JP2021110688A - Device and method for diagnosing semiconductor device - Google Patents

Abstract

To provide a semiconductor device diagnosing device that acquires a cross point with less offset errors from stored data without calibrating individual difference of devices or detection circuits or displacement from a standard value.SOLUTION: A data storage unit 1 stores data [Vce, Ic] with an on-voltage Vce and an off-current Ic of a semiconductor device as a pair. A CP detection unit 2 performs cross point detection processing of detecting a cross point CP from the data [Vce, Ic] with the on-voltage Vce and the off-voltage Ic and data amount determination processing of determining whether a data amount needed to detect the cross point CP has been obtained.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for diagnosing a semiconductor element by utilizing the voltage-current-temperature characteristics of the semiconductor element.

The relationship between the on-voltage (collector-emitter voltage) Vce-on-current (collector current) Ic-device temperature Tj of a semiconductor element (for example, an IGBT) is used for device temperature estimation and life diagnosis. FIG. 8 shows an example of the relationship between the on-voltage Vce-on-current Ic-device temperature Tj of the IGBT. This relationship is given in data sheets and the like.

The relationship between the on-voltage Vce and the on-current Ic varies depending on the device temperature Tj, but at the cross point (CP) [Ic = Ic, cp, Vce = Vce, cp], it does not depend on the device temperature Tj. It is known that the on-voltage Vce fluctuates due to deterioration of the element, and patent documents 1 and 2 disclose a technique for diagnosing device deterioration by measuring the on-voltage Vce of a crosspoint CP that does not fluctuate with temperature. There is.

On the contrary, in the region depending on the device temperature Tj, the device temperature Tj can be estimated by measuring the on-voltage Vce and the on-current Ic. For example, in FIG. 9, the measured on-current and on-voltage [Ic, Vce] values are set to [Ic, k, Vce, k]. Further, on the curve of Tj = 25 ° C., the on-voltage at the on-current Ic, k is Vce25 (Ic, k), and on the curve of Tj = 125 ° C., the on-voltage at the on-current Ic, k is Vce125 (Ic, k,). k). The device temperature Tj at [Ic, k, Vce, k] can be obtained from Vce, k, Vce25 (Ic, k) and Vce125 (Ic, k) by the following equation (1).

In each technique, it is necessary to know in advance the relationship of Vce-Ic-Tj given in FIGS. 8 and 9 and the value of the cross point CP [Ic, cp, Vce, cp] obtained from the relationship.

JP-A-2010-220470 Japanese Unexamined Patent Publication No. 2014-236538 Japanese Unexamined Patent Publication No. 2014-2232062

As shown in FIG. 10, the cross point “CP individual” of the individual value actually possessed by the individual due to the individual difference of the device itself and the measurement circuit of the on-current Ic and the on-voltage Vce is the standard value “CP standard” of the cross point. It has an offset error "ΔVce, offset, ΔIc, offset" between and.

In Patent Document 1 and Patent Document 2, deterioration is determined by comparing the on-voltage Vce at a predetermined cross-point on-current Ic and cp with a threshold value. The voltage fluctuation due to deterioration is minute, but when standard values are used for the cross-point on-currents Ic and cp, the offset error may become unacceptable.

Individual differences do not matter when the current-voltage-temperature characteristics are investigated in advance for each device and measurement circuit in a constant temperature bath test to obtain a crosspoint CP, but the cost is high when conducting a test to measure the characteristics of all of them. It will be huge. The same applies to temperature estimation.

From the above, it is possible to obtain an accurate cross point from the accumulated data in the semiconductor device diagnostic device without calibrating the individual difference of the device and the detection circuit and the deviation from the standard value in advance. It becomes an issue.

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect thereof is a data storage unit for accumulating data in which an on-voltage and an on-current of a semiconductor element are combined, and the on-voltage and the on-current. It is provided with a CP detection unit that performs a crosspoint detection process for detecting a crosspoint from current data and a data amount determination process for determining whether or not the amount of data required for detecting the crosspoint is obtained. It is characterized by that.

Further, as one aspect thereof, the cross point detection process is characterized in that a set of a range of the on voltage and a range of the on current having the largest amount of data is set as a cross point.

As another aspect, in the cross-point detection process, a sample of the first on-voltage and a sample thereof at a certain current value in which the on-voltage depends on the temperature on a graph showing the relationship between the on-voltage and the on-current. The intersection of the curve fitted to the sample for the time continuous with the sample and the curve fitted with the sample with the second on-voltage different from the first on-voltage and the sample with the time continuous with the sample is defined as the cross point. It is a feature.

Further, as one aspect thereof, in the data amount determination process, the difference between the maximum value and the minimum value of the on-voltage at the on-current representative value whose on-voltage value depends on the temperature is used as a temperature variation reference, and the temperature variation is used. When the reference is larger than the threshold value, it is determined that the amount of data required for detecting the cross point is obtained.

Further, as another aspect, in the data amount determination process, the dispersion value of the on-voltage at the on-current representative value whose on-voltage value depends on the temperature is used as the temperature variation reference, and the temperature variation reference is more than the threshold value. When it is large, it is determined that the amount of data required for detecting the cross point is obtained.

Further, as one aspect thereof, a deterioration diagnosis unit for diagnosing deterioration of the semiconductor element is provided based on the difference between the initial value of the on-voltage of the cross point and the current value of the on-voltage of the cross point. It is characterized by that.

Further, as one aspect thereof, a temperature at which the standard value of the cross point and the offset error of the cross point detected by the CP detection unit are obtained, and the temperature of the semiconductor element is estimated based on the on-voltage after the offset error compensation. It is characterized by having an estimation unit.

According to the present invention, in a semiconductor device diagnostic apparatus, it is possible to obtain an accurate cross point from accumulated data without calibrating in advance individual differences of devices and detection circuits and deviations from standard values. It becomes.

The block diagram which shows the semiconductor element diagnostic apparatus in Embodiments 1 and 2. The figure which shows the example of the data [Vce, Ic] accumulated in the data storage part. The flowchart which shows the processing of the CP detection part in Embodiment 1. The figure which shows the 2D histogram of [Vce, Ic]. The figure which shows the operation of the deterioration diagnosis part. The flowchart which shows the processing of the CP detection part in Embodiment 2. The figure which shows the process of S6 of FIG. The figure which shows the relationship of Vce-Ic-Tj. The figure explaining the relationship of Vce-Ic-Tj and the estimation of a device temperature. The figure which shows the relationship of Vce-Ic-Tj of a standard value and a solid value.

Hereinafter, embodiments 1 and 2 of the semiconductor device diagnostic apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 7, 9 and 10.

[Embodiment 1]
FIG. 1 shows the semiconductor device diagnostic apparatus according to the first embodiment. The semiconductor device diagnostic device of the first embodiment includes a data storage unit 1, a CP detection unit 2, a deterioration diagnosis unit 3, and a temperature estimation unit 4. In the present specification, the diagnosis of a semiconductor element includes crosspoint detection, deterioration diagnosis, and temperature estimation.

The data [Vce, Ic], which is a set of the measured on-voltage Vce and on-current Ic, is stored in the data storage unit 1. The CP detection unit 2 detects the cross-point CP possessed by the individual using the accumulated N-point data [Vce, Ic]. The deterioration diagnosis unit 3 diagnoses the deterioration of the device (semiconductor element) using the cross-point CP detected by the CP detection unit 2 and the data [Vce, Ic] of the current on-voltage Vce and on-current Ic. The temperature estimation unit 4 estimates the temperature Tj of the device using the cross-point CP detected by the CP detection unit 2 and the data [Vce, Ic] of the current on-voltage Vce and on-current Ic.

FIG. 2 shows an example of the data [Vce, Ic] stored in the data storage unit 1. Since the crosspoint CP does not depend on temperature, there is little variation in data. The representative values of the currents whose Vce-Ic relationship depends on the temperature are the on-current representative values Ic and tpp. The data of the on-voltage Vce near the on-current representative values Ic and tpm vary due to temperature changes.

FIG. 3 shows a flowchart of the CP detection unit 2. The CP detection unit 2 estimates the crosspoint CP using a two-dimensional histogram of the data [Vce, Ic]. In S1 and S2 of FIG. 3, the crosspoint detection process for detecting the crosspoint CP from the data [Vce, Ic] of the on-voltage Vce and the on-current Ic is performed, and in S3 to S5, the amount of data required for detecting the crosspoint CP is Performs data amount determination processing to determine whether or not it has been obtained.

First, in S1, a sample of new data [Vce, Ic] is added. In S2, the frequency of the bin of the two-dimensional histogram corresponding to the added data [Vce, Ic] is added by 1. The CP detection unit 2 holds the bin having the maximum frequency and the maximum value thereof. If the frequency of the bin with the frequency added by 1 exceeds the current maximum value, the bin with the maximum frequency and the maximum value are updated.

When a two-dimensional histogram is created from data with temperature fluctuations, the frequency of bins with crosspoint CP is relatively high because the crosspoint CP does not depend on temperature. Therefore, the crosspoint CP can be detected by selecting the bin (range) of the data [Vce, Ic] having the largest amount of data. FIG. 4 shows an example of a two-dimensional histogram of the on-voltage Vce and the on-current Ic.

In S3, it is determined whether or not the on-current Ic of the added data is the on-current representative values Ic and tmp. If the on-current Ic is not the on-current representative value Ic or tmp, the process returns to S1. If the on-current Ic is the on-current representative value Ic, tmp, the process proceeds to S4.

In S4, the temperature variation reference Vce and tpvar are updated by the on-voltage Vce when Ic = Ic and tpp. The temperature variation reference Vce and tpvar are values indicating how much the on-voltage Vce at the same on-current representative values Ic and tpm varies. For example, the temperature variation reference Vce and tpvar are the differences between the maximum value and the minimum value of the on-voltage Vce at the on-current representative values Ic and tpp. Alternatively, the temperature variation reference Vce and tpvar may be the dispersion value of the on-voltage Vce at the on-current representative values Ic and tpp.

In S5, it is determined whether or not the temperature variation reference Vce and tpvar are larger than the threshold value. When the temperature variation criteria Vce and tpvar are larger than the threshold value, it is judged that data with sufficient temperature fluctuation is obtained to estimate the crosspoint CP, and the data of the bin with the maximum frequency at that time [Vce, Ic] ] Is set as the estimated value of the crosspoint CP [Vce, cp, Ic, cp], and the process is terminated. If the temperature variation reference Vce and tpvar are equal to or less than the threshold value, the process returns to S1.

The operation of the deterioration diagnosis unit 3 is shown in FIG. The difference between the initial value Vce, cp (0) of the on-voltage of the cross point estimated first after starting the device and the current value Vce, cp (k) of the on-voltage of the currently estimated cross point is ΔVce, Let cp (k) be used, and compare this with the deterioration indexes ΔVce, cp, and threshold. When the difference ΔVce, cp (k) becomes larger than the deterioration index ΔVce, cp, threshold, it is determined as a failure. It is also possible to know the current degree of deterioration and the remaining life from the ratio of the current difference ΔVce, cp (k) and the deterioration index ΔVce, cp, threshold.

In the temperature estimation unit 4, first, the cross point (standard value) CP obtained from the intersection of the Vce 25 curve and the Vce 125 curve in FIGS. 9 and 10 and the cross point CP obtained by the CP detection unit (cross point detection process) 2 Find the offset error [ΔVce, cp, ΔIc, cp].

The temperature is estimated after compensating for the offset error of the on-voltage in Eq. (1). Specifically, the term of Vce25 (Ic, k) in Eq. (1) is (Vce25 (Ic + ΔIc, cp) + ΔVce, cp), and the term of Vce125 (Ic, k) is (Vce125 (Ic + ΔIc, cp) + ΔVce, cp). And.

As shown above, according to the first embodiment, there is little offset error from the accumulated data without calibrating the individual differences of the device (semiconductor element) and the detection circuit and the deviation from the standard value in advance. Cross-point CP can be obtained.

In the deterioration diagnosis, by comparing the detected change amount of the crosspoint CP with the threshold value, it is not affected by the offset error due to the individual difference of the crosspoint CP. Further, by comparing the threshold value and the ratio of the amount of change, the current degree of deterioration before the failure can be known.

In the temperature estimation, the temperature can be estimated more accurately by compensating for the offset error from the standard value of the relationship of Vce-Ic-Tj.

[Embodiment 2]
The second embodiment differs only from the first embodiment and the CP detection unit 2. FIG. 6 shows a flowchart of the CP detection unit 2 in the second embodiment. In the second embodiment, the data amount determination process for determining whether or not the amount of data required for detecting the cross point CP is obtained in S3 to S5 is performed, and the cross is performed from the data of the on-voltage Vce and the on-current Ic in S6. Performs cross-point detection processing to detect point CP.

First, in S1, a sample of new data [Ic, Vce] is added. Next, in S3, it is determined whether or not the on-current Ic of the added data is the on-current representative values Ic and tmp. If the on-current Ic is not the on-current representative value Ic or tmp, the process returns to S1. If the on-current Ic is the on-current representative value Ic, tmp, the process proceeds to S4.

In S4, the temperature variation reference Vce and tmpvar are updated according to the on-voltage when Ic = Ic and tmp. The temperature variation reference Vce and tpvar are the same as those in the first embodiment.

S5 determines whether or not the temperature variation reference Vce and tpvar are larger than the threshold value. When the temperature variation criteria Vce and tpvar are larger than the threshold value, it is determined that data with sufficient temperature fluctuation is obtained to estimate the crosspoint CP. If the temperature variation reference Vce and tpvar are equal to or less than the threshold value, the process returns to S1.

When the temperature variation reference Vce and tpvar exceed the threshold value, the process proceeds to S6. The process of S6 is shown in FIG.

As shown in FIG. 7, first, on a graph showing the relationship between the on-voltage Vce and the on-current Ic, a sample of the maximum on-voltage (first on-voltage) Vce at a current value where Ic = Ic, tpp and its A continuous Nh sample is extracted from the sample. The extracted sample is a sample represented by "x" on the right side of FIG. 7. These are samples with similar temperatures because the time is continuous. Find the curve that fits the extracted sample (dotted line on the right in FIG. 7).

Next, on the graph showing the relationship between the on-voltage Vce and the on-current Ic, at the current value where Ic = Ic, tmp, the sample of the minimum on-voltage (second on-voltage) Vce and the Nh sample continuous from the sample. Is extracted. The extracted sample is a sample represented by "+" on the right side of FIG. These are samples with similar temperatures because the time is continuous. Find the curve that fits the extracted sample (broken line on the right in FIG. 7).

Finally, the intersection of the two curves is found and used as the crosspoint CP. Since the temperature of the sample represented by "x" and the sample represented by "+" are different, the intersection of the curves is a point independent of temperature, that is, a cross point CP.

As shown above, the second embodiment has the same effect as that of the first embodiment. In FIG. 7, in the current values where Ic = Ic, tmp, the maximum on-voltage Vce is set to the first on-voltage and the minimum on-voltage Vce is set to the second on-voltage, but the first on-voltage and the second on-voltage are used. Other on-voltage Vce may be used as long as the voltages have different values.

Further, Ic and tpp in FIG. 7 are current values at which the on-voltage Vce depends on the temperature, and are the same values as the on-current representative values for obtaining the temperature variation reference Vce and tpvar shown in FIGS. 2, 3 and 6. But it may be a different value.

Although the above description has been made in detail only with respect to the specific examples described in the present invention, it is clear to those skilled in the art that various modifications and modifications can be made within the scope of the technical idea of the present invention. It goes without saying that such modifications and modifications fall within the scope of the claims.

1 ... Data storage unit 2 ... CP detection unit 3 ... Deterioration diagnosis unit 4 ... Temperature estimation unit Vce ... On voltage Ic ... On current Tj ... Device temperature CP ... Cross point

Claims (8)

A data storage unit that stores data that combines the on-voltage and on-current of a semiconductor element,
A CP that performs a crosspoint detection process that detects a crosspoint from the data of the on-voltage and the on-current, and a data amount determination process that determines whether or not the amount of data required for detecting the crosspoint is obtained. With the detector
A semiconductor device diagnostic device characterized by being equipped with. The cross point detection process
The semiconductor device diagnostic apparatus according to claim 1, wherein a set of a range of the on-voltage and a range of the on-current having the largest amount of data is used as a cross point. The cross point detection process
On a graph showing the relationship between the on-voltage and the on-current, a curve fitted to a sample of the first on-voltage and a sample of a time continuous with the sample at a certain current value in which the on-voltage depends on temperature, and a curve. The semiconductor element diagnostic apparatus according to claim 1, wherein a cross point is an intersection of a sample having a second on-voltage different from the first on-voltage and a curve fitted to the sample for a time continuous with the sample. In the data amount determination process, when the difference between the maximum value and the minimum value of the on-voltage at the on-current representative value whose on-voltage value depends on the temperature is used as the temperature variation reference, and the temperature variation reference is larger than the threshold value. The semiconductor device diagnostic apparatus according to any one of claims 1 to 3, wherein it is determined that the amount of data required for detecting the cross point has been obtained. In the data amount determination process, the dispersion value of the on-voltage at the on-current representative value whose on-voltage value depends on the temperature is used as the temperature variation reference, and when the temperature variation reference is larger than the threshold value, the cross point The semiconductor device diagnostic apparatus according to any one of claims 1 to 3, wherein it is determined that an amount of data required for detection has been obtained. A claim comprising a deterioration diagnosis unit for diagnosing deterioration of a semiconductor element based on a difference between an initial value of the on-voltage of the cross point and a current value of the on-voltage of the cross point. Item 6. The semiconductor device diagnostic apparatus according to any one of Items 1 to 5. It is provided with a temperature estimation unit that obtains the standard value of the cross point and the offset error of the cross point detected by the CP detection unit and estimates the temperature of the semiconductor element based on the on-voltage after compensation for the offset error. The semiconductor device diagnostic apparatus according to any one of claims 1 to 6. The data storage unit stores data that combines the on-voltage and on-current of the semiconductor element.
A crosspoint detection process in which the CP detection unit detects a crosspoint from the on-voltage and on-current data, and a data amount determination process for determining whether or not the amount of data required for detecting the crosspoint is obtained. When,
A semiconductor device diagnostic method characterized by performing the above.

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