WO2010136330A1

WO2010136330A1 - Measuring a substrate having electrically conductive structures

Info

Publication number: WO2010136330A1
Application number: PCT/EP2010/056451
Authority: WO
Inventors: Fatih Alatas; Martin KÖRDEL; Anton Schick
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-05-28
Filing date: 2010-05-11
Publication date: 2010-12-02
Also published as: EP2435840A1; DE102009022965A1

Abstract

The invention relates to a method and an apparatus for measuring a substrate (1) having electrically conductive structures (2, 3). In order to improve such a measurement, it is proposed for the apparatus to comprise a measurement sensor (4) and means (5) for a targeted movement of the measurement sensor (4) relative to the substrate (1), wherein the apparatus comprises means (6, 7) for simultaneously feeding several different electrical signals in the electrically conductive structures (2, 3), wherein the measurement sensor (4) is provided to measure fields generated by the electrical signals by way of field coupling, wherein the apparatus comprises means (8, 9, 10) for analyzing the measured fields and for determining properties of the electrically conductive structures (2, 3) on the basis of the analysis of the measured fields.

Description

Measurement of a substrate with electrically conductive structures

The invention relates to a device and a method for measuring a substrate having electrically conductive structures. The device has a measuring sensor and means for controlled movement of the measuring sensor relative to the substrate.

DE 10 2005 022 884 A1 describes a method for contactless inspection of a printed conductor structure formed on a planar support, in which an electrode is positioned at a predetermined distance relative to the printed conductor structure by means of a positioning device and an electrical connection between the electrode and the printed conductor structure Voltage is applied. The electrode is moved in a plane parallel to the carrier, wherein at least at selected positions, a current flow is measured by an electrical line connected to the elec- rode. From the strength of the current flow, the local stress state is detected in a subregion of the conductor track structure. This stress state can be used to determine the quality of the trace structure. Thus, defects such as short circuits, constrictions or line breaks generated by geometrical changes in the printed conductor structure can be detected.

The invention has for its object to improve the measurement of a substrate with electrically conductive structures.

This object is achieved by a device for measuring a substrate having electrically conductive structures, the device having a measuring sensor and means for controlled movement of the measuring sensor relative to the substrate, wherein the device has means for simultaneously feeding a plurality of different electrical signals into the electrically conductive structures , where the measuring sensor is used tion of fields generated by the electrical signals is provided by means of field coupling, the device having means for evaluating the measured fields and for determining properties of the electrically conductive structures based on the evaluation of the measured fields.

This object is achieved by a method for measuring a substrate having electrically conductive structures, in which a measuring sensor is moved in a controlled manner relative to the substrate, in which a plurality of different electrical signals are simultaneously fed into the electrically conductive structures, in which case the measuring sensor is triggered by the electrical signals generated fields by means of field coupling and in which the measured fields are evaluated and properties of the electrically conductive structures on the basis of the evaluation of the measured fields are determined.

The invention is based on the idea of introducing a plurality of different electrical signals into electrically conductive structures of a substrate and of measuring and evaluating the fields produced by these different electrical signals by means of field coupling and of using them to determine properties of the electrically conductive structures. Since several different electrical signals are fed simultaneously, several different electrically conductive structures can be examined simultaneously. This allows a considerable acceleration of the measurement. The controlled movement of the measuring sensor relative to the substrate can be effected by a movement of the measuring sensor itself and / or by movement of the substrate relative to the measuring sensor.

Advantageous embodiments of the invention will become apparent from the dependent claims.

According to an advantageous embodiment of the invention, the measuring sensor for measuring electrical fields generated by the electrical signals by means of capacitive field coupling intended. This allows a particularly simple non-contact measurement of the fields generated by the electrical signals.

In order to simplify the evaluation of the measured fields and the determination of properties of the electrically conductive structures on the basis of the evaluation of the measured fields, it is proposed according to a further advantageous embodiment of the invention that the means for the simultaneous feeding of several mutually phase-shifted periodic electrical signals in the electric conductive structures are formed. The fields generated by such type of mutually phase-shifted periodic electrical signals superimposed in such a way that in particular a reliable statement about the location of the source of electric fields, and thus on the location of the electrically conductive structures, is possible. The superposition of stationary phase-shifted electrical signals leads to a phase modulation of a signal which is recorded by a measuring sensor when this measuring sensor is moved uniformly over the emitting, electrically conductive structures. On the basis of the phase position of the resulting signal and on the basis of the respective amplitude of the signal conclusions about the electrically conductive structures can be made in a simple way se.

Particularly advantageous is an embodiment of the invention, according to which the means for the simultaneous feeding of two by 90 ° and / or of three by 120 ° to each other phase-shifted periodic electrical signals are formed in the electrically conductive structures. This leads to a particularly good signal separation with almost constant high signal strengths.

In order to also be able to determine properties of a substrate substrate, according to a further advantageous embodiment of the invention, the means for feeding an electrical signal into a base of the substrate are formed, in particular in particular a periodic electrical signal having a frequency which is different from frequencies of the plurality of mutually phase-shifted periodic electrical signals.

In order to avoid an unwanted influence of more than two electrical signals, in particular an extinction, it is proposed according to a further advantageous embodiment of the invention that the measuring sensor is designed for the simultaneous measurement of fields generated by a maximum of two electrical signals by means of field coupling.

The invention will be described in more detail with reference to the embodiments illustrated in the figures and explained.

Show it:

1 shows a device for measuring a substrate with electrically conductive structures,

2 shows an inspection system for electrically conductive structures on planar substrates,

3 shows a schematic representation of a sensor for measuring a substrate,

4 shows a schematic representation of a measurement of a plurality of phase-shifted signals,

5 shows the effect of different electrically conductive

Structures on a measurement result, and

6 shows the cancellation of a measurement signal by appropriate selection of the injected signals.

1 shows an embodiment of a device according to the invention for measuring a substrate 1 with electrically conductive border structures 2, 3, for example, electrical lines, tracks or electrically conductive surfaces. The device has a measuring sensor 4 and means 5 for the controlled movement of the measuring sensor 4 relative to the substrate 1. The device further comprises means 6, 7 for the simultaneous feeding of a plurality of different electrical signals in the electrically conductive structures 2, 3. In this case, the measuring sensor 4 is provided for measuring fields generated by the electrical signals by means of field coupling. Depending on the local position of the measuring sensor 4 above the substrate 1, different capacitive couplings to the individual electrically conductive structures 2, 3 are formed. That is, signals on the individual electrically conductive structures 2, 3 couple differently depending on the local structure strong to the sensor surface of the measuring sensor 4 a.

The device also has means 8, 9, 10 for evaluating the measured fields and for determining properties of the electrically conductive structures 2, 3 on the basis of the evaluation of the measured fields. The measuring sensor 4 is mounted on a support 12, for example made of glass, and surrounded by a shield 11, which is at a reference potential, in particular at ground potential. The measuring sensor 4 is kept at a constant potential, in particular ground potential. A measuring sensor 4 is also called a measuring electrode.

The measuring sensor for measuring by means of field coupling is not a classical field sensor, since influencing the original field by the measuring sensor itself is quite desirable. Measured z. B. capacitive Umladeströme or field-induced currents.

In embodiments of the measuring or inspection method according to the invention, the measuring process takes place via an inductive or capacitive field coupling. The simultaneous and high-quality measurement of several coupling fields and the simultaneous assignment of these field couplings to the individual coupling conductors is made possible. An invented The device according to the invention can be part of non-contact inspection or measuring systems for substrates with electrically conductive structures. Embodiments of the invention make use of the capacitive coupling between a measuring electrode and the lines or pixel areas of LCD substrates.

2 shows an embodiment of a device according to the invention, which is used to measure a display 20. The display 20 has individual pixels 32, which are shown in the enlarged representation indicated by the reference numeral 28. A pixel 32 has a TFT element 27 (TFT = Thin Film Transistor) and a pixel capacitance 33, respectively. In addition, the display 20 includes various electrically conductive structures 29, 30, 31. These electrically conductive structures are gate lines 29, Com, Bias, or

CS-lines 30, as well as data lines 31. For measuring the display 20, a measuring electrode 21 is provided, which can be moved by corresponding means 22 over at a constant distance over the substrate of the display 20. Means for simultaneously feeding a plurality of different electrical signals into the electrically conductive structures 29, 30, 31 of the display 20 are provided by way of a terminal strip 25. In this case, the means for feeding in are a frequency generator 24. Location-dependent capacitive couplings are formed between the measuring electrode 21 and the substrate surface. This situation is exploited by feeding suitable signals into the electrically conductive structures 29, 30, 31 for signal modulation. For example, with two sine waves on the lines that have the same frequency and amplitude but different phase angles. These would virtually phase encode the substrate lines and areas. Corresponding to the position above the substrate, a new signal then results in the measuring electrode 21, which is composed of the respective couplings of the line signals. When traveling over the substrate, the composition of the measurement signal on the measuring electrode 21 changes continuously according to the substrate structure. This steady change is a signal modulation. In the case of different phase This is a phase modulation resulting from the nature of the substrate surface. Scanning across the substrate would thus provide a phase and amplitude modulated measurement signal. By appropriate demodulation can then be deduced back to the substrate structure. The evaluation of the signals of the measuring electrode 21 takes place in the case shown by an electronics 23 and a computer 26. The modulation takes place by the changing coupling sizes, ie when driving with the measuring electrode on the substrate. At every defined position of the measuring electrode above the substrate there is also only one defined resulting measuring signal.

FIG. 3 shows parts of an exemplary embodiment of a device for measuring a substrate 1 with electrically conductive structures 2, 3. A measuring sensor 4, which is applied to a carrier 12, is shown. The measuring sensor 4 is surrounded by a shield 11, in this case designed as a ground plane. Furthermore, an amplifier circuit 8 is shown, which amplifies the signals output by the measuring sensor 4 and forwards them to means for evaluation, which are not shown in FIG. FIG. 3 serves to explain the possible sensor signals as a function of the signals applied to the conductive structures 2, 3. These periodic signals are each represented by a phase diagram 30, 31,

32 shown. The symbolized by the phase diagram 31 periodic electrical signal is thereby fed into the conductive structure 2. It is in this case a periodic signal with the phase 0 °. A second periodic electrical signal, symbolized by the phase diagram 31, which is phase-shifted with respect to the first signal, is fed into the electrically conductive structure 3. The phase shift in this case is 90 °, ie also that the phase position of the second signal fed into the electrically conductive structure 3 is 90 °. The amplitude of both signals 31, 32 is as shown in the unit circle 1. In the phase diagram 30 possible sensor signals of the measuring sensor 4 are reproduced. The actual Sensor signal depends on the position of the measuring sensor 4 with respect to the electrically conductive structures 2, 3 or the substrate 1. The phase angle of the sensor signal can move in the case shown between 0 ° and 90 °. The amplitude is maximum, if exactly one signal maximally couples into the measuring sensor 4, ie in this case at the phase position 0 ° - for a coupling solely by the electrically conductive structure 2 - or at the phase position 90 ° - for a coupling alone of In the case of a coupling of both electrically conductive structures 2, 3, a phase position between 0 ° and 90 ° results for the resulting sensor signal and an amplitude <1, indicated by the triangle shown in the phase diagram 30.

4 shows a sensor surface 4, which is moved at a constant distance d via electrically conductive structures 2, 3. In this case, a periodic signal, in this case a sinusoidal signal, with the phase 0 ° is fed into the electrically conductive structure 2. In the electrically conductive structure 3, a phase-shifted by 120 ° in the periodic electrical signal, including a sinusoidal signal, is fed. The signal curves identified by the reference numeral 40 show three sinusoidal oscillations phase-shifted by 120 °, with only two of these three signals being fed into the electrically conductive structures 2 and 3 in the exemplary embodiment shown here. The resulting sensor signal, which is supplied by the measuring sensor 4, is shown as a waveform 41. The signal course 41 shows the resulting time signal during the movement of the measuring sensor from a position over the electrically conductive structure 2

(Phase position 0 °) to a position above the electrically conductive structure 3 (phase position 120 °). In the phase diagrams 42, 43, 44 the resulting phases and amplitudes for three times of the sensor signal 41 are shown. The triangle in each case represents the achievable value range in the three phase positions sketched by way of example. The phase of the output signal of the measuring sensor 4 is dependent on the respective coupling capacitances between the sensor surface and the electrically conductive structures 2, 3. Thus, the phase range of the output signal is specified by the applied sine waves. The modulation corresponds to the changes in the coupling capacitances under the sensor surface. This means that the modulation frequency depends on the travel speed and the electrically conductive structures 2, 3. From the resulting phase can then the coupling capacity ratios to the electrically conductive

Structures 2, 3 are determined. From these, the respective proportions of the electrically conductive structures 2, 3 can be derived below the measuring sensor 4.

In addition to the phase modulation, an amplitude modulation also takes place (see top picture with signal curves), but the amplitude is also dependent on the capacity ratios. The maximum amplitude can only be achieved if only one signal is injected. The coupling of more than one signal automatically leads to a lower maximum amplitude. Therefore, the achievable value range in the phase diagram is also a polygon and not a circle. If required, this attenuation of the amplitude can be corrected again by evaluating the phase information.

Furthermore, the amplitude depends on the total size of the coupling capacitances. This means that the (corrected) amplitude can be used to deduce the total signal area under the sensor surface. Thus, with only one scan, the electrically conductive structures and their proportions, which are located simultaneously under a sensor surface, can be determined.

The feeding in of signals with two or three different phases is advantageous. Thus, for example, in the case of LCD substrates, the gate, data and com lines (if Com are present) and, in the case of (photo) detectors, the lines for gate, date and bias can be inspected simultaneously. Additive- It is still advantageous to apply a coded signal to the underlay (chuck) under the substrate. Thus, also unconnected electrical surfaces, via the capacitive coupling to the pad, be inspected. For this purpose, in addition, the use of a different frequency of advantage, since of the pad a much weaker coupling is expected.

FIG. 5 illustrates the dependence of the amplitude of a sensor signal on the respective conductive structure 2, from which a coupling-in signal is received. In each case, a substrate 1, optionally with an electrically conductive structure 2, is shown. Furthermore, a measuring sensor 4, which is applied to a carrier 12 and surrounded by a shield 11, is shown. The measuring signal of the measuring sensor 4 is forwarded to an amplifier circuit 8. The resulting measurement signal is represented in each case by a phase diagram 50, 51, 53. The phase diagrams 52, 54 reproduce the respective periodic electrical signals fed into the conductive structure 2. In this case, therefore, a periodic electrical signal having the phase position 0 ° and an amplitude of 1 in the unit circle is fed into the electrically conductive structure 2. Depending on the ratio of the extent of the electrically conductive structure 2 to the extent of the measuring sensor 4, the fed-in electrical signal couples differently into the measuring sensor 4, resulting in a measuring signal 51, 53 having a different amplitude. In the case of a non-existent supplied electrical signal, the amplitude of the measurement signal 50 is naturally equal to zero.

FIG. 6 shows by way of example how the measurement signal can be canceled out by a wrong choice of the phase difference and by the action of three phase positions and thus can not be distinguished from a free area. Shown again is in each case a substrate 1 with electrically conductive structures 2, 3 or 68, as well as a measuring sensor 4 located on a support 12, which is protected by a shield 11 is surrounded. The measuring signal of the measuring sensor 4 is transmitted to an amplifier 8. The periodic electrical signals fed into the respective conductive structures 2, 3 and 68 are represented by the phase diagrams 61, 62 and 64, 65, 66, respectively. The resulting measurement signals are reproduced in the phase diagrams 60, 63, 67. In the first case shown in FIG. 6, two periodic electrical signals are input, which have a phase shift of exactly 180 °. If the measuring sensor is located in a corresponding position above the electrically conductive structures 2, 3, ie in a position in which both signals are equally coupled into the measuring sensor 4, then the two signals shifted by 180 ° are effectively canceled out. That is, the resulting measurement signal is zero (see phase diagram 60). When using two phases they should therefore have a phase difference of 90 ° to each other. In this case, these two signals do not influence each other. In addition, a quadrature amplitude demodulator (QAM demodulation) with 90 ° phase difference of the signals directly supplies the respective coupling sizes.

In the second case illustrated, three conductive structures 2, 3, 68 are present, into which periodic electrical signals are fed, which are each shifted in phase by 120 ° in phase (see phase diagrams 64, 65, 66). In the event that the measuring sensor 4 is in a position relative to the electrically conductive structures 2, 3, 68, in which the three coupling-in signals equally coupled, cancel the signals phase-shifted by 120 °, resulting in a measurement signal equal Zero. When using three phases, they should each have 120 ° to each other. Thus, two signals can always be decoded and have the greatest possible phase separation from each other. As a matter of principle, more than two signal couplings can not be decoded independently of each other via the phase modulation. In the case of the three phases, when all three phase positions are coupled in, the above-mentioned mutual influences occur. In the case of 120 ° Phase distances in the form of attenuation of the signal. If the amplitudes of all three phase positions are equally strong, the signal is canceled out. Ie. During the measurement, it should be ensured that not more than two signals can merge appreciably at a time. This can be achieved, for example, with a correspondingly small sensor electrode area of the measuring sensor 4, which measures only two electrically conductive structures in the diagonal or the diameter.

The triangle in the phase diagram 63 indicates possible measurement signals during further movement of the measuring sensor 4 relative to the substrate 1 and thus relative to the electrically conductive structures 2, 3, 68. In the third example shown in FIG. 6, there is no electrically conductive structure on the substrate 1 to be measured, so that a measurement signal likewise results in zero (phase diagram 67).

The idea underlying the invention is thus the targeted signal modulation by field coupling by means of individual coded conductors. The line coding takes place via the creation of defined signals. Based on this, the phase and amplitude modulation as well as modulation types based on this can be adapted to this method. However, the greatest benefit lies in the implementation of the phase modulations described above.

In the case of phase modulation, the frequency modulation can be used to detect changes in the field couplings (edge detection of the substrates).

In principle, the application of this method is not limited to the measurement and inspection of substrates. It is also a technique that can be used for field coupling measurements, both capacitive and inductive, where information about coupling strength or coupling ratios is needed. The benefits of modulating through field coupling include:

- Better signal-to-noise ratio (SNR).

- All lines are on high amplitude signals. - The phase modulation results in a band spread, which further improves the SNR.

- With one measurement several lines can be detected, assigned and inspected in better quality.

- Due to the high SNR, higher scanning speeds are possible.

- Due to the phase modulation, all signal lines are equally influenced by the frequency behavior of the DUT, so that the method is robust against misdetections. - In phase modulation, all signals have the same

"Carrier frequency", so only one frequency has to be filtered.

- With the travel speed can be discussed on the modulation bandwidth, which can be scaled between quality and speed.

- The lines can also be supplied with additional signals if they do not fall into the modulation range in the frequency range. For example, in the case of LCD displays, the transistors can be permanently switched on or off by applying a direct current voltage. This allows more and more accurate inspection options.

This method can be used in the measurement and inspection of electrically conductive structures. Examples include: substrates for LCD / LCD TFT televisions and monitors, (photo) detectors, organic structures such as electronic newspapers, printed circuit boards of various kinds.

It is advantageous in particular for the qualitatively better and faster inspection of the printed conductors and surfaces on planar surfaces (eg glass or plastic substrates), the functional testing of simple circuits (switches TFT to pixel) and other similar measurement and inspection tasks.

The invention thus relates to a method and a device for measuring a substrate 1 with electrically conductive structures 2, 3. In order to improve such a measurement, it is proposed that the device comprise a measuring sensor 4 and means 5 for the controlled movement of the measuring sensor 4 to the substrate 1, the device comprising means 6, 7 for simultaneously feeding a plurality of different electrical signals in the electrically conductive structures 2, 3, wherein the measuring sensor 4 is provided for measuring fields generated by the electrical signals by means of field coupling, wherein the device Having means 8, 9, 10 for evaluating the measured fields and for determining properties of the electrically conductive structures 2, 3 based on the evaluation of the measured fields.

Claims

claims

1. Device for measuring a substrate (1) with electrically conductive structures (2, 3), the device having a measuring sensor (4) and means (5) for controlled movement of the measuring sensor (4) relative to the substrate (1), wherein the device comprises means (6, 7) for simultaneously feeding a plurality of different electrical signals into the electrically conductive structures (2, 3), wherein the measuring sensor (4) is provided for measuring fields generated by the electrical signals by means of field coupling, the device comprises means (8, 9, 10) for evaluating the measured fields and for determining properties of the electrically conductive structures (2, 3) on the basis of the evaluation of the measured fields.

2. Apparatus according to claim 1, characterized in that the measuring sensor (4) is provided for measuring electrical signals generated by the electrical signals by means of capacitive field coupling.

3. Apparatus according to claim 1 or 2, characterized in that the means (6, 7) for the simultaneous feeding of a plurality of mutually phase-shifted periodic electrical signals in the electrically conductive structures (2, 3) are formed.

4. Device according to one of the preceding claims, characterized in that the means (6, 7) for simultaneous supply of two by 90 ° and / or three by 120 ° phase-shifted periodic electrical signals in the electrically conductive structures ( 2, 3) are formed.

5. Apparatus according to claim 3 or 4, characterized in that the means (6, 7) for feeding an electrical signal in a pad of the substrate (1) are formed, in particular a periodic electrical signal having a frequency different from frequencies of the plurality of phase shifted periodic electrical signals.

6. Device according to one of the preceding claims, characterized in that the measuring sensor (4) for the simultaneous measurement of fields generated by a maximum of two electrical signals is formed by means of field coupling.

7. Method for measuring a substrate (1) with electrically conductive structures (2, 3), in which a measuring sensor (4) is moved in a controlled manner relative to the substrate (1), in which a plurality of different electrical signals are fed into the electrically conductive structures (2 , 3) are fed simultaneously, in which the measuring sensor (4) measures fields generated by the electrical signals by means of field coupling and in which the measured fields are evaluated and properties of the electrically conductive structures (2, 3) determined on the basis of the evaluation of the measured fields become.

8. The method according to claim 7, characterized in that a plurality of mutually phase-shifted periodic electrical signals in the electrically conductive structures (2, 3) are fed simultaneously.

9. The method according to claim 7 or 8, characterized in that two by 90 ° and / or three by 120 ° phase-shifted periodic electrical signals in the electrically conductive structures (2, 3) are fed simultaneously.

10. The method according to any one of claims 7 to 9, characterized in that an electrical signal in a pad of the substrate (1) is fed, in particular a periodic electrical signal having a frequency which is different from frequencies of the plurality of mutually phase-shifted periodic electrical Signals is.