DE3143948A1 - "PHOTOELECTRIC METHOD AND RECEIVER ARRANGEMENT FOR DETECTING THE POSITION OF EDGE-SHAPED MEASURING STRUCTURES" - Google Patents

Description

Photoelectric method and receiver arrangement; for lape detection; edge-shaped measuring structures

The invention relates to a photoelectriachea method and an arrangement for detecting the position of edge-shaped measuring structures, which can have any orientation to a fixed reference system (coordinate system). use the invention finds z. B. in optical precision measuring devices (coordinate measuring machines) to objectify the positioning method in the coordinate directions x, y and γ, with one automatic measurement of moving, d. H. non-stationary structures is possible. Another field of application of the invention relates to the position detection of simple geometric structures on stencils or semiconductor chips in photolithography.

Photoelectric systems come in many forms for the Construction of photoelectric microscopes and measuring systems, but also used for object recognition and image analysis. In In the literature, especially in the field of photolithography, a large number of static and dynamic working Photoelectric methods and arrangements for determining the position of edges, but especially of line-shaped flat objects, described (e.g. in Optik 21 (1964) pp. 605 ff. and Wiss. Ztschr. Friedrich-Schiller-University Jena, Math.-Hat. R., Vol. 25 (1976) H. 5 p. 683).

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These procedures are often very complex or they meet the requirements made by the coordinate measurement, not complete (e.g. need for defined marks on the objects to be measured ^ pre-orientation for Measuring system).

Furthermore, devices for photoelectrically determining the position of an object are known in which an image pickup tube is used as a converter (WP 128637 DD). A suitable control of the deflection unit or twice scanning of the image in the x and y directions made in the image pickup tube. Suitable evaluation electronics determines the misalignment with respect to an ideal mark in the x, y and γ directions. The measuring time is <100 ms.

In addition, a method is known (OS 2405 102 DB) in which a line or edge-shaped structure with the help of a mechanical deflected and circular rotating point light probe is scanned. The measurement signals produced by a photo receiver are related to their phase position evaluated for the rotational movement for the determination of the angular position of the structure. The frequency analysis of the measurement signals delivers the tray to the rotation center.

The last two solutions mentioned are characterized by a dynamic measuring principle. The use of mechanical Deflection means limits the application of the method to quasi-stationary objects. But also the use of non-mechanical ones Deflection means (e.g. the use of image pick-up tubes) bring in because of the limited spatial resolution Problems with yourself. In the end, the two methods are likely to lead to considerable measurement errors in the case of non-ideal structures lead, since the structural location is not appropriate according to any of the generally recognized definitions of location. In OS 2102027 DB, a method is described that defines the edge location at the location of the maximum blackening gradient to measure an edge-shaped intensity profile.

For this purpose, the twofold derivative of the Intensity profile formed. This method is according to the invention however, can only be used for one or two (see OS 2017400 DB) preferred measuring directions.

The aim of the invention is a fast, objective and non-contact Acquisition of measured variables when measuring optically effective structures that are not necessarily stationary in view are based on a fixed reference system and which do not have to have a preferred orientation to this. Special In the case of optical precision measuring devices, in particular coordinate measuring devices with a digital measuring system, the invention is intended to be a higher positioning accuracy and measuring speed through the replacement of the still predominant visual positiomer method enable"

The invention is based on the object of a photoelectric To develop a method and a receiver arrangement, which are suitable for the position detection of optically effective, line-shaped or edge-shaped measuring structures, regardless of the visibility and achieve the aim of the invention. In case of coincidence of the sighted according to the photometric definition of the center Structure location should be a suitable control signal for a peripheral measurement electronics, ζ. B. the position output of a Measuring system, be derivable.

According to the invention, the object is achieved by a static photoelectric Method solved, which by a two-dimensional photometric evaluation of the radiation flux emitted by characteristic structural elements Determination of the position of the structure regardless of its orientation in a fixed reference system (coordinate system) with respect to an excellent target point (coordinate origin). The procedure is characterized by that the minimum and the maximum of the radiation flux in the immediate vicinity of the edge transition are optical can be recorded integrally two-dimensionally, the sum of these integral radiation fluxes either optically with a peripheral one Orifice surface (z. B. circular ring) is formed and a proportional electrical signal is derived or

an electrical summation of individual signal values takes place, whereby the individual signal values correspond to the partial radiation penetrating through several peripheral partial diaphragm surfaces proportional to aind and that furthermore the integral radiant flux of the edge transition from a central diaphragm surface is completely recorded and in turn a proportional electrical signal is obtained. Afterward a difference is made between the resulting electrical Signal values, the signals being preamplified according to the area ratio of the peripheral diaphragm area central panel surface are assessed. In the event that the areas are the same size, the pre-amplification can of course omitted.

The ITuIl passage occurring in the difference signal is preferably used used to display a defined relative position of the measuring structure and coordinate projection. The radiation fluxes emitted by the central and the peripheral diaphragm surface are either controlled by suitable ones Steel elements on two photoelectric receivers or they are combined and mapped onto a receiver via a beam interrupter (chopper process).

It is also within the meaning of the invention, the aperture surfaces by appropriately designed and arranged receiver surfaces To form photoelectric receivers, which can be manufactured integrated on a chip or as a hybrid structure. According to the invention, the photoelectric receiver arrangement contains at least one centrally arranged receiver surface and at least one peripheral receiver surface surrounding the central surface. The receiving surfaces are apart electrically isolated and the signals of the individual surfaces can be freely interconnected * The central receiver surface is preferably made circular or square, the peripheral receiver surface can be circular or consist of four separate sub-areas of the same shape, each sub-area having the same area as the central area has, or the total peripheral area is equal to the central area.

The receiver arrangement according to the invention allows in addition to Realization of the method for direction-independent probing of edge-shaped measuring structures through the free interconnection of all individual receiver surfaces also the realization the well-known two-cell difference method for probing line-shaped objects. Since that applied Method represents a static measuring method in principle, the arrangement can be particularly advantageous for measuring Use moving (non-stationary) measuring structures.

Some embodiments of the receiver arrangement according to the invention are described in more detail below with reference to a drawing.
Show:

Fig. 1a) Receiver arrangement consisting of five integrated square receiver diodes of the same dimensions

Fig. 1b) Receiver signal with edge capture by translation (f a 0 or 45 °)

Fig. 1c) Receiver signal with edge capture by rotation Fig. 1d) Receiver signal with line capture by translation

Fig. 2a) Receiver arrangement consisting of five integrated rectangular receiver diodes of different geometry

Fig. 2b) Receiver signal with edge capture by translation

3a) Receiver arrangement consisting of two circular receiver surfaces arranged centrally with respect to one another with the area ratio 1: 1

Fig. 3b) Receiver signal with edge capture

Fig. 3c) Receiver arrangement according to 2a with signal evaluation device for line capture within a target area

Fig. 3d) receiver arrangement consisting of three centrally arranged receiver surfaces

Fig. 3e) Receiver signal with line capture

Pig. 4) Receiver arrangement according to 2a, with both circular areas are divided into 4 equally sized sectors.

The receiver arrangement shown in Fig. 1a consists of five separate square receiver areas, the central area 1 "and four peripheral areas 11 ', 12', 13 ', 14 * with the side lengths a. This structure can be integrated on a chip or as a hybrid structure. The separation strips d between the receiver surfaces define the axes (x, y) of the coordinate system. When using this receiver in an optical coordinate measuring machine it is in an intermediate image plane or, for example, on the projection screen to arrange that its center lies in the target axis. As a rule, the optical axis of the measuring device is used as the target axis chosen.

The receiver type shown allows:

1. The derivation of a coincidence signal for the position-independent positioning of an optically effective edge to the origin of coordinates,

2. the derivation of a parallelism signal or overlap signal when the coincidence according to 1 is reached when rotating an edge with respect to the coordinate axes,

3. the derivation of a coincidence signal with the position-independent positioning of the photometric center of optically effective lines of width b. Here are strokes having a width b a + 2d b 3a + 2d to the coordinate origin and strokes with db 2a + d to a target point on the coordinate axes in a distance of ^1/2 (a + d) positioned from the coordinate origin (s. Pig. 1a),

4. the derivation of a coincidence signal with a distance of Y2 (a + d) running parallel to the coordinate axes Lines when rotating a stroke.

To 1. According to the invention, the edge positioning with the receiver according to Fig. 1a takes place in that:

* + *, n. 04 i - radiation flux on

Z ψ - M- φ = φ the areas

^ ^ü (11 ·, 12 ', 13', H ¹ )

(0 = 0 for coincidence) 0 '\ - radiation flux on

¹ the area 1 ^tf

The quadrupling of the radiation afluase becomes after the conversion achieved by corresponding amplification of the signal s (r, f) proportional to the radiation flux.

_Δ - signals of 11 ', ₄ ¹ ^' ⁴ .12, 13 ', H'

s ¹ ^ signal of 1 ''

- Coordinates of the ^K »ι edge location

When an edge-shaped structure located in any angular position to the coordinate axes is translated via the receiver, the signal profile that is characteristic of the method is obtained. In Fig. 1b, the difference _{signals s (r K} , vf) are shown for φ-, = 0 ° and f ₂ = 45 °. The receiver arrangement shown in FIG. 2a works according to the same measuring principle. The equality of the signal sum from the outer receiver surfaces 21 ', 22', 23 ', 24' and the signal from the inner receiver surface 2 '' with full illumination of all receiver surfaces is shown here by the equality of the surface sum from 21 ', 22', 23 ' , 24 'and the surface 2 ¹¹ reached.

Fig. 2b shows the characteristic signal curves s (r ^, »p). Regardless of the angular position of the edge to the coordinate axes, the difference signal of the two embodiments has Coincidence of the edge with the coordinate origin of a pass through the envelope.

• •• on «

Ü β mo

• · O »4 O

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At this moment, the edge becomes half of the total area of the outer recipient surfaces and half of the inner recipient surface are darkened and the Differential signals

according to Fig. 1b or

f ⁵ U Cr _Kl t) - ^ S ₁ "Cn ₁₁ If") = 0

according to Fig. 2b.

The capture range in the coordinate direction is given by

B _xy = 2 (a ' ₁₊ d) + a ".

(The capture area B indicates the dimension of the area on the receiver arrangement for which s (r _k , ^) Φ Ο.)

The sensitivity is, if the external dimensions are the same (circumscribed circular area), with the same area Structure according to Fig. 1a larger than that of Fig. 2a.

For both receivers, the sensitivity increases when the angle of the edge to the coordinate axes (separation strips) increases from 0 ° to 45 °.

Regarding 2. Both receiver arrangements can still be used simply to indicate the coincidence during rotation (edge parallel to the coordinate axis). For this purpose, the z. B. in the arrangement according to Fig. 1, 11 'and 13' or 12 'and 14' switched in difference. The difference aial

s (s, 90 °) = s _'12 (x, 90 °) - s' ₁₄ (x, 90 °) or s (y, o) = s '^ iy.o) - s' ₁₃ (y, O)

be hull when the above excellent angles locations can be achieved.

Q
= a rc tan 2Γ ¹ " for h ^ I = arctan _Λ xj
1 + 2d f Ur h «ο

Achieving the coincidence position to a coordinate direction requires positioning according to point 1. The history the difference signal is in Pig. 1c. The limit angle of the capture area is generally given by

Max

or t _m ax ^{= av0} ^ ^an T + 2cT ^for ^ = O (coincidence)

h - distance of the edge from the origin of the coordinates

in coordinate direction 4 * mov ~ critical angle of the capture area edge to

Coordinate direction

Re 3: The indication of the nominal position of a line can advantageously be carried out with the detector according to FIG. 1a (receiver sub-areas of the same size). The static two-cell difference method is used for this. Optionally, the receiver surfaces 11 ', 12', 13 ', H ^{1 can be switched} with the surface 1 · · in difference, z. B. Use of the zero crossing of the difference signal

s (x) = s _'12 (x) - S ₁ ' ^! (x)

s (y) = S ^ ₁₁ (X) - S ^ '(χ)

for small line widths (s c b <. 2a + d) or

s (x) = s _'12 (x) - s' _u (x)

x (y) = s * ii (y) - a '"(y)

for line widths a + 2d <b <3a + 2d.

3 U 39

The Kull passage is for a specific pair of receiver surfaces in the range of 0 ° ^ f ^ 45 ° independent of the rotational position. For larger angles, measurements must be made in the other coordinate direction.

In Fig. 1d) is the course of the signals as a puncture from Location of the photometric line center shown.

Regarding 4, " Provided that the line has been positioned as per point 3", it is possible to derive a coincidence signal when the coordinate directions are reached by switching the partial areas of the receiver according to point 2.

In Pig. 3a is a further receiver arrangement for direction-independent Edge probing shown. It is characterized by being independent of the orientation of the edge Sensitivity off. ,

The arrangement consists of a circular receiver surface and a second circular ring-shaped receiver surface arranged concentrically to the center of the circle. Both receiver surfaces are to be coated in such a way that the electrical signals emitted by them are proportional to the incident light flux and are then subtracted. Facilities for this are known (see e.g. AS 1957 161 DB) and do not require any further explanation. According to the invention, the radius length is to be selected so that the circular ring surface 31 'becomes equal to the circular surface 3''. Neglecting the dimensions of the separation width d between the two receiver surfaces, this is the pail at r., = Y2r.

Moves now like in Pig. 3a indicated an edge-shaped Structure The in Pig. 3b indicated difference signal curve. It can be seen that when the edge coincides with the center of the Receiver arrangement a Uullsi £ inal arises, which is in

Yc

advantageously exploit to trigger a length measurement system leaves. In this state, half of the reception area is darkened by the edge-shaped structure or illuminated, so that assuming the same receiver sensitivity, the difference between the receiver signals is UuIl.

The analytical relationship between edge location r ^ and difference signal s (x) results from a separation width dtsO

-So [it (ore ccs ^ -ürtcos ^ + Γ _Λ (l / * -

S _{D is} the sensitivity of the receiving material and E is the illuminance in the bright part of the edge transition. (EaO was assumed for the dark rope of the Eante.) For the receiver sensitivity of the arrangement near the Uull passage (point of coincidence), z. B. with the values: E = 1500 Ix, S ^ = 4.2 mA / lm and T ^ = 100 around a value of

Because the dark current of the underlying receiver material with element operation is approx. 0.07 nA, deviations of less than 1 µm are safe with ideal structures (maximum contrast) verifiable.

The rotational symmetry of the receiver arrangement causes a Completely direction-independent sensitivity of the arrangement. The target axis is defined by the center of the circle. The arrangement can be particularly advantageous for measuring Use moving (non-stationary) edge-shaped objects. As a continuation of the inventive concept, an arrangement proposed, which enables the registration of a line-shaped structure within a predetermined target range.

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For this purpose, when using the receiver type proposed in FIG. 3a before the registration of the differential photocurrent daa originating from the circular ring receiver signal electronically by a factor of 4r3x (e.g. 2.5x) (Pig. 3c). According to the invention, however, the same effect is also achieved Adding a further, peripheral to the first circular ring surface arranged, second circular ring surface is achieved (Pig. 3d). The receivers are to be shelled in such a way that the resulting Total signal s with that of the receiver part

total

signals originating from surfaces is linked via the following relationship:

s _ges (r, Y> = s " ₃ (r, f) - / f" (s _'31 (r, if) + s' ₃₂ (r, »f) _7

The s switch can be used to switch to edge loading (switch position a).

s (r) «S (k)

s (r) = S (r _a )

s

If the radius r "(again neglecting the parting line) is selected to be somewhat smaller than twice the radius of the circular receiver r, the signal curve given in FIG. 3e results when a line-shaped structure passes over the receiver characterized in this way. For the line width b, b ₁ ^ b ₂ L \> y applies

It can be seen that symmetrically to the point of coincidence (ie the middle of the line is in the target axis) there is a double Hull crossing of the signal voltage «. The distance of these Uull crossings from the target axis is independent of the line width in the first approximation and is only determined by the selected radius r _g (or the amplification factor of the signal amplifier). The closer the gain factor to the value 3 (or the radius ratio the V / ert r _p / r β 2), the closer the liull passages come to the target axis, but the smaller they become

tive signal components, so that reliable registration of the Hull crossings is no longer guaranteed. With the proposed arrangement, it is thus possible to capture a line-shaped structure in a predetermined target area. For example, for r ^ 75 / _{um and r 2} ^ 140 / um a target range of + 30 um, or for r _Q 71 / um and r "» 140 yum a target range of + 10> um.

In this application, too, the measurement of moving objects is possible thanks to the implementation of a static measuring method possible without difficulty.

The arrangement represents a further advantageous embodiment according to Fig. 4.

This receiver arrangement is particularly useful for positioning the photometric center of a line to a target point. To do this, the sectors are paired in Difference switched that the receiver signal according to the relationships

s (r, f) = s' ₄₁₊ s' ₄₂₊ s'_{"45 +} s · _'46 - (s' + s _{43' 44+} · s' + s · ₄₇ ^)

for 45 ° * It I 4 90 ° resp.

s (r _,? ) = s' ₄₁ + d '44 ₊ s'' ₄₅₊ s' « ₄₈ - (s' ₄₂₊ s' ₄₃₊ s''^ + s ^ ₄₇ )

for 0 ° C I vf | ± 45 °

is formed.

The separation strips define the axes of the coordinate system.

The zero crossing of s (r, ip) shows the coincidence of the photometric line center with the detector center. The same circuit is used to indicate the coincidence of an edge with the coordinate axes during rotation.The coincidence of a line (photometric center) with the coordinate axes during rotation is determined by the fulfillment of the condition a '^ (r, <f) - s' ^ r ^) = 0 and s _'42 (r, f) - s' ₄₃ (r, ^) = 0 displayed.

19 14

The latter two applications require and positioning on the coordinate origin. The order can also be used to directly determine the angular position of a line can be used for the coordinate direction. For this purpose, when moving the object in the χ direction z. B. the receiving surfaces 41 'and 44' and the receivers 42 'and 43' as a difference switched, the Uull passages of the two difference signals registered and from the corresponding path coordinates the angle is calculated.

2 (r + d) + r- - r - d

* f- = arctan 2! 2

Δ χ

The positioning of an edge can be done by using of an education law, which according to the recipient order Fig. 3 corresponds to take place.

Because of the parting line, angular positions * f = 0 ° and ^ f = to be avoided (lower measuring accuracy).

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Claims (25)

3U3948 patent application 1.J]? Otoelectric method for the location detection of edge-shaped measuring structures by means of a two-dimensional photometric evaluation of the radiation emitted by characteristic structural elements, characterized in that the minimum and the maximum of the radiation in the immediate vicinity of the edge transition optically independent of the orientation in a coordinate system ₉ the sum of these integral radiation fluxes is either formed optically with a peripheral diaphragm surface and a proportional electrical signal is derived or an electrical summation of individual signal values is carried out, the individual signal values being proportional to the partial radiation fluxes passing through several peripheral diaphragm sub-surfaces entire radiation flux, influenced by the change in intensity of the edge transition, is completely absorbed by a central diaphragm surface, for this purpose in turn proportional electrical signal is obtained and that the difference between the resulting electrical signal values is then formed, whereby the electrical signals are evaluated by pre-amplification according to the area ratio of the peripheral diaphragm surface to the central diaphragm surface and preferably the disappearance of the difference indicates a defined relative position of the measuring structure and the origin of the coordinates « Method according to claim 1, characterized in that the diaphragm surfaces by appropriately designed and arranged Receiver area photoelectric receiver are formed and the course of the electrical output from them Signals the presence of a certain relative position of the measuring structure or its coincidence with the origin of coordinates indicates. 3. The method according to item 1, characterized in that the Radiation fluxes emitted by the central and the peripheral diaphragm surface through suitable beam guiding devices Elements are directed to two photoelectric receivers. 4. Method according to claim 1, characterized in that the two radiation flues combined by radiation-guiding elements be mapped to a photoelectric receiver via a beam interrupter and the size of the the alternating electrical signal emitted by these signals the presence of a certain relative position of the measuring structure and Shows the origin of coordinates. 5 · Photoelectric receiver arrangement for carrying out the Method, characterized by at least one centrally arranged receiver surface and at least one the central surface surrounding peripheral recipient surface, the Receiver surfaces are arranged electrically isolated from each other and the signals of the individual surfaces are freely interconnected are cash. 6. Arrangement according to claim 5, characterized in that the arrangement is monolithic. 7. Arrangement according to claim 5, characterized in that the arrangement is constructed hybrid. 8. Arrangement according to claims 5 to 7, characterized in that that the peripheral receiving surface consists of at least four separate partial surfaces of the same shape, wherein each sub-area has the same area as the Has central surface. 9. Arrangement according to claims 5 to 8, characterized in that the arrangement consists of a square central surface (1 ¹¹ ) and four with (1 ^fl ) identical peripheral receiver surfaces (11 ^f , 12 ', 13', H ^! ). 10. The arrangement according to claim 9, characterized in that the measurement signal according to claim 1 by an electrical summation of the signals S ¹ - generated by the peripheral receiver surfaces (11 ', 12', 13 ', 14'). _Λ . and I I · · · 14 subsequent subtraction of the sum signal and the signal S ' ¹ - generated by the central surface and amplified by the factor. 11. The arrangement according to claim 9, characterized in that the measurement signal by using the from the respective opposite peripheral receiver surfaces (12 ') and (14') or (11 ') and (13') originating signals in accordance with the relationship s (r , ^ f) = s _'12 (r,> f) - s' .. ^, ^) or s (r, vf) s = a '^ ir, ^) - 8 ^ι ^ Λτ, γ) is formed. 12. The arrangement according to claim 9, characterized by a differential circuit of opposite peripheral receiver surfaces or the differential circuit of a peripheral receiver surface with the central receiver (1V ¹ ). 13. Arrangement according to claims 5 to 7 »characterized in that that the peripheral receiving surface consists of at least four separate partial surfaces of the same shape, whose total area is equal to the central area. 14. The arrangement according to claim 13, characterized in that the arrangement consists of a square central receiver surface (2 ') and four rectangular peripheral receiver surfaces (21'), (22 '), (23'), (24 '), the The sum of these receiver areas is equal to the receiver area (2 ¹ ). 15. The arrangement according to claim 14, characterized in that the measurement signal generation according to claim 1 by an electrical summation of the signals S ' _o - emanating from the peripheral receiver surfaces (21'), (22), (23 '), (24') _nA and subsequent subtraction of the sum signal and that of the central surface (2 '') 1" generated signal S ¹¹ O takes place 16. The arrangement according to claim 14, characterized in that the measurement signal is obtained in accordance with claim 11. 17. Arrangement according to claims 5 Ms 7, characterized in that the arrangement consists of a circular central receiving ^{surface (3 ir} ) and an annular receiving surface (3 ¹ ) surrounding this surface. 18. The arrangement according to claim 17, characterized in that the measurement signal according to claim 1 by differential circuit of both receiver surfaces is generated. 19. The arrangement according to claim 18, characterized in that generated by the annular receiving surface
Signal is amplified by a factor of 3. 20. The arrangement according to claim 17, characterized in that the arrangement is arranged peripherally by a second
circular receiver surface (32 ') is added, the outer radius of which may be a maximum of twice the central circular receiver surface (3''). 21. Arrangement according to claim 20, characterized in that the measurement signal is generated by forming the difference between the signal sum between the signals emanating from the receiver ^{surfaces (31 ') and (32') and the signal from the receiver surface (3 tf} ). 22. Arrangement according to claim 17, characterized in that both the central receiving surface and the peripheral Circular ring receiver area in four equally large sector receiver areas that are electrically isolated from one another are divided. 23 «Arrangement according to claim 22, characterized in that the measurement signal by the combination of the signals Claim 18 is generated. 24 · Arrangement according to claim 22, characterized in that the measurement signal is generated by forming the difference between the sum signals emanating from the sector receiver surfaces separated by separating strips. 25. The arrangement according to claim 22, characterized in that two measurement signals simultaneously by differential switching of two sectors, for. B. (41 ') and (42 ¹ ) and (43') and (44 '), the circular ring receiver surface can be obtained.