JPH0621877B2 - Surface condition measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface condition measuring apparatus, and particularly to a surface condition measuring device other than a circuit pattern on a substrate such as a reticle or a photomask on which a circuit pattern used in a semiconductor manufacturing apparatus is formed. The present invention relates to a surface state measuring apparatus suitable for detecting foreign matter, such as impermeable dust.

(Prior Art) Generally, in an IC manufacturing process, a circuit pattern for exposure formed on a substrate such as a reticle or a photomask is used as a semiconductor printing apparatus (stepper or mask aligner).
Is transferred onto the surface of the wafer coated with the resist to manufacture.

At this time, if foreign matter such as dust is present on the surface of the substrate, the foreign matter is also simultaneously transferred at the time of transfer, which causes a decrease in yield of IC manufacturing.

In particular, when a circuit pattern is repeatedly printed on the wafer surface by the step-and-repeat method using a reticle, one foreign substance on the reticle surface is printed on the entire surface of the wafer, which causes a large decrease in the yield of IC manufacturing. Is coming.

Therefore, it is essential to detect the presence of foreign matter on the substrate in the IC manufacturing process, and various inspection methods have been conventionally proposed. For example, FIG. 2 shows an example of a method of utilizing the property that a foreign substance scatters light in the same direction. In the figure, the laser is passed through the scanning mirror 11 and the lens 12.
The luminous flux from 10 is divided into two by the half mirror 13 and is made incident on the front surface and the back surface of the substrate 15 by the two mirrors 14 and 45, respectively, and the scanning mirror 11 is rotated or vibrated to scan the substrate 15. . Then, a plurality of light receiving portions 16, 17, 18 are provided at positions apart from the optical paths of the reflected light and the transmitted light directly from the substrate 15.
Is provided, and the presence of foreign matter on the substrate 15 is detected using the output signals from the plurality of light receiving units 16, 17, and 18.

That is, since the diffracted light from the circuit pattern has a strong directivity, the output value from each light receiving unit is different, but when a light beam enters a foreign object, the incident light beam is scattered in the same direction, so the output values from multiple light receiving units are different. Each becomes equal. Therefore, the presence of foreign matter is detected by comparing the output values at this time.

Further, FIG. 3 is an example of a method of utilizing the property that a foreign substance disturbs the polarization characteristic of the incident light beam. In the figure, a light beam from the laser 10 is made into a light beam having a predetermined polarization state through a polarizer 19, a scanning mirror 11 and a lens 12 and is divided into two by a half mirror 13 and two mirrors 14 and 45 are provided on a substrate 15 respectively. The light is incident on the front surface and the back surface, and the scanning mirror 11 scans the substrate 15. Further, two light receiving portions 21 and 23 having analyzers 20 and 21 arranged in front are provided at positions apart from the optical paths of the reflected light and the transmitted light directly from the substrate 15. Then, the difference in the amount of received light caused by the difference in the polarization ratio between the diffracted light from the circuit pattern and the scattered light from the foreign matter is detected by the two light receiving units 21 and 23, and the circuit pattern on the substrate 15 and the foreign matter are detected by this. Different.

However, in the detection methods shown in FIGS. 2 and 3, the reflected light and the transmitted light of the incident light flux do not enter the light receiving portion, but a part of the diffracted light of each order from the circuit pattern enters. . Therefore, when the output difference between the diffracted light from the circuit pattern and the scattered light from the foreign matter is taken, if the reflectance and shape of the foreign matter are different, the output difference of both will fluctuate and the foreign matter detection rate will decrease. There was a drawback to come.

(Problems to be Solved by the Invention) The present invention has a high separation detection rate capable of separating and detecting a foreign matter in any state such as dust existing on a substrate from a circuit pattern with high accuracy. An object of the present invention is to provide a surface condition measuring device.

(Means for Solving the Problems) A light projecting unit that makes a light beam enter a substrate on which a pattern is formed and scans the substrate with the light beam is different from the diffracted light generated from the main pattern on the substrate. In a device having a light receiving means for receiving a scattered light flux from a substrate and measuring the surface state of the substrate using an output signal from the light receiving means, the light projecting means is configured to project the light flux onto the substrate surface. The light beam is obliquely incident on the substrate from a direction inclined with respect to the normal, and has an optical axis in a direction inclined with respect to a direction in which the main pattern extends on the substrate, and the light beam is inclined with respect to a direction in which the main pattern extends. Scanning the substrate in different directions.

Besides, the features of the present invention are described in the embodiments.

(Example) FIG. 1 is a schematic view of an optical system of an example of the present invention. In the figure, a light beam from a laser 1 which is a light source is reflected in one direction by a polygon mirror 2, and a circuit pattern on a substrate 5 which is an object to be measured such as a reticle is formed by a light projecting section 4 having an f-θ lens, for example. It is focused on the point O.

The polygon mirror 2 and the light projecting section 4 form a part of the light projecting means. The polygon mirror 2 is rotated to scan the substrate 5 from the point B ₁ to the point B ₂ direction, and the substrate 5 is moved in the arrow S ₁ or arrow S ₂ direction to scan the entire surface of the substrate 5. . The direction of incidence of the light flux on the substrate surface by the light projecting portion may be from any direction other than vertical incidence, for example, it may be incident from an inclined direction.

Then, a light condensing unit 6 is provided above the substrate 5 to condense scattered light flux from a foreign substance on the substrate 5, condense it to a point P _G ′ via a mirror 7, and then guide it to a light receiving surface 9 by a lens 8. It is shining.

The condenser 6, the mirror 7 and the lens 8 form a part of the light receiving means. Mirror 7 on extension of optical axis 8 ₁ of lens 8
Intersection of the ₇₁ and the line connecting the intersection point O of the substrate 5 condensing unit 6
Of the optical axis of the polygon mirror 2 and the reflection point P _{G of the} polygon mirror 2
The line connecting the two is the optical axis of the light projecting unit 5.

The point P _G ′ in this embodiment is the position where the light beam diverging from the reflection point P _G is scattered by the foreign matter on the substrate 5 as the polygon mirror 2 rotates and is condensed by the light condensing unit 6.

In this embodiment, when the surface of the substrate 5 is scanned with a light beam by the rotation of the polygon mirror 2, an intersection line 1 connecting the points B ₁ and B ₂ formed by scanning in one direction is formed on the substrate 5. The angle β is shifted in the inclined direction so as not to coincide with the direction of the diffracted light generated from the pattern.

The condensing unit 6 is arranged with an angle β so that the projected image of the optical axis of the condensing unit 6 on the substrate 5 does not coincide with the direction of the diffracted light generated from the main pattern on the substrate 5.

That is, in this embodiment, the converging line 6 through the converging part 6 on the substrate and the converging line 1 ′ for condensing corresponding to the converging line 1 on the substrate are substantially aligned with the intersecting line 1 so that the scattered light beam generated from the foreign matter on the substrate is The light is efficiently guided to the light receiving surface 9.

The intersecting line 1'for condensing does not have to exactly match the intersecting line 1 as long as it coincides with the light beam 1 within a range in which the scattered light immediately from the foreign matter can be collected. Further, as long as the light condensing unit 6 is arranged so that the projected image of the optical axis of the light condensing unit 6 onto the substrate 5 is displaced from the direction in which the diffracted light due to the main pattern of the substrate 5 is generated, the light condensing unit 4 causes the light to be generated on the substrate 5. The intersection line 1 may be arranged so as to coincide with the direction in which the light diffracted by the main pattern on the substrate 5 occurs.

FIG. 4 is an explanatory diagram of incident light speed and diffracted light generated from the circuit pattern on the substrate 5 in the embodiment of FIG. Now, it is assumed that the circuit pattern surface on the substrate coincides with the equator surface of the sphere S schematically drawn. The shape of the circuit pattern on the substrate of the semiconductor circuit pattern which is currently used is almost composed of, for example, patterns which are orthogonal to each other in the vertical and horizontal directions indicated by T ₁ and T ₂ . Now, the light flux is made to enter the pattern T ₁ and the pattern T _{2 on the} substrate from the direction indicated by the arrow I in the vertical direction of the substrate 5. Then, the reflected light directly from the substrate 5 returns in the incident direction. If the intersection of the sphere S of the reflected light at this time is P ′, diffraction images of respective orders are formed in the direction orthogonal to the patterns T ₁ and T ₂ with the point P ′ as the center. When the circuit pattern is an isolated line, its diffraction image Q appears continuously in the direction orthogonal to the pattern T, as shown in FIG. Also, when the circuit pattern is a repeating pattern such as a memory, the diffraction image Q is shown in FIG.
It appears discretely as shown in (B).

In either case, the intensity of the diffracted image from the circuit pattern becomes weaker as the distance from the point P ′ immediately after the direct reflected light increases. That is, points A ', P', which are the directions in which the respective diffracted lights are generated from the point P ',
In the plane A'P'A formed by A and the plane C'P'C formed by points C ', P', C, the intensity of the diffracted light becomes considerably weaker as the distance increases.

On the other hand, the scattered light of the foreign matter is isotropically generated. Therefore, in the present embodiment, the optical axis of the light collecting portion of the light receiving means is as far as possible from the optical path of the direct reflected light, and the light is condensed at a position, for example, near the point P _{o, which} is offset from the direction of the diffracted light generated by the main pattern on the substrate. By arranging so that the optical axis of the portion is located, the influence of the diffracted light from the circuit pattern is minimized and only the scattered light from the foreign matter on the substrate 5 is mainly received.

That is, as shown in FIG. 1, the optical axis of the condensing portion forms an angle α with the substrate 5, and the projected image of the optical axis of the condensing portion onto the substrate 6 produces diffracted light due to the main pattern of the substrate 5. The direction, for example, the angle formed by the vertical and horizontal directions of the substrate 5 is parallel to or orthogonal to the orthogonal direction by an angle β.

FIG. 5 (C) is an explanatory diagram of the direction in which the diffracted light is generated and the optical axis direction of the condensing part of the light receiving means. In the figure, arrow 51 is the direction of the projected image of the optical axis of the condensing part on the surface of the substrate 5, and arrows 52 and 53 are the directions of the diffracted light generated by the main patterns T ₁ and T ₂ on the substrate, respectively.

As shown in the figure, in the present embodiment, the influence of the diffracted light is eliminated by specifying the arrangement of the light condensing unit, and only the scattered light flux from the foreign matter is condensed. As a result, the foreign matter separation detection rate with respect to the circuit pattern is increased.

In the present embodiment, the point P'to further increase the separation detection rate.
And the larger the angle δ formed with respect to the center O of the point P _o ,
It is preferable to set in the range of 60 ° <δ <180 °.

Further, in this embodiment, it is effective to increase the foreign matter separation detection rate with respect to the circuit pattern by arranging the respective elements so that the optical axis of the condensing section is within ± 45 degrees with respect to the optical axis of the light projecting section. It is possible because it is possible.

Actual circuit patterns on the board may include patterns in the directions of 30, 45, and 60 degrees with respect to the vertical and horizontal directions of the board. In order to sufficiently exert the effects of the present invention even on such a substrate, the angle formed between the projected image of the optical axis of the condensing portion on the substrate surface and the vertical and horizontal directions of the substrate is more than the parallel or orthogonal direction.
It is better to set within the range of 15 degrees ± 5 degrees.

Incidentally, in the present embodiment, even if the optical axis of the light projecting portion and the optical axis of the light condensing portion with respect to the substrate are arranged in the same direction with respect to the normal line in the incident plane of the light flux and separately on the right and left sides with respect to the normal line, the same is true. The object of the present invention can be achieved.

In the embodiment shown in FIG. 1, the optical action of the lens 8 may be such that a point P _G ′ that is conjugate with the reflection point P _G of the polygon mirror 2 is imaged on the light receiving surface 9 or the substrate 5 is used. The light-receiving surface 9 may be in a light-handling relationship, and the light flux emitted from the point P _G may be guided to the light-receiving surface 9 as a parallel light flux.

(Effect of the Invention) According to the present invention, it is possible to selectively receive only the scattered light flux from the foreign matter existing on the substrate while avoiding the diffracted light generated from the circuit pattern on the substrate spatially. It is possible to achieve a surface state measuring device having a high foreign matter separation detection rate with respect to a circuit pattern.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical system according to an embodiment of the present invention, FIG. 4 is an explanatory view of incident light speed and diffracted light depending on a circuit pattern in the embodiment of FIG. 1, and FIGS. 5 (A) and 5 (B). , (C) are explanatory views showing the relationship between the circuit pattern and the diffraction pattern, and FIGS. 2 and 3 are examples of conventional surface condition measuring devices. In the figure, 1 is a light source, 2 is a polygon mirror, 4 is a light projecting portion, 5 is a substrate, 6 is a light collecting portion, 7 is a mirror, 8 is a lens, and 9 is a light receiving surface.

Continuation of the front page (56) Reference JP-A-57-128834 (JP, A) Actual development S57-22239 (JP, U) JP-B 63-58369 (JP, B2)

Claims (1)

[Claims] 1. A scattered light beam from the substrate, which is different from a light-projecting means for making a light beam incident on a substrate on which a pattern is formed and scanning the substrate with the light beam, and diffracted light generated from a main pattern on the substrate. In the device for measuring the surface condition of the substrate by using the output signal from the light receiving unit, the light projecting unit is configured to measure the light flux with respect to a normal line of the substrate surface. The substrate is obliquely incident on the substrate from an inclined direction and has an optical axis in a direction inclined with respect to the extending direction of the main pattern on the substrate, and the substrate is provided in a direction inclined with respect to the extending direction of the main pattern by the light flux. A surface condition inspection device characterized by scanning.