Method of measuring semiconductor device by applying voltage to the semiconductor device using probe needle

The present application relates to a technique of reducing the occurrence of a spot breakdown near a probe needle with the intention of preventing damage on the probe needle during a test implemented by applying a high voltage to a semiconductor device. In a method of measuring a semiconductor device, the semiconductor device includes: a semiconductor substrate (1), an epitaxial layer (2), at least one second conductivity type region (3) of a second conductivity type formed in a part of the surface layer of the epitaxial layer to have a contour, a Schottky electrode (11), an anode electrode (12), and a cathode electrode (13). A voltage is applied while the probe needle (21) is brought into contact with the upper surface of the anode electrode in a range in which the contour of the at least one second conductivity type region is formed in a plan view.

TECHNICAL FIELD

A technique disclosed in the description of the present application relates to a method of measuring a semiconductor device.

BACKGROUND ART

As described in patent document 1 (Japanese Patent Application Laid-Open No. 2014-229651, for example), if a test is implemented by applying a high voltage to a Schottky barrier diode (specifically, an SBD) using silicon carbide (SiC) or a junction barrier controlled Schottky diode (JBS) using silicon carbide (SiC), a spot breakdown may be caused by a crystal defect in SiC.

In a conventional semiconductor chip, a region in which a current is to flow has a uniform configuration. In such a semiconductor chip, the foregoing spot breakdown may occur, particularly near a probe needle for measurement.

If the spot breakdown occurs near the probe needle for measurement, the probe needle is damaged caused during the breakdown. This has necessitated interruption of the test and exchange of the probe needle.

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY

Problem to be Solved by the Invention

As described above, in the conventional SiC-SBD or SiC-JBS, the test implemented by applying a high voltage may cause a spot breakdown due to a crystal defect in SiC.

This spot breakdown is caused by thermal breakdown occurring in response to positive feedback in which a high leakage current is generated and starts to flow from the crystal defect to generate heat, and the generated heat increases the leakage current.

If this thermal breakdown occurs near the probe needle, the probe needle is damaged by adherence of an electrode melted and sputtered to the probe needle, or deformation of the probe needle itself by the heat.

If measurement continues while such damage remains unsolved, measurement failure may be caused by assembly failure due to an increased mark of contact with an electrode or malfunction due to damage on a surface of a semiconductor device at a lower part of the electrode, for example.

Hence, the occurrence of the spot breakdown near the probe needle has necessitated interruption of the test and exchange of the probe needle. In particular, if the test is implemented on a semiconductor device using a semiconductor material involving a large number of crystal defects in the semiconductor device such as silicon carbide (SiC), for example, the occurrences of a large number of spot breakdowns necessitates interruption of the test and exchange of the probe needle more frequently. This causes the problem of reducing processing capacity.

The technique disclosed in the description of the present application has been made to solve the foregoing problem, and relates to a technique of reducing the occurrence of a spot breakdown near a probe needle with the intention of preventing damage on the probe needle during a test implemented by applying a high voltage to a semiconductor device.

Means to Solve the Problem

A first aspect of the technique disclosed in the description of the present application is intended for a method of measuring a semiconductor device implemented by applying a voltage to the semiconductor device using a probe needle. The semiconductor device includes: a semiconductor substrate of a first conductivity type; an epitaxial layer of the first conductivity type formed on the upper surface of the semiconductor substrate; at least one second conductivity type region of a second conductivity type formed in a part of the surface layer of the epitaxial layer to have a contour; a Schottky electrode formed to cover the upper surface of the epitaxial layer and the upper surface of the second conductivity type region; an anode electrode formed on the upper surface of the Schottky electrode; and a cathode electrode formed on the lower surface of the semiconductor substrate. A voltage is applied while the probe needle is brought into contact with the upper surface of the anode electrode in a range in which the contour of the at least one second conductivity type region is formed in a plan view.

A second aspect of the technique disclosed in the description of the present application is intended for a method of measuring a semiconductor device implemented by applying a voltage to the semiconductor device using a probe needle. The semiconductor device includes: a semiconductor substrate of a first conductivity type; an epitaxial layer of the first conductivity type formed on the upper surface of the semiconductor substrate; at least one first Schottky electrode formed on the upper surface of the epitaxial layer; at least one second Schottky electrode formed on the upper surface of the epitaxial layer and forming a Schottky barrier between the second Schottky electrode and the epitaxial layer higher than a Schottky barrier formed between the first Schottky electrode and the epitaxial layer; an anode electrode formed on the upper surface of the first Schottky electrode and the upper surface of the second Schottky electrode; and a cathode electrode formed on the lower surface of the semiconductor substrate. A voltage is applied while the probe needle is brought into contact with the upper surface of the anode electrode in a range in which the at least one second Schottky electrode is formed in a plan view.

Effects of the Invention

The first aspect of the technique disclosed in the description of the present application is intended for the method of measuring a semiconductor device implemented by applying a voltage to the semiconductor device using the probe needle. The semiconductor device includes: the semiconductor substrate of the first conductivity type; the epitaxial layer of the first conductivity type formed on the upper surface of the semiconductor substrate; the at least one second conductivity type region of the second conductivity type formed in a part of the surface layer of the epitaxial layer to have a contour; the Schottky electrode formed to cover the upper surface of the epitaxial layer and the upper surface of the second conductivity type region; the anode electrode formed on the upper surface of the Schottky electrode; and the cathode electrode formed on the lower surface of the semiconductor substrate. A voltage is applied while the probe needle is brought into contact with the upper surface of the anode electrode in a range in which the contour of the at least one second conductivity type region is formed in a plan view. This configuration makes it possible to reduce the occurrence of a spot breakdown near the probe needle.

The second aspect of the technique disclosed in the description of the present application is intended for the method of measuring a semiconductor device implemented by applying a voltage to the semiconductor device using the probe needle. The semiconductor device includes: the semiconductor substrate of the first conductivity type; the epitaxial layer of the first conductivity type formed on the upper surface of the semiconductor substrate; the at least one first Schottky electrode formed on the upper surface of the epitaxial layer; the at least one second Schottky electrode formed on the upper surface of the epitaxial layer and forming a Schottky barrier between the second Schottky electrode and the epitaxial layer higher than a Schottky barrier formed between the first Schottky electrode and the epitaxial layer; the anode electrode formed on the upper surface of the first Schottky electrode and the upper surface of the second Schottky electrode; and the cathode electrode formed on the lower surface of the semiconductor substrate. A voltage is applied while the probe needle is brought into contact with the upper surface of the anode electrode in a range in which the at least one second Schottky electrode is formed in a plan view. This configuration makes it possible to reduce the occurrence of a spot breakdown near the probe needle.

These and other objects, features, aspects and advantages of the technique disclosed in the description of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF EMBODIMENT(S)

An embodiment will be described below by referring to the accompanying drawings.

The drawings are presented schematically. For the convenience of description, a structure is omitted or simplified, where appropriate. Correlations in terms of size and position between structures, etc. shown in different drawings are not always illustrated correctly but are changeable, where appropriate.

In the description given below, similar components will be given the same sign and illustrated with the same sign in the drawings. These components will be given the same name and are to fulfill the same function. Thus, to avoid duplication, detailed description of these components may be omitted.

In the description given below, a term meaning a particular position or a particular direction such as “upper,” “lower,” “side”, “bottom,” “front,” or “back” is used. These terms are used for the purpose of convenience to facilitate understanding of the substance of the embodiment, and do not relate to directions in actual use.

In the description given below, an ordinal number such as “first” or “second” may be used. These terms are used for the purpose of convenience to facilitate understanding of the substance of the embodiment, and are not intended to limit order that might be defined by these terms.

First Embodiment

A method of measuring a semiconductor device relating to a first embodiment will be described below. For the convenience of description, a spot breakdown and a mechanism of causing the spot breakdown will be described first.

In the description given below, a first conductivity type corresponds to an n type, and a second conductivity type corresponds to a p type.

FIG. 28is a sectional view illustrating the semiconductor device on the occurrence of a spot breakdown.FIG. 29is a plan view of the configuration illustrated inFIG. 28.FIG. 30illustrates the occurrence of a spot breakdown22.

As illustrated inFIG. 28, the semiconductor device relating to this embodiment includes an n+type silicon carbide semiconductor substrate1, an n−type epitaxial layer2formed on the upper surface of the n+type silicon carbide semiconductor substrate1, a Schottky electrode11formed on the upper surface of the epitaxial layer2, and an anode electrode12formed on the upper surface of the Schottky electrode11.

The semiconductor device relating to this embodiment includes a p-type terminal breakdown voltage holding layer91formed in the surface layer of the epitaxial layer2to surround the Schottky electrode11in a plan view. The terminal breakdown voltage holding layer91is joined in a partial region to the Schottky electrode11.

The semiconductor device relating to this embodiment includes a terminal protective film92formed to cover the Schottky electrode11and the anode electrode12, and a cathode electrode13formed on the lower surface of the silicon carbide semiconductor substrate1.

The anode electrode12of the semiconductor device relating to this embodiment has an upper surface to be contacted by a plurality of probe needles21.

A crystal defect23occurring in the semiconductor device having the foregoing configuration may cause the spot breakdown22near the probe needle21.

If the spot breakdown22occurs near the probe needle21for measurement, the probe needle21is damaged by the breakdown. This has necessitated interruption of a test and exchange of the probe needle.

A mechanism of causing a spot breakdown will be described next.

FIGS. 31, 32, and 33are sectional views for showing the mechanism of causing the spot breakdown.

As illustrated inFIG. 31, it is assumed that the crystal defect23occurs in the semiconductor device. A test is implemented on this semiconductor device by applying a high voltage.

More specifically, as illustrated inFIG. 32, the plurality of probe needles21contacts the upper surface of the anode electrode12of the semiconductor device. Then, a high voltage is applied through the probe needles21.

Then, as illustrated inFIG. 32, a high leakage current24is generated and starts to flow from the crystal defect23. The sizes of arrows indicating the leakage current24mean the approximate quantities of the leakage current.

As illustrated inFIG. 33, heat is generated at a position at which the high leakage current is generated. On the occurrence of positive feedback in which a leakage current is further generated at this position, thermal breakdown, specifically, the spot breakdown22is caused.

FIG. 1is a sectional view schematically illustrating the configuration in part of the semiconductor device, more specifically, a Schottky barrier diode (SBD) relating to this embodiment.FIG. 2is a plan view schematically illustrating the configuration in part of the semiconductor device relating to this embodiment.FIG. 1corresponds to a sectional view taken along AB inFIG. 2.

FIG. 3is a sectional view schematically illustrating the configuration in its entirety of the semiconductor device relating to this embodiment. A region X surrounded by dotted lines, specifically, an effective region inFIG. 3corresponds to a range of the partial configuration illustrated inFIG. 1.

In terms of facilitating understanding of the configuration, some components may be omitted or simplified in the illustrations ofFIGS. 1, 2, and 3.

The semiconductor device relating to this embodiment includes the n+type silicon carbide semiconductor substrate1, the n−type epitaxial layer2formed on the upper surface of the n+type silicon carbide semiconductor substrate1, the Schottky electrode11formed on the upper surface of the epitaxial layer2, and the anode electrode12formed on the upper surface of the Schottky electrode11. The Schottky electrode11is made of Ti, for example. In the below, the semiconductor device is described as a silicon carbide semiconductor device. However, the semiconductor device is not limited to a silicon carbide semiconductor device.

The semiconductor device relating to this embodiment includes a p-type semiconductor layer, specifically, an anode p-type region3formed in a part of the interior of the epitaxial layer2including a surface, specifically, in a part of the surface layer of the epitaxial layer2and joined in its entirety to the Schottky electrode11. The anode p-type region3is a p-type region in its entirety within a contour in a plan view.

The Schottky electrode11is formed to cover the upper surface of the epitaxial layer2and the upper surface of the anode p-type region3.

The anode p-type region3is formed in a layer below the anode electrode12. Meanwhile, for the convenience of description, the anode p-type region3is illustrated in a perspective fashion inFIG. 2.

The configuration of the semiconductor device in its entirety relating to this embodiment illustrated inFIG. 3includes the p-type terminal breakdown voltage holding layer91formed in the surface layer of the epitaxial layer2to surround the anode p-type region3in a plan view. The terminal breakdown voltage holding layer91is joined in a partial region to the Schottky electrode11.

The configuration of the semiconductor device in its entirety relating to this embodiment illustrated inFIG. 3includes the terminal protective film92formed to cover the Schottky electrode11and the anode electrode12, and the cathode electrode13formed on the lower surface of the silicon carbide semiconductor substrate1.

In the semiconductor device relating to this embodiment illustrated inFIG. 3, the anode electrode12has an upper surface to be contacted by the plurality of probe needles21.

As illustrated inFIG. 3, each of the probe needles21is to contact a position overlapping a region in which the anode p-type region3is located in a plan view.

The anode p-type region3includes at least one anode p-type region3formed in a part of a Schottky junction area, specifically, on a part of the lower surface of the Schottky electrode11. If there is a plurality of anode p-type regions3, a distance between adjacent ones of the anode p-type regions3is greater than twice the width of a depletion layer to extend from the anode p-type regions3in response to application of a rated voltage in a direction opposite a forward direction.

FIGS. 4, 5, and 6are sectional views for showing an arrangement interval between the anode p-type regions3.FIGS. 4, 5, and 6illustrate a depletion layer4generated by application of a rated voltage in a direction opposite a forward direction.

As illustrated inFIG. 4, a distance Y between adjacent ones of the anode p-type regions3is greater than twice a width W1of the depletion layer4to extend from the anode p-type regions3in response to application of a rated voltage in a direction opposite a forward direction.

A distance between the anode p-type region3and the terminal breakdown voltage holding layer91is also greater than twice the width W1of the depletion layer4to extend from the anode p-type region3in response to application of a rated voltage in a direction opposite a forward direction.

By doing so, like in a configuration inFIG. 5without a p-type region, a region Z in which the depletion layer4has a width W2is formed, as illustrated inFIG. 4.

More specifically, assuming that a rated voltage is V, an epitaxial concentration is Nd, the width of the depletion layer4is W, a distance between adjacent ones of the anode p-type regions3is d, the permittivity of semiconductor is ε, and elementary charge is q, the following relationship is established:

If a short distance is set between adjacent ones of the anode p-type regions3like in a conventional JBS, specifically, in a configuration illustrated inFIG. 6, ON resistance is increased by increase in JFET resistance.

The reason for this is that, in response to application of a rated voltage in a direction opposite a forward direction, the depletion layer4extending in a direction in the plane of a semiconductor wafer from the anode p-type region3exerts influence also on the width of the depletion layer4in a region in which the anode p-type region3is not formed.

Specifically, the depletion layer4extending in the direction in the plane of the semiconductor wafer from a region in the presence of the anode p-type region3reaches the region in which the anode p-type region3is not formed. This unfortunately makes a width W3of the depletion layer4in the region in which the anode p-type region3is not formed larger than the width W2of the depletion layer4shown inFIG. 5.

As described above, a spot breakdown is caused by thermal breakdown due to a leakage current. Hence, the occurrence of a spot breakdown can be reduced in a configuration achieving reduction in a crystal defect as a starting point of a leakage current and a leakage current to flow near the crystal defect.

Regarding a silicon carbide semiconductor, if an electrode having a low Schottky barrier practical for a Schottky barrier diode is used, for example, if an electrode made of Ti and having a barrier height of about 0.95 eV is used, a leakage current becomes lower at a pn junction at which a barrier height is about 2.5 eV than at a Schottky junction as a result of a difference in a barrier height between the junctions and a difference in a mechanism of generating a leakage current between the junctions.

Thus, as illustrated inFIG. 1, in the presence of the anode p-type region3introduced into a Schottky junction area in the n-type Schottky barrier diode, a leakage current becomes lower at a pn junction formed by the anode p-type region3than at the Schottky junction area. As a result, the occurrence of a spot breakdown is reduced in the anode p-type region3.

<Operation of Testing Semiconductor Device>

Described next is a test implemented by applying a high voltage to the semiconductor device relating to this embodiment using a probe needle. The test implemented by applying a high voltage mentioned herein means a test implemented by applying a voltage of 50 V or more in an opposite direction, for example.

As illustrated inFIGS. 7 and 8, for making measurement by applying the high voltage to the semiconductor device, the probe needle21is brought into contact with a range in which the anode p-type region3exists directly below the anode electrode12. Specifically, the probe needle21is brought into contact with the upper surface of the anode electrode12in the range in which the contour of the anode p-type region3is formed in a plan view. As a result, a spot breakdown becomes unlikely to occur near the probe needle21.

FIG. 7is a sectional view schematically illustrating the configuration of the semiconductor device relating to this embodiment.FIG. 8is a plan view schematically illustrating the configuration of the semiconductor device relating to this embodiment.FIG. 7corresponds to a sectional view taken along AB inFIG. 8.

Thus, it becomes possible to suppress damage caused by a spot breakdown on the probe needle21. As a result, necessity to interrupt the test and exchange the probe needle21can be eliminated.

The size of the anode p-type region3is desirably larger than the size of the probe needle21in a cross section. As illustrated inFIG. 9showing a relationship between the size of the anode p-type region3and the size of the probe needle21in a cross section, if the size of a range in which the spot breakdown22is to occur is 100 μm in diameter, the size of a region in which the probe needle21and the anode electrode12contact each other is 200 μm in diameter, and the probe needle21has accuracy of position of 50 μm, for example, the size of the anode p-type region3may be 400 μm or more.

An ON voltage is higher at the anode p-type region3than at the Schottky junction area. Hence, flowing a current in a forward direction increases the ON resistance of the Schottky barrier diode.

Thus, the anode p-type region3is desirably small in size. Desirably, the anode p-type region3has a minimum required size allowing protection of the probe needle21.

During measurement, the probe needle21is not required to contact a region entirely in which the anode p-type region3is located below the electrode but may contact a part of the region in which the anode p-type region3is located. Meanwhile, the anode p-type region3increases the ON resistance of the Schottky barrier diode as described above, so that the number of the anode p-type regions3is desirably small. Desirably, the number of the p-type regions3is a minimum required number allowing protection of the probe needle21.

FIGS. 10 and 11are sectional views for showing an arrangement interval between the anode p-type regions3.FIGS. 10 and 11illustrate the depletion layer4generated by application of a rated voltage in a direction opposite a forward direction.

As illustrated inFIG. 10, in the configuration of the semiconductor device relating to this embodiment, the distance Y between adjacent ones of the anode p-type regions3, and the distance Y between the anode p-type region3and the terminal breakdown voltage holding layer91, may be greater than twice a thickness W4of the epitaxial layer2directly below the anode p-type region3.

If the distance Y between adjacent ones of the anode p-type regions3is greater than twice the thickness W4of the epitaxial layer2directly below the anode p-type region3, in response to application of a rated voltage in a direction opposite a forward direction, an n-type region having the width W2of a depletion layer like in a Schottky barrier diode in the absence of the anode p-type region3illustrated inFIG. 11is partially formed without being influenced by the depletion layer extending in the direction in the plane of the wafer from the anode p-type region3.

If the anode p-type regions3are arranged to be spaced at a wide interval therebetween, an operating region for the Schottky barrier diode can be extended. This makes it possible to achieve the effect of this embodiment while minimizing influence caused by increase in the ON resistance.

FIGS. 12 and 13are sectional views each illustrating how a test is implemented by applying a voltage using the semiconductor device of this embodiment.

As illustrated inFIG. 13, a measurement method using the semiconductor device of this embodiment may be a measurement method for measurement of a high current with a low voltage such as forward direction measurement implemented by bringing a probe needle25into contact with a region other than a region in which the anode p-type region3is formed. Measuring a high current with a low voltage mentioned herein means making measurement by applying a voltage of 0 V or more and 5 V or less in a forward direction, and causing a current of 1 A or more to flow as a rough indication of a current capacity in one probe.

A current quantity allowed to flow in one probe needle21is determined in advance, so that many probe needles21are required for measurement of a high current. Except for initial failure such as short circuit between an anode and a cathode, a spot breakdown does not occur during measurement of a high current with a low voltage. A chip subjected to initial failure can be removed by screening.

Thus, for measurement of a high current with a low voltage, a region to be contacted by the probe needle21is not required to be limited to a region above the position of the anode p-type region3. Specifically, as illustrated inFIG. 13, contact by the probe needle25is allowed in addition to contact by the probe needle21.

By contrast, for making measurement by applying a high voltage that might result in the occurrence of a spot breakdown, the measurement is made using probe needles of a number smaller than the number of probe needles used for measurement of a high current with a low voltage, as illustrated inFIG. 12.

As a result of the foregoing, the number of the anode p-type regions3for suppressing concentration of a leakage current can be reduced. As a result, reduction in the ON resistance is achieved.

Second Embodiment

A method of measuring a semiconductor device relating to a second embodiment will be described below. In the description given below, a structure similar to the structure described in the foregoing embodiment will be given the same sign and illustrated with the same sign in the drawings. Detailed description of this structure will be omitted, where appropriate.

FIG. 14is a sectional view schematically illustrating the configuration of a semiconductor device, more specifically, a Schottky barrier diode (SBD) relating to this embodiment. The configuration illustrated inFIG. 14includes a high barrier Schottky electrode14having a higher Schottky barrier than the Schottky electrode11and provided as an alternative to the anode p-type region3in the configuration illustrated in the first embodiment. The high barrier Schottky electrode14is formed on the upper surface of the epitaxial layer2. The high barrier Schottky electrode14may be configured to include a plurality of regions arranged in a concentric pattern in a plan view. The high barrier Schottky electrode14may alternatively be configured to include a single region having a concentric pattern, specifically, only a circular contour in a plan view.

In the foregoing configuration, the high barrier Schottky electrode14generates a leakage current lower than a leakage current generated by the Schottky electrode11. Thus, the occurrence of a spot breakdown is reduced.

Thus, for making measurement by applying a high voltage to the semiconductor device, the probe needle21is brought into contact with a position at which the high barrier Schottky electrode14exists directly below the anode electrode12, as illustrated inFIG. 15. As a result, the occurrence of a spot breakdown near the probe needle21is reduced.FIG. 15is a sectional view schematically illustrating the configuration of the semiconductor device relating to this embodiment.

Thus, it becomes possible to suppress damage caused by a spot breakdown on the probe needle21. As a result, necessity to interrupt a test and exchange the probe needle21can be eliminated.

The Schottky electrode11may be made of titanium (Ti) having a barrier height of 0.95 eV relative to 4H—SiC. The high barrier Schottky electrode14may be made of nickel (Ni) having a barrier height of 1.62 eV relative to 4H—SiC.

Like in the case of the first embodiment, the size of the high barrier Schottky electrode14is desirably larger than the size of the probe needle21in a cross section.

FIGS. 16 and 17are sectional views each illustrating how a test is implemented by applying a voltage using the semiconductor device of this embodiment.

As illustrated inFIG. 17, a measurement method using the semiconductor device relating to this embodiment may be a measurement method for measurement of a high current with a low voltage such as forward direction measurement implemented by bringing the probe needle25into contact with a region other than a region in which the high barrier Schottky electrode14is formed.

By contrast, for making measurement by applying a high voltage that might result in the occurrence of a spot breakdown, the measurement is made using probe needles of a number smaller than the number of probe needles used for measurement of a high current with a low voltage, as illustrated inFIG. 16.

As a result of the foregoing, the number of the high barrier Schottky electrodes14for suppressing concentration of a leakage current can be reduced. As a result, reduction in the ON resistance is achieved.

Third Embodiment

A method of measuring a semiconductor device relating to a third embodiment will be described below. In the description given below, a structure similar to the structure described in the foregoing embodiments will be given the same sign and illustrated with the same sign in the drawings. Detailed description of this structure will be omitted, where appropriate.

FIG. 18is a sectional view schematically illustrating the configuration of the semiconductor device, more specifically, a Schottky barrier diode (SBD) relating to this embodiment.FIG. 19is a plan view schematically illustrating the configuration of the semiconductor device relating to this embodiment.FIG. 18corresponds to a sectional view taken along AB inFIG. 19.

The configuration illustrated inFIG. 18includes a JBS region5as an alternative to the anode p-type region3in the configuration illustrated in the first embodiment.

The JBS region5is formed in a layer below the anode electrode12. Meanwhile, for the convenience of description, the JBS region5is illustrated in a perspective fashion inFIG. 19.

The JBS region5is a p-type region formed in the surface layer of the epitaxial layer2to be joined to the Schottky electrode11. Like in the case illustrated inFIG. 6, a distance between adjacent ones of the JBS regions5is less than twice the width of a depletion layer to extend from the JBS regions5in response to application of a rated voltage in a direction opposite a forward direction.

The JBS region5includes a plurality of p-type regions6arranged in a concentric pattern in a plan view. Specifically, the JBS region5includes an n-type region surrounded by the p-type regions in a plan view. Alternatively, the JBS region5may be configured to include a single region having a concentric pattern, specifically, only a circular contour in a plan view. The formation of the JBS region5reduces the area of a Schottky junction. Further, the presence of a depletion layer extending in a direction in the plane of a wafer from the p-type regions6constituting the JBS region5reduces the intensity of an electric field applied to a Schottky junction in the JBS region5. As a result of these configurations, a leakage current is reduced. Thus, the occurrence of a spot breakdown is reduced in the JBS region5.

As illustrated inFIG. 20, for making measurement by applying a high voltage to the semiconductor device, the probe needle21is brought into contact with a position at which the JBS region5exists directly below the anode electrode12. As a result, the occurrence of a spot breakdown near the probe needle21is reduced.FIG. 20is a sectional view schematically illustrating the configuration of the semiconductor device relating to this embodiment.

Thus, it becomes possible to suppress damage caused by a spot breakdown on the probe needle21. As a result, necessity to interrupt a test and exchange the probe needle21can be eliminated.

The size of the JBS region5is desirably larger than the size of the probe needle21in a cross section.

FIGS. 21 and 22are sectional views each illustrating how a test is implemented by applying a voltage using the semiconductor device of this embodiment.

As illustrated inFIG. 22, a measurement method using the semiconductor device of this embodiment may be a measurement method for measurement of a high current with a low voltage such as forward direction measurement implemented by bringing the probe needle25into contact with a region other than a region in which the JBS region5is formed.

By contrast, for making measurement by applying a high voltage that might result in the occurrence of a spot breakdown, the measurement is made using probe needles of a number smaller than the number of probe needles used for measurement of a high current with a low voltage, as illustrated inFIG. 21.

As a result of the foregoing, the number of the JBS regions5for suppressing concentration of a leakage current can be reduced. As a result, reduction in the ON resistance is achieved.

Fourth Embodiment

A method of measuring a semiconductor device relating to a fourth embodiment will be described below. In the description given below, a structure similar to the structure described in the foregoing embodiments will be given the same sign and illustrated with the same sign in the drawings. Detailed description of this structure will be omitted, where appropriate.

FIG. 23is a sectional view schematically illustrating the configuration of the semiconductor device, more specifically, a Schottky barrier diode (SBD) relating to this embodiment.FIG. 24is a plan view schematically illustrating the configuration of the semiconductor device relating to this embodiment.FIG. 23corresponds to a sectional view taken along AB inFIG. 24.

The configuration illustrated inFIG. 23includes a JBS region50formed in a Schottky junction area, in addition to the configuration illustrated in the first embodiment.

The JBS region50is formed in a part of the surface layer of the epitaxial layer2. The JBS region50includes a p-type region60contacting the Schottky electrode11, and an n-type region contacting the Schottky electrode11. The p-type region60and the n-type region are formed alternately in a sectional view. In the illustration ofFIG. 24, the p-type region60constituting the JBS region50has a stripe shape.

The p-type region60constituting the JBS region50is formed to a width smaller than the width of the anode p-type region3. A dopant concentration in the p-type region60is equal to or higher than a dopant concentration in the anode p-type region3.

The JBS region50and the anode p-type region3are formed in a layer below the anode electrode12. Meanwhile, for the convenience of description, the JBS region50and the anode p-type region3are illustrated in a perspective fashion inFIG. 24.

As described above, a leakage current is lower at a pn junction than at a Schottky junction. Thus, a leakage current becomes lower at the anode p-type region3having a pn junction than at the JBS region50having both a Schottky junction and a pn junction. In this way, the occurrence of a spot breakdown is reduced in the anode p-type region3.

As illustrated inFIG. 25, for making measurement by applying a high voltage to the semiconductor device, the probe needle21is brought into contact with a position at which the anode p-type region3exists directly below the anode electrode12. As a result, the occurrence of a spot breakdown near the probe needle21is reduced.FIG. 25is a sectional view schematically illustrating the configuration of the semiconductor device relating to this embodiment.

Thus, it becomes possible to suppress damage caused by a spot breakdown on the probe needle21. As a result, necessity to interrupt a test and exchange the probe needle21can be eliminated.

Meanwhile, if a dopant concentration in the anode p-type region3increases, electric field intensity at a pn junction area is increased to increase a leakage current in the anode p-type region3. Thus, a dopant concentration in the anode p-type region3is required to be equal to or lower than a dopant concentration in the p-type region60constituting the JBS region50.

Like in the first embodiment, a range in which the anode p-type region3is formed is desirably greater than the size of the probe needle21.

FIGS. 26 and 27are sectional views each illustrating how a test is implemented by applying a voltage using the semiconductor device of this embodiment.

As illustrated inFIG. 27, a measurement method using the semiconductor device of this embodiment may be a measurement method for measurement of a high current with a low voltage such as forward direction measurement implemented by bringing the probe needle25into contact with a region other than a region in which the JBS region50is formed.

By contrast, for making measurement by applying a high voltage that might result in the occurrence of a spot breakdown, the measurement is made using probe needles of a number smaller than the number of probe needles used for measurement of a high current with a low voltage, as illustrated inFIG. 26.

As a result of the foregoing, the number of the JBS regions50for suppressing concentration of a leakage current can be reduced. As a result, reduction in the ON resistance is achieved.

Effect Achieved by Foregoing Embodiments

Exemplary effects achieved by the foregoing embodiments will be described next. These effects in the following description are achieved based on the specific configurations illustrated in the foregoing embodiments. However, these configurations may be replaced by different specific configurations illustrated in the description of the present application, as long as comparable effects are achieved by such different specific configurations.

This replacement may be done across a plurality of embodiments. Specifically, configurations illustrated in different embodiments may be combined to achieve comparable effects.

According to the foregoing embodiments, in a method of measuring the semiconductor device, a voltage is applied while the probe needle21is brought into contact with the upper surface of the anode electrode12in a range in which the contour of at least one second conductivity type region is formed in a plan view. The second conductivity type region corresponds to the anode p-type region3, for example. The silicon carbide semiconductor device used for the measurement includes the silicon carbide semiconductor substrate1of the first conductivity type, the epitaxial layer2of the first conductivity type, at least one anode p-type region3of the second conductivity type, the Schottky electrode11, the anode electrode12, and the cathode electrode13. The epitaxial layer2is formed on the upper surface of the silicon carbide semiconductor substrate1. The anode p-type region3is formed in a part of the surface layer of the epitaxial layer2to have a contour. The Schottky electrode11is formed to cover the upper surface of the epitaxial layer2and the upper surface of the anode p-type region3. The anode electrode12is formed on the upper surface of the Schottky electrode11. The cathode electrode13is formed on the lower surface of the silicon carbide semiconductor substrate1.

The foregoing configuration makes it possible to reduce the occurrence of a spot breakdown near the probe needle. More specifically, for a test implemented by applying a high voltage, the probe needle21is brought into contact with a region in which the anode p-type region3is located in a plan view. A pn junction is capable of reducing a leakage current, compared to a leakage current flowing in a Schottky junction, so that concentration of a leakage current can be suppressed around the probe needle21. This reduces the occurrence of a spot breakdown around the probe needle21to be caused by concentration of a leakage current, so that the probe needle21becomes less likely to be damaged by a spot breakdown. As a result, a workload of interrupting the test and exchanging the probe needle21can be reduced.

Structures illustrated in the description of the present application different from the structures described above can be omitted, where appropriate. Specifically, the foregoing effects are achieved only by the configurations described above.

Meanwhile, if at least one of the different structures illustrated in the description of the present application, specifically, a different one of the structures illustrated in the description of the present application and not listed as one of the foregoing structures is added to the foregoing structures, effects comparable to the foregoing effects are still achieved.

According to the foregoing embodiments, for application of a voltage higher than a threshold to the silicon carbide semiconductor device, the probe needle21is brought into contact with the upper surface of the anode electrode12only in a range in which the contour of the at least one anode p-type region3is formed in a plan view. For application of a voltage lower than the threshold to the silicon carbide semiconductor device, the probe needle21is brought into contact with the upper surface of the anode electrode12in the range in which the contour of the at least one anode p-type region3is formed in a plan view. Further, the probe needle25is brought into contact with the upper surface of the anode electrode12in a range in which the anode p-type region3is not formed in a plan view. In this configuration, if a voltage lower than the threshold is to be applied to the silicon carbide semiconductor device, for example, the probe needle21can be brought into contact further with the upper surface of the anode electrode12in the range in which the anode p-type region3is not formed in a plan view for implementation of a test. This makes it possible to reduce the number of positions at which the anode p-type regions3for suppressing concentration of a leakage current are to be formed. As a result, reduction in the ON resistance of the silicon carbide semiconductor device is achieved.

According to the foregoing embodiments, the anode p-type region3is a region of the second conductivity type in its entirety within a contour in a plan view. In this configuration, a leakage current is unlikely to be concentrated around the probe needle21contacting a position corresponding to a position at which the anode p-type region3is formed. This reduces the occurrence of a spot breakdown around the probe needle21to be caused by concentration of a leakage current, so that the probe needle21becomes less likely to be damaged by a spot breakdown. As a result, a workload of interrupting a test and exchanging the probe needle21can be reduced.

According to the foregoing embodiments, the silicon carbide semiconductor device includes at least one JBS region50of the second conductivity type. The JBS region50is formed in a part of the surface layer of the epitaxial layer2. The JBS region50includes a region of the second conductivity type contacting the Schottky electrode11, and a region of the first conductivity type contacting the Schottky electrode11. The region of the second conductivity type constituting the JBS region50, specifically, the p-type region60is formed to a width smaller than the width of the anode p-type region3. A dopant concentration in the JBS region50is higher than a dopant concentration in the anode p-type region3. In this configuration, a leakage current is unlikely to be concentrated around the probe needle21contacting a position corresponding to a position at which the anode p-type region3is formed. This reduces the occurrence of a spot breakdown around the probe needle21to be caused by concentration of a leakage current, so that the probe needle21becomes less likely to be damaged by a spot breakdown. As a result, a workload of interrupting a test and exchanging the probe needle21can be reduced.

According to the foregoing embodiments, the second conductivity type region includes a region of the first conductivity type surrounded by a region of the second conductivity type in a plan view. The second conductivity type region corresponds to the JBS region5, for example. In this configuration, a leakage current is unlikely to be concentrated around the probe needle21contacting a position corresponding to a position at which the JBS region5is formed. This reduces the occurrence of a spot breakdown around the probe needle21to be caused by concentration of a leakage current, so that the probe needle21becomes less likely to be damaged by a spot breakdown. As a result, a workload of interrupting a test and exchanging the probe needle21can be reduced.

According to the foregoing embodiments, in a method of measuring the semiconductor device, a voltage is applied while the probe needle21is brought into contact with the upper surface of the anode electrode12in a range in which at least one second Schottky electrode is formed in a plan view. The second Schottky electrode corresponds to the high barrier Schottky electrode14, for example. The silicon carbide semiconductor device used for the measurement includes the silicon carbide semiconductor substrate1of the first conductivity type, the epitaxial layer2of the first conductivity type, a first Schottky electrode, the high barrier Schottky electrode14, the anode electrode12, and the cathode electrode13. The first Schottky electrode corresponds to the Schottky electrode11, for example. The epitaxial layer2of the first conductivity type is formed on the upper surface of the silicon carbide semiconductor substrate1. The Schottky electrode11includes at least one Schottky electrode11formed on the upper surface of the epitaxial layer2. The high barrier Schottky electrode14includes at least one high barrier Schottky electrode14formed on the upper surface of the epitaxial layer2. The high barrier Schottky electrode14forms a Schottky barrier between the high barrier Schottky electrode14and the epitaxial layer2higher than a Schottky barrier formed between the Schottky electrode11and the epitaxial layer2. The anode electrode12is formed on the upper surface of the Schottky electrode11and the upper surface of the high barrier Schottky electrode14. The cathode electrode13is formed on the lower surface of the silicon carbide semiconductor substrate1.

The foregoing configuration makes it possible to reduce the occurrence of a spot breakdown near the probe needle. More specifically, for a test implemented by applying a high voltage, the probe needle21is brought into contact with a region in which the high barrier Schottky electrode14is located in a plan view. A pn junction is capable of reducing a leakage current, compared to a leakage current flowing in a Schottky junction, so that concentration of a leakage current can be suppressed around the probe needle21. This reduces the occurrence of a spot breakdown around the probe needle21to be caused by concentration of a leakage current, so that the probe needle21becomes less likely to be damaged by a spot breakdown. As a result, a workload of interrupting the test and exchanging the probe needle21can be reduced.

Structures illustrated in the description of the present application different from the structures described above can be omitted, where appropriate. Specifically, the foregoing effects are achieved only by the configurations described above.

Meanwhile, if at least one of the different structures illustrated in the description of the present application, specifically, a different one of the structures illustrated in the description of the present application and not listed as one of the foregoing structures is added to the foregoing structures, effects comparable to the foregoing effects are still achieved.

Unless otherwise specified, order of performing each process is changeable.

According to the foregoing embodiments, for application of a voltage higher than a threshold to the silicon carbide semiconductor device, the probe needle21is brought into contact with the upper surface of the anode electrode12only in a range in which the at least one high barrier Schottky electrode14is formed in a plan view. For application of a voltage lower than the threshold to the silicon carbide semiconductor device, the probe needle21is brought into contact with the upper surface of the anode electrode12in the range in which the at least one high barrier Schottky electrode14is formed in a plan view. Further, the probe needle25is brought into contact with the upper surface of the anode electrode12in a range in which the high barrier Schottky electrode14is not formed in a plan view. In this configuration, if a voltage lower than the threshold is to be applied to the silicon carbide semiconductor device, for example, the probe needle21can be brought into contact further with the upper surface of the anode electrode12in the range in which the high barrier Schottky electrode14is not formed in a plan view for implementation of a test. This makes it possible to reduce the number of positions at which the high barrier Schottky electrodes14for suppressing concentration of a leakage current are to be formed. As a result, reduction in the ON resistance of the silicon carbide semiconductor device is achieved.

Modifications of Foregoing Embodiments

In the foregoing embodiments, components may be described from the viewpoint of a material quantity, a material, a dimension, a shape, arrangement relative to each other, or a condition for implementation, for example. These are in all aspects illustrative and not restrictive, and the components are not limited to these viewpoints given in the description of the present application.

Thus, numerous modifications and equivalents not illustrated are assumed to be included within the technical scope disclosed in the description of the present application. These modifications include a modification, addition, or omission of at least one component, and extraction of at least one component from at least one embodiment and combination of the extracted component with a component in a different embodiment, for example.

As long as no contradiction is to occur, a component described in a “singular form” in the foregoing embodiments may include “one or more” such components.

Further, each component described in each of the foregoing embodiments is a conceptual unit. The technical scope disclosed in the description of the present application covers a case where one component is formed of a plurality of structures, a case where one component corresponds to a part of some structure, and a case where a plurality of components is provided in one structure.

Each component described in each of the foregoing embodiments includes a structure having a different configuration or a different shape, as long as such a structure fulfills the same function.

The explanation given in the description of the present application should in all aspects be referred to for all purposes relating to the technique in the description of the present application and should never be recognized as a background art.

In the foregoing embodiments, if the name of a material is given without particular designation, for example, this material includes a material such as an alloy containing a different additive, as long as no contradiction is to occur.

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