JP2019197771A - Prober device - Google Patents

Abstract

To calibrate the positional deviation generated in a chuck to which one end of a linear member is fixed.SOLUTION: A prober device 100 includes an XY stage 5 fixed to a main body housing 80, a Z stage 30 moved by the XY stage 5, a chuck 50 moved by the Z stage 30, and an image sensor 60 disposed above the chuck 50, and further includes a pipe 70 having one end fixed to the main body housing 80 and the other end fixed to the chuck 50, and a control device 90 that calculates an approximate expression (excluding the primary expression) obtained by approximating the least squares of the relationship between the target position of the XY stage 5 and the position of the chuck 50 measured by the image sensor 60.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a prober device.

  The prober apparatus is an apparatus that measures the electrical characteristics of a semiconductor wafer by moving the semiconductor wafer in the XYZθ directions while bringing the probe into contact therewith. Patent Document 2 discloses a positioning control device that uses an XYθ stage and an image sensor. The technique of Patent Document 2 captures a positioning target (part) placed on a table while still and images the first positioning for positioning, and second positioning for imaging and positioning while moving. Is to do. Further, the optimum value of the correction parameter is obtained by the least square method.

JP 2012-137916 A (paragraph 0092)

  By the way, the chuck that is disposed on the XYZθ stage and fixes the semiconductor wafer needs to blow nitrogen gas or DRY AIR toward the semiconductor wafer in order to prevent condensation of the semiconductor wafer. For this reason, one end of a hose (for example, a fluororesin pipe) is often fixed to the chuck. Also, a heater and a Peltier element cable for temperature control are attached to the chuck. For this reason, when a linear member such as a hose or a cable is attached to the chuck, the chuck is displaced due to the elastic force or elastic displacement of the linear member. Moreover, this positional deviation and elastic displacement vary depending on the amount of movement of the XYZθ stage.

  The technique described in Patent Literature 1 is based on a rigid XYθ stage. For this reason, with the technique described in Patent Document 1, it is not possible to calibrate the positional deviation that occurs when the linear member is attached to the table (chuck) attached on the XYθ stage.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a prober device capable of calibrating a positional shift generated in a chuck to which one end of a linear member is fixed. .

  In order to achieve the object, the present invention is moved by an XY stage (5) fixed to a main body casing (80), a Z stage (30) moved by the XY stage, and the Z stage. A prober device (100) comprising a chuck (50) and an image sensor (60) disposed above the chuck, wherein one end is fixed to the main body housing and the other end is fixed to the chuck. Approximate expression (excluding linear expression) that approximates the least squares of the relationship between the linear member (for example, pipe 70, cable 75) and the target position of the XY stage and the position of the chuck measured by the image sensor. And a control device (90) for calculating. In addition, the code | symbol and character in a parenthesis are the code | symbol attached | subjected in embodiment, etc., Comprising: This invention is not limited.

  According to the present invention, it is possible to calibrate a positional deviation that occurs in a chuck to which one end of a linear member is fixed.

It is a block diagram of the prober which is 1st Embodiment of this invention. It is a pattern figure of the mask for calibration. It is a flowchart for demonstrating a stage calibration method. It is a figure for demonstrating the calibration curve of the X-axis direction in 1st Embodiment of this invention. It is a flowchart for demonstrating the method of driving a stage using a calibration formula. It is a figure for demonstrating the calibration curve of the X-axis direction in 2nd Embodiment of this invention.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. In addition, each figure is only shown roughly to such an extent that this embodiment can fully be understood. Moreover, in each figure, the same code | symbol is attached | subjected about the common component and the same component, and those overlapping description is abbreviate | omitted.

FIG. 1 is a configuration diagram of a prober apparatus according to the first embodiment of the present invention.
The prober apparatus 100 includes an X stage 10, a Y stage 20, a θ stage 40, a Z stage 30, a stage controller 45, a columnar member 55, a chuck 50, a CCD camera 60 as an image sensor, and a hose 70. A cable 75, a chamber 85, a closing member 86, a main body housing 80, a control device 90, and a nitrogen cylinder 95.

  The X stage 10 has a Y stage 20 mounted on the top, and moves the Y stage 20 in the X-axis direction. The Y stage 20 mounts the θ stage 40 on the upper part and moves the θ stage 40 in the Y direction. The X stage 10 and the Y stage 20 constitute the XY stage 5. The θ stage 40 has the Z stage 30 mounted thereon and rotates the Z stage 30 around the Z axis. The Z stage 30 moves the chuck 50 in the Z direction via the columnar member 55.

  Each of the X stage 10, the Y stage 20, and the Z stage 30 incorporates linear scales 15, 25, and 35 that measure their control positions. The stage controller 45 includes the X stage 10, the Y stage 20, the θ stage 40, and the like so that the measurement positions of the linear scales 15, 25, and 35 coincide with the setting positions (target positions) set by the control device 90. The position of the Z stage 30 is feedback-controlled. With these configurations, the chuck 50 is moved in the X, Y, Z, and θ directions.

  The chuck 50 fixes the calibration mask 110 during stage calibration, and fixes the semiconductor wafer 120 during measurement of electrical characteristics or temperature characteristics. The columnar member 55 has a cylindrical shape and is formed longer than the moving distance of the Z stage 30. The columnar member 55 may be a prism. A circular opening 81 is formed in the bottom plate 85 a of the chamber 85. The diameter of the opening 81 is set to a size that does not contact the side surface of the columnar member 55 even when the columnar member 55 moves in the XY direction.

  The closing member 86 is a circular (annular) plate material, is placed on the upper surface of the bottom plate 85 a of the chamber 85, and closes the opening 81. However, the inner diameter of the closing member 86 is slightly larger than the diameter of the columnar member 55. Thereby, even if the columnar member 55 moves in the vertical direction, the closing member 86 abuts on the bottom plate 85a of the chamber 85 by its own weight. The chamber 85 forms a space filled with nitrogen and DRY AIR to prevent dew condensation on the semiconductor wafer. Since the chamber 85 is not a vacuum chamber, leakage of nitrogen and DRY AIR from the gap between the closing member 86 and the columnar member 55 does not matter.

  A hose 70 as a linear member is provided between the chuck 50 and the side plate 85 b of the chamber 85. The hose 70 is supplied with nitrogen or DRY AIR sprayed onto the semiconductor wafer 120. The hose 70 is a fluororesin pipe (Teflon (registered trademark) pipe), is hard, and has low flexibility. A cable 75 as a linear member is provided between the chuck 50 and the side plate 85 c of the chamber 85. The cable 75 energizes a heater and a Peltier element (not shown). The cable 75 also connects a probe that measures the electrical characteristics of the semiconductor wafer 120 and a measuring instrument (not shown).

  The chamber 85 and the X stage 10 are fixed to the main body housing 80. For this reason, the chuck 50 receives the restoring force of the hose 70 and the cable 75 due to the bending when the hose 70 and the cable 75 are attached. Further, the direction and magnitude of the restoring force received by the chuck 50 differ depending on the bent state of the hose 70 and the cable 75.

  Further, a θ stage 40, a Z stage 30 and a columnar member 55 are interposed between the chuck 50 and the XY stage 5. That is, the chuck 50 is disposed higher in the Z direction than the XY stage 5. For this reason, the chuck 50 tilts and is displaced in the X-axis direction or the Y-axis direction. Therefore, the position of the chuck 50 is different from the measurement positions of the linear scales 15 and 25 provided in the X stage 10 and the Y stage 20.

  In FIG. 1, the Y stage 20, the Z stage 30, the θ stage 40, and the chuck 50 are shown by broken lines in a state where they are slightly displaced in the X-axis direction. In FIG. 1, the amount of displacement of the chuck 50 is indicated by ΔX. Furthermore, the repulsive force of the hose 70 and the cable 75 changes due to the movement of any one of the X stage 10, the Y stage 20, the Z stage 30, and the θ stage 40, and the displacement amount (ΔX, ΔY, ΔZ) of the chuck 50 Also fluctuate.

  The CCD camera 60 is provided above the center of the XY stage 5 and below the upper plate 85d of the chamber 85. As a result, the CCD camera 60 is an image sensor that enlarges and images a part of the calibration mask 110 fixed to the chuck 50.

  The control device 90 is a PC (Personal Computer), and realizes functions of a position control unit and an image measurement unit (not shown) when a CPU (Central Processing Unit) executes a program. The position control unit controls a stage controller 45 that drives the X stage 10, the Y stage 20, the Z stage 30, and the θ stage 40. The image measurement unit measures the position of the chuck 50 (image measurement position) using the image captured by the CCD camera 60.

  Further, the control device 90 measures a minute displacement (for example, ΔX) generated in the chuck 50 while moving the X stage 10, the Y stage 20, the Z stage 30, and the θ stage 40, and calibrates the stage. Further, the control device 90 displays an image indicating the position of the chuck 50 (image measurement position) and a minute displacement on a display device (not shown) at the time of calibration. Note that the control device 90 and the nitrogen cylinder 95 are disposed outside the main body housing 80.

FIG. 2 is a pattern diagram of the calibration mask.
The calibration mask 110 is obtained by transferring a chromium oxide pattern onto quartz glass. The pattern of the calibration mask 110 is a pattern in which a plurality of parallel and equally spaced straight lines are arranged vertically and horizontally, and each straight line passes through the center point O (0, 0). The center point O of the calibration mask 110 is for evaluating the position of the chuck 50. Note that the grid interval D is narrower than the imaging range (dashed line) of the CCD camera 60. That is, the CCD camera 60 captures the entire range by performing multiple imaging.

FIG. 3 is a flowchart for explaining a stage calibration method.
This routine is activated when the calibration operator fixes the calibration mask 110 to the chuck 50 and activates the calibration program stored in the control device 90.

  The control device 90 performs image processing on the image captured by the CCD camera 60, and sets the center point O of the calibration mask 110 as an image measurement reference point (S11). After the process of S11, the control device 90 moves the X stage 10, the Y stage 20, and the Z stage 30 at a predetermined pitch (S12). At this time, the setting positions of the X stage 10, the Y stage 20, and the Z stage 30 are stored in the storage unit. After the processing of S12, the control device 90 measures the image of the intersection position (first time, the center point O) of the calibration mask 110 (S13), and stores the coordinates of the intersection in the storage unit.

  After the process of S13, the control device 90 tracks the intersection of the calibration mask 110 and determines whether the tracked intersection is within the imaging range (image measurement range) (S14). If the tracked intersection is within the imaging range (within S14), the control device 90 stores the coordinates of the intersection (S16). On the other hand, when the tracked intersection is out of the imaging range (out of range in S14), another intersection of the calibration mask 110 (for example, the intersection of coordinates (1, 0)) is within the imaging range (within the image measurement range). In. In this case, the control device 90 adds the coordinates of the other intersection at the grid interval D of the calibration mask (for example, shifts in the X direction) (S15), and stores the added coordinates of the other intersection (image measurement position). (S16).

After the process of S16, the control device 90 determines whether or not the set position of the XYZ stage is within the specification range (within the maximum movement range) (S17). If within the specification range (within the range in S17), the control device 90 returns the process to S12 and moves the X stage 10, the Y stage 20, and the Z stage 30 at a predetermined pitch (S12). On the other hand, if it falls outside the specification range (out of range in S17), the control device 90 approximates the image measurement position Xm with respect to the set position Xs of the XYZ stage by least squares (S18). That is, the control device 90 approximates the image measurement position (for example, the X axis) with the following nth order equation (however, excluding the first order equation) as a least square.
f (Xs) = a ₀ + a ₁ Xs + a ₂ Xs ² + a ₃ Xs ³ + (1)
Then, the coefficients a ₀ , a ₁ , a ₂ , a ₃ ,... Of the approximate expression f (Xs) are temporarily stored in the storage unit.

  In S11, the center point O of the calibration mask 110 is set as the image measurement reference point. For this reason, the positional deviation of the center point O generated when the hose 70 and the cable 75 are attached to the chuck 50 is regarded as zero.

FIG. 4 is a diagram for explaining a calibration curve in the X-axis direction in the first embodiment of the present invention.
The horizontal axis is the set position Xs of the X stage 10 stored in S12. The vertical axis represents the X coordinate (image measurement position) Xm of the intersection of the calibration mask 110 stored in S16. The broken line is an ideal straight line where the stage movement amount and the position of the calibration mask match (proportional). The solid line is an approximate expression obtained by approximating the measured value of the intersection point of the calibration mask 110 with a least square approximation by an nth order expression (for example, a quadratic expression). In FIG. 4, the difference (small displacement ΔX: deviation amount) between the solid line and the broken line varies depending on the set position of the X stage 10.

This approximate expression f (Xs) shows the relationship between the set position Xs of the X stage 10 and the image measurement position Xm at the intersection of the calibration mask 110. Since the approximate expression f (Xs) is a straight line having an inclination of 1 passing through the origin,
f (Xs) = Xs + a ₂ Xs ² + a ₃ Xs ³ + (2)
It becomes. Further, the approximate expression f (Xs) shown in FIG. 4 has a condition of monotonic increase (df (Xs) / dXs> 0). As a result, when the center point O of the calibration mask 110 is set as the target position (image measurement position Xm), the two set positions Xs of the X stage 10 are prevented from appearing.

Next, the control device 90 approximates the deviation amount ΔX at the set position Xs of the X stage 10 by least squares. That is, the control device 90 calculates the coefficients b ₀ , b ₁ , b ₂ , b ₃ ,... Of the calibration formula indicating the relationship between the set position Xs and the deviation amount ΔX = (f (Xs) −Xs). .
ΔX (Xs) = b ₀ + b ₁ Xs + b ₂ Xs ² + b ₃ Xs ³ +... (3)

  In the least-square approximation, all sections in which the stage is moved may be approximated by an nth-order equation (n: an integer equal to or greater than 2), or may be a moving average. 4 may be displayed on the display unit by the control device 90 at the time of calibration.

Returning to the description of the flowchart of FIG. 3, after the processing of S <b> 18, the control device 90 calculates a difference between each of the image measurement positions where the intersection of the calibration mask 110 is imaged and the value of the approximate expression (S <b> 19). It is determined whether (residual) is within a guaranteed range of prober position accuracy (S20). If within the accuracy guarantee range (within the range in S20), the control device 90 calculates the coefficients b ₀ , b ₁ , b ₂ , b ₃ ,... Of the calibration equation ΔX (Xs) obtained by the equation (3). A file is output (S21). At this time, the coefficients a ₀ , a ₁ , a ₂ , a ₃ ,... Of the approximate expression f (Xs) obtained by the expression (1) may be output as a file.

  On the other hand, if it is out of the guaranteed range (out of range in S20), the control device 90 changes the pitch interval (S22) to reduce the residual. After the process of S22, the control device 90 returns the set position of the stage to the initial state (S23), returns the process to S12, and moves the X stage 10, the Y stage 20, and the Z stage 30 at a predetermined pitch.

FIG. 5 is a flowchart for explaining a method of stage driving using a calibration formula. This routine (S30) is a case where the semiconductor wafer 120 is fixed to the chuck 50 (FIG. 1) and the electrical characteristics and temperature characteristics are measured, and is activated every time the stage is driven. At this time, the coefficients b ₀ , b ₁ , b ₂ , b ₃ ,... Of the calibration equation ΔX (Xs) output in the file in S21 (FIG. 4) are read in advance, and the target position of the stage Assume that (setting position) has been determined.

The control device 90 calculates the shift amount ΔX (Xs) at the image measurement position Xs (target value) using the coefficients b ₀ , b ₁ , b ₂ , b ₃ ,... Stored in the file. (S31). After S31, the stage set value Xs is calculated by subtracting the deviation amount ΔX (Xs) from the target value Xs (S32). After S32, the control device 90 outputs the stage set value Xs to the stage controller 45, and drives the X stage 10, the Y stage 20, and the Z stage 30 (S33).

  When there is an increase / decrease in the expression (1) (approximate expression f (Xs)), the maximum point is stored in the file in advance, and the setting position Xs of the X stage 10 increases from the maximum point. Determine whether to decrease.

  As described above, in the prober device 100, the hose 70 and the cable 75 as linear members are attached between the chuck 50 and the main body housing 80. For this reason, when the X stage 10, the Y stage 20, and the Z stage 30 are moved, the chuck 50 is displaced due to the restoring force of the hose 70 and the cable 75. The prober apparatus 100 captures an image of a cross line formed on the calibration mask 110 fixed to the chuck 50 while moving the X stage 10, the Y stage 20, and the Z stage 30.

  The control device 90 minimizes the position of the crosshair (image measurement position) obtained by image measurement with respect to the set position (target position) of the X stage 10, Y stage 20, and Z stage 30 by an nth-order equation (n: integer of 2 or more). Approximate square. The control device 90 changes the pitch interval until the difference between the image measurement position and the calibration formula approximated by the least square is within the accuracy guarantee range. The control device 90 stores the approximate expression f (Xs) and the calibration expression ΔX (Xs) within the accuracy guarantee range in a file.

  The prober apparatus 100 corrects by the read calibration formula, and controls the position of the X stage 10, the Y stage 20, and the Z stage 30 at the corrected set position (target position). As a result, it is possible to correct the elastic displacement (positional deviation) that occurs when the set positions of the X stage 10, Y stage 20, and Z stage 30 are changed.

(Second Embodiment)
In the first embodiment, the entire range of the stage movement amount is calibrated by an approximate expression using an nth-order expression (for example, a second-order expression), but it is simple in a special case where the deviation amount is point-symmetric. Can be calibrated.

FIG. 6 is a diagram for explaining a calibration curve in the X-axis direction in the second embodiment of the present invention.
As in FIG. 4, the horizontal axis in FIG. 6 is the stage movement amount, and the vertical axis is the mask position imaged by the CCD camera 60. The broken line is an ideal straight line where the stage movement amount and the position of the calibration mask 110 coincide (proportional). A solid line is a locus of intersection coordinates of the calibration mask 110. A difference between the solid line and the broken line is a minute displacement ΔX generated in the chuck 50.

  In FIG. 6, the minute displacement ΔX is point-symmetric about the point P. That is, the approximate expression f (Xs) that approximates the image measurement position Xm can be approximated by a cubic expression of the stage movement amount. Further, the minute displacement ΔX is in the opposite direction between when the stage movement amount X is decreased and when it is increased with reference to the point P. For this reason, if any one of the decrease time and the increase time is quadratic approximated with respect to the point P, the other can also be approximated.

  Similarly to the first embodiment, a condition for monotonically increasing (df (Xs) / dXs> 0) is attached to the approximate expression f (Xs).

(Modification)
The present invention is not limited to the above-described embodiment, and various modifications such as the following are possible, for example.
(1) The X stage 10, the Y stage 20, and the Z stage 30 of the above embodiment incorporate linear scales 15, 25, and 35, respectively, and are feedback controlled so that the measurement position and the target position coincide. A stepping motor may be used to perform open-loop control of the stage position.
(2) In the stage apparatus 100 of the above-described embodiment, the θ stage 40 and the columnar member 55 are interposed between the X stage 10 and the Y stage 20 and the Z stage 30, but the columnar member 55 is not necessary. I do not care. In the above-described embodiment, the calibration mask 110 is used. For example, a mark (mark) or a scale is attached to the chuck 50, and the CCD camera 60 images the mark or scale so that the position of the chuck 50 is imaged. You can measure.

5 XY stage 10 X stage 20 Y stage 30 Z stage 40 θ stage 50 Chuck 55 Columnar member 60 CCD camera (imaging device)
70 Hose (Linear member)
75 Cable (Linear member)
80 Body casing 81 Opening 85 Chamber 85a Bottom plate (bottom)
86 Closing member 90 Control device 95 Nitrogen cylinder 100 Prober device 110 Calibration mask 120 Semiconductor wafer

Claims (5)

An XY stage fixed to the main body housing;
A Z stage moved by the XY stage;
A chuck moved by the Z stage;
A prober device comprising an image sensor disposed above the chuck,
A linear member having one end fixed to the body housing and the other end fixed to the chuck;
A control device for calculating an approximate expression (excluding the linear expression) that approximates the least squares of the relationship between the first target position of the XY stage and the position of the chuck measured by the image sensor;
A prober device comprising: The prober device according to claim 1,
The prober device characterized in that the control device measures the position of the reference point of the calibration mask using the captured image of the calibration mask output from the imaging device to obtain the position of the chuck. The prober device according to claim 2,
The prober device, wherein the control device stores a relationship between the difference between the approximate expression and the first target position and the first target position in a file. The prober device according to claim 3,
A prober apparatus that controls the position of the XY stage and the Z stage at a second target position calibrated using the relationship stored in the file. A prober device according to any one of claims 1 to 4, wherein
A columnar member inserted between the chuck and the Z stage;
The prober apparatus characterized in that a length of the columnar member is longer than a moving distance of the Z stage.

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