JPH11173821A - Optical inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a fast height measurement at arbitrary location of an object to be measured realizable while maintaining highly accurate measurement accuracy by a confocal method by providing a 2-dimensional movable mirror to polarize a light beam, etc. SOLUTION: An object to be measured is irradiated with a light beam from a light source 17 via an object lens 11, and the reflected light is condensed concentrically with the light beam. The condensed reflected light is separated from the light passage of the light beam via a beam splitter 15 and is received at a light receiving device 21. A focus adjusting means 13 changes the substantial length of the light passage of the light beam and the reflected light via the object lens 11 with respect to the object to be measured. A 2-dimensional movable mirror 12 polarizes the light beam in a predetermined direction to displace the irradiation location of the light beam via the object lens 11 and condenses the reflected light from the irradiation location to guide it to the light receiving device 21. As the irradiation location and the detection location of the light beam are optically displaced by this, it is possible to measure the height of the object to be measured at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical inspection apparatus used for inspecting the appearance and shape of a semiconductor chip and the like, and inspecting the state of component mounting on a printed circuit board.

[0002]

[Related Background Art] One of the techniques for optically inspecting the appearance and shape of a semiconductor chip or the like is a confocal method using the longitudinal magnification of a lens. In the confocal method, basically, the focal position of an optical system (lens) for viewing the object to be measured is changed, and the height of the object to be measured is obtained from information on the focal point.

More specifically, as shown in FIG. 3, light output from a light source 1 is applied to an object 3 to be measured via an objective lens 2, and the reflected light is condensed via the objective lens 2.
And this reflected light is half mirror (beam splitter)
The light is guided to a light receiver 5 via the light source 4 and the amount of received light is measured.
At this time, as shown in FIGS.
Is displaced in the optical axis direction to change its focal position. Then, as shown in FIG. 4, the amount of light received by the light receiver 5 changes with the change of the focal position with respect to the measurement target 3, and when the measurement target 3 is focused, the amount of received light is maximized. Then, the height of the measurement object 3 is measured.

[0004]

However, the shape measurement by the confocal method described above has advantages such as higher measurement accuracy as compared with a conventional general triangulation method using the lateral magnification of a lens. On the other hand, for example, since the objective lens needs to be displaced in the optical axis direction, there is a problem that the time required for measurement is long (measuring speed is slow). In particular, when the height measurement is performed while changing the measurement position over a certain wide area, such as when inspecting the appearance and shape of a semiconductor chip or the like or inspecting the component mounting state on a printed circuit board,
There is a problem that the measurement speed is further reduced in conjunction with the position control. In addition, if a mechanical two-axis scanning stage is used to control the measurement position, the entire configuration of the apparatus is unavoidably large and expensive.

The present invention has been made in view of such circumstances, and an object of the present invention is to measure height at an arbitrary position on an object to be measured while maintaining highly accurate measurement accuracy by a confocal method. An object of the present invention is to provide a simple and highly practical optical inspection device that can be realized at high speed.

[0006]

In order to achieve the above object, an optical inspection apparatus according to the present invention irradiates a light beam output from a light source to the object to be measured, and reflects a light beam reflected by the object to be inspected. An objective lens that condenses the light beam coaxially with the light beam, a light receiver that separates and receives reflected light condensed through the objective lens from an optical path of the light beam through a beam splitter, and the objective lens Focus adjusting means for changing a substantial optical path length of the light beam and the reflected light with respect to the inspection object through the objective lens, and further irradiates the light beam in a predetermined direction to irradiate the light beam through the objective lens. And a two-dimensional movable mirror that condenses reflected light from the irradiation position via the objective lens and guides the reflected light to the light receiver.

That is, by deflecting the light beam and the reflected light in a predetermined direction in the optical path of the light beam and the reflected light connecting the beam splitter and the objective lens, the transmission position of the light beam and the reflected light in the objective lens is obtained. To change
With this, the irradiation position of the light beam on the measurement object,
And the detection position of the reflected light is optically displaced.

According to a preferred aspect of the present invention, claim 2 is provided.
An optical path between the light source and the focus adjusting means and an optical path between the light receiver and the focus adjusting means are provided as a collimator optical system, and the focus adjustment is performed as described in claim 3. The means is realized as an actuator for moving and displacing a condenser lens provided in front of the two-dimensional movable mirror in the optical axis direction.

That is, by providing the focus adjusting means in front of the two-dimensional movable mirror, the size of the condenser lens in the two-dimensional movable mirror and the focus adjusting means can be reduced, and the light beam and reflected light passing through the two-dimensional movable mirror can be reduced. By squeezing
It is characterized in that the size is reduced and the driving speed is increased, and the measuring speed is improved as a whole.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG.
1 shows a schematic configuration of an optical inspection apparatus according to this embodiment, and 11 denotes an objective lens arranged to face a measurement object. As the objective lens 11, a lens having a large diameter corresponding to a scanning range of a light beam which is optically deflected and scanned as described later is used, and is fixedly incorporated in a housing of the inspection apparatus. Thus, above the objective lens 11, passing through the optical center of the objective lens 11 and 45 °
A two-dimensional galvanomirror (two-dimensional reflecting mirror) 12 whose posture is controlled at a reference position having an inclination of. The galvanometer mirror 12 is two-dimensionally tilt-controlled with its optical center as a fulcrum by a two-dimensional attitude control mechanism (not shown).

On the other hand, on the side of the galvanometer mirror 12, a condenser lens 13a as a focus adjusting means 13 is disposed. The condenser lens 13a is supported by an actuator 13b composed of, for example, a linear motor or a piezoelectric vibrator, and is provided to be movable and displaceable in the optical axis direction. That is, the actuator 13b is connected to the condenser lens 1
By displacing 3a in the direction of the optical axis, the distance between the objective lens 11 and the condenser lens 13a via the galvanometer mirror 12 is changed. Further, it has a role of adjusting a focal position for receiving the reflected light and changing its substantial optical path length. By adjusting the focal position of the condenser lens 13a, the focus adjustment of the objective lens 2 with respect to the measurement target shown in FIG. 3 is equivalently realized.

A quarter-wave plate 1 is positioned beside the condenser lens 13a with its optical center aligned so as to view the objective lens 11 via the galvanometer mirror 12.
4 and a beam splitter 15 are arranged. Specifically, when the position of the galvanomirror 12 is controlled to a reference position having an inclination of 45 °, the objective lens 11
And the optical center axis of the optical system formed by the 波長 wavelength plate 14 and the beam splitter 15 intersects at right angles at the optical center position of the galvanometer mirror 12, The quarter-wave plate 14 and the beam splitter 15 are provided.

On the extension of the optical center axis of the optical system formed by the quarter-wave plate 14 and the beam splitter 15, a light beam for irradiating the object to be measured through the objective lens 11 is generated. An optical system 16 is provided.
The light projecting system 16 includes a light source 17 that outputs a coherent light beam such as a semiconductor laser, a collimator lens 18 that converges the light beam output from the light source 17 into a spot light composed of a parallel light beam, An astigmatism correction lens 19 for compensating astigmatism caused by the objective lens 11 is provided. Such a floodlight system 1
The light beam (spot light) output from 6 is guided from the beam splitter 15 to the galvano mirror 12 via the quarter-wave plate 14 and the condensing lens 13a, and is reflected by the galvanomirror 12. The object to be measured is irradiated via the objective lens 11. The optical path between the collimator lens 18 and the condenser lens 13a is constructed as a collimator optical system, and the light beam is guided as a parallel light beam.

A light receiving system 20 is provided on the output end side of the reflected light from which the optical path from the objective lens 11 is branched by the beam splitter 15. The light receiving system 20 includes a light receiving device 21 such as a phototransistor, and an imaging lens 2 that forms an image of the reflected light branched by the beam splitter 15 on the light receiving surface via an aperture (aperture) 22.
3 is provided. The optical path between the imaging lens 23 and the condenser lens 13a is also constructed as a collimator optical system.

The height of the object to be measured is measured, for example, by monitoring the amount of reflected light received by the light receiver 21 and monitoring the optical conditions when the amount of received light is maximized, specifically, by the actuator 13b. This is achieved by determining the position of the condenser lens 13a that is driven to be displaced. The position information of the condenser lens 13a is, for example, the actuator 1
The output is obtained by detecting the output of a differential transformer (not shown) for driving the actuator 3b, or as the output of an encoder for monitoring the amount of movement of the actuator 13b.

The angle of the galvanomirror 12 is adjusted as shown in FIG. 1. The optical axis between the condenser lens 13a and the objective lens 11, particularly the galvanomirror 12 and the objective The optical axis between the objective lens 11 and the lens 11 is displaced (deflected) from the optical center axis of the objective lens 11. Thus, the light beam (reflected light) deflected from the optical center axis of the objective lens 11 passes through a position displaced from the optical center of the objective lens 11 according to the direction of the deflection, and is perpendicular to the object to be measured. It is illuminated and its reflected light is collected along the reverse path. That is, the objective lens 1 is deflected by the deflection of the optical axis of the light beam (reflected light) by the galvanometer mirror 12.
The irradiation position of the light beam irradiating the object to be measured via 1;
And the detection position of the reflected light is displaced.

According to the optical inspection apparatus thus configured, the focal point (light receiving optical path length) of the reflected light of the light beam irradiated on the object to be measured with respect to the light receiver 21 is displaced to increase the height of the object to be measured. When measuring the height with high precision, the light beam guided to the objective lens 11 and its reflected light are optically deflected by using the galvanometer mirror 12, thereby displacing the measurement position two-dimensionally. Scanning is possible. Moreover, as long as the light beam can be irradiated through the objective lens 11, an arbitrary position on the measurement object can be quickly irradiated with the light beam and its reflected light can be detected. Need not be incorporated into a mechanical two-axis scanning stage to adjust the measurement site. Therefore, it is possible to perform three-dimensional shape measurement of the measurement object with high accuracy in a relatively short time (high speed).

With the above-described configuration, it is not necessary to displace the large-diameter objective lens 11 and it is only necessary to displace the minute condenser lens 13a in the focus adjusting means 13 in the optical axis direction. The energy required for the movement of the condenser lens 13a during the operation can be small, and the actuator 13b itself can be simply configured. Further, since the diameter of the light beam irradiating the galvanomirror 12 can be reduced, the galvanomirror 12
Can be reduced, and the driving force required for the inclination adjustment can also be reduced. Therefore, the galvanomirror 12 can be driven at a high speed, and the control of the irradiation position of the light beam can be speeded up. Therefore, while maintaining the measurement accuracy at a high level, it is possible to obtain an effect that the measurement site can be changed at a high speed.

The present invention is not limited to the above embodiment. For example, it is possible to sequentially measure the height at each part while continuously scanning the light beam within the effective range of the objective lens 11, but only the measurement part specified in advance is spot-likely measured. It is also possible. In this case, for example, as shown in FIG. 2, the TV camera 30 is mounted on the housing provided with the optical inspection device having the above-described configuration.
And the angle of the galvanomirror 12 may be adjusted so that the measurement site is specified from the information of the measurement object captured and input as an image in advance, and the light beam is emitted only to the specific site. . At this time, the housing is assembled on a uniaxial scanning stage 31 so that the field of view of the object to be measured by the TV camera 30 and the objective lens 1
The drive control of the galvanomirror 12 may be performed after the casing is moved so that the visual field position of the measurement object by 1 becomes equal.

In the embodiment, the irradiation position of the light beam is displaced to a two-dimensional point by using the galvanomirror 12.
In a simple type, the irradiation position of the light beam by the galvanometer mirror 12 may be displaced only in one axis direction. In this case, the direction of the displacement may be a direction that intersects (orthogonally) with the scanning direction of the uniaxial scanning stage 31. In this case, it can be considered that the displacement of the two-dimensional galvanomirror 12 in the one axis direction is fixedly given. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0021]

As described above, according to the present invention, the irradiation position of the light beam irradiating the object to be measured via the objective lens and the detection position of the reflected light of the light beam are determined by the light forming the collimator optical system. Since the optical path is optically displaced by deflecting the optical path using a two-dimensional reflecting mirror (galvanometer mirror) on the road, the height of the object to be measured at an arbitrary position can be maintained while maintaining high measurement accuracy by the confocal method. Can be measured at high speed. Moreover, a great effect in practical use such as simplification of the device configuration can be obtained.

In particular, a condenser lens as focus adjusting means is provided with two lenses.
The converging lens is provided in front of the three-dimensional movable mirror to move the converging lens in the optical axis direction, and the optical path between the converging lens, the light source, and the light receiver is a collimator optical system.
Effects such as miniaturization of the three-dimensional movable mirror and enabling high-speed tilt control thereof can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an optical inspection device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of an optical inspection apparatus configured by incorporating an image processing apparatus.

FIG. 3 is a diagram for explaining the principle of height measurement by a confocal method.

FIG. 4 is a diagram showing a change in the amount of reflected light received with a change in a focal position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Objective lens 12 Galvano mirror (two-dimensional movable mirror) 13 Focus adjustment means 13a Condensing lens 13b Actuator 14 Quarter-wave plate 15 Beam splitter 16 Projection system 17 Light source (semiconductor laser) 18 Collimator lens 19 Astigmatism correction lens Reference Signs List 20 light receiving system 21 light receiving device (phototransistor) 22 aperture 23 imaging lens (light receiving lens) 30 TV camera 31 uniaxial scanning stage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/66 H01L 21/66 J

Claims (3)

[Claims] A light source for outputting a light beam; a light source arranged opposite to the inspection object to irradiate the measurement object with the light beam; and condensing light reflected by the inspection object coaxially with the light beam. An objective lens, a beam splitter for separating reflected light condensed via the objective lens from an optical path of the light beam, a light receiving device for receiving the reflected light separated via the beam splitter, Focus adjusting means for changing a substantial optical path length of the light beam and the reflected light with respect to the inspection object through the lens, and a light beam which deflects the light beam output from the light source in a predetermined direction and passes through the objective lens And a two-dimensional movable mirror for displacing the irradiation position of the light source, condensing the reflected light from the irradiation position via the objective lens, and guiding the reflected light to the light receiver. Optical inspection equipment. 2. An optical path between the light source and the focus adjusting means and an optical path between the light receiver and the focus adjusting means are provided as a collimator optical system. Optical inspection equipment. 3. The optical inspection device according to claim 1, wherein the focus adjustment means comprises an actuator for moving and displacing a condenser lens provided in front of the two-dimensional movable mirror in an optical axis direction. apparatus.