JPS603631A - Mask checking device - Google Patents

Abstract

PURPOSE:To enable detection of transferred images even of microscopic foreign matters by forming register marks in advance on the wafer or the like on which a test pattern is to be transferred, and registering the photographed image of a reticle using this mark. CONSTITUTION:A mobile stage 5 is stepwise moved with a driving member 6 and a coordinate position measuring meter 7 and the transfer region PA3 of an inverted reticle R3 is illuminated, and these operations are repeated to transfer the inverted pattern successively on a wafer W. Next, the right pattern of a reticle R2 to be checked is registered on this wafer W to transfer the pattern. When foreign matters have attached, they intercept the illumination light to cause an unexposed part on the reticle R2. The inverted pattern is thus overlaid on the right pattern and they are transferred to a positive resist layer 100. This wafer W is taken out and exposed, resulting in leaving the unexposed part as a residual protuberant resist P on the wafer W. As a result, the transferred image of microscopic foreign matters can be detected.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a method for detecting whether or not foreign matter is attached to a disk used in the process of transferring a circuit pattern onto a wafer in the production of integrated circuits. It concerns a method of testing whether

(Background of the Invention) As integrated circuit patterns become finer and more dense, reduction projection exposure apparatuses have come into widespread use in recent years.

In this type of apparatus, a pattern on a mask called a reticle is reduced to a size of 115 or 1/io and projected. For this reason, foreign matter such as dust on the reticle is also reduced, so small foreign matter is not transferred, but foreign matter that is larger than a certain value and has an optical density will be transferred onto the wafer during all printing of repeated exposures. There was a drawback that it could be transferred. In order to compensate for this shortcoming, in the old days, people used a microscope to observe resist images printed on sea urchins as a test to check whether any foreign matter had been transferred. However, with this method, a maximum of 2 to 2
This requires a very eye-tiring process that takes three hours, and it is possible that the transfer of foreign matter may be overlooked. To solve this problem, a device has recently been proposed that scans a laser spot on a reticle and detects scattered light to determine the presence and size of foreign objects. (For example, JP-A No. 58-62544)
This device shortens the inspection time, can perform automatic inspection, and can detect almost all foreign substances that have a size that may cause transfer. However, since the detection method used in this device has a high ability to distinguish between foreign objects and the chrome layer of the circuit pattern, conversely, if the foreign object adheres flatly to the reticle, and the area of the foreign object becomes thick enough to be transferred, it may be mistaken for a chrome layer. There is a possibility that the detection will be impossible due to being judged.

In addition, this method does not directly inspect the pattern transferred to the resist layer of the wafer, etc., and it is necessary to detect all foreign particles that are large enough to have a possibility of transfer, but are small enough to not affect the transfer. -Some disliked the fact that it detected even objects and required a reticle cleanliness that was stricter than necessary.

As an inspection method that is completely different from the above inspection methods,
A method has been considered in which a reticle to be inspected and a reticle whose light and dark areas are reversed are superimposed and transferred onto the same photosensitive material, and the presence or absence of a speckled pattern in the photosensitive material remaining after development is inspected. However, alignment accuracy between the latent image in the resist layer formed by the first exposure and the projected image of the reticle to be exposed the second time was insufficient. The reason for this is the variation in the alignment of the reticle with respect to the exposure device, and the position of the stage on which the sea urchin is placed.
This is because there is a drift etc. Therefore, if the alignment accuracy is poor between the 72nd exposure and the 1st monthly exposure, increase the exposure amount and widen the width of the double exposure at the edge of the image to improve the registration of the areas where the edges do not match. It is also conceivable to expose the photosensitive material to light so that there is an apparent positional shift, and then inspect the presence or absence of the remaining photosensitive material. However, if this is done, foreign matter adhering to the edge will be transferred and will be difficult to find during inspection, or will not be found at all.

(Objective of the Invention) The present invention solves these drawbacks, performs the relative positioning of the latent image formed by the fourth exposure method and the image to be exposed in the second time with high precision, and It is an object of the present invention to provide a method for inspecting the presence or absence of foreign matter on a mask by detecting even the transferred image of the foreign matter.

(Summary of the Invention) The present invention involves forming alignment marks (alignment marks) in advance on a wafer or the like onto which a pattern is to be transferred on a trial basis, and using these marks to form a projected image of a reticle (which may also be a mask). By performing alignment, a superimposed image of the reticle to be inspected and the inverted reticle is formed on a photosensitive material such as a wafer, and developed to form a speckled resist pattern on the wafer surface. Specifically, defects such as foreign matter adhering to the reticle to be inspected can be inspected by examining the photosensitive state.

(Example) Next, a first embodiment of the present invention will be described based on the drawings.

FIG. 1 is an overall perspective view of the main parts of a reduction projection type exposure apparatus suitable for carrying out the method of the present invention.

In FIG. 1, a mark reticle R1 used in the step of previously transferring only marks onto an object coated with resist is placed above the projection lens 1. As shown in FIG.

Specifically, as shown in a plan view in FIG. 2, the mark reticle R1 has two marks RMI and RM2 for reticle alignment formed therein.

Then, when an orthogonal coordinate system XY having the origin at the center O of the transfer area PAlO on the reticle R1 is determined, the mark RM1 is determined to be located on the Y line, and the mark RM2 is determined to be located on the X axis. In addition, this mark reticle R1 has three marks MX, MY, and Iv to be transferred onto the object.
Only the transfer area PAI is provided at the periphery within the transfer area PAI. Of these, the marks MY and Mθ are provided at two separate locations within the transfer area PAl so as to be located on a line parallel to the Y axis of the coordinate system XY. The mark MX is provided so as to be located on a line parallel to the Y-axis and perpendicular to the Y-axis. These three marks MX, MY, and Mθ all have a diagonal hatched lattice structure.

Now, the mark RMI of the mark reticle R1 is observed by the reticle alignment microscope 2, which is composed of a mirror 2a, an objective lens 2b, a half mirror 20, etc. arranged on the light source side (not shown above), and the mark RM2 is observed by the mirror 3a,
Observation is performed using a reticle alignment microscope 3 consisting of an objective lens 3b, a half mirror 30, and the like. In addition, the half mirror 2C13C uses the objective lenses 2b and 3b to direct the illumination light.
It is something that leads to. Now, these two microscopes 2.degree. 3 are each equipped with a reference for aligning the observed images of marks RMI and RM2. And reticle R
A reticle drive unit 4 for moving the reticle R1 in two' dimensions (including rotation) is provided for each of the two microscopes 2 and 3, and is positioned so that the optical axis l of the projection lens 1 passes through the center 0 of the reticle R1. It will be done.

On the other hand, a wafer W is normally fed directly under the projection lens 1, and a reticle pattern is projected onto the surface of the wafer W. This wafer W is placed on a two-dimensional movement stage 5, and is moved in the X direction of the orthogonal coordinate system xy and
It is possible to move in both directions. Further, the moving stage 5 is provided with a holder 5a which holds the wafer W by suction and is rotatable within the xy plane with respect to the moving stage 5. Further, the coordinate position measuring device 7 is set at a predetermined origin (
For example, the two-dimensional position of the moving stage 50 with respect to the axis e@A is measured. For example, this can be done using a laser interferometer,
The amount of movement of the moving stage 5 may be measured in the X direction and the X direction.

Two wafer alignment microscopes 8 and 9 are arranged around the projection lens 10. The wafer alignment microscope 8 (hereinafter referred to as X-W'AM8) is set so that its optical axis is parallel to the optical axis l of the projection lens 10, and its optical axis (or observation center) is set so that the optical axis l is parallel to the optical axis l of the projection lens 10. It is located so as to intersect the xyOX axis of the coordinate system, which is determined to pass through the origin.

～, Ueno Alignment Microscope 9 (hereinafter referred to as Y-WA
M9) is determined so that its optical axis is parallel to the optical axis l of the projection lens 1, and its optical axis (or observation center) is located so as to intersect the xyOy axis of the coordinate system. And 1. The X-WAM8 detects the position of the wafer W in the X direction by observing the mark on the wafer W.
-WAM9 observes the marks on the wafer W and
This is to detect the position of W in the X direction.

In addition, reticle alignment microscopes 2 and 3 and X-WAM
8. In addition to visual observation, Y-WAM9 vibrates the observation image of each mark and the slit relatively, and photoelectronically measures the displacement between the center of vibration (the above-mentioned reference or observation center) and the mark image. It also has photoelectron microscope functions for detecting images.

In particular, the X-WAM8 and Y-WAM9 vibrate the laser light spot minutely on the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface. It also has functions.

FIG. 3 is a plan view showing an example of the reticle R2 to be inspected on which the original pattern to be transferred to Ueno-W is formed.

The size of the transfer area PA2 of the reticle R2 to be inspected is the same as the large stone of the transfer area PA1 of the mark reticle R1.

Reticle mark RM in the same position as RM2],
.

RM2 is formed. In FIG. 3, the shaded area is the light-shielding part on which the layer L1 is deposited, and the other parts are made of glass so that the light can pass through the plate C. Note that the pattern in the transfer area PA2 will hereinafter be referred to as a normal rotation pattern for convenience.

On the other hand, FIG. 4 is a plan view of an inverted reticle R3 prepared for carrying out the method of the present invention. There is also a mark reticle R1 on the inverted reticle R3, and a similar reticle mark RM1 at the same position as the reticle to be inspected R2. RM2 is formed. The size of the transfer area PA3 is the size of the reticle to be inspected R.
The size of the transfer area PA2 of No. 2 is determined to be the same as the size of the transfer area PA2 of No. 2.

Furthermore, the pattern in the transfer area PA3 is similar to the pattern in the transfer area PA3.
It is formed in a one-to-one positional relationship with respect to the normal rotation pattern in Z, and in a complementary shape in which the light transmitting part and the light blocking part are reversed, that is, in a negative relationship.

In the present invention, the entire pattern of a reticle (mask) will also be referred to as a reticle (or mask).

Next, the steps of the first embodiment of the inspection method according to the present invention will be explained using FIGS. 5 to 7.

First, the wafer W is coated with a positive photosensitive material to form a uniform positive resist layer 100 on the surface, and then baked. Then, the wafer W is placed on the holder 5a of the exposure apparatus as shown in FIG. At this time, the wafer W is positioned and placed on the wafer holder 5a using a peripheral notch, that is, a flat. In this embodiment, the flat direction is positioned so as to match the moving direction of the moving stage 5 with respect to the χ axis.

On the other hand, the mark reticle R1 shown in FIG. 2 is positioned and arranged with respect to the exposure device as shown in FIG.

Therefore, the driving unit 6 is operated based on the measured values of the coordinate position measuring device 7, and the moving stage 5 is moved step by step in the x, y and x directions by a predetermined pitch, and the transfer area PA1 of the mark reticle R1 is repeatedly illuminated for a certain period of time. Figure 5 (a
) in mark reticle R1, mark MX, MY,
Only the luminous flux Lm from IViθ 1 is sent to the positive position on the wafer W.
The resist layer 100 is irradiated. As a result, reduced latent images of the marks MX, MY, and Mθ are formed on the positive resist layer 100.

Next, this wafer W is removed from the wafer holder 5a and the positive resist layer 100 is developed, as shown in FIG.
As shown in b), the resist in the latent image portions of the marks MX, MY, and Mθ is removed, and the marks MX are removed.

Mark A corresponding to MY and Mθ appears as a recess.

On the wafer W, the marks AX, AX, and Mθ correspond to the marks MX, MY, and Mθ, respectively, as shown in FIG.
AY and Aθ are formed for each transfer area. Of course, the marks AX, AY, and Aθ have a diagonal hatched lattice structure.

Next, take out the mark reticle R1 from the exposure device, and replace it with the inverted reticle R3 shown in FIG.
2 to position and set the exposure device.

On the other hand, the wafer W shown in FIG.
When using the OFPR series, etc., it is possible to maintain photosensitivity even after development, but when using a resist that loses photosensitivity after development, it is necessary to form a resist layer again on the wafer W shown in Figure 6. There is.

Now, while the wafer W is placed on the wafer holder 5a and vacuum-adsorbed, you may notice that the position of the wafer W relative to the exposure device is slightly shifted from the position when the mark reticle R1 was transferred. It's normal.

Then, transfer the wafers W to X-WAM8 and Y-WAM9.
to position it relative to the exposure device.

For details regarding this positioning method, please refer to JP-A-56-1
Since it is disclosed in No. 02823 and No. 57-80724, it will be briefly explained here. First, among the plural marks AY and Aθ formed on a specific line extending in the X direction parallel to the flat, , two marks AY on the peripheral side of the wafer W, or on both ends.

(or mark a) to detect the rotational error of the wafer W and the position in the X direction. To do this, the moving stage 5 is moved so that the mark AY at the left end of the wafer W matches the observation center of the Y-WAM 9 in the X direction. Thereafter, the moving stage 5 is moved in the X direction, and the mark Aθ at the right end on the wafer W is observed by the Y-WAM 9. From that position, the moving stage 5 is moved in the X direction until the mark Aθ coincides with the observation center of the Y-WAM 9 in the X direction.

At this time, from the mark AY on the moving stage 5 to the mark Aθ
The coordinate position measuring device 7 calculates the amount of movement in the X direction until
By detecting the rotation error of the wafer W with respect to the coordinate system xy. This rotational error has been corrected in advance by rotating the wafer holder 5a within a certain range, but even more precise rotational error correction is possible in Japanese Patent Laid-Open No. 57-8.
As disclosed in No. 0724, when stepping the moving stage 5 during exposure, a coordinate system rotated by a minute amount of rotation of the wafer W is set with respect to the coordinate system xy, and this coordinate system is This is done by positioning the moving stage 5 accordingly.

Now, when the amount of rotation of the wafer W with respect to the coordinate system xy is detected in this way, the left end mark AY on the wafer W is
Find the y-coordinate value when it coincides with the observation center in the X direction of AM9, and move a specific mark AX on the wafer W to X-X-
Match the observation center in the X direction of 4VA, and find the X coordinate value at that time. .

As a result, the positional relationship of the wafer W in the xyx directions with respect to the optical axis l of the projection lens 1 is determined accurately.

Then, in order to match the previously transferred marks AX, AY, and Aθ, the moving stage 5 is moved step by step using the drive unit 6 and the coordinate position measuring device 7 at the same pitch as when exposing the mark reticle R1, and then the inverted reticle is moved. R2 transcription region PA
3 is repeated, and the inverted pattern is sequentially transferred onto the wafer W. At this time, marks AX, A'Y, Aθ
is positioned around the projected image of the transfer area PA3, so that the marks AX, AY, and Aθ are not exposed. Figure 5 (•) shows one example of the exposure of the reversal pattern, in which the light flux Lm passing through the transparent part of the reversal reticle R2 is irradiated onto the positive resist layer 1oo, resulting in a reduced latency of the reversal pattern. An image is formed in the positive resist layer ioo.

In this step exposure of the reverse pattern, one transfer region on the wafer W where the marks AX, AY, and Aθ are provided in advance is not exposed to the reverse pattern.

Next, the normal rotation pattern of the reticle R2 to be inspected is superimposed and transferred onto the wafer W.

First, the inverted reticle R3 is taken out from the exposure device, and the reticle R2 to be inspected is positioned and set in the exposure device using the marks RMI and RM2. Therefore, at this point, the reticle R2 to be inspected is on the wafer W on the moving stage 5.
mark AX, AY, Aθ through the exposure equipment main body
This means that the position is indirectly aligned based on the .

Then, the moving stage 5 is moved to the same position as the step exposure position of the reversal pattern so that the projected image of the normal rotation pattern of the reticle to be inspected R2 is superimposed on the latent image of the reversal pattern of the reversal reticle R3 transferred earlier. Then, the process of repeatedly illuminating the transfer area PA2 of the reticle to be inspected R2 is repeated. In this case as well, the marks AX, AY, and Aθ are prevented from being exposed. Figure 5(d) shows the exposure at this time.
Shown below. 5 (C
), except for the portion irradiated with the light beam Lm, the light beam Lm is irradiated onto all other areas, and a reduced latent image of a normal rotation pattern is formed. However, if a foreign substance is attached, the foreign substance blocks the illumination light, and a dark area Dm corresponding to the foreign substance is generated in the luminous flux Lm as shown in FIG. 5(d). This dark area Dm does not form a photosensitive area in the positive resist layer 100. In other words, an unexposed portion is generated in the positive resist layer 100 due only to the foreign matter adhering to the reticle R2 to be inspected.

In this way, the reverse pattern and the normal pattern are superimposed on each other and transferred to the positive resist layer 100. At this time, only the normal rotation pattern of the reticle R2 to be inspected is transferred to the area on the Ueno W where the exposure of the inversion pattern was not performed. By the way, when transferring the normal rotation pattern onto the wafer W, it is not necessary to keep the wafer W in the wafer holder 5a, but after transferring the inversion pattern, it is removed and the reticle R2 to be inspected is set in the exposure device. , the wafer W may be placed on the wafer holder 5a again, and the wafer W may be positioned with respect to the projected image of the normal rotation pattern of the reticle R2 to be inspected, according to the above-described wafer W positioning method.

Further, as described above, it is not necessary to use the same exposure device as used for transferring the reverse pattern. However, if printing is performed using separate exposure devices, there may be differences in transfer distortion, including errors in projection magnification, between the exposure device used to transfer the reverse pattern and the exposure device used to transfer the normal pattern. It is desirable that the value is sufficiently small. When using separate exposure devices in this way, one device exposes the reversed pattern onto the sea urchin...W, and then the sea urchin...W is placed on the other device and the marks AX, AY, Air and Mark MR1
, MR2 may be used to position the wafer W and the reticle R2 to be inspected, and then the normal rotation pattern may be overprinted.

Next, when this wafer W is taken out from the exposure apparatus and the positive resist layer 100 is developed, the exposed portions are removed by the normal rotation pattern and the reverse pattern, and foreign matter is attached as shown in FIG. 5(e). The unexposed portions appear as residual resist P on the surface of the wafer W in a convex shape.

Now, as an example, on the surface of the wafer W after development, a seventh
A pattern group as shown in the figure is formed. Here, six representative transcription regions S are arranged in a matrix. -85
Only shown. It is assumed that only the normal pattern of the reticle to be inspected R2 is transferred to the transfer area So, and the normal pattern and the reverse pattern are superimposed and transferred to the other five areas 5l-S5. . The six regions so to S5 are defined in the orthogonal coordinate system 6β defined on the wafer W.
It is assumed that they are positioned at a constant pitch.

When inspecting the wafer W, the regions s1 to s5 are observed and it is confirmed that the remaining resists 1p15 and the remaining resists Nl-N5 are commonly present at the same position in each region. If there is no residual resist of the same shape at a common position, but there is residual resist at random positions, for example, there may be dust on the resist of the wafer W before exposure.
It is thought that fine resist particles were attached during the development process, and it can be determined that no foreign matter is attached to the corresponding position on the reticle R2 to be inspected.

Now, when it is confirmed that the resists appearing at the common positions in the areas S1 to S5 are the remaining resists P+ to Ps and N1 to N5, it is next determined whether there is a similar remaining resist at the corresponding position in the transfer area SO. Find out. In this case, in the normal rotation pattern of the area So, there is a residual resist) Pa at a common position with the residual resists P1 to P5, and the residual resist) N+ to N
No residual resist is observed at the same position as No. 5.

Therefore, the remaining registers) Po to P5 are the reticle R to be inspected.
It can be determined that the residual resist (Nl-N5) was formed by a foreign substance attached to the transparent part of the reversible reticle R3.

Therefore, finally, at the position in the reticle to be inspected R2 corresponding to the position where the remaining resist PO in the area QSo exists,
It can be determined that foreign matter is attached that affects the yield in one lithography process.

In this way, as an apparatus for inspecting the surface of the wafer W,
For example, as shown in FIG. 8, a light source 20 that illuminates the surface of the wafer W obliquely. Objective lens 21. An inspection device consisting of a television camera 22 (hereinafter referred to as ITV 22), a monitor television 23, and a processing device 24 can be used. This inspection device also includes a stage on which a wafer W is placed and moves two-dimensionally, as shown in FIG. 1, a coordinate position measuring device, and an X-WAM
Two alignment microscopes similar to the 8° Y-WAM9 are provided. This microscope has a projection lens 1, X-WAM8, Y-4VAM with respect to the optical axis of the objective lens 21.
They are arranged in the same positional relationship as 9.

Here, the observation range by the ITV 22 is determined to be a local part of the transfer area on the wafer W.

First, when inspecting the transfer area Sl, the stage is moved so that the optical axis of the alignment microscope (hereinafter referred to as an X microscope) in the y direction of the inspection apparatus coincides with the mark AYl. Then, when the optical axis and the mark AYI match (-), the optical axis of the X microscope and the objective A value corresponding to the distance between the lens 21 and the optical axis is preset.Furthermore, the stage is moved and the inspection device
Align the optical axis of the microscope (X microscope) with the mark AXl. At this time, the position measurement counter (X
The optical axis of the xJl mirror and the objective lens 21
Preset the value to be adjusted to the interval between. Through the above operations, the coordinate system αβ1 of the wafer W-H is associated with the movement coordinate system of the stage in a one-to-l relationship.

That is, when the stage is moved so that the contents of the X counter and the X counter both become zero, the sea urchin...W is positioned so that the optical axis of the objective lens 21 passes through the origin of the coordinate system αβ1. Therefore, the stage is moved according to the coordinate system αβ1 so that the observation range of the ITV 22 scans the transfer area SL in steps. Residual regimen in the observation range of ITV22) P+
, Nt, the level of the image signal changes, so the processing device 24 detects the level change, and
The contents of the X counter and X counter at that time are stored as the coordinate values of the remaining registers Pi and N1.

The above operation is similarly repeated for the transfer areas 82 to S5. Then, a common coordinate value within the error range is searched for in the five transfer areas S+ -Ss.

As a result, the coordinate values (xp,
yp) and residual register) Nl-N5 coordinate value (XNIyN
) to be criticized.

Next, using a Y and X microscope, the transfer area So is marked AYo.
, AXo, preset the X counter, and position the stage so that the optical axis of the objective lens 210 passes through the origin of the coordinate system αβ0, so that both the X counter and the X counter become zero. do. Then, by positioning the stage so that the coordinate values determined by the X counter and the X counter become the previously determined coordinate values (X, P+yP), the remaining resist Pa in the transfer area SO can be confirmed on the monitor television 23. be done. Also, when the stage is positioned at the coordinate value (XNIyN), the monitor TV 2
Since no residual resist is observed in No. 3, it can be confirmed that it is not a foreign object on the reticle to be inspected R2.

Therefore, the coordinate value (Xp+
By observing the corresponding position on the reticle R2 to be inspected using a microscope or the like based on the reticle Vp), the attachment of foreign matter may be finally confirmed, and the reticle R2 to be inspected may be returned to the cleaning process.

As described above, in the first embodiment of the present invention, marks provided in advance on a wafer were aligned using an off-axis wafer alignment microscope of a reduction projection exposure apparatus. However, as another example, a so-called TTL alignment device that aligns the image of the mark on the wafer back-projected onto the reticle by the projection lens 1 and the mark on the reticle is used to transfer the transfer area of the reticle. The projected image and the transfer area on the wafer can be directly aligned. In this way, the alignment accuracy for each transfer area on the wafer W may be improved as well as the off-axis alignment.

In any case, it is sufficient that the reticle and the wafer can be aligned directly or indirectly, and marks may be formed on the wafer so that alignment can be performed appropriately for the exposure C device used.

Next, a second embodiment of the present invention will be described using FIG. 9. In the second embodiment, the alignment marks for positioning the sea urchins are not formed with positive resist, but with other materials such as silicon oxide 5i02,
It is formed using materials used for manufacturing integrated circuits such as silicon nitride Si3N4, silicon Si1 aluminum AI, molybdenum Mo1 tungsten W, PSG, and polyimide. FIGS. 9(a) to 9(e) show a process for forming an alignment mark, and FIG. 9(a) shows a layer 110 formed of an alignment mark forming material on a wafer W by vapor deposition or the like. After forming a positive resist layer 100 thereon, the portions other than the marks are exposed to light using a luminous flux value using a mark reticle R+ with the marks MX, MY, and Mθ as light shielding parts. Next, when the positive resist layer 100 is developed, as shown in FIG. 9(b), the positive resist layer 100 is developed.
A resist layer 100 remains on layer 110.

Next, after etching the layer 110 on this wafer W,
When the positive resist layer 100 is removed, a portion of the layer 110 becomes a mark MX, as shown in FIG. 9(C).

Marks N are left on the wafer W in a convex shape corresponding to MY and Mθ. Now, when a wafer W on which only the mark R is formed is prepared and a foreign object inspection is performed on the reticle, a positive resist layer 100' is coated on the surface as shown in FIG. 9(d). After the formation, the wafer W is set in an exposure apparatus, and after directly or indirectly aligning with the reversal reticle R3 using the mark N, the reversal pattern is exposed.

This forms a latent image in the positive resist layer 100'. Next, the reticle to be inspected R2 is inverted to the reticle R3.
Instead, it is set in the exposure apparatus, and the mark A' is used to align directly or indirectly with the wafer W, and exposure is performed. FIG. 9(e) shows how a portion complementary to the portion already exposed by the reversal reticle R3 is newly exposed. If foreign matter remains in the light transmitting portion of the reticle to be inspected R2, a dark portion Dm occurs. . When this positive resist layer 100' is developed, a residual resist (P) is formed on the wafer W at a position corresponding to the image of the foreign object, as shown in FIG. 9(f).
Appears in a convex shape on the surface. After this, this residual resist P
Detection and confirmation of whether there is a foreign object on the reticle R2 to be inspected are performed in the same manner as in the first embodiment.

The second embodiment differs from the first embodiment in that the mark A' is formed in advance using a material similar to that of September 2012.If the Ueno resist used for pattern inspection is removed, It can be used again for inspection, and although extra steps such as etching are required compared to the first embodiment, it has the advantage that once the mark N is formed and cut, there is no need to form the mark N. be. Here it is 2゜eh□. Engineering, yo. , tsu, 2,
I-6° and -1-ri were formed by etching, but
Of course, it can also be formed using riffs and offs.

As an improved example of the second embodiment, the alignment mark may be formed using a negative resist. Although the process is simple and not shown in the drawings, the only difference from the second embodiment is that the mark N in FIG. 9(C), which is an explanatory diagram of the second embodiment, is formed with a negative resist. This embodiment has the advantage that alignment marks can be easily formed since no steps such as etching or lift-off are required.

In the first and second embodiments, a positive resist was used as the photosensitive material for exposure of the reverse pattern and the normal pattern.
It is also possible to implement using a negative resist. In this case, the transferred foreign matter appears as a pattern in the resist.

In the above description of each embodiment of the present invention, it is assumed that the inverted reticle R3 is transferred first and then the reticle to be inspected R2 is transferred, but the order of transfer of the reticle may be reversed. good. However, when the inspection of the reticle R2 to be inspected is completed, the exposure device
It goes without saying that if it is desirable to set , it is better to transfer the reticle to be inspected R2 later.

Furthermore, although an optical reduction projection type exposure apparatus was used as the exposure apparatus, the present invention is applicable to a type of exposure apparatus that transfers the pattern of a mask onto the photosensitive layer of a wafer, such as a projection exposure apparatus of the same magnification, or a contact type exposure apparatus. The present invention can be similarly applied to an exposure apparatus or a gloximity type X-ray exposure apparatus.

For inspection, Ueno was used in the above example, but when transferring marks and patterns, a glass plate or aluminum plate with a photosensitive material coated on the surface may be used as long as it can be set in an exposure device. It's okay.

(Effects of the Invention) As described above, according to the present invention, the images of the mask to be inspected and the inverted mask can be relatively aligned with high precision and transferred to the same photosensitive material, so that even foreign particles near the pattern edges can be It has the advantage of being detectable. Furthermore, when using the present invention, there is no need to transfer the inversion mask and the mask to be inspected to a photosensitive material in succession; instead, the photosensitive material to which the latent image of the pattern of one mask has been transferred is stored, and the pattern of the other mask is transferred to the photosensitive material. Since patterns can also be transferred, there is also the advantage that the process is flexible, such as not using the same exposure device.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a reduction projection type exposure apparatus suitable for implementing the method according to the present invention, FIG. 2 is a plan view of a mark reticle for transferring only marks on a wafer, and FIG. 3 is a plan view of a target to be inspected. A plan view of a reticle (mask), FIG. 4 is a plan view of an inverted reticle (mask), and FIG. 5 is a cross-sectional view showing changes in the wafer surface due to mark formation, overprinting, and development. A first embodiment of the present invention. 6 is a plan view showing the arrangement of marks on a wafer, FIG. 7 is a plan view showing a group of transferred patterns, FIG. 8 is a schematic block diagram of an apparatus for inspecting the wafer, FIG. 9 is a process diagram according to a second embodiment of the present invention. Applicant: Nippon Kogaku Kogyo Co., Ltd. Agent Takashi Watanabe Male Off-Scale Figure 3 Figure 268- Age 9 Figure

Claims (1)

[Claims] A step of placing a photosensitive material having a positioning mark detectable by a positioning device of the exposure device on an exposure device; a mask to be inspected having a predetermined pattern and a positioning mark. , and a reversal mask having a pattern in a negative relationship with the pattern of the mask to be inspected and a mark for alignment is prepared in advance, and one of the mask to be inspected and the reversal mask is placed on an exposure device. , a first transfer step of aligning the one mask and the photosensitive material using the marks on the one mask and the marks on the photosensitive material, and exposing the pattern of the one mask onto the photosensitive material; ; placing the other of the mask to be inspected and the inversion mask on an exposure device, and aligning the other mask and the photosensitive material using marks on the other mask and marks on the photosensitive material;
The latent image in the photosensitive material formed in the first transfer step,
a second transfer step of overlapping and exposing the pattern of the other mask; a step of developing the photosensitive material after the first and second transfer steps; and inspecting the photosensitive state of the photosensitive material. 1. A method for inspecting a mask, comprising: an inspection step of inspecting whether or not the mask has defects.