JPH0621876B2 - 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 condition measuring device suitable for detecting foreign matter, for example, opaque 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 isotropically scatters light. In the figure, the laser is passed through the scanning mirror 11 and range 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 directly reflected light from the substrate 15 and the transmitted light. 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 because it can separate and detect foreign matter existing on a substrate in any state such as dust 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 for measuring the surface state of the substrate by using an output signal from the light receiving means, the light receiving means receives the scattered light flux from the substrate on a light receiving surface, A scanning mirror for scanning is provided, and the light flux is configured to be obliquely incident on the substrate from a direction inclined with respect to the normal line of the substrate surface, and the light receiving means causes the scattered light flux to be normal to the substrate surface. On the other hand, the light is received from a direction inclined to the light projecting means side, and the reflection point of the scanning mirror of the light projecting means forms an image on the light receiving surface.

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 polingon mirror 2 and the light projecting unit 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. .

Then, the light collecting portion 6 is provided on the incident side with respect to the normal line of the incident surface of the substrate 5.
Is provided, the scattered light flux from the foreign matter on the substrate 5 is condensed, is condensed to the point P _G ′ via the mirror 7, and then is guided to the light receiving surface 9 by the lens 8.

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 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. As an optical action of the lens 8, 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.

The converging line 1'for condensing does not have to exactly coincide with the intersecting line 1 as long as it coincides with the light beam 1 within a range in which the scattered light flux from the foreign matter can be condensed. 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 the incident light flux and the 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 incident on the pattern T ₁ and the pattern T ₂ on the substrate from a direction passing through a point P ₀ on the spherical surface at an angle α obliquely upward and an angle β deviated from the direction of the diffracted light generated by the main pattern. Then, the plane formed by points A, μ, A ′ in the figure becomes the incident surface and the substrate 5
The direct reflected light from is reflected in the direction passing through the point P ₀ ′ on the sphere S as shown by the arrow I ′.

Also the intersection between the sphere S of the reflected light in the case where that is incident light beam to the center point O from a point P on the sphere S parallel to the direction of the pattern T ₂ 'When the point P' P respectively around the Diffraction patterns of respective orders are formed in the direction orthogonal to the patterns T ₁ and T ₂ . 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. When the circuit pattern is a repeating pattern such as a memory, the diffraction image Q appears discretely as shown in FIG. 5 (B).

FIG. 5C is an explanatory diagram of the incident direction of the light beam and the direction in which the diffracted light is generated. In the figure, the luminous flux is emitted from the substrate 5 in the direction indicated by arrow 51.
When incident on the substrate, the main patterns T ₁ and T ₂ on the substrate show that diffracted light is generated in the directions indicated by arrows 52 and 53, that is, in the direction deviated from the incident direction by an angle β.

In either case, the points P _o ′ and P ′ of the directly reflected light flux
The farther away from it, the weaker the intensity of the reflected light and the diffraction image from the circuit pattern. That is, from the point P ₀ ′, the normal μ in the plane of incidence
Come to the intensity of the diffracted light becomes quite weak to the vicinity of the sphere and the intersection point P _o of the incident side of the incident light beam past.

On the other hand, the scattered light of the foreign matter is isotropically generated, and therefore a lot of it appears on the incident side.

Therefore, in this embodiment, the diffraction caused by the main pattern on the substrate is at a position where the optical axis of the condensing part of the light receiving means is as far as possible from the optical path of the direct reflected light, that is, on the incident side with respect to the normal μ in the incident plane. scattered light from as small as possible to foreign matter on the substrate 5 the influence of the diffracted light from the circuit pattern by arranging to come the optical axis of the condensing portion shifted to the direction of light for example the point P _o vicinity only Is mainly received.

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

The projection image of the optical axis of the light converging unit 6 on the substrate 5 and the projection image of the optical axis of the light projecting unit 5 on the substrate 5 are arranged to coincide with each other. The twins do not necessarily have to be matched as long as the scattered light can be collected.

As described above, the positions of the light projecting portion and the light condensing portion with respect to the substrate are specified, whereby the separation detection rate of foreign matter with respect to the circuit pattern is increased. In order to increase the separation detection rate, if the optical axis of the condensing part is arranged so as to be on the point P _o , the point P is assumed.
_It is preferable to set the range of 90 ° <δ <180 ° as the angle δ between _o ′ and the center O of the point P _o increases.

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 by 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 15 from the parallel or orthogonal direction. It is better to set within ± 5 degrees.

In this embodiment, the optical axis of the light projecting portion and the optical axis of the light condensing portion with respect to the substrate are not arranged in the same direction with respect to the normal line in the incident surface of the light flux, but are arranged separately on the left and right sides with respect to the normal line. Can achieve the object of the present invention as well.

FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention.
In this embodiment, the light projecting portion 4 and the light converging portion 6 in the embodiment of FIG. 1 are configured by one optical system 61, and the scattered light flux from the foreign matter is incident from the same direction as the incident light flux on the substrate 5. In this case, the half mirror 62 is used instead of the mirror 7 in FIG. 1 to partially transmit and reflect the incident light flux and the scattered light flux. In addition, the same elements as those shown in FIG. 1 are designated by the same reference numerals.

In the present embodiment, the substrate 5 and the light receiving surface 9 may have a conjugate relationship, and the light beam emitted from the point P _G ′ may be guided to the light receiving surface 9 as a parallel light beam.

(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 of an embodiment of the present invention, FIG. 4 is an explanatory view of incident light flux and diffracted light by a circuit pattern in the embodiment of FIG. 1, and FIGS. 5 (A) and 5 (B). , (C) are explanatory views showing the relationship between a circuit pattern and a diffraction image, FIG. 6 is a schematic view of an optical system of another embodiment of the present invention, and FIGS. 2 and 3 are conventional surface states. It is an example of a measuring device. In the figure, 1 is a light source, 2 is a polygon mirror, 4 is a light projecting unit, 5 is a substrate, 6 is a light collecting unit,
7 is a mirror, 8 is a lens, 9 is a light receiving surface, 10 is an optical system, 11
Is a half mirror.

 ─────────────────────────────────────────────────── ─── 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 flux from the substrate, which is different from a light projecting means for making a light flux incident on a substrate on which a pattern is formed and scanning the substrate with the light flux, and diffracted light generated from a main pattern on the substrate. And a light receiving means for receiving the light on a light receiving surface, wherein the light projecting means scans the substrate with the light beam in a device for measuring the surface state of the substrate using an output signal from the light receiving means. A mirror is provided, and the light flux is configured to be obliquely incident on the substrate from a direction inclined with respect to the normal line of the substrate surface, and the light receiving means projects the scattered light flux with respect to the normal line of the substrate surface. A surface state inspection device, characterized in that it is configured to receive light from a direction inclined to the means side and to form an image on a reflection surface of the scanning mirror of the light projecting means on the light receiving surface.