EP3847466A1

EP3847466A1 - Method for positioning test substrate, probes and inspection unit relative to one another, and tester for carrying out the method

Info

Publication number: EP3847466A1
Application number: EP19780142.6A
Authority: EP
Inventors: Anthony James LORD; Peter Douglas Andrews; Frank Thiele; Jens KLATTENHOFF; Gavin Fisher; Ralf Keller; Peter Schneider; Enrico Herz; Hans-Jürgen FLEISCHER; Jörg KIESEWETTER
Original assignee: FormFactor GmbH
Current assignee: FormFactor GmbH
Priority date: 2018-09-07
Filing date: 2019-09-04
Publication date: 2021-07-14
Also published as: CN112585485A; KR20210055708A; DE102018121911A1; WO2020048567A1; CN112585485B; TW202027227A

Abstract

The invention relates to a method and a tester (1) for positioning the test substrate (5), probes (6) and inspection unit (9) relative to one another, in which the test substrate (5) and the probes (6) are oriented into a desired position relative to one another at least in the X-Y plane, and the inspection unit (9) is moved in a Z position over the relative position in which the focus of the inspection unit (9) is set onto an observation point on the test substrate (5). In order to make tracking of the inspection unit (9) simpler and faster, the test substrate (5) and the inspection unit (9) are moved synchronously from this starting position in the Z direction such that the focal plane is maintained.

Description

Method for positioning the test substrate, probes and inspection unit relative to one another and probe to the same

execution

The invention relates generally to a method for

Positioning of test substrate, probes and

Inspection unit relative to one another, in which the test substrate and the probes are aligned with one another in a desired relative position at least in the XY plane and the inspection unit is moved into such a Z position via a relative position in which the focus of the inspection unit is set to an observation point of the test substrate is. The invention also relates to a prober for carrying out the method

It is known that a wide variety of electronic components, generally referred to as test substrates, are tested for different properties or are subjected to special tests. The test substrates can be used in various manufacturing and integration stages

available. So tests of semiconductor chips,

Hybrid components, micromechanical and micro-optical components and the like are carried out, which are still in the wafer composite or isolated or are already integrated in more or less complex circuits.

For testing and inspection of test substrates

Test stations, commonly referred to as probers,

used, which include a chuck with a surface for receiving test substrates. The chuck is a holding device that is matched to the holder of the test substrate, to its contacting and to the test conditions and is usually in X-, Y- and Z- by means of a movement unit. Movable direction.

The Prober also includes several probes that are held by a probe holder. Depending on the test substrate and test status, individual probes or probe cards with a large number of probe tips, so-called probe cards, can be used as probes. The probe holder includes

regularly a probe holder plate, which is arranged above the chuck and carries the individual probes, held by probe heads, or the probe card. Also the

The probe holder plate and / or the probe heads can have movement units by means of which the probes can be moved together or individually at least in the Z direction.

The Prober also has an inspection unit, which serves to depict the test substrate and the probe tips. The inspection unit comprises a microscope and / or a camera with which the surface of the test substrate can be viewed in the Z direction. The inspection unit often also has a movement unit in order to bring the objective for inspection in the Z direction to the test substrate, so that the focus of the inspection unit is on a specific one

Observation point of the test substrate is set, d. H. this observation point can be depicted sharply, and in order to establish a sufficient distance again, for example when the probes are to be replaced.

The movement units regularly leave each other

independent movements of the components of the prober mentioned, for example, with the inspection unit either the probe tips or the test substrate or Focus on intermediate positions. The

Movement units are also regularly equipped with drives for motorized movement of the chuck and / or the probe holder plate or the individual probes and / or the inspection unit. The motor movements of the components mentioned are configured using a

Control unit realized.

The focus of the observation point must be repeated several times in the course of a test sequence, which includes repeated contacting of one or more points on the test substrate and thus the necessary infeed movements in the X, Y and Z directions. Because of this, the time required increases with each new delivery movement.

To establish the electrical contact, in addition to the movability in the XY plane, which is always defined as the plane in which the receiving surface of the chuck lies and is usually realized by the movement unit of the chuck, an infeed movement in the Z direction between the probes and the test substrates required.

First, probes and the test substrate are used

at least one of the movement units is positioned relative to one another in the X-Y plane, so that they are at a distance from one another. The contact is established in a subsequent infeed movement in the Z direction (hereinafter referred to as Z infeed movement). This Z position is called the contact position. After completion of the test, the contact is released by moving in the Z direction and the next contact position in the X-Y plane is approached.

The Z infeed movement into the contact position can be done using a movement of the probes or by means of a movement of the test substrate. The delivery of the probes has the advantage that the relative positions of

Do not change the inspection unit and test substrate and thus the focus on the contact surface is maintained, so that even the smallest evasive movements of the observed ones

The probe tip in the X-Y direction, which takes place when the probe tip is attached and is desired for establishing a safe electrical contact, can be continuously observed.

In various situations, approaching an intermediate position of the probe tips in the Z direction above the test substrate has proven to be advantageous. In this

The intermediate position is a sufficiently large distance between the probe tips and the test substrate, so that, for. B. Corrections in the X-Y plane are possible without the risk of

Damage to probe tips. This intermediate position

but at the same time allows control of the X-Y positions and quick, also manual delivery to the contact position.

Infeed in the Z direction by the chuck is often preferred or only possible with it due to the design of the probe holder. However, this means that the

Inspection unit must be tracked in order, for. B. to recognize the contact surfaces of the test substrate. If the intermediate position also has to be approached, the time required for this, due to the necessary intermediate corrections on both components, the chuck and the inspection unit, adds up to a measure that corresponds to the constant requirement

Cost efficiency and a partially or fully automated Testing is no longer acceptable.

There is therefore a need for the delivery movements of the

Simplify and accelerate the inspection unit in the Z direction.

Their delivery accuracy in the X-Y plane should also be maintained.

Furthermore, the final delivery should also be

Contact position, at least from the intermediate position

outgoing, can also be done by manual operation.

The concept for solving the task envisages that effect using the chuck and inspection unit

simulate what would be achieved if the probe holder plate with the probes was raised and to establish and release the contact between the test substrate and probe tips

would be lowered and the test substrate and inspection unit would not be moved. This is realized by starting from a starting position in which the focus of the inspection unit is on an observation point of the

Test substrate, for example a contact surface on the surface of the test substrate, is set that

Test substrate and the inspection unit are moved synchronously in the Z direction in order to set the desired end position of the test substrate relative to the probe tips, for example the contact position.

This synchronous movement takes place in such a way that the focal plane is maintained at least during a Z feed movement, possibly also during the release of the contact, so that the observation point on the test substrate is sharp remains mapped, as is known from the movement of the probes from the prior art. Such a procedure can be regarded as a virtual movement of the probe holder plate and is also possible in those applications where the probe holder plate is immobile or its movement interferes disproportionately in the test sequence.

The term “a” movement in the Z direction encompasses both the entire movement sequence that is to be carried out by a required distance in the Z direction, for example the distance up to the contact of the probe tips on the

Test substrate to overcome, as well as individual sections of it. Such a section can, for example, the

Delivery from or to the above-mentioned intermediate position, both to the test substrate or away from it.

Features used to implement the concept are described below. This is the specialist in

combine different embodiments differently with each other, insofar as this seems sensible and suitable for an application.

The directions X, Y and Z correspond to the usual use in the present field for

horizontal X and Y directions and the vertical Z direction.

A synchronous movement while maintaining the focus level includes both the length of movement in the Z direction and the temporal component.

The term "synchronous" here also refers to simultaneous movements and includes such delays caused by the control unit is conditional and / or can be implemented with the currently customary computing technology if the focus is also shifted by means of the common algorithms, too

automated, recognized and a corresponding

Compensating movement is triggered.

Studies have shown that with the current

Prober technology latency periods, d. H. Delay times

between the start of the triggering, actually occurring movement, for example the chuck, and this

following actual movement, for example the

Inspection unit of 300 ms are still sufficient to be able to recognize a shift in the focal plane in time.

"In good time" means, for example, that the evasive movement triggered by the placement of the probe tips on the test substrate is perceived at a time when the probe tip is still on the contact area and / or has not yet suffered any damage or another disadvantageous relative position has been reached. Preferred the latency should be less than 200 ms, preferably less than 100 ms, more preferably less than 50 ms, more preferably less than 40 ms, more preferably less than 30 ms, more preferably less than 20 ms, more preferably less than 10 ms, more preferably less than 5 ms increasing scaling of the

electronic components and the performance of computing technology can further reduce permissible evasive movements and the realizable latency times.

A synchronous movement of the test substrate and

Inspection unit can be implemented, for example, by means of synchronous control signals for executing the movements of the chuck and inspection unit, with reference also to the time intervals of the control signals the above latencies are applicable.

If a movement of the chuck is described below, this is with the movement of the test substrate

identical since the chuck is on its horizontal

Receiving surface the test substrate carries.

According to one embodiment of the method, the movements of the test substrate and inspection unit in the Z direction can be initiated by a manipulator body, which is part of a manipulator of the prober used. The manipulator body is moved in such a way that the movement is clearly determined by a

Direction of movement and a measure of the movement, for example a length or an angle, is determined. The movement of the manipulator body is measured in terms of direction and dimension by means of a suitable movement sensor, so that from this sense of direction, from the direction of movement of the manipulator body, and length of the movement, from the

Dimension of movement of the manipulator body for which the movement of the chuck and / or inspection unit to be carried out in the Z direction can be determined.

Based on the measured values and the ones generated from them

Control signals are the movements of Chuck or

The inspection unit and the other prober component follow this initial movement synchronously on the basis of a mathematical coupling of the two movement units by means of the control unit. Depending on the configuration of the test device, other methods of connecting the two movements can also be considered, provided that these permit the synchronous movement. The initial movement can, for example be carried out by the chuck, whereupon the inspection unit follows. The other order or the movement of both components on the basis of the control signals generated from the measured values are also possible.

To implement the synchronous movement of the test substrate and inspection unit, the manipulator can be coupled to both movement units, so that the manipulator drives both when the motor is moving

Controls movement units by based on the

Measured values of the manipulator's motion sensor

Control signals are generated which are used to control the

Serve movement units.

Alternatively, the manipulator can be directly related to only one of the two movement units. In this embodiment, the second movement unit carries out a compensating movement in the Z direction.

According to a further embodiment, the

Manipulator body moved manually. Alternatively, movements of the manipulator body carried out by means of a suitable manipulator control are also possible.

A movement of the manipulator body can be a rotation of the manipulator body about an axis of rotation. The direction of rotation, clockwise or counterclockwise, gives the direction of direction in the Z direction, up or down, and the angle of rotation gives the value of the positive or negative stroke, i. H. the length of the movement in the Z direction.

According to a further embodiment of the method, the manipulator body can be moved by a Stop or more of them can be limited. The stop limits the amount of movement and can by the

Contact position must be defined. Even for frequent ones

Uses advantageous start, intermediate and

End positions, such as a minimum distance position, can be defined using a stop.

It was found that the axes of movement of the chuck and the inspection unit in the Z direction are not always exactly parallel to one another. According to an embodiment of the method, one of them is used for compensation

resulting change in the X-Y relative positions between the observation point of the test substrate and the focus of the

Inspection unit determines the deviation as a result of a Z movement and compensates for it using its movement unit. For this, too, are the above for synchronous movement

described latencies applicable.

The compensation of the X-Y deviation, here as

Designated linear compensation, depending on the direction of movement and the degree of deviation during or after the execution of the movement in the Z direction, can be carried out by an additional movement of at least one of the two components in the X-Y direction. For example, when the test substrate is moved in the X-Y direction, the compensation during the movement and before the probe tips are placed on the test substrate is preferred in order to avoid damage to the contact surface as a result of the subsequent compensation.

Alternatively, the compensation can take place after the Z movement. If the inspection unit is moved for this purpose, the relative position between the test substrate and Probe holder unaffected.

The determination of the deviations is based on the distance still existing between the two contact partners during the Z movement, which leads to a displacement of the image field relative to the test substrate in the case of Z movements which do not run parallel. Such a deviation is in the

Top view recognizable. This shift, like deviations in the synchronous Z movement, can be achieved by means of

known methods, e.g. B. pattern recognition methods or monitoring of the spatial positions of both components or other suitable measures can be determined in situ.

Alternatively, the position of the Z axes can be known

for example from previous delivery movements or an analysis of the prober. In all cases, the

Linear compensation can be compensated for by countermoving movements during or after the Z movement

In addition to the generic components chuck, probes with their corresponding holder and inspection unit, a prober which can be used to carry out the method has a positioning device which comprises movement units, at least one for the chuck and one for the

Inspection unit, for executing movements of the chuck and inspection unit at least in the Z direction. Next is at least one control unit for controlling both

Movement units configured such that movements of the chuck and the inspection unit can be carried out synchronously as described above. Alternatively, each of the movement units can have its own control unit which is used to carry out the synchronous movement

are communicatively connected. The synchronous movement takes place in such a way that the focal plane is maintained, so that the observation point remains in focus on the test substrate.

According to one embodiment, the

Positioning device of the Prober a manipulator, which serves to move the chuck or the inspection unit.

The manipulator comprises a manipulator body, one

Control element for moving the manipulator body and a motion sensor. Objects that can be moved in such a way that one can measure clearly from your movement are considered as manipulator bodies

Direction of movement and a measure of the movement can be removed.

According to an embodiment of the manipulator, a clear direction of movement is guaranteed if the manipulator has exactly one degree of freedom in its movement.

According to a further embodiment of the manipulator, the manipulator body can be a rotating body which is arranged rotatable about its axis of rotation.

The manipulator is operated by means of a suitable control element, which is based on the type of

Operation, manual or mechanical, and the type of

Movement, for example rotation or displacement, of the manipulator body is coordinated.

Direction of movement and measure of movement are determined by means of a manipulator motion sensor which is configured accordingly. Depending on the type of the movement value transmitter and the one to be determined with it

Movement is the movement value generator relative to

Manipulator body arranged. In the example of the

Body of rotation is the motion encoder

Rotary value encoder, which detects the direction of rotation and angle of rotation and is arranged, for example, axially to the rotating body.

Alternatively, more than one motion sensor can be used to determine the required measurement values. The measured values are, if necessary preprocessed, transmitted to the at least one control unit.

Control signals are generated on the basis of the measured values, which control the movement of Chuck or

Serve inspection unit or both in the Z direction as described above. For this purpose the

Movement value transmitter communicatively connected to the control unit.

According to a further embodiment of the prober, the manipulator has at least one stop for limiting the movement of the manipulator body. It is advantageous if this stop is variable and / or adjustable for a defined distance in the Z direction. By the stop is adjustable, different end or

Intermediate positions can also be approached manually. The at least one stop can be on the hardware side on the manipulator or on the software side, for example by means of the

Control unit, can be realized.

According to the description of the method, it may be necessary to linearly compensate the relative position of the chuck and the inspection unit in the XY direction in order to always have the desired image section available. To this includes one for linear compensation

configured prober at least one movement unit accessing the chuck or inspection unit, the

is configured to perform movements of the associated component in the X, Y direction in addition to the Z movement.

Optionally, both components can also be connected to such a movement unit. In addition, the control unit is also set up on the hardware and software side, the corresponding, at least one

Control the movement unit in the X, Y and Z directions.

The invention is based on

Embodiments are explained in more detail. The associated drawing shows in

1 shows a prober with the components essential to the invention;

FIGS. 2A and 2B show detailed views of an embodiment of a manipulator in perspective, as a view and in section, and

Fig. 3 shows a manipulator body with an adjustable stop.

The drawings show the device only schematically to the extent that it is used to explain the invention

is required. You make no claim to

Completeness or scale.

1 comprises a chuck 2 with a movement unit 3 of the chuck. The Chuck 2 can be moved in the X, Y and Z directions. The directions are through one

Coordinate system shown. On the upper, horizontal receiving surface 4 there is a test substrate 5, for example a Wafer. The wafer is contacted by means of probes 6, which are held by probe heads 7. The probe heads are arranged on a probe holder plate 8.

From above, in the Z direction, an inspection unit 9, for example a camera, looks at the test substrate 5, specifically at the contact point, so that it can be depicted sharply. The inspection unit 9 also has a

Movement unit 10 with which the inspection unit 9 can also be moved, for example, in the X, Y and Z directions, but at least in the Z direction.

To clarify the kinematic certainty of the moving components with the associated ones

Movement units or brackets, in the present case these are the chuck 2 and the inspection unit 9 with their

Movement units 3, 10 and the probe heads 7 with their probe holder plate 8 are fixed to the frame and thus statically determined to a common reference system

shown (hatched horizontal line).

For their operation, both movement units 3, 10 are communicatively connected, for example, but not by way of limitation, to a common control unit 11, which is configured for this in terms of hardware and software.

In the illustration, the probe 6 is in contact with the test substrate 5 by the chuck 2 in a

Contact position K _c was moved. Also the

Inspection unit 9 is in its contact position Ki. In this, the focus of the inspection unit 9 is set on the surface of the wafer 5 and thus also on the tips of the probes 6 lying thereon. If the contact is to be released, the Chuck 2 is moved downwards (represented by an arrow). At the same time, the inspection unit 9 is also moved downward with the same distance in the Z direction (represented by the same arrow length). The movements can be up to an intermediate position Zc, Zi (each represented by a dashed line for the receiving surface 4 of the chuck 2 and the lower edge of the inspection unit 9) or an end position Ec, Ei (each represented by a dash-dot line for the receiving surface 4 of the chuck 2 and the lower edge of the inspection unit 9) take place. Due to the synchronous movement of chuck 2 and inspection unit 9, the set observation point 12 remains on the

Test substrate 5, in the exemplary embodiment that is one of the contact surfaces of the wafer, which is or was contacted by a probe tip, is always clearly visible during the movement of the chuck 2 into one of the lower positions.

In the intermediate position Z _c or the end position E _c , the chuck 2 can be moved in the X and / or Y direction in order to approach another electronic component of the wafer and subsequently contact it by means of the probes 6.

For contacting the next electronic component, the wafer 5 is raised by means of a chuck 2, for example, into an intermediate position Z _c . This intermediate position Z _c can be in its Z coordinate with the previous and the

Intermediate position Z _{c of} each further electronic component of the wafer 5 match. Below is the

Movement of the chuck 2 into the contact position Kc.

In the control unit 11 are synchronized with the

Control signals for moving the chuck 2 control signals for Movement of the inspection unit 10 first in the intermediate position Zi and analog for the inspection unit

subsequent contact position Ki generated.

2A and 2B are exemplary and not

restricting an embodiment of a manipulator 13, which can be used to move the chuck 2. The same reference numerals used in both figures denote the same component of the manipulator.

The manipulator 13 itself is operated manually and controls a motor movement of the chuck 2.

The manipulator 13 comprises a manipulator body 20 which is designed as a cylindrical rotating body. The manipulator body 20 is rotatable in a housing 21

stored.

On the manipulator body 20 is a suitable connector 22 (Fig. 2B), an operating element 23, which in

Embodiment is designed as a lever 23, mounted so that the manipulator body 20 manually

Can be turned clockwise and counterclockwise.

Such a lever 23 is also for other movements

alternative versions of a manipulator body can be used. The lever 23 is guided in a frame 25 in that its contour corresponds to that contour of the frame 25.

Next are the operating force and the operating torque of the

Manipulator body 20 and thus its sensitivity can be varied by means of brakes 24. In the exemplary embodiment, two brakes 24 are arranged, which apply an adjustable force to the lateral surface of the cylindrical manipulator body 20 to press .

Is adjacent and axially to the manipulator body 20

Motion encoder 26, in the embodiment

Rotary encoder 26, which measures the direction of rotation and the angle of rotation. The measured values are optionally transmitted to the control unit 11 (FIG. 1) via a signal conductor 28 after preprocessing.

The manipulator body 20 and the rotary encoder 26 are protected from external influences by means of a cladding 27 and can be mounted on the prober (FIG. 1).

3 is an embodiment of an alternative

Manipulator body 30 shown, in which the

Manipulator body 30 is designed as a rotary knob 31 and can be locked in defined angular positions. The rotary knob 31 is rotatable about its axis 32. On a partial circumference, three radial recesses 34 are arranged in its lateral surface 33, into which a pin 35 can be inserted. The pin 35 is guided through a guide slot 37 of a guide plate 36 arranged concentrically to the rotary knob 31 into one of the recesses 34 and in this way limits the executable rotary movement of the rotary knob 31 to the length of the guide slot 37. If another recess 34 is used, another one is different Rotational movement executable, whereby the executable by means of the movement units 3, 10

Movement length is modified.

Alternative versions of a manipulator or the

Attacks are possible. If the Prober has several

Manipulators with different functions can support a haptic distinction via the design become .

execution

Reference list

1 rehearsal

2 Chuck

3 Direction of movement of the chuck

4 receiving surface

5 test substrate, wafer

6 probe

7 probe head

8 probe holder plate

9 inspection unit

10 Direction of movement of the inspection unit

11 control unit

12 observation point

13 manipulator

20 manipulator body

21 housing

22 connectors

23 Control element, lever

24 brakes

25 frames

2 6 Motion encoder, rotary encoder

27 paneling

2 8 signal conductors

30 manipulator body

31 rotary knob

32 axis

33 lateral surface 34 recess

35 pen

36 guide plate

37 guide slot

K _c contact position of the chuck

Z _c intermediate position of the chuck

E _c final position of the chuck

Ki contact position of the inspection unit Zi intermediate position of the inspection unit Ei end position of the inspection unit

Claims

1. Method for positioning test substrate (5),

Probes (6) and inspection unit (9) relative

to each other, in which the test substrate (5) and the probes (6) at least in the X-Y plane in one

desired relative position to each other and the inspection unit (9) is moved into such a Z position above the relative position in which the focus of the inspection unit (9) on an observation point (12) of the test substrate (5)

is set, characterized in that starting from this starting position, the test substrate (5) and the inspection unit (9) are moved synchronously in the Z direction such that the focal plane

is maintained.

2. The method according to claim 1, characterized

characterized that the movements of

Test substrate (5) and inspection unit (9) in the Z direction are initiated by a manipulator body (20, 30) which is moved manually, the direction of movement and the degree of movement of the

Manipulator body (20, 30) is measured and the direction of direction in the Z direction and the length of the movement in the Z direction are determined therefrom.

3. The method according to claim 1 or 2, characterized

characterized that the movements of Test substrate (5) and inspection unit (9) in the Z direction are initiated by a manipulator body (20, 30) which performs a rotation, the direction of rotation and the angle of rotation of the

Manipulator body (20, 30) is measured and the direction of direction in the Z direction and the length of the movement in the Z direction are determined.

4. The method according to any one of the preceding claims,

characterized in that the movement of the

Manipulator body (20, 30) is limited by at least one, optionally variable stop.

5. The method according to claim 6, characterized in that the at least one stop is set for a distance to be overcome.

6. The method according to any one of the preceding claims,

characterized in that during the Z movement of the test substrate (5) and inspection unit

(9) or thereafter linear compensation of deviations in the relative position between

Test substrate (5) and inspection unit (9) in the X-Y direction.

7. The method according to any one of the preceding claims,

characterized in that the maintenance of the focal plane and / or the relative position between the test substrate (5) and the inspection unit (9) are monitored in situ in the X-Y direction and a

detected deviation is compensated.

Prober for testing test substrates, which one Chuck (2) for receiving and holding a test substrate (5), probes (6) for contacting the test substrate (5), an inspection unit (9) for focused imaging of an observation point of the test substrate (5) during the test and one

Positioning device for moving the chuck (2) and the inspection unit (9), characterized in that the

Positioning device comprises movement units (3, 10) which are configured to execute movements of the chuck (2) and the inspection unit (9) at least in the Z direction and at least one control unit (11) which is used to control the movement units (3,

10) is configured to such movements of the chuck (2) and the inspection unit (9) in the Z direction

execute synchronously that the focus level is maintained.

9. Prober according to claim 8, characterized

characterized that the

Positioning device comprises a manipulator (13) with a manipulator body (20, 30), an operating element (23) for moving the manipulator body (20, 30) and a motion sensor that

Movement value transmitter (26) is configured and arranged relative to the manipulator body (20, 30) in such a way that it detects the type and extent of movement of the manipulator body (20, 30) by measurement technology, and that the

Manipulator (13) is communicatively connected to the control unit (11) for generating control signals for moving the chuck (2) and / or the inspection unit (9) in the Z direction on the basis of the measured values.

10. Prober according to claim 9, characterized

characterized in that the manipulator body (20, 30) has exactly one degree of freedom of movement.

11. Prober according to claim 9 or 10, characterized

characterized in that the manipulator body (20,

30) is a body of revolution and the motion sensor (26) is a rotary sensor.

12. Prober according to one of claims 9 to 11, characterized

characterized in that the manipulator (13) has at least one stop to limit the movement of the

Manipulator body (20, 30).

13. Prober according to one of claims 8 to 12, characterized in that the prober has at least one movement unit (3, 10) which is configured to move the chuck (2) and / or the

Execute inspection unit (9) in the X, Y direction, and that the control unit (11) is configured to determine deviations from a set X-Y relative position and / or a set Z relative position between an observation point (12) of the test substrate (5) and the focus of the

Inspection unit (9).