JP2008021930A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device constituted by juxtaposing an MOS and an SBD on a semiconductor substrate, superior in recovery characteristic of a diode, reducible in forward direction loss, free of decreases in breakdown voltage and surge tolerance, superior in switching characteristic, compact in structure, and inexpensive. <P>SOLUTION: The semiconductor device 100 has embedded trenches T1 and T2 formed linearly without crossing each other, and a predetermined region at a surface layer divided into a plurality of partition regions R1 and R2. In the first partition region R1, a layer 33 of a second conductivity type to become a channel of the MOS is formed, polycrystalline silicon in the first embedded trench T1 is connected to a gate wiring, and polycrystalline silicon in the second embedded trench T2 is connected to a source wiring or the gate wiring. In the second partition region R2, a layer 30a of a first conductivity type is exposed on a surface and connected to the source wiring, and a Schottky barrier is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on one semiconductor substrate.

  An inverter circuit for driving a load such as an in-vehicle motor is an exchange between direct current and alternating current, converts a direct current voltage into an alternating current voltage, and supplies power to the load motor and the like. An inverter circuit for driving an inductive motor is composed of a MOS transistor (hereinafter abbreviated as MOS) or an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) which is a switching element, and a free wheel diode (hereinafter abbreviated as FWD). The Here, the FWD bypasses and recirculates the current flowing through the motor while the MOS is off so that the current flowing through the motor itself does not change due to the switching of the MOS. More specifically, when the MOS that connected the DC power source and the motor and applied the voltage to the motor is turned off, the current flowing through the motor passes through the FWD by the energy accumulated in the inductance L of the motor, and the DC is supplied. The current is reversed, and the motor is in a state equivalent to a reverse DC voltage being applied. As a result, the AC voltage can be supplied from the DC power supply by switching without suddenly interrupting the motor current by switching the MOS. In order to perform such an operation, the inverter circuit requires an FWD connected in antiparallel to the MOS. In the inverter circuit, a low on-resistance and a low switching loss are required for the MOS functioning as a switching element. For FWD, recovery characteristics and forward loss are important characteristics.

  When the MOS or IGBT, which is the switching element, is formed as a vertical MOS transistor having a trench gate structure, a P conductivity type layer serving as a channel formation region of the transistor is formed on the surface layer portion on the main surface side of the N conductivity type semiconductor substrate. Therefore, it is possible to configure a (body) diode by using the PN junction at the interface and to make it an FWD. In this structure, since the vertical MOS transistor and the body diode are disposed adjacent to each other, a semiconductor device having good switching characteristics can be basically obtained. However, the body diode formed as described above has a problem that the recovery time is long and the forward loss is large.

  In order to overcome the problem of the body diode using a PN junction, the use of a Schottky barrier diode (hereinafter abbreviated as SBD) has been studied. For example, Japanese Patent Laid-Open No. 2002-37389 (Patent Document 1) discloses a semiconductor device in which a vertical MOS transistor having a trench gate structure and an SBD are provided on one semiconductor substrate.

  FIG. 18 is a diagram showing the structure of a conventional semiconductor device disclosed in Patent Document 1, and is a schematic cross-sectional view of a semiconductor device 90. FIG. 18 shows the structure of an SBD and several cells of NMOSFET (hereinafter abbreviated as MOS) having a trench gate structure formed on an N + / N− substrate.

  In the semiconductor device 90 of FIG. 18, a P base layer 12 is selectively formed in the MOS formation region 14 in the surface layer portion of the N− layer 11 of the N + / N− substrate. An N + source region 13 is selectively formed, and a gate trench having a depth reaching the N− layer 11 from the surface of the N + source region 13 is formed. The SBD formation region 28 is disposed so as to continuously surround, for example, the periphery of the P base layer 12 in the MOS formation region 14. The same process as that of the P base layer 12 is performed so as to surround the periphery of the SBD formation region 28. Thus, a guard ring region 17 is formed.

An interlayer insulating film 19 is deposited on the substrate of the MOS formation region 14, and a plurality of contact holes are opened at predetermined positions of the interlayer insulating film 19. A barrier metal 21 is formed on the surface of the N− layer 11 in the SBD formation region 28 and on a part of the surface of the N + source region 13 through a contact hole formed in the interlayer insulating film 19. The barrier metal 21 is a Schottky junction on the surface of the N− layer 11 in the SBD formation region 28, and an ohmic junction on the surface (high concentration region) of the N + source region 13. Furthermore, a first main electrode 1 made of metal is formed on the barrier metal 21 in common as an anode electrode of SBD and a source electrode of MOS. The second main electrode 22 is provided almost entirely on the back side of the chip in common as the MOS drain electrode and the SBD cathode electrode.
JP 2002-373890 A

  A semiconductor device 90 illustrated in FIG. 18 has a structure in which a MOS and an SBD are connected in antiparallel. The SBD can be used as an FWD, and the semiconductor device 90 can be applied to the inverter circuit. Since SBD has a lower threshold voltage than a PN junction diode such as the body diode, when used as an FWD, it has excellent recovery characteristics and can reduce forward loss.

  On the other hand, the body diode uses a P-conductivity type layer (corresponding to the P base layer 12 in FIG. 18) serving as a MOS channel formation region, whereas in the semiconductor device 90 in FIG. An independent SBD formation region 28 is disposed so as to continuously surround the periphery of the P base layer 12. For this reason, the semiconductor device 90 has a problem that the switching characteristics are basically poor, and the chip area increases and the chip cost increases.

  In order to suppress an increase in the chip area in the semiconductor device 90, a structure in which the SBD is arranged between adjacent gate trenches by increasing the interval between the gate trenches in the MOS formation region 14 is conceivable. However, in this structure, another problem arises that the breakdown voltage of the MOS is lowered because the interval between the gate trenches is increased. In addition, since the MOS and SBD are mounted in a limited area in the same structure, the area of the P base layer 12 of the MOS needs to be sufficiently narrow in consideration of the amount of lateral diffusion. However, the P base layer 12 of the MOS corresponds to the base of the parasitic bipolar transistor, and parasitic operation is likely to occur unless the area of the P base layer 12 is sufficiently secured. That is, there is a problem that the L load surge resistance is reduced.

  Therefore, the present invention is a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on a single semiconductor substrate, and has excellent diode recovery characteristics and can reduce forward loss. An object of the present invention is to provide a small and inexpensive semiconductor device that does not deteriorate the breakdown voltage and surge resistance of a transistor and has excellent switching characteristics.

  The semiconductor device according to claim 1 is a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided side by side on a semiconductor substrate of a first conductivity type, and the main surface side of the semiconductor substrate Embedded trenches in which polycrystalline silicon is embedded through an insulating film are formed in a plurality of lines that do not cross each other in the substrate surface, and the surface layer on the main surface side of the semiconductor substrate in the substrate surface A predetermined region in the section is partitioned by the plurality of buried trenches and divided into a plurality of partition regions, and one of the plurality of partition regions has a channel of the vertical MOS transistor in one first partition region. A second conductivity type layer serving as a formation region is formed in a surface layer portion on the main surface side of the semiconductor substrate, and the plurality of buried trenches are formed. That is, the polycrystalline silicon in one first buried trench adjacent to the first conductivity type region which is the source region of the vertical MOS transistor formed in the surface layer portion of the second conductivity type layer is the vertical MOS. Polycrystalline silicon in the other second buried trench which is connected to the gate wiring of the transistor and is not adjacent to the first conductivity type region among the plurality of buried trenches is the source wiring or gate of the vertical MOS transistor. A first conductive type layer made of the semiconductor substrate is exposed on the surface on the main surface side in the other second partition region of the plurality of partition regions, and the vertical MOS A Schottky barrier of the Schottky barrier diode is formed and connected to a source wiring of a transistor.

  The semiconductor device has a structure in which a vertical MOS transistor and a Schottky barrier diode are provided on one semiconductor substrate and are connected in antiparallel. Therefore, the semiconductor device can be used as a switching element of an inverter circuit as it is. In this case, since the Schottky barrier diode in the semiconductor device has a threshold voltage lower than that of the PN junction diode, it has excellent recovery characteristics and can reduce forward loss.

  In the above semiconductor device, the vertical MOS transistor and the Schottky barrier diode are arranged not in separate regions, but in close proximity to each partition region partitioned by a buried trench in one predetermined region. Become. Therefore, the semiconductor device can be a small and inexpensive semiconductor device having excellent switching characteristics. In addition, by appropriately setting the interval between the plurality of buried trenches that partition the predetermined region, it is possible to suppress a decrease in breakdown voltage of the vertical MOS transistor disposed in each partition region. In addition, the second conductivity type layer, which is the channel formation region of the vertical MOS transistor, is limited in the lateral diffusion by the buried trench, so that the impurity concentration can be easily controlled and the parasitic operation of the parasitic bipolar transistor is suppressed. Thus, it is possible to prevent a decrease in the L load surge resistance.

  As described above, the above semiconductor device is a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on one semiconductor substrate, and has excellent diode recovery characteristics and forward loss. Thus, the transistor withstand voltage and surge withstand capability are not deteriorated and the semiconductor device is excellent in switching characteristics.

  In the semiconductor device, for example, as described in claim 2, the first metal layer which is the source wiring of the vertical MOS transistor so as to cover the predetermined region above the main surface side of the semiconductor substrate. It is preferable that a second metal layer that is a gate wiring of the vertical MOS transistor is formed so as to surround the first metal layer. According to this, the first metal layer as the source wiring is connected to the source region with the shortest length, and a large area can be secured. For this reason, wiring resistance is reduced, and the semiconductor device can be a large-capacity power element.

  The polycrystalline silicon in the second buried trench in the semiconductor device has a zero potential which is the same potential as the polycrystalline silicon in the first buried trench which is the gate electrode when the vertical MOS transistor is turned off. Connected to.

  According to a third aspect of the present invention, when the polycrystalline silicon in the second buried trench is connected to the source wiring of the vertical MOS transistor, it is unnecessary for the gate as compared with the case of connecting to the gate wiring. No parasitic capacitance is added. For this reason, deterioration of the switching speed of the vertical MOS transistor can be suppressed, which is preferable.

  In this case, for example, as in claim 4, the polycrystalline silicon in the second buried trench is connected to the polycrystalline silicon formed on the semiconductor substrate outside the predetermined region. It can be configured to be connected to the source wiring of the vertical MOS transistor via a silicon layer. Further, for example, as in claim 5, in the adjacent first partition region and second partition region, the first conductivity type region, the second conductivity type layer, and the second exposed on the surface of the semiconductor substrate. The polysilicon and the first conductivity type layer in the buried trench may be configured to be commonly connected by a metal layer formed on the semiconductor substrate.

  On the other hand, when the polycrystalline silicon in the second buried trench is connected to the gate wiring of the same vertical MOS transistor as the polycrystalline silicon in the first buried trench, the wiring structure is simplified, and a smaller semiconductor device is obtained. can do. In this case, for example, as described in claim 6, the polycrystalline silicon in which the polycrystalline silicon in the first buried trench and the second buried trench is formed on the semiconductor substrate outside the predetermined region. It can be configured to be connected to the gate wiring of the vertical MOS transistor through a polycrystalline silicon layer connected to silicon.

  In the semiconductor device, as described in claim 7, it is preferable that in the plurality of partition regions, the first partition region is arranged on both sides of the second partition region. In this case, a vertical MOS transistor is arranged on both sides of the Schottky barrier diode. For this reason, the carrier movement time between the vertical MOS transistor and the Schottky barrier diode is shortened, and the semiconductor device can be a semiconductor device particularly excellent in switching characteristics.

  The line-shaped buried trench in the semiconductor device may be curved, but as described in claim 8, it is more preferably linear. In this case, as described in claim 9, it is preferable that the plurality of buried trenches are formed in parallel to each other. The semiconductor device can be easily designed with high withstand voltage, and can be a highly reliable and inexpensive semiconductor device.

  When parallel and straight buried trenches are used, for example, the widths of the first partition region and the second partition region can be set to be equal to each other. Further, as described in claim 11, the width of the second partition region may be set smaller than the width of the first partition region. In this case, it is possible to further suppress the deterioration of the breakdown voltage accompanying the insertion arrangement of the second partition region (Schottky barrier diode).

  Moreover, in order to suppress the breakdown voltage degradation due to the insertion arrangement of the second partition region (Schottky barrier diode), two adjacent embeddings defining the second partition region as described in claim 12 A plurality of third buried trenches that connect the adjacent buried trenches in a ladder shape are formed with respect to the trench, and the second partition region is partitioned by the plurality of third buried trenches, You may comprise so that it may divide | segment into a small area | region. In this case, it is preferable that the small region has a substantially square shape.

  In order to improve the breakdown voltage, for example, as described in claim 14, the insulating film of the buried trench in the semiconductor device may be formed such that the bottom of the trench is thicker than the side wall of the trench. According to a fifteenth aspect of the present invention, the buried trench in the semiconductor device may be formed such that a curvature radius at the bottom of the trench is larger than a trench radius at the top of the trench.

  In order to obtain good characteristics with respect to the semiconductor device, it is particularly preferable that the first conductivity type is an N conductivity type and the second conductivity type is a P conductivity type, as described in claim 16.

  The semiconductor device described above is a small semiconductor device in which a vertical MOS transistor and a Schottky barrier diode are provided on one semiconductor substrate. Therefore, as described in claim 17, the semiconductor device is a semiconductor device used in an inverter circuit configured by a combination of a vertical MOS transistor and a free wheel diode (FWD), wherein the Schottky barrier diode is It is suitable when used as the FWD.

  Further, the semiconductor device is a small semiconductor device and can ensure high breakdown voltage. Therefore, the semiconductor device is suitable as an in-vehicle semiconductor device.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic sectional view of a semiconductor device 100 as an example of the semiconductor device according to the present invention. 2 is a schematic plan view showing an example of a plane pattern of the main part of the semiconductor device 100 shown in FIG. 1, and a cross section taken along a dashed line AA in FIG. 1 corresponds to FIG.

  A semiconductor device 100 shown in FIG. 1 and FIG. 2 includes a trench gate structure vertical MOS transistor (hereinafter abbreviated as MOS) and a Schottky barrier diode (hereinafter abbreviated as SBD). This is a semiconductor device provided alongside the substrate 30. In the following example, an NMOSFET (N-channel Metal Oxide Semiconductor Field Effect Transistor) will be described as an example of a vertical MOS transistor, but an IGBT (Insulated) in which a P-conductivity type layer is provided on the back side of the semiconductor substrate 30. Gate BipolarTransistor).

  In the semiconductor device 100, as shown in FIG. 1, a plurality of buried trenches T <b> 1 and T <b> 2 in which polycrystalline silicon 32 is buried via an insulating film 31 are formed in the surface layer portion on the main surface side of the semiconductor substrate 30. Yes. The polycrystalline silicon 32 in the trench is doped N + type. The interval between the buried trenches T1 and T2 is, for example, 2 μm to 5 μm. Of the plurality of buried trenches T1 and T2, a buried trench that functions as a MOS gate electrode is a first buried trench T1, and a buried trench that does not function as a MOS gate electrode is a second buried trench T2.

  As shown in FIG. 2, the plurality of buried trenches T1 and T2 are formed in a plurality of straight lines parallel to each other in the substrate surface. The predetermined internal region shown in FIG. 2 in the surface layer portion on the main surface side of the semiconductor substrate 30 is partitioned by a plurality of buried trenches T1 and T2, and is divided into a plurality of partition regions R1 and R2. 2 is a P-conductivity type (P) region 36 that is formed simultaneously with or separately from the P-conductivity type (P) layer 33 shown below.

  Of the plurality of partition regions R1 and R2, a region where the MOS is formed is referred to as a first partition region R1, and a region where the SBD is formed is referred to as a second partition region R2. In one first partition region R 1, a P-conductivity type (P) layer 33 that becomes a MOS channel formation region is formed on the surface layer portion on the main surface side of the semiconductor substrate 30. In the surface layer portion of the P conductivity type layer 33, an N conductivity type (N +) region 34, which is a source region of the MOS, is formed adjacent to the first buried trench T1. In the other second partition region R2, an N conductivity type (N−) layer 30a made of the semiconductor substrate 30 is exposed on the surface on the main surface side. An N conductivity type (N +) layer 35 for connection to the common MOS drain (D) electrode and SBD cathode electrode is formed on the surface layer portion on the back side of the semiconductor substrate 30. In FIG. 1, the N conductivity type (N +) layer 35 is drawn thinner than the N conductivity type (N−) layer 30a. However, the N conductivity type (N +) layer 35 is thin on a thick wafer made of the N conductivity type (N +) layer 35. The semiconductor substrate 30 may be an epitaxially grown N conductivity type (N−) layer 30a. In the semiconductor device 100, the N conductivity type (N−) layer 30a functions as a carrier drift layer with respect to the MOS and the SBD.

  Of the plurality of buried trenches T1 and T2, the polycrystalline silicon in the first buried trench T1 functioning as the MOS gate electrode is connected to the gate (G) wiring of the MOS. Further, the N conductivity type layer 30a exposed on the surface in the second partition region R2 is commonly connected to the source wiring of the MOS, and an SBD Schottky barrier is formed at the contact portion indicated by a thick line in FIG. . Further, in the semiconductor device 100 of FIG. 1, the polycrystalline silicon in the second buried trench T2 that is not adjacent to the N conductivity type (N +) region 34 that is the MOS source region and does not function as the gate electrode is the source of the MOS ( S) Connected to the wiring.

  In the semiconductor device 100, as shown in FIG. 2, a first metal layer M1 that is a source (S) wiring of a MOS is disposed above the main surface side of the semiconductor substrate 30 so as to cover a predetermined internal region. ing. A second metal layer M2 that is a MOS gate (G) wiring is formed so as to surround the first metal layer M1. According to this, the first metal layer M1 as the source wiring is connected to the source region with the shortest length, and a large area can be secured. For this reason, wiring resistance is reduced and the semiconductor device 100 can be made into a high capacity | capacitance power element.

  In the semiconductor device 100, as described above, the polycrystalline silicon in the second buried trench T2 is connected to the source (S) wiring of the MOS. For this reason, in the semiconductor device 100, as shown in FIG. 2, the polycrystalline silicon in the second buried trench T2 is connected to the polycrystalline silicon formed on the semiconductor substrate 30 outside the predetermined internal region. It is connected to the first metal layer M1 which is the source wiring of the MOS disposed above via the crystalline silicon layer 37a. Further, the polycrystalline silicon in the first buried trench T1 is connected to the gate line of the MOS disposed above via the polycrystalline silicon layer 37b connected to the polycrystalline silicon formed on the semiconductor substrate 30 in the outer peripheral region. Is connected to the second metal layer M2. In the figure, each portion surrounded by a thick broken line is a contact portion.

  Next, a method for manufacturing the semiconductor device 100 shown in FIGS. 1 and 2 will be briefly described.

  First, an N conductivity type (N−) layer 30a to be a drift layer is formed by epitaxial growth on the N + type semiconductor substrate to be the N conductivity type (N +) layer 35 shown in FIG. Next, a P conductivity type (P) region 36 to be an outer peripheral withstand voltage region shown in FIG. 2 is formed in a predetermined region of the surface layer portion of the N conductivity type (N−) layer 30a. Next, a P conductivity type (P) layer 33 is formed by ion implantation and thermal diffusion. Next, an oxide film serving as a mask for forming the first buried trench T1 and the second buried trench T2 is deposited by about 1 μm by the CVD method. Thereafter, the oxide film in a predetermined region (trench formation scheduled region) is selectively removed by photolithography and dry etching. At this time, as shown in FIG. 2, the length of the second buried trench T2 is set shorter than that of the first buried trench T1, and patterning is performed so that the terminal position is inside the first buried trench T1. Thereafter, the trench is dry-etched. (The trench depth is 1 to 3 μm in the case of MOS and 4 to 6 μm in the case of IGBT.) Next, damage removal processing (also serving as rounding of the trench corner) such as chemical dry etching and sacrificial oxidation was performed. Thereafter, the insulating film 31 shown in FIG. 1 is formed by thermal oxidation. Thereafter, polycrystalline silicon 32 doped with impurities is buried in the trench by CVD, and further deposited on the substrate (non-doped polycrystalline silicon may be deposited, and then impurities may be introduced), and then dry. By patterning by etching, polycrystalline silicon layers 37a and 37b shown in FIG. 2 are formed. At this time, in the gate lead region of the first buried trench T1, the polycrystalline silicon layer 37b is formed so as to cover the terminal portion of the first buried trench T1. In addition, on the outer periphery of the inner (cell) region, the polycrystalline silicon layer 37a is patterned so as to cover the terminal portion of the second buried trench T2. Thereafter, the trench mask oxide film is removed by dry etching. At this time, patterning is performed so that only the trench mask oxide film in the inner (cell) region is etched and not in the gate lead portion or the field portion. Thereafter, a P conductivity type layer 33, which is a MOS channel forming layer, is formed in the first partition region R1 between the first buried trench T1 and the second buried trench T2. Next, an N conductivity type (N +) region 34 which is a source region of the MOS is formed in the surface layer portion of the P conductivity type layer 33 in the first partition region R1. Thereafter, an interlayer insulating film is formed and a contact hole is opened. At this time, a contact hole for connecting to the source is formed on the polycrystalline silicon layer 37a covering the terminal portion of the second buried trench T2. Thereafter, the first metal layer M1 and the second metal layer M2 are formed of aluminum (Al) or the like. Thereby, the polycrystalline silicon in the second buried trench T2 is connected to the source wiring through the contact hole. Thereafter, the wafer thickness is reduced by backside grinding to form the drain electrode on the backside shown in FIG.

  The semiconductor device 100 shown in FIGS. 1 and 2 has a structure in which a MOS and an SBD are provided on one semiconductor substrate 30 and are connected in antiparallel. Therefore, as described above, the semiconductor device 100 can be used as a switching element of an inverter circuit as it is. In this case, since the SBD in the semiconductor device 100 has a lower threshold voltage than that of the PN junction diode, it has excellent recovery characteristics and can reduce forward loss.

  In the semiconductor device 100 shown in FIG. 1 and FIG. 2, the MOS and SBD are not separated by separate trenches as in the semiconductor device 90 shown in FIG. It will be arranged adjacent to each partition area R1, R2. Therefore, the semiconductor device 100 shown in FIGS. 1 and 2 can be a small and inexpensive semiconductor device having excellent switching characteristics. Further, by appropriately setting the interval between the plurality of buried trenches T1 and T2 partitioning the inner region in the range of 2 μm to 5 μm, electric field concentration at the bottom of the trench during reverse bias is suppressed, and each partition region R1, R2 It is possible to suppress a decrease in breakdown voltage of the MOS arranged in the circuit.

  Further, in the P-conductivity type layer 33 serving as a MOS channel formation region, lateral diffusion is limited by the buried trenches T1 and T2 as shown in FIG. For this reason, it is not necessary to secure a margin of the lateral diffusion of the P conductivity type layer 33 as a margin, and the device can be miniaturized. In addition, the impurity concentration of the P conductivity type layer 33 can be easily controlled, and the parasitic operation of the parasitic bipolar transistor can be suppressed to prevent the L load surge withstand capability from being lowered.

  As described above, the semiconductor device 100 shown in FIGS. 1 and 2 is a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on one semiconductor substrate 30, In addition to excellent recovery characteristics, forward loss can be reduced, and the transistor withstand voltage and surge resistance are not deteriorated, and a small semiconductor device with excellent switching characteristics can be obtained.

  Note that the plurality of buried trenches T1 and T2 in the semiconductor device 100 are formed in parallel and in a straight line. As a result, the semiconductor device 100 can be easily designed with high withstand voltage, and can be a highly reliable and inexpensive semiconductor device. However, the semiconductor device that can achieve the same effect as the semiconductor device 100 described above is not limited to this. For example, the plurality of buried trenches may have a curved shape, and may have a plurality of lines that do not intersect with each other in the substrate surface. It only has to be formed.

  Further, in the semiconductor device 100, in the plurality of partition regions R1 and R2 in the inner region partitioned by the plurality of buried trenches T1 and T2 shown in FIG. 2, the first partition region is adjacent to the second partition region R2. R1 is arranged. As a result, MOSs are arranged on both sides of the SBD. For this reason, the movement time of carriers between the MOS and the SBD is shortened, and the semiconductor device 100 can be a semiconductor device particularly excellent in switching characteristics. However, the present invention is not limited to this. For example, the plurality of buried trenches may be curved, and the combination of the arrangement of the first partition region R1 in which the MOS is formed and the second partition region R2 in which the SBD is formed is arbitrary. It may be.

  FIG. 3 is a schematic cross-sectional view of the semiconductor device 101 as another example of the semiconductor device. 4 is a schematic plan view showing an example of a plane pattern of the main part of the semiconductor device 101 shown in FIG. 3, and a cross section taken along a dashed line BB in the figure corresponds to FIG. In the semiconductor device 101 shown in FIGS. 3 and 4, the same parts as those of the semiconductor device 100 shown in FIGS. 1 and 2 are denoted by the same reference numerals.

  The semiconductor device 100 shown in FIG. 1 and the semiconductor device 101 shown in FIG. 3 have the same cross-sectional structure, but the connection method of the second buried trench T2 is different. In the semiconductor device 100 of FIG. 1, the second buried trench T2 is connected to the source (S) wiring of the MOS. On the other hand, in the semiconductor device 101 of FIG. 3, the second buried trench T2 is connected to the gate (G) wiring of the MOS.

  Since the polycrystalline silicon in the second buried trench T2 in the semiconductor device of the present invention has a zero potential which is the same potential as the polycrystalline silicon in the first buried trench T1 which is the gate electrode when the MOS is turned off, Connected to wiring. As in the semiconductor device 100 of FIG. 1, when the second buried trench T2 is connected to the MOS source (S) wiring, unnecessary parasitics are applied to the MOS gate as compared with the case where the second buried trench T2 is connected to the gate (G) wiring. No (gate) capacitance is added. For this reason, deterioration of the switching speed of the MOS can be suppressed and switching loss can be reduced, which is preferable.

  On the other hand, when the second buried trench T2 is connected to the same gate (G) wiring of the MOS as the first buried trench T1, the wiring structure is simplified and a smaller semiconductor device can be obtained. For example, in the semiconductor device 101 shown in FIG. 4, the polycrystalline silicon in the first buried trench T1 and the second buried trench T2 is connected to the polycrystalline silicon formed on the semiconductor substrate outside the predetermined internal region. It is connected to the MOS gate (G) wiring through the polycrystalline silicon layer 37b.

  FIG. 5 is a schematic cross-sectional view of the semiconductor device 102 as another example of the semiconductor device. 6 is a schematic plan view showing an example of a plane pattern of the main part of the semiconductor device 102 shown in FIG. 5, and a cross section taken along a dashed line CC in FIG. 5 corresponds to FIG. In the semiconductor device 102 shown in FIGS. 5 and 6, the same reference numerals are given to the same parts as those of the semiconductor device 100 shown in FIGS.

  In the semiconductor device 102 shown in FIGS. 5 and 6, the second buried trench T2 is connected to the source (S) wiring of the MOS as in the semiconductor device 100 shown in FIGS. On the other hand, the semiconductor device 102 shown in FIGS. 5 and 6 is different from the semiconductor device 100 shown in FIGS. 1 and 2 on the surface of the semiconductor substrate 30 in the adjacent first partition region R1 and second partition region R2. An exposed N conductivity type (N +) region 34, a P conductivity type (P) layer 33, a polycrystalline silicon 32 in the second buried trench T2, and an N conductivity type (N−) layer 30a are formed on the semiconductor substrate 30. The first and second metal layers M1, which are source wirings, are commonly connected. For this reason, in the semiconductor device 102, the contact portion is disposed so as to be surrounded by a thick broken line in FIG. 6, thereby connecting to the polycrystalline silicon in the second buried trench T2 like the semiconductor device 100 shown in FIG. There is no need to form the polycrystalline silicon layer 37a.

  Next, a method for further improving the breakdown voltage in the semiconductor devices 100 to 102 of FIGS. 1 to 6 will be described.

  7 and 8 are examples of other semiconductor devices, and are schematic cross-sectional views of the semiconductor devices 103 and 104, respectively. In the semiconductor devices 103 and 104 shown in FIGS. 7 and 8, the same parts as those of the semiconductor device 100 shown in FIG.

  In the semiconductor device 100 of FIG. 1, the insulating films 31 of the buried trenches T1 and T2 are formed to have the same thickness at the bottom of the trench and the side wall of the trench. On the other hand, in the semiconductor device 103 of FIG. 7, in order to improve the breakdown voltage, the insulating film 31a of the buried trenches T1a and T2a is formed so that the bottom of the trench is thicker than the side wall of the trench. . The structure of the buried trenches T1a and T2a in the semiconductor device 103 of FIG. 7 includes, for example, thermal oxidation after forming the trench to form an oxide film having a thickness equal to the bottom and side walls, and then forming an oxide film on the bottom of the trench. It can be formed by depositing.

  In the semiconductor device 100 of FIG. 1, the buried trenches T1 and T2 are formed so that the radius of curvature at the bottom of the trench is equal to the trench radius at the top of the trench. On the other hand, in the semiconductor device 104 of FIG. 8, in order to improve the breakdown voltage, the buried trenches T1b and T2b are formed so that the curvature radius at the bottom of the trench is larger than the trench radius at the top of the trench. The structure of the buried trenches T1b and T2b in the semiconductor device 104 of FIG. 8 is, for example, that isotropic etching is performed without removing reaction products adhering to the trench sidewalls after forming the trenches by anisotropic etching. Can be formed.

  Further, in the semiconductor devices 100 to 102 of FIGS. 1 to 6, the breakdown voltage can be further improved by narrowing the interval between the adjacent buried trenches T1 and T2.

  FIG. 9 to FIG. 11 are schematic plan views showing examples of plane patterns of main parts of the semiconductor devices 100a to 102a, which are examples of other semiconductor devices. In addition, in the semiconductor devices 100a to 102a shown in FIGS. 9 to 11, the same reference numerals are given to the same parts as those of the semiconductor devices 100 to 102 shown in FIGS.

  In the semiconductor devices 100 to 102 shown in FIGS. 2, 4, and 6, the widths of the partition regions R <b> 1 and R <b> 2, that is, the interval between the adjacent linear buried trenches T <b> 1 and T <b> 2 are The first partition region R1 and the second partition region R2 were set substantially equal. On the other hand, in the semiconductor devices 100a to 102a shown in FIGS. 9 to 11, the width w2 of the second partition region R2a is set smaller than the width w1 of the first partition region R1a. As a result, the withstand voltage can be improved as compared with the semiconductor devices 100 to 102 shown in FIGS. 2, 4 and 6, and the second partition region R2a (SBD) is compared with the case where the second partition region R2a (SBD) is not provided. It is possible to further suppress the deterioration of the breakdown voltage due to the insertion arrangement.

  FIGS. 12 to 14 and FIGS. 15 to 17 are schematic plan views showing examples of planar patterns of main parts of the semiconductor devices 100b to 102b and the semiconductor devices 100c to 102c, respectively, as examples of other semiconductor devices. . In the semiconductor devices 100b to 102b shown in FIGS. 12 to 14 and the semiconductor devices 100c to 102c shown in FIGS. 15 to 17, the same parts as those of the semiconductor devices 100 to 102 shown in FIGS. The same symbols are attached.

  In each of the semiconductor devices 100b to 102b shown in FIGS. 12 to 14, each of the semiconductor devices 100b to 102b shown in FIGS. 2, 4, and 6 is adjacent to two semiconductor devices 100 to 102 that define the second partition region R2. For the buried trench T2, a plurality of third buried trenches T3 that connect the neighboring buried trenches T2 in a ladder shape are formed. As a result, the second partition region R2 is partitioned by a plurality of third buried trenches T3 and divided into a plurality of small regions, thereby suppressing the deterioration of the breakdown voltage accompanying the insertion arrangement of the second partition region (SBD) R2. be able to. In order to suppress breakdown voltage degradation, the plurality of small regions are preferably substantially square as shown in FIGS.

  In addition to the suppression of the breakdown voltage degradation, the third buried trench T3 prevents lateral diffusion of the P-conductivity type region 36 on the outer periphery to the second partition region R2, and the polysilicon and the substrate in the buried trench T2. It can be used to expand the connection area with the upper polycrystalline silicon layers 37a and 37b. In the semiconductor devices 100c to 102c shown in FIGS. 15 to 17, the third buried trench T3a formed at the end of the second partition region R2 is connected to the second partition region R2 of the P conductivity type region 36 on the outer periphery. Used to prevent lateral diffusion. Further, in the semiconductor devices 100c and 101c shown in FIGS. 15 and 16, the third buried trench T3b immediately below the polycrystalline silicon layers 37a and 37b on the substrate respectively includes the polycrystalline silicon in the buried trench T2 and the substrate. It is used for expanding the connection area with the upper polycrystalline silicon layers 37a and 37b.

  The semiconductor devices 100 to 104, 100a to 102a, 100b to 102b, and 100c to 102c shown in FIG. 1 to FIG. 17 all use an N conductivity type (N−) semiconductor substrate 30 and are arranged on the main surface side. In the surface layer portion, a P conductivity type (P) layer 33 serving as a MOS channel formation region and an N conductivity type layer 30a for forming an SBD Schottky barrier were disposed. In order to obtain good characteristics regarding the MOS which is a constituent element of the semiconductor devices 100 to 104, 100a to 102a, 100b to 102b, and 100c to 102c, each part of the semiconductor devices 100 to 102 shown in FIGS. The conductivity type structure is preferable. However, the present invention is not limited to this, and may be a semiconductor device in which the conductivity types of the respective regions in the semiconductor devices 100 to 104, 100a to 102a, 100b to 102b, and 100c to 102c are all reversed.

  As shown in the above example, the semiconductor device of the present invention is a semiconductor device in which a vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on a single semiconductor substrate, and has a diode recovery characteristic. In addition to being excellent, the forward loss can be reduced, the breakdown voltage and surge resistance of the transistor are not deteriorated, and the semiconductor device is small and inexpensive with excellent switching characteristics.

  Therefore, the semiconductor device is a semiconductor device used in an inverter circuit configured by a combination of a vertical MOS transistor and a free wheel diode (FWD), and is suitable when the Schottky barrier diode is used as the FWD. It is.

  Further, the semiconductor device is a small semiconductor device and can ensure high breakdown voltage. Therefore, the semiconductor device is suitable as a vehicle-mounted semiconductor device.

1 is a schematic cross-sectional view of a semiconductor device 100 as an example of a semiconductor device according to the present invention. FIG. 2 is a schematic plan view showing an example of a plane pattern of a main part of the semiconductor device 100 shown in FIG. 1, and a cross section taken along a dashed line AA in FIG. FIG. 5 is a schematic cross-sectional view of a semiconductor device 101 as another example of a semiconductor device. FIG. 4 is a schematic plan view showing a planar pattern example of a main part of the semiconductor device 101 shown in FIG. 3, and a cross section taken along a dashed line BB in FIG. FIG. 6 is a schematic cross-sectional view of a semiconductor device 102 as another example of a semiconductor device. FIG. 6 is a schematic plan view showing an example of a planar pattern of a main part of the semiconductor device 102 shown in FIG. 5, and a cross section taken along a dashed line CC in FIG. 5 corresponds to FIG. FIG. 10 is a schematic cross-sectional view of a semiconductor device 103 as another example of the semiconductor device. FIG. 6 is a schematic cross-sectional view of a semiconductor device 104 as another example of the semiconductor device. FIG. 14 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 100a as an example of another semiconductor device. FIG. 10 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 101a as an example of another semiconductor device. FIG. 11 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 102a as an example of another semiconductor device. FIG. 10 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 100b as an example of another semiconductor device. FIG. 10 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 101b as an example of another semiconductor device. FIG. 14 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 102b as an example of another semiconductor device. FIG. 11 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 100c as an example of another semiconductor device. FIG. 14 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 101c as an example of another semiconductor device. FIG. 10 is a schematic plan view showing another example of a planar pattern of the main part of the semiconductor device 102c as an example of another semiconductor device. It is a figure which shows the structure of the conventional semiconductor device, and is typical sectional drawing of the semiconductor device 90. FIG.

Explanation of symbols

90, 100 to 104, 100a to 102a, 100b to 102b, 100c to 102c Semiconductor device 30 Semiconductor substrate T1, T1a, T1b First buried trench T2, T2a, T2b Second buried trench T3, T3a, T3b Third buried trench R1 , R1a First partition region R2, R2a Second partition region 30a N conductivity type (N−) layer 31, 31a Insulating film 32 Polycrystalline silicon 33 P conductivity type (P) layer 34 N conductivity type (N +) region 35 N conductivity Type (N +) layer 36 P conductivity type (P) region 37a, 37b Polycrystalline silicon layer M1 First metal layer M2 Second metal layer

Claims (18)

A vertical MOS transistor having a trench gate structure and a Schottky barrier diode are provided on a semiconductor substrate of the first conductivity type,
In the surface layer portion on the main surface side of the semiconductor substrate, a buried trench in which polycrystalline silicon is buried via an insulating film is formed in a plurality of lines that do not intersect with each other in the substrate surface,
A predetermined region in the surface layer portion on the main surface side of the semiconductor substrate within the substrate surface is partitioned by the plurality of buried trenches, and is divided into a plurality of partition regions,
In one of the plurality of partition regions, a second conductivity type layer serving as a channel formation region of the vertical MOS transistor is formed in a surface layer portion on the main surface side of the semiconductor substrate in one of the first partition regions. ,
Among the plurality of buried trenches, the polycrystal in one first buried trench adjacent to the first conductivity type region which is the source region of the vertical MOS transistor formed in the surface layer portion of the second conductivity type layer Silicon is connected to the gate wiring of the vertical MOS transistor,
Of the plurality of buried trenches, polycrystalline silicon in the other second buried trench not adjacent to the first conductivity type region is connected to the source wiring or gate wiring of the vertical MOS transistor,
Among the plurality of partition regions, in the other second partition region, the first conductive type layer made of the semiconductor substrate is exposed on the surface on the main surface side and connected to the source wiring of the vertical MOS transistor. A semiconductor device in which a Schottky barrier of the Schottky barrier diode is formed. Above the main surface side of the semiconductor substrate,
A first metal layer that is a source wiring of the vertical MOS transistor is disposed so as to cover the predetermined region,
2. The semiconductor device according to claim 1, wherein a second metal layer which is a gate wiring of the vertical MOS transistor is formed so as to surround the first metal layer.   3. The semiconductor device according to claim 1, wherein the polycrystalline silicon in the second buried trench is connected to a source wiring of the vertical MOS transistor. The polycrystalline silicon in the second buried trench is
4. The source of the vertical MOS transistor is connected to the vertical MOS transistor via a polycrystalline silicon layer connected to the polycrystalline silicon formed on the semiconductor substrate outside the predetermined region. A semiconductor device according to 1. In the adjacent first partition region and second partition region,
The first conductivity type region exposed on the surface of the semiconductor substrate, the second conductivity type layer, the polycrystalline silicon in the second buried trench, and the first conductivity type layer are commonly connected by a metal layer formed on the semiconductor substrate. The semiconductor device according to claim 3, wherein the semiconductor device is formed. The polycrystalline silicon in the first buried trench and the second buried trench is
2. The gate electrode of the vertical MOS transistor is connected to a gate electrode of the vertical MOS transistor through a polycrystalline silicon layer connected to the polycrystalline silicon formed on the semiconductor substrate outside the predetermined region. Or the semiconductor device according to 2; In the plurality of partition regions,
The semiconductor device according to claim 1, wherein the first partition region is disposed on both sides of the second partition region.   The semiconductor device according to claim 1, wherein the line shape is a straight line shape.   9. The semiconductor device according to claim 8, wherein the plurality of buried trenches are formed in parallel to each other.   The semiconductor device according to claim 9, wherein the first partition region and the second partition region are all set equal in width.   The semiconductor device according to claim 9, wherein a width of the second partition region is set smaller than a width of the first partition region.   For two adjacent buried trenches defining the second partition region, a plurality of third buried trenches connecting the adjacent buried trenches in a ladder shape are formed, and the second partition region is The semiconductor device according to claim 11, wherein the semiconductor device is divided into a plurality of small regions by being partitioned by the plurality of third buried trenches.   The semiconductor device according to claim 12, wherein the small region has a substantially square shape.   14. The semiconductor device according to claim 1, wherein the insulating film of the buried trench has a trench bottom formed thicker than a trench sidewall.   15. The semiconductor device according to claim 1, wherein the buried trench has a radius of curvature at the bottom of the trench that is larger than a trench radius at the top of the trench.   16. The semiconductor device according to claim 1, wherein the first conductivity type is an N conductivity type, and the second conductivity type is a P conductivity type. The semiconductor device is a semiconductor device used for an inverter circuit,
The semiconductor device according to claim 1, wherein the Schottky barrier diode is used as a free wheel diode.   The semiconductor device according to claim 1, wherein the semiconductor device is a vehicle-mounted semiconductor device.

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