JPH0545945B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a surface condition measuring device, and in particular to a surface condition measuring device used in semiconductor manufacturing equipment, on a substrate such as a reticle or a photomask on which a circuit pattern is formed, and a pellicle protection device on the substrate. The present invention relates to a surface condition measuring device that accurately detects foreign matter such as impermeable dust when it is attached to the surface of a pellicle protective film when the membrane is attached.

(Prior Art) Generally, in the IC manufacturing process, a circuit pattern for exposure formed on a substrate such as a reticle or photomask is transferred onto a wafer surface coated with resist using a semiconductor printing device (stepper or mask aligner). Manufactured by

At this time, if foreign matter such as dust is present on the substrate surface, when the circuit pattern is transferred onto the wafer surface, the foreign matter will also be transferred at the same time, causing a reduction in the yield of IC manufacturing.

In particular, when a step-and-repeat method is used to repeatedly project and expose a circuit pattern on the reticle surface onto the wafer surface, a single piece of dust on the reticle surface is printed onto the entire wafer surface, causing a significant decrease in yield. .

Therefore, in recent years, it has become essential to detect the presence of foreign matter on a substrate in the IC manufacturing process, and various inspection methods have been proposed. For example, FIG. 2A is an example of a method that utilizes the property of foreign matter to scatter light isotropically.

In the same figure, a light beam emitted from a laser 20 is reflected by a polygon mirror 21 placed near the entrance pupil of an f-theta lens 22, and after passing through the f-theta lens 22, it is passed through an aberration correction plate 23 to a reticle 20. Arrow 27 points the reticle stage (not shown) on the surface.
It scans sequentially while moving along the direction.

In general, most of the circuit patterns on the surface of the reticle 24 have regularity, so that the diffracted light generated from the circuit patterns is also emitted in a direction following a certain rule.

On the other hand, dust on the surface of the reticle 24 generates scattered light in the same direction. Therefore, at this time, the condenser lens 26-1
By arranging the detection system 26, which includes a detector 26-2 and a light receiver 26-2, in a direction different from the emission direction of the diffracted light generated from the circuit pattern, only the scattered light generated from dust is detected.

However, with this method, it is necessary to scan and measure the front and back surfaces of the reticle 24 with a beam of light.
It took a lot of time and was mechanically very troublesome.

Furthermore, when pellicle protective films 28a and 28b are attached to the top and bottom of the reticle 24 as shown in FIG. 2B, dust may also adhere to the pellicle surface.
In this case, it is necessary to use the detection system 26 to determine which surface the dust is attached to, and it is very difficult to accurately perform this determination, and the mechanism tends to become very complicated.

(Problems to be Solved by the Invention) The present invention solves the problem of the presence and size of foreign objects such as dust and defects on the surface of a substrate such as a reticle or photomask, and also increases the number of surfaces to be measured by attaching a pellicle protective film to the substrate. It is an object of the present invention to provide a surface condition measuring device which is particularly suitable for semiconductor manufacturing equipment and can easily measure on which surface a foreign substance is present even when a foreign substance is present with high precision and in a short time.

(Means for Solving the Problem) The measurement surface is measured while the first and second light beams used for measuring the surface condition of a plurality of laminated measurement surfaces are incident on the measurement surface from different directions. Scanning simultaneously with the first and second beams,
The first plane is arranged such that the intersection line of the first plane defined by the incident direction and scanning direction of the first luminous flux and the second plane defined by the incident direction and scanning direction of the second luminous flux does not intersect the measurement surface. and the relationship between the second luminous flux is set.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1A is a schematic diagram of an optical system according to an embodiment of the present invention.

In the figure, 1 is the reticle, 1a and 1b are the front and back surfaces of the reticle, 2a and 2b are the upper and lower surfaces of the pellicle to prevent dust from adhering to the reticle 1, respectively, and 3 and 4 are the non-reticle surfaces. a light beam from the illustrated light source, e.g. a laser;
Similarly, by a scanning means such as a polygon mirror (not shown), the light beam 3 is directed to the pellicle top surface 2a and the reticle back surface 1b.
, the light beam 4 is between the pellicle lower surface 2b and the reticle upper surface 1.
a is scanned in a direction perpendicular to the plane of the paper. 5a~
Each optical member 5d has a plurality of self-cleaning lenses arranged in a one-dimensional direction.
a to 5d focus on measurement surfaces 2a, 1b, 1a, 2b, respectively. Reference numerals 6a to 6d refer to field stops disposed near positions conjugate with the respective measurement surfaces through the optical members 5a to 6d, and 7a to 7d guide the light beams that have passed through the respective field stops 6a to 6d to light receivers 8a to 8d. It is a light guide for shining light.

Optical member 5a and field stop 6 in this embodiment
a, the light guide 7a, and the light receiver 8a constitute a part of the detection means 9a. Other optical member 5b
~5d, field diaphragm 6b~6d, light guide 7b
7d and the light receivers 8b to 8d also constitute a part of the detection means 9b, 9c, and 9d, respectively.

In this embodiment, the reticle upper surface 1a, the reticle lower surface 1b, the pellicle upper surface 2a, and the pellicle lower surface 2b.
are each a measurement plane.

In this embodiment, four light beams may be used to make the light beams incident on each measurement surface and scan them.

FIG. 1B is a perspective view of a portion of FIG. 1A;
This figure shows a state in which the light beams 3 and 4 of FIG. 1A scan the measurement surface.

Further, FIG. 1C is a schematic diagram when viewed from the direction of arrow 10 in FIG. 1B.

In this embodiment, as shown in FIGS. 1B and 1C, when any two planes are selected from among the plurality of planes formed by the light beams scanning each measurement surface,
The light beam is made incident on the measurement surface and scanned so that the intersection line l formed by these two planes does not intersect any of the measurement surfaces.

In the embodiment shown in FIG. 1A, since the light beam 3 scans the pellicle upper surface 2a and the reticle lower surface 1b, the planes formed by the light beams scanning the pellicle upper surface 2a and the reticle lower surface 1b are the same.

Also, the light beam 4 is similar to the light beam 3, and since it scans the pellicle lower surface 2b and the reticle upper surface 1a, the planes formed by the light beams scanning the pellicle lower surface 2b and the reticle upper surface 1a are the same.

Therefore, in this example, there are two planes in total (when four light beams are used, there are four planes).The intersection line l formed by these two planes is the first plane. As shown in Figure C, it is made so that it does not intersect with any measurement plane.

Next, regarding the operation of this embodiment, Fig. 1 A, B, and C.
Explain using.

Now, suppose that a foreign object P such as dust exists at a position on the measurement surface 2a. Then, when the light beam 3 hits the foreign object P, the foreign object generates isotropically scattered light. At this time, since the detection means 9a is focused on the measurement surface 2a, the optical member 5a efficiently condenses the scattered light flux. As a result, the output from the light receiver 8a increases.

On the other hand, the other detection means 9b, 9c, and 9d have field stops 6b, 6c, and 6d arranged near the conjugate positions of the respective measurement surfaces 1b, 1a, and 2b, so that the detection means 9b, 9c, and 9d are free from the foreign matter P on the measurement surface 2a. The scattered light flux is field aperture 6
b, 6c, and 6d. As a result, the outputs from the light receivers 8b, 8c, and 8d do not change.

In this embodiment, the four light receivers 8a to 8a at this time are
The presence of foreign matter on the measurement surface is detected using the output signal from 8d, and the size of the foreign matter is determined at the same time by measuring the magnitude of the output signals from the light receivers 8a to 8d.

Furthermore, by using a plurality of detection means, the presence of foreign matter can be detected at high speed.

On the other hand, in FIG. 3A, similarly to the embodiment shown in FIG. 1C, the light beam 3 scans the pellicle top surface 2a and the reticle back surface 1b, the light beam 4 scans the pellicle bottom surface 2b and the reticle surface 1a, and the detection means 31a is arranged to detect scattered light from the pellicle top surface 2a, but when a plurality of light beams are incident on the measurement surface, the difference from this embodiment is that the pellicle top surface 2
The intersection line l formed by two planes, the plane formed by the light beam scanning a and the plane formed by the light beam scanning the reticle surface 1a, is 1 of the measurement surface.
The problem is that it intersects with the upper surface 2a of the pellicle.

In this case, as shown in FIG. 3A, the light beam 4 is incident on the pellicle top surface _2a , and as shown in FIG. occurs, and depending on these two cases, the pellicle top surface 2a
There is uneven illumination.

Generally, the intensity of scattered light generated by dust present on a measurement surface is proportional to the size of the dust. Therefore, in many cases, the size of dust can be determined to some extent by measuring the size of the output signal from the detection means.

However, as mentioned above, if there is uneven illumination on the measurement surface, even if the size of the dust is the same, the output signal from the detection means will change depending on its location, making it difficult to accurately determine the size of the dust. It becomes difficult to do so.

Therefore, in this embodiment, when any two planes are selected from among the plurality of planes formed by the light beams scanning each measurement surface as shown in FIG. The light beam is incident on the measurement surface and scanned so that the line of intersection formed by the measurement surface does not intersect with any measurement surface.

As a result, the measurement surface 2a detected by the detection means 9a
This prevents the occurrence of uneven illuminance at the upper position, detects the surface where foreign matter such as dust is present, and makes it easy to simultaneously determine the size of the foreign matter based on the magnitude of the output signal from the detection means.

4 to 7 are schematic diagrams of portions of other embodiments of the present invention, each of which is similar to FIG. 1C.

In FIG. 4, the light beam 3 scanning the measurement surfaces 2a and 1b
When the intersection line l formed by two planes, the plane formed by be.

5 shows the case where the light beam 3 is vertically incident on the reticle 1, FIG. 6 shows the case where the detection means 9c vertically receives the scattered light from the reticle surface 1a scanned by the light beam 4, and FIG. 7 shows the case where the two light beams are incident on the reticle 1. 3 and 4 are incident on the pellicle upper surface 2a and the pellicle lower surface 2b so as to be parallel to each other and are scanned.

In each embodiment, each element is constructed so that the above-mentioned intersection line l does not intersect with any measurement surface.

In this embodiment, the above-mentioned intersection line l may exist anywhere as long as it does not intersect with the measurement surface.

(Effects of the Invention) According to the present invention, when any two planes are selected from among the plurality of planes formed by the light beams scanning each measurement surface, the intersection line formed by these two planes. By configuring each element so that the surface does not intersect with any measurement surface, it is possible to detect the measurement surface where a foreign object is present with high accuracy and in a short time, and the size of the foreign object can also be determined with high precision at the same time. It is possible to achieve a surface condition measuring device that can

[Brief explanation of the drawing]

FIG. 1A is a schematic diagram of an optical system according to an embodiment of the present invention, FIGS. 1B and C are each an explanatory diagram of a part of FIG. 1, and FIGS. 2A and B are each an illustration of a conventional embodiment. 3A and 3B are explanatory diagrams for comparing the configurations of the present invention, and FIGS. 4 to 7 are explanatory diagrams of parts of other embodiments of the present invention, respectively. In the figure, 1 is a reticle, 2a and 2b are the upper and lower surfaces of each pellicle, 3 and 4 are luminous fluxes, 9a, 9b, 9c, and 9d are detection means, 1 is an intersection line, and P is dust.

Claims (1)

[Claims] 1. Simultaneously illuminate the measurement surface with the first and second light beams, which are used to measure the surface condition of a plurality of laminated measurement surfaces, while making them incident on the measurement surface from different directions. While scanning, a line of intersection between a first plane defined by the incident direction of the first beam and the scanning direction and a second plane defined by the incident direction and the scanning direction of the second beam does not intersect the measurement surface. A surface condition measuring device characterized in that the relationship between the first and second light beams is set to .