JPS62188944A - Surface condition measuring apparatus - Google Patents

Abstract

PURPOSE:To enable an increase in separate detection rate of a foreign matter for a circuit pattern, by arranging an optical axis of a focusing section of a light receiving means to be positioned on the incidence side with respect to a normal within an incidence surface of a substrate. CONSTITUTION:A polygon mirror 2 and a projection section 4 compose a part of a projection means. A mirror 2 is rotated to scan over a substrate 5 from a point B1 to point B2 while the substrate 5 is moved in the direction of the arrow S1 or S2 to scan the whole of substrate 5. A focusing section 6 is provided on the incidence side with respect to a normal on an incidence surface of the substrate 5 and focus scattered luminous fluxes from a foreign matter on the substrate 5 and then introduced to a light receiving surface 9 with a lens 8. The focusing section 6, the mirror 7 and the lens 8 composed a part of a light receiving means. On the other hand, with the rotation of the mirror 2, a luminous flux emitted at the reflection point PG is scattered by the foreign matter on the substrate 5 to be focused 6. This can achieve a higher separate detection rate of a foreign matter for a circuit pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a surface condition measuring device, and particularly to a surface condition measuring device that is used in semiconductor manufacturing equipment to measure a surface condition on a substrate such as a reticle or a photomask on which a circuit pattern is formed. The present invention relates to a surface condition measuring device suitable for detecting foreign matter such as impermeable dust.

(Prior Art) Generally, in the IC manufacturing process, a semiconductor printing device (stepper or mask aligner) is used to print a circuit pattern for exposure formed on a substrate such as a reticle or a photomask.
It is manufactured by transferring it onto eight surfaces of sea urchins coated with resist.

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

In particular, when using a reticle and printing a circuit pattern on eight sides by turning the edges using the step-and-repeat method, a single foreign object on the reticle surface is printed onto the entire wafer surface, resulting in IC manufacturing (') 3p fil. This will cause a significant decrease in performance.

Therefore, in the IC manufacturing process, it is essential to detect the presence of foreign matter on the substrate, and various inspection methods have been proposed. For example, FIG. 2 shows an example of a method that utilizes the property of foreign objects to scatter light equally. In the figure, the beam from the laser IO is divided into two by a half mirror 13 via a scanning mirror 11 and a lens 12, and is made incident on the front and back surfaces of a substrate 15 by two mirrors 14 and 45, respectively. The mirror 11 is rotated or vibrated to scan the substrate 15. A plurality of light receiving sections 16, 17, 18 are provided at positions away from the optical path of direct reflected light and transmitted light from the substrate 15, and output signals from these plurality of light receiving sections 16, 17, 18 are used to The presence of objects above is being detected.

In other words, since the diffracted light from the circuit pattern has strong directionality, the output value from each light receiving part will be different, but if the light beam is incident on a foreign object, the incident light flux will be scattered equally, so the output values from multiple light receiving parts will be different. Each becomes equal. Therefore, the presence of foreign matter is detected by comparing the output values at this time.

Furthermore, FIG. 3 shows an example of a method that utilizes the property that foreign matter disturbs the polarization characteristics of an incident light beam. In the same figure, the light beam from the laser 10 is converted into a light beam in a predetermined polarization state through a polarizer 19, a scanning mirror +1, and a lens 12, and then a half mirror 13
The light beam is divided into two parts by two mirrors 14 and 45, and the light is incident on the front and back surfaces of the substrate 15, respectively, and the scanning mirror 11 scans the substrate 15. Two light receiving sections 21.2 each having an analyzer 20.21 disposed in front thereof are located away from the optical paths of direct reflected light and transmitted light from the substrate 15.
There are 3.

Then, the difference in the amount of light received due to the difference in polarization ratio between the diffracted light from the circuit pattern and the scattered light from the foreign object is detected by the two light receiving sections 21 and 23, thereby distinguishing between the circuit pattern on the board 15 and the foreign object. Separate.

However, in both of the detection methods shown in Figures 2 and 3, the direct reflected light and transmitted light of the incident light beam do not enter the light receiving section, but a portion of the diffracted light of each order from the circuit pattern enters the light receiving section. . For this reason, when taking the output difference between the diffracted light from the circuit pattern and the scattered light from a foreign object, if the reflectance or shape of the foreign object differs, the output difference between both will fluctuate and the detection rate of the foreign object will decrease. There were some drawbacks.

(Problems to be Solved by the Invention) The present invention has a high separation detection rate that allows foreign substances such as dust on a board to be detected separately from circuit patterns in any state with high accuracy. The purpose of the present invention is to provide a surface condition measuring device with

(Means for Solving the Problem) A light projecting means illuminates a substrate on which a pattern is formed with a light beam obliquely from above to scan the substrate, and a light receiving means collects a scattered light beam from the substrate. When measuring the surface condition of the substrate using the output signal from the light receiving means, the optical axis of the light condensing part of the light receiving means is on the incident side with respect to the normal to the incident plane of the substrate. It was arranged so that it would come to a close.

In addition, the features of the present invention will be described in Examples. Fig. 1 is a schematic diagram of an optical system according to an embodiment 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 is formed on a substrate 5, which is an object to be measured such as a reticle, by a light projector 4 having, for example, an f-θ lens. The light is focused on point O.

The polygon mirror 2 and the light projecting section 4 constitute part of a light projecting means. The polygon mirror 2 is rotated to scan the substrate S from point B to point B2, and the entire surface of the substrate 5 is scanned by moving the substrate 5 in the direction of arrow S1 or arrow S2.

A light condensing section 6 is located on the incident side with respect to the normal to the incident surface of the substrate 5.
is provided to condense the scattered light beam from the foreign matter on the substrate 5, condense it at a point P6' via the mirror 7, and then guide it to the light receiving surface 9 by the lens 8.

The condensing section 6, mirror 7, and lens 8 constitute a part of the light receiving means. Mirror 7 on the extension of optical axis 8 of lens 8
The line connecting the intersection 71 with the intersection O on the substrate 5 is the light condensing part 6
is the optical axis of , and the intersection point 0 and the reflection point P6 of the polygon mirror 2
The line connecting them is the optical axis of the light projecting section 5.

In this embodiment, point PG is the position where, as the polygon mirror 2 rotates, the light beam diverging from the reflection point P6 is scattered by foreign matter on the substrate 5 and is focused by the condenser 6.

FIG. 4 is an explanatory diagram of the incident light beam 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 board corresponds to the equatorial plane of the schematically drawn sphere S. Most of the shapes of circuit patterns on substrates of semiconductor circuit patterns currently in use are composed of patterns indicated by T, . . . T2, which are perpendicular to each other in the vertical and horizontal directions. Now, a light beam is made to enter at an incident angle α from diagonally above the direction indicated by the arrow I of the batanine T2. Then, the plane formed by points A, μ, and A° in the figure becomes an incident plane, and the direct reflected light from the substrate 5 is reflected in the direction indicated by the arrow I°. At this time, if Po is the intersection point with the sphere S, then diffraction images of each order are formed in a direction orthogonal to each pattern T, , T2 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. 5(8).

If the circuit pattern is a repeating pattern such as a memory pattern, the diffraction image Q appears discretely as shown in FIG. 5(II).

In either case, the intensity of the diffraction image from the circuit pattern becomes weaker as the distance from the point P° of the directly reflected light beam increases. That is, the intensity of the diffracted light becomes considerably weaker when it passes from the point P' to the vicinity of the point P, which passes through the normal μ in the plane of incidence and intersects with the sphere on the incident side of the incident light beam.

On the other hand, since the scattered light from foreign objects is generated in the same direction, a large amount appears on the incident side as well.

Therefore, in this embodiment, the optical axis of the condensing part of the light receiving means is placed as far away from the optical path of the direct reflected light as possible, that is, on the incident side with respect to the normal μ in the incident plane. The influence of the diffracted light is reduced as much as possible, so that only the scattered light from the foreign matter on the substrate 5 is mainly received.

This increases the rate of separation and detection of foreign matter from circuit patterns. In order to increase the separation detection rate, if the optical axis of the condensing part is placed on point P, then the larger the angle δ between point P' and the center O of point P, for example 60 °
It is preferable to set it in the range of δ<180°.

In addition, in Figure 4, for the directly transmitted light in which the incident light beam passes through the substrate, the intersection with the sphere S is P'', and δ is the angle between the points P and the center 0 of the points P'', as in the case of the reflected light beam. In this case, it is better to set the extending angle δ in the same way as described above.

Furthermore, in this embodiment, arranging each element so that the optical axis of the condensing section is within ±45 degrees with respect to the optical axis of the light projecting section effectively increases the rate of separating and detecting foreign objects from the circuit pattern. It is preferable because it can be done.

In addition, if the optical axis of the light emitter is at an angle of 60 degrees with respect to the substrate, the optical axis of the converging section should be aligned with the substrate so that it is on the incident side with respect to the normal line within the incident plane. The angle ranges from 15 degrees to 90 degrees.

FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention.

In this embodiment, the light projecting section 4 and the condensing section 6 in the embodiment shown in FIG. Accordingly, a half mirror 62 is used in place of the mirror 7 in FIG. 1 to transmit and reflect a portion of the incident light beam and the scattered light beam. Other elements that are the same as those shown in FIG. 1 are given the same reference numerals.

In the embodiments shown in FIGS. 1 and 6, the optical function of the lens 8 is the reflection point P of the polygon mirror 2. It is also possible to form an image on the light-receiving surface 9 at a point P6' that is conjugate with .Also, the substrate 5 and the light-receiving surface 9 may be in a conjugate relationship and the point P. The light beam emitted from the light beam may be guided to the light-receiving surface 9 as a parallel light beam.

(Effects of the Invention) According to the present invention, it is possible to spatially avoid the diffracted light generated from the circuit pattern on the board and selectively receive only the scattered light flux from the foreign matter existing on the board. It is possible to achieve a surface condition measuring device with a high rate of separating and detecting foreign substances from circuit patterns.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention, FIG. 4 is an explanatory diagram of an incident light beam and diffracted light due to a circuit pattern in the embodiment of FIG. 1, and FIG. 5 (8). (b) is an explanatory diagram showing the relationship between the circuit pattern and the diffraction image;
FIG. 6 is a schematic diagram of an optical system according to another embodiment of the present invention;
3 and 3 each show an example of a conventional surface condition measuring device. In the figure, 1 is a light source, 2 is a polygon mirror, 4 is a light projector, and 5
6 is a substrate, 6 is a condenser, 7 is a mirror, 8 is a lens, 9 is a light-receiving surface, IO is an optical system, and 11 is a half mirror.

Claims (3)

[Claims] (1) A light beam is incident on a substrate on which a pattern is formed obliquely from above by a light projecting means to scan the substrate, a light receiving means receives a scattered light beam from the substrate, and the light receiving means When measuring the surface condition of the substrate using the output signal from the substrate, the optical axis of the condensing part of the light receiving means is arranged on the incident side with respect to the normal to the incident plane of the substrate. A surface condition measuring device featuring: (2) The surface according to claim 1, wherein the optical axis of the light converging section is arranged within ±45 degrees with respect to the optical axis of the light projecting section of the light projecting means. Condition measuring device. (3) The surface condition measuring device according to claim 1, wherein the light converging section is constituted by a part of the optical system of the light projecting means.