JP4565663B2 - Droplet shape measuring method and apparatus - Google Patents

Description

  The present invention relates to a shape measuring method and apparatus for accurately measuring the shape of minute droplets arranged on a substrate using a diffraction pattern.

  Usually, when measuring the shape of a droplet using a contact angle meter, first, a liquid is dropped on a target substrate to form a droplet having a diameter of about 1 mm. Thereafter, a method has been used in which the formed droplet is imaged from a direction parallel to the substrate, and the contact angle and the shape of the droplet such as the droplet are measured from the captured image of the droplet. In order to evaluate wettability for a region of 100 μm square or less, it is necessary to form a droplet having a diameter of 100 μm or less on a substrate and measure the shape.

  When using a conventional contact angle meter to measure the shape of a minute droplet with a diameter of 100 μm or less, the droplet that is the object to be measured is much smaller than in the normal case. High resolution is required. Therefore, it is not practical from the viewpoint of cost to provide an imaging device having such a high function.

  On the other hand, as an effective method for measuring the shape of a minute object having a size of 100 μm or less, a shape measuring technique using an interferometer using an optical interference phenomenon is conventionally known.

  Since the shape measurement technique using an interferometer uses the interference phenomenon of light, it is possible to measure the shape of an object with the accuracy of light wavelength, that is, submicron or less. For this reason, the shape measurement technique using an interferometer is widely used as a method for evaluating the shape of a workpiece in the field of semiconductor microfabrication.

  Among conventional interferometers, the main ones are listed as methods for evaluating the surface shape.

  According to the reflection type interferometer described in Patent Document 1, first, laser light is obliquely incident on a substrate having a regularly arranged pattern. Then, by analyzing the diffraction pattern generated upon incidence, the film thickness of the regularly arranged pattern formed on the substrate can be measured.

  In this technique, a diffraction pattern to be generated is calculated in advance based on optical theory and used as a determination table, and when measuring the film thickness, the determination table is searched to extract the film thickness when the diffraction intensity is closest.

  In the reflection interferometer described in Patent Document 2, a method using polarized light has been proposed. This is because, for example, by applying a coating that reflects the S-polarized light component of the light beam and transmits the P-polarized light component on the transparent parallel plate placed in front of the sample, the laser light that is incident on the sample is used as the reference light and the sample light. The diffraction pattern is obtained by dividing into two and interfering with each other.

  Patent Document 3 describes a transmission interferometer. There has been proposed a method for obtaining a phase difference of a phase region from a diffraction pattern formed by the transmitted light, in which a pattern having a phase region that causes a phase difference is formed with respect to the transmitted light of a transparent region. Here, linearly polarized light is transmitted through a birefringent prism and a condenser lens, separated into two light beams having different polarization directions, and irradiated onto a sample. The two light beams that have passed through the sample are recombined by the birefringent prism, and an interference image is generated on the image plane. Since the contrast of the interference image changes depending on the phase difference between the two light beams, the phase difference on the sample can be detected by evaluating the diffraction pattern.

JP 2002-277216 A JP 2001-41724 A JP-A-8-94444

  However, the above-described technique for measuring the surface shape of a fine workpiece using the light diffraction pattern has the following problems when used for droplets.

Since the technique of Patent Document 1 irradiates the laser from an oblique direction, when the measurement target is a droplet, a portion where the laser beam is not irradiated is generated.
Therefore, when the optical system described in Patent Document 1 is applied to droplet shape measurement, the shape cannot be obtained accurately.

  In the measurement method using the phase shift method using the reflective optical system described in Patent Document 2, in order to measure the shape, the measurement object is moved or the phase of light incident on the object is changed, and at least It was necessary to measure two or more types of interference fringes. For this reason, measurement takes time.

  Therefore, it is difficult to measure the shape of a minute droplet that evaporates in a few seconds.

  In addition, a mechanism for moving the measurement object or a mechanism for changing the phase of light is necessary, and the cost and complexity of the apparatus configuration are also problems.

  In the phase shift method using the transmission optical system described in Patent Document 3, the film thickness can be measured by the phase difference, but the shape of a droplet or the like whose height changes sharply with respect to the substrate Is difficult to measure.

  In addition, it takes time to measure, and a mechanism for moving the measurement object is necessary, and a mechanism for changing the phase of light is necessary, which is also difficult in terms of measurement time, cost, and complexity of the apparatus configuration. .

  Therefore, it is still difficult to quickly and easily obtain the shape of a droplet having a diameter of about 20 to 100 μm arranged on the substrate.

  It is an object of the present invention to form a droplet having a diameter of 100 μm or less arranged on a substrate, which is difficult to measure with the prior art, with a simple configuration as much as possible and capable of accurately measuring the droplet shape. It is to provide a measurement method and apparatus.

The droplet shape measuring method of the present invention is a diffracted light generated when a laser beam is irradiated perpendicularly to the substrate with respect to a droplet placed on the substrate and the laser beam is irradiated to the droplet. A first step of detecting interference fringes ( diffraction patterns ) caused by mutual interference;
And a second step of determining the shape of the surface of the droplet from the refractive index of the droplet and the detected interference fringe ( diffraction pattern ) .

  In the present invention, it is possible to accurately and quickly measure the shape of a droplet having a contact diameter of 100 mm or less with a simple configuration.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an optical system 2 capable of adjusting the beam diameter of the laser light L is installed for the laser light source 1 whose phase state is known. The substrate 3 is installed perpendicular to the optical axis, and droplets 4 are arranged on the substrate 3 in advance. The laser beam L is irradiated onto the droplet 4 from the back side of the substrate 3, and the resulting diffraction pattern is imaged on the detector 5 (screen). The diffraction pattern is imaged by the imaging device 6 and input to the analysis device, and the shape of the droplet 4 is detected.

  The flow of the droplet shape measuring method of the present invention will be described with reference to FIG.

  First, step S <b> 1 is a step of irradiating the droplet 4 disposed on the substrate 3 with the laser beam L. Subsequently, as a step of S2, a diffraction pattern generated by interference of diffracted light generated by the irradiated laser light L is imaged on the detector 5. In step S3, the intensity distribution of the diffraction pattern is recorded using the imaging device 6 or the like. In addition, you may perform the process of S2, S3 collectively using an area sensor etc. In step S4, the diffraction pattern recorded in step S3 is input to the analyzer and converted into numerical data. In the process of S5, the diffraction pattern recorded in the database of diffraction patterns prepared for each of the contact diameter, the contact angle, and the refractive index prepared in advance by calculation using the analysis device, and converted in the process of S4. Compare the numerical data of the diffraction pattern and find the most consistent one. In step S6, the most matched database shape value is output as a measurement result.

  The droplet shape measuring method according to the present invention includes a first step of detecting a diffraction pattern generated by irradiating the droplet 4 on the substrate 3 with the laser light L, the refractive index of the droplet 4 and the detected refractive index. A second step of determining the shape of the droplet 4 from the diffraction pattern.

  Next, the analysis apparatus will be described with reference to FIG.

  The analysis device 7 uses a PC including a video board 71, a CPU 72, a memory 74, and a storage area 73. However, when the diffraction pattern is stored in the external storage area 77 in advance, the video board 71 is not essential. The analysis device 7 is connected to an imaging device 6 for acquiring a diffraction pattern, a display 75 for displaying a user interface, a keyboard 76 for performing various inputs, and an external storage area 77 as required. .

  In the analysis apparatus 7 having such a configuration, the following processing is performed. First, a diffraction pattern is acquired by the video board 71 and the imaging device 6 of the analysis device 7. This diffraction pattern is stored in the storage area 73. The image data stored in the storage area 73 receives an appropriate command by input means such as a keyboard 76, is stored in the memory 74, and is converted into numerical data in a format used for analysis by the CPU 72. The converted numerical data is written in the memory 74 and then stored in the storage area 73. Next, the database is read into the memory 74.

  At this time, the database may be stored in the storage area 73 inside the analysis device 7 or may be stored in the external storage area 77. The read database is input to the memory 74. Numerical data to be analyzed is read from the storage area 73 into the memory 74, and the CPU 72 performs collation with the database. The most consistent result is displayed on the display 75. Although the analyzer 7 has such a configuration, it is needless to say that the analyzer is not limited to the case described above.

  As the laser light source 1 of the present invention, it is preferable to use a laser light source whose phase state is known, such as having a phase plane perpendicular to the optical axis at the incident position on the object.

  There are various types of lasers depending on the laser medium such as gas laser, solid state laser, laser diode, etc., but the absorption spectrum and detection method of droplet 4 in terms of wavelength, wavelength width, beam shape at the time of emission, beam intensity, etc. Select the best one according to your needs. It is particularly preferable to use a gas laser having a perfect beam shape and good beam quality.

  Although the shape of the laser beam depends on the shape of the droplet 4, it is preferably a perfect circle from the viewpoint of ease of measurement and analysis. The beam diameter is preferably larger than the representative length of the droplet 4. Since the phase state of the laser beam only needs to have a plane perpendicular to the optical axis at the incident position on the droplet 4, the collimating optical system that converts the beam into a parallel beam also condenses that the beam is the thinnest on the substrate 3. Either optical system can be used. Therefore, the optical system 2 that adjusts the laser beam may be any system that allows the laser beam to have an equiphase surface with an arbitrary diameter on the substrate 3.

  Depending on the state of the laser light and the detection method, the optical system 2 for adjusting the laser light may not be used.

  The material of the substrate 3 is determined depending on whether a transmission optical system or a reflection optical system is used. In the case of a transmission optical system in which laser light is vertically incident from the back surface of the substrate 3 and the laser light is transmitted through the droplet 4, the substrate 3 needs to be transparent to the laser light to be used. As the surface state of the substrate 3, there is no problem even if there is a thin film or pattern on the surface as long as it has a thickness equal to or less than the wavelength of the laser light to be used and is transparent.

  Further, as shown in FIG. 5, when a reflection optical system that directly irradiates the droplet 4 with laser light from the laser light source 21 through the optical system 22, the surface roughness is small with respect to the wavelength. If the substrate does not absorb the laser beam, there is no particular limitation on the type and material of the substrate.

  However, if there is a pattern due to a metal film or the like on the substrate surface, or if the substrate itself has a step and has a structure larger than the wavelength, it affects the shape of the generated diffraction pattern, so grasp the substrate structure in advance. There is a need.

The droplet 4 is made of a liquid having at least one composition, a soft material, or the like.
The size of the droplet 4 for which the shape measuring method according to the present invention is particularly effective is that the contact diameter is 100 μm or less and the refractive index is known.

  In addition, as a measuring object in this invention, it can measure not only a droplet but if it is a shape of an axial object with respect to the normal line direction of a board | substrate. For example, it is possible to measure the shape of a measurement object by arranging a microlens or the like on the substrate.

  Now that the light source and the measurement object have been described in detail, the optical system characteristic of the present invention will be described below.

  The inventors of the present invention have the optical system 2 according to the present invention, since the object to be measured is the droplet 4, as a basic configuration, the laser light L is perpendicular to the substrate 3 on which the droplet 4 is disposed. I found a good thing.

  The reason for this is as follows.

  First, the transmissive optical system 2 will be described. In the transmissive optical system 2, when the laser light L is incident obliquely on the substrate 3 on which the droplet 4 is placed, the laser light L is transmitted through the substrate 3 in addition to the diffracted light from the droplet 4. Refraction and scattering must be taken into account. For this reason, the parameters used for the analysis are increased as compared with the case of vertical incidence. In addition, the intensity distribution of the observed diffraction pattern is not concentric but complicated, and the number of data to be calculated increases. For these reasons, making the laser light L obliquely incident on the transmissive optical system 2 increases measurement and analysis time and complicates the process, and is not suitable for practical use.

  Next, the reflective optical system 2 will be described. In the case of the reflection type, when the laser beam L is incident obliquely, a portion where the laser beam L does not hit may occur due to the shape of the droplet 4. Further, unless the incident light angle is larger than the contact angle of the droplet 4, the reflected light on the incident-side droplet surface does not reach the detector 5.

  Therefore, in the reflection type, when the laser light L is incident obliquely, it becomes difficult to accurately detect the diffracted light from the droplet surface. Therefore, highly accurate measurement is not possible. Furthermore, as in the case of the transmissive type, the intensity distribution of the diffraction pattern becomes complicated, and there is a problem that it takes a lot of time for analysis and database calculation.

  From the above, in order to measure the shape of a droplet placed on a substrate at high speed and with high accuracy using simple means, it is necessary to make laser light incident vertically as in the present invention.

  The material of the detector 5 is not particularly limited as long as it can project a diffraction pattern. A diffraction pattern is projected onto a screen using a material that scatters light, and the projected pattern is imaged using the imaging device 6, or an arbitrary area of the diffraction pattern is directly captured using an optical sensor such as a photodiode. A method for detection is conceivable. As the material of the screen, tracing paper, a diffusion plate, opal glass, etc. can be considered.

  When imaging a diffraction pattern using the imaging device 6, the positional relationship among the laser light source 1, the droplet 4, and the detector 5 is important. As shown in FIG. 1A, in order to accurately photograph a diffraction pattern of diffracted light generated by causing laser light L to enter the droplet 4 perpendicularly and causing the laser light L to enter. It is good to project on the detector 5 (screen) and to set the imaging device 6 vertically.

  If the detector 5 is a transmissive screen, it is possible to shoot from the back of the screen, so the imaging device 6 can be installed perpendicular to the optical axis. When photographing from the front, an image perpendicular to the optical axis can be photographed by photographing using a half mirror. However, it is difficult to install vertically otherwise. When the imaging device 6 is installed in a position other than vertical, it is necessary to correct the shape of the droplet from the diffraction pattern based on the inclination and distance of the imaging device 6.

  As the type of the imaging device 6, a digital single-lens reflex camera, a CMOS, a CCD camera, or the like that has a large dynamic range with respect to luminance and a variable shutter speed is preferable. In addition, when a camera with a high frame rate is used as an imaging means, it captures changes with time of droplets that occur in a very short time, such as the evaporation process of a minute droplet having a contact diameter of 100 μm or less, which is the measurement object of the present invention. You can also.

  In the analysis device 7, if a diffraction pattern data is input from the imaging device 6 and an object shape can be measured from the diffraction pattern, there is no problem with a general PC.

  In order to determine the shape of the object on the substrate 3 from the diffraction pattern detected by the detector 5 or the imaging device 6, it is necessary to determine the shape of the measurement object based on the optical theory from the analysis result of the diffraction pattern.

  The following can be considered as a method for specifying the shape from the diffraction pattern.

  In the first method, all shapes that can be predicted are extracted, objects having the respective shapes are actually prepared, the diffraction pattern is detected by the optical system 2 described above, and the database is created. This is a method for comparison with the obtained diffraction pattern.

  The second method is a method in which all predictable shapes are extracted, the diffraction pattern generated by the optical system 2 is calculated based on optical theory, a database is created, and the obtained diffraction pattern is compared. is there.

  The third method is a method of calculating the shape of the droplet 4 by calculation based on optical theory for each detected diffraction pattern.

  From these methods, an optimum method may be selected according to the shape of the object and the performance of the analysis apparatus.

  The first method can be easily implemented. In the present embodiment, a method for determining the shape of a droplet from the obtained diffraction pattern will be described below by taking the second method as an example.

  First, a database is created in advance before measuring the shape with the optical system 2 of the present invention described above. This database is based on the numerical calculation based on the optical theory for the droplet 4 when the conditions are the same as the actual measurement such as the refractive index of the droplet 4 and the distance between the droplet 4 and the detector 5 (screen). The numerical data relating the shape of the droplet and the diffraction pattern is recorded. In this measurement, it is desirable that all the objects to be measured have a droplet shape, and that a plurality of numerical data corresponding to the contact diameter and the contact angle are stored for each refractive index. This database creation step corresponds to the step S0 in FIG.

  As described above, the droplet shape measuring method of the present invention can be suitably used for measuring the shape of a minute droplet having a size of 100 μm or less because it quickly measures the shape with a simple apparatus configuration.

  In addition, if the measurement object is made of a liquid that easily evaporates, the diffraction pattern changes sequentially with time. Therefore, if the shape of the measurement object at the time determined at an appropriate time interval is determined, it is possible to observe a change with time of the shape of the measurement object that easily evaporates.

  FIG. 1A shows a droplet shape measuring apparatus according to the first embodiment. This droplet shape measuring apparatus irradiates a laser beam L whose beam diameter is adjusted by the optical system 2 from the back surface of the droplet 4 on the substrate 3 and detects a diffraction pattern by the diffracted light generated by transmitting the droplet 4. This is detected by the device 5. A transmissive screen is used as the detector 5, and the imaging device 6 is installed so that an image perpendicular to the optical axis can be obtained from the back surface of the detector 5. The image captured by the imaging device 6 is subjected to image processing by the analysis device 7 and the shape of the droplet 4 is measured.

  As the laser light source 1, a He-Ne laser having a wavelength of 632.8 nm was used. The injection diameter was 0.8 mm.

  The optical system 2 was adjusted so that the laser beam diameter was about 150 μm on the substrate 3. The optical system for adjusting the beam diameter is composed of a beam expander and a plano-convex lens. In this example, a beam expander with a magnification of 3 times optimized for a wavelength of 632.8 nm was used. A plano-convex lens having a focal length of 400 mm was used. With this configuration, the beam diameter becomes the smallest at the position of the droplet 4 on the substrate 3, and the phase plane is adjusted to be a horizontal plane with respect to the optical axis. For the substrate 3 on which the droplets 4 are arranged, glass having a thickness of 0.7 mm was used. In this example, ethylene glycol droplets were used as the measurement object.

  The refractive index of ethylene glycol is 1,431 at room temperature.

  As the detector 5, tracing paper was used as a transmissive screen. At this time, the optical axis of the laser light source 1 and the screen were adjusted to be vertical. In the adjustment, a mirror was attached to the screen holder, and the angle of the holder was adjusted so that the return light of the laser light L returned to the laser light emitting portion.

  The distance between the screen which is the detector 5 and the substrate 3 was 5 cm.

  The photographing apparatus 6 is a CMOS camera having a pixel number of 1024 × 1024 and a macro lens having a focal length of 55 mm. As a result, the field angle was about 50 × 50 mm, and the resolution was about 42 μm / pixel.

  One drop of ethylene glycol was dropped on the substrate 3 using an inkjet method, and then the substrate 3 was placed on the optical axis. The position of the substrate 3 was adjusted so that the ethylene glycol droplets were irradiated with the laser beam L, and it was visually confirmed that the diffraction pattern appeared on the screen, and then the diffraction pattern was photographed by the imaging device 6 such as a camera.

  FIG. 2 shows a photographed image of the diffraction pattern. As shown in FIG. 2, the diffraction pattern was a concentric pattern.

  FIG. 1B schematically shows a state near the center of the concentric circles in the diffraction pattern image of FIG. As the distance from the center starts from the center 8 of the diffraction pattern, the dark part 9, the bright part 10, the dark part 11, and the light and dark are repeated.

  Before photographing the diffraction pattern, the laser beam L alone was irradiated onto the substrate 3 without dropping the ethylene glycol droplets, and the optical axis position on the detector 5 (screen) was obtained. The brightness in the radial direction (illustrated by the arrow in FIG. 1B. The arbitrary position starting from the center of the concentric diffraction pattern may be selected) is measured with the position as the center of the diffraction pattern. When the dark part of the diffraction pattern was defined as the stripe position and the stripe position of the detected diffraction pattern was measured, the positions were 0.46 mm, 0.8 mm, and 1.22 mm in order from the center.

  The ethylene glycol droplets used in this example are tens of pl droplets ejected by inkjet. The droplet 4 of this size has a contact diameter on the substrate 3 of 100 μm or less. A droplet having a contact diameter of about 100 μm or less is extremely less affected by gravity, and its shape is determined only by the surface tension of the substrate 3 and the internal pressure of the droplet 4. In such a case, the droplet shape becomes a part of a sphere. If it is a part of a sphere, the droplet shape can be described by a contact diameter and a contact angle.

  Since the droplet 4 can be described by the contact diameter and the contact angle, it is easy to analyze the diffraction pattern obtained when the laser beam L of the droplet 4 is irradiated.

  Theoretically, the diffraction pattern is specific to the shape and refractive index of the droplet. Therefore, only one droplet shape can be determined from one diffraction pattern.

  In the present invention, it is desirable to measure the shape using a database of droplet shapes and diffraction patterns based on theoretical calculation results.

  In this embodiment, a database recording the relationship between the stripe position, the contact diameter, and the contact angle as shown in FIG. 3 is prepared and used for measuring the shape of the ethylene glycol droplet.

  FIG. 3 is a graph showing the relationship between the fringe position of the diffraction pattern and the contact diameter obtained in this apparatus configuration based on optical theory. Theoretically, it is known that the fringe position near the center is less affected by the contact angle and the refractive index. Therefore, the droplet diameter can be obtained using this figure regardless of the refractive index.

  In FIG. 3, when the primary fringe position and the secondary fringe position are set in order from the dark part position closest to the center, the relationship between the fringe positions from the first to the fourth order and the contact diameter is graphed.

  Based on the relationship between the contact diameter and the fringe position as shown in FIG. 3, the estimated contact diameter from the fringe position of the diffraction pattern in FIG. 2 was about 90 μm. Based on this value, the diffraction pattern was calculated by changing the contact angle with respect to the refractive index of ethylene glycol. When the calculated diffraction pattern was compared with the detected diffraction pattern, the good agreement was found to be 44 to 46 degrees.

  Therefore, the shape of this ethylene glycol droplet was considered to be a contact diameter of about 90 μm and a contact angle of 44 to 46 degrees.

  The ethylene glycol droplets in this example evaporated in a few seconds. When the shape of the ethylene glycol droplets was measured at appropriate time intervals along the time-dependent change of the diffraction pattern, changes in the contact diameter and contact angle over time could be measured. Therefore, it can be said that the process of shape change accompanying droplet evaporation can be observed using this apparatus.

[Reference Example 1]
Next, using the same optical system as in Example 1, the shape of the microlens was measured. Microlenses are equivalent in shape to droplets, and the shape can be measured by the same theory. Moreover, since there is no change with time unlike a droplet, it can be measured by another measurement method. By comparing the measurement result of another measurement method with the measurement result of this measurement, it is possible to prove the certainty of the measurement.

  When the refractive index of the microlens was measured using an optical measurement method, it was 1.596 with respect to the laser wavelength used.

  A diffraction pattern was obtained for the microlens formed on the substrate by the same procedure as in Example 1. FIG. 4 shows a diffraction pattern obtained from this microlens. From FIG. 4, the fringe positions were measured to be 1.5 mm, 2.3 mm, and 3.6 mm in order from the center.

  Using FIG. 3, the contact diameter was determined to be about 30 μm. Further, when calculating a diffraction pattern in which the contact angle is changed with respect to the refractive index of the microlens, the diffraction pattern which is in good agreement with FIG. 4 has a contact angle of about 29 degrees or 30 degrees.

  Therefore, it can be said that the shape of the microlens measured by this reference example has a contact diameter of about 30 μm and a contact angle of 29 degrees or 30 degrees.

  In order to confirm the certainty of the measurement result, the shape of the microlens was measured with a confocal microscope. As a result, the contact diameter was 31.2 μm and the contact angle was 28.1 degrees. This value agrees very well with the value measured in this reference example. In particular, comparing the shape measurement with the confocal microscope and the shape measurement result according to this reference example, it is considered that the contact diameter can be measured within an error of about 1 μm and the contact angle within about 2 degrees.

[Reference Example 2]
FIG. 5 shows an example of an apparatus configuration for measuring a diffraction pattern by the reflection optical system. This shape measuring apparatus adjusts the laser light L emitted from the laser light source 21 by the optical system 22 so that the laser light L has an equiphase surface horizontal to the optical axis on the substrate 3. Incidently incident on the drop-shaped measurement object 24. The laser light L incident on the measurement object 24 passes through the droplet-shaped measurement object 24, is reflected by the substrate 3, and exits from the droplet-shaped measurement object 24. At this time, the phase of the laser beam L is shifted in accordance with the shape of the measurement object 24 having a droplet shape, and a diffraction pattern is generated. This diffraction pattern is observed by the detector 5 and photographed by the imaging device 6. The combination of the detector 5 and the imaging device 6 may be a general imaging device such as a screen and a camera that simply captures a diffraction pattern made of tracing paper or the like. Further, the diffraction pattern may be directly recorded as image data by using an area sensor or the like as the detector 5.

  In order to install the screen of the detector 5 perpendicular to the optical axis, a hole through which the laser beam L passes is provided in the center.

  As the laser light source 21, a He-Ne laser having a wavelength of 632.8 nm was used.

  The optical system 22 was set so that the laser beam diameter was about 150 μm at the incident position on the measurement object 24. The beam diameter adjusting optical system 22 is composed of a beam expander and a plano-convex lens. In this reference example, a beam expander with a magnification of 3 times optimized for a wavelength of 632.8 nm was used. A plano-convex lens having a focal length of 400 mm was used. With this configuration, the beam diameter becomes the smallest at the position of the measurement object 24 on the substrate 3, and the phase plane is adjusted so as to be a horizontal plane with respect to the optical axis.

  A microlens different from that used in Reference Example 1 was used as the measurement object 24 in this Reference Example.

  As the detector 5, tracing paper was used as a transmissive screen. At this time, the optical axis of the laser light source 21 and the screen were adjusted to be vertical.

  The distance between the detector 5 (screen) and the substrate 3 was 8 cm.

  The imaging device 6 used a digital single-lens reflex camera with 3504 × 2336 pixels. The field angle was about 70 × 47 mm, and the resolution was about 20 μm / pixel.

  The installation angle of the imaging device 6 is inclined about 20 degrees from the optical axis.

  The substrate 3 on which the microlens was installed was placed on the optical axis, and it was visually confirmed that a diffraction pattern was obtained, and then photographed with a camera.

  FIG. 6 is the right half of the image of the captured diffraction pattern. As shown in this figure, the diffraction pattern was a concentric pattern. At this time, when the stripe position from the center was measured, they were 0.28 mm, 0.44 mm, and 0.74 mm. A graph of the stripe position and the contact diameter for this device configuration is prepared in advance. The contact diameter determined from the measured stripe position was about 49 μm. Similarly to the transmission optical system, a diffraction pattern was calculated using theoretical calculation for the obtained contact diameter of 49 μm, and compared with the measurement result. The contact angle of the closely matched diffraction pattern was about 34 to 37 degrees.

  When the shape of the microlens was measured with a confocal microscope, the contact diameter was 51.3 μm and the contact angle was 35.5 degrees. This value is very close to the value measured in this reference example.

  That is, it was found that the reflection optical system can be measured with an error of about 2 μm in contact diameter and about 2 degrees in contact angle as compared with the confocal microscope.

[Reference Example 3]
In order to compare the measurement results of the reflection optical system and the transmission optical system, the microlens used in Reference Example 2 was measured using the same transmission optical system as in Example 1.

  FIG. 7 is a diffraction pattern obtained by this reference example. The fringe position from the center as in Example 1 was found to be 0.83 mm, 1.33 mm, and 2.12 mm. When the contact diameter was obtained from the graph using these stripe positions, the contact diameter was about 50 μm. The contact angle was measured to be about 35 to 36 degrees. This value is almost the same as the measurement result of the reflection optical system, and also coincides with the measurement result of the confocal microscope.

The droplet shape measuring method using the transmission optical system by Example 1 is demonstrated, (a) is a figure which shows the structure of a shape measuring apparatus, (b) is a schematic diagram which shows the center part of a diffraction pattern. It is a figure which shows the pattern image of a droplet. It is a graph which shows the relationship between the representative length (contact diameter) of an object and the dark part position of a diffraction pattern in case the shape of an object is axisymmetric with respect to a normal line. It is a figure which shows the pattern image of the micro lens by the reference example 1. FIG. It is a figure which shows the structure of the droplet shape measuring apparatus using the reflective optical system by the reference example 2. FIG. It is a figure which shows the pattern image of the micro lens by the reference example 2. FIG. It is a figure which shows the pattern image of the micro lens by the reference example 3. FIG. It is a flowchart which shows the process of the droplet shape measuring method of this invention. It is a block diagram which shows the analyzer used for implementation of the droplet shape measuring method of this invention.

Explanation of symbols

1, 21 Laser light source 2, 22 Optical system 3 Substrate 4 Droplet 5 Detector 6 Imaging device 7 Analysis device

Claims (5)

Interference fringes generated by irradiating laser beams perpendicularly to the substrate with respect to the liquid droplets arranged on the substrate and diffracted light generated when the laser light is irradiated on the liquid droplets. A first step of detecting;
And a second step of obtaining the shape of the surface of the droplet from the refractive index of the droplet and the detected interference fringe .   2. The droplet shape measuring method according to claim 1, wherein the contact diameter of the droplet is 100 [mu] m or less. The second step, the liquid and the shape of the droplet is related, and the interference fringes obtained when that caused the interference fringes in the same conditions as the first step, the detected interference fringes, the The droplet shape measuring method according to claim 1, wherein the shape of the surface of the droplet is obtained by comparison. 2. The droplet shape measuring method according to claim 1, wherein in the second step, the shape of the droplet is obtained by relating the detected interference fringe and the shape of the droplet based on optical theory. . An optical system for irradiating a laser beam perpendicularly to the substrate with respect to the droplet disposed on the substrate and generating interference fringes from the diffracted light from the droplet;
A detector for detecting the generated interference fringes ,
A shape measuring apparatus, wherein the shape of the surface of the droplet is determined from the refractive index of the droplet and the interference fringes .

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