JPS62299706A - Pattern inspecting instrument - Google Patents

Abstract

PURPOSE:To accurately detect even a multilayered three-dimensional fine pattern by scanning linear light by a light deflecting means and detecting light cutting lines formed on a body to be inspected by a line sensor successively. CONSTITUTION:When the linear light l1 is scanned by the light deflecting means 1a from t0 to DELTAt as shown by an arrow A, a light cutting line L formed on the body M to be inspected moves from, for example, L1 to L5 successively according to the scanning. Those light cutting lines L1-L5 are observed by the line sensor 2a in a fixed direction to detect only parts crossing the detection direction N. Consequently, when a three-dimensional pattern P, for example, is detected, the linear light l1 is scanned once to obtain one light cutting image consisting of detected images m1-m5 corresponding to the light cutting lines L1-L5. This light cutting image is obtained at each position of the body M to be detected and they are seen totally to accurately detect the three- dimensional shape of the pattern P.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Summary] The present invention provides a pattern inspection device that detects the three-dimensional shape of a pattern using a light cutting method, in which a line-shaped light is deflected by a light deflection means. The line sensor sequentially detects the light cutting lines formed on the object according to the scanning, and the three-dimensional shape of the pattern is detected based on the obtained detection image. For example, it is possible to accurately detect multilayer three-dimensional fine patterns on an IC wafer.

, [Industrial Application Field] The present invention optically and automatically measures fine patterns formed on wafers such as TC and LSI, wiring patterns on printed boards, and the mounting state of chip components on printed boards. The present invention relates to a pattern inspection device for inspection.

Recently, with the increase in the density of IC and LSr patterns, the pattern width has become extremely narrow to about 1 μm. Therefore, automatic inspection that targets not only printed circuit boards and chip components but also the above-mentioned fine patterns has become important in improving product reliability and yield.

□ [Prior Art] Until now, devices have been developed that use transmitted light to inspect reticles and photomask patterns, but transmitted light cannot be used for opaque wafer patterns.

Therefore, conventionally, devices have been developed that utilize (i) spot scanning, (ii) gray scale images, (iii) interference color, etc. using a laser beam.

[Problem that the invention seeks to solve]

In any case, the above-mentioned conventional devices are unable to accurately discriminate fine patterns such as three-dimensional shapes in which wiring made of aluminum or the like is stacked in multiple layers.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a pattern inspection device that can accurately detect even multilayer three-dimensional fine patterns.

[Means for solving problems]

The present invention utilizes a light cutting method and is comprised of three means: a light irradiation means, a light detection means, and an image processing means.

The principle is shown in FIG. 1(a).

The light irradiation means 1 irradiates a line-shaped light β1 onto a test object M such as an IC wafer, and directs this light in the line direction of the light 11 (see FIG. In (a), it is a means for scanning in a direction (direction perpendicular to the plane of the paper) and a direction perpendicular to the direction (direction of arrow A). According to this scanning, light cutting lines are sequentially formed on the object M along the irregularities thereof.

The light detection means 2 detects the light cutting line as the light! .

The irradiation directions are sequentially detected from different fixed directions by a line sensor 2a. By detecting the light cut-Ur line with the line sensor 22 in this way, the light 1. One photosection image is obtained for each scan of .

The image processing means 3 determines the specimen M based on the photocutting image.
This is a means for detecting the three-dimensional shape of the above pattern.

[For production]

The present invention will be described in detail based on FIG. 1 (bl, (C1).

First, by the light deflecting means 1a shown in FIG. 1(a),
As shown in FIG. 1 (bl), if the line-shaped light β is scanned by Δt from to in the direction of arrow A, the light cutting line formed on the test object M will be, for example, It will move sequentially from Ll to Ll.If these light cutting lines Ll to L are observed sequentially from a certain direction with the line sensor 2a, only the part that intersects with the detection direction N will be detected. As a result, for example, Fig. 1(b)
In the case of a three-dimensional pattern P as shown in FIG. 1 consisting of m5
Two photosection images are obtained.

If such light-cut Ur images are obtained for each position of the object M and viewed as a whole, the three-dimensional shape of the pattern P can be detected accurately.

According to the present invention, multilayer three-dimensional fine patterns on IC or LSI wafers can be easily detected using the same principle as described above.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram showing a first embodiment of the present invention.

In this example, light irradiation means (11 to 17), light detection means (
16 to 21) and image processing means (image processing circuit 22)
It consists of

In the light irradiation means, the laser beam "11" output from the laser 11 is passed through the cylindrical lens 12, the mirror 13, and the cylindrical lens 14 into a line-shaped light a1.
Convert to □. This line-shaped light 11□ is deflected by an ultrasonic deflector I5 in a direction perpendicular to the line direction (in the direction of arrow B). The ultrasonic deflector 15 is driven by the deflector drive section 24 according to instructions from the CPU 23. Next, this deflected light 11° is transmitted through the polarization separation film 16, and the objective lens 1
The light beam is irradiated onto a test object M, which is, for example, an IC or LSI wafer, through the center of the laser beam 7. Then, a line-shaped light N+4 obtained on the object M through the objective lens 17
is scanned in the same direction as the above-mentioned arrow B direction.

Therefore, on the test object M, the above-mentioned light 7! Depending on the scan of ,
As shown in FIG.
Based on instructions from the CPU 23, the table driving section 25 sequentially moves the light beam 114 in a direction perpendicular to the line direction of the light beam 114. Every time the object M moves a predetermined distance, the ultrasonic deflector 15 scans the light J+4 once.

The light detection means includes an objective lens I7 and a polarization separation film 1G.
is shared with the light irradiation means, and first, reflected light β15+i! from the above-mentioned light cutting line in two constant directions is reflected. +6 is guided to the polarization separation film 16 through both ends of the objective lens 17.

This polarization separation film 16 is a film that transmits only light having a certain polarization direction and reflects light having a polarization direction perpendicular to that polarization direction. Through this polarization separation film 16, the light 7!13 having a certain polarization direction is transmitted as is, while the scattered light component 118a+ of the reflected light 'IS+116
116m is reflected. Therefore, strong reflection due to specularly reflected light can be suppressed.

Next, the above nk scattered light component 'I5+'! 16 are reflected by mirrors 18 and 19, respectively, and applied to line sensors 20 and 21 such as CCD line sensors. That is, the above-mentioned optical cutting line on the test object M is connected to the two line sensors 20, 2.
1, it will be observed from two fixed directions. Then, as shown in FIG. 1(b), only the reflected light from the part intersecting the detection direction is sequentially detected by the line sensor 20.21.
It will be detected.

As a result, by arranging the detection signals for a plurality of lines sequentially obtained by each line sensor 20, 21 for one scan of the line-shaped light 1+4, one light section image is obtained. This optically cut image corresponds to a cross-sectional shape when the object M (including the pattern P) is cut in the detection direction (slope) of the line sensor 20.21.

Note that by simultaneously observing the object M from both sides with the two line sensors 20 and 21 in this way, the influence of shadows caused by the pattern P is eliminated, and accurate detection is possible. For example, as shown in FIG. 3, even if one reflected light j2+5 from the object M is hidden by the pattern P and is not detected by the line sensor 20, the other reflected light eIh is detected by the line sensor 21. detected. Therefore, each line sensor 20.2 for the shaded area
By complementing each other, the light sectioned images obtained in step 1 can become a complete image without the influence of shadows.

In addition, in the above optical system, the numerical aperture for both illumination and detection is
There is an advantage that selection can be made without mutual interference.

Next, the light section image obtained for each scan mentioned above is
As the object M moves, it is sequentially stored in the image processing circuit 22 as a memory brain MP, as shown in FIG. 4(a). Here, each of the light-cut images in the memory brain MP corresponds to the cross-sectional shape when cut along the slope, which is the detection direction of the line sensor 20.21, as described above, so this image is The image is shaped so that it has a cross-sectional shape along the vertical plane that is the incident direction of the linear light 114, that is, it has the same light distribution as the light cutting line formed at the same position on the test object M. Perform the conversion process.

The processing for this image conversion is shown below.

First, as shown in FIG. 4(a), the memory plane MP
If it is composed of N image lines in the height direction, then as a premise for performing the above image conversion process,
For example, n in any nth memory brain MP
th image line and n+1th memory plane M
P 11. The line sensors 20 and 21 are arranged so that the n+1-th image line in
The signal readout timing from the xy child table 6 and the moving speed of the xy child table 6 are synchronized. Under such conditions,
As shown in FIG. 4 (bl), the address controller 22
According to the instructions in a, for example, the nth memory plane MP
, the n-th image line is sequentially extracted from n=1 to N, and these are combined to obtain one image. The light section image obtained in this manner has a cross-sectional shape along a vertical plane, and has the same light distribution as one light section line.

Next, in FIG. 4 (bl), the three-dimensional shape of the pattern P is obtained by determining the height of each position using the height discrimination circuit 22b from the light-cut image of each position obtained as described above. Next, the pattern determination circuit 22C determines whether the pattern P is defective or the like.

Therefore, according to this embodiment, the pattern P
Because it can accurately detect the three-dimensional shape of
Multilayer three-dimensional fine patterns on SI wafers and the like can also be easily detected.

Next, a second embodiment of the present invention is shown in FIG.

In this example, the light irradiation means (31 to 37), the light detection means (
36 to 42) and an image processing means (not shown).

In the light irradiation means, the laser beam 12+ outputted from the laser 31 is guided to the ultrasonic deflector 34 via the beam shaping lens 32 and the mirror 33, and is deflected in the direction of arrow C here, in the same manner as in the first embodiment. shake.

This deflected light is converted into linear light β2□ by the cylindrical lens 35. In addition, the light at this time 12□
The line direction is made perpendicular to the deflection direction (direction of arrow C). Next, the above-mentioned line-shaped light 12□ is irradiated onto the test object M placed on the xy child table 3 by 1ffJ via the beam splinter 36 and the objective lens 37. Then, the line-shaped light 123 obtained through the objective lens 37 on the object M is scanned in a direction perpendicular to the line direction (the same direction as the above-mentioned arrow C direction), and the scanning According to this, a light cutting line is formed in the same manner as described above.

The light detection means shares an objective lens 37 and a beam splitter 36 with the light irradiation means, and the light 7!24+'25 reflected from the light cutting line in two constant directions is sent to the beam splitter via the objective lens 37. 36, the reflected light is divided into two directions, upper and lower, by a prism mirror 38, deflected 906 times by reflecting mirrors 39 and 40, and then detected by line sensors 41 and 42.

In this embodiment, the line sensors 41 and 42 are arranged so that their light receiving surfaces are perpendicular to the light reflected by the reflecting mirrors 38 and 40. Moreover, as is clear from FIG. 6(a) (side view), the line sensor in the optical system 100 composed of the beam 1, the splitter 36, the prism mirror 38, the reflecting mirror 39.40, and the line sensor 41.42 The optical paths a, b, and c are selected so that the dimension 1 in the direction perpendicular to 41.42 (in the direction of the arrow) falls within the diameter d of the objective lens 37. In addition, Figure 6 (
The maximum dimension in the lateral direction (direction of arrow E) in b) (front view) is the length t2 of the line sensors 41 and 42 in the line direction.
It is.

By using the optical system 100 and the objective lens 37 having the above-mentioned dimensional relationship, it is possible to treat these as one element and arrange a plurality of elements closely together, as shown in FIG. 7, for example. In FIG. 7, a plurality of elements are arranged closely together in the direction of arrow E without shifting the pitch, while in the direction of arrow E, line sensors 41 and 42 in adjacent elements are arranged close to each other so as not to collide with each other. They are arranged closely and shifted by a half pitch t3/2.

By arranging a plurality of elements closely in this manner, image processing can be performed in parallel for each element, thereby enabling even higher speed processing. Note that image processing for each element can be performed in the same manner as in the first embodiment.

Next, a third embodiment of the present invention is shown in FIGS. 8 and 9. This embodiment is composed of light irradiation means (51 to 56), light detection means (57 to 60), and image processing means (61 to 67), and in particular, a condensing lens 5 of the light irradiation means.
6 and observation lenses 57 and 58 of the light detection means are provided separately from each other.

In the light irradiation means, the laser 51
First, the laser beam fi+ outputted from the ultrasonic deflector 52
swing it in the direction of arrow F, and then move it to the mirror 53 and lens 5.
By passing the light through the cylindrical lens 55 via the light beam 4, the light is converted into a line-shaped light 132. Then, this waved line-shaped light "3Z is irradiated onto the test object M through the condensing lens 56. Then, on the test object M, the Light on the line l.

is scanned in a direction perpendicular to the line direction, and a light cutting line is formed according to the scanning.

In the light detection means, the line sensor 59.60 observes the reflected light '34r7!35 from the light-cut cotton in two constant directions via a separately provided observation lens 57.58. In this way, by providing the observation lenses 57 and 58, the focal length of the observation lenses 57 and 58 can be made variable independently of the condensing lens 56, and thus the desired resolution can be obtained. Can be done. Therefore, 1
It is possible not only to inspect minute patterns that require a resolution of less than .mu.m, but also to detect object shapes (about 10 to 100 .mu.m in height) that require a resolution of about 5 to 20 .mu.m as necessary.

As the image processing means, the same means as in the first embodiment may be used, but as another example, the circuit shown in FIG. 9 may be used. In the same figure, the detection signals of line sensors 59 and 60 are rearranged by rearrangement circuits 61 and 62, respectively, in the same manner as in FIG. 4 Tbl to obtain a light-cut image along the vertical plane. The light cut image obtained in this way has a slight spread in the height direction of the image due to the influence of light from the surroundings, etc., but the light intensity is the highest within that spread in the height direction. (peak) corresponds exactly to the actual optical cutting line. Therefore, the rearrangement circuit 6
From the photocutting image obtained in 1.62, the peak detection circuit 6
3.64, the peak in the height direction is detected, and a light section image consisting only of the peak value is taken out. By combining the light cut images from both directions obtained by these two peak detection circuits 63 and 64 in the combining circuit 65, they complement each other as described in FIG. In addition to obtaining an image, the two-dimensional shape of the entire Bakun is also obtained. By binarizing this in a binarizing circuit 66, only the necessary patterns are extracted separately from unnecessary parts. Next, the discrimination circuit 67 compares the binarized pattern with a pre-stored reference pattern.
Determines the presence or absence of various defects in the pattern.

Note that the light deflection means used in the present invention includes:
Not limited to the above-mentioned ultrasonic deflector, for example, a galvano mirror
etc. may also be used. Furthermore, the line sensor is not limited to a CCD line sensor either.

Also, ICJ as a test object? It can be used not only for 3LSI wafers, but also for printed boards, chip parts, etc.
It can be applied to any pattern.

〔Effect of the invention〕

According to the present invention, not only printed boards and chip parts, but also
Even multilayer three-dimensional fine patterns on IC or LSI wafers, etc., can be accurately detected without being affected by the quality of the contrast or the unevenness of the surface shape.

[Brief explanation of drawings]

Figures 1+8) to (C) are diagrams of the principle of the present invention, Figure 2 is a configuration diagram showing the first embodiment of the present invention, Figure 3 is a diagram showing the advantages in detection from two directions, 4(a) and 4(b) are diagrams showing image processing by the image processing circuit 22 shown in FIG. 2, FIG. 5 is a block diagram showing the second embodiment of the present invention, and FIG.
a) and (bl) are a side view and a front view showing the configuration of the optical system according to the same embodiment, FIG. Figure 8 shows the third aspect of the present invention.
FIG. 9 is a block diagram showing an image processing circuit in the same embodiment. l... Light irradiation means, la... Light deflection means, 2... Light detection means, 2a... Line sensor, 3... Image processing means, 15... Ultrasonic deflector, 16. ...Polarization separation film, 17...Objective lens, 20.21...Line sensor, 22...Image processing circuit, 34...Ultrasonic deflector, 36...Beam splitter, 37...・Objective lens, 38... Prism mirror, 39.40... Reflection mirror, 41.42... Line sensor, 52... Ultrasonic deflector, 56... Condensing lens, 57.58 ...Observation lens, 59.60...Line sensor.

Claims (1)

[Claims] 1) A line-shaped light is irradiated onto the test object on which a pattern is formed, and the line-shaped light is deflected by a light deflecting means (1a).
A light irradiation means (1) that scans in a direction perpendicular to the line direction of the light, and a light cutting line formed on the test object according to the scanning by the light irradiation means, Line sensor (2) from a certain direction different from the irradiation direction
a); and an image processing means (3) that detects the three-dimensional shape of the pattern on the test object based on the light sectioned image obtained from the light detection means. A pattern inspection device characterized by: 2) The light detection means includes two sets of the line sensors,
2. The pattern inspection apparatus according to claim 1, wherein the optical cutting line is detected from two different directions. 3) The light irradiation means and the light detection means share an objective lens (17), and the light that has passed through the light deflection means is irradiated onto the object through the center of the objective lens, and 3. The pattern inspection apparatus according to claim 1, wherein the optical cutting line is detected by the line sensor through an end of the objective lens. 4) The light irradiation means and the light detection means further share a polarization separation film (16) that transmits only light having a certain polarization direction and reflects light having a polarization direction perpendicular to the polarization direction, The polarization separation film transmits the light obtained by the light deflecting means and guides it to the objective lens, and also reflects the scattered light component from the light cutting line obtained through the objective lens to separate the light from the line. The pattern inspection device according to claim 3, characterized in that the pattern inspection device is guided to a sensor. 5) The light detection means includes a prism mirror (38) and a reflection mirror (39) for guiding reflected light from the light cutting line obtained through the objective lens to the line sensor.
, 40), wherein a dimension of an optical system (100) composed of the prism mirror, the reflective mirror, and the line sensor in a direction perpendicular to the line sensor is equal to or less than the diameter of the objective lens. A pattern inspection device according to claim 3 or 4. 6) A plurality of elements including the optical system and the objective lens are arranged closely together without shifting pitches from each other in the line direction of the line sensor, and are shifted by half a pitch from each other in a direction perpendicular to the line direction. The pattern inspection device according to claim 5, characterized in that the pattern inspection device is arranged closely. 7) The light irradiation means has a condensing lens (56) for guiding the light that has passed through the light deflection means onto the test object,
The light detection means has an observation lens (57, 58) separate from the condenser lens for guiding the reflected light from the object to the line sensor, and has a focal length of the imaging lens. Claim 1 characterized in that it is changeable.
The pattern inspection device according to item 1 or 2. 8) The image processing means changes the processing order of detection signals obtained by sequentially detecting each position on the object moving in a direction perpendicular to the line direction of the linear light with the line sensor. , obtaining the same light distribution as a light section line formed at the same position on the test object, and detecting the three-dimensional shape of the pattern based on the light distribution. The pattern inspection device according to any one of items 7 to 8. 9) The pattern inspection apparatus according to any one of claims 1 to 8, wherein the light deflection means is a galvano mirror. 10) The optical deflection means is an ultrasonic deflector (15, 34, 5
2) The pattern inspection device according to any one of claims 1 to 8. 11) The pattern inspection apparatus according to any one of claims 1 to 10, wherein the line sensor is a CCD line sensor.