JPH0797083B2 - Reticle inspection method - Google Patents

Description

The present invention relates to a reticle inspection method, and more particularly, to a reticle inspection method for detecting foreign matter in a pellicle including a reticle and determining whether or not the reticle can be used. In order to increase the production throughput, a reticle containing a pattern without a fatal defect, an origin mark, and a rotation reference mark is mounted on a table, and the reticle is irradiated with the laser beam. By moving relative to the reticle, the entire surface of the reticle is scanned, the reflected light from the reticle is received and converted into an electric signal, and the position where the laser light is irradiated and the abnormal electric signal are detected. Create reticle foreign object coordinate data corresponding to the foreign object on the reticle, and detect the positions of the origin mark and the rotation reference mark to create those coordinate data. Then, coordinate conversion is performed so that the origin mark is the origin and the rotation reference mark is on the coordinate axis to create first-time reticle foreign matter coordinate data. Then, when the reticle is used, the first-time reticle foreign matter coordinate data is The reticle inspection for determining whether or not the reticle can be used by creating the reticle foreign matter coordinate data to be inspected in the same manner as the creation and comparing the reticle foreign matter coordinate data to be inspected with the initial reticle foreign matter coordinate data to check the difference According to the method.

[Industrial application field]

The present invention relates to a reticle inspection method, and more particularly to a reticle inspection method that detects foreign matter in a pellicle including a reticle and determines whether or not the reticle can be used.

In the semiconductor wafer process, it is desired to reduce the waiting time and increase the production throughput. Therefore, when using a reticle that is an original plate for transferring a pattern onto a semiconductor wafer, it is required to shorten the time for confirming whether or not the reticle can be used.

[Conventional technology]

FIG. 5 is an explanatory view of a pellicle including a reticle, (a),
(B) is a perspective view and a sectional view, respectively, 1 is a reticle, 13 is a quartz plate, 2 is a pellicle, and 21 is a frame. Reticle 1
The pattern is usually made of chrome, and is covered with a pellicle 2 which is a transparent protective film so as to prevent scratches and dust from adhering during use.

Nevertheless, as the storage period, the number of movements, and the number of times of use increase, foreign matter is generated inside the pellicle, and it reaches the reticle 1 or the quartz plate 13 or moves to other places. This causes defects in the pattern transferred to the semiconductor wafer. The surface to which such foreign matter adheres includes the upper and lower surfaces of the quartz plate on which the reticle is formed, the upper pellicle surface, the lower pellicle surface, etc.
A major obstacle to use in particular is foreign matter attached to the upper surface of the quartz plate.

Usually, when using a reticle, first attach this reticle to an exposure device, deposit chromium, apply a resist to a quartz plate, perform pattern transfer, and perform development etching processing. It is used after confirming that the defect has not changed since the last time it was used.

Although this method is excellent in reliability, it has a drawback that it requires an inspection time of 4 hours or more each time it is used, and the waiting time of the wafer process is long.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for determining whether or not a reticle to be used can be used in a short time.

[Means for Solving the Problems]

FIG. 1 is a diagram for explaining a reticle inspection method of the present invention, and FIG. 2 is a diagram for explaining a reticle inspection device.

The above problems are the pattern and origin mark without fatal defects.
The reticle 1 including the 11 and the rotation reference mark 12 is mounted on the table 3, the laser beam is applied to the reticle 1, and the laser beam is moved relative to the table 3 to cause the reticle 1 to move.
The entire surface of the reticle is scanned, the reflected light from the reticle 1 is received and converted into an electric signal, and the coordinates of the reticle foreign matter corresponding to the foreign matter of the reticle 1 are detected from the position where the laser light is irradiated and the abnormal electric signal. Data is created, and the coordinates of the origin mark 11 and the rotation reference mark 12 are detected to create their coordinate data. The origin mark 11 is the origin and the rotation reference mark 12 is on the coordinate axis. The conversion is performed to create the initial reticle foreign matter coordinate data, and when the reticle 1 is used, the inspected reticle foreign matter coordinate data is created in the same manner as the initial reticle foreign matter coordinate data is created, and the inspected reticle is created. The foreign matter coordinate data is compared with the first-time reticle foreign matter coordinate data to check the difference to determine whether the reticle 1 can be used or not by a reticle inspection method. .

[Action]

In the present invention, the initial reticle foreign matter coordinate data of the reticle is created in advance, and before using the reticle, the inspected reticle foreign matter coordinate data is created in the same procedure as when the initial reticle foreign matter coordinate data is created. Then, it is determined whether or not the reticle can be used by comparing the reticle foreign matter coordinate data to be inspected with the initial reticle foreign matter coordinate data. By doing so, it is not necessary to perform the transfer development processing of the pattern which has been conventionally performed for comparison, and the confirmation time can be significantly shortened.

Further, in order to accurately compare the reticle foreign matter coordinate data to be inspected with the initial reticle foreign matter coordinate data, the origin mark 11 and the rotation reference mark 12 are formed on the reticle, and when the reticle is mounted on the table 3, the origin mark 11 is formed. Even if the rotation reference mark 12 and the rotation reference mark 12 are not on the coordinate axis and the origin of the XY coordinates fixed on the base 3, for example, the origin mark 11 is on the coordinate origin and the rotation reference mark 12 is on the coordinate axis by coordinate conversion. I have to. Since the initial reticle foreign matter coordinate data and the inspected reticle foreign matter coordinate data have been subjected to such coordinate conversion, the overlay accuracy is high and the difference between the initial reticle foreign matter coordinate data and the inspected reticle foreign matter coordinate data is high. It can be detected accurately.

〔Example〕

FIG. 1 is a diagram for explaining the reticle inspection method of the present invention, FIG. 2 is a diagram for explaining a reticle inspection device for performing the reticle inspection of the present invention, and FIGS. 3 (a) to 3 (c). 4A to 4C are diagrams for explaining the procedure for creating the initial reticle foreign matter coordinate data, and FIGS. 4A to 4C are diagrams for explaining the procedure for creating the inspected reticle foreign matter coordinate data. An example of inspection of the reticle 1 surrounded by the pellicle 2 as shown in FIG. 5 will be described with reference to FIG.

See FIG. 2. FIG. 2 is a view for explaining the inspection apparatus for performing the reticle inspection of the present invention, where 1 is a reticle, 2 is a pellicle, 3 is a table, 4
Is a laser, 5 is a light receiving unit, 6 is a signal processing unit, 71 is a memory I, 72 is a memory II, 8 is a control unit, 9 is a comparison and determination unit, and 10 is an XY drive unit.

The reticle 1 surrounded by the pellicle 2 is mounted on the table 3.
The table 3 is driven in the X direction and the Y direction by the XY driving unit 10.

The surface of the reticle on which the pattern is formed is irradiated by the laser 4, and the reflected light is received by the light receiving unit 5. If there is no foreign matter on the surface where the reticle pattern is formed, almost no light is incident on the light receiving section 5, but if there is a foreign matter, the laser light is diffusely reflected and light corresponding to the size of the foreign matter is incident on the light receiving section 5. To do.

The laser light drives the XY drive unit 10 to scan the entire surface on which the reticle is formed.

The light receiving unit 5 converts light into an electric signal and sends it to the signal processing unit 6. The signal processing unit 6 creates reticle foreign matter coordinate data corresponding to the reticle foreign matter from the abnormal electrical signal and the data of the position coordinates on the table 3 where the laser light is irradiated. The positions of the origin mark and the rotation reference mark are detected by, for example, a microscope whose positional relationship with the table 3 is predetermined, and the positional information is sent to the signal processing unit 6 to create coordinate data. The signal processing unit 6 processes the data and sends it to the memory I (71) or the memory II (72).

The comparison and measurement unit 9 compares the data and determines whether or not the reticle can be used.

The control unit 8 controls each unit so as to perform a series of work in a fixed procedure.

See FIG. 1. FIG. 1 is a diagram for explaining the reticle inspection method of the present invention.

First, the first reticle 1 on which the origin mark 11 and the rotation reference mark 12 are formed without including a fatal defect is mounted on the table 3.

The table 4 is driven by the XY drive unit 10 while irradiating the surface on which the reticle pattern is formed with the laser 4, and the laser 4 scans the entire surface of the reticle 1.

The reflected light is sequentially captured by the light receiving unit 5 and converted into an electric signal. If there is no foreign substance, almost no reflected light enters the light receiving unit 5, but if there is a foreign substance, the light diffusely reflected from the light receiving unit 5
And an abnormal electrical signal is generated. Reticle particle coordinate data is created from the electric signal and the data of the position coordinate on the table 3 irradiated with the laser beam. The origin mark 11 and the rotation reference mark 12 are detected by a microscope whose positional relationship with the table 3 is determined in advance, and the origin mark coordinate data and the rotation reference mark coordinate data are created from the information. Next, coordinate conversion processing is performed so that the position of the origin mark 11 is the origin of the coordinates and the position of the rotation reference mark 12 is on the coordinate axis, and the initial reticle foreign substance coordinate data is created. The initial reticle foreign matter coordinate data is stored in the memory I.

Next, when using this reticle, inspect it before using. Therefore, the reticle foreign matter coordinate data to be inspected is created in the same manner as when the initial reticle foreign matter coordinate data is created. The data is stored in the memory II.

The inspected reticle foreign matter coordinate data extracted from the memory II is compared with the initial reticle foreign matter coordinate data extracted from the memory I. If there is no difference, the reticle is determined to be usable, and if there is a difference, the reticle is determined to be unusable.

FIGS. 3 (a) to 3 (c) are views for explaining the procedure for creating the initial reticle foreign matter coordinate data from the reticle foreign matter coordinate data.

See FIG. 3 (a). This reticle has an origin mark 11 and a rotation reference mark 12 and foreign matter 31, 32, but these foreign matter are not fatal defects and the reticle is possible. is there.

When this reticle is mounted on the base 3, the origin mark 11 does not always coincide with the origin of the XY coordinates of the base 3 and the origin mark 11
The direction connecting 11 and the rotation reference mark 12 also does not coincide with the X-axis direction of the base 3. Origin mark viewed from the XY coordinate system of the stand 3
11, the coordinates of the rotation reference mark 12 are A (x ₀ , y ₀ ), B (x ₁ , y ₁ ).
And

See FIG. 3 (b) Next, the coordinates are moved parallel to the X axis and further parallel to the Y axis to bring the origin to the origin mark 11.

If the new coordinate system ^X * -Y ^* system and the coordinates of the origin mark 11 and the rotational reference mark 12 ^{A * (0,0), B *} (x 1 *,
y ₁ ^* ) and the relationship between the X ^* -Y ^* coordinate system and the XY coordinate system is as follows.

x ^* = x−x ₀ y ^* = y−y _{0 The} direction connecting the origin mark 11 and the rotation reference mark 12 forms an angle θ with the X ^* axis.

See Fig. 3 (c). Next, rotate the coordinates around the origin of the X ^* -Y ^* system to move X ^**.
-Convert the coordinates to the Y ^** system so that the rotation reference mark 12 is on the X ^** axis. Origin mark 11 and rotation reference mark 12
The coordinates are A ^** (0,0), B ^** (x ₁ ^** , 0), and X
The relationship between the ^** -Y ^** coordinate system and the X ^* -Y ^* coordinate system is as follows.

x ^** = cos θ · x ^* + sin θ · y ^* y ^** = -sin θ · x ^* + cos θ · y ^* Reticle foreign matter The first conversion of the reticle foreign matter is performed by applying the coordinate conversion described above to the coordinate data. Get coordinate data.

FIGS. 4 (a) to 4 (c) are diagrams for explaining the procedure for creating the reticle foreign matter coordinate data to be inspected from the reticle foreign matter coordinate data. The procedure is the procedure for creating the initial reticle foreign matter coordinate data. Is the same as.

See FIG. 4 (a). The reticle to be inspected has an origin mark 11 and a rotation reference mark 12, and foreign matter 33, 34, and 35 are present.

When this reticle is mounted on the base 3, the coordinates of the origin mark 11 and the rotation reference mark 12 viewed from the XY coordinate system of the base 3 are set to C (x
₂ , y ₂ ), D (x ₃ , y ₃ ).

See FIG. 4 (b) Next, the coordinates are moved parallel to the X axis and further parallel to the Y axis to bring the origin to the origin mark 11.

If the new coordinate system ^X * -Y ^* system and the coordinates of the origin mark 11 and the rotational reference mark 12 is ^{C * (0,0), D *} (x 3 *,
y ₃ ^* ) and the relationship between the X ^* -Y ^* coordinate system and the XY coordinate system is as follows.

x ^* = x−x ₂ y ^* = y−y _{2 The} direction connecting the origin mark 11 and the rotation reference mark 12 forms an angle ψ with respect to the X ^* axis.

See Fig. 4 (c). Next, rotate the coordinates around the origin of the X ^* -Y ^* system to move X ^**.
-Convert the coordinates to the Y ^** system so that the rotation reference mark 12 is on the X ^** axis. Origin mark 11 and rotation reference mark 12
The coordinates are C ^** (0,0), D ^** (x ₃ ^** , 0), and X is
The relationship between the ^** -Y ^** coordinate system and the X ^* -Y ^* coordinate system is as follows.

x ^** = cos ψ ・ x ^* + sin ψ ・ y ^* y ^** =-sin ψ ・ x ^* + cos ψ ・ y ^* reticle The reticle to be inspected by performing the above-mentioned coordinate conversion on the foreign particle coordinate data. Obtain foreign object coordinate data.

Now, when comparing this reticle foreign matter coordinate data with the initial reticle foreign matter coordinate data, the origin mark 11 and the rotation reference mark 12 are overlapped, and the foreign matter 31 and the foreign matter 33, and the foreign matter 32 and the foreign matter 34 are found to be different. However, the foreign matter 35 does not match the first-time reticle foreign matter coordinate data, and this reticle is determined to be unusable.

Even if the foreign matter position in the inspected reticle foreign matter coordinate data overlaps with the foreign matter position in the initial reticle foreign matter coordinate data, if the foreign matter in the inspected reticle foreign matter coordinate data is larger, this reticle It is determined that it cannot be used.

Further, the foreign matter adhering to the lower surface of the quartz plate 13, the upper pellicle surface, and the lower pellicle surface is also focused and irradiated with laser light, and the first foreign matter coordinate data and the foreign matter to be inspected in the same manner as described above. A more complete inspection can be performed by creating coordinate data and adding an inspection for comparing and comparing them.

It should be noted that, in the above, when the reticle foreign matter coordinate data to be inspected does not match the initial reticle foreign matter coordinate data, it was determined to be unusable, but the criterion is slightly relaxed to allow a difference that does not result in a fatal defect. You can also do it.

In this way, after scanning the surface of the reticle on which the reticle pattern is formed with laser light and capturing the image,
Since only data processing is required, complicated steps such as conventional pattern transfer and development etching processing can be omitted, and the reticle inspection time can be greatly reduced.

〔The invention's effect〕

As described above, according to the present invention, the waiting time in the wafer process using the reticle can be significantly shortened, which can contribute to the improvement in throughput.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a reticle inspection method of the present invention, FIG. 2 is a diagram for explaining a reticle inspection device, FIG. 3 is a procedure for creating initial reticle foreign substance coordinate data, and FIG. 4 is an object to be inspected. Procedure for creating reticle foreign matter coordinate data, FIG. 5 is an explanatory diagram of a pellicle including a reticle. In the figure, 1 is a reticle, 11 is an origin mark, 12 is a rotation reference mark, 13 is a quartz plate, 2 is a pellicle, 21 is a frame, 3 is a stand, 31 to 35 are foreign matters, 4 is a laser, 5 is a light receiving part, 6 is a signal processing unit, 71 is a memory I, 72 is a memory II, 8 is a control unit, 9 is a comparison and determination unit, and 10 is an XY drive unit.

Claims (1)

[Claims] 1. A reticle (1) including a pattern without a fatal defect, an origin mark (11) and a rotation reference mark (12) is mounted on a table (3), and a laser beam is applied to the reticle (1). Then, the laser beam is moved relative to the table (3) so that the entire surface of the reticle (1) is scanned, and the reflected light from the reticle (1) is received and converted into an electrical signal. The reticle foreign substance coordinate data corresponding to the foreign substance on the reticle (1) is created from the converted position of the laser beam and the abnormal electric signal, and the origin mark (11) and the rotation reference mark (12) are generated. The coordinates of the reticle foreign matter are created by detecting the position of the reticle and creating their coordinate data. The origin mark (11) is the origin and the rotation reference mark (12) is on the coordinate axis. , Then, when using the reticle (1) Then, the reticle foreign matter coordinate data to be inspected is created in the same manner as the initial reticle foreign matter coordinate data, and the reticle foreign matter coordinate data is compared with the first reticle foreign matter coordinate data to check the reticle ( A method for inspecting a reticle, which comprises determining whether or not the use of 1) is possible.