JP2000074985A - Survey point obtaining method in ic testing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically shorten the measuring time of a device to be tested as a whole and reduce the production cost of a measuring device as a whole. SOLUTION: The survey point obtaining method in IC testing is to give two additional values form an impressing system 10A of an IC test device 1 to a device to be tested 2, takes in a measured value from the device to be tested 2 into the measuring system 10B of the IC test device 1 and obtain a variation point to be a reference for determining which of pass region or fail region the measured value comes in by a binary search method. Here, the region where the number of the variation points concentrate in a wafer unit and a lot unit in a device production process is limited as a survey region and survey with the binary search method is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a search point acquisition method in an IC test for acquiring a search point to be used as a pass / fail decision criterion of a device by a binary search method in an IC test apparatus.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing a general IC test apparatus. In the figure, reference numeral 1 denotes an IC test device,
This has an application system 10A and a measurement system 10B. According to this, an additional value is given from the application system 10A to the device under test 2, and the measurement result is taken into the measurement system 10B. The binary search method is a method in which some additional values are given from the application system 10A to the device under measurement 2 and the search points are investigated based on the values taken from the device under measurement 2 into the measurement system 10B. FIG. 5 is an input / output characteristic diagram of the device under test 2. In FIG.
A method for acquiring data using the binary search method in the IC test apparatus 1 will be described with the SS test area and the reference value or less as a fail area. FIG. 6 is a flowchart showing the procedure of data acquisition by the binary search method. The points searched for and obtained are the changing points of the pass area and the fail area. The change point of the pass area and the fail area is determined by the application system 10A.
It is assumed that there is only one point within the search range L between the point A and the point B of the additional value given to the device under test 2 from. First, in the IC test apparatus 1, the application system 10A
Search range L of additional value given to device under test 2 from
Is specified (step S1). Then, this search range L
It is tested whether the points A and B that determine the position are in the pass area or the fail area (steps S2 and S3).

When the test results at points A and B indicate that both measured values are in a pass area or a fail area as shown in FIG. 5, the change point to be found does not exist within the designated search range. In this case, the search ends (step S4). On the other hand, point A is in the fail area and B is
If the point is in the path area, the change point to be found will be between point A and point B. Then, at this point, point C = [(A + B) / 2] which is an intermediate point between points A and B,
The test is performed again as described above (step S5). And
As a result of the measurement by the retest, when the point C is in the fail area, the change point to be found exists between the point C and the point B. Then, the test is performed again in the same manner as described above at point D = [(C + B) / 2], which is an intermediate point between points C and B (step S6).

As a result of this measurement, if the point D is in the fail area, the change point to be found will be between the points D and B. Therefore, the test is performed again at point E, which is an intermediate point between point D and point B = [(D + B) / 2] (step S7). As a result of the measurement by this test, when the point E is in the pass area, the change point to be found exists between the point D and the point E. Therefore, the test is performed again at point F = [(D + E) / 2], which is an intermediate point between points D and E (step S8). Since the measurement result at the point F is a pass point, the change point to be found exists between the point D and the point F. Then, in the same manner as described above, the test is sequentially repeated until the minimum resolution that can be searched between the point D and the point F, and the change point is obtained.

[0005]

However, in such a conventional search point acquisition method in an IC test, evaluation of a device under test is performed by using a binary search method and executing a test based on a device program to execute device test. Good,
Since the measurement is performed by determining a defect, there is a problem that the measurement time is prolonged when mass-producing the device to be measured, and the cost of the entire device to be measured cannot be avoided.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem. In the case of a device program for repeatedly measuring the same test item by a binary search method, the same measurement frequency is reduced,
The measurement time can be significantly reduced for the entire device under test,
Therefore, the manufacturing cost of the entire device under test can be reduced.
The purpose is to obtain a search point acquisition method in the C test.

[0007]

In order to achieve the above object, a search point acquiring method in an IC test according to the present invention provides two additional values to a device under test from an application system of an IC test apparatus. From the device under test to the IC
A search point acquisition method in an IC test in which a measurement value is taken into a measurement system of a test apparatus and a change point serving as a criterion for determining whether the measurement value falls into a pass area or a fail area by a binary search method, The search by the binary search method is performed by limiting a range in which the number of the change points is concentrated on a wafer or lot basis in a device manufacturing process as a search range.

According to a second aspect of the present invention, there is provided a search point acquiring method in an IC test in which a binary search is performed by changing the search range every time a test is executed.

According to a third aspect of the present invention, there is provided a method for acquiring a search point in an IC test, in which an initial search range is specified for a measured value from a device to be measured for two additional values, and the measured value within this search range is A measurement is performed to determine whether the point is in the pass area or in the fail area. Subsequently, a search range in which the number of change points determined by the binary search method is concentrated is specified between two additional values. It is checked whether or not there is a change point to be searched for.If there is a change point to be found within the search range, the next device test is performed using the same additional value as specified above, while If there is no change point to be found within the search range obtained, measurement is performed by specifying the initial search range, and if the change point to be found is within the specified search range, the measurement result indicates that the specified search range When outside Is the measurement result that determined as the two additional values that specifies the specified search range of the.

According to a fourth aspect of the present invention, there is provided a method for acquiring a search point in an IC test in which a measurement value within the initial search range is in a pass area or a fail area when a wafer is switched in a device manufacturing process. Returning to the measurement procedure, the binary search is restarted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The search point acquisition method in the IC test according to the present invention uses the block diagram shown in FIG.
This is performed by a method as shown in FIGS. Also,
Generally, the number of change points obtained for the search range obtained by the binary search method is as shown in a histogram in FIG. The tendency of the number of change points thus obtained to fall within a certain range can be seen for each wafer or lot in the device manufacturing process. The present invention can reduce the number of searches by focusing on such characteristics and limiting the test search range. That is, in the present invention, the search range is changed every time the test is executed, and the binary search is performed.

Next, referring to FIG. 2, an area I or more according to the present invention is defined as a pass area, and an area below the reference value S is defined as a fail area.
A method of acquiring data as a search point by using the binary search method in the C test apparatus 1 will be described.
The procedure for acquiring data by the binary search method is as shown in the flowchart of FIG. In the binary search according to the present invention, the search ranges A ′ and B ′ are in an indeterminate state until the first measurement result is obtained, and the above-described binary search method according to the related art is used. If the change point can be obtained once, in the subsequent tests, the minimum value of the obtained measurement results is designated as A 'and the maximum value is designated as B', and the search range L1 between the points A 'and B' is determined. Decide and test. The procedure is described below. Here, the points A 'and B' do not exceed the range between the points A and B of the initial value of the search range.

That is, first, until the first measurement result is obtained, the measured values are fetched from the device under test 2 by the binary search method according to the prior art in steps S1 to S8 of the flowchart of FIG. Data search is performed (step S11). When the first measurement result is obtained, the minimum value of the obtained measurement results is set to A 'and the maximum value is set to B' (step S12). Therefore, in the next test, measurement is performed by designating the search range L1 between the points A 'and B' (step S13). Next, it is checked whether or not a change point exists within the search range L1 (step S14). If no change point exists within the designated search range L1, points A and B, which are initial values, are included in the search range L1. A change point is determined by designating a search range L between points (step S1).
5). If both the measurement results at points A and B are pass points or fail points, the change point to be found does not exist within the designated search range, and in this case, the search is terminated. (Step S16).

On the other hand, if it is determined in step S14 that a change point exists within the designated search range L1, the next device test is repeated using the same values A 'and B'. When the measurement result is obtained, the value is compared with A 'and B'. If the measurement result is out of the search range L1, it is changed as follows (step S17). That is, when the measurement result is smaller than A ', the measurement result is set to A'. On the other hand, when the measurement result is larger than B ',
The measurement result is defined as B '. Thus, step S13
The test from step S17 to step S17 is repeated, and the search range L1 is determined based on the measurement result every time the test is executed. Then, if the tendency is shown by the histogram in FIG. 4, the search range L1 converges to a certain range within the initial value L, that is, the search range L1 is narrower than the search range L of the initial value. It is possible to reduce the number of data searches in the search method.
Therefore, as the number of tests in the range specification in the search range L1 increases, the number of tests performed in the conventional search range L becomes larger.
The total test time required for device evaluation can be reduced.
In consideration of the fact that the search range L1 changes in units of lots and wafers of the device under test 2 and returns to step S11 at the wafer switching, the binary search is started.
This leads to an improvement in the effect of shortening the test time.

[0015]

As described above, according to the present invention, the IC
Two additional values are given from the application system of the test apparatus to the device under test, and the measured values are fetched from the device under test into the measurement system of the IC test apparatus. A search point acquisition method in an IC test for finding a change point that is a reference for determining whether to enter, wherein a range in which the number of the change points is concentrated on a wafer or lot unit in a device manufacturing process is limited as a search range, Since the search is performed by the binary search method, the number of data searches can be reduced when acquiring data in an IC test apparatus, and as a result, the time and manufacturing cost of the entire device test can be significantly reduced. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a general configuration of an IC test apparatus.

FIG. 2 is an explanatory diagram showing a search point acquisition method in an IC test according to the present invention.

FIG. 3 is a flowchart showing an execution procedure of a search point acquisition method in an IC test according to the present invention.

FIG. 4 is a histogram showing a search result obtained by a binary search method of the present invention.

FIG. 5 is an explanatory diagram showing a search point acquisition method in a conventional IC test.

FIG. 6 is a flowchart showing an execution procedure of a search point acquisition method in a conventional IC test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IC test apparatus 2 Device under test 10A Application system 10B Measurement system

Claims (4)

[Claims] 1. Two additional values are given to a device under test from an application system of an IC test apparatus, and measured values are taken into the measurement system of the IC test apparatus from the device under test, and the measured values are passed by a binary search method. In a search point acquisition method in an IC test for finding a change point that is a reference for determining whether to enter a region or a fail region, a range in which the number of the change points is concentrated on a wafer or lot unit in a device manufacturing process is set as a search range. A search point acquisition method in an IC test, wherein a search by the binary search method is performed in a limited manner. 2. The IC according to claim 1, wherein the binary search is performed by changing the search range every time a test is executed.
Search point acquisition method for testing. 3. An initial search range is specified for the measured values for the two additional values, and a measurement is performed to determine whether the measured values within the search range are in a pass area or a fail area. A search range in which the number of change points to be obtained by the search method is concentrated is specified between two additional values, and it is checked whether or not there is a change point to be found in the specified search range. If there is, the next device test is performed using the same additional value as specified above, while if there is no change point to be found within the specified search range, the initial search range is If the measured values corresponding to the two additional values that specify the initial search range are both in the pass area or the fail area, it is determined that the change point to be found is not within the specified search range. And, on the other hand, If the change point falls within the specified search range, when the measurement result is out of the specified search range, the measurement result is determined as two additional values that specify the specified search range. The I according to claim 1, wherein
Search point acquisition method in C test. 4. The method according to claim 1, wherein when the wafer is switched in the device manufacturing process, the process returns to the measurement procedure as to whether the measurement value within the initial search range is in the pass area or the fail area, and the binary search is restarted. A search point acquisition method in the IC test according to claim 3.