JP2002040099A - Method for generating approximate waveform and semiconductor testing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for generating approximate a waveform capable of generating an approximate waveform with high approximate precision to a given analog waveform, and a semiconductor testing device capable of performing a precise quality judgment. SOLUTION: The value of the analog waveform is gained in a plurality of timings, the approximate values of the values of the analog waveform in the respective timings are calculated, and an approximate waveform is generated on the basis of the timings and the approximate value in each timing. Each of the timings is corrected, whereby the approximate waveform with high approximate precision is generated. Each of the timings is set to a timing where the square error of the value of the analog waveform and the approximate value in each timing is minimized, whereby an approximate waveform with a small error can be generated. In this semiconductor testing device, the above approximate waveform with high approximate precision is used as a test signal, whereby the quality judgment can be precisely performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an approximate waveform generation method for generating an analog analog waveform and a semiconductor test apparatus for testing a semiconductor device. In particular, the present invention relates to an approximate waveform generation method and a semiconductor test apparatus in which the approximate value calculation timing of an analog waveform is corrected.

[0002]

2. Description of the Related Art Conventionally, an approximate waveform generating method for generating an approximate waveform of an analog waveform calculates an approximate value of the analog waveform at timings arranged at predetermined time intervals, and generates an approximate waveform based on the approximate value. I was

FIG. 1 is a diagram showing an approximate waveform generated by a conventional approximate waveform generation method. The vertical axis of the graph in FIG. 1 represents voltage, and the horizontal axis represents time. The graph in FIG. 1 shows an analog waveform 50 and an approximate waveform 52 that approximates the analog waveform 50. The analog waveform 50 of this example is a waveform called a Lorentz waveform, and is given by the following equation.

(Equation 1) Here, t is time, τ is a peak position, and PW50 is a half width. In this example, τ = 55 [ns], PW50 = 20
[Ns]. The approximate waveform 52 holds an approximate value of the voltage value of the analog waveform 50 calculated at a timing of 10 [ns] from t = 0 [ns] until the next timing. The voltage value of the analog waveform 50 is divided into a plurality of predetermined ranges, and each range is approximated to a constant value.

FIG. 2 shows the relationship between the range of the voltage value of the analog waveform 50 and the approximate value. The column of the input voltage range indicates the voltage value of the analog waveform 50, and the column of the output voltage indicates the approximate value corresponding to the range of the voltage value of each analog waveform 50. In this example, the output voltage is the center value of the corresponding input voltage range.

FIG. 3 shows that t = 0 [ns] to 10 [ns].
The value of the analog waveform 50 at the timing of the interval, and
The value of the approximate waveform 52 is shown. One of the indexes indicating the degree of approximation of the waveform is a square error e _RMS ² . The square error is a value obtained by dividing the sum of square values of the difference between the value x _i of the ideal waveform and the approximate waveform y _i at the time of each evaluation time interval T _Eval by the number N of elements. That is, it is given by the following equation.

(Equation 2) The smaller the value of the square error, the higher the approximation accuracy of the approximate waveform. For the approximate waveform 52 of FIG.
_{When the} square error e _RMS ² is calculated with _Eval = 1 [ns], it becomes 0.023.

[0006]

For example, in a test of a semiconductor device, a waveform approximating an ideal input waveform is used as a test signal. Therefore, in order to perform a test with high accuracy, it is desirable to use a waveform that accurately approximates an ideal input waveform as a test signal. In the above-described conventional approximate waveform method, the time interval between the timings at which the values of the analog waveforms, which are ideal waveforms, are acquired is fixed at a fixed time. Therefore, even if the square error is large, it is difficult to reduce the square error, and sufficient approximation accuracy has not been obtained. as a result,
For example, it has been difficult to accurately test a semiconductor device.

Accordingly, an object of the present invention is to provide an approximate waveform generation method and a semiconductor test apparatus which can solve the above-mentioned problems. This object is achieved by a combination of features described in independent claims. The dependent claims define further advantageous embodiments of the present invention.

[0008]

According to a first aspect of the present invention, there is provided an approximate waveform generating method for generating an approximate waveform that approximates an analog waveform. There is provided an approximate waveform generating method, comprising: an approximate step of calculating an approximate value of a value of an analog waveform; and a timing correcting step of correcting each of a plurality of timings based on the approximate value.

In the first embodiment, the approximating step may include a timing setting step of setting each of a plurality of timings based on a curvature of the analog waveform. Also, in the approximation step, the time interval of a plurality of timings may be set short in a portion where the curvature of the analog waveform is large, and the time interval of the plurality of timings may be set long in a portion where the curvature of the analog waveform is small. In the timing correction step, each of the plurality of timings may be set to an optimal timing at which the square error between the analog waveform value and the approximate value at each timing is minimized.

In the approximation step, one of a plurality of predetermined values may be selected as the approximate value. The approximation step is
The approximating step may further include an initial setting step of presetting each of the plurality of values based on the analog waveform.

An initial setting step of acquiring an analog waveform value at more timings than the plurality of timings; a width determining step of determining a width of the analog waveform value to be approximated by each of the plurality of values; Of the values obtained in the obtaining step, a selecting step of selecting a value included in one of the widths, and for each value selected in the selecting step,
Allocating one of a plurality of values to a value that minimizes the sum of square errors.

A second aspect of the present invention is a semiconductor test apparatus for testing a semiconductor device, comprising: an input unit for inputting an analog waveform for testing the semiconductor device as time-series waveform data; An approximating unit that calculates an approximate value of the waveform data value, a timing correcting unit that corrects each of a plurality of timings based on the approximate value, and an analog value by receiving the approximate value at the timing corrected by the timing correcting unit. A waveform generation unit that generates an approximate waveform that approximates the waveform and inputs the approximate waveform to the semiconductor device; and determines whether the semiconductor device is good or bad based on a signal output from the semiconductor device when the approximate waveform is input to the semiconductor device. A semiconductor testing device comprising:

In a second embodiment, the waveform generating section has a plurality of rectangular wave generating sections for generating a rectangular wave based on the plurality of timings corrected by the timing correcting section and the approximate values at the corrected plurality of timings. Alternatively, an approximate waveform may be generated based on the rectangular waves generated by the plurality of rectangular wave generators. Further, the waveform generation unit may generate an approximate waveform by adding the rectangular waves generated by the plurality of rectangular wave generation units. The plurality of square wave generators may generate a square wave that can indicate a plurality of values, respectively.

Note that the above summary of the present invention does not enumerate all the necessary features of the present invention, and sub-combinations of these features can also constitute the present invention.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the invention according to the claims, and are described in the embodiments. Not all combinations of features are essential to the solution of the invention.

FIG. 4 shows a semiconductor test apparatus 1 according to the present invention.
00 shows an example of the configuration of 00. The semiconductor test apparatus 100 determines pass / fail of the semiconductor device 66. Semiconductor test equipment 1
00 denotes an input unit 12, an approximation unit 14, and a timing correction unit 1.
6, waveform generation unit 18, device contact unit 20, processing unit 22
And a determination unit 64. The input unit 12 receives time-series waveform data 56 representing an analog waveform for testing the semiconductor device 66. As an example, waveform data 5
Reference numeral 6 denotes a data group obtained by sampling an analog waveform at a predetermined cycle, or an analog waveform represented by a mathematical expression.

The approximating unit 14 calculates an approximate value of the value of the waveform data 56 at a plurality of timings. Approximator 14
May calculate the approximate value by selecting one of a plurality of predetermined values as the approximate value. For example, one of a plurality of predetermined values may be selected based on the value of the waveform data 56 and set as an approximate value. Timing correction unit 1
6 corrects each of the plurality of timings based on the approximate value calculated by the approximating unit 14 so that the square error between the value of the waveform data 56 and the approximate value is reduced.

The waveform generating section 18 receives the approximate value calculated by the approximating section 16 at a timing based on the timing corrected by the timing correcting section 16 and, based on the received timing and the approximate value, approximates the analog waveform. Is generated, and the generated approximate waveform is input to the semiconductor device 66 via the device contact unit 20.

The processing section 22 supplies a signal to the determination section 64 based on the output signal output from the semiconductor device 14 when the approximate waveform is input to the semiconductor device 66. The determination unit 64 determines the quality of the semiconductor device 66 based on the signal supplied from the processing unit 22 and the expected value signal 58. Expected value signal 58 is preferably a digital signal. At this time, if the output signal output from the semiconductor device 66 is an analog signal, the processing unit 22
May convert an analog signal output from the semiconductor device 66 into a digital signal and supply the digital signal to the determination unit 64. If the output signal output from the semiconductor device 66 is a digital signal, the processing unit 22 may supply the output signal to the determination unit 64 as a digital signal. The determination unit 64 includes a signal output from the processing unit 22 and
By performing matching with the expected value signal 58, the quality of the semiconductor device 14 is determined. Alternatively, the waveform generation unit 18 may generate the expected value signal 58 based on the generated approximate waveform, and supply the expected value signal 58 to the determination unit 64.

FIG. 5 illustrates an example of a method of correcting a plurality of timings at which the value of the waveform data 56 is obtained in the timing correction section 16. The analog waveform 50 is an analog waveform on which the waveform data 56 is based. The vertical axis of the graph shown in FIG. 5 indicates a voltage value, and the horizontal axis indicates time. One scale on the horizontal axis represents the minimum variable time of the timing. The waveform data 56 is preferably a data group obtained by sampling the analog waveform 50 at the cycle of the minimum variable time of the timing shown in FIG.

First, as an example, as shown in FIG. 5A, a plurality of timings T at which the value of the waveform data 56 is obtained are set.
₁ ,... T _k−1 , T _k , T _{k + 1} , T _{k + 2.}
Are arranged at regular time intervals. Also, a ₁ , a ₂ ,
a ₃ and a ₄ indicate values determined in advance as approximate values selected by the approximating unit 14. Examples timing below T _k, describing a method of correcting timing.

[0022] The timing _{T k,} the range can be moved on the horizontal axis is determined. In this example, the movement range is set from _{Tk (−2)} , which is moved two graduations to the left from the position shown in FIG. 5A, to Tk _(+2), which is moved two graduations to the right. Within the defined moving range, the timing T
_k can take five kinds of timings from T _{k (−2)} to T _{k (+2)} . At all timings, an error ΔV _k from an approximate value that can be selected by the approximation unit 14 is calculated, and ΔV _k is calculated.
T _k is set at a timing at which the square of _k is minimized. In this example, as shown in FIG. 5B, T _{k (−1)}
At the timing, the square error between the value of the waveform data 56 and the approximate value is minimized.

The operation described above is performed for all the timings at which the values of the waveform data 56 are to be obtained, and each of the timings is corrected. As shown in FIG. 5 (c), an approximate value with a small square error, in which the respective timings are optimized, is obtained.

In this embodiment, the timing to be corrected by the timing correction section 16 is determined based on the square error between the value of the waveform data 56 and the approximate value. In another example, each of the plurality of timings may be set based on the curvature of the analog waveform 50 represented by the waveform data 56. For example, a time interval of a plurality of timings may be set short in a portion where the curvature of the analog waveform 50 is large, and a time interval of a plurality of timings may be set long in a portion where the curvature of the analog waveform 50 is small. Further, in FIG. 5, the time intervals of the plurality of timings are initially arranged at regular intervals. However, each of the plurality of timings is first set based on the curvature of the analog waveform 50, and the respective set timings are described above. As described above, the timing may be corrected based on the square error between the value of the waveform data 56 and the approximate value.

FIG. 6 shows an approximation generated by the waveform generator 16 when the function representing the Lorentz waveform described with reference to FIG. 1 is given as waveform data 56 to the input unit 12 of the semiconductor test apparatus 100. A waveform 54 is shown. The analog waveform 50 shows a Lorentz waveform.

The approximating unit 14 calculates an approximate value of the value of the waveform data 56 at a plurality of timings as described with reference to FIG. As described with reference to FIG. 5, the timing correction unit 16 generates a plurality of timings based on the approximate value calculated by the approximation unit 14 so that the square error between the value of the waveform data 56 and the approximate value is reduced. Modify each of the. The waveform generation unit 18 receives the approximate value calculated by the approximation unit 16 at the timing corrected by the timing correction unit 16 at the timing corrected by the timing correction unit 16 as described with reference to FIG. And an approximate waveform 54 that approximates the analog waveform 50 based on the approximate value and the approximate value. In this example, the approximate value that can be selected by the approximating unit 14 and the value range of the analog waveform 50 to be approximated are the same as the input voltage range and the output voltage range described with reference to FIG.

FIG. 7 shows an example of the waveform data 56 described with reference to FIG. The timing in FIG. 7 is a timing at which the approximating unit 22 calculates an approximate value. When the square error e _RMS ² of the approximate waveform 56 generated in this example is calculated based on the values shown in FIG. 7, e _RMS ² = 0.0046. The evaluation time interval of the square error in this example is the same as the evaluation time interval used when calculating the square error in the conventional approximate waveform generation method described with reference to FIGS. As described above, the square error e _RMS ² when the same Lorentz waveform is approximated by the conventional approximate waveform generation method is e
_{Since RMS} ² = 0.023, by using the approximate waveform generation method of the present invention, in this example,
The square error could be reduced by about 80%.

In the present embodiment, the approximation unit 22 selects one of a plurality of predetermined values as the approximate value. The plurality of predetermined values as the approximate values are the center values of the widths of the values of the analog waveform to be approximated, but in other examples, each of the plurality of values is set in advance based on the analog waveform. You may. For example, the value of the analog waveform is obtained at a greater number of timings than the plurality of timings, the width of the value of the analog waveform to be approximated by each of the plurality of values is determined, and the determined value of the obtained analog waveform value is determined. May be selected, and one of a plurality of values may be assigned to a value that minimizes the sum of square errors for each of the selected values.

For example, when generating an approximate waveform of the analog waveform 50 described with reference to FIG.
The value of the analog waveform 50 is acquired at a time interval of 1 [ns]. Next, the width of the value of the analog waveform to be approximated by the approximate value is set for each approximate value. In this example, the same setting as the range described with reference to FIG. 2 is used. From the values of the acquired analog waveform 50, all values included in one of the set widths are selected. One of the approximate values is assigned to a value that minimizes or reduces the sum of square errors with all the selected values. The same operation is performed for each width.

For example, an approximate value in the width may be assigned to the average value of the acquired values of the analog waveform 50 included in one of the widths. Taking the range described with reference to FIG. 2 as an example, in the range from 0.00 to 0.25, 0.105 is an approximate value, and 0.25 to 0.50
In the range up to 0.356 is an approximate value, in the range from 0.50 to 0.75, 0.626 is an approximate value,
In the range from 0.75 to 1.00, 0.926 is an approximate value. Using the approximate values set in this way, FIG.
When the square error of the approximated waveform that approximates the Lorentzian waveform is calculated by the approximated waveform generation method of the present invention described in relation to the above, e _RMS ² = 0.0041, and the approximation accuracy is improved.

In the present embodiment, the width of the value of the analog waveform to be approximated to the approximate value is constant. In another example, the width of each value may be set so as to further reduce the square error. For example, the width of the value may be small in a portion where the curvature of the analog waveform is large, and the width of the value may be large in a portion where the curvature of the analog waveform is small.

FIG. 8 shows an example of the configuration of the waveform generator 18 of the semiconductor test apparatus 100. The waveform generator 18 includes an approximate voltage memory 24, a reference clock generator 26, a timing memory 28, a voltage generator 30, a timing controller 32, and an analog signal generator 34.

The approximate voltage memory 24 stores the analog waveform 50 at a plurality of timings input from the approximation unit 14.
Is stored. The timing memory 28 stores a plurality of timings at which approximate values of the analog waveform 50 have been obtained. The reference clock generator 26 outputs the reference clock to the approximate voltage memory 24 and the timing memory 28.
The approximate voltage memory 24 sequentially outputs the approximate values to the voltage generator 30 in synchronization with the reference clock,
Outputs the timing at which the approximate value is obtained in synchronization with the reference clock to the timing control unit 32 in order. The timing controller 32 outputs a clock to the voltage generator 30 at time intervals based on the input timing. Voltage generator 3
0 sequentially outputs signals based on the input approximate values to the analog signal generator 34 in synchronization with the input clock. The analog signal generator 34 generates an analog signal based on the signal output from the voltage generator 30 in synchronization with the clock, and inputs the analog signal to the semiconductor device 66 via the device contact unit 20. The analog signal generator 34 may generate an analog signal by passing a voltage sequence input from the voltage generator 30 through a low-pass filter, for example.

FIG. 9 shows an example of the configuration of the voltage generator 30. The voltage generator 30 includes a controller 36, a plurality of rectangular wave generators 38, and a calculator 60. The control unit 36 receives the approximate value of the analog waveform 50 from the approximate voltage memory 24, and receives a clock from the timing control unit 32. The controller 36 outputs a control signal to the plurality of rectangular wave generators 38 based on the approximate value and the clock. The plurality of rectangular wave generating units 38 generate rectangular waves based on the control signal at timings based on the control signal, respectively.
A signal is generated based on the rectangular waves generated by the plurality of rectangular wave generators.

The plurality of rectangular wave generators 38 may generate rectangular waves each of which can indicate a plurality of values. The plurality of rectangular wave generators 38 may generate a rectangular wave indicating a desired value at a desired timing. In addition, the calculation unit 60 may generate a signal by adding the rectangular waves generated by the plurality of rectangular wave generation units 38.

FIG. 10 shows an example of a signal generated by the voltage generator 30. In this example, the voltage generation unit 30 includes two rectangular wave generation units 3 of a rectangular wave generation unit 38a and a rectangular wave generation unit 38b.
An example provided with 8 will be described. The clock stage in FIG. 10 represents the timing of the clock output by the timing control unit 32, the Va stage represents the output signal generated by the rectangular wave generation unit 38a, the Vb stage represents the output signal generated by the rectangular wave generation unit 38b, The Vout stage represents a signal generated by the operation unit 60.

The rectangular wave generators 38a and 38b generate rectangular waves based on the logical value pattern output from the controller 36. When the lower order digit of the logical value pattern is 1, the rectangular wave generator 38a generates a 1V rectangular wave from the time when the clock signal is applied to the time when the next clock signal is applied. When the upper digit of the logical value pattern is 1, the rectangular wave generation unit 38b generates a 2V rectangular wave from the time when the clock signal is applied to the time when the next clock signal is applied.

The calculation unit 60 includes a signal Va generated by the rectangular wave generation unit 38a and a signal V generated by the rectangular wave generation unit 38b.
The signal Vout is generated by adding b to the signal Vout, and is output to the analog signal generator 34.

In this example, the arithmetic section 60 generates an approximate waveform by adding the signals generated by the rectangular wave generating section 38. In another example, an approximate waveform may be generated by an operation such as subtraction. In addition, the rectangular wave generation unit 38 outputs 0 V or 1
As in the case of the voltage value of V, two voltage values were shown. In another example, the rectangular wave generator 38 may take three or more voltage values. When the voltage generator 30 has n (n is a natural number) rectangular wave generators 38 and each of the n rectangular wave generators takes a voltage value of x value (x is a natural number), the arithmetic unit 60 The generated signal can take x ⁿ voltage levels.

According to the semiconductor test apparatus 100 described above, a plurality of timings for obtaining the value of the analog waveform are
Since the correction is made so as to reduce the square error, it is possible to generate an approximated waveform having a smaller error as compared with the conventional device.
As a result, the quality of the semiconductor device 66 can be more accurately determined.

FIG. 11 is a flowchart of an example of the approximate waveform generation method according to the present invention. In the approximation stage, an approximate value of an analog waveform value to be approximated at a plurality of timings is obtained (S100). The approximation step S100 includes:
The method may include a timing setting step of setting each of the plurality of timings based on the curvature of the analog waveform. In the timing setting step, a time interval of a plurality of timings may be set short in a portion where the curvature of the analog waveform is large, and a time interval of a plurality of timings may be set long in a portion where the curvature of the analog waveform is small. Approximation stage S
The 100 may obtain an approximate value of the analog waveform in the manner described in connection with FIGS. In the timing setting step, each of the plurality of timings may be set by the method described with reference to FIG.

Next, in the timing correction stage, each of the plurality of timings is corrected based on the approximate value calculated in the approximation stage (S120). In the timing correction step S120, each of the plurality of timings may be set to an optimal timing at which the square error between the analog waveform value and the approximate value at each timing is minimized. The timing correction step S120 may correct each of the plurality of timings according to the method described with reference to FIGS.

Next, in the approximate waveform generation step, an approximate waveform is generated based on the approximate value calculated in the approximate step S120 and the timing corrected in the timing correction step S120 (S140). The approximate waveform generation step S140 may generate an approximate waveform according to the method described with reference to FIGS.

In the approximation step S100, one of a plurality of predetermined values may be selected as the approximate value. Further, the approximation step S100 may further include an initial setting step of presetting each of a plurality of values predetermined as approximate values based on the analog waveform. The initial setting step includes an acquiring step of acquiring the value of the analog waveform at a greater number of timings than the plurality of timings, a width determining step of determining a value width of the analog waveform to be approximated by each of the plurality of values, and an acquiring step. Selecting a value included in one of the widths from the acquired values, and assigning one of the plurality of values to a value that minimizes the sum of square errors for each value selected in the selection step And an assignment stage. In the initial setting step, each of the plurality of values may be preset in the method described with reference to FIG.

FIG. 12 is a flowchart showing an example of the timing correction step S120. First, a plurality of timings are set at fixed time intervals (S102). Next, one of the timings is selected (S104). A timing changeable range is set for the selected timing (S106). An optimization timing at which the square error between the analog waveform and the approximate value is minimized in the timing changeable range is detected (S108). The detected optimization timing is recorded (S110). It is determined whether there is a timing that has not been optimized (S112). If there is a timing that has not been optimized, the process returns to S104, and one timing that has not been optimized is selected. If there is no unoptimized timing, that is, if all the timings have been optimized, the time interval optimization stage is ended.

According to the above-described approximate waveform generation method,
Since the multiple timings for acquiring the analog waveform value are corrected to the timing at which the error between the analog waveform value and the approximate value becomes smaller, an approximate waveform with a smaller error is generated compared to the conventional approximate waveform generation method. It is possible to do.

In the above embodiment, the approximate waveform generation method of the present invention is applied to the semiconductor test apparatus 100. However, it is clear from the above description that the present invention can also be applied to an arbitrary waveform generator that generates an analog waveform, a waveform comparator, a signal converter, and the like other than the semiconductor test apparatus 100.

Although the present invention has been described with reference to the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is apparent to those skilled in the art that various changes or improvements can be made to the above embodiment. It is apparent from the description of the appended claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

[0049]

As is apparent from the above description, according to the present invention, it is possible to generate an approximated waveform having a high approximate accuracy of a given analog waveform. Further, it is possible to accurately perform a test of a semiconductor device or the like using the approximate waveform.

[Brief description of the drawings]

FIG. 1 is a diagram showing an approximate waveform 52 generated by a conventional approximate waveform generation method.

FIG. 2 is a diagram showing a relationship between a value range of an analog waveform 50 and an approximate value.

3 is a diagram illustrating values of an analog waveform 50 and an approximate waveform 52. FIG.

FIG. 4 is a diagram illustrating an example of a semiconductor test apparatus 100 according to the present invention.

FIG. 5 is a diagram illustrating an example of a method of correcting a plurality of timings.

FIG. 6 shows an analog waveform 50 and an approximate waveform 5 according to the present invention.
FIG.

7 is a diagram showing values of an analog waveform 50 and an approximate waveform 54. FIG.

FIG. 8 is a diagram illustrating an example of a configuration of a waveform generation unit 18.

FIG. 9 is a diagram illustrating an example of a configuration of a voltage generation unit 30.

FIG. 10 shows an example of a signal generated by the voltage generator 30.

FIG. 11 is a diagram illustrating a flowchart of an example of an approximate waveform generation method according to the present invention.

FIG. 12 is a flowchart illustrating an example of a timing correction stage.

[Explanation of symbols]

12 input unit, 14 approximation unit 16 timing correction unit, 18 waveform generation unit 20 device contact unit, 22 processing unit 24 determination unit, 26 ... Reference clock generation unit 28 ... Timing memory, 30 ... Voltage generation unit 32 ... Timing control unit, 34 ... Analog signal generation unit 36 ... Control unit, 38 ... Square wave Generator 50: Arbitrary waveform, 52: Approximate waveform 54: Approximate waveform, 56: Ideal waveform 58: Expected value, 60: Operation unit 62: Device contact unit, 64 ... Processing unit 66 ... Semiconductor device, 100 ... Semiconductor test equipment

Claims (11)

[Claims] 1. An approximate waveform generating method for generating an approximate waveform that approximates an analog waveform, comprising: an approximate step of calculating an approximate value of the value of the analog waveform at a plurality of timings; A timing correction step of correcting each of the plurality of timings. 2. The method according to claim 1, wherein the approximating step includes a timing setting step of setting each of the plurality of timings based on a curvature of the analog waveform.
2. The method for generating an approximate waveform according to item 1. 3. The approximating step sets a short time interval between the plurality of timings in a portion where the curvature of the analog waveform is large, and increases a time interval between the plurality of timings in a portion where the curvature of the analog waveform is small. The method for generating an approximate waveform according to claim 2, wherein the setting is performed. 4. The timing correcting step sets each of the plurality of timings to an optimum timing at which a square error between a value of the analog waveform and the approximate value at each timing is minimized. 4. The method for generating an approximate waveform according to claim 1, wherein: 5. The approximate waveform generating method according to claim 1, wherein said approximating step selects one of a plurality of predetermined values as said approximate value. 6. The approximate waveform generating method according to claim 5, wherein the approximating step further includes an initial setting step of presetting each of the plurality of values based on the analog waveform. 7. The initial setting step includes: obtaining an analog waveform value at more timings than the plurality of timings; and a width of the analog waveform value to be approximated by each of the plurality of values. Determining a width, and selecting a value included in one of the widths from the values obtained in the obtaining step; and sum of square errors for each value selected in the selecting step. And allocating one of the plurality of values to a value that minimizes. 8. A semiconductor test apparatus for testing a semiconductor device, comprising: an analog waveform for testing the semiconductor device;
An input unit for inputting as time-series waveform data; an approximation unit that calculates an approximate value of the waveform data value at a plurality of timings; and a timing correction unit that corrects each of the plurality of timings based on the approximate value. Receiving the approximate value at the timing corrected by the timing correction unit, generating an approximate waveform approximating the analog waveform, and inputting the approximate waveform to the semiconductor device; A semiconductor test apparatus comprising: a determination unit configured to determine the acceptability of the semiconductor device based on a signal output from the semiconductor device when input to the semiconductor device. 9. The waveform generator includes a plurality of rectangular wave generators that generate a rectangular wave based on the plurality of timings corrected by the timing corrector and the approximate value at the corrected plurality of timings. The semiconductor test apparatus according to claim 8, wherein the approximate waveform is generated based on the rectangular waves generated by the plurality of rectangular wave generators. 10. The semiconductor test apparatus according to claim 9, wherein the waveform generation unit generates the approximate waveform by adding the rectangular waves generated by the plurality of rectangular wave generation units. . 11. The semiconductor test apparatus according to claim 9, wherein each of the plurality of rectangular wave generators generates a rectangular wave that can indicate a plurality of values.