JPS61202111A - Position change detector - Google Patents

Abstract

PURPOSE:To detect changes in the position of a moving mirror satisfactorily, by arranging a first detection means for detecting relative positional deviation between an optical member and a moving body and a second detection means for detecting the inclination of a reflecting surface in comparison of positional deviations detected. CONSTITUTION:An MPU 54 calculates the capacitance difference between capacitors Cya and Cyb and determines the inclination value theta0 corresponding to the difference from a table stored in a memory 56. Moreover, the MPU 54 determines the positional deviation beta0 corresponding to the difference from the initial value of the capacitance of the capacitors Cya and Cyb in the same way. The inclination value theta0 and the positional deviation value beta0 are outputted to an arithmetic circuit 20 as data LY indicating variations. Then, the arithmetic circuit 20 calculates what position a laser flux LA is irradiated in the direction (x) on a reflecting surface 12A of a moving mirror 12. The y-way deviation DELTAy of the laser flux LA is determined at an incident point on the reflecting surface 12A.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a position change detection device, and for example, detects the position of a two-dimensionally moving stage used in a reduction projection exposure device using light wave interference. The present invention relates to a position change detection device suitable for highly accurate detection using a measurement system.

[Background of the invention]

Conventionally, when measuring the position or moving distance of a moving stage using a light wave interferometer, for example, if the moving mirror of the interferometer is not properly fixed, the moving mirror may be slightly moved when the moving stage starts or stops moving. However, there may be deviations. Such a shift may cause an error in measuring the actual moving distance of the moving stage.

Since this error is generally very small and may occur randomly, it takes a great deal of time and effort to discover it.

To be more specific, a movable mirror for an interferometer is generally required to have extremely high surface accuracy, and in some cases requires flatness of about a few tenths of the wavelength of the laser beam used.

When the moving stage moves in two dimensions of X and y,
A moving mirror is required for each x and y direction. The reflection planes of these movable mirrors are formed to be elongated in the X direction and in the X direction. For this reason, a movable mirror is generally made by coating the surface of a prismatic optical glass with a predetermined reflective surface, and this movable mirror is precisely mounted at a predetermined position on a movable stage.

By the way, even if the surface precision of the movable mirror itself is obtained by appropriate means, if the mounting precision on the movable stage is poor, the surface precision will eventually deteriorate. For example, if a movable mirror is screwed to a movable stage using bolts, etc.,
It was found that the surface accuracy deteriorated significantly depending on the tightening of the bolts. Another option is to use adhesive to attach the movable mirror, but when the adhesive hardens,
Unnecessary stress is applied to the bonding surface between the movable mirror and the movable table,
Surface accuracy will be significantly reduced. In particular, when adhesive is used, the position of the movable mirror may shift while the adhesive is curing. The correction work requires a great deal of effort.

From the above points of view, the method for fixing the movable mirror is to place the movable mirror at a fixed position on the movable stage, press it to the extent that the movable mirror does not move, and does not reduce the surface accuracy. Alternatively, it is recognized that a method of locking is preferable. In this case, since the movable mirror does not need to move in the length measurement direction perpendicular to its reflecting surface, the movable mirror is urged from the reflecting surface side with a weak panel so as to press the back of the movable mirror against the movable stage side. Just do it.

However, even if the surface accuracy of the movable mirror is ensured using the method described above, if large vibrations occur in the movable stage,
There is a possibility that the position of the movable mirror may shift. In particular, in a reduction projection type exposure apparatus, since chips on a wafer placed on a moving stage are exposed in a step-and-repeat manner, the acceleration required of the moving stage is also increased.

Therefore, the position of the movable mirror may shift slightly (for example, about 0.81 μm to 0.5 μm) due to the movement of the movable stage. When such a shift occurs, the position of the moving stage also shifts, which in turn causes a shift in the position of the chips on the wafer with respect to the exposure device, resulting in exposure being performed at the shifted position. Therefore, the displacement of the moving mirror is IC.

The position of the moving stage, including the shift of the moving mirror, is measured using a light wave interferometer. It could not be determined from the measured values, and in the end,
This cannot be discovered until the overlap between the exposed wafer and the mask and the arrangement of the chips are confirmed using a separate inspection device.

Such inconveniences exist not only in exposure apparatuses but also in other NC machine tools, laser processing apparatuses, etc. that use stages having interferometers as length measuring means or position change measuring instruments.

Furthermore, if the movable mirror is not placed exactly orthogonal to both the x and 7 directions, when exposing each chip on the wafer using the step-and-repeat method, the chip arrangement on the wafer will not follow the orthogonality of the movable mirror. There is also the inconvenience of being left behind.

Therefore, a positional shift occurs in the step arrangement or the superposition of patterns in accordance with the error in orthogonality. From this point of view as well, the production yield of ICs, LSIs, etc. will be significantly reduced.

[Purpose of the invention]

The present invention has been made in view of this point.

It is possible to easily detect minute shifts caused by tilting of the movable mirror, thereby reducing movement errors of the movable stage, which in turn reduces the occurrence of defects in ICs, etc., improving yields and improving the reliability of exposure equipment, etc. Its purpose is to achieve this goal.

[Summary of the invention]

The present invention provides first detection means (change detection circuit 30.: rndensors Cxa, Cxb, Cya.

cyb) and the reflective surface of the optical member (12A
, 14A) for detecting the slope of the capacitors Cxa, Cxb, Cya.
, Cyb), and use these detection means to detect positional changes.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a position change detection device according to the present invention will be described in detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 shows the overall configuration of an embodiment of the present invention. FIG. 2 shows a partially exploded table portion of this embodiment. Note that the dimensions are not necessarily the same. Next, FIG. 3 shows the electrical components of the above embodiment.Furthermore, FIG. 4 shows the following:
An example of a variation of the moving mirror is shown.

In these FIGS. 1 to 4, the moving stage 10
can be moved in both directions x and 7 shown in FIG. 1 or 2 by means not shown. The movable stage 10 is provided with a gap on two sides, each of which has a movable mirror 12, 14 fixed thereto. The movable mirror 12 extends in the X direction and has a reflective surface 124. The movable mirror 14 extends in the X direction and has one reflective surface 14A. The movable mirror 12.14 is, for example, a block of optical glass formed into a prismatic shape, and has a reflective surface 12A,
14A can be obtained, for example, by depositing a reflective thin film of metal.

Interferometers 16 and 18 are arranged at positions facing each of the aforementioned reflecting surfaces 12A and 14A. The X-direction interferometer 16 irradiates the laser beam LA perpendicularly to the reflective surface 12A, and the reflected laser beam is incident on the X-direction position of the reflective surface 127V, that is, the stage 1 due to interference.
This detects the position of 0 in the X direction. The X-direction interferometer 18 irradiates the laser beam LB perpendicularly to the reflective surface 14A, and the reflected laser beam is incident on the X-direction interferometer 18, and due to interference, the position of the reflective surface 14A- in the X direction, that is, the stage 10
The position in the X direction is detected.

Through these operations, the X-direction interferometer 16 moves to the stage 1.
The X-direction interferometer 18 successively outputs the X-direction position information Dy of 0, and the X-direction interferometer 18 successively outputs the X-direction position information Dx of the stage 10. These data are the coordinate values Tx of the stage 10
l so that it is input to the arithmetic circuit 20 that calculates s ”!
It's happening.

Next, moving mirror t2. As shown in FIG. 2, capacitance sensors are formed between i4 and the side surface of the stepped portion of the table 10, and the signals from these sensors are changed by the shielded cables 22, 24, 26, and 28, respectively. The change detection circuit 30 determines the amount of change in the reflection surface 12A of the movable mirror 12 in the X direction from the input data (capacitance value). The amount of change Lx in the X direction is determined and these are output to the arithmetic circuit 20. Amount of change Lx
, Ly include the amount of positional deviation and the amount of inclination in each axial direction.

Next, the capacitance sensor will be described in detail with particular reference to FIG. 2. FIG. 2 shows the movable mirror 12 in an exploded view. Note that the capacitance sensor is a movable mirror 12.1.
The same reference numerals will be used for the same constituent parts as shown in FIG.

In FIG. 2, reflective surfaces 12A, 1 of movable mirror 12.14
Conductive films 32 and 34 each divided into two in the longitudinal direction are provided on the surface opposite to 4A. These conductor films 32, 34 are formed by depositing metal such as aluminum, for example. A lead-out portion 36 is provided on the end side of the conductive film 32, 34 to enable electrical connection with the outside.
are provided for each. The surface of the conductive film 32.34 excluding this lead-out portion 36 is then covered with silicon oxide (st), for example.
o2) is coated with an insulating thin film.

The movable mirror 12.14 configured as described above is attached to the step of the stage 10 so that the conductive film 32.34 faces the step side 10A of the stage 10. To explain in detail, the step side surface 10A of the stage 10 has a protrusion 10B.
Two movable mirrors 1 are provided on these protrusions 10B.
2. It is placed on the step of the stage 10 so that the back side of 14 is in contact with it. The movable mirror 12.
The fixation is effected by pressing 14. This pressing force by the leaf spring 40 is taken into consideration so as not to reduce the surface area of the reflective surfaces 12A, 14A of the movable mirror 12.14.

In addition, the protrusion 1 [IB is used to regulate the position of the movable mirror 12j14 on the back surface side. Adjustment so that the reflective surfaces 12A and 14A are parallel to the y-axis and the y-axis is necessary to control the position of the movable mirror 12j14 on the back side.
This is because it is easier than when they are in contact with each other. Also,
The amount of protrusion of the protrusion 10B from the stepped side surface 10A is 1, for example, 5.
A movable mirror of more than υ1° with a small diameter of fl or 10 μm12. By attaching i4, a capacitor is formed between the electrically grounded stage 10 and the conductive film 32,34. Conductor film 32.3
4, the shielded cables 22, 24, 2
6.28 core wire is connected, shielded cable 22.2
The shield wires 4, 26, and 28 are connected to the stage 10.

Note that the conductor films 32 and 34 of the movable mirror 12 and the stage 10
A capacitor formed between Cya and Cya.

cyb represents a capacitor formed between the conductive film 32, 34 of the movable mirror 14 and the stage 10.

Let them be expressed as exa and Cxb. The capacitance of these capacitors Cxa, Cxb, Cya, and Cyb is approximately expressed as a function of the surface area of the conductive film 32, 34, the area of the stepped side surface 10A of the stage 10, and the distance between these surfaces.

Next, the electrical components will be explained with reference to FIG. Capacitors Cxa and Cxb formed between the stage 10 and the movable mirror 14 are connected to the changeover switch 42.
selectively via a capantance meter (rCPM)
J) 44# is connected.

This CPM 44 outputs an analog voltage according to the capacitance values of the capacitors exa and Cxb. C.P.
M44 is connected to an analog-to-digital converter (hereinafter referred to as "converter") 46, so that the analog signal input is converted into a digital quantity and output.

On the other hand, the capacitor Cya #Cyb formed between the stage 10 and the movable mirror 12 is similarly connected to the E switch 48.
selectively connected to the CPM50 via the CPM
50 is connected to the ADC 52.

AJ) C46, 52 are each connected to a microcomputer (hereinafter referred to as "Shinmei") 54, and a capacitor C
The capacitance values of xa, Cxb, Cya, and Cyb are converted into digital values and input to the MPU 54. In addition, MPrJ54 has a changeover switch 42.48
are connected to each other, and switching is controlled.

Next, a memory 56 is connected to the MPU 54. This memory 561 includes capacitors Cxa and Cxb.

The capacitance values of Cya and Cyb and the corresponding amount of change of the movable mirror 12.14 with respect to the x and y axes, that is, the amount of inclination θ and the amount of positional shift β in parallel are stored as a table. These data are prepared in advance by actual measurements using a precise photoelectric autocollimator or the like. Also, memory 5
6 shows the capacitors Cxa, Cxb, when the movable mirror 12.14 is set accurately against the stage 10).
Capacitance values, ie, initial values, of Cya and Cyb are also stored. The MPU 54 determines the tilt amount θ and the parallel shift amount β of the movable mirror 12.14 corresponding to the capacitance value f of the capacitors exa, Cxb, Cya, and Cyb inputted from the ADCs 46 and 52 from the table in the memory 56, and determines whether the values are applicable. , or data Lx and Ly containing the most approximate values θ and β, are output to the arithmetic circuit 20 (see FIG. 1).

Next, the overall operation of the above embodiment will be explained with reference to FIG. 4 as well. Figure 4 is axis A in Figure 1.
When viewed from the X direction, the movable mirror 12 has a parallel deviation from its normal state by an amount equal to θG, and is tilted within the x, y plane. In addition.

It is assumed that the movable mirror 14 is in a normal position.

In the state shown in FIG. 4, the capacitance of the capacitors Cya and Cyb becomes smaller as a whole due to the positional deviation β0 compared to the normal state. And then,
Depending on the slope θ0, the capacitance of capacitor Cyb changes to become smaller than Cya.

Therefore, the changeover switch 48 is alternately switched at appropriate timing by a control signal from the MPU 54.

The capacitance values of the capacitors Cya and Cyb are read into the MPU 54 as digital values. Incidentally, it is preferable that the cycle of switching the changeover switch 48 and reading data by the MPU 54 is performed successively regardless of the movement of the stage 10. Also, if necessary, capacitor C
The capacitance values of ya and Cyb may be read multiple times and the average of these values may be taken.

Next, the MPU 54 calculates the capacitance difference between the capacitors Cya and cyb, and obtains the slope amount θ0 corresponding to this deviation from a table stored in the memory 56.

Furthermore, the MPU 54 similarly determines the positional deviation amount β0 corresponding to the deviation E of the capacitance value of the capacitor CyajCyb from the initial value. These tilt amounts θ01 and positional deviation amounts are:
It is output to the arithmetic circuit 20 as data Ly indicating the amount of change.

Next, the arithmetic circuit 20 calculates which position in the X direction on the reflective surface 12A of the movable mirror 12 is irradiated with the laser beam LA. This can be easily determined simply by the operation of the arithmetic circuit 20 to read the position information Dx from the X-direction interferometer 18 (see FIG. 1).

Let us assume that the length of the movable mirror 12 is t, and consider that the laser beam LA is irradiated at exactly half the position of t.
The amount of deviation t=y in the X direction at the incident point of the laser beam LA on the reflective surface 12A is ・muy=bird+(t/2)81nθ
It is represented by (1). Therefore, when the stage 10 moves in the X direction and the laser beam enters the reflecting surface 12A at a position different from the half t position of the moving mirror 12,
When f is incident, the correction amount Δy in the X direction is Δy=βo +f (Dz)8inθo ”...
-----(2). In equation (2), f(DX) is a linear function whose variable is the position of the stage 10 in the X direction, and represents the point of incidence of the laser beam L4 on the reflective surface 12N. Note that since the amount of inclination θ0 is an extremely small value, there are 8 planes. ”. It can be approximated as

Therefore, the arithmetic circuit 20 calculates the accurate position Ty of the stage 10 in the X direction from the outputs of the interferometers 16 and 18 and the change detection circuit 30 using the following equation.

Ty=Dy-△Y=Dy-(β'o+f (Dx)!i
'o) ·---(3) The same applies to positional changes in the X direction. That is, the tilt amount ε0 of the movable mirror 14. Both parallel deviation amounts are read out from the memory 56 in response to changes in capacitors exa and Cxb, and the accurate position Tx of the stage 10 in the X direction is determined from the following equation.

TX:DX-b X=Dx-(αo+, !7(Dy)s
inεG)--(4) Next, other embodiments E, such as other variations or applications of the above-mentioned embodiments, will be explained.

First, as shown in Fig. 85, move the movable mirror 58 to sX*'1X
In this case, the capacitive sensor portions may be formed in an L-shape (this may be formed in one piece) in the direction, for example, at two locations PA and PB, which are the ends of the movable mirror 58 and are indicated by broken lines. It may also be provided.

Next, as shown in FIG.
Reflective surface 62.64 in a direction having an angle of 45° with the Y direction
The same effect can be obtained by forming capacitance sensor portions at the positions of PC and FD indicated by broken lines.

In the above example (also in this case), when the tilt of the movable mirror 58, 60 exceeds the allowable value, the optical axis of the reflected light returning to the laser interferometer tilts, and the S ratio in the interferometer decreases. , the reflected light will not return to the interferometer at all. Therefore, if position measurement using an interferometer is possible, the data should be corrected as in the above example, and if the operation of the interferometer becomes unstable, The operator issues an appropriate alarm, stops the operation of the exposure equipment, and readjusts the position of the movable mirror 58. In addition, the number of defective chips is reduced, and no defective chips are manufactured after the stoppage, which improves the throughput of IC and LSI manufacturing. If the capacity of the unit or the difference thereof exceeds a predetermined tolerance, an alarm may be issued or the system may be shut down.

The conductive film constituting the capacitor is divided into three, four, etc. for one movable mirror, and
A plurality of capacitors may be formed. By comparing the capacitances of the respective capacitors in this manner, position changes can be detected with higher accuracy. There are various methods for detecting the capacitance of these capacitors, such as a method using resonance by a resonant circuit, a method using phase comparison, and a method using a change in oscillation frequency. Any method may be used.

Furthermore, the change in position is not determined by a change in the capacitance of a capacitor (for example, a photoelectric micrometer may be provided in the stage, and the change in position of the movable mirror may be detected using this).

Furthermore, the present invention is not limited to exposure apparatuses and the like (but can also be applied to other apparatuses such as NC machine tools).

〔Effect of the invention〕

As explained above, according to the position change detection device according to the present invention, the position change of the movable mirror can be detected satisfactorily, and data can be corrected based on this.

This has the effect of allowing necessary measures such as issuing a warning to be taken promptly, thereby improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing a first embodiment of the position change detection device according to the present invention, FIG. 2 is a perspective view showing the detailed configuration of the device shown in FIG. 1, and FIG. FIG. 4 is a circuit block diagram showing the main part of the electrical configuration of the device, FIG. 4 is a transparent diagram showing an example of position change, and FIGS. 5 and 6 are perspective views showing other embodiments of the present invention. [Explanation of symbols of main parts] 10...Table, 12.14...Movement mirror,
12A, 14A... Reflective surface, 16.18... Interferometer, 30... Change detection circuit. Cxa, Cxb, Cy a, Cyb --- condenser, LA, LB... laser beam.

Claims (1)

[Claims] An optical member having a reflective surface on which a predetermined light beam is incident is installed on a moving body to be measured, and the light beam reflected by the reflective surface is incident on a light wave interferometer to measure the value of the moving body. A position change detection device for measuring a position change, comprising: a first detection means for detecting a relative positional deviation between the optical member and the movable body at each of a plurality of locations on the optical member; A position change detection device comprising: second detection means for detecting an inclination of the reflective surface by comparing detected positional deviations at the plurality of locations.