JP5997904B2 - Resistivity measuring apparatus and method - Google Patents

Description

This invention relates to a device applied to a semiconductor manufacturing or processing, measuring probe for measurement of electrical variables, regarding resistance measuring apparatus and method for testing the electrical properties.

  Semiconductor wafer resistivity measuring device is based on the resistivity of the wafer, the resistivity of the epitaxially grown film formed on the wafer surface, the sheet resistance of the diffusion layer or the implanted layer when impurities are diffused or implanted from the surface, and the metal produced on the surface. The sheet resistance of the film is measured. The result measured by the resistivity measuring apparatus is fed back to the process conditions of each semiconductor manufacturing apparatus and used as an important index for keeping the quality of the semiconductor device uniform.

  There are various types of surface materials for semiconductor wafers to be measured by a resistivity meter. When measuring the resistivity of these semiconductor wafers, the material of the tip of the four-probe probe, the tip radius of curvature, the tip, etc., depending on the material to be measured such as silicon and metal and the specific resistivity value In order for the load applied to the semiconductor wafer, the descending speed at the time of contact, and the like to match the object to be measured, the load and descending speed of the four-probe probe must be set appropriately.

JP 2010-225920 A

  However, with the thinning of the semiconductor wafer, the measured value fluctuates due to the contact state with the semiconductor wafer controlled by the load and descending speed of the four-probe probe, and it becomes difficult to obtain a reliable true value. It is coming. Further, it is assumed that the contact state with the semiconductor wafer at each measurement point changes due to the deflection of the wafer and the non-uniform film thickness as the diameter of the wafer increases.

The present invention has been made paying attention to the above circumstances, and its purpose is to automatically adjust the contact state between the probe and the semiconductor wafer at each measurement point according to the deflection of the wafer and the uneven film thickness. It can be to provide a resistance measuring device and method Ru can be measured reliable resistivity.

One aspect of the present invention in order to achieve the above object, an apparatus for measuring a plurality of measurement positions of the resistivity of the c Eha, and pushing means for pushing the front Kiu Eha move the probe in a vertical direction , before measuring means for measuring a plurality of measurement items that have been set in advance by supplying a current to the pre Kiu Eha by Kipu lobes score before Symbol measurement results of the change rate of the measurement items measured by the measuring means a number applying means for applying and a pushing amount determining means for determining the total or we push inclusive of the score of each pressing amount of the probe, and a control unit. Then, when the measurement result of the previous measurement position by the measurement unit exceeds an arbitrary reference value by the control unit, a preset contact condition range is set from the current push amount, and the push unit is set to the push unit. Measurement is performed on the measurement item, the measurement results of the plurality of measurement items are analyzed, the change of the measurement result is scored by the score giving means, and the score is comprehensively evaluated by the indentation amount determining means. The optimum push amount is determined, and the optimum push amount is set to the push amount when the next measurement is performed.

That is, when measuring the resistivity of the c Eha, a function of adjusting automatically during measuring the pushing amount of up Help lobe is driven and controlled by the probe vertical drive unit is brought into contact with the front Kiu Eha, during measurement automatic adjustment function of the pushing amount, in the case where advance arbitrarily set one variation width from the previous measurement value exceeds the reference, in any contact condition range, optimum by changing the pushing amount by a predetermined amount By specifying the indentation amount and measuring with the optimum indentation amount from the next measurement position , a reliable true value can be obtained by always maintaining the optimum contact state.

That is, according to the present invention, the contact state between the probe and the semiconductor wafer at each measurement point can be automatically adjusted by the deflection of the wafer and the non-uniform film thickness, and a reliable resistivity can be measured. resistance measuring device and method Ru can can provide.

The block diagram which shows the whole structure of the 4 probe resistivity measuring apparatus which concerns on one Embodiment of this invention. The external view which shows the detailed structure of a probe vertical drive part. The block diagram which shows the internal structure of 4 probe probes. The graph showing the experimental value which showed the relationship between the pushing amount of a probe, the rotation angle of a vertical drive cam, and the spring stress used as the load to a semiconductor wafer. The figure which shows the measuring system of step 1 by a dual configuration system. The figure which shows the measurement system of step 2 by a dual configuration system. The flowchart which shows the determination method of the pushing amount of 4 probe probes. The figure which shows the example of the determination table in the case of determining pushing amount from the measurement result of each measurement item.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an overall configuration of a 4-probe resistivity measuring apparatus according to an embodiment of the present invention.
In FIG. 1, this four-probe resistivity measuring apparatus includes a disk-shaped measurement stage 11 on which a semiconductor wafer 12 to be measured is placed, a rotation drive unit 13 that rotates the measurement stage 11, and the measurement stage 11. A four-probe probe 14 for measuring the resistivity of the semiconductor wafer 12 in contact with the upper surface of the semiconductor wafer 12 placed thereon, and a measurement current supplied to the semiconductor wafer 12 by the four-probe probe 14 for resistance A measurement unit 15 that measures a plurality of measurement items for obtaining a rate, a probe vertical drive unit 16 that moves the four-probe probe 14 in the vertical direction, and the probe vertical drive unit 16 and the four-probe probe 14. The probe horizontal drive unit 17 that moves in the radial direction of the measurement stage 11 and the position of the measurement point are specified, and this is the case when there are a plurality of four probe probes 14. An operation unit 18 for inputting control information for designating any one of a plurality of four probe probes, a display unit 19 for displaying data such as the position of a measurement point and the resistivity of a measurement result, and the rotation drive according to the control information A control unit 20 is provided for driving the unit 13, the probe horizontal drive unit 17, and the probe vertical drive unit 16 to bring the four probe probes 14 into contact with specified positions on the upper surface of the semiconductor wafer 12. The control unit 20 is supplied with predetermined operating power from the power supply unit 21.

  The control unit 20 includes automatic setting means for automatically setting the descending speed until the four-probe probe 14 driven by the probe vertical drive unit 16 contacts the semiconductor wafer 12 and the amount of pressing with respect to the semiconductor wafer 12. . Hereinafter, the configuration of the probe vertical drive unit 16 and the control operation of the control unit 20 for the probe vertical drive unit 16 will be described in detail.

FIG. 2 is an external view showing the configuration of the probe vertical drive unit 16, the four-probe probe 14, the semiconductor wafer 12, and the measurement stage 11 in FIG.
The probe vertical drive unit 16 includes a probe mounting bracket 16a, a cam receiver 16b, a weight 16c, a vertical drive cam 16d, and a stepping motor 16e.

  The probe mounting bracket 16a is a bracket to which the four-probe probe 14 is mounted. The cam receiver 16b receives a probe vertical driving force integrated with the probe mounting bracket 16a. The weight 16c is one weight having a mass sufficient to apply a static load in the vertical direction to the probe vertical drive unit 16. The vertical drive cam 16d is connected to the shaft of the stepping motor 16e, and is always kept in contact with the tip of the cam receiver 16b, so that the weight of the probe mounting bracket 16a including the weight of the weight 16c can be reduced. Support on the axis. The vertical drive cam 16d has, for example, an eccentric circular cam shape, and moves the cam receiver 16b up and down depending on the rotation angle. The stepping motor 16e is connected to a cam receiver 16b supported by the probe mounting bracket 16a and a vertical driving cam 16d on a support member independent of the probe mounting bracket 16a, and is arbitrarily selected according to control information commanded from the control unit 20 Rotate / stop at the position of the rotation angle.

  With the above configuration, the control unit 20 controls the probe vertical drive unit 16 by giving control information indicating the push amount for determining the load to be applied to the probe appropriate for the type of the semiconductor wafer 12 and the probe vertical movement speed. Appropriate contact between the needle probe 14 and the semiconductor wafer 12 is realized, and the resistivity of the semiconductor wafer 12 is measured by the measuring unit 15.

FIG. 3 shows the configuration of the 4-probe probe 14 and the semiconductor wafer 12 portion, and shows the internal configuration of the 4-probe probe 14.
In FIG. 3, a sufficient load is applied to the four-probe probe 14 so that the probe 14 a is always in contact with the surface of the semiconductor wafer 12. Since the four-probe probe 14 acts so that the vertical position control is performed by the probe vertical driving unit 16, the leaf spring 14b and the upper end contact portion of the probe 14a are bent according to the spring constant according to the vertical position. As a result, the pressing force between the probe 14a and the semiconductor wafer 12 is determined only by the spring stress of the leaf spring 14b, and is stopped at a predetermined pressing amount.

The probe 14a in contact with the semiconductor wafer 12 constitutes an electric circuit connected to the measuring unit 15 via the lead 14c, and can measure the resistivity of the semiconductor wafer 12.
FIG. 4 is a graph showing experimental values showing the relationship between the pressing amount of the probe 14a, the rotation angle of the vertical drive cam 16d, and the spring stress as a load on the semiconductor wafer 12.

  This experimental value is obtained from the change of the pushing amount (unit: mm) as the first X axis obtained from the change of the load as the Y axis and the deflection of the leaf spring 14b, and the rotational angle and the pushing amount (unit of the vertical drive cam 16d). mm) to obtain the second X axis in FIG.

The control unit 20 can control the stepping motor 16e based on the experimental value and adjust the pushing amount to accurately and freely control the needle pressure (load) at the tip of the probe.
As a measurement method using the four probe probes 14 arranged in series, there is a dual configuration method.

FIG. 5 shows step 1 of the dual configuration method.
First, as shown in FIG. 5A, a current I is passed between the probes 1-4 of the four-probe probe 14 by the constant current source 33, and the voltage Va between the probes 2-3 is measured by the voltmeter 34. To do. At this time, in order to remove an error due to rectification between the probe and the sample (semiconductor wafer 12), the polarity of the applied current I by the constant current source 33 is changed as shown in FIG. Ask for. Here, the voltage between the probes 2-3 when the current I flows between the probes 1 → 4 is assumed to be “Va +”. The voltage when the current I is passed between the probes 4 and 1 is assumed to be “Va−”. At this time, it can be determined that the smaller the voltage difference between “Va +” and “Va−”, the better the contact state between the probe and the semiconductor wafer 12.
The resistance value Ra in step 1 can be calculated by the following equation (1).
Ra = Va / I = ((| Va + | + | Va− |) / 2) / I (1)

FIG. 6 shows step 2 of the dual configuration method.
As shown in FIG. 6A, a current I is passed between the probes 1-3 of the four-probe probe 14 by the constant current source 33, and the voltage Vb between the probes 2-4 is measured by the voltmeter 34. At this time, in order to remove an error due to rectification between the probe and the sample (semiconductor wafer 12), the polarity of the applied current I by the constant current source 33 is measured as shown in FIG. Ask for. Here, the voltage between the probes 2-4 when the current I is passed between the probes 1 → 3 is assumed to be “Vb +”. The voltage when the current I is passed between the probe 3 and the probe 1 is assumed to be “Vb−”. At this time, the smaller the voltage difference between “Vb +” and “Vb−”, the better the contact state between the probe and the semiconductor wafer 12.

The resistance value Rb in step 2 can be calculated by the following equation (2).
Rb = Vb / I = ((| Vb + | + | Vb− |) / 2) / I (2)
The probe interval correction coefficient Ka can be calculated by the following equation (3).
Ka = 114.696 + 25.173 (Ra / Rb) −7.872 (Ra / Rb) ² (3)
And sheet resistance (rho) s can be calculated by following Formula (4).
ρs = Ka × Ra (4)

  The probe intervals of the four probe probes 14 are adjusted to be equal to each other, but minute variations actually occur depending on the accuracy of the bearings. In the dual configuration method, the change in the probe interval is reflected in the measurement voltages Va and Vb, and is reflected in the calculated values Ra, Rb, Ka, and ρs, and even if there is a change in the probe interval, the change occurs. The error of the measured value can be corrected.

Next, a method for automatically adjusting the pushing amount during measurement of the four-probe probe 14 will be described with reference to the flowchart shown in FIG.
First, the control unit 20 determines the difference between the voltages “Va +” and “Va−” at the previous measurement point and the difference between the voltages “Vb +” and “Vb−” with arbitrary reference values. It is determined whether it is within the allowable range (step S1). If it is determined that the value is within the allowable range, the process ends.

  When the allowable range is exceeded in step S1, the control unit 20 sets the contact condition range (push amount) for readjustment to “current push amount” ± (0.05 mm to an arbitrarily set range). (Step S2). In the present embodiment, as an example, the current push amount is 0.5 mm, and the contact condition is 0.05 mm to 0.15 mm.

The control unit 20 starts the pressing amount from “current pressing amount” +0.05 mm, and measures the − direction when the + direction ends (step S3).
The control unit 20 shifts the measurement point by 0.1 mm in the center direction of the R axis (step S4).
In this state, the control unit 20 starts measurement by the measurement unit 15 (step S5) and acquires the measurement result (step S6).

  Steps S4 to S6 are repeated, and the pressing amount is measured from +0.05 mm to an arbitrarily set range. Measure in the range of -0.05mm to an arbitrarily set in the direction of pushing up. At this time, if the measurement result clearly deteriorates, the measurement with the pushing amount changed is terminated even before the arbitrarily set range.

  The control unit 20 analyzes the measurement result of each measurement item, and the difference between the voltages “Va +” and “Va−” and the difference between the voltages “Vb +” and “Vb−” are compared with the previous measurement result. The smaller the rate of change, the better the result is judged as “good”. Further, since “Va” + “Vb”, the voltage difference is similarly determined. (Step S7)

In step S7, the quality of each value is determined according to the following criteria.
Va difference: The rate of change between the voltage difference at the time of polarity reversal measured in Step 1 of FIG. 5 and the value at the previous measurement is small.
Vb difference: The rate of change between the voltage difference at the time of polarity reversal measured in Step 1 of FIG. 6 and the value at the previous measurement is small.
Va + Vb: The rate of change between the sum of the voltages measured in step 1 of FIG. 5 and step 2 of FIG. 6 and the value measured last time is small.
Next, each change rate is comprehensively evaluated by assigning a score from the best data, and the optimum push-in amount is determined.

FIG. 8A shows the measurement results of the rate of change in Va difference and Vb difference between the previous measurement result and the current measurement result. The control unit 20 determines that the rate of change of Va difference (182.4%) exceeds an arbitrary reference value (for example, 150%), changes the push amount, and performs remeasurement.
FIG. 8B shows a measurement result when the pressing amount is measured by changing the current pressing amount by 0.05 mm from “current pressing amount” +0.05 mm to +0.15 mm.

FIG. 8C shows the measurement results when the indentation amount is measured by changing the “current indentation amount” from −0.05 mm to −0.15 mm.
FIG. 8 (d) shows a determination table for each measurement result, and the optimum push-in amount is "current push-in amount" -0.15 mm that minimizes the sum total obtained by adding points to each change rate. Can be determined.

The control unit 20 sets the optimum push amount determined in step S7 as the push amount for the next measurement. In addition, the measurement result at this time is the current measurement result.
And the control part 20 repeats the process of step S1-S7 about the remaining measurement points with the newly set pushing amount, and measures.

From the above, in this embodiment, “current push amount (0.5 mm)” − 0.15 mm is reset as the optimum push amount, and the subsequent measurement is performed with the newly reset push amount.
According to the above embodiment, in the semiconductor wafer resistivity measuring apparatus that measures the resistivity of a semiconductor wafer using a four-probe resistivity meter, the control unit 20 controls the probe vertical drive unit 16 during the measurement with respect to the semiconductor The pushing amount of the four-probe probe 14 is controlled so as to maintain an optimum contact state between the semiconductor wafer 12 and the probe in accordance with changes in the wafer deflection and film thickness. Therefore, the contact state of the four-probe probe 14 can be automatically optimized during the resistivity measurement, and the resistivity can be measured with reliability.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Measurement stage, 12 ... Semiconductor wafer, 13 ... Rotation drive part, 14 ... 4 probe probe, 14a ... Probe, 14b ... Leaf spring, 14c ... Lead, 15 ... Measurement part, 16 ... Probe vertical drive part, 16a ... probe mounting bracket, 16b ... cam receiver, 16c ... weight, 16d ... vertical drive cam, 16e ... stepping motor, 17 ... probe horizontal drive part, 18 ... operating part, 19 ... display part, 20 ... control part, 21 ... power supply Part 33 ... constant current source 34 ... voltmeter.

Claims (4)

The resistivity of the c Eha an apparatus for measuring at a plurality of measurement positions,
And pushing means for pushing the front Kiu Eha move the probe in a vertical direction,
Measuring means for measuring a plurality of measurement items that have been set in advance by supplying a current to the pre Kiu Eha by prior Kipu lobe,
A number applying means for scoring the results of measurement of the rate of change of said measured measurement items by the pre-Symbol measuring means,
A pushing amount determining means for determining the total or we push inclusive of the score of each pressing amount of the probe,
When the measurement result of the previous measurement position by the measurement unit exceeds an arbitrary reference value, a preset contact condition range is set from the current push amount, and the push item is measured for the measurement item. Analyzing the measurement results of the plurality of measurement items, assigning a score to the change in the measurement result by the score giving means, and comprehensively evaluating the score by the push amount determining means to determine an optimum push amount And a control unit for setting the optimum push amount to the push amount when measuring next.
Resistance measuring device characterized by comprising a.   The resistivity measuring apparatus according to claim 1, wherein the control unit determines the optimum indentation amount for the remaining measurement positions other than the previous measurement position.   The resistivity measurement apparatus according to claim 2, wherein the control unit resets the optimum pressing amount and measures the resistivity of the wafer with the reset pressing amount.   A resistivity measurement method executed by an apparatus that measures the resistivity of a wafer at a plurality of measurement positions,
  When the measurement result at the previous measurement position exceeds an arbitrary reference value, a preset contact condition range is set from the current push amount, and the push amount is changed by a predetermined amount within the contact condition range. The probe is brought into contact with the wafer, and a plurality of measurement items are measured within the contact condition range, the measurement results of the plurality of measurement items are analyzed, the change in the measurement result is scored, and the score is comprehensively calculated. And determining the optimum push amount, and setting the optimum push amount to the push amount when measuring next,
  Determining the optimum push-in amount for the remaining measurement positions other than the previous measurement position;
  A measurement step of resetting the indentation amount and measuring with the reset indentation amount;
Resistivity measuring method having

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