JPH10260037A - Flatness measuring method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure flatness by subtracting deflection due to the dead weight of a platelike object computed or measured from the distorted state of the platelike object held with a holder. SOLUTION: In measurement of flatness, at first the distorted state of the upper face of a mask 203 is measured by a known method. Deflection 201 is deflection due to the dead weight of the mask when the mask is held with a holder of three-point support only by frictional force without addition of external force. The distorted state 203 of the upper face of the mask is the sum of the deflection 201 and flatness 202, and the deflection 201 due to the dead weight of the mask can be measured by a known measuring method. Because the shape of the mask is a simple platlike shape, the deflection 201 due to the dead weight of the mask can be correctly obtained by theoretical computation such as a finite element method. The flatness 202 of the mask to be finally obtained is obtained by subtracting the deflection 201 due to the dead weight from the measured value 203 of the distorted state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the flatness of a plate-like object such as a mask or a reticle for manufacturing a semiconductor.

[0002]

2. Description of the Related Art Conventionally, flatness measurement of a photomask, a reticle, and the like (hereinafter, referred to as a mask) has been performed using an apparatus having a structure as shown in FIG. The mask 2 is placed vertically (the normal direction of the surface on which the pattern on the mask is formed is horizontal) in order to avoid the influence of deflection due to its own weight.
It is held so that the mask surface does not bend due to its own weight,
The flatness 1 of the mask was measured using a detection device such as an interferometer provided in the horizontal direction (horizontal direction). A flatness measuring device of this type is Flatmas manufactured by TROPEL.
ter 200M.

[0003]

In the conventional apparatus as described above, the effect of the deflection due to its own weight can be eliminated by placing the mask vertically, but the mask transport required for performing measurement, inspection, and the like is required. Since it is necessary to always maintain a constant position even when receiving the vibration or acceleration, the position of the mask must be maintained by applying some mechanical external force to the mask. The external force for holding the mask distorts the mask in an unpredictable manner, and this distortion causes a non-negligible error factor in the flatness measurement.

In addition, when the mask is placed vertically, there is another problem that it is difficult to transfer the mask when performing automatic conveyance. Furthermore, when configuring a multi-function device in combination with other devices such as coordinate measurement, defect inspection, etc., many other devices require a configuration in which a mask is placed horizontally (mask surface is horizontal). There is also a problem that it is difficult to combine a flatness measuring device with a device having these other functions.

The present invention has been made in view of such problems of the conventional flatness measuring apparatus, and eliminates unpredictable distortion of a mask surface, improves the accuracy of a flatness measuring function, and Flatness measurement function and other coordinate measurement, defect inspection,
It is an object of the present invention to realize a high-precision multifunctional device combining functions such as the above.

[0006]

In order to solve the above-mentioned problems, when the mask is supported on a special three-point support holder by a frictional force without applying an external force in a state where the mask is placed in a horizontal position, the mask is deformed. The state is reproduced very well. Furthermore, the deflection due to the mask's own weight is determined only by the mask's size, thickness, material (specific gravity, Young's modulus, Poisson's ratio) and support position, and theoretical calculations such as the finite element method Attention was paid to the fact that the calculated value of the deflection obtained by the above and the measured value are in good agreement. That is, if the type of the mask is known, the deflection due to its own weight can be known in advance. The distortion state of the mask is the sum of the "flatness" of the mask and the "deflection of the mask due to its own weight".

These are disclosed in Japanese Patent Application Laid-Open No. 5-33276.
1. We tried to use these to measure the flatness of the mask.As a result, we calculated or measured the deflection of the mask due to its own weight with the mask placed horizontally, and calculated this amount from the measured value of the mask distortion state. The reduction enables the flatness of the mask to be measured with high accuracy.

According to the present invention, first, in the method for measuring the flatness of a plate-like object, the plate-like object is provided with holders arranged at three places, and each of the holders is Holding substantially in point contact with the lower surface of the plate-shaped object, and holding the plate-shaped object surface in a horizontal direction, without applying any mechanical external force, and holding the plate-shaped object in a holding tool adjusted to hold only by frictional force; Measure the distortion state of the plate-like object from above or below, subtract the deflection due to the weight of the plate-like object obtained by theoretical calculation or measurement from the measured distortion state, the flatness of the plate-like object The flatness measurement method is characterized in that the flatness of the plate-like object is measured by calculating the flatness (claim 1).

[0009] Secondly, "a plate has a retainer substantially in contact with the lower surface of the plate-like object at three points,
And measuring the holding state of the plate-like object from above or below, the holder being adjusted so as to hold only the frictional force without applying any mechanical external force to each of the plate-like object surfaces in a horizontal direction. A measuring device, a storage device that stores the deflection due to its own weight of the plate-like object obtained by theoretical calculation or measurement, and subtracts the deflection due to the stored own weight from the measured distortion state, A flatness measuring device, comprising: an arithmetic device for calculating flatness. (Claim 2) "is provided.

Third, "at least one selected from a coordinate measuring unit, a defect inspecting unit, or a pattern drawing unit is added.

3. The flatness measuring apparatus according to claim 2, wherein the pattern is drawn. (Claim 3) "is provided.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a flatness measuring apparatus according to an embodiment of the present invention. 2A is a plan view of the stage 15, and FIG. 2B is a cross-sectional view taken along the line AB. The flatness measuring apparatus of this embodiment is combined with a measuring apparatus of a pattern coordinate formed on a mask. That is, it is a flatness-coordinate measurement sharing device.
The embodiment of the present invention is based on the embodiment of Japanese Patent Application Laid-Open No. 5-332762.

The flatness measuring apparatus of the present invention basically includes
As shown in FIG. 2, a holder for holding the mask at only three points without applying an external force and only a frictional force, an edge detecting device for detecting an edge of a pattern on the mask, and the like (see, for example, Japanese Unexamined Patent Application Publication No. The method is not limited to the method for detecting the scattered light or the diffracted light of the laser light according to the embodiment, and a detection unit or the like based on image processing may be used.) It comprises a detection device (such as an autofocus).

In the flatness measurement, first, the distortion state of the mask upper surface 203 shown in FIG. 5C is measured. Since this measuring method is disclosed in detail in Japanese Patent Application Laid-Open No. 4-65619, its explanation is omitted here. As a result, for example, a distortion state (two-dimensional distribution of distortion amount) as shown in FIG. 4 is measured. The distortion state measured in this way is stored in main controller 20 in FIG.

FIG. 5 is a diagram showing the relationship among the deflection, flatness, and distortion state of the mask. FIG. 5A shows a mask 3
5 shows a deflection 201 caused by the weight of the mask when the holder is held only by a frictional force without applying an external force by a point support holder. Fig. 5-
b indicates the flatness 202 of the mask. At this time, the distortion state 203 (FIG. 5-c) of the mask upper surface measured as described above is
The sum of 201 and 202 is obtained.

Here, the deflection 201 of the mask due to its own weight is performed.
Can be measured, for example, by the measurement method disclosed in Japanese Patent Application Laid-Open No. 5-332762. Further, since the shape of the mask is a simple plate shape, the deflection due to the own weight of the mask 2
01 can be accurately obtained by theoretical calculation using, for example, the finite element method. According to these methods, the amount of deflection due to its own weight is determined in advance according to the type of mask (for example, 5 in., T = 0.09 in., Quartz or the like or 6 in., T = 0.25 in., Quartz, etc.) in FIG. It is stored in the storage device 22.

The flatness 202 of the mask to be finally obtained
As is apparent from FIG. 5, the storage device 22 is obtained from the measured value 203 of the distortion state stored in the main controller 20 in FIG.
Is obtained by subtracting the deflection 201 due to its own weight stored in the. For the method of coordinate measurement, see
No. 3,327,61, the description is omitted.

In the embodiment of the present invention, an example in which the flatness measurement and the coordinate measurement are combined has been described. However, it is needless to say that the flatness measurement can be performed alone. In this case, the mask distortion measuring method is not limited to the method according to the embodiment of the present invention. Autofocus is based on image processing,
An oblique incidence method of laser, etc. can be considered. An example of autofocus using image processing is disclosed in
828 and JP-A-3-44608. Examples of the autofocusing by the oblique incidence method of the laser are disclosed in JP-A-61-290414 and JP-A-62-190410.
Is disclosed. In addition, a method using an interferometer instead of using the autofocus may be considered. This can be performed using, for example, a TROPEL / MASK flatness measuring / analyzing apparatus Flatmaster 200 / Mask. .

In the embodiment of the present invention, the measurement of the distortion state is performed from above the mask.
The configuration may be such that the pattern surface is downward, and distortion measurement or coordinate measurement is performed from below the mask.
In the embodiment of the present invention, the flatness measurement and the coordinate measurement are combined, but, of course, an apparatus configured only with the flatness measurement may be used. In addition to the coordinate measurement, other functions such as defect inspection and pattern drawing (these devices generally perform processing with a mask mounted horizontally, so that the combination with the flatness measurement in the present invention is easy). May be combined.

[0020]

As described above, according to the present invention, it is possible to hold the mask only by frictional force without applying an external force by using a special three-point supporting holder by placing the mask horizontally. The flatness measurement device that measures the flatness with the mask placed vertically, the high-precision plane that eliminates the flatness measurement error caused by the distortion of the mask due to artificial and unpredictable external force for holding the mask Measurement is possible.

Further, since the mask is placed horizontally, it is easy to transfer the mask when performing automatic conveyance of the mask. Further, since a coordinate measuring device, a defect inspection device, a pattern drawing device and the like are generally devices having a configuration in which a mask is placed horizontally, it is easy to incorporate a flatness measuring function into these devices.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the device according to the present invention.

FIG. 2 is a view of a stage (holder) of an embodiment of the apparatus according to the present invention.

FIG. 3 is an example of a conventional flatness measuring device.

FIG. 4 is an example of a measurement result of a distortion state of a mask in an embodiment of the apparatus according to the present invention.

FIG. 5 is a diagram illustrating a method of calculating flatness in the present invention.

Claims (3)

[Claims] In the method for measuring flatness of a plate-like object, the plate-like object has retainers arranged at three positions, and each of the retainers substantially corresponds to a lower surface of the plate-like object. Point contact, and furthermore, the plate-like object surface is kept in a horizontal direction, without applying any mechanical external force, and is held by a holder which is adjusted to be held only by frictional force, and the distortion state of the plate-like object is maintained. By measuring from above or below and subtracting the deflection due to the own weight of the plate-like object obtained by theoretical calculation or measurement from the measured distortion state, and calculating the flatness of the plate-like object, A flatness measuring method characterized by measuring the flatness of an object. 2. A substantially point contact with the lower surface of the plate-like object,
A holder having three retainers and being adjusted so as to maintain each of the plate-like object surfaces in a horizontal direction and apply only a frictional force without applying any mechanical external force; A measuring device that measures the distortion state of the plate-like object from above or below, a storage device that stores the deflection due to its own weight of the plate-like object obtained by theoretical calculation or measurement, and the storage device that is stored from the measured distortion state. An arithmetic unit that subtracts the deflection due to its own weight and calculates the flatness of the plate-like object,
A flatness measuring device comprising: 3. The method according to claim 1, wherein at least one selected from a coordinate measuring unit, a defect inspecting unit, and a pattern drawing unit is added, and coordinate measurement, defect inspection, or pattern drawing is performed in addition to flatness measurement. 2. The flatness measuring device according to 2.