Semiconductor device and manufacturing method thereof

Abstract

To provide a technique for accurately measuring the forward voltage of a pn diode in a temperature sensing section.SOLUTION: A semiconductor device 1 having a temperature sensing section 30 includes a cathode region 46 which is an n-type semiconductor, an anode region 48 which is a p-type semiconductor, a cathode electrode 32 in contact with the cathode region, an anode electrode 34 in contact with the anode region, and Kelvin electrodes 36, 36K, 36A in contact with at least one of the cathode region and the anode region.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a semiconductor device having a temperature sensing portion and a manufacturing method thereof. [Background technology]

[0002] In order to prevent the semiconductor device from overheating, a temperature sensor for monitoring the temperature is mounted on the semiconductor device. The temperature sensor includes a cathode region which is an n-type semiconductor, an anode region which is a p-type semiconductor, a cathode electrode in contact with the cathode region, and an anode electrode in contact with the anode region. A current source and a voltage measurement circuit are connected between the cathode electrode and the anode electrode. The forward voltage of a pn diode formed by the cathode region and the anode region changes depending on the temperature of the semiconductor device. The temperature of the semiconductor device is monitored based on the voltage measured by the voltage measurement circuit. Examples of semiconductor devices having such a temperature sensor are disclosed in Patent Documents 1 to 3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-201357 A [Patent Document 2] JP 2008-235600 A [Patent Document 3] JP 2017-174863 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a voltage measurement circuit is connected between the cathode electrode and the anode electrode, the measured voltage includes a voltage drop due to the contact resistance between the cathode region and the cathode electrode and a voltage drop due to the contact resistance between the anode region and the anode electrode. Variations in these voltage drops make it difficult to accurately measure the forward voltage of the pn diode. This specification aims to provide a technique for accurately measuring the forward voltage of the pn diode in the temperature sensing section. [Means for solving the problem]

[0005] An embodiment of a semiconductor device (1) having a temperature sensor (30) disclosed in the present specification may include a cathode region (46) which is an n-type semiconductor, an anode region (48) which is a p-type semiconductor, a cathode electrode (32) in contact with the cathode region, an anode electrode (34) in contact with the anode region, and a Kelvin electrode (36, 36K, 36A) in contact with at least one of the cathode region and the anode region. In this semiconductor device, a current source is connected between the cathode electrode and the anode electrode, and a current flows through a pn diode formed by the cathode region and the anode region. The Kelvin electrode is wired separately from the path through which the main current flows. When the Kelvin electrode is in contact with the cathode region, a voltage measurement circuit may be connected between the Kelvin electrode and the anode electrode. When the Kelvin electrode is in contact with the anode region, a voltage measurement circuit may be connected between the Kelvin electrode and the cathode electrode. When the Kelvin electrode has a cathode Kelvin electrode and an anode Kelvin electrode, the cathode Kelvin electrode is in contact with the cathode region, and the anode Kelvin electrode is in contact with the anode region, a voltage measurement circuit may be connected between the cathode Kelvin electrode and the anode Kelvin electrode. With this configuration, the voltage measurement value measured by the voltage measurement circuit is free from the effects of at least one of the voltage drop due to the contact resistance between the cathode region and the cathode electrode and the voltage drop due to the contact resistance between the anode region and the anode electrode. Therefore, in the semiconductor device, the forward voltage of the pn diode can be accurately measured.

[0006] This specification discloses a method for manufacturing a semiconductor device (1) having a temperature sensor (30) including a cathode region (46) which is an n-type semiconductor, an anode region (48) which is a p-type semiconductor, a cathode electrode (32) in contact with the cathode region, an anode electrode (34) in contact with the anode region, and a Kelvin electrode (36) in contact with at least one of the cathode region and the anode region. This manufacturing method may include a step of simultaneously forming the cathode electrode, the anode electrode, and the Kelvin electrode. According to this manufacturing method, the Kelvin electrode can be formed without adding a new step. [Brief description of the drawings]

[0007] [Figure 1] 1 is a plan view illustrating a schematic layout of a semiconductor device disclosed in this specification. [Diagram 2] 2 is a cross-sectional view of a main part that illustrates a schematic view of a temperature sensing portion, the cross-sectional view corresponding to line II-II in FIG. 1. [Diagram 3] FIG. 1 is a diagram showing an equivalent circuit of a semiconductor device disclosed in this specification. [Figure 4] FIG. 13 is a diagram showing an equivalent circuit of a modified example of the semiconductor device disclosed in this specification. [Diagram 5] FIG. 13 is a diagram showing an equivalent circuit of a modified example of the semiconductor device disclosed in this specification. [Figure 6] FIG. 11 is a plan view illustrating a layout of a modified example of the semiconductor device disclosed in this specification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] As shown in FIG. 1, the semiconductor device 1 is a type of semiconductor device called a power semiconductor element, and may be, for example, a MOSFET or an IGBT, although it is not particularly limited thereto. The semiconductor device 1 includes a semiconductor substrate 10. The material of the semiconductor substrate 10 is not particularly limited, and may be, for example, silicon carbide. The semiconductor substrate 10 is partitioned into a pair of active regions 12 and an outer peripheral region 14 provided around the pair of active regions 12. Each of the pair of active regions 12 is a region in which a gate constituting a transistor is disposed. The outer peripheral region 14 is provided with a gate pad 20 and a temperature sensor 30. Note that the temperature sensor 30 in this example is provided in the outer peripheral region 14 of the semiconductor substrate 10, but may be provided within the active region 12.

[0009] 2, the semiconductor substrate 10 has a portion where an n-type semiconductor layer 42 and a p-type semiconductor layer 44 are stacked. The n-type semiconductor layer 42 is a drift layer constituting a MOSFET or an IGBT. The p-type semiconductor layer 44 is a body layer constituting a MOSFET or an IGBT.

[0010] The temperature sensing section 30 has a cathode region 46 and an anode region 48 which form a pn diode for sensing temperature.

[0011] The cathode region 46 is a semiconductor region containing n-type impurities, and is formed in the semiconductor substrate 10. The cathode region 46 is formed on the p-type semiconductor layer 44, and is disposed at a position exposed on the upper surface of the semiconductor substrate 10. The cathode region 46 is disposed so as to be in contact with the p-type semiconductor layer 44 and surrounded by the p-type semiconductor layer 44. As a result, the cathode region 46 is separated from the n-type semiconductor layer 42 by the p-type semiconductor layer 44.

[0012] The anode region 48 is a semiconductor region containing p-type impurities, and is formed in the semiconductor substrate 10. The anode region 48 is formed on the cathode region 46, and is disposed at a position exposed on the upper surface of the semiconductor substrate 10. The anode region 48 is disposed so as to be in contact with the cathode region 46 and to be surrounded by the cathode region 46. As a result, the anode region 48 is separated from the p-type semiconductor layer 44 by the cathode region 46.

[0013] The cathode region 46 and the anode region 48 are formed in the semiconductor substrate 10 using ion implantation technology. The cathode region 46 and the anode region 48 constituting the pn diode may be formed in polysilicon deposited on the semiconductor substrate 10.

[0014] The temperature sensing section 30 further includes a cathode electrode 32, an anode electrode 34, and a Kelvin electrode 36.

[0015] The cathode electrode 32 is provided on the semiconductor substrate 10, and is in contact with the cathode region 46 exposed on the upper surface of the semiconductor substrate 10 through a contact hole in the interlayer insulating film 50. The cathode electrode 32 is electrically connected to the cathode pad 32b through the cathode wiring 32a (see FIG. 1). Here, the cathode electrode 32 is a metal portion provided in a range in contact with the cathode region 46. The cathode wiring 32a is a metal portion coated with an insulating protective film (not shown) formed on the interlayer insulating film 50 between the cathode electrode 32 and the cathode pad 32b. The cathode pad 32b is a metal portion exposed from the insulating protective film (not shown). The material of the cathode metal wiring portion consisting of the cathode electrode 32, the cathode wiring 32a, and the cathode pad 32b is not particularly limited, but may be, for example, aluminum. The cathode metal wiring portion may be formed using a deposition technique. Furthermore, in order to improve the ohmic properties, a nickel silicide layer, for example a nickel layer silicided, may be provided on the contact surface between the cathode electrode 32 and the cathode region 46, although this is not particularly limited. Such a nickel silicide layer may be formed by forming a nickel layer using a deposition technique and then performing an annealing process.

[0016] The anode electrode 34 is provided on the semiconductor substrate 10, and is in contact with the anode region 48 exposed on the upper surface of the semiconductor substrate 10 through a contact hole in the interlayer insulating film 50. The anode electrode 34 is electrically connected to the anode pad 34b through the anode wiring 34a (see FIG. 1). Here, the anode electrode 34 is a metal portion provided in a range in contact with the anode region 48. The anode wiring 34a is a metal portion coated with an insulating protective film (not shown) formed on the interlayer insulating film 50 between the anode electrode 34 and the anode pad 34b. The anode pad 34b is a metal portion exposed from the insulating protective film (not shown). The anode metal wiring portion, which is composed of the anode electrode 34, the anode wiring 34a, and the anode pad 34b, is formed in the same manufacturing process as the cathode metal wiring portion. In addition, a silicide layer may also be provided on the contact surface between the anode electrode 34 and the anode region 48.

[0017] The Kelvin electrode 36 is provided on the semiconductor substrate 10 and contacts the anode region 48 exposed on the upper surface of the semiconductor substrate 10 through a contact hole in the interlayer insulating film 50. The Kelvin electrode 36 contacts the anode region 48 at a position different from that of the anode electrode 34. The Kelvin electrode 36 is electrically connected to the Kelvin pad 36b through the Kelvin wiring 36a (see FIG. 1). Here, the Kelvin electrode 36 is a metal portion provided in a range contacting the anode region 48. The Kelvin wiring 36a is a metal portion coated with an insulating protective film (not shown) formed on the interlayer insulating film 50 between the Kelvin electrode 36 and the Kelvin pad 36b. The Kelvin pad 36b is a metal portion exposed from the insulating protective film (not shown). The Kelvin metal wiring portion consisting of the Kelvin electrode 36, the Kelvin wiring 36a, and the Kelvin pad 36b is formed in the same manufacturing process as the cathode metal wiring portion and the anode metal wiring portion. A silicide layer may also be provided on the contact surface between the Kelvin electrode 36 and the anode region 48 .

[0018] A current source 52 is connected between the cathode electrode 32 and the anode electrode 34. The current source 52 is configured to pass a constant current in the forward direction through the pn diode formed by the cathode region 46 and the anode region 48. A voltage measurement circuit 54 is connected between the cathode electrode 32 and the Kelvin electrode 36. The voltage measurement circuit 54 is configured to measure the voltage between the cathode electrode 32 and the Kelvin electrode 36, i.e., the forward voltage of the pn diode formed by the cathode region 46 and the anode region 48.

[0019] 3 shows an equivalent circuit of the semiconductor device 1. In this equivalent circuit, an example is shown in which a MOSFET is formed as the transistor. When the temperature of the semiconductor substrate 10 rises due to Joule heat of the current flowing through the transistor, the forward voltage of the temperature sensing pn diode decreases. In this way, the forward voltage of the temperature sensing pn diode varies depending on the temperature of the semiconductor substrate 10. The temperature sensing unit 30 can measure the temperature of the semiconductor substrate 10 based on the voltage measurement value measured by the voltage measurement circuit 54.

[0020] Here, consider a temperature sensor unit of a comparative example in which a Kelvin metal wiring portion is not formed. In the temperature sensor unit of the comparative example, a voltage measurement circuit 54 is connected between the cathode electrode 32 and the anode electrode 34. Therefore, the voltage measurement value of the temperature sensor unit of the comparative example includes a voltage drop due to the contact resistance between the anode electrode 34 and the anode region 48.

[0021] The p-type region of silicon carbide has a deep Fermi level due to the deep acceptor level. Therefore, the p-type region of silicon carbide is likely to form a Schottky contact with a metal electrode, and is unlikely to form an ohmic contact with a metal electrode. Therefore, the contact resistance between the anode electrode 34 and the anode region 48 is high. In addition, the contact resistance between the anode electrode 34 and the anode region 48 varies due to manufacturing variations. As a result, in the temperature sensor unit of the comparative example, there is a problem that it is difficult to accurately measure the fluctuation in the forward voltage of the pn diode for temperature sensing due to the influence of the voltage drop caused by the contact resistance between the anode electrode 34 and the anode region 48. Note that such a problem may occur in a semiconductor material other than silicon carbide.

[0022] On the other hand, in the temperature sensing unit 30 of this embodiment, by measuring the voltage between the cathode electrode 32 and the Kelvin electrode 36, the voltage drop due to the contact resistance between the anode electrode 34 and the anode region 48 is not included in the voltage measurement value. As a result, in the temperature sensing unit 30 of this embodiment, the influence of the contact resistance between the anode electrode 34 and the anode region 48 can be ignored, so that the fluctuation in the forward voltage of the pn diode can be accurately measured. Furthermore, in the temperature sensing unit 30 of this embodiment, the variation in the voltage drop due to the resistance and inductance of the anode metal wiring portion can also be ignored, so that in this respect too, the fluctuation in the forward voltage of the pn diode can be accurately measured.

[0023] A pn diode for temperature sensing is often configured by connecting multiple pn diodes in series to increase the voltage fluctuation with respect to temperature. In the temperature sensing section 30 of this embodiment, the effect of the contact resistance between the anode electrode 34 and the anode region 48 can be ignored, so that even if the fluctuation in the forward voltage of the pn diode is small, it can be measured sufficiently. Therefore, the temperature sensing section 30 of this embodiment can be configured with a small area because the number of pn diodes connected in series can be reduced. For example, in an example in which the temperature sensing section 30 is arranged in the active region 12, there is a problem that the invalid area increases if the number of pn diodes is large. The temperature sensing section 30 of this embodiment can be configured with a small area, so it is particularly useful when it is arranged in the active region 12.

[0024] 1, in the temperature sensing section 30, the wiring width of the Kelvin wiring 36a is formed to be wider than the cathode wiring 32a and the anode wiring 34a. This makes it possible to suppress the influence of variations in voltage drop due to the resistance and inductance of the Kelvin wiring 36a, and therefore makes it possible to accurately measure the fluctuation in the forward voltage of the pn diode.

[0025] In the above example, the temperature sensing unit 30 is configured so that the Kelvin electrode 36 is in contact with the anode region 48. Alternatively, the Kelvin electrode 36 may be configured so that it is in contact with the cathode region 46. In this case, a voltage measurement circuit 54 is connected between the anode electrode 34 and the Kelvin electrode 36. In this modification, the voltage drop due to the contact resistance between the cathode electrode 32 and the cathode region 46 is not included in the voltage measurement value. Even in this modification, the effect of the contact resistance between the cathode electrode 32 and the cathode region 46 can be ignored, so that the fluctuation in the forward voltage of the pn diode can be accurately measured.

[0026] As shown in FIG. 4, the Kelvin electrode 36 may have a cathode Kelvin electrode 36K and an anode Kelvin electrode 36A, the cathode Kelvin electrode 36K may be in contact with the cathode region 46, and the anode Kelvin electrode 36A may be in contact with the anode region 48. In this case, a voltage measurement circuit 54 is connected between the cathode Kelvin electrode 36K and the anode Kelvin electrode 36A. In this modification, the voltage drop due to the contact resistance between the anode electrode 34 and the anode region 48 and the contact resistance between the cathode electrode 32 and the cathode region 46 is not included in the voltage measurement value. In this modification, the influence of the contact resistance between the anode electrode 34 and the anode region 48 and the contact resistance between the cathode electrode 32 and the cathode region 46 can be ignored, so that the fluctuation of the forward voltage of the pn diode can be measured more accurately.

[0027] 5, a reverse connection protection diode 62 in the opposite direction to the temperature sensing pn diode may be connected in parallel to the temperature sensing pn diode between the cathode electrode 32 and the anode electrode 34. The reverse connection protection diode 62 may be formed in the semiconductor substrate 10 using ion implantation technology, or may be formed in polysilicon formed on the semiconductor substrate 10. When such a reverse connection protection diode 62 is provided, it is possible to prevent a reverse voltage from being applied to the temperature sensing pn diode. This improves the stability of temperature measurement in the temperature sensing unit 30.

[0028] As shown in Fig. 6, the Kelvin electrode 36 may be disposed outside the region between the cathode electrode 32 and the anode electrode 34. In the example shown in Fig. 1, the Kelvin electrode 36 is disposed between the cathode electrode 32 and the anode electrode 34. In the example shown in Fig. 1, the voltage measurement includes a voltage drop due to a current flowing through the anode region 48 below the Kelvin electrode 36 so as to cross the Kelvin electrode 36. On the other hand, in the example shown in Fig. 6, the effect of such a voltage drop is suppressed, so that the fluctuation in the forward voltage of the pn diode can be measured more accurately.

[0029] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0030] 1: semiconductor device, 10: semiconductor substrate, 30: temperature sensor, 32: cathode electrode, 34: anode electrode, 36: Kelvin electrode, 42: n-type semiconductor layer, 44: p-type semiconductor layer, 46: cathode region, 48: anode region, 50: interlayer insulating film, 52: current source, 54: voltage measurement circuit

Claims

1. A semiconductor device (1) having a temperature sensing unit (30), a cathode region (46) that is an n-type semiconductor; an anode region (48) that is a p-type semiconductor; a cathode electrode (32) in contact with the cathode region; an anode electrode (34) in contact with the anode region; a Kelvin electrode (36, 36K, 36A) in contact with at least one of the cathode region and the anode region.

2. The semiconductor device further includes a silicon carbide semiconductor substrate (10) on which a transistor is formed, The semiconductor substrate has a portion where an n-type semiconductor layer (42) and a p-type semiconductor layer (44) are laminated, the cathode region is disposed in contact with the p-type semiconductor layer and surrounded by the p-type semiconductor layer, the anode region is disposed so as to be in contact with the cathode region and to be surrounded by the cathode region, The semiconductor device according to claim 1 , wherein the Kelvin electrode is in contact with the anode region.

3. The Kelvin electrodes include a cathode Kelvin electrode (36K) and an anode Kelvin electrode (36A), the cathode Kelvin electrode is in contact with the cathode region; 2. The semiconductor device according to claim 1, wherein the anode Kelvin electrode is in contact with the anode region.

4. 2. The semiconductor device according to claim 1, wherein a contact surface between said Kelvin electrode and at least one of said cathode region and said anode region is silicided.

5. 5. The semiconductor device according to claim 1, wherein the Kelvin electrode is disposed outside a region between the cathode electrode and the anode electrode.

6. A method for manufacturing a semiconductor device (1) having a temperature sensing section (30), the temperature sensing section (30) including a cathode region (46) which is an n-type semiconductor, an anode region (48) which is a p-type semiconductor, a cathode electrode (32) in contact with the cathode region, an anode electrode (34) in contact with the anode region, and a Kelvin electrode (36) in contact with at least one of the cathode region and the anode region, the method comprising the steps of: forming the cathode electrode, the anode electrode, and the Kelvin electrode simultaneously.

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