JP2008235308A - Inspection method and apparatus of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inspect existence of a void precisely by nondestructive inspection. <P>SOLUTION: In an inspection method of a semiconductor device having electrodes, respectively, on both sides of a first conductivity type semiconductor layer in order to feed a current in the thickness direction of the semiconductor layer, and having an iteration PN structure formed by filling a trench formed on one side of the semiconductor layer with an epitaxially grown second conductivity type trench embedding layer opposite to the first conductivity type, an measuring instrument is connected between the electrodes of the semiconductor device having no void in the trench embedding layer to acquire the reverse recovery time of the semiconductor device previously as a reference reverse recovery time, an measuring instrument is connected between the electrodes of the inspection object semiconductor device to acquire the reverse recovery time of that semiconductor device, and a judgment is made that a void exists in the trench embedding layer of the inspection object semiconductor device if the reverse recovery time of the inspection object semiconductor device deviates more than a predetermined threshold from the reference reverse recovery time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection method of a semiconductor device and an inspection device using the inspection method, and more particularly to a method and an inspection device for inspecting a void of a semiconductor device having a repetitive PN structure called a super junction. .

  A semiconductor device called a superjunction has a repetitive structure of a P column and an N column arranged in parallel with the current path at the time of ON, as disclosed in, for example, Patent Document 1 and Patent Document 2. It is known that higher breakdown voltage can be obtained than the conventional structure.

A P column (or N column: the P column will be described as a trench burying layer hereinafter) that is a basic part for obtaining a high breakdown voltage is formed by burying a semiconductor material in the formed trench by an epitaxial growth method. However, if the semiconductor material is embedded with a void in the groove, the semiconductor device cannot obtain a desired performance.
JP 2006-294968 A JP 2003-069017 A

  Therefore, it has been required to grasp whether a void has occurred in the manufactured semiconductor device. Conventionally, an inspection method for grasping the presence or absence of voids has been performed by disassembling a semiconductor device. Therefore, there is a risk of disassembling even a semiconductor device in which no void is generated, and an improvement thereof has been demanded.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a method capable of accurately inspecting the presence or absence of voids by nondestructiveness.

  The present invention was devised to achieve the above object, and has electrodes on one surface and the other surface of the semiconductor layer, respectively, in order to pass a current in the thickness direction of the semiconductor layer of the first conductivity type. In a method for inspecting a semiconductor device having a PN structure repeatedly by embedding a second conductivity type groove buried layer opposite to the first conductivity type in a groove formed on one surface side of a semiconductor layer by epitaxial growth, A measuring instrument is connected between the electrodes of the semiconductor device having no void in the buried layer, and the reverse recovery time of the semiconductor device is acquired in advance as a reference reverse recovery time, and the measuring instrument is connected between the electrodes of the semiconductor device to be inspected. Connecting and acquiring the reverse recovery time of the semiconductor device, and when the reverse recovery time of the semiconductor device to be inspected and the reference reverse recovery time are different from each other by a predetermined threshold or more, It characterized in that it determined to have a void Kimizo buried layer.

  When the inspection method is for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device having no void in the groove buried layer, the threshold value is 15% or less.

  The first conductive type semiconductor layer has electrodes on one side and the other side of the semiconductor layer to allow current to flow in the thickness direction, and the first conductive type is formed in a groove formed on one side of the semiconductor layer. In an inspection apparatus for a semiconductor device having a PN structure repeatedly by burying a trench buried layer of the second conductivity type opposite to the mold by epitaxial growth, a measuring instrument is previously provided between the electrodes of the semiconductor device having no void in the trench buried layer And connecting a measuring device between the reference reverse recovery time acquisition unit for acquiring the reverse recovery time of the semiconductor device as the reference reverse recovery time and the electrode of the semiconductor device to be inspected, and calculating the reverse recovery time of the semiconductor device. When the reverse recovery time acquisition unit to acquire and the reverse recovery time of the semiconductor device to be inspected and the reference reverse recovery time are more than a predetermined threshold, if there is a void in the groove buried layer of the semiconductor device to be inspected A determination unit for disconnection, characterized in that it comprises a.

  In the case of an inspection apparatus for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device having no void in the groove buried layer, the threshold value is 15% or less.

  The reference reverse recovery time acquisition unit holds in the reference reverse recovery time storage unit when it is an inspection device for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device having no void in the groove buried layer. The measured reverse recovery time of the diode is compared with the measured reverse recovery time of the diode, and when the measured reverse recovery time of the diode is longer than the retained reference reverse recovery time, the measured reverse recovery time of the diode is newly set. An update determination unit that performs updating in the reference reverse recovery time storage unit in a plurality of semiconductor devices so as to be stored in the reference reverse recovery time storage unit as a correct reference reverse recovery time.

According to the present invention, the reverse recovery time of the semiconductor device having no void is measured and obtained in advance as the reference reverse recovery time, the reverse recovery time in the semiconductor device to be inspected is measured, and the measurement result and the reference reverse recovery time are When the obtained divergence value is equal to or greater than a predetermined threshold value, it is determined that the groove embedded layer of the semiconductor device to be inspected has a void. Thereby, according to this invention, the presence or absence of a void can be confirmed with high accuracy without disassembling the semiconductor device to be inspected.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same components are denoted by the same reference numerals in the drawings used in the embodiments, and overlapping descriptions are possible. Omitted as much as possible. In the following description, N type is used as the first conductivity type, and P type is used as the second conductivity type.

Prior to describing the method for inspecting a semiconductor device of the present invention, a semiconductor device to be inspected will be described first.
The semiconductor device is a diode, MOSFET, IGBT, power IC, or the like having a structure called a super junction. In the following description, a diode will be described as an example of a semiconductor device having a super junction structure.

  As shown in FIG. 2, the super junction structure diode 200 includes a cathode electrode 206, a cathode layer 205 for obtaining ohmic contact with the cathode electrode 206, a drift layer 204 provided on the cathode layer 205, The P pillar 203 as a groove buried layer in which a P type impurity is formed by an epitaxial growth method in a groove provided in the drift layer 204 at a predetermined spacing, and the P type impurity is doped on the surface of the drift layer between the P pillars. The surface layer 202 thus formed, and the anode electrode 201 provided on the surface of the surface layer 202 and the surface of the P column region are provided.

  In addition, the layer which consists of the cathode layer 205 and the drift layer 204 arrange | positioned on this cathode layer 205 in a present Example respond | corresponds to the semiconductor layer as described in a claim.

  Incidentally, the diode 200 may appropriately include a conventionally known configuration such as a guard ring or a surface protective film as a configuration for obtaining good performance. Since these configurations are not directly related to the gist of the present invention, the explanation is omitted.

Here, each configuration of the diode 200 will be described in detail.
The cathode layer 205 has a layer thickness of about 350 μm and contains N-type impurities at a concentration of about 2 × 10 ¹⁹ cm ⁻³ .
The drift layer 204 in which the P pillar 203 is formed has a layer thickness of about 26 μm, and includes N-type impurities at a concentration of about 1.8 × 10 ¹⁵ cm ⁻³ , depending on the concentration. , Having a lifetime of about 10 μs.

A groove having a groove width of about 2 μm and a groove depth of about 14 μm is formed in the drift layer 204 at intervals of 9 μm, and a P pillar 203 formed by embedding a P-type impurity in the groove by an epitaxial growth method is about It has a width dimension of 2 μm and a depth dimension of about 14 μm, and is formed to contain P-type impurities at a concentration of about 8.0 × 10 ¹⁵ cm ⁻³ . By the way, since the P pillars are formed in the N type drift layer 204 at predetermined intervals, an N type region divided by the formation of the P pillars 203 is formed as an N pillar on the surface of the drift layer 204. The N pillars and the P pillars 203 are formed alternately.

The surface layer 202 is provided to obtain a PN junction with the N-type drift layer 204, includes P-type impurities at a concentration of about 3.0 × 10 ¹⁷ cm ⁻³ , and has a layer thickness of about 2 μm. It is formed to have.

  By the way, the diode 200 having the super junction structure is provided with the P pillar 203 and the N pillar in the vertical stripe shape as described above, so that the depletion layer is formed from the interface between the P pillar 203 and the N pillar. Spread throughout. As a result, the internal electric field strength does not increase locally but becomes constant in the thickness direction, and the breakdown voltage can be improved.

  Further, since the diode 200 having a super junction structure can deplete the P pillar 203 and the N pillar at a low voltage, the impurity concentration of the N pillar can be increased, and the on-resistance can be reduced. .

  Next, a method for inspecting the presence or absence of voids in the P pillar 203 of the diode will be described with reference to the flowchart of FIG.

First, the reverse recovery time (trr) of the diode is acquired as the reference reverse recovery time (step S1).
Here, the reverse recovery time will be described. In general, when a forward current is passed through a diode and then the applied voltage is reversed, the diode can be regarded as a kind of capacitor that stores minority carriers, and until the stored charge amount (Qrr) is completely discharged. Time is the reverse recovery time.

The reverse recovery time is acquired by a method called IF / IR method or di / dt method.
In this embodiment, as shown in FIG. 3, a diode, a power source (VF power source) for supplying a forward bias (IF) to the diode, and a power source (VR) for supplying a reverse bias (IR) are provided. The reverse recovery time is obtained using a circuit composed of a power source), a switch for switching these power sources, and a CRO (Cathode Ray Oscilscope) connected to the cathode of the diode.

To obtain the reverse recovery time, first, a forward bias is supplied to the diode by the VF power source.
Thereafter, a reverse bias is supplied to the diode by the VR power supply by switching the switch. At this time, the amount of charge stored by applying the forward bias gradually decreases. Accordingly, as shown in FIG. 4, a period in which the current decreases from 0 point through the reverse recovery current peak value to 0.1 IR, for example, is measured by CRO, and this is acquired as the reverse recovery time.

  In this embodiment, the reverse recovery time is obtained by setting the current supplied in the forward bias to 0.5 A and the current supplied in the reverse bias to 1 A.

  Here, the reference reverse recovery time will be described again by returning to the description of Step 1. In the following description, however, it is based on a diode group composed of a plurality of diodes including at least a diode without a void (see the schematic diagram of FIG. 5). An example of acquiring the reference reverse recovery time will be described.

  The inventor obtained the reverse recovery time of each diode in the diode group of the schematic diagram shown in FIG. 5 by the above-described method, and created the graph shown in FIG. 6 based on the obtained result. In this graph, the reverse recovery time is shown on the horizontal axis and the number is shown on the vertical axis.

  In addition, the inventor has confirmed and inspected each diode of the diode group shown in the graph whether or not there is a void, including the size of the void. I found that there is no. That is, the inventor found that there is no void in the diode showing the longest reverse recovery time in the graph shown in FIG.

  As a result, the longest reverse recovery time is acquired as the reference reverse recovery time as a criterion for determining a diode without a void. In the graph shown in FIG. 6, 830 ns indicating the longest reverse recovery time is acquired as the reference reverse recovery time.

Next, the reverse recovery time of the diode to be inspected is acquired by the method described above (step S2).
Thereafter, a deviation value between the acquired reverse recovery time of the inspection target diode and the reference reverse recovery time is calculated (step S3).

Next, the deviation value is compared with a predetermined threshold value (step S4).
Here, the predetermined threshold will be described.
The threshold value indicates a predetermined ratio from the reference reverse recovery time. Specifically, the predetermined ratio is preferably 20 percent or less, and more preferably 15 percent or less.

  This specific numerical value is based on the graph shown in FIG. 6 which the inventor repeated and summarized the experiment. A diode without a void or a diode having a minute void that does not particularly adversely affect performance is shown in the graph. As is apparent from FIG. 4, it is particularly concentrated within a range indicated by a predetermined ratio from the reference reverse recovery time.

  When the threshold value is 15%, the longest reverse recovery time (reference reverse recovery time) in the graph shown in FIG. 6 is 830 ns, so 124.5 ns (hereinafter, referred to as 15% of the 830 ns). In the explanation of 125 ns rounded off to the nearest decimal point). That is, 125 ns is a deviation allowable value between the reverse recovery time of the diode to be inspected and the reference reverse recovery time, and the so-called threshold value is changed.

  By comparing the deviation value with the threshold value in step S4, when the deviation value is equal to or greater than the threshold value, that is, when the deviation value is equal to or greater than 125 ns, it is determined that the diode to be inspected has a void in the P column (step S5).

  On the other hand, when the divergence value does not deviate more than the threshold value according to the comparison result between the divergence value and the threshold value, that is, when the divergence value is less than 125 ns, the diode to be inspected has no void in the P column, or has an adverse effect on the diode performance It is determined that the P column has a minute void that does not affect the P column (step S6).

  As described above, according to the method for inspecting a semiconductor device of the present invention, when the reverse recovery time of the diode to be inspected deviates more than a threshold from the reference reverse recovery time acquired in advance, it is determined that there is a void. As a result, the semiconductor device inspection method of the present invention does not need to bother disassembling the diode to check for the presence of voids, and can prevent the inspection target diode from being wasted. The manufacturing cost can be reduced.

Next, an inspection apparatus that embodies the inspection method shown in the flowchart of FIG. 1 will be described.
As shown in FIG. 7, the inspection apparatus 10 using the semiconductor device inspection method of the present invention acquires a reference reverse recovery time as a reference reverse recovery time when the P pillar 203 has no void as a reference reverse recovery time 1. And the reference reverse recovery time storage unit 2 that holds the acquired reference reverse recovery time, the reverse recovery time acquisition unit 3 that acquires the reverse recovery time of the test-symmetric semiconductor device, and the reverse recovery time acquisition unit 3 The reverse recovery time is compared with the reference reverse recovery time held in the reference reverse recovery time storage unit 2, and the divergence value calculation unit 4 that acquires the divergence value, the threshold value storage unit 5 that holds a predetermined threshold, and the divergence value A determination unit 6 that compares the deviation value calculated by the calculation unit 4 with a threshold value stored in the threshold value storage unit 5 to determine the presence or absence of a void, and an output unit 7 that outputs a determination result are provided.

  The reference reverse recovery time acquisition unit 1 acquires the reverse recovery time of each diode in the diode group described above, and stores the longest reverse recovery time in the acquisition result in the reference reverse recovery time storage 2 as the reference reverse recovery time. In the present embodiment, the following description will be given with an example in which 830 ns is acquired as the reference reverse recovery time.

  The reference reverse recovery time storage unit 2 holds the reference reverse recovery time acquired by the reference reverse recovery time acquisition unit 1, and receives the instruction from the divergence value calculation unit 4 to store the reference reverse recovery time stored as the divergence value calculation unit. Output to 4. Even after the output, the reference reverse recovery time is continuously held in the reference reverse recovery time storage unit 2.

  The reverse recovery time acquisition unit 3 acquires the reverse recovery time of the diode to be inspected, and outputs the acquired reverse recovery time to the deviation value calculation unit 4.

  The deviation value calculation unit 4 calculates a deviation value between the reference reverse recovery time held in the reference reverse recovery time storage unit 2 and the reverse recovery time of the diode to be inspected acquired by the reverse recovery time acquisition unit 3.

  The threshold storage unit 5 performs a calculation based on a percentage indicating a predetermined ratio with respect to the reference reverse recovery time and the reference reverse recovery time held in the reference reverse recovery time storage unit 2, and holds the calculation result as a threshold. . For example, when the reference reverse recovery time is 830 ns and the predetermined ratio is 15%, the threshold value storage unit 5 holds 125 ns corresponding to 15% of 830 ns as a threshold value.

The determination unit 6 determines whether or not the divergence value deviates more than the threshold based on the divergence value calculated by the divergence value calculation unit 4 and the threshold value stored in the threshold value storage unit 5. Output to the output unit 7.
When the output unit 7 receives the determination result from the determination unit 6, the output unit 7 outputs the determination result.

  By the way, each structure of the above-mentioned inspection apparatus 10 is realizable by the specific structure shown in FIG. That is, the inspection apparatus 10 of the present invention includes a bus 101 for transmitting and receiving various data and information as electrical signals, a central processing unit (CPU) 102 connected via the bus 101, and the central processing unit. 102, a RAM 103 used as a work area, a ROM 104 for storing each configuration described above as a program, interfaces 105 and 106 connected to a bus, a CRT 107 connected via the interface 105, a keyboard and a mouse And an input device 108 and a Trr measuring device (CRO) 109 connected via the interface 106.

  The Trr measuring device 109 is a conventionally known measuring device such as a CRO and has a function of outputting the measured reverse recovery time as a signal. The signal output from the Trr measuring device is sent to the interface 106, and the interface 106 that has received the signal processes the signal into information that can be processed by the central processing unit 102, and the information is sent to the central processing unit 102. Output.

  The central processing unit 102 reads out a program stored in the ROM 104 based on a program counter (not shown), and performs arithmetic processing based on an instruction obtained by decoding the read program with a decoder (not shown). The RAM 103 is used as a work area for this arithmetic processing, and the RAM 103 temporarily stores information such as the result of the arithmetic processing and the reference reverse recovery time. Information with a low update (change) frequency such as the reference reverse recovery time may be held in the ROM 104 or a non-volatile memory (not shown).

  On the CRT 107, an input guidance screen for setting an inspection result and a threshold is displayed by control based on a program. Thereby, the inspector can input parameters for threshold setting using the input device in accordance with the input guidance screen. The input information is stored in the RAM 103 or a non-volatile memory (not shown).

  The program stored in the ROM 104 is for carrying the above-described components of FIG. For example, in the control based on the program for the reference reverse recovery time acquisition unit 1, acquisition of the reverse recovery time is instructed to the Trr measuring device 109 via the interface 106. After that, when the reverse recovery time of each diode of the diode group is acquired by the Trr measuring device 109 that has received the instruction, the longest reverse recovery time is set as the reference reverse recovery time based on these in the RAM 103 or a nonvolatile memory (not shown). Control to store is performed.

  Here again, the operation of the semiconductor device inspection apparatus 10 using the semiconductor device inspection method of the present invention shown in the flowchart of FIG. 1 will be described in detail with reference to FIGS.

  As described above, when the Trr measuring device 109 acquires the reverse recovery time of each diode of the diode group by the reference reverse recovery time acquisition unit 1, the inspection apparatus 10 of the present invention uses the longest reverse recovery time as the reference reverse recovery time as a reference. Store in reverse recovery time memory 2. In the present embodiment, 830 ns is stored as the reference reverse recovery time in the RAM 103, the ROM 104, or the non-illustrated nonvolatile memory as the reference reverse recovery time storage unit 2.

  On the other hand, the threshold value storage unit 5 holds a percentage indicating a predetermined ratio with respect to the reference reverse recovery time, and calculates based on the percentage and the reference reverse recovery time held in the reference reverse recovery time storage unit 2. And the calculation result is held as a threshold value.

  By the way, the threshold value storage unit 5 obtains a percentage (threshold value) indicating a predetermined ratio from an attendant. Specifically, the threshold value storage unit 5 displays a percentage input guidance screen on the CRT 107 by display control, and based on the input guidance screen, When the percentage is acquired from the input device 108 operated by the user, the calculation is performed based on the percentage and the reference reverse recovery time, and the calculation result is stored in the RAM 103 or a nonvolatile memory (not shown) as a new threshold value.

  When 15% is input by the attendant, 125 ns is calculated as the threshold based on the percentage and the reference reverse recovery time of 830 ns.

  Next, when the reverse recovery time acquisition unit 3 acquires the reverse recovery time of the diode to be inspected by the Trr measuring device 109, the inspection device 10 of the present invention outputs the acquired reverse recovery time to the deviation value calculation unit 4.

  The deviation value calculation unit 4 acquires the reverse recovery time of the diode to be inspected from the reverse recovery time acquisition unit 3 and reads the reference reverse recovery time held in the reference reverse recovery time storage unit 2. The divergence value calculation unit 4 calculates a divergence value between the reverse recovery time and the reference reverse recovery time of the diode to be inspected, and outputs the calculation result to the determination unit 6.

  For example, the divergence value calculation unit 4 that acquired 480 ns as the reverse recovery time of the diode to be inspected from the reverse recovery time acquisition unit 3 and acquired 830 ns held in the reverse recovery time acquisition unit 3 uses 350 ns as the divergence value. calculate. The divergence value calculation unit 4 appropriately uses the RAM 103 as a work area for calculating the divergence value in the above-described arithmetic processing.

  The determination unit 6 determines whether or not the divergence value is more than the threshold value based on the divergence value calculated by the divergence value calculation unit 4 and the threshold value stored in the threshold value storage unit 5. When the deviation is greater than or equal to the threshold value, it is determined that there is a void in the P pillar 203 and that fact is output to the output unit 7.

  That is, if the determination unit 6 determines that the deviation value is equal to or greater than the threshold value based on the 125 ns threshold value held by the deviation value calculation unit 4 and the 350 ns deviation value obtained by the deviation value calculation unit 4, The fact that the pillar 203 has a void is output to the output unit 7.

  On the other hand, when the divergence value does not deviate more than the threshold value, the determination unit 6 determines that there is no void and outputs that fact to the output unit 7.

  Upon receiving the determination result from the determination unit 6, the output unit 7 performs display control so that the determination result is displayed on the CRT 107. Thereby, the inspector can grasp the presence / absence of voids in the diode to be inspected based on the display content displayed on the CRT 107, and needs to check the presence / absence of voids by dismantling the inspected diode. There is no.

  In the above-described embodiment, the output of the determination result has been described as an example of displaying on the CRT 107. However, in addition to the CRT 107 as an output means, for example, a print output by a printer or a file that can be stored in a database is output. May be.

  Further, when the system is constructed so that the inspection apparatus 10 of the present invention is arranged on the inspection line, the presence or absence of voids in the diode to be inspected is displayed on the CRT 107 as described above to notify the inspector. Alternatively, the inspector may be notified by sounding from a speaker or lighting (flashing) by a lighting device. Furthermore, a diode having a void may be automatically sorted by a sorter.

<Example 2>
Next, a semiconductor having a function of acquiring the reverse recovery time of each diode in the diode group shown in FIG. 5 (see FIG. 5) and automatically setting the reference reverse recovery time based on the acquired multiple reverse recovery times A device inspection apparatus will be described.

  As shown in FIG. 9, the inspection apparatus 20 of the second embodiment includes a reference reverse recovery time storage unit 2, a reverse recovery time acquisition unit 3, a divergence value calculation unit 4, a threshold storage unit 5, and a determination unit similar to those of the first embodiment. 6 and the output unit 7, and further includes a reference reverse recovery time acquisition unit 21 that is a feature of the present embodiment.

  The description of the configuration similar to that of the first embodiment is omitted, and the reference reverse recovery time acquisition unit 21 that is a feature of the present embodiment will be described in detail.

  The diode group used in the description of the present embodiment is the same as that of the first embodiment, and the P pillar 203 includes a large number of diodes having no voids or minute voids. Is formed in the P pillar 203, and some diodes having such voids are included. As a result, the diode group basically consists of a large number of diodes that can exhibit the desired performance, but some diodes that do not exhibit the desired performance due to the formed voids are included.

  The reference reverse recovery time acquisition unit 21 that acquires the reference reverse recovery time from the diode group described above includes an update determination unit 22 as shown in FIG. 9, and the update determination unit 22 performs reverse recovery of each diode of the diode group. Based on the time, the reference reverse recovery time storage unit 2 stores the longest reverse recovery time as the reference reverse recovery time.

  That is, the update determination unit 22 compares the reference reverse recovery time temporarily stored in the reference reverse recovery time storage unit 2 with the measured reverse recovery time of the diode, and the measured reverse recovery time of the diode is temporarily stored. When the reference reverse recovery time is longer than the reference reverse recovery time, the reference reverse recovery time storage unit 2 is updated so that the measured reverse recovery time of the diode is temporarily stored in the reference reverse recovery time storage unit 2 as a new reference reverse recovery time.

Here, the operation of the reference reverse recovery time acquisition unit 21 will be described in detail along the flowchart of FIG.
First, in the diode group shown in FIG. 5, the reverse recovery time of the diode is acquired (step S11).

  Next, the reference reverse recovery time acquisition unit 21 compares the reverse recovery time acquired this time by the update determination unit 22 with the reference reverse recovery time temporarily held in the reference reverse recovery time storage unit 2 (step S12). When the reverse recovery time acquired this time is longer than the reference recovery time temporarily stored in the reference reverse recovery time storage unit 2, the acquired reverse recovery time is temporarily stored in the reference reverse recovery time storage unit 2 (step S13).

  The update determination unit 22 uses the reverse recovery time acquired first when the reference reverse recovery time to be compared is not temporarily stored in the reference reverse recovery time storage unit 2, that is, when the first update determination is performed. The reference reverse recovery time storage unit 2 temporarily holds the reference reverse recovery time.

  The reference reverse recovery time acquisition unit 21 repeats the process from step S11 described above until the update determination process described above is performed for all the diodes in the diode group (step S14).

  As a result, when the update determination for all the diodes in the diode group is completed, the longest reverse recovery time is temporarily stored in the reference reverse recovery time storage unit 2, and as a result, the reference reverse recovery time is stored as the reference reverse recovery time. Held in part 2.

  The reference reverse recovery time acquired as described above is used when determining the presence or absence of voids in each diode of the diode group used for acquiring the reference reverse recovery time, as in the first embodiment.

  Thereby, according to the inspection apparatus of the semiconductor device of Example 2, the reference reverse recovery time is automatically set based on the reverse recovery time of each diode of the diode group by the update determination unit 22 of the reference reverse recovery time acquisition unit 21. Can be acquired.

  If the reverse recovery time of each diode obtained at the time of acquiring the reference reverse recovery time is held, and each reverse recovery time and each diode are managed in association with each other, the reverse recovery time acquisition unit 3 Therefore, it is not necessary to re-acquire the reverse recovery time of each diode, and whether or not there is a void based on the reverse recovery time acquired and held in advance and the reference reverse recovery time held in the reference reverse recovery time storage unit 2 It is possible to select a diode managed in association with a reverse recovery time acquired in advance based on the determination result.

  In the above-described embodiments, the semiconductor device to be inspected is a super junction structure diode. However, the invention is not limited to this. For example, a semiconductor device such as a super junction structure MOSFET or a semiconductor device such as a super junction structure IGBT is used. Also, the presence or absence of voids can be inspected by the inspection method and inspection apparatus of the present invention.

  In the above embodiment, an example of the threshold value has been described. However, the present invention is not limited to this. For example, as a method of manufacturing a semiconductor device to be inspected, the growth rate of epitaxial growth, the size of the P pillar, and the inspection object The threshold value may be appropriately changed according to conditions such as the yield rate of the semiconductor device.

  In the above-described embodiment, the configuration in which the deviation value calculation unit 4 and the determination unit 6 are provided independently has been described. However, the present invention is not limited to this. For example, the configuration form is appropriately changed so that the determination unit 6 has various configurations. Such a configuration change is substantially the same as that of the inspection apparatus of the present invention, and is understood as one aspect of the inspection apparatus of the present invention.

  In the embodiment of the present invention, the reverse recovery time is used as an example. However, the reverse recovery time is the time until the reverse recovery charge amount (Qrr) is completely discharged by the reverse current (IR). It can be considered that time (Trr) = reverse recovery charge amount (Qrr) / reverse current (IR). Accordingly, the semiconductor device inspection method using the reverse recovery charge amount is naturally understood as an aspect of the semiconductor device inspection method based on the reverse recovery time of the present invention.

3 is a flowchart illustrating a semiconductor device inspection method according to the present invention. It is a figure which shows the structure of a diode as a semiconductor device of a super junction. It is a measurement circuit diagram used for acquisition of reverse recovery time (Trr). It is a figure which shows acquisition of reverse recovery time (Trr). The schematic diagram which shows the diode group which consists of a diode without a void and a diode which has a void of various sizes. It is a figure which shows the histogram in which the reverse recovery time and the number of each diode of a diode group were shown. It is a functional block diagram of the inspection apparatus of the semiconductor device of the present invention. It is the block diagram which embodied the function of the inspection apparatus of the semiconductor device of this invention. FIG. 10 is a functional block diagram of a semiconductor device inspection apparatus according to a second embodiment. 10 is a flowchart illustrating an operation of a reference reverse recovery time acquisition unit of the semiconductor device inspection apparatus according to the second embodiment.

Explanation of symbols

1 reference reverse recovery time acquisition unit 2 reference reverse recovery time storage unit 3 reverse recovery time acquisition unit 4 deviation value calculation unit 5 threshold storage unit 6 determination unit 7 output unit 10 inspection device 101 bus 102 central processing unit 103 RAM
104 ROM
105, 106 interface 107 CRT
108 Input Device 109 Trr Measuring Device 200 Semiconductor Device (Diode)
201 Anode electrode 202 Surface layer 203 P pillar 204 Drift layer 205 Cathode layer 206 Cathode electrode

Claims (5)

The first conductive type semiconductor layer has electrodes on one side and the other side of the semiconductor layer to allow current to flow in the thickness direction, and the first layer is formed in a groove formed on one side of the semiconductor layer. In a method of inspecting a semiconductor device having a PN structure repeatedly by embedding a trench buried layer of a second conductivity type opposite to the conductivity type by epitaxial growth,
Connecting a measuring instrument between the electrodes of the semiconductor device having no void in the groove buried layer, and obtaining in advance the reverse recovery time of the semiconductor device as a reference reverse recovery time;
Connecting a measuring instrument between the electrodes of the semiconductor device to be inspected to obtain a reverse recovery time of the semiconductor device;
A semiconductor device characterized in that when the reverse recovery time of the semiconductor device to be inspected and the reference reverse recovery time are different from each other by a predetermined threshold or more, it is determined that the groove buried layer of the semiconductor device to be inspected has a void. Device inspection method. When it is an inspection method for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device without a void in the groove buried layer,
2. The semiconductor device inspection method according to claim 1, wherein the threshold value is 15% or less. The first conductive type semiconductor layer has electrodes on one side and the other side of the semiconductor layer to allow current to flow in the thickness direction, and the first layer is formed in a groove formed on one side of the semiconductor layer. In an inspection apparatus for a semiconductor device having a PN structure repeatedly by embedding a trench buried layer of a second conductivity type opposite to the conductivity type by epitaxial growth,
A reference reverse recovery time acquisition unit that acquires a reverse recovery time of the semiconductor device as a reference reverse recovery time by connecting a measuring instrument between the electrodes of the semiconductor device without voids in the groove buried layer in advance,
A reverse recovery time acquisition unit that connects a measuring device between the electrodes of the semiconductor device to be inspected and acquires a reverse recovery time of the semiconductor device;
And a determination unit that determines that the groove buried layer of the semiconductor device to be inspected has a void when the reverse recovery time of the semiconductor device to be inspected and the reference reverse recovery time are different from each other by a predetermined threshold value or more. An inspection apparatus for a semiconductor device. When it is an inspection apparatus for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device having no void in the groove buried layer,
4. The semiconductor device inspection apparatus according to claim 3, wherein the threshold value is 15% or less. When it is an inspection apparatus for a plurality of semiconductor devices including a semiconductor device having a void in the groove buried layer and a semiconductor device having no void in the groove buried layer,
The reference reverse recovery time acquisition unit compares the reference reverse recovery time held in the reference reverse recovery time storage unit with the measured reverse recovery time of the diode, and the measured reverse recovery time of the diode is held. When the reference reverse recovery time is longer than the reference reverse recovery time, an update in the reference reverse recovery time storage unit is made to hold the measured reverse recovery time of the diode as a new reference reverse recovery time in the reference reverse recovery time storage unit. 4. The semiconductor device inspection apparatus according to claim 3, further comprising an update determination unit that is performed in step (1).

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