JPH0139041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the position and parallelism of a plate having a minute area, such as a semiconductor integrated circuit chip.

Semiconductor integrated circuits (IC, LSI, etc., hereinafter simply referred to as IC) are generally mounted by brazing a semiconductor chip onto a mounting base made of ceramic or the like.

In recent years, many ICs with multiple arrays of photo-sensing elements, such as image sensor ICs, have been manufactured, and it has become necessary to strictly control the parallelism when brazing semiconductor chips to mounting stands. .

For example, in the case of a solid-state imaging device using a CCD (charge-coupled device) element, the CCD chip is a plate with a microscopic area of about 5 x 5 mm, and the chips are separated by about 10 μ on the surface of the chip. In order to laminate the filter parallel to the chip, a measurement system for controlling the Z-axis direction is essential for the laminator to place the filter several tens of millimeters away in the reference stage before laminate.

Conventionally, when measuring the parallelism of a plate such as an IC chip, which has a small surface area and irregularities of several microns on its surface, and the distance from a reference point, two methods have been used: tilt measurement and distance measurement. There was no measurement method that could perform both at the same time.

Therefore, conventionally, there was no other way than to measure distance and inclination using separate devices and perform them sequentially. However, in the autocollimator conventionally used for measuring inclination, it is essential that the surface to be measured be able to reflect specularly, so if the surface has irregularities, the accuracy decreases.

In addition, distance measurement can be performed by irradiating a spot beam onto the surface to be measured, focusing the reflected light, and reading it with a position sensor, but if the parallelism of the surface to be measured is not maintained, accurate measurements may be required. I can't.

As described above, the conventional method of measuring distance and inclination separately has the drawback that not only the accuracy actually decreases, but also the measurement is time-consuming in practical terms.

The present invention has been made in view of the above points, and is capable of simultaneously measuring the distance from a reference surface and the normal slope of a plate with a small area, and without contacting the surface to be measured, with high accuracy. The purpose is to provide an angle measuring device.

An embodiment of the present invention will be described below.

The light source S is, for example, a light emitting diode, a laser diode, a gas laser, or the like that can generate a highly focused beam.

For example, one of the reflective surfaces R ₁ and R ₂ is a surface to be measured such as an IC chip, and the other is an imaginary reference surface.

The beam from the light source S has a spot diameter of, for example, several tens to several hundred μmφ on the reflecting surfaces R ₂ and R ₁ .

The lens L is a convex lens placed at a distance a from the reflective surface _R1 , which is a virtual reference surface, with its optical axis aligned with the reflected beam, but a composite optical system with two or more lenses can also be used. .

In the focal plane of this lens L, that is, the lens L
At the focal length f position, there is an area image sensor formed by regularly arranging a plurality of photoelectric conversion elements vertically and horizontally, or a two-dimensional position sensor 1 equivalent thereto.
It is arranged so that its center coincides with the optical axis of the lens L.

A beam splitter 2 for splitting is provided between the lens L and the two-dimensional position sensor 1 at a distance b ₁ from the lens L, and a reference reflecting surface is provided on the split optical axis.
A one-dimensional position sensor 3 is arranged on the surface where R ₁ forms an image (a position satisfying 1/f=1/a+1/b ₁ +b ₂ at a distance of b ₂ from the splitter 2).

This one-dimensional position sensor 3 is a linear image sensor in which a plurality of photoelectric conversion elements are arranged linearly or something equivalent thereto, and both sensors 1 and 3 are
The position irradiated with the spot light can be detected according to the position of the sensing element.

In the apparatus of the present invention configured in this way, the one-dimensional position sensor 3 measures the distance between the reflective surfaces R ₁ and R ₂ , and the two-dimensional position sensor 1 simultaneously measures the distance between the reflective surfaces R _{1 , R 2} , and Parallelism between R ₂ can be measured.

In other words, in position measurement, the reflective surface that forms the reference surface
The spot image of R ₁ is focused by the lens L, and is imaged at the P ₂ position of the one-dimensional position sensor 3 as reflected light from the splitting beam splitter 2 .

On the other hand, when a spot image is formed on the surface to be measured R ₂ , it similarly passes through the lens L and the beam splitter 2 and is focused on the one-dimensional position sensor 3 at the P ₂ ' position.

Therefore, first, measure the light from the reference surface R ₁ to determine the P ₂ position of the one-dimensional position sensor 3, and then hold the surface to be measured R ₂ near the reference surface R ₁ . When the light is applied to the one-dimensional position sensor 3,
It can be tied to the P ₂ ′ position.

By using this relationship, the distance between the surface to be measured and the reflective surface _R2 can be calculated using the reflective surface _R1 as a reference.

That is, the distance between R ₁ and R ₂ is d, the distance between P ₂ and P ₂ ' is X ₂ , the angle of incidence of the light source on the reference reflector R ₁ is α,
For convenience of explanation, the relational expression will be derived based on FIG. 2, which shows the R ₁ and R ₂ parts enlarged.

Here, if the magnification of this optical system is m (=b ₁ + b ₂ /a), then r ₁ t=X ₂ /m=d/sinαcos(180°−90°−2α) +d/sinαsin(180° −90°−2α) tan2θ = 2αcosα+dcos2α/sinαtan2θ = d(2cosα+cos2α/sinαtan2θ) Therefore, d=X ₂ /m(2cosα+cos2α/sinαtan2θ) Here, m and α are the given values, and the measurement method described later By determining θ and measuring the distance of X ₂ with the one-dimensional sensor 3, it is possible to determine d, that is, the distance from the reference position to the position where the object to be measured is placed.

Next, the slope θ measurement will be explained.

The light rays (approximately parallel rays) emitted by the light source S pass through the reflective surfaces R ₁ and R ₂ and are focused on the two-dimensional position sensor 1 placed at the focal point of the lens L (that is, at a distance f from the lens L). tie.

The image point formed by the ray that passed through the reference reflective surface R ₁ is
If the origin of the two-dimensional position sensor 1 surface is P ₁ , the image forming point from the reflective surface R ₂ which is the surface to be measured is the reflective surface R ₁ ,
When R ₂ is parallel, P ₁ matches, and when reflective surface R ₂ is tilted, the input point shifts vertically and horizontally on the two-dimensional position sensor 1 depending on the tilt angle and direction. occurs at P ₁ ′. The position of this P ₁ ′ is the reflection surface
If R ₂ is tilted by θ as shown in FIGS. 1 and 2, the inclination of the ray of light incident on the lens L will be 2θ, and P ₁ P ₁ ′=X ₁ =f tan2θ. Therefore, θ
= 1/2 tan ^-1 X ₁ /f, θ can be determined by measuring X ₁ .

Therefore, first, light is applied to the reference reflective surface R ₁ to determine the position P ₁ of the two-dimensional sensor 1, and then light is applied to the object to be measured R ₂ to detect the position P ₁ ′.

In this way, the splitting beam splitter 2 is placed behind the lens L, and the one-dimensional position sensor 3 and the two
With the dimensional position sensor 1, it is possible to simultaneously measure the distance and inclination with respect to the reference plane.

In the above embodiment, the reflected beam is condensed by the optical system consisting of the lens L and the beam splitter 2 for splitting, and split beams in two directions are obtained. By shortening the focal length of the lens system, the device size can be made compact.

Furthermore, as the beam detection means, both the one-dimensional position sensor 3 and the two-dimensional position sensor 1 can be constructed of an image sensor or the like in addition to a continuous output analog sensor.

Furthermore, the sensors 1 and 3 are not necessarily limited to two-dimensional and one-dimensional sensors, respectively. In other words, a two-dimensional sensor is used for sensor 3, and sensor 1 is
A one-dimensional reflective surface may be used as long as the reflective surface _R2 to be measured is tilted in only one direction, as explained using the drawing.
(Typically, a two-dimensional sensor is required since it is tilted in two directions).

Furthermore, as another embodiment, as shown in FIG. 3, the reflecting surfaces R ₁ and R ₂ are brought downward, and the reflection is made once by the reflecting mirror M, and then passed through the lens L, and the rest is as described above. In the same way, distance and slope can also be measured at the same time.

However, in this case, the distance a is the reference reflective surface
The distance from _R1 to the reflecting mirror M and the distance from this mirror M to the lens L are made to be the same.

As described above, according to the present invention, the parallelism between the reference reflecting surface R ₁ and the surface to be measured R ₂ and the distance therebetween can be measured simultaneously and with high precision.

Therefore, when an IC chip having a reflective surface of a minute area as a surface to be measured is brazed to a mounting table made of ceramic or the like, sufficiently high accuracy can be obtained by using the apparatus of the present invention. Moreover,
Measurement can be performed without contacting the surface to be measured, and the device itself can be configured extremely compactly.

In the semiconductor manufacturing process, the object to be measured often has a small area, and there are large dimensional restrictions due to other inspection equipment, alignment microscopes, transport mechanisms, fixing mechanisms, etc. Therefore, control and measurement using the device of the present invention is difficult. has extremely large merits.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is a schematic enlarged view of reflective surfaces R ₁ and R ₂ , and FIG. 3 is a diagram showing another embodiment of the present invention. It is a configuration explanatory diagram. S ₁ , S ₂ ... light source, R ₁ , R ₂ ... reflective surface, M ...
Half mirror, L...Lens, 1...Two-dimensional position sensor, 2...Beam splitter for division, 3...
One-dimensional position sensor.

Claims (1)

[Claims] 1. A light source that irradiates a beam onto the reference surface and the surface to be measured, a lens that focuses the beam reflected from the surface to be measured, and an optical system that obtains split beams in two directions.
The reference surface is located at the position where the image is formed on one of the optical axes of the split beam, and by detecting the deviation in the image formation position between the reflected beam of the measured surface and the reflected beam of the reference surface, the reference surface and the measured object are A first beam detection means for measuring the distance between the surfaces; and a second beam detection means for detecting the inclination angle formed between the surface to be measured and the reference surface at the focal position of the other optical axis of the split beam. A distance and inclination angle measuring device comprising: