JPH06331328A - Height measuring device and method - Google Patents

Abstract

PURPOSE:To accurately and rapidly inspect the shape or amt. of the solder sphere bonded to an electrode by controlling the intensity of measuring light irradiating a measuring point on the basis of the output signal of a light intensity detector corresponding to the reflectivity at the measuring point of an object to be measured. CONSTITUTION:The reflectivity detection light 51 and height measuring light 52 incident on the same point of a rotary polyhedral mirror 31 through the same mirror 23 scans the same scanning line of an object to be measured at a definite interval through a scanning lens 32 and a mirror 33 accompanying the rotation of the rotary polyhedral mirror 31. The detection light 51 regularly reflected from the surface of the object to be measured is always incident on a light intensity detector 6 preceding to the height detection light 52 and the intensity of the detection light 51 incident on the light intensity detector 6 excellent in sensitivity and response speed, for example, a photomultiplier tube is measured. The height detection light 52 regularly reflected from the surface of the object 1 to be measured through which the detection light 51 passes is incident on a position detection element 41 and the height of the unevenness on the surface of the object l to be measured is measured on the incident position of the measuring light 52 to the position detection element 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for optically inspecting the surface shape of an electrode formed on a chip in the manufacture of an LSI, and in particular, an error does not intervene in a measured value due to a difference in reflectance at a measuring point. A height measuring device configured as described above.

In recent years, as one of the methods for mounting LSIs on a printed wiring board at a high density, an LSI in which fine solder balls are attached on electrodes is joined to a conductor pattern formed on the printed wiring board. A mounting method called flip chip bonding is used.

In order to reliably bond the LSI to the printed wiring board by such a method, it is necessary to strictly control the shape and amount of the solder balls on the electrodes. Therefore, it is desired to realize a height measuring device capable of accurately and quickly inspecting the shape and amount of the solder balls attached to the electrodes.

[0004]

2. Description of the Related Art FIG. 6 is a perspective view showing a part of an electrode forming surface of an LSI, FIG. 7 is a perspective view showing a configuration of a conventional height measuring device, and FIG. 8 is a perspective view showing an operating principle of a position detecting element. Is.

An LSI (hereinafter referred to as an object to be measured) 1 to be inspected has a plurality of electrodes on an electrode forming surface as shown in FIG.
11 are formed, and a plurality of solder balls 12 having substantially the same grain size are adhered to the respective electrodes 11 prior to mounting on the printed wiring board.

In order to surely bond the measured object 1 to a printed wiring board (not shown) by the flip chip bonding method, the solder balls 12 attached to the respective electrodes 11 formed on the same measured object 1 are used. And the particle size should be approximately equal.

In the LSI manufacturing process, therefore, the object to be measured 1 having the solder balls 12 attached to the electrodes 11 on the chip is placed on the apparatus shown in FIG. 7 and the height of the unevenness on the surface is optically measured. The solder spheres 12 adhered to the electrodes 11 are inspected for grain size or lack thereof.

As shown in FIG. 7, the conventional height measuring device comprises a measuring light source 2 for outputting a laser beam, an optical scanning mechanism 3 and a height measuring mechanism 4, and the measuring light source 2 emits a laser light source 21 and a laser beam. It has a sharpening beam expander 22 and a mirror 23 that bends in a predetermined direction.

The optical scanning mechanism 3 for scanning the incident laser light within a predetermined range is a rotary polygon mirror 31 and a scan lens 32.
The laser light incident on the optical scanning mechanism 3 from the measurement light source 2 scans the scanning line 13 of the measured object 1 as the rotary polygon mirror 31 rotates.

On the other hand, the height measuring mechanism 4 uses PSD (position
Position detection element 41 called "sensitive diode" and imaging lens
The laser light specularly reflected on the surface of the object to be measured 1 is imaged on the incident surface of the position detecting element 41 via the imaging lens 42.

As shown in FIG. 8, a position detecting element 41 for measuring the height of unevenness has a shallow rectangular p-type diffusion layer 44 formed on one surface of an n-type Si substrate 43, and a rectangular p-type diffusion layer 44. On the upper side, four electrodes 45 are formed along each side so that their ends do not contact each other.

A large reverse bias is applied to the pn junction through the electrode 46 on the bottom so that the pn junction is not biased in the forward direction even if the amount of light increases, and a thin laser beam is incident on the light spot position indicated by the arrow on the incident surface. Then, a photocurrent is generated at the light spot position, and the photocurrent is shunted to the electrodes 45 on the four sides.

Divided photocurrents I _x1 , I _x2 , I _y1 , I _y2
Is dependent on the sheet resistance of the diffusion layer from the light spot position to each electrode 45, and the ratio of the respective currents I _x1 / I _x2 , I _y1 /
It is possible to calculate the coordinates x and y of the position of the light spot where the laser light is incident from I _y2 .

The incident position of the laser beam specularly reflected on the surface of the object to be measured 1 on the position detecting element 41 changes depending on the height of the irregularities on the surface, and the coordinates x, y of the light point position at that time are calculated. Thus, the height of the unevenness on the surface of the measured object 1 can be measured.

[0015]

If the surface of the object to be measured that reflects the laser light is a flat surface having the same reflectivity, the height of the unevenness can be measured by the position detecting element, but the light reflected by the solder ball can be used. Even if they have the same height, the amount of light incident on the position detection element fluctuates greatly due to the inclination of the reflecting surface.

However, the commercially available position detecting element has an extremely narrow allowable range of the amount of light capable of accurately detecting the position of the light spot from the current ratio, and is incident even if the intensity of the laser beam or the sensitivity of the position detecting element is adjusted. There was a problem that the amount of light could not be set within the allowable range.

An object of the present invention is to provide a height measuring device capable of accurately and quickly inspecting the shape and amount of solder balls attached to electrodes.

[0018]

FIG. 1 is a perspective view showing the principle of a height measuring device according to the present invention. Note that the same object is denoted by the same symbol throughout the drawings.

The above-mentioned problem is that the surface of the object to be measured having irregularities is scanned with laser light, the specularly reflected light from the object to be measured is made incident on the position detecting element, and the output signal of the position detecting element indicating the incident position of the specularly reflected light In a measuring device for measuring the height of unevenness of an object to be measured, a laser light source 5 for outputting a reflectance detection light 51 for detecting the reflectance of the surface and a height measuring light 52 for measuring the height of the unevenness, and a reflectance Detection light 51 and height measurement light
An optical scanning mechanism 3 configured to scan the same scanning line 13 at a constant interval 52, and detects the intensity of the reflectance detection light 51 specularly reflected on the surface of the measured object 1 prior to height measurement. The light intensity detector 6 and the position detecting element 41 for measuring the height of the unevenness of the object to be measured 1 from the incident position of the height measuring light 52 specularly reflected on the surface are measured points of the object to be measured 1 The intensity of the height measuring light 52 irradiating the measurement point after a certain time is controlled by the light intensity control unit 7 based on the output signal of the light intensity detector 6 corresponding to the reflectance of the height of the present invention. Is achieved by a measuring device.

[0020]

In FIG. 1, a height measuring device according to the present invention is a laser light source that outputs reflectance detection light and height measurement light, and the reflectance detection light and height measurement light scan the same scanning line at regular intervals. An optical scanning mechanism configured to operate, a light intensity detector that detects the intensity of the reflectance detection light specularly reflected on the surface of the measured object prior to height measurement, and the measured position from the incident position of the height measurement light. And a position detecting element for measuring the height of the unevenness of the object.

The light intensity control unit controls the intensity of the height measuring light irradiating the measurement point after a predetermined time based on the output signal of the light intensity detector corresponding to the reflectance at the measurement point of the object to be measured. By doing so, it is possible to keep the amount of height measurement light incident on the position detection element within the allowable range according to the reflectance, and accurately and quickly inspect the shape and amount of solder balls attached to the electrodes. It is possible to realize a height measuring device that can be used.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 2 is a perspective view showing an embodiment of the height measuring device according to the present invention, FIG. 3 is a time chart showing the intensity of height measuring light according to the embodiment, and FIG. 4 is a view showing the height measuring device according to the present invention. FIG. 5 is a perspective view showing another embodiment, and FIG. 5 is a time chart showing the intensity of the height measuring light of another embodiment.

One embodiment of the present invention has a laser light source 5 consisting of two linearly polarized light sources 53 having a beam expander 22 as shown in FIG. 2, and a reflectance detection light consisting of linearly polarized laser light. The polarization directions of 51 and the height measurement light 52 are orthogonal to each other.

The reflectance detecting light 51 and the height measuring light 52 which are incident on the same point of the rotary polygon mirror 31 constituting the optical scanning mechanism 3 via the same mirror 23 are scanned by the scan lens 32 as the rotary polygon mirror 31 rotates. And the same scanning line 13 of the object to be measured 1 is scanned at regular intervals via the mirror 33.

The reflectance detection light 51, which is specularly reflected on the surface of the object to be measured 1 prior to the height measurement light 52, is incident on the light intensity detector 6, and the sensitivity and response of, for example, a photomultiplier tube. The intensity of the reflectance detection light 51 incident on the light intensity detector 6 having an excellent speed is measured.

The height measuring light 52 specularly reflected on the surface of the object to be measured 1 through which the reflectance detecting light 51 has passed is incident on the position detecting element 41, and the position detecting element composed of the PSD of the height measuring light 52. The height of the unevenness on the surface of the measured object 1 is measured by the incident position on the object 41.

The reflectance detection light 51 entering the light intensity detector 6 and the height measuring light 52 entering the position detecting element 41 are reflected by the object to be measured 1 and are rotated to constitute the optical scanning mechanism 3 as described above. As the polygon mirror 31 rotates, it scans the same scan line 13 of the object 1 to be measured at regular intervals.

Therefore, as a means for branching the reflectance detection light 51 and the height measurement light 52 specularly reflected on the surface of the object to be measured 1 into different paths, a polarized beam for splitting linearly polarized laser light whose polarization directions are orthogonal to each other is used. The splitter 61 is arranged after the imaging lens 42.

As described above, the commercially available position detecting element has an extremely narrow allowable range of the amount of light capable of accurately detecting the position of the light spot from the current ratio, and when the reflectance fluctuates, the intensity of the laser beam and the sensitivity of the position detecting element are reduced. Even if it is adjusted, the amount of incident light cannot be kept within the allowable range.

However, by scanning the same scanning line 13 of the object to be measured 1 with the reflectance detecting light 51 prior to the scanning of the height measuring light 52, the measurement of the intensity of the height measuring light 52 irradiating the measuring point is performed. The ratio of the intensities of the height measuring light 52 specularly reflected at the points can be detected.

For example, when the intensity detected by the light intensity detector 6 is lowered when the reflectance detection light 51 irradiates an arbitrary measuring point, the position detecting element 41 is specularly reflected at the same measuring point after a certain period of time. The light amount of the height measuring light 52 incident on is also reduced at substantially the same rate.

Therefore, one embodiment of the present invention is a linearly polarized light source 53.
While the intensity of the reflectance detection light 51 output from the device is kept constant, the intensity of the height measurement light output after a fixed time based on the intensity of the reflectance detection light detected by the light intensity detector as shown in FIG. Are in control.

That is, the product of the intensity of the reflectance detection light 51 detected by the light intensity detector and the intensity of the height measurement light 52 irradiating the same measurement point after a fixed time is always constant. The linearly polarized light source 53 that outputs the light is controlled to stabilize the amount of light incident on the position detection element 41.

Further, in another embodiment of the present invention, as shown in FIG. 4, the laser light source 5 has one circularly polarized light source 54 having the beam expander 22, and the circularly polarized light source 54 outputs the circularly polarized light. The laser light is split into two by a spectroscopic means 55 including a half mirror 57 and a mirror 58.

The circularly polarized laser light split by the spectroscopic means 55 consists of laser light linearly polarized by passing through the quarter-wave plate 56, and the reflectance detection light 51 and the height measurement are orthogonal to each other in the polarization direction. The light 52 is converted into light 52 and is incident on the rotary polygon mirror 31 which constitutes the light scanning mechanism 3.

The reflectance detecting light 51 and the height measuring light 52 incident on the same point of the rotary polygon mirror 31 constituting the optical scanning mechanism 3 are scanned by the scan lens 32 with the rotation of the rotary polygon mirror 31, as in the above embodiment. And the same scanning line 13 of the object to be measured 1 is scanned at regular intervals via the mirror 33.

Also in this embodiment, as in the case of the above-described embodiment, a certain time has elapsed since the intensity of the reflectance detection light was detected based on the intensity of the reflectance detection light detected by the light intensity detector as shown in FIG. The intensity of the height measuring light 52 output from the circularly polarized light source 54 later is controlled.

That is, a circularly polarized laser light is used so that the product of the intensity of the reflectance detection light 51 detected by the light intensity detector and the intensity of the height measurement light 52 irradiating the same measurement point after a predetermined time is always constant. The output circularly polarized light source 54 is controlled to stabilize the amount of light incident on the position detection element 41.

As described above, the height measuring device according to the present invention includes a laser light source for outputting reflectance detection light and height measurement light,
An optical scanning mechanism configured so that the reflectance detection light and the height measurement light scan the same scanning line at regular intervals, and the intensity of the reflectance detection light specularly reflected on the surface of the object to be measured prior to height measurement. And a position detecting element for measuring the height of the unevenness of the object to be measured from the incident position of the height measuring light.

The light intensity control unit controls the intensity of the height measuring light irradiating the measurement point after a certain time based on the output signal of the light intensity detector corresponding to the reflectance at the measurement point of the object to be measured. By doing so, it is possible to keep the amount of height measurement light incident on the position detection element within the allowable range according to the reflectance, and accurately and quickly inspect the shape and amount of solder balls attached to the electrodes. It is possible to realize a height measuring device that can be used.

[0041]

As described above, according to the present invention, it is possible to provide a height measuring device capable of accurately and quickly inspecting the shape and amount of solder balls attached to electrodes.

[Brief description of drawings]

FIG. 1 is a perspective view showing the principle of a height measuring device according to the present invention.

FIG. 2 is a perspective view showing an embodiment of a height measuring device according to the present invention.

FIG. 3 is a time chart showing the intensity of height measurement light according to an example.

FIG. 4 is a perspective view showing another embodiment of the height measuring device according to the present invention.

FIG. 5 is a time chart showing the intensity of height measurement light according to another embodiment.

FIG. 6 is a perspective view showing a part of an electrode formation surface of an LSI.

FIG. 7 is a perspective view showing a configuration of a conventional height measuring device.

FIG. 8 is a perspective view showing the operating principle of the position detection element.

[Explanation of symbols]

1 Object to be Measured 3 Optical Scanning Mechanism 5 Laser Light Source 6 Optical Intensity Detector 7 Optical Intensity Control Section 13 Scanning Line 22 Beam Expander 23 Mirror 31 Rotating Polyhedral Mirror 32 Scan Lens 33 Mirror 41 Position Detector 42 Imaging Lens 51 Reflectance Detection light 52 Height measurement light 53 Linearly polarized light source 54 Circularly polarized light source 55 Spectroscopic means 56 1/4 wavelength plate 57 Half mirror 58 Mirror 61 Polarization beam splitter

Claims (5)

[Claims] 1. An output of the position detecting element indicating the incident position of the specularly reflected light by scanning the surface of the object to be measured having irregularities with a laser beam to cause the specularly reflected light from the object to be measured to enter the position detecting element. A laser light source that outputs a reflectance detection light (51) for detecting the reflectance of the surface and a height measurement light (52) for measuring the height of the unevenness in a measuring device for measuring the height of the unevenness by a signal
(5), an optical scanning mechanism (3) configured to scan the reflectance detection light (51) and the height measurement light (52) on the same scanning line (13) at regular intervals, Light intensity detector (6) for detecting the intensity of the reflectance detection light (51) specularly reflected on the surface of the object to be measured (1) prior to measurement
And a position detecting element for measuring the height of the unevenness of the object to be measured (1) from the incident position of the height measuring light (52) specularly reflected on the surface.
(41) and a light intensity control unit (7) based on the output signal of the light intensity detector (6) corresponding to the reflectance at the measurement point of the object to be measured (1)
The height measuring device is configured so as to control the intensity of the height measuring light (52) for irradiating the measuring point after a predetermined time. 2. The output of the position detecting element, which indicates the incident position of the specular reflected light, by scanning the surface of the object to be measured having irregularities with a laser beam to cause the specularly reflected light from the object to be measured to enter the position detecting element. A laser light source that outputs a reflectance detection light (51) for detecting the reflectance of the surface and a height measurement light (52) for measuring the height of the unevenness in a measuring device for measuring the height of the unevenness by a signal
(5), an optical scanning mechanism (3) configured to scan the reflectance detection light (51) and the height measurement light (52) on the same scanning line (13) at regular intervals, Light intensity detector (6) for detecting the intensity of the reflectance detection light (51) specularly reflected on the surface of the object to be measured (1) prior to measurement
And a position detecting element for measuring the height of the unevenness of the object to be measured (1) from the incident position of the height measuring light (52) specularly reflected on the surface.
(41) and a light intensity control unit (7) based on the output signal of the light intensity detector (6) corresponding to the reflectance at the measurement point of the object to be measured (1)
However, the height measuring method is characterized in that the intensity of the height measuring light (52) reflected at the measuring point and input to the position detecting element (41) is controlled. 3. The reflectance detection light (51) comprising two linearly polarized light sources (53) for outputting a reflectance detection light (51) made of linearly polarized laser light and a height measurement light (52). And a laser light source arranged such that the polarization directions of the height measuring light (52) are orthogonal to each other.
(5), the intensity detected by the light intensity detector (6) when the reflectance detection light (51) irradiates an arbitrary measurement point, and the height at which the measurement point is irradiated after a certain time. The light intensity control unit (7) is configured to control the linearly polarized light source (53) that outputs the height measurement light (52) so that the product of the intensities of the measurement light (52) becomes constant. 1. The height measuring device according to 1. 4. A reflectance detection light (51) and a height measurement light (52) for scanning the same scanning line (13) of the object to be measured (1) at regular intervals.
The height measuring device according to claim 1, further comprising a polarization beam splitter (61) as a means for splitting the specularly reflected light of (1) into different paths. 5. A circularly polarized light source (54) for outputting circularly polarized laser light, a spectroscopic means (55) and a quarter wavelength plate (56) are provided,
The reflectance detection light (51) and the height measurement light (52) formed by dividing the circularly polarized laser light by the spectroscopic means (55) are orthogonal to each other in polarization direction by the quarter wavelength plate (56). Which has a laser light source (5) for converting it into a linearly polarized laser light, which is detected by the light intensity detector (6) when the reflectance detection light (51) irradiates an arbitrary measuring point, and The light intensity control unit (7) controls the circularly polarized light source (54) that outputs the circularly polarized laser light so that the product of the intensities of the height measuring light (52) that illuminates the measurement point later becomes constant. The height measuring device according to claim 1, which is configured to: