JPH0384441A - Inspection method for reticle - Google Patents

Abstract

PURPOSE:To decide whether or not the reticle 1 can be used in a short time by generating initial-time reticle foreign matter coordinate data previously, and generating and comparing inspected reticle foreign matter coordinate data by a similar procedure before the reticle is used. CONSTITUTION:The reticle 1 which has a pattern having no fatal flaw, an origin mark 11, and a rotation reference mark 12 is placed on a base 3 and its entire surface is irradiated by a laser beam 4. A light receiving part 5 converts reflected light into an electric signal and a signal processing part 6 generates reticle foreign matter coordinate data corresponding to foreign bodies 31 and 32 and coordinate data on the marks 11 and 12 from the position irradiated with the laser beam and an abnormal electric signal, performs coordinate transformation so that the mark 11 is at the origin and the mark 12 is on a coordinate axis, and generates the initial-time reticle foreign matter coordinate data. Then when the reticle is used, the inspected reticle foreign matter coordinate data is generated similarly and a comparison control part 9 compares the inspected foreign matter coordinate data with the initial-time reticle foreign matter coordinate data to check the difference, thereby deciding whether or not the reticle 1 can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a reticle inspection method, and particularly to a reticle inspection method for detecting foreign matter in a pellicle including a reticle to determine whether or not the reticle can be used.

The purpose is to reduce waiting time in semiconductor wafer processing and increase production throughput.

A reticle containing a pattern with no fatal defects, an origin mark, and a rotation reference mark is mounted on a stand, the reticle is irradiated with a laser beam, and the #f laser beam is moved relative to the stand. Make sure to scan the entire surface of the reticle,
Receives reflected light from the reticle and converts it into an electrical signal,
Create reticle foreign object coordinate data corresponding to the foreign object on the reticle from the position where the laser beam is irradiated and the abnormal electrical signal, and also detect the positions of the origin mark and the rotation reference mark and create their coordinate data. Then, coordinate transformation is performed so that the origin mark is at the origin and the rotation reference mark is on the coordinate axis to create initial reticle foreign object coordinate data.Next, when using the reticle, the initial reticle foreign object coordinate data is Inspecting the reticle by creating inspected reticle foreign object coordinate data in the same manner as the creation, and comparing the inspected reticle foreign object coordinate data with the initial reticle foreign object coordinate data to check for differences to determine whether or not the reticle can be used. Configure by method.

[Industrial application field]

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 semiconductor wafer processing, it is desired to reduce waiting time and increase production throughput.

Therefore, when using a reticle as an original plate for pattern transfer to a semiconductor wafer, it is required to shorten the time required to confirm whether or not the reticle can be used.

[Conventional technology]

Figure 5 is an explanatory diagram of a pellicle including a reticle.

(a) and (b) are a perspective view and a sectional view, respectively,
1 is the reticle, 13 is the quartz plate, and 2 is the verital.

Reference numeral 21 represents a frame, and the pattern of the reticle I is usually made of chrome, and is covered with a pellicle 2, which is a transparent protective film, to prevent scratches or foreign matter such as dust from adhering during use.

Nevertheless, as the storage period, number of moves, and number of uses increases, foreign matter is generated inside the pellicle, and it may land on the reticle l or quartz plate 13 or move here and there. This causes defects in the pattern transferred to the semiconductor wafer. What is the surface to which such foreign matter adheres?

The top and bottom surfaces of the quartz plate on which the reticle is formed.

There is an upper pellicle surface, a lower pellicle surface, etc., but foreign matter adhering to the upper surface of the quartz plate poses a particularly large obstacle in use.

Normally, when using a reticle, the reticle is first mounted on an exposure device, a resist is applied to a chromium-coated quartz plate, a pattern is transferred, and a development and etching process is performed to remove common defects caused by the reticle. Before using the product, make sure that it has not changed since the last time you used it.

Although this method has excellent reliability, it requires an inspection time of 4 hours or more each time it is used, and has the disadvantage that the waiting time for wafer processing is long.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for quickly determining whether a reticle to be used is usable or not.

[Means to solve the problem]

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

To solve the above problem, a reticle 1 including a pattern without fatal defects, an origin mark 11, and a rotation reference mark 12 is mounted on a stand 3, a laser beam is irradiated onto the reticle 1, and the laser beam is directed onto the stand 3. The entire surface of the reticle 1 is scanned by moving the reticle 1 relatively, and the reflected light from the reticle 1 is received and converted into an electric signal, and the position where the laser beam is irradiated and the abnormal electric signal are detected. Reticle foreign object coordinate data corresponding to the foreign object on the reticle 1 is created, and the positions of the origin mark 11 and the rotation reference mark 12 are detected to create their coordinate data, and when the origin mark 11 is at the origin, the rotation Coordinate transformation is performed so that the reference mark 12 is on the coordinate axis to create initial reticle foreign object coordinate data.Next, when using the reticle 1, the reticle to be inspected is created in the same manner as the creation of the initial reticle foreign object coordinate data. Create foreign object coordinate data.

The problem is solved by a reticle inspection method that determines whether or not the reticle I can be used by comparing the inspected reticle foreign object coordinate data with the first reticle foreign object coordinate data and examining the difference.

[Effect]

In the present invention, initial reticle foreign object coordinate data of a reticle is created in advance, and before using the reticle, reticle foreign object coordinate data to be inspected is created using the same procedure as when creating the initial reticle foreign object coordinate data. Then, by comparing the foreign object coordinate data of the reticle to be inspected with the foreign object coordinate data of the first reticle, it is determined whether the reticle can be used. In this way, there is no need to perform pattern transfer and development processing and comparison, which has been done in the past, and the confirmation time can be significantly shortened.

Furthermore, in order to accurately compare the foreign object coordinate data of the reticle to be inspected and the foreign object coordinate data of the first reticle, an origin mark 11 and a rotation reference mark 12 are formed on the reticle, and when the reticle is mounted on the machine 3, the origin is aligned. For example, even if the rotation reference mark 11 and the rotation reference mark 12 are not on the coordinate axis with the origin of the X-Y coordinates fixed on the table 3, by performing coordinate transformation, the origin mark 11 can be placed on the origin of the coordinates and the rotation reference mark 12 can be placed on the coordinate axis. I try to come. Since the initial reticle foreign object coordinate data and the inspected reticle foreign object coordinate data have been subjected to such coordinate transformation, the accuracy of one overlay is high, and the difference between the initial reticle foreign object coordinate data and the inspected reticle foreign object coordinate data is It can be detected with high accuracy.

〔Example〕

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

Refer to Fig. 2 Fig. 2 is a diagram for explaining an inspection apparatus for performing reticle inspection of the present invention, where l is a reticle, 2 is a pellicle, and 3
is a stand, 4 is a laser, and 5 is a light receiving section.

6 is a signal processing section, 71 is a memory ■, and 72 is a memory ■.

8 represents a control section, 9 represents a comparison/determination section, and 10 represents an XY drive section.

A reticle 1 surrounded by a pellicle 2 is mounted on a stand 3.

The table 3 is driven in the X direction and the Y direction by an X-Y drive section 10.

A surface of the reticle on which a pattern is formed is irradiated with a laser 4 and one reflected light is received by a light receiving section 5. If there is no foreign object on the patterned surface of the reticle, almost no light will enter the light receiving section 5. However, if there is a foreign object, the laser beam will be diffusely reflected, and light will enter the light receiving section 5 according to the size of the foreign object. do.

The laser beam scans the entire surface of the reticle by driving the X-Y drive section 10.

The light receiving section 5 converts the light into an electrical signal and sends it to the signal processing section 6. The signal processing unit 6 creates reticle foreign object coordinate data corresponding to the reticle foreign object from the abnormal electrical signal and the position coordinate data on the table 3 irradiated with the laser beam. The positions of the origin mark and the rotation reference mark are detected using a microscope whose positional relationship with the table 3 is determined in advance, for example, and the position information is sent to the signal processing section 6 to create coordinate data. The signal processing unit 6 processes the data and stores it in the memory I (71).
Alternatively, it is sent to the memory IF (72).

The comparison/determination section 9 compares the data and determines whether or not the reticle can be used.

The control section 8 controls each section to perform a series of operations in a fixed procedure.

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

First, the initial reticle 1, which does not contain any fatal defects and has the origin mark 11 and rotation reference mark 12 formed thereon, is mounted on the stand 3.

The table 3 is driven by the X-Y drive section 10 while the laser 4 irradiates the surface on which the reticle pattern is formed, and the entire surface of the reticle 1 is scanned by the laser 4.

The reflected light is sequentially taken into the light receiving section 5 and converted into an electrical signal. If there is no foreign object, almost no reflected light will enter the light receiving section 5, but if there is a foreign object, the diffusely reflected light will enter the light receiving section 5.
An abnormal electrical signal is generated. Reticle foreign object coordinate data is created from the electric signal and the position coordinate data 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 origin mark coordinate data and rotation reference mark coordinate data are created from that information. , the position of the origin mark 11 is 1 at the origin of the coordinates.
Coordinate conversion processing is performed so that the position of the rotation reference mark 12 is on the coordinate axis, and initial reticle foreign object coordinate data is created. The initial reticle foreign object coordinate data is stored in memory I.

Next, when this reticle is used, it is inspected before use.For this purpose, foreign object coordinate data for the reticle to be inspected is created in the same manner as when the initial reticle foreign object coordinate data was created. Store the data in memory ■.

The foreign object coordinate data of the reticle to be inspected retrieved from the memory (2) is compared with the initial reticle foreign object coordinate data retrieved from the memory (2). 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. 3A to 3C are diagrams for explaining the procedure for creating initial reticle foreign object coordinate data from reticle foreign object coordinate data.

Refer to FIG. 3(a). This reticle has an origin mark 111, a rotation reference mark 12,
is formed, and there are also foreign substances 31 and 32, but these foreign substances are not fatal defects.

A reticle is possible.

When this reticle is mounted on the stand 3, the origin mark 11 does not necessarily coincide with the origin of the X-Y coordinates of the stand 3, and the direction connecting the origin mark 11 and the rotation reference mark 12 also coincides with the X-axis direction of the stand 3. does not match. Origin mark 11 as seen from the X-Y coordinate system of table 3. The coordinates of the rotation reference mark 12 are r A (X
l + ye) e B (Xl + 71).

Refer to 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 is the x”-y” system, the origin mark 11
The coordinates of the rotation reference mark 12 are A'' (0,0).

B"(Xl" + 3'l"), x"-y
``Coordinate system and.

The relationship with the X-Y coordinate system is as follows.

X Wings X-X.

)' -7-3'e What is the direction in which the origin mark 11 and the rotation reference mark 12 are connected?

It forms an angle θ with the X0 axis.

Refer to Figure 3 (C) Next, rotate the coordinates around the origin of the X"-Y" system and x"
The coordinates are converted to the -y- system so that the one-turn reference mark 12 is on the X0 axis. Origin mark 11 and rotation reference mark 1
The coordinates of 2 are A” (0,0).

B” (Xl “”, O) becomes X **
The relationship between the Y＊＊＊＊ system and the x''-y'' coordinate system is as follows.

x”=cos θ−x” +sin θ′y11
y "sx -3in θ*x*+COs θ°y" By performing the coordinate transformation described above on the reticle foreign matter coordinate data, initial reticle foreign matter coordinate data is obtained.

FIGS. 4(a) to 4(c) are diagrams for explaining the procedure for creating inspected reticle foreign object coordinate data from the reticle foreign object coordinate data, and the procedure is the procedure for creating the initial reticle foreign object coordinate data described above. It is similar to

Refer to Fig. 4(a) The reticle to be inspected has an origin mark 119 and a rotation reference mark 1.
2 is formed, and there are also foreign substances 33, 34, and 35.

When this reticle is mounted on the stand 3, the origin mark 11.2 as seen from the X-Y coordinate system of the stand 3. Let the coordinates of the rotation reference mark 12 be C(xz+yz) and D(xs, ys).

Refer to 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 is the X”-Y” system, the origin mark 11
The coordinates of the rotation reference mark 12 are C'' (0,0).

D” (Xs ” + Vs I), which is the X”-Y” coordinate system.

The relationship with the X-Y coordinate system is as follows.

X=X−X.

'!　　　　　　=3'　　)' What is the direction in which the origin mark 11 and the rotation reference mark 12 are connected?

It forms an angle ψ with respect to the X1 axis.

Refer to Figure 4 (C) Next, rotate the coordinates around the origin of the X"-Y1 system, and
The coordinates are converted to the "-Y- system so that the 2nd rotation reference mark 12 is on the X0 axis. The coordinates of the origin mark 11 and the rotation reference mark 12 are C" (0,0).

D” (X3 “”, O) becomes X 111
The relationship between the Y*1' coordinate system and the X"-Y" coordinate system is as follows.

x”acos ψ・x” 10 sin ψ, y 1y
"=-5in ψ*x"+cos ψ°y By performing the coordinate transformation described above on the reticle foreign object coordinate data, the reticle foreign object coordinate data to be inspected is obtained.

Now, when this inspected reticle foreign object coordinate data is compared with the initial reticle foreign object coordinate data, the origin mark 11 and the rotation reference mark 12 overlap, and the foreign object 31 and the foreign object 33. Foreign matter 32 and foreign matter 34 match and no difference is found, but foreign matter 35 does not match the initial reticle foreign matter coordinate data,
This reticle is determined to be unusable.

Furthermore, even if the position of the foreign object in the foreign object coordinate data of the reticle to be inspected overlaps with the position of the foreign object in the initial reticle foreign object coordinate data, if the foreign object in the foreign object coordinate data of the reticle to be inspected is larger, this reticle It is judged as unusable.

Furthermore, foreign matter attached to the lower surface, upper pellicle surface, and lower pellicle surface of the quartz plate 13 is irradiated with laser light with a focus on those surfaces, and the initial foreign matter coordinate data and the foreign matter to be inspected are processed in the same manner as described above. If you create coordinate data and add an inspection to compare and judge it.

A more complete inspection is possible.

Note that the above example shows a case where the inspected reticle foreign object coordinate data does not match the initial reticle foreign object coordinate data.

It was judged as unusable, but the criteria for judgment was slightly relaxed.

It is also possible to allow differences that do not amount to fatal defects.

By doing the above, after scanning the patterned surface of the reticle with the laser beam and capturing the image,
Since everything is done through data processing, the troublesome processes required in the past, such as actual pattern transfer, development and etching, can be omitted, and reticle inspection time can be significantly shortened.

〔Effect of the invention〕

As described above, according to the present invention, the waiting time in a wafer process using a reticle can be significantly reduced, contributing to an improvement in throughput.

[Brief explanation of drawings]

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. Figure 3 shows the procedure for creating initial reticle foreign object coordinate data. FIG. 4 shows the procedure for creating foreign object coordinate data on the reticle to be inspected. FIG. 5 is an explanatory diagram of a pellicle including a reticle. In fig. 1 is the reticle. 11 is the origin mark. 12 is a rotation reference mark. l3 is a quartz plate. 2 is pellicle. 21 is the frame. 3 is the stand. 31 to 35 are foreign substances. 4 is a laser. 5 is the light receiving section. 6 is a signal processing section. 71 is memory■. 72 is memory■. 8 is a control unit. 9 is a comparison and judgment section. 10 is the X-Y drive unit in August. Shima Guru 111 Object coordinate data's Boku Hirokon - No. 1 Map

Claims (1)

[Claims] A reticle (1) including a pattern without fatal defects, an origin mark (11) and a rotation reference mark (12) is mounted on a stand (3).
The reticle (1) is irradiated with a laser beam, and the entire surface of the reticle (1) is scanned by moving the laser beam relative to the stand (3). (1) Receives the reflected light from and converts it into an electrical signal,
Create reticle foreign object coordinate data corresponding to the foreign object on the reticle (1) from the position where the laser beam is irradiated and the abnormal electric signal, and also determine the positions of the origin mark (11) and the rotation reference mark (12). Detect and create their coordinate data, perform coordinate transformation so that the origin mark (11) is at the origin and the rotation reference mark (12) is on the coordinate axis to create initial reticle foreign object coordinate data, and then When using the reticle (1), create inspected reticle foreign object coordinate data in the same manner as the creation of the first reticle foreign object coordinate data, and compare the inspected reticle foreign object coordinate data with the first reticle foreign object coordinate data. A method for inspecting a reticle, characterized in that it is determined whether or not the reticle (1) can be used by examining the difference between the reticle and the reticle.