Method for open-loop or closed-loop control of the temperature of a chuck for a wafer, temperature adjustment device, and wafer testing system

A method for open-loop or closed-loop control of the temperature of a chuck for a wafer includes detecting the position of a test device for testing a wafer and determining the spatial distances between the test device and a plurality of temperature measurement devices for measuring the temperature of the chuck or of a wafer supported or clamped by the chuck. The method proceeds by selecting at least one temperature measurement device from the plurality of temperature measurement devices as a reference temperature measurement device; and controlling the temperature of the chuck by open-loop or closed-loop control on the basis of the temperature(s) of the chuck or wafer as measured by the selected one or more reference temperature measurement devices.

BACKGROUND

Related Art Chucks are used e.g. in the semiconductor industry, in particular in microelectronics and microsystem technology, for providing wafers, for example for examining geometric parameters of a wafer. Also, structures located on the wafer (electrical components such as diodes, transistors, integrated circuits, etc.) can be contacted with the aid of a test means (prober) and various functional tests can be carried out. Functional tests include e.g. applying a voltage and/or a current to the structures and measuring specific parameters. For such functional tests it is particularly advantageous for the wafer or the structures of the wafer to be tested to have a certain temperature at the beginning of the test. This has the particular advantage that influences interfering with the test can be reduced or substantially avoided. In addition, there is usually a change in the temperature of the structures or of the wafer due to the interaction with the test means (prober), in particular upon contacting the structures with the prober and due to the current flows during the performance of the functional tests. It is therefore advantageous to continuously temperature-control the structures or the wafer or to control or regulate the temperature thereof, so that preferably substantially identical test conditions prevail for the functional tests. The temperature range in which functional tests are carried out is usually in the range from about −75° C. to about 400° C.

A plurality of temperature sensors and temperature control elements can be used for controlling or regulating the temperature and can be controlled or regulated in different ways. A chuck often is equipped with a plurality of temperature sensors to obtain a measurement of the temperatures of different areas of the chuck or wafer. In addition, plural temperature control elements usually are provided for heating and/or cooling the chuck or wafer. Here, the temperature is monitored in a plurality of areas of the chuck or wafer and, in the case of a deviation from a target temperature, the temperature control element(s) in this area is/are controlled accordingly so that the temperature in these areas of the wafer or chuck is always substantially identical and substantially corresponds to the target temperature.

However, a regulation or control as described in the process is expensive to implement. In addition, areas of the chuck or wafer in which no functional tests are carried out are continuously temperature-controlled, but the temperature in these areas substantially has little or no influence on the functional tests.

It is therefore an object of the present invention to provide a method for temperature control or regulation as well as a temperature control device and a wafer test system for simplified, advantageous temperature control of a chuck or wafer.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a method for controlling or regulating the temperature of a chuck for a wafer, comprising the steps of: detecting the position of a test means for testing a wafer; determining the respective spatial distances between the test means and a plurality of temperature-measuring means for measuring a temperature of the chuck or a wafer mounted or clamped by the chuck; selecting at least one temperature-measuring means among the plurality of temperature-measuring means as a reference temperature-measuring means; and controlling or regulating the temperature of the chuck based on the temperature(s) of the chuck or wafer measured by the selected reference temperature-measuring means.

This method enables a simplified and advantageous temperature control of a chuck or wafer, since the temperature control of the entire chuck takes place substantially uniformly, for example by controlling all means for temperature control of the chuck. Thus, the method has low requirements in terms of process handling and/or the control or regulation electronics. In addition, there is no unnecessary heating and/or cooling of areas of the chuck or wafer that are insignificant for the functional tests carried out.

In some embodiments, a chuck has a platform for clamping a wafer, and a wafer may be mounted or clamped by the chuck e.g. by means of generating a magnetic field or a vacuum.

The chuck of some embodiments comprises a plurality of temperature-measuring means arranged in or on the chuck to measure a temperature of the chuck or wafer at preferably several different locations.

The wafer may be mounted or clamped by the chuck in such a way that a test means, for example a probe needle or a probe card, can contact different locations on a wafer surface and test structures located in the wafer or on a surface of the wafer. Plural probe needles or probe fingers may be aligned to contact contact surfaces of the structures to be tested and can examine the properties of the structure, e.g. by introducing a current or applying a voltage.

In some embodiments, the temperature of the chuck is controlled or regulated substantially uniformly, i.e. substantially in the same manner or consistently, such as by uniform control of one or more means for temperature control of the chuck, such as several electrothermal converters arranged in or on a chuck.

Selecting a temperature-measuring means as a reference temperature-measuring means may comprise selecting the temperature-measuring means that has the smallest spatial distance from the test means.

The temperature of the chuck, and furthermore of the wafer, may be controlled or regulated based on the measured temperature of an individual temperature-measuring means among the plurality of temperature-measuring means. Use may be made of the temperature-measuring means or the measured temperature of the temperature-measuring means that has the smallest spatial distance from the test means or is closest to the current position of the test means. Thus, advantageously, the temperature-measuring means that potentially detects or records a temperature change in the area of the wafer in which the structure to be tested is located most precisely and/or first in terms of time is selected for controlling or regulating the temperature of the chuck or the wafer as the reference temperature-measuring means.

If the determined spatial distances of two or more temperature-measuring means are within a certain tolerance T± and/or are substantially the same size, selecting the reference temperature-measuring means may comprise the step of: selecting the temperature-measuring means among the two or more temperature-measuring means that the has the greatest amount of temperature difference Tdiff and/or temperature change per time Tgrad; or selecting the two or more temperature-measuring means as reference temperature-measuring means. In accordance with this aspect of the disclosure, controlling or regulating the temperature of the chuck may be based on the mean or average of the temperatures measured by the reference temperature-measuring means. Here, the tolerance T± can correspond e.g. to an equivalent of preferably less than about 10 cm, more preferably less than about 1 cm, more preferably less than about 0.1 cm. Substantially the same size may correspond e.g. to a difference in the distances of less than about 10%, more preferably less than about 1%, more preferably than about 0.1%. The values can be selected according to the structural conditions, in particular the number and/or arrangement of the plurality of temperature-measuring means, and/or the desired behavior of the temperature control or regulation. Alternatively, two or more of the temperature-measuring means can be selected as reference temperature-measuring means, and the temperatures measured by the two or more reference temperature-measuring means and, for example, an average of the measured temperatures, can be used to regulate or control the temperature of the chuck.

Here, the temperature difference Tdiff corresponds to the amount of the difference between the measured temperature T(t) and:a target temperature of the chuck or wafer Tsoll:
Tdiff=|T(t)−Tsoll|ora previously measured temperature T(t−x) of the same temperature-measuring means:
Tdiff=|T(t)−T(t−x)|oran average temperature of a plurality of temperature-measuring means Tavg:
Tdiff=|T(t)−Tavg|=|T(t)−(T1+T2+T3+ . . . +TX)/X|.
Preferably, the temperature change per time Tgrad is compared within a certain time period t1:
Tgrad=|(T(x)−T(x+t1))/t1|.

In this way, that temperature-measuring means that detects the greatest temperature drop or the greatest temperature increase within a time period t1can be selected as the reference temperature-measuring means. The time period t1is preferably less than about 5 seconds, more preferably less than about 1 second.

In some embodiments, the spatial distance between the test means and a temperature-measuring means is determined based on vector coordinates. Here, the positions of the test means and the temperature-measuring means are preferably projected into a coordinate system and the connection vectors and further their amounts (lengths) are calculated to determine the respective distances between the test means and the temperature-measuring means. To determine the distance, 2D and/or 3D coordinates of the test means and the temperature-measuring means can be used. The 2D coordinates of the test means and/or the temperature-measuring means preferably relate to a plane parallel to the wafer surface. The determination of the distances based on vector coordinates is described in more detail in the detailed description of the figures.

A further aspect of the invention relates to a temperature control device for temperature control of a chuck and/or of a wafer positioned or clamped by the chuck. The temperature control device has a first communication interface for communicating with a chuck, and the first communication interface is suitable for transmitting electrical signals. The temperature control device further has a control unit in connection with the first communication interface. The control unit may be operative for: receiving electrical signals from a plurality of temperature-measuring means for measuring the temperature of the chuck or wafer; selecting one of the temperature-measuring means as a reference temperature-measuring means; and controlling or regulating the temperature of the chuck based on the temperature(s) of the chuck or wafer measured by the selected reference temperature-measuring means.

The temperature control device may be configured for selecting the temperature-measuring means that has the smallest spatial distance from a test means for testing the wafer as the reference temperature-measuring means.

In some embodiments, the control unit of the temperature control device is suitable for selecting the temperature-measuring means that has the greatest amount of a temperature difference Tdiff and/or temperature change per time Tgrad as the reference temperature-measuring means, provided that the determined spatial distances of two or more temperature-measuring means are within a certain tolerance T± and/or are substantially the same size.

The temperature control device of some embodiments further comprises: a second communication interface for supplying and/or draining a temperature control medium into or out of the chuck for controlling the temperature of the chuck; and/or a third communication interface for communicating with at least one electrothermal converter for controlling the temperature of the chuck.

A further aspect relates to a wafer test system for testing a wafer. The wafer test system in accordance with this aspect of the disclosure comprises a chuck for providing or clamping and temperature control of a wafer. Temperature-measuring means are provided for measuring a temperature of the chuck and/or of a wafer mounted or clamped by the chuck. The wafer test system further has: at least one test means for testing the wafer; a position detection means for detecting the position of the test means in relation to the chuck or wafer; and a temperature control device described in the process.

In the following detailed description, individual embodiments for solving the object will be described by way of example with reference to the figures. Some of the individual embodiments described have features that are not absolutely necessary in order to carry out the claimed subject matter, but which provide desired properties in certain applications. Thus, embodiments that do not include all the features of the embodiments described below shall also be considered to be disclosed as falling under the technical teaching described. Furthermore, in order to avoid unnecessary repetition, certain features will only be mentioned in relation to individual embodiments described below. It should be noted that the individual embodiments shall therefore not only be viewed individually, but also viewed together. On the basis of this overview, the person skilled in the art will recognize that individual embodiments can also be modified by including individual or multiple features of other embodiments. It is pointed out that a systematic combination of the individual embodiments with one or more features described in relation to other embodiments can be desirable and practical and shall therefore be considered, and shall also be regarded as encompassed by the description.

DETAILED DESCRIPTION

FIG.1is a sectional view of a wafer test system20according to an exemplary embodiment. The illustrated wafer test system20comprises a chuck1or a holding or clamping device that mounts or clamps a wafer2. The wafer2preferably is mounted parallel to a substantially flat surface of the chuck1by means of an applied magnetic field. Alternatively, the chuck1can have a plurality of suction grooves (not shown) via which the wafer can be sucked by means of negative pressure and thus clamped or positioned by the chuck1. As a result of the suction, the wafer2is pressed against the chuck1or arranged on it so that a good heat transfer coefficient between the chuck1and the wafer2is ensured. The chuck1preferably comprises a ceramic body, for example comprising aluminum oxide or aluminum nitride, and more preferably an electrically conductive shielding layer on the surface of the chuck1oriented toward the wafer2. The wafer2is preferably in substantially surface contact with the shielding layer of the chuck2. The wafer2preferably further has a wafer surface3comprising one or more structures4to be tested. The structures4to be tested are e.g. integrated circuits or electrical components (diode, transistor, etc.). The wafer2can have a different number and/or arrangement of structures4to be tested, depending on the size of the wafer surface3and the structures4to be tested.

In this context, reference is made to particularly preferred embodiments of the chuck as described in patent specifications US 2008/302513 and DE 20 2005 014 918 U1, the contents of which are hereby incorporated into the present disclosure by reference.

The illustrated embodiment of the wafer test system10further comprises at least one test means22with which a structure4of the wafer2to be tested can be tested. A suitable test means22has one or more probe needles23each of which can contact a contact point of a structure4to be tested. The properties of the structures4can be examined or tested in this way, for example by introducing a current or applying a voltage and/or measuring voltages/currents by means of the probe needles23. The control of the test means22, in particular the alignment of the test means22in relation to the wafer2or to the structures4, takes place e.g. by a (preferably separate) control device. In the embodiment of the wafer test system20shown illustrated herein, the test means22is moved over the wafer2and aligned on the wafer surface3in accordance with the positions of the structures4to be tested. In addition, a position detection means28for detecting and/or checking the position of the test means22preferably is provided. The position detection means28of certain embodiments receives the position of the test means22e.g. from an actuating or positioning device for moving the test means22. Alternatively and/or in addition, the position detection means28can detect the position of the test means22by means of sensors (e.g. infrared sensors, resistive sensors and/or magnetic sensors). The position of the test means22is detected or determined with the aid of the position detection means28, preferably in relation to a reference element/point of the wafer2and/or the chuck1(e.g. wafer surface3, structure4of the wafer, temperature detection means6of the chuck).

As an alternative to the test means22described in the process, a test means22suitable for testing the wafer2can have a so-called probe card24. The probe card24may comprise a circuit board25with contact elements26that can be contacted with contact points of structures4to be tested. The probe card24has the particular advantage of enabling plural structures4to be tested substantially simultaneously or immediately one after the other without realigning the test means22.FIG.2shows a further embodiment of a wafer test system20with such a probe card24as a test means22for testing the structures4on the wafer2.

In the embodiment shown, the chuck1comprises a plurality of temperature-measuring means6suitable for measuring a temperature of the wafer2or the temperature of the chuck1in a range close to or substantially adjacent to the wafer2(for example temperature sensors: PT100, NTC, PTC, etc.). In the embodiment shown, plural (preferably 5) temperature-measuring means6are provided next to one another at substantially regular intervals and in a plane substantially parallel to the wafer surface3. The temperature-measuring means6are arranged in the chuck1near the surface of the chuck1on which the wafer2is clamped/mounted, so that the temperature of the wafer2advantageously can be transmitted to the chuck1. The chuck1according to the exemplary embodiment shown preferably has one or more electrothermal converters9(for example electrical heating elements and/or Peltier elements) to enable controlling the temperature of the chuck1and, subsequently, of the wafer2. Preferably, the chuck1has more than 5, more preferably more than 10 electrothermal converters9preferably arranged in the chuck1in a substantially evenly distributed manner, so that the temperature of the chuck1can be advantageously controlled, in particular cooled and/or heated.

As an alternative to the exemplary embodiment of a chuck1described in the process, other means or features for temperature control or regulation of the chuck1can also be mounted. A further embodiment of a chuck1has a line8that is suitable for having a temperature control medium18flow therethrough, in particular temperature-controlled air and/or temperature-controlled liquid. The medium line8of the chuck1of this embodiment is designed in such a way that a large part of the chuck1can be temperature controlled substantially uniformly by means of the temperature control medium18flowing through the medium line8. The medium line8of some embodiments has a substantially meander-shaped course in the interior of the chuck1at least in part.FIG.2shows a further exemplary embodiment of a wafer test system20with a chuck1, the temperature of which can be controlled or regulated by a temperature control medium18.

The embodiment of a wafer test system20shown inFIG.1further comprises a temperature control device10for controlling or regulating the temperature control of the chuck1or wafer2. The temperature control device10of this embodiment comprises means for communicating with the chuck1, for example in the form of one or more communication interfaces12via which the temperature control device12can be connected to the chuck1. The temperature control device12of this embodiment has at least one first communication interface12athat is particularly suitable for transmitting electrical signals, in particular electrical signals from one or more temperature-measuring means6to the temperature control device12. Further, the temperature control device12according to the exemplary embodiment has at least one further communication interface12cthat enables communication with the one or more electrothermal converters9of the chuck1, in particular control of the electrothermal converters9. Alternatively and/or in addition, a single communication interface12for communicating with the temperature measuring means6and the electrothermal converters9can be provided.

The exemplary temperature control device12shown further has a control unit14(e.g. (micro) controller, FPGA, etc.) that is connected to the one or more communication interfaces12and can communicate with the chuck1via these interfaces. In particular, the control unit14is suitable for receiving, processing and/or evaluating the signals from the temperature-measuring means/temperature sensors6of the chuck1. Moreover, the exemplary embodiment of the control unit14ofFIG.1is suitable for influencing or controlling/regulating the temperature of the chuck1or the wafer2. In particular, the control unit14is suitable for controlling the electrothermal converters9of the chuck1to increase, decrease and/or keep substantially constant the temperature of the chuck1. Further, the control unit14may be designed to obtain the position of the test means22from the position detection means28. Alternatively and/or in addition, the control unit14of some embodiments is suitable for controlling or regulating a supply and/or drain-off of a temperature control medium18for temperature control of the chuck1and/or the temperature of the temperature control medium18. A detailed description of this will be given with reference toFIG.2.

Moreover, the embodiment of the control unit14shown inFIG.1enables the temperature control device10to carry out a method for temperature control or regulation of a chuck1and/or of a wafer2mounted or clamped by a chuck1. The method includes determining the respective spatial distances between the test means22and a plurality of temperature-measuring means6for measuring a temperature of the chuck1or of a wafer2clamped by the chuck1.

The control unit14in the embodiment shown can determine the respective spatial distance between the test means22and the plurality of temperature-measuring means6of the chuck1.

An exemplary method suitable for this step comprises defining the positions of the test means22and of the temperature-measuring means6in a (preferably Cartesian) coordinate system. The position of the test means22may be approximated to a point or a substantially punctiform, infinitesimally small area, preferably in a plane substantially parallel to the wafer surface3. This point may substantially correspond to a geometric center of gravity of the test means22or its projection onto the plane defined by the temperature-measuring means6of the chuck1. Further, a reference point of this embodiment is determined as the coordinate origin or pole/zero point of a two-dimensional coordinate system, which is preferably located on the plane of the plurality of temperature-measuring means6. Further, the positions of the individual temperature-measuring means6, as well as the test means22, are approximated to a substantially punctiform, infinitesimally small area (preferably corresponding to the geometric center of gravity) and assigned to a coordinate in the coordinate system. Moreover, the control unit14determines the distances of the individual temperature-measuring means6from the test means22. This distance calculation may be carried out by calculating the length (amount) of the connection vectors between the respective coordinates of the test means22and the temperature-measuring means6.

The method described in the process for determining the spatial distances between the test means22and the individual temperature-measuring means6represents only one embodiment. For example, the positions of the test means22or of the temperature-measuring means6can also be assigned to coordinates in a three-dimensional coordinate system (without projection to a certain plane—seeFIG.2). In addition, any alternative methods for determining the distances of the test means22from the temperature-measuring means6can be used.

Furthermore, the exemplary method for temperature control or regulation of a chuck1or of a wafer2clamped by the chuck1comprises the step of:selecting a temperature-measuring means6from the plurality of temperature-measuring means6as a reference temperature-measuring means; andselecting the temperature-measuring means6having the smallest spatial distance from the test means22.

To this end, the control unit14of some embodiments compares the determined spatial distances Ai of the individual temperature-measuring means6from the test means22and selects the temperature-measuring means6with the smallest distance Ai as the reference temperature-measuring means. If two or more temperature-measuring means6have substantially the same distance or distances with a difference less than a certain tolerance value T± (preferably less than about 1 cm, more preferably less than about 0.1 cm), a (further) selection among the temperature-measuring means6concerned takes place by choosing the temperature-measuring means6among the two or more temperature-measuring means6(the determined spatial distances of which from the test means22are within a certain tolerance T± and/or are substantially the same) that has the greatest amount of temperature difference Tdiff and/or temperature change per time Tgrad.

Alternatively, two or more of the temperature-measuring means6can also be selected as reference temperature-measuring means and, for example, an average of the temperatures measured by the reference temperature-measuring means can be used as the reference temperature for controlling the temperature of the chuck1.

If two or more temperature-measuring means6are at a substantially identical distance from the test means22, the temperatures or temperature profiles measured by the temperature-measuring means6concerned or having a substantially identical distance from the test means are further compared. For example:

the individual temperature difference Tdiff of a temperature-measuring means6corresponds to the amount of the difference between a temperature measured by the temperature-measuring means6at the time t T(t) and:

a target temperature of the chuck or of the wafer Tsoll:
Tdiff=|T(t)−Tsoll|ora previously measured temperature T(t−x) of the same temperature-measuring means6:
Tdiff=|T(t)−T(t−x)|(a selection process based on this temperature difference is shown as an example inFIGS.3and4)oran average temperature of a plurality X of temperature-measuring means6(preferably all temperature-measuring means6of the chuck1) Tavg:
Tdiff=|T(t)−Tavg|=|T(t)−(T1+T2+T3+ . . . +TX)/X|.The temperature change per time Tgrad within a certain period of time t1may correspond to the amount of a change in the temperature measured by a temperature-measuring means6over a duration or a period of time t1:
Tgrad=|T(x)−T(x+t1)|.

As a result, the temperature-measuring means6that detects the greatest temperature loss or the greatest temperature increase within a time period t1subsequently is selected as the reference temperature-measuring means. The time period t1, over which the temperature profile is determined, is preferably less than about 5 seconds, more preferably less than about 1 second, more preferably less than about 0.1 seconds.

The parameters described in the process for (further) selecting one of the temperature-measuring means6from the temperature-measuring means6concerned can be used both alone and in any combination, possibly with different weighting, for the step of selecting the reference temperature-measuring means. The same applies to the determined distance of the temperature-measuring means concerned. In addition, further alternative parameters can also be used for selecting the reference temperature-measuring means.

Furthermore, the exemplary method for temperature control or regulation of a chuck1or of a wafer2clamped by a chuck1may further comprise the step of: controlling or regulating the temperature of the chuck1based on the temperature of the chuck1or the wafer2measured by the reference temperature-measuring means selected.

The temperature of the entire chuck1, i.e. preferably all means for temperature control of the chuck1(e.g. electrothermal converters, temperature control medium/medium line), is controlled substantially uniformly/identically, so that the temperature of the chuck1is controlled substantially uniformly. For controlling or regulating the temperature of the chuck1, preferably only the measured temperature of the selected reference temperature-measuring means is used. In some embodiments, the temperature measured by the reference temperature-measuring means is compared with a specified target temperature of the chuck1or of the wafer2and, for example, is substantially adapted to the target temperature of the chuck1or of the wafer2by correspondingly controlling the temperature control means (e.g. electrothermal converter9) (see alsoFIG.4). As a result, it is possible for different areas of the chuck1, which influence the temperature of the wafer2, to have different temperatures.

FIG.2is a sectional view of a wafer test system20according to a further embodiment (similar to the embodiment inFIG.1). The wafer test system20shown inFIG.2comprises a chuck1that clamps a wafer2by means of a magnetic field or application of a negative pressure. The chuck1, like the chuck1inFIG.1, has plural temperature-measuring means6(e.g. PT100, NTC, PTC) for measuring the temperature of the chuck1or of the wafer2. These temperature measuring means6are connected to a control unit14via a first communication interface12a. The wafer test system20, like the system inFIG.1, is suitable for carrying out the method described in the process for controlling the temperature of a chuck1or of a wafer2.

As an alternative to the wafer test system20shown inFIG.1, however, in the system shown inFIG.2, a so-called probe card24is provided as a test means22for testing the wafer2or the structures4on the wafer2. The probe card24of this embodiment comprises a circuit board25with contact elements26arranged in such a way that they can be brought into contact with contact points of several structures4to be tested on the wafer2. Thus, by aligning or positioning the test means22or the probe card24once, several structures can advantageously be tested substantially simultaneously and/or sequentially, which enables the test method to be accelerated.

What is also shown is a different determination of the respective spatial distances between the temperature-measuring means6and the test means22or the probe card24. Unlike inFIG.1, the position of the probe card24is not projected onto a plane formed by the positions of the temperature-measuring means6, but is determined according to an alternative method. This exemplary method assigns a coordinate in a three-dimensional (preferably Cartesian) coordinate system to the test means22(probe card24) and the temperature-measuring means6and determines the length or the amount of the connection vectors in three-dimensional space. As described with regard toFIG.1, the positions of the individual temperature-measuring means6and of the test means22are approximated to a substantially punctiform, infinitesimally small area (preferably corresponding to the respective geometric center of gravity). The distances Ai correspond to the length (amount) of the connection vectors between the coordinates of the temperature-measuring means6and the test means22.

Also different to the embodiment shown inFIG.1, the means for temperature control or controlling or regulating the temperature of the chuck1comprises a temperature control medium18and a medium line8, arranged in the chuck8, for conducting the temperature control medium18. For example, the temperature control medium comprises temperature-controlled air and/or temperature-controlled liquid and flows through the medium line8of the chuck in order to achieve temperature control (increasing/lowering/maintaining a temperature of the chuck1). The medium line8of the chuck1is designed to be substantially meander-shaped, at least in part, so that an advantageous temperature control of the chuck1can be achieved by means of the temperature control medium18. According to the preferred embodiment shown, the temperature control device10has a corresponding communication interface12bthat is suitable e.g. for supplying and/or draining the temperature control medium into the chuck1or out of the chuck1. A correspondingly configured control unit14is suitable for influencing or adapting the flow parameters, the temperature and/or the composition of the temperature control medium18as required. Various alcohols such as amyl alcohol (pentanol) and methanol, but also heptane, are particularly suitable as the temperature control medium. A thermal oil based on silicone oil is more suitable. A temperature control fluid containing perfluorinated polyether (e.g. available under the trade name Galden HT from Solvay Solexis SpA), poly(oxyperfluoro-n-alkylene) (e.g. available under the trade name Galden ZT from Solvay Solexis SpA) and/or a mixture of triethoxyalkylsilanes (for example available under the trade name DW-Therm from DWS Synthesetechnik) is preferably used. However, other substances known to the person skilled in the art can also be used. Further, the chuck1can have several (independent) medium lines8that are suitable for temperature control of a large part of the chuck1, which can furthermore preferably be controlled substantially uniformly, so that a substantially uniform temperature control of the entire chuck1or all temperature control elements of the chuck can be used.

FIG.3is a top view of a chuck1with a mounted or clamped wafer2that has a substantially circular wafer surface3. The wafer has a plurality (preferably between 1 and about 1000; more preferably between about 5 and about 200; more preferably between about 10 and about 100; for example 14, as shown inFIG.3) of structures4to be tested. The structures are arranged in a substantially uniform pattern in or on the wafer2(wafer surface3). In the exemplary embodiment shown, the chuck1has a plurality (preferably between about 3 and about 20; for example 5, as shown inFIG.3) of temperature-measuring means6a,6b,6c,6d,6e, preferably PT-100 temperature sensors that are preferably located below the wafer2. Alternatively and/or in addition, other temperature sensors such as HTCs and/or NTCs can be provided to measure the temperature of the chuck1or of the wafer2.

The temperature-measuring means6a-6epreferably are arranged according to a pattern, as shown, and more preferably distributed substantially uniformly over the wafer surface3.FIG.3also shows a test means22with a plurality (preferably 4) of probe needles23(not identified) that are suitable for contacting contact surfaces of the structures4to be tested in order to test them.

The test means22shown inFIG.3is located substantially above one of the plurality of the structures4to be tested, with its probe needles23respectively contacting a contact surface of the structure4. In this state, the test means22has a position (preferably approximated, substantially punctiform and substantially corresponding to the geometric center of gravity) whose distance from the (preferably approximated, substantially punctiform and substantially corresponding to the geometric center of gravity) positions of the temperature-measuring means6a,6band6cis substantially identical (or wherein the distances between the test means22and one of the temperature-measuring means A6a, A6bor A6ceach have a difference within a specified tolerance value T±). If such a case occurs when using the method described in the process for temperature control or regulation of the chuck1, the reference temperature-measuring means preferably is selected among the temperature-measuring means6a,6band6ctaking into account the temperature difference Tdiff and/or the temperature gradient Tgrad of the temperature-measuring means6a,6band6c.

FIG.4shows an exemplary temperature profile for the arrangement shown inFIG.3and described in the process. The profiles of the temperatures T6a, T6b, T6c, T6dand T6emeasured by the temperature-measuring means6a-6eare shown here. As described in the process, the reference temperature-measuring means on which the regulation or control of the temperature of the chuck1or of the wafer2is based is selected among the temperature-measuring means6a,6band6c. To this end, in the present example, the temperature differences Tdiff of the temperature T(t) of the temperature-measuring means6a-6cmeasured at the time t are compared with the temperatures of the respective temperature-measuring means6a-6cmeasured at the time tx (i.e. a period of duration x before the time t):
Tdiff6a=|T6a(t)−T6a(t−x)|
Tdiff6b=|T6b(t)−T6b(t−x)|
Tdiff6c=|T6c(t)−T6c(t−x)|

InFIG.3, the temperature difference Tdiff6aof the temperature-measuring means6ais shown as an example or representative, which in this exemplary scenario also corresponds to the greatest temperature difference of the temperature-measuring means6a-6c.

The temperature differences Tdiff6a, Tdiff6band Tdiff6care compared with one another and the temperature difference with the highest value is determined. According to the exemplary method, the temperature-measuring means6associated with the temperature difference with the highest value is selected as the reference temperature-measuring means. Consequently, in the present exemplary method, the temperature-measuring means6ais selected as the reference temperature-measuring means and is used to control the temperature of the chuck1or of the wafer2.

Further preferably, the temperature control (control or regulation of the temperature) is carried out by substantially adjusting the temperature measured by the temperature-measuring means6a. As can be seen inFIG.4, the temperature control influences each of the plurality of temperature-measuring means6and thus preferably substantially all or at least a large part of the areas of the chuck1. In the present example, the temperature-measuring means6b-6emeasure a value (clearly) below the target temperature of the wafer1or of the chuck1.

The method explained with regard toFIGS.3and4is only an exemplary embodiment of the method for temperature control of a chuck or of a wafer. In particular, the parameters used to select the reference temperature-measuring means can be varied depending on the requirements and/or desire. Here, for example, a temperature gradient of the temperature-measuring means can be selected or used as a determining parameter. The measured temperatures of two or more temperature-measuring means6can also be used as a reference value for the temperature control, for example by averaging the measured temperatures. The method of temperature control can also take place in an alternative manner, for example by substantially halving the difference between the temperature of the reference temperature-measuring means and the target temperature of the chuck1or of the wafer2.

FIG.5shows a further embodiment of a chuck1. A temperature control of the chuck1is made possible by different temperature control media18a,18bin a first temperature control circuit30and a second temperature control circuit32. The two temperature control circuits30,32each have a medium line8a,8bthat extends at least in certain areas and substantially in a meandering manner. This exemplary embodiment enables advantageous temperature control of the chuck1, since different temperature control media18can be used for temperature control in different temperature ranges. For example, a first temperature control medium18ais used for a first temperature range, for example for a range between about −75° C. and about 100° C., and a second temperature control medium18bis used for a second temperature range, for example between about 50° C. to about 400° C. Various alcohols such as amyl alcohol (pentanol) and methanol, but also heptane, are particularly suitable as the temperature control medium18. A thermal oil based on silicone oil is more suitably used. A temperature control fluid containing perfluorinated polyether (e.g. available under the trade name Galden HT from Solvay Solexis SpA), poly(oxyperfluoro-n-alkylene) (e.g. available under the trade name Galden ZT from Solvay Solexis SpA) and/or a mixture of triethoxyalkylsilanes (for example available under the trade name DW-Therm from DWS Synthesetechnik) is preferably used. However, other substances known to the person skilled in the art can also be used.

Furthermore, the chuck1ofFIG.5preferably has one or more electrothermal converters9to enable a further advantageous temperature control of the chuck1. The one or more electrothermal converters9are particularly suitable for temperature control that can be adjusted precisely and quickly in a comparatively low temperature range of about +−50° C.

In this context, reference is made to the preferred embodiment of a chuck particularly suitable for this purpose, described in U.S. Pat. No. 9,202,729, the content of which is hereby incorporated into the present disclosure by reference.

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