JPH051812Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a surface foreign matter inspection device that can be used in vacuum process equipment such as vacuum equipment for semiconductor manufacturing.

BACKGROUND ART For example, in semiconductor manufacturing technology, it is important to observe and inspect foreign substances such as dust particles attached to the surface of a substrate such as a wafer from the viewpoint of improving yield.

Conventionally used methods for inspecting foreign matter on the surface of a substrate include a method that uses light such as a laser beam to detect the particle size of the foreign matter from the scattered light, and a method that uses a microscope or scanning electron microscope. There are methods of testing.

Among these, the light scattering method is widely used because it can be quickly inspected on the line, and among them, it has high detection sensitivity and can detect even the smallest particles.
A light source using a laser is used. Although these devices are commercially available as complete devices, it is necessary to add a separate inspection step during the manufacturing process, which results in a time penalty.

For this reason, there is a demand for incorporating a foreign matter inspection device into manufacturing equipment, and in particular, there is an increasing demand for in-line measurement by incorporating the foreign matter inspection device into a device with a special environment such as a vacuum process device. By the way, unlike conventional laser dust monitors that are used in the atmosphere, a vacuum window is always required when introducing a laser beam into a vacuum equipment, or when emitting light specularly reflected on a wafer out of a vacuum equipment. This causes a problem such as the reflected light at the vacuum window portion increasing the background, resulting in a decrease in detection sensitivity.

On the other hand, it is known to use a Brieuster window in order to suppress the reflected light of the laser beam as low as possible. However, the Brieuxta window is only effective at a specific angle of incidence, and even a slight deviation in the angle increases the reflectance. Also, it is effective only when the laser is polarized. Therefore, Brieuster windows are not suitable when it is necessary to scan the surface of a wafer or the like.

Additionally, it is possible to move the wafer along with the stage without scanning the laser, but moving the stage is impractical when considering incorporating it into an in-line device, and moving the stage also generates dust. It's scary and undesirable.

In order to solve these problems, we first proposed the use of glass with an anti-reflection coating for the vacuum window for introducing the laser beam and the vacuum window for guiding the laser beam, which makes it possible to incorporate it into in-line vacuum equipment. A practical surface foreign matter inspection device has been realized.

In this surface foreign matter inspection apparatus, as shown in FIG. 2 of the drawings, when a 4-inch wafer B in a vacuum container A is laser scanned by a laser scanner C through a vacuum window D for introducing laser beams, the wafer B is About 0.4% of the light specularly reflected at the end is reflected into the vacuum chamber A by the vacuum window E for guiding the laser beam, as shown by the arrow, and hits the inner wall of the vacuum chamber A. The light hitting the inner wall of the vacuum container A is diffusely reflected there and becomes a large stray light inside the vacuum container A. The factors that determine the background are the diffused reflection of the reflected light at the laser beam introducing vacuum window D and the laser beam leading vacuum window E, and the diffused reflection on the wafer B. Therefore, the background rises and becomes larger than the dust signal, making it impossible to measure the dust. As a result, it is actually possible to measure only about half or less of the wafer diameter.

By the way, in the semiconductor process, there is a strict standard that the number of dust particles per wafer is 10 or less, and unless the monitor can measure the entire surface of the wafer, it cannot be called a perfect in-process monitor.

Problems to be Solved by the Invention In the surface foreign matter inspection device shown in Figure 2, glass with an anti-reflection film is used for the vacuum window for introducing the laser beam and the vacuum window for guiding the laser beam. It has become possible to detect dust particles with a particle size of about 0.5 μm, but in this case it is not possible to scan the entire wafer surface. If an attempt was made to scan the entire surface of the wafer, the reflected light would hit the inner wall of the vacuum container as described above, raising the background and causing the problem that measurement would be impossible. Therefore, regardless of the size of the wafer, the area on the wafer surface that can be scanned is limited.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface foreign matter inspection device that can scan the entire area of an object to be inspected, solves the problem of reflected light, and can be used in a vacuum.

Means for Solving the Problems In order to achieve the above object, the surface foreign matter inspection device according to the present invention, which can be used in a vacuum, is equipped with an anti-reflection coating on a vacuum container containing an object to be inspected for foreign matter. A window for introducing a laser beam and a window for guiding a laser beam provided with an anti-reflection film that guides the laser beam specularly reflected on the object to be inspected in the vacuum container to the outside, A laser scanner that scans the surface of the object to be inspected in at least one direction with a laser beam introduced onto the surface is connected to the laser beam introducing window, and the laser beam is diffusely reflected by foreign matter on the object to be inspected. A detector is provided at a position where the laser beam leading window can be detected, and the laser beam leading window is provided with an outer side having a radius of curvature equal to the length from the laser scanner to the laser beam leading window through the surface of the object to be inspected in the container. It is characterized by being formed into a convex spherical shape.

Function: In the surface foreign matter inspection device of the present invention configured as described above, which can be used in a vacuum, the laser beam passes through the laser beam introduction window provided in the vacuum container and is introduced onto the surface of the object to be inspected inside the vacuum container. This laser beam scans the surface of the object to be inspected in the X and Y directions. In this case, the laser scanner can scan the surface of the object to be inspected inside the vacuum container in the X and Y directions or only in the X direction, and when scanning in both the X and Y directions, the object to be inspected does not move during measurement.
On the other hand, when scanning only in the X direction, the inspection can be carried out while sending the object to be inspected in the Y direction at an appropriate speed using an in-line conveyance system.
The light beam specularly reflected on the surface of the object to be inspected is perpendicularly incident on the window for guiding the laser beam, and approximately 0.4% of the reflected light rays reflected by the window for guiding the laser beam all pass through the same path and reach the surface of the object to be inspected. will return to.
If any foreign matter is present on the surface of the object to be inspected, the introduced laser beam will be specularly reflected on the object to be inspected and will be led out through the vacuum window for guiding the laser beam, as well as the foreign object. The portion of the laser beam that collides with the detector is diffusely reflected and enters the detector. Thereby, the detector detects foreign matter on the surface of the object to be inspected.
In this case, a series of foreign object inspection operations can be performed in-line.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIG. 1 of the drawings.

The drawing shows the main parts of the surface foreign matter inspection device according to the present invention, which is applied to detect foreign matter on a substrate in a vacuum device. 1 is a vacuum container, and this vacuum container 1 includes a movable table that can move in the Y direction. 2 is provided,
A substrate holder 3 is mounted on the movable table 2, and a substrate 4, which is an object to be inspected, is mounted on the substrate holder 3. The vacuum container 1 has a laser beam introducing opening 5 at a position where the laser beam can be introduced into the substrate 4 at a predetermined incident angle, and a laser beam guiding port 5 at a position where the laser beam incident on the substrate 4 is specularly reflected and proceeds. It is equipped with an opening part 6. A vacuum window 7 is hermetically installed in the laser beam introduction opening 5, and a spherical vacuum window 8 convex to the outside is hermetically installed in the laser beam exit opening 6. These vacuum windows 7, 8 are provided with anti-reflection coatings. Reference numeral 9 denotes a laser scanner attached to the vacuum port 5 for introducing the laser beam, and includes a scanner 9a and a scanner mirror 9b for scanning the laser beam from the laser light source 10 on the substrate 4 in the X direction.

A detector 11, which may be a photomultiplier tube, is placed in the vacuum container at a predetermined angle with respect to a plane passing through the vacuum window 7 at the laser beam introduction port 5 and the vacuum window 8 at the laser beam exit port 6. It is attached to 1. Any suitable type of detector 11 may be used, the output of which is connected to, for example, a computer device (not shown).

An outwardly convex spherical vacuum window 8 that is sealed in the laser beam guiding port 6 has a radius of curvature that is substantially equal to the distance from the scanner mirror 9b to the vacuum window 8 passing over the substrate 4. There is.

In the operation of the illustrated device configured in this way,
First, the laser beam generated by the laser beam source 10 is scanned by the scanner 9a, and is introduced from the scanner mirror 9b through the vacuum window 7 in the laser beam introduction opening 5 onto the substrate 4 on the movable table 2. Scan in the direction. If there is no foreign matter on the substrate 4 scanned by the laser beam, the laser beam is specularly reflected by the substrate 4 and exits the vacuum chamber 1 through the vacuum window 8 in the laser beam outlet 6. If there is a foreign object on the substrate, the part of the laser beam that collides with the foreign object will be scattered, and this scattered light will be sent to the detector 11.
In this way, foreign substances on the substrate can be detected.

In the illustrated embodiment, the detector 11 may be located at any position as long as it can detect light diffusely reflected by foreign matter on the substrate. Well, Sukiyana 9a
It is recognized that the scanning operation by and the movement of the substrate in the Y direction should be performed in synchronization. Further, in the illustrated embodiment, the laser scanner 9 scans the laser beam only in the X direction and inspects the substrate while moving it in the Y direction, but it is of course configured to scan in both the X and Y directions. However, the board may be kept stationary during the inspection.

Effects of the Invention As explained above, according to the present invention, a laser beam introducing window provided with an anti-reflection film is provided on a vacuum container containing an object to be inspected for foreign substances, and and a laser beam emitting window equipped with an anti-reflection film to guide the specularly reflected laser beam to the outside. A laser scanner that scans in at least one direction is connected to the laser beam introducing window, a detector is provided at a position where it can detect the laser beam diffusely reflected by foreign matter on the object to be inspected, and the laser beam guiding window is formed into an outwardly convex spherical shape with a radius of curvature equal to the length from the laser scanner to the laser beam guiding window through the surface of the object to be inspected in the container, so that the anti-reflection coating is The effect can reduce reflected light from 4% to 0.4%,
Not only can the minimum detectable particle size of dust be reduced from 2μm to 0.5μm, but the laser beam introduced onto the object to be inspected through the laser beam introduction window is mirror-reflected on the object to be inspected, and then all of the laser beams are passed through the laser beam extraction window. The reflected light all returns through the same path or an inner path, and therefore the entire surface of the object to be inspected can be scanned, making it possible to detect foreign substances on the entire surface of the object. This allows the device according to the invention to be easily integrated into in-line vacuum process equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view showing a conventional example. In the figure, 1... vacuum container, 2... movable table,
4...Substrate, 5...Laser beam introduction opening, 6...
...Laser beam extraction port, 7, 8...Vacuum window, 9
...Laser scanner, 9a...Scaner, 9b...
...Scanner mirror, 10...Laser beam, 11...
…Detector.

Claims (1)

[Scope of utility model registration request] A vacuum container containing an object to be inspected for foreign substances is provided with a laser beam introduction window equipped with an anti-reflection film and an anti-reflection film for directing the laser beam specularly reflected on the object to be inspected in the vacuum container to the outside. a laser beam guiding window, and a laser scanner that scans the laser beam introduced onto the surface of the object to be inspected in at least one direction on the surface of the object to be inspected in the laser beam introducing window; A detector is provided in a position where the laser beam diffusely reflected by a foreign substance on the object to be inspected can be detected, and the window for guiding the laser beam is connected from the laser scanner through the surface of the object to be inspected in the container. A surface foreign matter inspection device usable in a vacuum, characterized in that it is formed into an outwardly convex spherical shape with a radius of curvature equal to the length up to the laser beam guiding window.