Dryness detection method and dryness detection device

Abstract

To provide a dry detection method capable of detecting dry of a liquid resin in appropriate timing, and a dry detection device.SOLUTION: A dry detection method for detecting dry of a liquid resin containing a solvent includes: a wavelength selecting step of selecting a light absorption wavelength of the solvent; a light source selecting step of selecting a light source including light of the selected wavelength; a light receiving step of receiving light with which the liquid resin is irradiated and which passes through the liquid resin; and a determination step of determining that the solvent is evaporated and dried in a case where a light quantity of light of the wavelength absorbed by the solvent exceeds a predetermined threshold in the light receiving step. A dry detection device 2 includes: a light source 62 including light of the light absorption wavelength of the solvent contained in a liquid resin P; light receiving means 7 for receiving light which is radiated from the light source 62 and passes through the liquid resin P; and determination means 110 which determines whether or not a light quantity Q of the light of the wavelength absorbed by the solvent exceeds a threshold Q9 based on the light quantity Q of light received by the light receiving means 7 to determine that the liquid resin P is dried.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for detecting dryness of a liquid resin. [Background technology]

[0002] Wafers with multiple devices such as ICs and LSIs formed on their surfaces, which are divided by planned division lines, are then divided into individual device chips using a dicing machine or laser processing machine, and these are used in electrical devices such as mobile phones and personal computers.

[0003] The laser processing device is generally composed of a chuck table that holds a wafer, a laser beam application means that applies a laser beam to the wafer held on the chuck table, and a feed means that feeds the chuck table and the laser beam application means relative to each other for processing, and is capable of processing wafers with high precision.

[0004] Furthermore, when a laser beam having an absorbent wavelength is irradiated onto the wafer to form division grooves along the intended division lines by ablation processing, a protective film is coated on the surface of the wafer in advance to prevent scattered debris from adhering to the surface of the device and degrading its quality (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-188475 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the protective film is formed by coating the surface of a wafer with a liquid resin, if processing is performed by irradiating a laser beam before the protective film has sufficiently dried and hardened, the protective film will not be able to fully function as a protective film, and metal films such as TEG formed on the planned dividing lines will peel off, resulting in a decrease in device quality. The above-mentioned problem is not limited to the case where a protective film is formed from a liquid resin on the surface of a wafer on which devices have been formed, as described above. In various situations where a liquid resin is used, it is necessary to determine whether the liquid resin has sufficiently dried, and therefore it is necessary to reliably determine whether the liquid resin has dried.

[0007] The present invention has been made in view of the above circumstances, and its main technical object is to provide a dryness detection method and a dryness detection device that can reliably determine whether a liquid resin has dried. [Means for solving the problem]

[0008] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a dryness detection method for detecting dryness of a liquid resin containing a solvent, comprising: a wavelength selection step of selecting a light absorption wavelength of the solvent; a light source selection step of selecting a light source that emits light of the selected wavelength; a light receiving step of irradiating light onto the liquid resin and receiving the light that has passed through the liquid resin; and a determination step of determining that the solvent has evaporated and dried when the amount of light of the wavelength absorbed by the solvent in the light receiving step exceeds a predetermined threshold. The light from the light source selected in the light source selection step is irradiated onto the liquid resin from which the solvent has evaporated and dried, the light that has passed through the liquid resin is received and the amount of light is measured, and a value below the amount of light is selected as the threshold value. A method for detecting desiccation is provided.

[0009] The dryness detection method is performed before performing ablation processing using a laser beam on the wafer coated with the liquid resin, and the determining step determines whether the liquid resin has reached a dry state suitable for ablation processing using a laser beam. It is preferable that the liquid resin is a water-soluble resin and the solvent is water. The wavelengths of light absorbed by water are 1450 nm, 1940 nm, and 2900 nm, and it is preferable that the light source selection step selects a light source that emits light of any of the above wavelengths.

[0010] Furthermore, according to the present invention, there is provided a dryness detection device for detecting the dryness of a liquid resin, comprising: a light source that emits light having a wavelength absorbed by a solvent contained in the liquid resin; a light receiving means that receives light that has been irradiated from the light source and passed through the liquid resin; and a determination means that determines whether the amount of light having a wavelength absorbed by the solvent exceeds a threshold based on the amount of light received by the light receiving means, thereby determining that the liquid resin has dried. The threshold value is determined by irradiating the light from the light source onto a liquid resin from which the solvent has evaporated and dried, receiving the light that has passed through the liquid resin, and measuring the amount of light, and selecting a value below the amount of light as the threshold value. A dryness detection device is provided. [Effects of the Invention]

[0011] The dryness detection method of the present invention is a method for detecting dryness of a liquid resin containing a solvent, and includes a wavelength selection step of selecting a light absorption wavelength of the solvent, a light source selection step of selecting a light source that emits light of the selected wavelength, a light receiving step of irradiating light onto the liquid resin and receiving the light that has passed through the liquid resin, and a determination step of determining that the solvent has evaporated and dried when the amount of light of the wavelength absorbed by the solvent in the light receiving step exceeds a predetermined threshold. The light from the light source selected in the light source selection step is irradiated onto the liquid resin from which the solvent has evaporated and dried, the light that has passed through the liquid resin is received and the amount of light is measured, and a value below the amount of light is selected as the threshold value. This makes it possible to reliably determine whether the liquid resin has dried, and for example, it becomes possible to perform ablation processing by irradiating the wafer with a laser beam when the liquid resin is reliably dried. This eliminates the problem that even if a metal film such as TEG is formed on the planned dividing line, it will peel off during the ablation processing, thereby degrading the quality of the device.

[0012] The dryness detection device of the present invention is a dryness detection device that detects the dryness of a liquid resin, and includes a light source that emits light having a wavelength absorbed by a solvent contained in the liquid resin, a light receiving means that receives light that is irradiated from the light source and passes through the liquid resin, and a determination means that determines whether the amount of light having a wavelength absorbed by the solvent exceeds a threshold based on the amount of light received by the light receiving means, thereby determining that the liquid resin has dried. The threshold value is determined by irradiating the light from the light source onto a liquid resin from which the solvent has evaporated and dried, receiving the light that has passed through the liquid resin, and measuring the amount of light, and selecting a value below the amount of light as the threshold value.This makes it possible to reliably determine whether the liquid resin has dried, and for example, it becomes possible to perform ablation processing by irradiating the wafer with a laser beam when the liquid resin is reliably dry. This solves the problem that even if a metal film such as TEG is formed on the planned dividing line, it will peel off during the ablation processing, thereby reducing the quality of the device. [Brief explanation of the drawings]

[0013] [Figure 1] 1A is a perspective view showing a mode of forming a protective film made of a liquid resin on a wafer, and FIG. 1B is an enlarged cross-sectional view showing a part of the wafer shown in FIG. 1A. [Figure 2] 1 is an overall perspective view of a dryness detection device according to an embodiment of the present invention; [Figure 3] 3(a) is a block diagram showing an optical system of a dryness detection means of the dryness detection device shown in FIG. 2, and FIG. 3(b) is a cross-sectional view showing an enlarged view of a part of a wafer in a state where a light receiving step is being performed. [Figure 4] FIG. 1 is a conceptual diagram showing the relationship between dryness and light intensity. [Figure 5] 10 is a flowchart showing a determination process. [Figure 6] FIG. 10 is a cross-sectional view showing another embodiment of the aspect of performing the light receiving step. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a dryness detection method and a dryness detection device configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0015] 1(a) shows a protective film forming apparatus 20 (only a portion thereof is shown) and a wafer 10 on which drying of a liquid resin is detected by the dryness detection method of this embodiment. The wafer 10 is a semiconductor disk-shaped substrate having a surface 10a partitioned by planned division lines 14 and having a plurality of devices 12 formed on it. The wafer 10 is held by adhesive tape T on an annular frame F having an opening Fa capable of accommodating the wafer 10.

[0016] The wafer 10 of this embodiment is irradiated with a laser beam having a wavelength that is absorbable by the wafer 10 by a laser processing apparatus (not shown), and a dividing groove is formed along a dividing line 14 by ablation processing. Before performing the above-described laser processing, the surface 10a of the wafer 10 is coated with a liquid resin P so that debris scattered during the laser processing on the wafer 10 does not adhere to the surface of the device 12 and degrade the quality.

[0017] The liquid resin P is supplied to the surface 10a of the wafer 10 by, for example, a protective film forming apparatus 20 shown in FIG. 1(a). The protective film forming apparatus 20 includes a spinner table 22 configured to be able to suck and hold the above-described wafer 10 and rotated at high speed in the direction indicated by an arrow R1 in the figure, and a liquid resin supply nozzle 24 that drops a predetermined amount of the liquid resin P downward from above the center of the spinner table 22.

[0018] The above-described wafer 10 is sucked and held by the spinner table 22, the liquid resin P is dropped from the liquid resin supply nozzle 24 onto the surface 10a of the wafer 10, and the spinner table 22 is rotated at high speed in the direction indicated by the arrow R1. The liquid resin P of this embodiment is, for example, a water-soluble resin PVA (polyvinyl alcohol), and the solvent is water. By the rotation of the spinner table 22, the liquid resin P spreads on the surface 10a of the wafer 10, and as understood from the cross-sectional view partially enlarged in FIG. 1(b), a protective film of the liquid resin P is formed on the surface 10a of the wafer 10. The protective film of the liquid resin P formed on the surface 10a of the wafer 10 dries and cures as water, which is the solvent, evaporates over time. The drying detection method of this embodiment aims to reliably determine whether the liquid resin P forming this protective film has reached a dry state suitable for ablation processing by a laser beam.

[0019] In order to detect the dry state of the above-described liquid resin P, the wafer 10 is transported to a drying detection apparatus 2 shown in FIG. 2, which is suitable for carrying out the drying detection method of the present invention.

[0020] 2 shows an overall perspective view of the dryness detection device 2. The dryness detection device 2 is disposed on a base 2a and includes a holding means 3 for holding the wafer 10 described above, a moving means 4 for moving the holding means 3 in the X-axis direction and the Y-axis direction, a dryness detection means 6 for detecting the drying of the liquid resin P on the wafer 10 held by the holding means 3, a frame 5 consisting of a vertical wall 5a erected on the side of the moving means 4 and a horizontal wall 5b extending horizontally from the upper end of the vertical wall 5a, and a control means 100. An optical system (described in detail later) of the dryness detection means 6 is housed inside the horizontal wall 5b.

[0021] 2, the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2a so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support column 33. A chuck table 35 extending upward through an elongated hole formed in the cover plate 34 is disposed on the cover plate 34. The chuck table 35 is a means for holding the wafer 10 using an XY plane specified by the X and Y coordinates as a holding surface, and is configured to be rotatable by a rotation drive means (not shown) housed in the support column 33. A suction chuck 36 formed of a porous material with air permeability as the holding surface is disposed on the upper surface of the chuck table 35. The suction chuck 36 is connected to a suction means (not shown) by a flow path passing through the support 33, and four clamps 37 are arranged at equal intervals around the suction chuck 36 to grip an annular frame F when holding the wafer 10 (described later) on the chuck table 35.

[0022] The moving means 4 includes an X-axis moving means 4a that moves the chuck table 35 in the X-axis direction and a Y-axis moving means 4b that moves the chuck table 35 in the Y-axis direction. The X-axis moving means 4a converts the rotational motion of the motor 42a into linear motion via a ball screw 42b and transmits the linear motion to the X-axis movable plate 31, moving the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2b, 2b arranged on the base 2a along the X-axis direction. The Y-axis moving means 4b converts the rotational motion of the motor 44a into linear motion via a ball screw 44b and transmits the linear motion to the Y-axis movable plate 32, moving the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged on the X-axis movable plate 31 along the Y-axis direction.

[0023] 3(a) is a block diagram showing an outline of the optical system of the dryness detection means 6 of this embodiment. The dryness detection means 6 includes at least a light source 62 that irradiates light L0, and a light receiving means 7 that receives light L1 after the light L0 is irradiated onto the liquid resin P on the front surface 10a of the wafer 10 and passes through the liquid resin P. More specifically, the device comprises a reflecting mirror 63 that changes the optical path of the light L0 emitted from the light source 62 to an appropriate direction, a beam splitter 64 that transmits the light L0 emitted from the reflecting mirror 63, a condenser 60 equipped with a focusing lens 61 that collects the light L0 and irradiates it onto the liquid resin P of the wafer 10, a bandpass filter 65 that transmits only a predetermined wavelength range contained in the light L1 that passes through the liquid resin P of the wafer 10 and is reflected by the surface 10a of the wafer 10 and is reflected by the beam splitter 64, and a light receiving means 7 composed of a photodetector that receives the light L2 after passing through the bandpass filter 65 and outputs the amount of light L2 as a voltage value (mV), and the value of the amount of light detected by the light receiving means 7 is sent to and stored in the control means 100.

[0024] The control means 100 provided in the dryness detection device 2 is configured by a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program, etc., a readable / writable random access memory (RAM) that temporarily stores detected values, calculation results, etc., an input interface, and an output interface (details not shown in the figures). At least the light receiving means 7 is connected to the control means 100, and the control means 100 includes a determination means 110 (described in detail later) configured with a control program that determines whether the liquid resin P has dried based on the amount of light L2 received by the light receiving means 7. Although not shown in the figures, the control means 100 may also control the operation of the holding means 3, moving means 4, etc.

[0025] The dryness detection device 2 of this embodiment has roughly the same configuration as described above, and the following describes the dryness detection method of this embodiment, which is carried out using the dryness detection device 2. The protective film forming device 20 may be disposed inside the dryness detection device 2 shown in Fig. 2. In this case, the protective film is formed by supplying liquid resin P to the surface 10a of the wafer 10 while the wafer 10 is held by the holding means 3.

[0026] When carrying out the dryness detection method of this embodiment, a wavelength selection step is carried out to select the light absorption wavelength of the solvent of the liquid resin P supplied as a protective film to the wafer 10. More specifically, as described above, the protective film formed on the wafer 10 of this embodiment is formed from the liquid resin P whose solvent is water. Water has the property of absorbing light with wavelengths longer than 700 nm, and is known to particularly absorb light with wavelengths of 1450 nm, 1940 nm, and 2900 nm. Therefore, in the wavelength selection step of this embodiment, one of the wavelengths 1450 nm, 1940 nm, and 2900 nm, for example 1940 nm, is selected as the light absorption wavelength of the water solvent.

[0027] Next, a light source selection step is carried out to select a light source that includes light of the wavelength (1940 nm) selected in the wavelength selection step described above. As the light source 62 of this embodiment, for example, a QTH lamp capable of irradiating light including the wavelength selected in the wavelength selection step described above, i.e., light of 1940 nm, is selected. A QTH lamp is a light source that includes light of a wide wavelength range from 350 to 4000 nm, and can be used regardless of the wavelength selected in the wavelength selection step described above, which is the light absorption wavelength of 1450 nm, 1940 nm, or 2900 nm that is particularly absorbed by water.

[0028] Next, a light receiving step is carried out in which light L0 is irradiated onto the liquid resin P and the light is received after passing through the liquid resin P. More specifically, the wafer 10 is held by the holding means 3 of the dryness detection device 2 for which the light source 62 has been selected in the light source selection step described above, and is positioned directly below the condenser 60 of the dryness detection means 6 described above.

[0029] Next, the light source 62 of the dryness detection means 6 is activated to irradiate light L0, and the light L0 transmitted through the beam splitter 64 is irradiated onto the liquid resin P of the wafer 10. As shown in FIG. 3(b), the light L0 irradiated onto the liquid resin P passes through the liquid resin P, reaches the surface 10a of the wafer 10, is reflected, and further passes through the liquid resin P to become light L1, which reaches the beam splitter 64. The light L1 that reaches the beam splitter 64 is reflected by the beam splitter 64 and is guided to the optical path where the light receiving means 7 is disposed. As described above, a bandpass filter 65 is disposed between the beam splitter 64 and the light receiving means 7. The bandpass filter 65 of this embodiment is a filter that transmits only light in the wavelength range selected in the wavelength selection process described above. In this embodiment, for example, the bandpass filter 65 is set to transmit only light in the wavelength range of 1900 to 1980 nm. After passing through this bandpass filter 65, the light L2 reaches the light receiving means 7, and the amount Q of light L2 detected by the light receiving means 7 is transmitted to and stored in the control means 100, completing the light receiving step. The control means 100 is provided with a determination means 110, which performs a determination step of determining whether the liquid resin P has dried or not based on the amount Q of light received by the light receiving means 7 and a predetermined threshold Q2. Here, the threshold Q2 is determined in advance, for example, by the procedure described below, and is stored in the control means 100.

[0030] 4, the horizontal axis represents the dryness (%) of the liquid resin P, and the vertical axis represents the light intensity (mV) measured by the light-receiving means 7. As can be seen from this conceptual diagram, when the liquid resin P supplied to the wafer 10 is not completely dry (0%), the light intensity Q1 (e.g., 1.0 mV) received by the light-receiving means 7 is the lowest. This is because, as described above, water contained as a solvent has the property of absorbing light with a wavelength of 1940 nm, and the 1940 nm light contained in the light L0 is absorbed to the maximum extent by the water solvent as it passes through the liquid resin P. As the water contained in the liquid resin P evaporates and the dryness of the liquid resin P increases, the amount of light with a wavelength of 1940 nm absorbed by the liquid resin P decreases, and the light intensity Q measured by the light-receiving means 7 increases as the resin becomes drier, as shown in the figure. Then, when a sufficient amount of time has passed since the liquid resin P was supplied to the surface 10a of the wafer 10 and the liquid resin P has completely dried (dryness 100%), the light with a wavelength of 1940 nm is not absorbed by the liquid resin P due to the action of water, and the maximum light intensity Q10 (e.g., 10.0 mV) is measured. Then, in order to determine the dryness of the liquid resin to a level that will not cause any problems when processing the wafer 10 by ablation processing, for example, a light intensity Q9 at which the dryness is 90%, which is lower than the light intensity Q10, is selected as the threshold Q9 for determining that the liquid resin is sufficiently dry. This threshold Q9 is determined in advance by experiment and stored in the control means 100.

[0031] With the threshold value Q9 stored in the control unit 100, the flow chart of the determination unit 110 shown in FIG. 5 is executed to perform the determination process. More specifically, in the dryness detection device 2, the light source 62 of the dryness detection unit 6 irradiates the liquid resin P on the surface 10a of the wafer 10 with light L0, allowing the light L0 to pass through the liquid resin P, and the amount of light Q detected by the light receiving unit 7 is detected (step S1). Next, it is determined whether the amount of light Q is greater than the threshold value Q9 (step S2). If the amount of light Q is equal to or less than the threshold value Q9 (No), this indicates that the 1940 nm wavelength light of the light L0 is absorbed and the amount of light Q is low. This indicates that a large amount of water, which is the solvent, is present in the liquid resin P and that the liquid resin P is not sufficiently dried (step S3), and the process returns to step S1. On the other hand, if the amount of light Q is greater than the threshold value Q9 (Yes) in step S2, it is determined that the water, which is the solvent, has been sufficiently reduced from the liquid resin P and that the liquid resin P has dried to a predetermined level, and the process is determined to have completed drying (step S4). This completes the dryness detection method of this embodiment.

[0032] As described above, once the drying of the liquid resin P is detected by the dryness detection method of this embodiment, the wafer 10 is transported to a laser processing device (not shown), and a laser beam of a wavelength that is absorbable by the wafer 10 is irradiated from the front surface 10a side of the wafer 10 along the intended division line 14, thereby performing ablation processing and dividing the wafer 10 into individual device chips.

[0033] The dryness detection method and dryness detection device of this embodiment make it possible to reliably determine whether the liquid resin P applied as a protective film to the wafer 10 has dried, and it becomes possible to perform ablation processing by irradiating the wafer 10 with a laser beam when the liquid resin P is reliably dry. This eliminates the problem that even if a metal film such as TEG is formed on the planned division lines 14, it will peel off during the ablation processing, degrading the quality of the device. Furthermore, since there is no need to spend more time than necessary on drying, productivity is improved.

[0034] In the above embodiment, the solvent for the liquid resin P is water. However, the present invention is not limited to liquid resins that use water as the solvent. For example, the solvent contained in the liquid resin may be acetone or hexamethyl. When the solvent is acetone, the wavelength of light absorbed by acetone is 220 to 330 nm. Therefore, a deuterium lamp emitting light of 200 to 400 nm is selected as the light source 62, and a bandpass filter 65 that transmits only light of wavelengths from 220 to 330 nm is provided. Note that the light emitted from the deuterium lamp mainly contains light in the wavelength range absorbed by acetone, so the bandpass filter 65 that transmits only light of wavelengths from 220 to 330 nm can be omitted. Furthermore, when the solvent is hexamethyl, the wavelengths of light absorbed by hexamethyl are 350 nm and 500 nm. Therefore, a short-arc xenon lamp emitting light of 250 to 1500 nm can be selected as the light source 62. In this case, the bandpass filter 65 of the dryness detection means 6 described above can be set to transmit only wavelengths of, for example, 340 to 360 nm, and the light receiving means 7 can detect the amount Q of light L2 that has passed through the liquid resin P.

[0035] In addition, if the thickness of the protective film formed by the liquid resin P, the concentration of the solvent contained in the liquid resin P, or the type of solvent is changed, the light source 62 and the bandpass filter 65 are changed, and the threshold value Q9 used in the above judgment process is also recalculated by experiment each time in accordance with the above procedure and stored in the control means 100.

[0036] Furthermore, in the above-described embodiment, the light L0 is irradiated onto the surface 10a of the wafer 10 and reflected therefrom, so that the light emitted from the light source 62 and passing through the liquid resin P is received by the light receiving means 7. However, the present invention is not limited to this. For example, if the wafer 10 and the adhesive tape T are made of a material that can transmit light L0, an opening (not shown) may be formed in the chuck table 35 that holds the wafer 10, and the bandpass filter 65 and the light receiving means 7 may be disposed on the side of the adhesive tape T that supports the wafer 10, as shown in FIG. 6, so that the light L2 that has passed through the liquid resin P, the wafer 10, and the adhesive tape T is received by the light receiving means 7. However, in this case, it is expected that light will also be absorbed by the wafer 10 and the adhesive tape T, making it difficult to set the threshold Q9. Therefore, the embodiment described above based on FIG. 3 is preferable. Furthermore, in the above embodiment, the dryness detection device 2 is described as an independent device, but the present invention is not limited to this, and it may be incorporated into a laser processing device that irradiates a laser beam to perform ablation processing on the wafer 10. [Explanation of symbols]

[0037] 2: Dryness detection device 2a: Base 3: Holding means 35: Chuck table 36: Vacuum chuck 4. Transportation 5:Frame body 6: Dryness detection means 60: Concentrator 61: Condenser lens 62: Light source 63: Reflective mirror 64: Beam splitter 65: Bandpass filter 7: Light receiving means 10: Wafer 10a: surface 12: Device 14: Planned division line 14 20: Protective film forming device 22: Spinner table 24: Liquid resin supply nozzle 100: Control means 110: Judgment means (flowchart)

Claims

1. A method for detecting drying of a liquid resin containing a solvent, comprising: a wavelength selection step of selecting a light absorption wavelength of the solvent; a light source selection step of selecting a light source that includes light of the selected wavelength; a light receiving step of irradiating the liquid resin with light and receiving the light that has passed through the liquid resin; a determining step of determining that the solvent has evaporated and dried when the amount of light of the wavelength absorbed by the solvent exceeds a predetermined threshold in the light receiving step; The present invention is configured to include: A dryness detection method in which light from the light source selected in the light source selection process is irradiated onto a liquid resin from which the solvent has evaporated and dried, the light that passes through the liquid resin is received to measure the amount of light, and a value below this amount of light is selected as the threshold value.

2. The dryness detection method described in claim 1, which is performed before performing ablation processing using laser beam on a wafer coated with the liquid resin, and the judgment step determines whether the liquid resin has reached a dry state suitable for ablation processing using laser beam.

3. 3. The method for detecting dryness according to claim 1, wherein the liquid resin is a water-soluble resin and the solvent is water.

4. 4. The method for detecting dryness according to claim 3, wherein the wavelengths of light absorbed by water are 1450 nm, 1940 nm, and 2900 nm, and the light source selection step selects a light source that contains light of any one of the wavelengths.

5. A dryness detection device having a dryness detection means for detecting dryness of a liquid resin, The dryness detection means a light source emitting light of a wavelength corresponding to the light absorption wavelength of a solvent contained in the liquid resin; a light receiving means for receiving light that has been irradiated from the light source and passed through the liquid resin; a determining means for determining whether the amount of light having a wavelength absorbed by the solvent exceeds a threshold value based on the amount of light received by the light receiving means, and determining whether the liquid resin has dried; The present invention is configured to include: The threshold value is determined by irradiating light from the light source onto a liquid resin that has been dried after the solvent has evaporated, receiving the light that has passed through the liquid resin, and measuring the amount of light, and selecting a value below that amount of light as the threshold value.

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