JPH07198348A - Measurement device of surface shape - Google Patents

Abstract

PURPOSE:To accurately measure a surface shape of an object to be measured by a method wherein an emission light emitted on the object including a resist component is obtained from an emission light source in a prescribed of wavelength band having a great reflectivity intensity against a green component of visible rays. CONSTITUTION:An emission system 21 consisting of a second harmonic wave laser device 23 that generates emission rays and a lens group 4 vertically emits a laser light MG on a plane face 8 of an object to be measured and horizontally scans it. The device 23 utilizes a semiconductor laser as an excitation light and consists of, for example, Nd: YAG laser medium that emits a basic wave of the laser light and nonlinear optical element that converts a laser light having a wavelength of 1064mum to the second harmonic wave having a wavelength of 532nm. The laser light MG has a reflectivity intensity of 2.66%, against a resist component of a substrate and the value is not less than 75%, of a maximum reflectivity intensity (3%) of the resist component. As a result, a difference of the reflectivity intensity between a portion with the resist component and a portion without the resist component is reduced so that it is possible to execute the accurate measurement with a high S/N ratio.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 5 and 6) Problem to be Solved by the Invention (FIG. 6) Means for Solving the Problem (FIGS. 1 and 2) Action (FIGS. 3 and 4) Example (FIGS. 1 to 4) Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface profile measuring apparatus, and can be applied to a device for irradiating a surface of a measured object with a laser beam to measure the shape of the surface of the measured object in a non-contact manner.

[0003]

2. Description of the Related Art Conventionally, a surface shape measuring apparatus 1 as shown in FIG. 5, for example, has been used as a non-contact measuring apparatus for measuring the surface shape of an object to be measured. The surface profile measuring apparatus 1 is composed of an irradiation system 2 and a light receiving system 3. Irradiation system 2
Is composed of an irradiation light source laser device 4 for irradiating near-infrared light having a wavelength of emitted laser light of 632 to 830 [nm], a collimator lens 5, a cylindrical lens 6 and a cylindrical lens 7, and the laser light is a linear light. (Hereinafter, this is referred to as a bright line.) The plane to be measured 8 is irradiated.

The irradiation system 2 is arranged so as to be vertically above the object plane 8. The light receiving system 3 includes a CCD (couple charged device) camera 9 for receiving laser reflected light, and an imaging lens 10 for forming an image of a bright line of the laser light on the object plane 8 on the CCD camera 9, and the object to be measured. It is arranged so as to be diagonally upward with respect to the plane.

A flat surface 8 of the object to be measured by the surface profile measuring apparatus 1.
The surface shape measurement of the laser light emitted from the irradiation light source laser device 4 is performed by the collimator lens 5 and the cylindrical lens 6.
The cylindrical lens 7 and the cylindrical lens 7 irradiate the object plane 8 as a bright line from vertically above, and the object plane 8 is horizontally moved in the direction orthogonal to the bright line for scanning.
As a result, the bright lines are collected at the apex of the object plane on the object plane 8 and the reference point.

The reflection of this bright line is reflected by the imaging lens 10 at C.
An image is formed on the light receiving surface of the CD camera 9. The light receiving surface of the CCD camera 9 has a reference surface 8A on the flat surface 8 of the object to be measured and an upper surface 8 of the object.
The reflection of the bright line focused on B is imaged as two observation points having different positions. These two observation points and the object plane 8
In the triangle formed by the reference plane 8A or the upper surface 8B of the object, the reference plane 8A on the object plane 8 is measured by the triangulation method from the distance between the observation points and the viewing angle at the observation points.
The height from the object top surface 8B is calculated.

[0007]

However, when the surface shape is measured by using a near infrared laser beam as the irradiation light source laser, if the object to be measured has a resist component, for example, as shown in FIG. The reflectance is 780
GaAlAs (gallium alminium arsenic) laser of [nm] is 0.54 [%], and the wavelength of emitted light is 670 [nm].
lGaInP (aluminium gallium indium phosphorus)
Since it is as low as 0.28 [%] with a laser, it becomes difficult to obtain a sufficient amount of light with a light receiving element. Further, for example, in a solder portion containing no resist component, the reflectance becomes about 70%, and a large difference occurs in the light intensity sensed by the light receiving element, and the difference in the video signal intensity converted from the light intensity becomes very large.

Therefore, for example, when the light receiving level is set so that the video signal of the solder portion is not saturated, the SN ratio of the video signal in the portion including the resist component is deteriorated, which makes it difficult to accurately measure the surface shape. Atsuta Further, when the irradiation light is condensed linearly, there is a problem that the line width of the reflected light changes between the portion containing the resist component and the portion not containing the resist component, and accurate shape measurement cannot be performed.

The present invention has been made in view of the above points, and an object thereof is to propose a surface shape measuring apparatus capable of accurately measuring the surface shape of an object to be measured including a resist component.

[0010]

In order to solve such a problem, in the present invention, an irradiation light source 23 which emits light in a wavelength band of 475 to 560 [nm] and a light which is emitted from the irradiation light source 23 are measured. Lens system 24 that collects light as a bright line on 8
And a light receiving means 9 for receiving the reflected light of the bright line condensed on the object to be measured 8, and the object to be measured 8 on the light receiving surface 9A of the light receiving means 9.
The image forming lens 10 forms an image of the reflected light of the bright line 40 condensed above.

[0011]

[Function] By setting the wavelength band of the irradiation light with which the DUT 8 including the resist component is irradiated to 475 to 560 [nm],
A sufficient reflectance intensity can be obtained in the portion containing the resist component, and the difference in reflectance intensity from the portion not containing the resist component can be reduced. As a result, the reflected light on the DUT 8 can be easily measured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 5 are designated by the same reference numerals, numeral 20 indicates an apparatus for measuring the surface shape as a whole, and an irradiation system 21 for condensing laser light on the plane 8 to be measured.
And a light receiving system 22 for receiving the bright line of the laser beam on the object plane 8 by the CCD camera 9. The surface shape measuring device 20 is an automatic control device (not shown).
Is used to horizontally scan the object plane 8 to measure the surface shape of the entire surface of the object plane 8.

The irradiation system 21 comprises a second harmonic laser device 23 which serves as an irradiation light source, and a lens group 24 which focuses the laser light MG emitted from the second harmonic laser device 23 on the object plane 8. Composed. The irradiation system 21 is the object plane 8
Is arranged vertically above the object plane 8 and is horizontally scanned so that the emitted laser beam MG is vertically irradiated to the object plane 8. The second harmonic laser device 23 uses a semiconductor laser as the excitation light and emits the fundamental wave laser light Nd:
Wavelength 1064 emitted from YAG (neodymium yittrium alminium garnet) laser medium and Nd: YAG laser medium
SHG (second harmonic generation) for wavelength conversion of fundamental wave laser light of [μm] into second harmonic of wavelength 532 [nm]
It consists of a nonlinear optical element.

The lens group 24 comprises a collimator lens 25, a cylindrical lens 26 and a spherical lens 27. The laser light MG emitted from the second harmonic laser device 23 becomes parallel light via the collimator lens 25. Further, a cylindrical lens 26 and a spherical lens 27
And linearly condensed by and about NA (numerical aperture)
0.025, depth of focus about 400 [μm], line width 50 to 100 [μm] in the direction of the optical axis ± 2.5 [mm] from the focal point, line length direction 7
-8 plane of the object to be measured as a bright line composed of laser light of 8 [mm]
Is irradiated. The laser irradiation light amount on the object plane 8 is 50 [μm] in the line width and 50 [μW / mm] in the line length direction.

The laser light MG irradiated here has a reflectance intensity of 2.66 [%] with respect to the resist component on the substrate and has a maximum reflectance intensity MAX (about 3 [%]) of the resist component.
It reaches 75% or more. This makes it possible to reduce the difference in reflectance intensity from the portion not containing the resist component.

Next, the configuration of the light receiving system 22 is the same as that of the light receiving system 3 in the surface profile measuring apparatus 1 and the imaging lens 10 and CCD.
It is composed of a camera 9. Here, the optical axis AX of the imaging lens 10 and the optical axis BX of the irradiation system 21 are set so that the angle θ is 45 degrees, and the lens surface 10A of the imaging lens 10 is further set.
The angle φ between the extension line of the line and the extension line of the image plane 9A on the CCD camera 9 is set to 45 degrees. Further, the imaging lens 10 having a magnification of 1 is used for the light receiving system 22. In this way, the irradiation system 21 and the light receiving system 22 are arranged on the basis of the Sheamplf principle.

That is, as shown in FIG. 2, the extension line AB of the object plane 30 and the extension line CD of the image plane 31 and the extension line OP of the lens surface 32A orthogonal to the optical axis QR of the lens 32 are defined by the Sheamplf principle. Are set so that they intersect at one point, the angle between the optical axis QR of the lens 32 and the object plane 30 is θ, the extension line CD of the image plane 31 and the lens plane 32.
If the angle formed by the extension line OP of A is φ and the magnification of the lens 32 is M, then

[Equation 1] The relational expression shown in is established. As a result, all the images of the object plane 30 formed by the lens 32 on the image plane 31 come into focus.

In the above example, the angle θ is 45 degrees,
Since the angle φ is 45 degrees, and the lens magnification is 1, substituting these into the equation (1) satisfies the Schaimfluff principle, and accordingly, the imaging lens 10 connects the imaging surface 9A of the CCD camera 9 to the imaging surface 9A. All the images on the object plane 8 to be imaged are in focus.

In the above configuration, for example, the second harmonic laser device 23 irradiates the laser beam MG on the object surface 8 to be measured on the semiconductor mounting substrate after applying the cream solder, so that the object surface 8 to be measured is irradiated. Surface shape measurement is started. The laser light MG emitted from the second harmonic laser device 23 is collimated through the collimator lens 25, is linearly condensed by the cylindrical lens 26 and the spherical lens 27, and is irradiated onto the object plane 8. It At this time, a bright line 40A is observed with respect to the reference plane 8A on the object plane 8 and a bright line 40B is observed with the object upper surface 8B whose height is to be measured.

The bright lines 40A and 40B are imaged on the light receiving surface of the CCD camera 9 through the imaging lens 10, as shown in FIG. That is, the reference plane 8 of the object plane 8
The bright line 40A of A is the bright line 41A, and
The bright line 40B of B is imaged on the light receiving surface of the CCD camera 9 as a bright line 41B. At this time, the height h from the reference surface 8A to the object upper surface 8B is observed as a shift h'between the imaged bright lines 41A and 41B.

Here, even when the resist component is contained on the flat surface 8 of the object to be measured, the green laser light M having a wavelength of 532 [nm] is obtained.
The reflectance of G is 2.66 [%], which is improved by 20 [dB] or more compared with the conventional one, so that the difference from the reflectance intensity in the cream solder is reduced and accurate measurement with a high SN ratio can be performed. Further, even if the bright line 40 irradiated on the object plane 8 is linearly condensed, the line width becomes constant between the portion containing the resist component and the portion not containing the resist component, and more accurate measurement can be performed.
Further, since the laser light MG having a wavelength of 532 [nm] is green visible light, the irradiated portion on the object plane 8 can be visually observed, which allows the laser beam MG on the object plane 8 without using the reference light laser. Can be applied.

When the bright lines 41A and 41B condensed on the light receiving surface of the CCD camera 9 are converted into a video signal, as shown in FIG.
As shown in, the positions of the bright lines appear as peaks 42A and 42B of the video signal, respectively. Here, the pixel number a between the H sync on the reference surface 8A and the peak 42A and the pixel number b between the H sync on the object upper surface 8B and the peak 42B are read. As a result, the difference between the number of pixels a and the number of pixels b is measured as the distance between the observation points, and the height from the reference surface 8A to the object upper surface 8B is calculated using the triangulation method from the viewing angle with the bright lines 42A and 42B. To be done.

According to the above configuration, the surface shape is measured by irradiating the green laser beam having the wavelength of 532 [nm], so that even when the measured object contains the resist component. By obtaining a sufficient reflectance intensity, the reflected light of the portion containing the resist component and the reflected light of the portion not containing the resist component can both be detected with a good SN ratio by the same irradiation light. Further, the line width of the reflected light does not change between the portion containing the resist component and the portion not containing the resist component, which allows accurate surface shape measurement. Further, since it is visible light, a laser device used for reference light is unnecessary, the number of parts can be reduced, and the device can be downsized.

In the above-mentioned embodiments, the case where the optical arrangement of the irradiation system and the light receiving system is the arrangement based on the shear-impul principle is described, but the present invention is not limited to this, and the imaging lens of the light receiving system is described. The optical axis angle may be arranged at an angle at which the bright line condensed on the surface of the object to be measured can be observed by the CCD camera.

Further, in the above-described embodiment, the case where one light receiving system is arranged for one irradiation system has been described, but the present invention is not limited to this, and two left and right objects are provided for one irradiation system. You may install two or more light receiving systems,
By doing so, the measurement accuracy of the surface profile can be further improved.

Further, in the above-mentioned embodiment, the output of the irradiation laser is 50 [μW / mm], but it is sufficient if the video signal representing the bright line portion is not saturated and the intensity center thereof can be detected. Further, in the above embodiment, the CCD
Although a camera having a size of ½ inch is used, the camera size is not limited to this, and in the above-mentioned embodiment, the case where the CCD camera is used as the light receiving element has been described. It may be a sensor or an optical position sensor.

Further, in the above-mentioned embodiments, the case where a green light laser having a wavelength of 532 [nm] is used as the irradiation light source has been described, but the present invention is not limited to this, and for example, a wavelength of 442 [n]
m] Cd: He (cadmium helium) gas laser,
Wavelength 477 (nm), 488 (nm), 497 (nm), 502 (n
m], 515 [nm] Ar (argon) or wavelength 521 [nm],
Ion laser such as Kr (krypton) of 531 [nm], semiconductor laser of wavelength band 475 to 560 [nm] or wavelength band of 4
An LED (light emitting diode) of 75 to 560 [nm] may be used as the irradiation light source.

In the above embodiment, the laser medium for emitting the SHG fundamental wave laser light is Nd: YAG.
Although the laser medium is used, the present invention is not limited to this, and Nd: YVO ₄ (neodymium ion, yttrium vanadate) or the like may be used, and a semiconductor is used as an excitation light source of the laser medium that emits a fundamental wave laser beam. A flash lamp or the like may be used instead of the laser device.

Further, in the above embodiment, the case where the surface shape on the semiconductor mounting substrate is measured has been described.
The present invention is not limited to this, and can be widely applied to the case of measuring the surface shape of an object to be measured having a 475 to 560 [nm] reflection band.

[0031]

As described above, according to the present invention, a wavelength band having a large reflectance intensity for the green component of visible light is used.
By using an irradiation light source of ~ 560 [nm], 475 ~ 56
A sufficient reflectance intensity on the object to be measured having a reflection band of 0 [nm] can be obtained, and the irradiation light can be visually observed. Therefore, accurate reflection light measurement can be easily performed without reference light.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a surface profile measuring apparatus according to the present invention.

FIG. 2 is a schematic diagram showing the principle of the shear impul.

FIG. 3 is a schematic diagram showing an image recognized by a CCD camera.

FIG. 4 is a signal waveform diagram showing a video signal obtained by a CCD camera.

FIG. 5 is a schematic diagram showing a conventional surface profile measuring apparatus.

FIG. 6 is a characteristic curve diagram showing reflectance spectral characteristics of a resist component.

[Explanation of symbols]

1, 20 ... Surface shape measuring device, 4 ... Irradiation light source laser device, 5, 25 ... Collimator lens, 6, 7, 26 ...
… Cylindrical lens, 8… Object plane, 9 ……
CCD camera, 10 ... Imaging lens, 27 ... Spherical lens.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyuki Ukai 9-15-22 Hongo-cho, Minokamo City, Gifu Prefecture Sony Minokamo Co., Ltd.

Claims (4)

[Claims] 1. An irradiation light source that emits light in a wavelength band of 475 to 560 [nm], a lens system that collects the light emitted from the irradiation light source as a bright line on the object to be measured, and the object to be measured. Light receiving means for receiving the reflected light of the bright line focused on the light receiving surface, and an imaging lens for forming an image of the reflected light of the bright line focused on the object to be measured on the light receiving surface of the light receiving means. A surface shape measuring device characterized by being obtained. 2. The irradiation light source includes a semiconductor laser device as an excitation light source, an Nd: YAG laser medium which emits a fundamental wave laser light by being excited by the semiconductor laser device, and an emission source from the Nd: YAG laser medium. The surface profile measuring apparatus according to claim 1, further comprising a non-linear optical element that wavelength-converts a fundamental wave laser beam into a second harmonic. 3. A first angle between the optical axis of the irradiation light irradiated on the object to be measured and the optical axis of the imaging lens, and the imaging lens orthogonal to the optical axis of the imaging lens. A second angle between the extension line of the center plane and the extension line of the light receiving surface of the light receiving means and the magnification of the imaging lens, and the tangent of the first angle is the tangent of the magnification and the tangent of the second angle. The surface shape measuring apparatus according to claim 1 or 2, wherein the imaging lens is arranged so as to be equal to a quotient. 4. As the object to be measured, the surface shape of a mounting board is measured, and a maximum of four times the maximum value of the resist component of the mounting board is measured by using light in the wavelength band of 475 to 560 [nm]. The surface shape measuring device according to claim 1, 2 or 3, wherein a reflectance intensity of 3 or more is obtained.