JP3064613B2 - High precision coordinate measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-precision coordinate measuring apparatus utilizing laser interference.

[0002]

2. Description of the Related Art First, FIG. 11 showing the concept of a laser interference coordinate measuring instrument made based on the prior art will be described.
Rectangular reflecting mirrors Mx and My are fixed on the stage 6 movable in the X and Y directions. These mirrors M
x and My are respectively arranged so as to be perpendicular to the measuring arms of the X-axis measuring laser interferometer (hereinafter referred to as X-axis interferometer) Ix and the Y-axis measuring laser interferometer (hereinafter referred to as Y-axis interferometer) Iy. I have. When the stage 1 moves in the X direction, the movement amount in the X direction is measured by the X-axis interferometer Ix, and when the stage 1 moves in the Y direction, the movement amount in the Y direction is measured by the Y-axis interferometer Iy. Reference numeral 3 denotes a surface position detector such as a position detecting microscope for detecting the position of the drawn figure 5 on the DUT 4. The optical axes of the X and Y axis interferometers Ix and Iy and the optical axis of the surface position detector 3 are perpendicular to each other and intersect at one point. With this configuration, even if the Abbe condition is satisfied and the stage 6 is slightly tilted around the X axis and / or the Y axis, a measurement error (abbe error) proportional to the tilt angle occurs. Absent. However, in this example, the heavy stage 6 having the object 4 to be measured must be moved, and therefore, the X-axis interferometer Ix and the Y-axis interferometer Iy
If the base (not shown) to which the surface position detector 3 is fixed does not have sufficient rigidity, the base is bent. As a result, the distance between the interferometer and the reflecting mirror changes, causing an error. In order to achieve nanometer accuracy, it is necessary to remove such errors. For that purpose, the rigidity of the base must be increased, and the whole apparatus becomes large and heavy. Therefore, the key to improving accuracy is to make the moving object as lightweight as possible.

FIG. 12 is a conceptual diagram of three-dimensional measurement.
In the configuration shown in FIG. 1, a Z-axis interferometer Iz in the Z-axis direction and a Z-axis reflecting mirror Mz are added to the lower surface of the stage 6, and the stage 6 is configured to move in three dimensions of X, Y, and Z. I have. 5a is a three-dimensional surface. Also in this example, the heavy stage 6 must be moved, and an error due to the deflection of the base cannot be avoided. A method of reducing the weight of the moving object is to place the interferometers Ix, Iy, and Iz inside the three reflecting mirrors instead of the stage 6 and move the interferometers together with the surface position detector 3. In this case, both the interferometer and the surface position detector can be much lighter than the stage. However, when trying to bring the interferometer closer to the surface position detector, the interferometer hits the object to be measured. Therefore, if the optical axis of the interferometer is shifted upward so as not to make contact, Abbe's condition cannot be satisfied. Such a disadvantage is the same in the case of two dimensions.

[0004]

It is said that a length measuring system utilizing light wave interference can achieve extremely high accuracy on the order of nanometers. However, unless the measurement system including position detection is comprehensively considered, the high accuracy inherent in the interferometer cannot be realized. Further, in the conventional coordinate measuring device, there is a problem that a heavy stage must be moved two-dimensionally, a rigid base that does not bend is required, and the stage becomes large. Furthermore, means for measuring a three-dimensional object with high accuracy has not yet been known. SUMMARY OF THE INVENTION It is an object of the present invention to realize the high accuracy of an interferometer by reducing the weight of a moving part in length measurement or coordinate measurement.

[0005]

According to the high accuracy coordinate measuring apparatus of the present invention, a reflecting mirror is fixed to a base, and a movable holder movable in a direction perpendicular to the reflecting mirror is provided. First and second interferometers for measuring a relative amount of movement between the position detecting device and the reflecting mirror and the position detecting device are provided;
Further, the first and second interferometers each have a measurement optical system and a reference optical system, and the optical axes of the measurement optical systems of the first and second interferometers are respectively set from the measurement points of the position detecting device. L1 and D2 (where D ≠ L), and the moving amount measurement values of the movable holder measured by the first and second interferometers are d1 and d2,
When m = L / D, the movement amount S of the measurement point is calculated by the following equation: S = (d2-md1) / (1-m).

[0006]

By moving the movable holder provided with the position detecting device in place of the stage, the moving portion is reduced in weight, and a measurement error hardly occurs. Also, two interferometers are provided at different heights from the measurement point, and based on interference fringe measurement data obtained from each interferometer, the moving distance is determined using a parameter including the position of each interferometer from the measurement point. The calculation cancels out Abbe's error due to the tilt of the movable holder and cancels it.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 10 is a configuration diagram showing a conceptual diagram of the first embodiment. On the base 1, plane reflecting mirrors Mx, My, and Mz are fixed by appropriate means (not shown). The movable holder 2 is provided with a surface position detector 3, an X-axis interferometer Ix, a Y-axis interferometer Iy, and a Z-axis interferometer Iz. The holder 2 is configured to be freely movable in three axes of X, Y and Z by a well-known three-dimensional drive mechanism, and is placed on the base 1 by a surface position detector 3 attached to the movable holder 2. The three-dimensional surface position of the object 4 to be measured is detected.

Here, one embodiment of a method for removing Abbe's error will be described with reference to FIGS. FIG. 1 shows FIG.
FIG. 5 is a diagram in which only a portion for performing measurement in the X-axis direction is extracted from FIG. In the figure, an X-axis interferometer Ix fixed to a movable holder 2 includes two interferometers 20 and 30 and a subtractor 41 that performs a predetermined operation based on the number of interference fringes measured by these interferometers. Have. The interferometers 20 and 30 are fixed to the measurement point O of the position detection device 3 at intervals of D and L, respectively.

FIG. 2 is an explanatory diagram of an optical path of a main part of the interferometer 20 shown in FIG. In the figure, all optical components are fixed to a movable holder 2 (not shown here). Numeral 21 denotes a polarizing prism, of which a linearly polarized light component (p component) vibrating in parallel to the paper surface of the light flux passing therethrough passes through the polarizing prism 21 and the quarter-wave plate 23 and is reflected by an X-axis reflecting mirror Mx (here, X-axis reflecting mirror Mx). (Not shown), and again passes through the quarter-wave plate 23, and then is reflected by the polarizing prism 21 to form another polarizing prism 2.
Head to 2. Here, the reflected light is transmitted through the quarter-wave plate 24, reflected by the fixed reflecting mirror 8, transmitted again through the quarter-wave plate 24, and then transmitted through the polarizing prism 22. Then, after being reflected by the right-angle prism 25, the light passes through the polarizing prism 22 and the quarter-wave plate 24 and travels to the X-axis reflecting mirror Mx. Further, the light beam reflected here passes through the quarter-wave plate 24 again, is reflected by the polarizing prism 22 and the polarizing prism 21, is reflected by another fixed reflecting mirror 9, and is again reflected by the quarter-wave plate 23. The light passes through the prism 21 and exits from the interferometer 20.

On the other hand, a linearly polarized light component (s component) vibrating perpendicularly to the plane of the paper is reflected by the polarizing prism 21 and is reflected by a quarter-wave plate 26 whose back surface is a reflecting mirror. 22 and is reflected by a quarter-wave plate 27 whose back surface is a reflecting mirror, like the quarter-wave plate 26.
After that, the light is reflected by the polarizing prism 22 and becomes a right angle prism 25.
, Reflected by the polarizing prism 22, reflected again by the quarter-wave plate 27, transmitted through the polarizing prisms 22 and 21, and
The light is reflected by the quarter wave plate 26 and the polarizing prism 21 and emitted from the interferometer. Here, the p component and the s component are emitted together.

FIG. 3 shows the configuration of the main part of the optical path of an embodiment of the interferometer 30. The difference from FIG. 2 is that the fixed reflecting mirrors 8 and 9 are removed, and In the total 20, two light beams are directed to the reflecting mirror Mx, while in the case of the interferometer 30, four light beams are directed. Interferometer 2
The emitted lights from 0 and 30 are respectively guided to an interference fringe detection system as shown in FIG. In the figure, reference numeral 11 denotes a half-wave plate, and p and s components from each interferometer are each a half-wave plate 1
After the polarization plane is rotated by 45 ° around the optical axis by 1 and transmitted through the polarizing prism 7, interference fringes are formed, and this is detected by a known photodetector 12. The intensity of the interference fringes is converted into an electric signal by the photodetector 12, and the number of interference fringes is counted by a known means.

With the movement of the movable holder 2, the position detecting device 3
Is moved by S in the X-axis direction. It is also assumed that the movable holder 2 has been tilted clockwise by α after the movement. The number of interference fringes Z1 measured by the interferometers 20 and 30, respectively.
, Z2 are given by the following equations. That is, Z1 = (S−Dα) / (λ / 4) (1) Z2 = (S−Lα) / (λ / 8) (2) Therefore, when the difference Z is calculated by the subtractor 41, Z = Z2 −Z1 = {S− (2L−D) α} / (λ / 4) (3) From this equation, when D = 2L, Z = S / (λ / 4) (4) The movement amount S is obtained by the following equation. S = (λ / 4) Z (5) As described above, even if the position detection device 3 rotates around the measurement point O, this value does not change, so that Abbe's error can be removed. In FIG. 1, reference numeral 10 denotes a probe for detecting the position of the measurement point O of the position detecting device 3, which includes a photoelectric microscope, a scanning tunneling microscope (STM), and an atomic force microscope (AF).
A known device such as M) can be used.

FIG. 5 shows a second embodiment. This example is shown in FIG.
The optical system of the interferometer 20 in the example shown in FIG. 3 is replaced with the interferometer optical system shown in FIG. When counting the number of these interference fringes, it enters a subtracter 41 through a thinning circuit 42 which outputs one count pulse for two interference fringes. The other interferometer 31 is the same as the interferometer 30 except that one counting pulse enters the subtractor 41 for one interference fringe. In this configuration, one interference fringe counting pulse in each interferometer is λ / 8.
Therefore, the output of the subtractor 41 is expressed by the equation (3) as before. Therefore, when D = 2L as in the previous embodiment, Abbe's error is eliminated.

Here, for convenience of explanation, one of the interferometers 31 will be described.
Although one counting pulse corresponds to the interference fringe, it is not possible to measure the fraction of the interference fringe by associating two or four or more pulses to one interference fringe by a known interference fringe dividing method. Easy. Now, as an interference fringe detection system of the interferometer 30, one that detects M count pulses in one interference fringe is used.
As an interference fringe detection system of the interferometer 31, N (N
Is larger than M), the Abbe error is eliminated when MD = NL is satisfied, and the interference fringes can be divided into M to measure more finely.

FIG. 6 shows a third embodiment. That is, the counting pulse from the interferometer 30 is counted by the counter 43, the number of pulses is multiplied by M by the multiplier 45, and the interferometer 31 is counted by the counter 44.
After counting the counting pulses from, the number of pulses is multiplied by N in a multiplier 46 and then input to a subtractor 41. Also in this case MD
When = NL, Abbe's error is eliminated. Assuming that one counting pulse from the interferometer 30 or 31 corresponds to the length of λ / 2K (K is an integer), the displacement S of the measuring point of the position detecting device 3 is represented by Z Then, S = λZ / 2K (N−M) (6)

FIG. 7 shows the count values Z 1,
This is a fourth embodiment in which the movement amount S is obtained by the calculator 47 using Z2 as an input. Assuming that the count value measured by the interferometer 30 is Z1, the movement amount d1 of the movable holder 2 in that part is Z1.
Is as follows: d1 = S-Dα = Z1 one (λ / 2K) (7) Assuming that the count value measured by the interferometer 31 is Z2,
The amount of movement d2 of the movable holder 2 at that portion is as follows: d2 = S-Lα = Z2 (λ / 2K) (8) The arithmetic unit 47 performs the following calculation when m = L / D (9) . S = (λ / 2K) (Z2−mZ1) / (1−m) (10) or S = (d2−md1) / (1−m) (11) In this way, Abbe's error is not included. Correct travel distance S
Is required. Here, if m = ２, then DL = L
/ 2, and the distance (DL) between the two interferometer optical axes is L /
Can be 2. Even when the number of times the measurement light beam of the two interferometers reciprocates with the reflecting mirror is different, it is extremely easy to derive the equation corresponding to the equation (10) or (11). It goes without saying that it is included in the category.

FIGS. 8 and 9 show a fifth embodiment. These are examples in which the light beam emitted from the optical system shown in FIGS. 2 and 3 is returned to the interferometer again by the right-angle prism 48.
The optical system of FIG. 8 is used as the interferometer 20 in the embodiment of FIG. 1, and the optical system of FIG. 9 is used as the interferometer 30. In this example, the measurement light beam of the interferometer 20 reciprocates six times with the reflection mirror Mx. The measuring beam of the interferometer 30 is 8
Go back and forth. Therefore, if 3D = 4L is satisfied, Abbe's error is eliminated. The optical axis interval between the interferometer 20 and the interferometer 30 is DL, but DL = L / 3. Therefore, if L is the same, the distance between the interferometer optical systems can be reduced, and the interferometer can be compactly integrated.
If the intervals are the same, the measurement points can be set further away.

As seen from the above embodiment, when two interferometers are used and m = N / M = L / D, (10)
A correct movement amount S that does not include Abbe's error is obtained by the equation (11).

In the above embodiment, the interferometer is fixed to the movable holder and the reflecting mirror is fixed to the base. However, the present invention is not limited to this. The reflecting mirror is mounted on the movable holder and the interferometer is mounted on the base. Is fixed, and Abbe's error can be removed if the above relation is satisfied.

The high-precision coordinate measuring apparatus according to the present invention eliminates Abbe's error and enables high-precision measurement.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of a high-precision coordinate measuring device according to the present invention.

FIG. 2 is an explanatory view of an optical path of the interferometer in FIG. 1;

FIG. 3 is an explanatory view of an optical path of another interferometer in FIG. 1;

FIG. 4 is a schematic diagram of a photodetector omitted in FIG.

FIG. 5 is a configuration diagram of a high-precision coordinate measuring device according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a main part of a high-precision coordinate measuring device according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of a main part of a high-precision coordinate measuring device according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory view of an optical path of one interferometer according to a fifth embodiment of the present invention.

FIG. 9 is an explanatory view of an optical path of another interferometer according to the fifth embodiment of the present invention.

FIG. 10 is a configuration diagram showing a concept of three-dimensional measurement according to the present invention.

FIG. 11 is a configuration diagram showing a concept of conventional two-dimensional measurement.

FIG. 12 is a configuration diagram showing the concept of three-dimensional measurement.

[Explanation of symbols]

 Reference Signs List 1 base 2 movable holder 3 surface position detector 4 DUT 6 stage 7 polarizing prism 8 reflecting mirror 9 reflecting mirror 10 probe 11 1/2 wave plate 12 photodetector 20 interferometer 21 polarizing prism 22 polarizing prism 23 1 / 4 wavelength plate 24 1/4 wavelength plate 25 right angle prism 26 1/4 wavelength plate 27 1/4 wavelength plate 30 interferometer 41 subtracter 42 thinning circuit 43 counter 44 counter 45 multiplier 46 multiplier 47 arithmetic unit 48 Right-angle prism Mx X-axis reflecting mirror My Y-axis reflecting mirror Mz Z-axis reflecting mirror Ix X-axis interferometer Iy Y-axis interferometer Iz Z-axis interferometer

Claims (6)

(57) [Claims] 1. A base, a reflecting mirror fixed to the base,
A movable holder provided on the base movably in a direction perpendicular to the reflecting mirror, a position detecting device fixed to the movable holder, and the reflecting mirror and position detecting device fixed to the movable holder. First and second interferometers for measuring a relative movement amount of the first and second interferometers, each of the first and second interferometers has a measurement optical system and a reference optical system, and the first interferometer The optical axis of the measuring optical system is located at a distance of L from the measuring point of the position detecting device, and the optical axis of the measuring optical system of the second interferometer is D (where D ≠ L) from the measuring point. The distance measured value of the movable holder measured by the first interferometer is d1, the measured value of the movable holder measured by the second interferometer is d2, and m = L / When D, the moving amount S of the measuring point is calculated by the following equation: S = (d2-md1) / (1-m) High precision coordinate measuring device. 2. A base, a movable holder provided to be movable in one direction with respect to the base, a position detection device fixed to the movable holder, and a reflection fixed to the movable holder. A mirror, and first and second interferometers fixed to the base for measuring a relative movement amount between the reflecting mirror and a position detecting device,
The first and second interferometers each have a measuring optical system and a reference optical system, and the optical axis of the measuring optical system of the first interferometer is a distance L from the measuring point of the position detecting device. And the second
The optical axis of the measuring optical system of the interferometer is located at a distance of D (where D ≠ L) from the measurement point, and the measured value of the amount of movement of the movable holder measured by the first interferometer is d1, Second
When the measured value of the moving amount of the movable holder measured by the interferometer is d2 and m = L / D, the moving amount S of the measuring point is calculated by the following equation: S = (d2-md1) / (1-m) A high-precision coordinate measuring device characterized by calculating. 3. A base, a reflecting mirror fixed to the base,
A movable holder provided on the base so as to be movable in a direction perpendicular to the reflecting mirror, a position detecting device fixed to the movable holder, and the reflecting mirror and position detecting device fixed to the movable holder 2 First and second interferometers for measuring a relative movement amount of the first and second interferometers, each of the first and second interferometers has a measuring optical system and a reference optical system, The optical axis of the measuring optical system of the meter is at a distance of L from the measuring point of the position detecting device, and the optical axis of the measuring optical system of the second interferometer is D (where D ≠ L) from the measuring point. And the number of times that the measurement light beam of the first interferometer reciprocates with the reflecting mirror is N
NL = MD, where M is the number of times (N is an integer of 2 or more) and the number of times that the measurement light beam of the second interferometer reciprocates with the reflecting mirror is M (M is an integer smaller than N). A high-precision coordinate measuring apparatus which satisfies a relationship and further calculates a movement amount of a measurement point from a difference between interference fringes including fractions measured by the two interferometers. 4. A base, a movable holder provided to be movable in one direction with respect to the base, a position detection device fixed to the movable holder, and a reflection fixed to the movable holder. A mirror, and first and second interferometers fixed to the base for measuring a relative movement amount between the reflecting mirror and a position detecting device,
The first and second interferometers each have a measuring optical system and a reference optical system, and the optical axis of the measuring optical system of the first interferometer is a distance L from the measuring point of the position detecting device. And the second
The optical axis of the measuring optical system of the interferometer is located at a distance of D (where D ≠ L) from the measuring point, and the number of times that the measuring light beam of the first interferometer reciprocates between the reflecting mirror and the optical axis. When N times (N is an integer of 2 or more) and the number of times that the measurement light beam of the second interferometer reciprocates between the reflecting mirror is M times (M is an integer smaller than N), NL = MD A high-precision coordinate measuring apparatus that satisfies the following relationship, and further calculates a movement amount of a measurement point from a difference between interference fringes including fractions measured by the two interferometers. 5. The reflection mirror according to claim 1, wherein the reflection mirror has an X-axis and a Y-axis reflection mirror fixed on an X-axis and a Y-axis, respectively, and the movable holder has an X-axis with respect to the base. And an X-axis interferometer provided with the first and second interferometers respectively facing the X-axis and Y-axis reflecting mirrors in the movable holder. 4. A high-precision coordinate measuring apparatus according to claim 1, further comprising a Y-axis interferometer. 6. The Z-axis reflecting mirror according to claim 5, wherein the Z-axis reflecting mirror is fixed, and the movable holder is provided so as to be able to move in parallel with the base in the Z-axis direction. 6. A Z-axis interferometer provided with the first and second interferometers facing a reflecting mirror.
High precision coordinate measuring device.