the light-absorbing agent is α-glucosylrutin.

5. The protective film agent according to claim 1, wherein the content of metal impurities is 100 ppb or less.

6. A protective film agent according to any one of claims 1 to 5, further comprising an antioxidant and / or a plasticizer.

7. The antioxidant content is 0.005% by mass or more. The protective film agent according to claim 6, wherein the content of the plasticizer is 2.5% by mass or more.

8. The protective film agent according to claim 6, wherein the antioxidant is L-ascorbic acid or an ascorbic acid derivative.

9. A method for forming a protective film, which involves forming a protective film on one surface of a workpiece before processing the workpiece, A protective film agent, which is a solution containing a water-soluble resin, water, and a light-absorbing agent, is applied to the surface. The protective film is formed by drying the protective film agent applied to the surface, The light-absorbing agent has a flavonoid structure, a flavonol structure, or an isoflavone structure. A method for forming a protective film, wherein the protective film agent contains 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

10. A method for manufacturing chips, which involves dividing a workpiece on which multiple devices are formed along the boundaries of the multiple devices to produce chips, A protective film agent, which is a solution containing a water-soluble resin, water, and a light-absorbing agent, is applied to one surface of the workpiece. A protective film is formed by drying the protective film agent applied to the surface, By irradiating the workpiece with a pulsed laser beam having a wavelength absorbed by the light absorber along the boundary from the side on which the protective film is formed, the protective film is partially removed and the workpiece is partially exposed. The method comprises dividing the workpiece into multiple chips by performing plasma etching on the workpiece using the partially removed protective film as a mask, The light-absorbing agent has a flavonoid structure, a flavonol structure, or an isoflavone structure. A method for manufacturing chips, wherein the protective film agent contains 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

11. A method for manufacturing chips, which involves dividing a workpiece on which multiple devices are formed along the boundaries of the multiple devices to produce chips, A protective film agent, which is a solution containing a water-soluble resin, water, and a light-absorbing agent, is applied to one surface of the workpiece. A protective film is formed by drying the protective film agent applied to the surface, The method comprises partially removing the protective film and the workpiece and dividing the workpiece into multiple chips by irradiating the workpiece with a pulsed laser beam having wavelengths absorbed by the light absorber and the workpiece, respectively, along the boundary from the side on which the protective film is formed, The light-absorbing agent has a flavonoid structure, a flavonol structure, or an isoflavone structure. A method for manufacturing chips, wherein the protective film agent contains 52.00 parts by mass or more of the light absorber per 100 parts by mass of the water-soluble resin.

12. A method for manufacturing a chip according to claim 11 or 12, wherein each of the plurality of devices is an image sensor.

Images