JP4577506B2 - Semiconductor device test method and standard value determination method - Google Patents

Description

  The present invention relates to a test method for a semiconductor device suitable for testing a semiconductor device, particularly an RBSOA tolerance of an IGBT, and a standard value determining method for determining a standard value used in the test method.

The RBSOA (Reverse Biased Safe Operating Area) represents the non-destructive operation range of the collector-emitter voltage and collector current accompanying the turn-off of the IGBT (Insulated Gate Bipolar Transistor). The wider the range, the higher the non-destructive performance against reverse bias.
Therefore, conventionally, techniques for improving RBSOA tolerance have been proposed. According to this, there is an advantage that RBSOA tolerance can be improved without deteriorating characteristics such as on-voltage and switching loss (see Patent Document 1).

JP 2004-228175 A

However, in the above-described prior art, no consideration is given to the test method for evaluating the RBSOA tolerance, and there are the following problems.
That is, the nondestructive performance of the IGBT with respect to the reverse bias is verified by the RBSOA tolerance test, and this guarantees the RBSOA tolerance. In this test, for example, a voltage (rated voltage) of several hundred volts is applied to the IGBT. It is necessary to energize 100A (twice the rated current). This is because the RBSOA tolerance is a breakdown tolerance under a test condition close to the actual use state, and in particular, with respect to the current, it is usual to guarantee about twice the rated current.
On the other hand, a wafer tester, chip tester or the like (hereinafter referred to as a wafer tester or the like) used for testing a general semiconductor element (chip) can only flow a current of about several tens of A due to probe limitations. For this reason, it is necessary to use a curve tracer or the like after the semiconductor element is assembled in a module state in the test for assuring the RBSOA tolerance.
However, in the method in which the test is performed after the assembly in the module state, the throughput is several minutes / unit, which is extremely low compared to the few seconds / unit in the wafer test performed in the chip state. In addition, when a defective element (an element whose RBSOA tolerance cannot be guaranteed: an abnormal product) is found in the module state, the cost loss is increased by the extra module assembly cost compared to the case where it is found in the chip state. For this reason, the cost for finding a defective element has become extremely high.

  The present invention has been made in view of the above circumstances, and a semiconductor device test method and test capable of greatly improving the throughput of the RBSOA tolerance test and greatly reducing the cost for finding a defective device. It is an object of the present invention to provide a standard value determination method for performing pass / fail judgment in a method.

In order to achieve the above object, a test method for a semiconductor device according to claim 1 is characterized in that an avalanche resistance test is performed on any one of a plurality of samples of a semiconductor device to be tested on a wafer surface. The avalanche resistance data is obtained, and the RBSOA tolerance test is performed on a sample adjacent to the sample used for the acquisition of the avalanche resistance data among the plurality of samples to obtain the RBSOA tolerance data. The RBSOA tolerance and the avalanche are obtained from both data. Correlation data of withstand capability is obtained, and from this correlation data, a standard value for pass / fail judgment of an avalanche withstand test performed as an alternative to the RBSOA withstand test is determined, and the avalanche withstand capability performed for the semiconductor device under test using this standard value The test pass / fail judgment result is shown as RBSO of the semiconductor device under test. Characterized by the acceptance determination result in immunity.
In the invention according to claim 2, the RBSOA resistance test is performed on any one of the plurality of sample groups of the semiconductor device to be tested on the wafer surface, and an abnormal product of RBSOA resistance is screened. A standard value 1 of RBSOA tolerance that is possible and does not lead to destruction of a normal product is determined, and the standard value of the RBSOA tolerance of the plurality of sample groups is determined using the determined standard value 1 as a standard value for pass / fail judgment. An RBSOA tolerance test is performed on a sample group different from the sample group used for the determination of 1 to screen a normal product of RBSOA tolerance, and an avalanche tolerance test is performed on the normal product of RBSOA tolerance obtained by this screening. The value within the area near the lower limit of the normal product distribution and below the lower limit is used as an alternative to the RBSOA tolerance test. The standard value 2 for determining whether or not the avalanche resistance test is acceptable, and using the standard value 2 to determine whether or not the avalanche resistance test is performed on the test target semiconductor element is the pass / fail determination result for the RBSOA resistance of the test target semiconductor element. It is characterized by.
The invention according to claim 3 of the claims determines a standard value for pass / fail judgment of an avalanche resistance test performed as an alternative to the RBSOA resistance test from a plurality of samples of the semiconductor device to be tested on the wafer surface. there the decision method of the standard value of definitive to test methods of the semiconductor device according to acceptance judgment result of the RBSOA capability of the tested semiconductor devices acceptability judgment result of the avalanche resistance test performed on the test subject semiconductor device using Then, an avalanche resistance test is performed for any one of the plurality of samples to obtain avalanche resistance data, and an RBSOA resistance is measured for a sample adjacent to the sample used for acquiring the avalanche resistance data among the plurality of samples. RBSOA tolerance data is obtained by testing, and RBSOA is obtained from both data. It acquires correlation data quantity and avalanche withstand capability, and determines the standard value from the correlation data.
The standard value determination method according to claim 4 of the claims is to determine a standard value 2 for pass / fail judgment of an avalanche resistance test performed as a substitute for the RBSOA resistance test from a plurality of sample groups of semiconductor devices to be tested on the wafer surface. Then, the standard value 2 in the semiconductor element test method in which the pass / fail judgment result of the avalanche resistance test performed on the test target semiconductor element using the standard value 2 is used as the pass / fail judgment result of the RBSOA resistance test of the test target semiconductor element. The RBSOA tolerance test is performed so that an RBSOA tolerance test can be performed on any one of the plurality of sample groups so that an abnormal RBSOA tolerance product can be screened and a normal product is not destroyed. A standard value 1 is determined, and the determined standard value 1 is used as a standard value for the pass / fail judgment, and the R among the plurality of sample groups. An RBSOA tolerance test is performed on a sample group different from the sample group used to determine the standard value of SOA tolerance, and a normal product of RBSOA tolerance is screened, and the normal product of RBSOA tolerance obtained by this screening is obtained. An avalanche resistance test is performed, and the standard value 2 is determined from a value within a region near the lower limit value that is not more than the lower limit value of the normal product distribution.

According to the first aspect of the present invention, the avalanche resistance test that can be tested with a wafer tester or the like can be performed as an alternative to the RBSOA resistance test that is difficult to test with a wafer tester or the like. The RBSOA tolerance test that has been performed later can be performed in a chip state. Therefore, the throughput of the RBSOA tolerance test can be greatly improved, and the cost for finding a defective element can be greatly reduced.
According to the second aspect of the present invention, the semiconductor element can be tested using a standard value different from that of the first aspect of the invention. The degree of freedom in selecting standard values used for testing can be expanded. Specifically, a semiconductor element can be tested by arbitrarily selecting any standard value according to various conditions.
According to the invention described in claim 3 of the appended claims, is used in the method of testing a semiconductor device according to claim 1, determine the standard values of the acceptance judgment of avalanche resistance test carried out as an alternative to the RBSOA capability test it can.
According to the invention described in claim 4 , the standard value of the pass / fail judgment of the avalanche resistance test used as an alternative to the RBSOA resistance test used in the semiconductor element test method according to claim 2 can be determined. .

Hereinafter, embodiments of the present invention will be described. Prior to that, RBSOA tolerance and avalanche tolerance will be described, and then the outline of the present invention will be described.
First, the RBSOA tolerance will be described. This RBSOA tolerance is one of the tolerances to be guaranteed for the IGBT. This is measured by a test that evaluates how much current can flow without destroying the IGBT when the voltage is fixed at a certain value when the IGBT is turned off (when the current and voltage become maximum values). It is withstand. Usually, about twice the rated current is guaranteed.
In addition, the avalanche resistance is the resistance measured by a test in which energy stored in the inductance is applied to the IGBT when the IGBT is turned off and the energy that the element breaks is evaluated.
In the following description, the circuits used in the respective tests for evaluating RBSOA tolerance and avalanche tolerance (RBSOA tolerance test and avalanche tolerance test) are all normally used in this type of test.

First, with respect to the sample (chip) of the IGBT to be tested specially prepared for this experiment, each defect rate (probability of abnormal products appearing) in the RBSOA tolerance test and avalanche tolerance test conducted by the present inventors, and avalanche tolerance The RBSOA failure rate after screening in the test was several percent (almost the same value) for the former two and almost 0% for the latter.
As shown in FIG. 1, the RBSOA defect rate after screening in the avalanche resistance test is about 0% for the remaining samples after screening for avalanche resistance abnormal products by applying a constant avalanche stress in the avalanche resistance test. RBSOA defective rate.

According to each defect rate above,
(1) The defect rate in the RBSOA tolerance test and the defect rate in the avalanche tolerance test are approximately the same,
(2) No abnormal RBSOA product exists after screening for an abnormal avalanche product in the avalanche test.
I understand.
From these (1) and (2), the present inventor
(3) There is a correlation between RBSOA tolerance and avalanche tolerance,
(4) RBSOA tolerance abnormal products (IGBT with low RBSOA tolerance) can be screened by an avalanche tolerance test,
Newly found.

Both the RBSOA tolerance and the avalanche tolerance are reduced by factors such as non-uniform formation of the body diffusion layer, local thinning of the gate oxide film, etc., causing current to flow non-uniformly. The normal products show different destruction mechanisms, and the energy leading to the destruction is also different, but the abnormal factors of the RBSOA tolerance abnormal product and the avalanche tolerance abnormal product are the same. Therefore, the present inventor considered that it would be possible to screen RBSOA tolerance abnormal products by an avalanche tolerance test, and realized the present invention.
As described above, the RBSOA tolerance test is a test in which a large current is passed, and it is difficult to perform a total number test using a current wafer tester or the like, and it is necessary to perform a test after the elements are assembled in a module state. However, if an avalanche resistance test that can be tested using a wafer tester or the like can be performed as an alternative to the RBSOA resistance test, a test for assuring the RBSOA resistance can be performed at a high throughput, and a defective element can be found. Cost can be greatly reduced.
According to the newly found (3) and (4) above, the standard value for pass / fail judgment of the avalanche resistance test for screening RBSOA resistance abnormality products is determined, and the avalanche resistance test is performed with this standard value. For example, it has been concluded that an RBSOA tolerance test can be realized that can greatly improve the throughput and significantly reduce the cost for finding a defective element.

In the following, based on the above (3) and (4), a method for determining the pass / fail judgment standard value of the avalanche resistance for screening RBSOA tolerance abnormal products, in other words, for guaranteeing the RBSOA tolerance will be described.
First, as a first example, a method for determining a standard value for determining whether or not avalanche resistance is acceptable from the correlation between RBSOA resistance and avalanche resistance will be described.
In this first example, RBSOA tolerance and avalanche tolerance are measured for adjacent chips (IGBT elements) on the wafer, respectively, and an RBSOA tolerance-avalanche tolerance correlation graph (correlation data) is created. In this method, an avalanche resistance capable of guaranteeing a desired RBSOA resistance is read, and this is used as a standard value for determining whether or not the avalanche resistance is acceptable.

Details of the first example will be described below with reference to FIGS.
Since the chip after the measurement of the RBSOA resistance and the avalanche resistance is broken by the measurement, it is impossible to measure both the RBSOA resistance and the avalanche resistance for a specific chip. On the other hand, since the element characteristics on the wafer have in-wafer dependence, it is considered that the characteristics of the adjacent chips 32 and 32 on the wafer 31 shown in FIG.
Therefore, if one of the adjacent chips 32 and 32 measures the RBSOA tolerance, and the other measures the avalanche tolerance, the measurement result is the RBSOA tolerance of a specific chip at the position of the adjacent chips 32 and 32. And it can be considered that it is a measurement result of avalanche tolerance.
Therefore, RBSOA tolerance and avalanche tolerance are measured separately using adjacent chips 32 and 32 on the wafer 31, and the correlation data is obtained assuming that the values are the RBSOA tolerance and avalanche tolerance of one chip at that location. Then, a RBSOA tolerance-avalanche tolerance correlation graph is created.
FIG. 3 shows the RBSOA tolerance-measured by measuring the RBSOA tolerance and the avalanche tolerance in the above-described procedure for a large number of adjacent chips 32, 32 on the wafer 31, and obtaining correlation data for both tolerances. It is a figure which shows typically an avalanche tolerance correlation graph (straight line 41). A region 42 in the figure shows an outline of the range of the correlation distribution.

FIG. 4 is a graph (straight line 51) showing an example of the RBSOA tolerance-avalanche tolerance correlation obtained by actually conducting the RBSOA tolerance test and the avalanche tolerance test in the same procedure as described above for the sample (chip) of the IGBT to be tested. ).
This straight line 51 is a graph in which the avalanche resistance is uniquely obtained from the RBSOA resistance, and as an example, in the xy coordinate system shown in FIG. 4 where the RBSOA resistance is taken in the x-axis direction and the avalanche resistance is taken in the y-axis direction. = 0.0093x-4.9466, and the correlation coefficient in this case was 0.8134. As in the general example, the RBSOA tolerance test was performed in a high temperature = 150 ° C. environment, and the avalanche resistance test was performed in a room temperature = 25 ° C. environment.
In the first example, the avalanche resistance that can guarantee the desired RBSOA tolerance is read from the graph shown in FIG. 4, and this is used as a standard value for determining whether or not the avalanche resistance is acceptable (pass / fail judgment of the avalanche tolerance test performed as an alternative to the RBSOA tolerance test). Standard value). For example, when the RBSOA tolerance 600A should be guaranteed, according to the straight line 51 shown in FIG. 4, the corresponding avalanche tolerance (standard value of the pass / fail judgment) is about 0.63J.
Therefore, for each chip (test target IGBT element) designed and created in the same manner as described above, the avalanche resistance 0.63J is used as the standard value for pass / fail judgment, and the RBSOA resistance is evaluated. A test guaranteeing 600A has been conducted. That is, a test for assuring the RBSOA tolerance test can be performed by a wafer test or the like performed in a chip state, the throughput of the RBSOA tolerance test can be greatly improved, and the cost for finding a defective element can be greatly reduced.

Next, a second example will be described.
The second example is a method of determining the standard value for the pass / fail judgment of the avalanche resistance from the avalanche resistance distribution of the normal RBSOA tolerance.
In the second example, first, an avalanche resistance test is performed by using a plurality of chips as samples (first sample group) from a large number of chips (IGBT elements) on the wafer to obtain an avalanche resistance distribution (see FIG. 5). ). This is to confirm that the distribution of the characteristics of the chip to be performed later can be clearly classified into normal products and abnormal products.
Next, an RBSOA tolerance test is performed using a plurality of chips different from the avalanche tolerance distribution as a sample group (second sample group), and the RBSOA tolerance measurement result of the sample that can be regarded as normal RBSOA tolerance The standard value is determined so that an abnormal product of the RBSOA tolerance can be surely screened and the normal RBSOA tolerance will not be destroyed.
Next, a plurality of chips different from the first and second sample groups are used as a sample group (third sample group), and the third sample group is determined using the second sample group. The RBSOA tolerance test is performed using the standard value as the standard value for pass / fail judgment, and normal products are screened.
Then, the avalanche resistance test is performed on the normal product obtained by this screening, and the lower limit value of the normal product distribution is set as the standard value for the pass / fail judgment of the avalanche resistance test that guarantees the RBSOA resistance. The lower limit value does not need to be a (actual) lower limit value in a strict sense, and is the median value of the boundary area of the distribution of normal products and abnormal products classified using the first sample group (see FIG. 5), a value lower than the actual lower limit value may be used as long as it is a value on the normal product side than the median value. That is, the value may be any value that is equal to or lower than the lower limit value and within the vicinity of the lower limit value.

The details of the second example will be described below with reference to FIGS.
As described above, first, an avalanche resistance test is performed by using a plurality of chips as samples (first sample group) from a large number of chips (IGBT elements) on the wafer to obtain an avalanche resistance distribution. Is divided into a distribution of normal products and abnormal products (see FIG. 5). In the second example, a sample of an element having a rating different from that of the element used in the description of the first example is used.
Next, an RBSOA tolerance test is performed on the second sample group different from the chip that has obtained the avalanche tolerance distribution, and the RBSOA tolerance measurement result of the sample in which the RBSOA tolerance is normal indicates an incorrect RBSOA tolerance product. The standard value is determined so that it can be screened without damaging the RBSOA tolerance of normal products.
Next, with respect to a plurality of third sample groups different from the first and second sample groups, an RBSOA tolerance test is performed using the standard value determined using the second sample group as a standard value for pass / fail judgment, and normal Perform product screening. For example, since the tested RBSOA tolerance average value for the five samples (second sample group) of the IGBT chip to be tested was 851A, the standard value of the above pass / fail judgment was set to 800A, and this 800A was a normal product. Was screened. In this case, the breakdown tolerance (RBSOA tolerance) of the abnormal product was about 300 A (see FIG. 6).
Then, the avalanche resistance test is performed on the normal product obtained by this screening, and the lower limit value of the normal product distribution is set as the standard value for the pass / fail judgment of the avalanche resistance test that guarantees the RBSOA resistance. The lower limit value does not need to be a (actual) lower limit value in a strict sense, and is the median value of the boundary area of the distribution of normal products and abnormal products classified using the first sample group (see FIG. 5), a value lower than the actual lower limit value may be used as long as it is a value on the normal product side than the median value.
Next, as a result of the screening at 800A, an avalanche resistance test is performed on the normal product of RBSOA resistance obtained, and an avalanche resistance distribution is obtained for the normal product. The lower limit value of this distribution is used as a standard value for pass / fail judgment of an avalanche resistance test (an avalanche resistance test performed as an alternative to the RBSOA resistance test) that guarantees RBSOA resistance. In the IGBT chip used as a sample, the lower limit value of the avalanche resistance distribution of the RBSOA resistance normal product was 1.5 J, so the standard value of the above pass / fail judgment was set to 1.5 J (see FIG. 7).
Therefore, for each chip (test target IGBT element) on a shipping wafer designed and created in the same manner as described above, the avalanche resistance 1.5J is used as a standard value for pass / fail judgment, and RBSOA resistance is evaluated. A test to assure 800A has been conducted. That is, a test for assuring the RBSOA tolerance test can be performed by a wafer test or the like performed in a chip state, the throughput of the RBSOA tolerance test can be significantly improved, and the cost for finding a defective element can be greatly reduced.

It is a figure for demonstrating the RBSOA defect rate after screening by the avalanche tolerance test in FIG. It is a top view which shows a wafer for explaining a 1st example of a method of the present invention partially notched. It is a figure which shows typically the RBSOA tolerance-avalanche tolerance correlation graph for demonstrating a 1st example. It is a graph which shows the example of the RBSOA tolerance-avalanche tolerance correlation obtained by actually testing about a sample. It is an avalanche capability distribution map for demonstrating the 2nd example of the method of this invention. It is a RBSOA tolerance distribution map for demonstrating a 2nd example similarly. It is an avalanche tolerance distribution figure which shows the decision value of the standard value of the pass / fail judgment with respect to the avalanche tolerance distribution of a normal RBSOA tolerance.

Explanation of symbols

31: Wafer, 32: Chip, 41, 51: Straight line (RBSOA tolerance-avalanche tolerance correlation graph)

Claims (4)

The avalanche resistance data is obtained by performing an avalanche resistance test for any one of the plurality of samples of the semiconductor device to be tested on the wafer surface, and the sample used for acquiring the avalanche resistance data among the plurality of samples. RBSOA tolerance test is performed for adjacent samples to obtain RBSOA tolerance data, correlation data between RBSOA tolerance and avalanche tolerance is obtained from both data, and pass / fail judgment of avalanche tolerance test performed as an alternative to RBSOA tolerance test is obtained from this correlation data And a pass / fail judgment result of an avalanche resistance test performed on the test target semiconductor element using the standard value as a pass / fail judgment result of the RBSOA resistance of the test target semiconductor element. Device testing method. An RBSOA tolerance test is performed on any one of a plurality of sample groups of the semiconductor device to be tested on the wafer surface, and an RBSOA tolerance tester can be screened for an abnormal product of RBSOA tolerance and the normal product is not destroyed. And a sample group different from the sample group used to determine the standard value 1 of the RBSOA tolerance among the plurality of sample groups. An RBSOA tolerance test is conducted to screen normal products of RBSOA tolerance, and an avalanche tolerance test is performed on the normal products of the RBSOA tolerance obtained by this screening. Standard value for pass / fail judgment of avalanche tolerance test in which the value in the vicinity of the value is substituted for RBSOA tolerance test Determined as, it said to Rukoto and acceptance judgment result of the RBSOA capability of the tested semiconductor devices acceptability judgment result of the avalanche resistance test performed on the test subject semiconductor device by using the standard value 2 half Conductor element testing method. A standard value for pass / fail judgment of an avalanche resistance test performed as an alternative to the RBSOA resistance test is determined from a plurality of samples of the semiconductor element under test on the wafer surface, and the avalanche resistance performed on the test target semiconductor element using this standard value wherein a method for determining the standard value for definitive acceptance or rejection determination result of the test to test methods of the semiconductor device according to acceptance judgment result of the RBSOA capability of the tested semiconductor devices,
An avalanche resistance test is performed on any one of the plurality of samples to acquire avalanche resistance data, and an RBSOA resistance test is performed on a sample adjacent to the sample used for acquiring the avalanche resistance data among the plurality of samples. A standard value determination method comprising: obtaining RBSOA tolerance data, obtaining correlation data between RBSOA tolerance and avalanche tolerance from both data, and determining the standard value from the correlation data. A standard value 2 for determining whether or not the avalanche resistance test is performed as an alternative to the RBSOA resistance test is determined from a plurality of sample groups of the test target semiconductor elements on the wafer surface. A determination method of the standard value 2 in the test method of a semiconductor device, in which the pass / fail judgment result of the avalanche withstand test is the RBSOA tolerance test result of the semiconductor device under test,
An RBSOA tolerance test is performed for any one of the plurality of sample groups, and an RBSOA tolerance standard value that can be screened for abnormal RBSOA tolerance products and does not lead to destruction of normal products is determined. Using the determined standard value 1 as a standard value for pass / fail judgment, an RBSOA tolerance test is performed on a sample group different from the sample group used for determining the standard value of the RBSOA tolerance among the plurality of sample groups. The normal product of the RBSOA resistance obtained by this screening is subjected to an avalanche resistance test, and the standard is determined based on the value within the lower limit value range of the normal product distribution and below the lower limit value. A standard value determination method characterized by determining value 2 .

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