Dryness detection method and processing method for workpieces

Abstract

To provide a dryness detection method and a workpiece processing method capable of detecting the dryness of a protective film.SOLUTION: A dryness detection method includes a light irradiation step 2-1 of irradiating a liquid resin with excitation light having a wavelength absorbed by a light absorbent contained in the liquid resin, a measurement step 2-2 of receiving the fluorescence emitted by the light absorbent due to the irradiation of the excitation light and measuring a fluorescence spectrum showing the correspondence relationship between the intensity and the wavelength of the fluorescence, and a determination step 2-3 of determining whether the liquid resin is dry on the basis of the peak wavelength in the fluorescence spectrum. A processing method for a workpiece includes a protective film formation step 1 of applying a liquid resin containing a light absorbent to a workpiece to form a protective film, a dryness detection step 2 of using the dryness detection method to detect whether the liquid resin is dry, and a processing step 3 of irradiating the workpiece with a laser beam from the side on which the protective film is formed to perform processing when it is detected that the liquid resin is dry.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drying detection method and a processing method for a workpiece.

Background Art

[0002] In order to divide a semiconductor wafer having a plurality of devices formed on a substrate into individual chips, a method is known that irradiates the semiconductor wafer with a laser beam having a wavelength absorbable by the semiconductor wafer to form processing grooves along lines to divide, and then divide the wafer. In such a processing method, a protective film made of liquid resin is coated on the surface of the wafer in advance to prevent debris generated when the wafer is ablated from adhering to the device surface and degrading quality (see Patent Document 1).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] When a protective film is formed on the wafer surface, if laser processing is performed before the protective film is sufficiently dried and cured, the protective film may scatter and contaminate the optical system for laser processing or the interior of the processing apparatus, or the protective film may not fully exhibit its function as a protective film, leading to peeling of a metal film such as TEG (Test Element Group) formed on the lines to divide, which degrades the quality of the devices.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a drying detection method capable of detecting drying of a protective film and a processing method for a workpiece.

Means for Solving the Problem

[0006] To solve the above-mentioned problems and achieve the objective, the present invention provides a drying detection method for detecting the drying of a liquid resin containing an absorbent, comprising: a light irradiation step of irradiating the liquid resin with excitation light having a wavelength absorbed by the absorbent; a measurement step of receiving fluorescence emitted by the absorbent as a result of irradiation with the excitation light and measuring a fluorescence spectrum showing the correspondence between the intensity of the fluorescence and its wavelength; and a determination step of determining whether or not the liquid resin is dry based on the peak wavelength in the fluorescence spectrum measured in the measurement step.

[0007] Furthermore, in the drying detection method of the present invention, in the determination step, it may be determined that the liquid resin is dry if the peak wavelength in the fluorescence spectrum measured in the measurement step is on the shorter wavelength side of a predetermined threshold.

[0008] Furthermore, the drying detection method of the present invention may also involve performing the light irradiation step and the measurement step in advance when the liquid resin is in a dried state, and setting the threshold based on the peak wavelength in the fluorescence spectrum measured in the measurement step performed in advance.

[0009] Furthermore, the present invention relates to a drying detection method for detecting the drying of a liquid resin containing an absorbent, and is characterized by comprising: a light irradiation step of irradiating the liquid resin with excitation light having a wavelength absorbed by the absorbent; a measurement step of receiving fluorescence emitted by the absorbent as a result of irradiation with the excitation light and measuring the number of photons of the fluorescence detected in a predetermined wavelength range; and a determination step of determining that the liquid resin is dry if the number of photons of the fluorescence in the predetermined wavelength range measured in the measurement step is greater than a predetermined threshold.

[0010] Furthermore, the present invention provides a method for processing a workpiece, comprising: a protective film forming step of applying a liquid resin containing a light absorbent to the workpiece to form a protective film to protect the workpiece; a drying detection step of detecting that the liquid resin is dry using the drying detection method described in any one of claims 1 to 3; and, if the drying detection step detects that the liquid resin is dry, a processing step of irradiating the workpiece with a laser beam from the side on which the protective film is formed to perform processing. [Effects of the Invention]

[0011] The present invention can detect the drying of the protective film. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart showing the flow of the workpiece processing method according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of the protective film formation step shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing a magnified portion of the workpiece after the protective film formation step shown in Figure 1. [Figure 4] Figure 4 is a schematic diagram showing the general configuration of the fluorescence detection unit that performs the drying detection step shown in Figure 1. [Figure 5] Figure 5 is a schematic diagram showing an example of the processing steps shown in Figure 1. [Figure 6] Figure 6 is a schematic diagram showing the general configuration of the fluorescence detection unit of the first modified example. [Figure 7] Figure 7 is a schematic diagram showing the general configuration of the fluorescence detection unit of the second modified example. [Figure 8] Figure 8 is a schematic diagram showing the general configuration of the fluorescence detection unit of the third modified example. [Figure 9] Figure 9 is a schematic diagram showing the general configuration of the fluorescence detection unit of the fourth modified example. [Figure 10]FIG. 10 is a graph showing fluorescence spectra measured in the measurement step of the method for processing a workpiece according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. In addition, the constituent elements described below include those that can be easily conceived by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. In addition, various omissions, substitutions, or changes to the configuration can be made without departing from the gist of the present invention.

[0014] [First Embodiment] A drying detection method and a processing method for a workpiece 10 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing the flow of the processing method for the workpiece 10 according to the first embodiment. As shown in FIG. 1, the processing method for a workpiece 10 of the first embodiment includes a protective film forming step 1, a drying detection step 2, and a processing step 3. The drying detection step 2 is the drying detection method of the first embodiment, and includes a light irradiation step 2-1, a measurement step 2-2, and a determination step 2-3.

[0015] In the first embodiment, the workpiece 10 to be processed is, for example, a wafer such as a disk-shaped semiconductor wafer or an optical device wafer that uses silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like as a substrate. The workpiece 10 has a plurality of scheduled dividing lines formed on a surface 11 of a substrate, and devices formed in respective regions partitioned by the plurality of scheduled dividing lines intersecting in a grid pattern.

[0016] The device is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a MEMS (Micro Electro Mechanical Systems). Further, TEG, which is an element for evaluation to detect design and manufacturing problems occurring in devices, may be formed on the lines to be divided.

[0017] The workpiece 10 is supported by an annular frame 20 and a tape 21 (see FIG. 2 described later and the like). The frame 20 has an opening larger than the outer diameter of the workpiece 10, and is made of a material such as metal or resin. The tape 21 includes a base material layer made of synthetic resin, and an adhesive paste layer laminated on at least one of the front surface and the back surface of the base material layer, and the outer periphery thereof is adhered to the back side of the frame 20. The workpiece 10 is positioned at a predetermined position of the opening of the frame 20, and is fixed to the frame 20 and the tape 21 by adhering the back surface 12 to the tape 21.

[0018] (Protective Film Forming Step 1) FIG. 2 is a schematic diagram showing an example of the protective film forming step 1 shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view showing a part of the workpiece 10 after the protective film forming step 1 shown in FIG. 1. The protective film forming step 1 is a step of applying a liquid resin 34 containing a light absorbing agent to the workpiece 10 to form the protective film 13 that protects the workpiece 10. In the protective film forming step 1 of the first embodiment, the liquid resin 34 is applied to the front surface 11 of the workpiece 10 by the protective film forming unit 30 shown in FIG. 2. In the first embodiment, the protective film forming unit 30 includes a spin coater, and comprises a spinner table 31, a clamp member 32, and a liquid resin supply nozzle 33.

[0019] In protective film formation step 1, first, the back surface 12 of the workpiece 10 is held by suction to the holding surface of the spinner table 31 via the tape 21, and the outer circumference of the frame 20 is clamped by the clamping member 32. Next, with the spinner table 31 rotating around its axis, liquid resin 34 is dripped from the liquid resin supply nozzle 33 onto the surface 11 of the workpiece 10. At this time, the liquid resin supply nozzle 33 may reciprocate in the radial direction of the workpiece 10. The dripped liquid resin 34 flows from the center to the outer circumference on the surface 11 of the workpiece 10 by the centrifugal force generated by the rotation of the spinner table 31, and is applied to the entire surface 11 of the workpiece 10.

[0020] The liquid resin 34 contains a light-absorbing agent. The main components of the liquid resin 34 include, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), a light-absorbing agent such as ferulic acid, and a solvent such as water and propylene glycol monomethyl ether (PGME) organic solvent. For example, HOGOMAX (registered trademark) manufactured by DISCO Corporation is used as the liquid resin 34.

[0021] In protective film formation step 1, a layer of liquid resin 34 covering the entire surface 11 of the workpiece 10 is formed by drying and curing the liquid resin 34 applied to the entire surface 11 of the workpiece 10. As a result, as shown in Figure 3, the surface 11 of the workpiece 10 is covered with a protective film 13 made of the layer of liquid resin 34. The protective film 13 is preferably transparent. This allows for alignment using the camera of the processing device in processing step 3, which will be described later.

[0022] (Drying detection step 2) Figure 4 is a schematic diagram showing the general configuration of the fluorescence detection unit 50 that performs the drying detection step 2 shown in Figure 1. The drying detection step 2 is a step to detect whether the liquid resin 34 containing the light absorber is dry. In the first embodiment, the drying detection step 2 is performed by the fluorescence detection unit 50 shown in Figure 4.

[0023] The fluorescence detection unit 50 irradiates the workpiece 10 held on the holding table 40 with excitation light 51 and detects fluorescence 52 emitted by the light absorber contained in the liquid resin 34 (protective film 13) on the surface 11 of the workpiece 10. The fluorescence detection unit 50 includes an excitation light source 53, a focusing lens 54, an excitation light reflector 55, a light receiving unit 56, a bandpass filter 57, a fluorescence reflector 58, and a control unit 90.

[0024] The excitation light source 53 irradiates the liquid resin 34 (protective film 13) with excitation light 51 having a wavelength absorbed by the light absorber contained in the liquid resin 34 (protective film 13). The excitation light source 53 has, for example, a GaN (gallium nitride) based light-emitting element.

[0025] The focusing lens 54 focuses the excitation light 51 irradiated from the excitation light source 53 toward the liquid resin 34 (protective film 13) applied to the workpiece 10, which is held on the holding surface of the holding table 40 with its back surface 12 side facing the holding surface. In the first embodiment, the focusing lens 54 is positioned between the excitation light reflector 55 and the workpiece 10, but in the present invention, it may be positioned between the excitation light source 53 and the excitation light reflector 55.

[0026] The excitation light reflector 55 reflects the excitation light 51 irradiated from the excitation light source 53 and guides it toward the liquid resin 34 (protective film 13) applied to the workpiece 10 held on the holding surface of the holding table 40. In the first embodiment, the excitation light reflector 55 reflects the excitation light 51 irradiated from the excitation light source 53 toward the focusing lens 54.

[0027] The light-receiving unit 56 detects the intensity of fluorescence 52 generated from the liquid resin 34 (protective film 13) applied to the workpiece 10. Specifically, the light-receiving unit 56 detects the number of photons of the received fluorescence 52. The light-receiving unit 56 includes, for example, a high-sensitivity photodetector that converts light energy into electrical energy using the photoelectric effect and also has a current amplification (electron multiplication) function. The light-receiving unit 56 is, for example, placed in a vacuum region partitioned by a glass tube, and receives photoelectrons (photons) of fluorescence 52 that have passed through the glass tube, and outputs an electrical signal indicating the number of photons of fluorescence 52. The photoelectrons of fluorescence 52 received by the light-receiving unit 56 generate secondary electrons one after another through photoelectron collisions, amplifying the current.

[0028] The bandpass filter 57 is positioned before the light-receiving unit 56. The bandpass filter 57 allows light of a predetermined wavelength from the fluorescence 52 generated from the liquid resin 34 (protective film 13) applied to the workpiece 10 to pass through, and removes light of wavelengths other than the fluorescence 52 of the predetermined wavelength. Therefore, for example, even if some of the excitation light 51 is scattered and directed towards the light-receiving unit 56, the excitation light 51 is removed by the bandpass filter 57.

[0029] The fluorescent reflector 58 reflects the fluorescence 52 generated from the liquid resin 34 (protective film 13) applied to the workpiece 10 toward the light receiving unit 56. The fluorescent reflector 58 is a spheroidal mirror whose reflective surface 59 is made up of a part of the surface of a spheroid obtained by rotating an ellipse 60, which has a major axis 61 extending vertically and a minor axis 62 perpendicular to the major axis 61, around the major axis 61.

[0030] Elliptic mirrors are known to have two foci, and light emitted from one focal point is reflected off the inner surface of the elliptic mirror before reaching the other focal point. The elliptic mirror forming the ellipsoid in the first embodiment has a first focal point 63 and a second focal point 64. At the position of the first focal point 63, there is a portion of the liquid resin 34 (protective film 13) applied to the workpiece 10 that is irradiated with excitation light 51. A light-receiving unit 56 is located at the second focal point 64.

[0031] With this configuration, when excitation light 51 is irradiated onto the liquid resin 34 (protective film 13) applied to the workpiece 10 located at the first focal point 63, fluorescence 52 is emitted from the liquid resin 34 (protective film 13) applied to the workpiece 10 by the excitation light 51. The fluorescence 52 is reflected by a reflective surface 59 which is part of a spheroid, focused toward the second focal point 64, and received by a light-receiving unit 56 located at the second focal point 64.

[0032] Therefore, the fluorescence 52 emitted from the liquid resin 34 (protective film 13) applied to the workpiece 10 can be efficiently guided to the light-receiving unit 56 located at the second focal point 64 via the reflective surface 59, thereby reducing the loss of weak fluorescence 52. Furthermore, in the first embodiment, since the light-receiving unit 56 is located at the second focal point 64, detection sensitivity can be improved even for fluorescence 52 of low intensity.

[0033] (Light irradiation step 2-1) The light irradiation step 2-1 is a step of irradiating the liquid resin 34 (protective film 13) with excitation light 51 having a wavelength absorbed by the absorbent. The excitation light 51 has a different wavelength (e.g., 365 nm) from the processing wavelength (e.g., 355 nm) of the laser beam 81 irradiated in the processing step 3 described later, and is, for example, ultraviolet light.

[0034] In the light irradiation step 2-1, first, the back surface 12 of the workpiece 10 is held by suction to the holding surface of the holding table 40 via the tape 21. Next, the first focal point 63 of the fluorescence detection unit 50 is aligned with the liquid resin 34 (protective film 13) applied to the workpiece 10. Then, the fluorescence detection unit 50 irradiates the liquid resin 34 (protective film 13) applied to the workpiece 10 with excitation light 51. The light absorber contained in the liquid resin 34 (protective film 13) absorbs the excitation light 51 and emits fluorescence 52.

[0035] (Measurement step 2-2) Measurement step 2-2 is a step in which the fluorescence 52 emitted by the absorber due to the irradiation of excitation light 51 in light irradiation step 2-1 is received, and the number of photons of the fluorescence 52 detected in a predetermined wavelength range is measured. The predetermined wavelength range is, for example, 410 to 430 nm if the bandpass filter 57 allows only fluorescence 52 in the wavelength range of 410 to 430 nm to pass through.

[0036] The light-receiving unit 56 of the fluorescence detection unit 50 receives fluorescence 52 emitted from the liquid resin 34 (protective film 13). The light-receiving unit 56 detects the intensity (number of photons) of fluorescence 52 in a predetermined wavelength range that has passed through the bandpass filter 57, and outputs the detection result to the control unit 90. The control unit 90 may store the number of photons of fluorescence 52 in the predetermined wavelength range detected by the light-receiving unit 56 as a time progression.

[0037] (Decision-making steps 2-3) The determination step 2-3 is the step of determining that the liquid resin 34 is dry if the number of photons of fluorescence 52 in a predetermined wavelength range measured in measurement step 2-2 is greater than a predetermined threshold. The predetermined wavelength range corresponds to the wavelength band that the bandpass filter 57 passes through.

[0038] It is known that changing the type of solvent alters the intensity and peak wavelength of fluorescence 52. After protective film formation step 1, the liquid resin 34 applied to the surface 11 of the workpiece 10 gradually dries and hardens over time. As drying progresses, the water and organic solvents contained in the liquid resin 34 evaporate, changing their component ratios. Since the peak wavelength of fluorescence 52 changes due to the change in solvent, the peak wavelength of fluorescence 52 changes as drying progresses. In other words, the number of photons of fluorescence 52 detected in a predetermined wavelength range changes.

[0039] In the determination step 2-3, the control unit 90 compares the number of photons of the fluorescent 52, which changes in this manner, with a predetermined threshold value. If the number of photons of the fluorescent 52 measured in the measurement step 2-2 exceeds the threshold value, the control unit 90 determines that the liquid resin 34 is dry. The drying detection step 2 repeatedly performs the light irradiation step 2-1, the measurement step 2-2, and the determination step 2-3 until drying of the liquid resin 34 is detected. If drying of the liquid resin 34 is detected, the drying detection step 2 is terminated, and the process moves to the next processing step 3.

[0040] (Processing step 3) Figure 5 is a schematic diagram showing an example of processing step 3 shown in Figure 1. Processing step 3 is performed when the liquid resin 34 is detected to be dry in drying detection step 2. Processing step 3 is a step in which a laser beam 81 is irradiated onto the workpiece 10 from the side on which the protective film 13 is formed to perform processing. Processing step 3 in the first embodiment is performed by the laser irradiation unit 80 shown in Figure 5. The laser irradiation unit 80 irradiates the workpiece 10 held on the holding table 70 with a laser beam 81.

[0041] The laser irradiation unit 80 includes, for example, an oscillator that emits a laser beam 81, a focuser that focuses and irradiates the laser beam 81 toward the holding surface of the holding table 70, and various optical components that guide the laser beam 81 from the oscillator to the focuser. Multiple clamp members 71 that hold the frame 20 that supports the workpiece 10 are arranged around the holding table 70. The holding table 70 is movable relative to the focusing point 82 of the laser beam 81 formed by the laser irradiation unit 80 by a moving unit (not shown). The holding table 70 may also be used interchangeably with the holding table 40 shown in Figure 4, in which case the holding tables 40 and 70 are configured to be movable between a position facing the fluorescence detection unit 50 and a position facing the laser irradiation unit 80.

[0042] In processing step 3, first, the back surface 12 of the workpiece 10 is held by suction to the holding surface of the holding table 70 via the tape 21, and the outer circumference of the frame 20 is clamped by the clamping member 71. The focal point 82 of the laser beam 81 is positioned on the planned division line of the surface 11 of the workpiece 10. Next, while moving the focal point 82 and the holding table 70 relative to each other, a pulsed laser beam 81 is irradiated along the planned division line. The laser beam 81 is a laser beam with a wavelength that is absorbed by the workpiece 10. By irradiating the workpiece 10 with a laser beam 81 of a wavelength that is absorbed by the workpiece 10, the workpiece 10 is divided along the planned division line and broken down into individual chips.

[0043] During this process, the laser beam 81 processes the workpiece 10, generating processing debris 14 on the surface 11 of the workpiece 10. The processing debris 14 adheres to the protective film 13 formed on the surface 11 of the workpiece 10. After the processing step 3 is completed, for example, the surface 11 of the workpiece 10 is cleaned to remove the protective film 13. The removal of the protective film 13 by cleaning is performed, for example, by supplying cleaning water pressurized to about 10-12 MPa to the surface 11 of the workpiece 10. The cleaning water may be, for example, pure water or bubble water mixed with air. Alternatively, cleaning may be performed using a so-called two-fluid system, where water and air are mixed together.

[0044] In addition, the fluorescence detection unit 50 that irradiates excitation light 51 and detects fluorescence 52 in the drying detection step 2 of the first embodiment is not limited to the configuration shown in Figure 4, but may also be configured as shown in the following first to fourth modified examples.

[0045] [First variation] Figure 6 is a schematic diagram showing the general configuration of the fluorescence detection unit 50-1 of the first modified example. The fluorescence detection unit 50-1 of the first modified example includes an excitation light source 53, a light receiving unit 56, a bandpass filter 57, and a control unit 90. While the excitation light source 53 of the embodiment irradiates the workpiece 10 with excitation light 51 from directly above, the excitation light source 53 of the first modified example irradiates the workpiece 10 with excitation light 51 incident on its surface 11 at a predetermined inclination angle.

[0046] In the first modified example, an LED (Light Emitting Diode) or a CW (Continuous Wave) laser can be used as the excitation light source 53. The fluorescence detection unit 50-1 of the first modified example does not have the function to improve detection sensitivity even for weak fluorescence 52 compared to the fluorescence detection unit 50 of the embodiment, but it is possible to detect fluorescence 52 with a simple configuration.

[0047] [Second variation] Figure 7 is a schematic diagram showing the general configuration of a second modified fluorescence detection unit 50-2. The second modified fluorescence detection unit 50-2 includes an excitation light source 53, a light receiving unit 56, a bandpass filter 57, a fiber 65, a probe 66, and a control unit 90. The fiber 65 guides excitation light 51 from the excitation light source 53 to the liquid resin 34 (protective film 13) coated on the surface 11 of the workpiece 10. The probe 66 focuses the excitation light 51 guided by the fiber 65 onto the liquid resin 34 (protective film 13) coated on the surface 11 of the workpiece 10 and guides the fluorescence 52 generated from the liquid resin 34 (protective film 13) to the light receiving unit 56 via the bandpass filter 57.

[0048] In the second modified example, excitation light 51 is irradiated onto the liquid resin 34 (protective film 13) in the probe 66, generating fluorescence 52. Leakage to the outside is suppressed, thereby improving the detection efficiency of fluorescence 52.

[0049] [Third variation] Figure 8 is a schematic diagram showing the general configuration of the fluorescence detection unit 50-3 of the third modified example. The fluorescence detection unit 50-3 of the third modified example includes an excitation light source 53-1, a light receiving unit 56, a bandpass filter 57, and a control unit 90. The excitation light source 53-1 of the third modified example irradiates a large area or the entire surface 11 of the workpiece 10 with excitation light 51. The light receiving unit 56 receives the fluorescence 52 generated over the entire surface of the liquid resin 34 (protective film 13) coated on the surface 11 of the workpiece 10 via the bandpass filter 57.

[0050] In the third modified example, an LED array is preferably used as the excitation light source 53-1. The fluorescence detection unit 50-3 in the third modified example can detect fluorescence 52 generated over the entire surface of the liquid resin 34 (protective film 13) coated on the surface 11 of the workpiece 10. Therefore, even if there are inconsistencies in the degree of drying, it is possible to observe, for example, the changes in the fluorescence spectrum 91 in the area where drying progresses most slowly.

[0051] [Fourth variation] Figure 9 is a schematic diagram showing the general configuration of the fluorescence detection unit 50-4 of the fourth modified example. The fluorescence detection unit 50-4 of the fourth modified example includes an excitation light source 53-2, a light receiving unit 56, a bandpass filter 57, and a control unit 90. The excitation light source 53-2 of the fourth modified example has a shape with a hollow center (for example, a donut shape) and irradiates a large area or the entire surface 11 of the workpiece 10 with excitation light 51 from directly above the workpiece 10. The light receiving unit 56 receives the fluorescence 52 generated over the entire surface of the liquid resin 34 (protective film 13) coated on the surface 11 of the workpiece 10 via the bandpass filter 57.

[0052] In the fourth modified example, an LED array is preferably used as the excitation light source 53-2. The fluorescence detection unit 50-4 of the fourth modified example, like the fluorescence detection unit 50-3 of the third modified example, can detect fluorescence 52 generated over the entire liquid resin 34 (protective film 13) applied to the surface 11 of the workpiece 10. Therefore, even if there are inconsistencies in the degree of drying, it is possible to observe, for example, the changes in the fluorescence spectrum 91 in the area where drying progresses most slowly.

[0053] As described above, the processing method of the first embodiment and each of its modifications involves irradiating the liquid resin 34 containing an absorbent applied to the surface 11 of the workpiece 10 with excitation light 51 such as ultraviolet light, thereby causing the absorbent contained in the liquid resin 34 to fluoresce. Then, at predetermined elapsed time intervals after the application of the liquid resin 34, the number of photons of fluorescence 52 in a predetermined wavelength range is measured, and the drying state can be detected by determining whether the number of photons is greater than a predetermined threshold.

[0054] This allows the workpiece 10 to be laser-processed after the protective film 13 has dried and hardened sufficiently. Therefore, it is possible to prevent the protective film 13 from scattering and contaminating the optical system or processing equipment used for laser processing, and to prevent the protective film 13 from not fully performing its function, which could cause metal films such as TEGs formed on the planned division lines to peel off and degrade the quality of the device.

[0055] [Second Embodiment] Next, a drying detection method according to the second embodiment will be described. The drying detection method of the second embodiment differs from the drying detection method of the first embodiment in that it detects drying based on the number of photons of fluorescence 52 in a predetermined wavelength range, whereas the drying detection method of the second embodiment detects drying based on the peak wavelength in the fluorescence spectrum. This will be explained in detail below.

[0056] In the drying detection step 2 of the second embodiment, the procedure is carried out by a fluorescence detection device capable of irradiating with excitation light 51, spectrally detecting and receiving the fluorescence 52, and measuring the fluorescence spectrum. The fluorescence detection device may be, for example, the fluorescence detection unit 50 used in the drying detection step 2 of the first embodiment, but without the bandpass filter 57, and with a small spectrometer mounted on the light receiving unit 56. That is, the fluorescence detection device can scan the wavelength of the fluorescence 52 and obtain a fluorescence spectrum 91 (see Figure 10) that represents the relationship between fluorescence intensity at different fluorescence wavelengths. In the following description, components of the fluorescence detection device similar to those shown in Figure 4 will be denoted by the same reference numerals, and the fluorescence detection device will be referred to as the fluorescence detection unit 50.

[0057] The drying detection step 2 of the second embodiment consists of three steps, similar to the drying detection step 2 of the first embodiment: a light irradiation step 2-1, a measurement step 2-2, and a determination step 2-3. The procedure for the light irradiation step 2-1 is the same as that of the light irradiation step 2-1 of the second embodiment, so its description is omitted.

[0058] (Measurement step 2-2) The measurement step 2-2 of the second embodiment is a step in which the fluorescence 52 emitted by the absorbent due to the irradiation of excitation light 51 in the light irradiation step 2-1 is received, and a fluorescence spectrum 91 (see Figure 10) showing the correspondence between the intensity of the fluorescence 52 and the wavelength (for example, wavelength 400-500 nm) is measured.

[0059] The light-receiving unit 56 of the fluorescence detection unit 50 receives the fluorescence 52 emitted from the liquid resin 34 (protective film 13) via a spectrometer. The light-receiving unit 56 detects the intensity of the fluorescence 52 and outputs the detection result to the control unit 90. The control unit 90 detects the intensity of the fluorescence 52 at each wavelength detected by the light-receiving unit 56 as a function of wavelength.

[0060] (Decision-making steps 2-3) The determination step 2-3 of the second embodiment is a step of determining whether or not the liquid resin 34 is dry based on the fluorescence spectrum 91 measured in the measurement step 2-2. Figure 10 is a graph showing the fluorescence spectrum 91 measured in the measurement step 2-2 of the processing method for the workpiece 10 according to the second embodiment. The graph shown in Figure 10 includes the data of the fluorescence spectrum 91-1 measured by performing the light irradiation step 2-1 and the measurement step 2-2 on the solution of the liquid resin 34, and the data of the fluorescence spectra 91-2, 91-3, 91-4, and 91-5 measured after the protective film formation step 1, 1 min, 5 min, 20 min, and 40 min.

[0061] In the determination step 2-3 of the second embodiment, the control unit 90 determines whether the liquid resin 34 is dry or not based on the peak wavelength of fluorescence 52 in the fluorescence spectrum 91. It is known that changing the type of solvent changes the intensity and peak wavelength of fluorescence 52. After the protective film formation step 1, the liquid resin 34 applied to the surface 11 of the workpiece 10 gradually dries and hardens over time. As drying progresses, the solvents such as water and organic solvents contained in the liquid resin 34 change in composition due to evaporation. Since the peak wavelength of fluorescence 52 changes as the solvent changes, the peak wavelength of fluorescence 52 changes as drying progresses.

[0062] In the case of a liquid resin 34 whose peak wavelength of fluorescence 52 shifts to a shorter wavelength as drying progresses, in judgment step 2-3, if the peak wavelength is shorter than a predetermined threshold 92 (for example, 420 nm), it is determined that the liquid resin 34 is dry. Alternatively, when irradiation and measurement are repeated several times at predetermined elapsed time intervals immediately after coating, it may be determined that the resin is dry if the peak wavelength has shifted 10 nm or more (preferably 15 nm or more) to a shorter wavelength from the peak wavelength immediately after coating.

[0063] Furthermore, in the case of a liquid resin 34 whose peak wavelength of fluorescence 52 shifts to a longer wavelength side as drying progresses, in judgment step 2-3, if the peak wavelength is on the longer wavelength side of a predetermined threshold 92, it is determined that the liquid resin 34 is dry. When irradiation and measurement are repeated several times at predetermined elapsed time intervals immediately after application, it may also be determined that the resin is dry if the peak wavelength has shifted 10 nm or more (preferably 15 nm or more) to the longer wavelength side from the peak wavelength immediately after application.

[0064] As shown in Figure 10, the liquid resin 34 of the embodiment has the property that the peak wavelength of fluorescence 52 shifts to the shorter wavelength side as drying progresses. In the second embodiment shown in Figure 10, a predetermined threshold 92 is set to 420 nm. The peak wavelength of the fluorescence spectrum 91-2 measured 1 min after the protective film formation step 1 is approximately 427 nm, which is on the longer wavelength side of the threshold 92. The peak wavelength of the fluorescence spectrum 91-3 measured 5 mins later is approximately 422 nm, which is on the longer wavelength side of the threshold 92. The peak wavelength of the fluorescence spectrum 91-4 measured 20 mins later is approximately 418 nm, which is on the shorter wavelength side of the threshold 92. The peak wavelength of the fluorescence spectrum 91-5 measured 40 mins later is approximately 415 nm, which is on the shorter wavelength side of the threshold 92. Therefore, in the measurement example shown in Figure 10, the control unit 90 determines that it is not dry at 5 mins and that it is dry at 20 mins.

[0065] The threshold 92 may be set, for example, based on the peak wavelength in the fluorescence spectrum 91 measured by performing the light irradiation step 2-1 and measurement step 2-2 in advance while the liquid resin 34 is in a dry state.

[0066] In the second embodiment, the drying detection step 2 is the same as in the first embodiment, and the light irradiation step 2-1, measurement step 2-2, and judgment step 2-3 are repeated until drying of the liquid resin 34 is detected. If drying of the liquid resin 34 is detected, the drying detection step 2 is terminated and the process proceeds to the next processing step 3.

[0067] As described above, the drying detection method and the processing method for the workpiece 10 according to the second embodiment involve irradiating the liquid resin 34 containing an absorbent applied to the surface 11 of the workpiece 10 with excitation light 51 such as ultraviolet light, thereby causing the absorbent contained in the liquid resin 34 to fluoresce. Then, at predetermined elapsed time intervals after the application of the liquid resin 34, the fluorescence spectrum 91, which shows the intensity of fluorescence 52 as a function of wavelength, is measured, and the drying state can be detected by observing the change in the peak wavelength of the fluorescence spectrum 91.

[0068] This allows the workpiece 10 to be laser-processed after the protective film 13 has dried and hardened sufficiently. Therefore, it is possible to prevent the protective film 13 from scattering and contaminating the optical system or processing equipment used for laser processing, and to prevent the protective film 13 from not fully performing its function, which could cause metal films such as TEGs formed on the planned division lines to peel off and degrade the quality of the device.

[0069] It should be noted that the present invention is not limited to the embodiments and modifications described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. [Explanation of Symbols]

[0070] 10 Workpiece 13 Protective film 30 Protective film forming unit 34 Liquid resin 50, 50-1, 50-2, 50-3, 50-4 Fluorescence Detection Unit 51 Excitation light 52 Fluorescence 53, 53-1, 53-2 Excitation light source 56 Light receiving part 57 Bandpass filter 80 Laser irradiation units 81 Laser beam 82 Focusing points 90 Control Unit 91, 91-1, 91-2, 91-3, 91-4, 91-5 fluorescence spectra 92 threshold

Claims

1. A drying detection method for detecting the drying of a liquid resin containing a light absorbent, A light irradiation step in which the liquid resin is irradiated with excitation light having a wavelength absorbed by the light absorber, A measurement step involves receiving the fluorescence emitted by the absorbent upon irradiation with the excitation light and measuring the fluorescence spectrum which shows the correspondence between the intensity of the fluorescence and its wavelength. The measurement step includes a determination step of determining whether the liquid resin is dry or not based on the peak wavelength in the fluorescence spectrum measured in the measurement step. A method for detecting dryness, characterized by the features described above.

2. In this decision step, In the measurement step, if the peak wavelength in the fluorescence spectrum measured is on the shorter wavelength side than a predetermined threshold, it is determined that the liquid resin is dry. The drying detection method according to claim 1, characterized in that

3. The light irradiation step and the measurement step are performed in advance while the liquid resin is in a dry state. The threshold is set based on the peak wavelength in the fluorescence spectrum measured in the previously performed measurement step. The drying detection method according to claim 2, characterized in that

4. A drying detection method for detecting the drying of a liquid resin containing a light absorbent, A light irradiation step in which the liquid resin is irradiated with excitation light having a wavelength absorbed by the light absorber, A measurement step in which the fluorescence emitted by the absorber upon irradiation with the excitation light is received, and the number of photons of the fluorescence detected in a predetermined wavelength range is measured, The measurement step includes a determination step in which it is determined that the liquid resin is dry if the number of photons of the fluorescence in the predetermined wavelength range measured in the measurement step is greater than a predetermined threshold. A method for detecting dryness, characterized by the features described above.

5. A method for processing a workpiece, A protective film forming step involves applying a liquid resin containing a light absorbent to the workpiece to form a protective film that protects the workpiece. A drying detection step in which the liquid resin is detected to be dry using the drying detection method described in any one of claims 1 to 4, If the drying detection step detects that the liquid resin is dry, the process includes a processing step of irradiating the workpiece with a laser beam from the side on which the protective film is formed to perform processing. A method for processing a workpiece, characterized by the features described above.

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