Schottky rectifier and manufacturing method thereof

Abstract

The invention provides a Schottky rectifier and a manufacturing method thereof. The Schottky rectifier device may be configured to provide multiple types of surge current protection. Different current magnitudes and characteristics may relate to different types of inrush current events. The described Schottky rectifier structures provide surge current protection in various types of surge current scenarios, while minimizing or reducing the instances that a solution in one environment undesirably mitigates the effects of the solution in another environment.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980094692.1, entitled "Schottky Rectifier with Surge Current Stability and Method of Manufacturing the Same", which is the national stage entry of PCT International Patent Application PCT / US2019 / 068946 with a filing date of December 30, 2019. Technical Field

[0002] This application relates to Schottky rectifier semiconductor devices. Background Art

[0003] Silicon Carbide (SiC) devices, especially SiC high-power devices, offer advantages such as high switching speed and low power loss. Examples of efficient SiC power devices include (but are not limited to) rectifiers, Field-Effect Transistors (FETs), and Bipolar Junction Transistors (BJTs).

[0004] A Schottky rectifier is a type of diode with a metal-semiconductor junction. As is well known, Schottky rectifiers have a low forward voltage drop and a fast switching speed. Thus, SiC Schottky rectifiers offer the advantages of general SiC devices, as well as the advantages of traditional (e.g., silicon-based) Schottky rectifiers.

[0005] Schottky rectifiers, including SiC Schottky rectifiers, are often used in, for example, power conversion systems. In these and other settings, high current surges can be problematic. For example, in a power conversion system, a load short circuit situation can result in a high surge current. The rectifier current cannot be interrupted during a surge current event, so the rectifier should be able to withstand a surge current event without failure. Thus, Schottky rectifiers are often subject to various reliability or stability requirements related to withstanding forward current surges.

[0006] Prior art methods are used to improve the surge current reliability and stability of Schottky rectifiers. For example, it can include a merged p-n diode with a Schottky rectifier (which can be referred to as a "MPS" or Junction-Blocked (JBS) rectifier). Such MPS / JBS devices can be further improved in terms of withstanding surge current events, for example, by adding a relatively wide p-body for increasing the forward voltage drop of the Schottky rectifier at certain positions during a surge current event. However, these existing methods either cannot achieve the desired level of surge current reliability or stability, or have other drawbacks, such as consuming too much device area. Summary of the Invention

[0007] In the following disclosure, example embodiments of a Schottky rectifier are described that provide surge current protection against multiple types of surge current events. For example, one type of surge current event may be relatively short, while a second type may be relatively long (where the length of the surge current event can be defined in terms of, for example, time units or relevant line cycle units). Different current magnitudes and characteristics may be associated with different types of surge current events. The described Schottky rectifier structure provides surge current protection in multiple types of surge current scenarios while minimizing or reducing the situation where a solution in one environment undesirably mitigates the effectiveness of the solution in another environment.

[0008] According to one general aspect, a Schottky rectifier device includes a silicon carbide (SiC) layer, a channel region of a first conductivity type formed on the SiC layer, and a metal contact formed on the channel region. The Schottky rectifier device further includes a multi-layer body of a second conductivity type that is formed within the channel region and extends in the direction of the SiC layer from the metal contact. The multi-layer body includes a first layer adjacent to the metal contact and having a first doping concentration, a second layer adjacent to the first layer and having a second doping concentration less than the first doping concentration, and a third layer adjacent to the second layer and having a third doping concentration less than the second doping concentration.

[0009] According to another general aspect, a method for manufacturing a Schottky rectifier device includes forming a silicon carbide (SiC) substrate and forming an epitaxial layer of a first conductivity type on the SiC substrate. The method includes forming a mask layer on the epitaxial layer, performing ion implantation of a second conductivity type donor through the mask layer to form a part of a charge-balanced body, and removing the mask layer. The method further includes repeating the formation of the epitaxial layer and the mask ion implantation until the charge-balanced body reaches a specified thickness; forming an implantation layer on the charge-balanced body, the implantation layer having a doping concentration of a second conductivity type that is higher than the doping concentration of the charge-balanced body; forming a contact layer on the implantation layer; and forming a metal contact on the contact layer and the epitaxial layer.

[0010] According to another general aspect, a Schottky rectifier device includes a silicon carbide (SiC) layer, a channel region of a first conductivity type formed on the SiC layer, and a metal contact formed on the channel region. The Schottky rectifier device includes a multi-layer body of a second conductivity type that is formed within the channel region and extends in the direction of the SiC layer from the metal contact. The multi-layer body includes a tunnel contact layer adjacent to the metal contact, an implantation layer adjacent to the first layer, and a deep layer adjacent to the second layer, where the multi-layer body extends at least 30% of the distance between the metal contact and the SiC layer.

[0011] The accompanying drawings and the following description give details of one or more embodiments. Other features are apparent from the specification, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic cross-sectional view of a SiC Schottky rectifier having inrush current stability.

[0013] Figure 2A is Figure 1 a schematic cross-sectional view of an exemplary embodiment of a SiC Schottky rectifier.

[0014] Figure 2B is Figure 2A a first top view of an exemplary embodiment.

[0015] Figure 2C is Figure 2A a second top view of an exemplary embodiment.

[0016] Figure 3 is a graph showing Figure 1 and Figures 2A to 2C a first current-voltage curve of a Schottky rectifier.

[0017] Figure 4 is a graph showing Figure 1 and Figures 2A to 2C a second current-voltage curve of a Schottky rectifier.

[0018] Figure 5 is a graph of the electron concentration curve along a vertical device cross-section of a Schottky rectifier of Figure 1 and Figures 2A to 2C a Schottky rectifier.

[0019] Figure 6 is Figure 1 a cross-sectional view of a rectifier unit cell of Figure 1 with a dedicated ohmic contact to a multi-layer p-body of

[0020] Figures 7A to 7J shows the operation for forming one or more of the Figures 1 to 2C Schottky rectifier devices.

[0021] Figure 8 is a schematic diagram showing a room-temperature secondary ion mass spectrometry (SIMS) chart for Al channeling implantation into SiC.

[0022] Figure 9 is for Figure 1 and Figure 2ASchematic diagrams of the channeled phosphorus with donor doping in the drift region and the diagram of random implantation. Detailed Description

[0023] Figure 1 FIG. 6 is a schematic cross-sectional view of a SiC Schottky rectifier 100 having surge current stability. As described above, the Schottky rectifier 100 can be configured to provide various types of surge current protection. For example, referring to the following description, the maximum surge current I FM caused by, for example, a load short circuit typically has a time of about 10 μs, and a similar measurement time can be used to test I FM (usually the standard is 10 μs). Another surge current stability requirement is, for example, the ability to maintain a single-pulse maximum surge current I FSM for half a cycle of the line period, which can be about 10 ms for typical power applications. As described herein, the SiC Schottky rectifier 100 provides surge current stability for I FM and I FSM surge current events.

[0024] In Figure 1 , the SiC Schottky rectifier 100 is shown to include an n-type channel region 102 parallel to the multi-layer p-body 110. In the example of Figure 1 , the multi-layer p-body 110 includes layers 111, 112, and 113. As described in more detail below, during a surge current event, the multi-layer p-body 110 provides surge current stability with respect to the n-type channel 102. For example, the multi-layer p-body 110 can include an implanted layer 112 that is constructed and doped to provide a high injection efficiency. The multi-layer p-body 110 can include a deep p-body 113 that extends parallel to the n-type channel and, in some embodiments, extends completely along the remaining length of the n-type channel 102 to contact the substrate 101 of the Schottky rectifier.

[0025] During a relatively long surge current event (e.g., I FSM ), the multi-layer p-body 110 can provide surge current protection by, for example, causing an electron current to flow along the n-type Schottky channel 102. Causing the electron current to flow along the n-type Schottky channel 102 generates a high enough voltage drop to turn on the p-n diode formed by the multi-layer p-body 110 and the n-type channel 102. More specifically, compared to a conventional MPS / JBS Schottky rectifier, the structure of the multi-layer p-body 110 reduces the voltage required to turn on minority carrier injection at the p-n diode.

[0026] For example, in a conventional MPS / JBS Schottky rectifier, a 10 ms surge current event may require withstanding a surge current of up to 4X to 10X the rated current of the MPS / JBS Schottky rectifier. However, during the transition from the normal current level to the surge current level, due to the relatively low on-voltage (about 1V) of the Schottky rectifier compared to that of the adjacent p-n diode (about 3V), a short circuit of the p-n diode may occur in the vertical Schottky rectifier channel. This short circuit effect prevents the p-n diode from turning on the injection mode at a relatively low forward bias and reduces the surge current stability of such a conventional MPS / JBS Schottky rectifier.

[0027] In contrast, the multi-layer p-body 110 includes many characteristics and features that are superior to those of a conventional MPS / JBS Schottky rectifier. For example, the injection layer 112 is configured to provide high injection efficiency, and together with the relative length of the deep p-body 113, the multi-layer p-body 110 provides a super junction effect for charge balancing of the n-channel 102, where such charge balancing occurs during reverse bias conditions. During a forward bias surge current event such as a relatively long surge current event (e.g., I FSM ), the forward voltage drop of the p-n diode 110 / 102 is reduced relative to the on-voltage of the Schottky rectifier 100, which alleviates or eliminates the undesirable short circuit effect of the vertical Schottky channel 102 on the p-n diode 110 / 102.

[0028] In addition, the multi-layer p-body 110 may include, for example, a tunnel contact layer 111 in contact with the injection layer 112. Thus, as shown, the injection layer 112 connects the tunnel contact layer 111 and the deep p-body layer 113.

[0029] During a relatively short surge current event (e.g., I FM ), the tunnel contact layer 111 provides a reduced voltage drop. In other words, the tunnel contact layer 111 provides surge current stability for scenarios of short current pulses with high current density.

[0030] In an embodiment where the injection layer 112 connects the tunnel contact layer 111 and the deep p-body layer 113, the injection layer 112 can be doped and otherwise configured to prevent electrons from recombining at the tunnel contact layer 111 as described below. In the case of a relatively long surge current event (e.g., I FSM ), if this recombination is not prevented, it may alleviate or be detrimental to the surge current stability.

[0031] Charge balancing can occur as Figure 1within the charge balance region schematically shown as region 109. Charge balance is generally not achieved in regions above or below region 109 because the acceptor or donor concentrations outside region 109 are very high.

[0032] In Figure 1 a Schottky rectifier 100 is formed using an n-doped epitaxial layer that forms a drift region 102 on top of an n+ substrate 101. A multi-layer p-body (represented by multi-layer p-body 110) penetrates Lpbody in depth, where Lpbody is between approximately 30% and 100% of, for example, the drift region thickness Ldrift. As shown, the width of the multi-layer p-body 110 is Wp. The period of the unit cell is Wcell, the value of which should preferably be less than the drift region length, i.e., Wcell < Ldrift.

[0033] Figure 1 The unit cell in

[0034] can be provided with a metal layer 150 that forms a Schottky contact with the n-region 102 having a desired barrier height. An ohmic contact 160 is provided at the bottom of the n+ substrate 101.

[0034] Regarding doping, in some example embodiments, degenerate acceptor doping can be provided to the tunnel contact layer 111 to, for example, 10 20 cm -3 or a higher concentration. In other words, as described above, the heavily doped p-body portion (tunnel contact layer) 111 provides a tunnel contact to the top metal 150, which prevents excessive voltage drop at the interface between the metal 150 and the layer 111 at very high current densities, which corresponds to the mode of the IFM test. A near-surface acceptor concentration higher than about 10 20 cm -3 can be used to ensure a low forward voltage drop of the multi-layer p-body 110 at the metal contact 150 to the tunnel contact layer 111.

[0035] In a more detailed example, under conditions corresponding to the IFM test, the average current density through the 650V Schottky rectifier active region may be close to 40 kA / cm 2 . During a 10 microsecond surge current event, the local current density through the multi-layer p-body 110 can be, for example, twice the average value, e.g., 80000 A / cm 2 . A high-quality ohmic contact with p-type SiC has a specific resistance of approximately 10 -5 to 3x10 -5 Ohm cm 2 for optimizing the metallization scheme. At a current density of about 100 kA / cm 2When this occurs, the contact resistance can cause a parasitic voltage drop in the p-type body 110 that far exceeds 1 volt. However, in many cases, the ohmic contact process is simplified for manufacturing considerations, and the specific resistance of such a simplified contact can be 10 -4 Ohm cm 2 or higher. A high near-surface acceptor concentration above 1x10 20 / cm 3 will facilitate direct tunneling at the contact-semiconductor interface 150 / 111 and will prevent the formation of an excessive voltage drop at this interface.

[0036] In an example embodiment, an acceptor dose above approximately 2x10 14 cm -2 is provided for the injection layer 112, where the acceptor doping is below approximately 2x10 19 cm -3 . As described below, in an example embodiment, a relatively low level of approximately 1x10 18 cm- 3 can be maintained to ensure an acceptable level of injection efficiency.

[0037] In an example embodiment, the multi-layer p-body 110 penetrates into the drift region 102 towards the substrate 101 to at least 30% of the depth. In an example embodiment, the ratio of Lpbody to Ldrift may be between 0.7 and 0.9. The acceptor doping of the deep p-body 113 can be between approximately 2x10 16 cm -3 and 1x10 18 cm -3 . In some example embodiments, the acceptor dose in the deep p-body 113 is selected such that, prior to the avalanche breakdown point, it is depleted to at least 50% of its length under reverse bias.

[0038] As described above, in an example embodiment, the injection layer 112 can be designed and configured to provide high injection efficiency. Specifically, the injection layer 112 can be designed to have a high effective Gummel number.

[0039] In this regard, the regular Gummel number can be understood as representing the integral of the doping concentration over the layer thickness (e.g., the carrier path length). The Gummel number indicates the injection efficiency of the doped layer and can, in some cases, particularly for relatively low doping levels, provide a reasonable approximation of this injection efficiency.

[0040] However, as the doping level increases, the effect indicated by the Gummel number decreases from the level that would be expected based on the actual dose concentration. Specifically, as the doping level increases for a given path length, various physical effects contribute to this reduction. In particular, the bandgap narrowing known to occur in heavily doped regions due to many-body quantum effects can facilitate minority carrier injection into the heavily doped material while suppressing carrier injection from the heavily doped material.

[0041] For a p-type layer with a box-shaped acceptor profile, the resulting effective Gummel number "NGeff" is NG eff = Q a * exp(-dEg / kT), where Q a is the ionized acceptor dose, dEg is the bandgap reduction due to heavy doping, k is the Boltzmann constant, and T is the Kelvin temperature. Taking this bandgap narrowing into account, in an exemplary embodiment, the upper doping limit of the injection layer 112 can be set to approximately 2x10 19 cm -3 . In an exemplary embodiment, to optimize the injection efficiency, a lower doping may be preferred because significant bandgap narrowing is known to occur starting from a lower doping concentration of approximately 2 - 3x10 18 cm -3 .

[0042] Thus, the doping concentration of the connection layer 112 can be understood to have a value associated with the peak injection efficiency rating (e.g., 2x10 18 to 2x10 19 cm -3 ), below which the concentration is insufficient and above which the bandgap narrowing becomes increasingly detrimental. Thus, the effective Gummel number of the connection layer 112 can be maintained at a level of, for example, 2x10 14 or higher.

[0043] Meanwhile, as described above, the preferred doping concentration of the tunnel contact layer 111 is generally higher than the peak injection efficiency value of the injection layer 112, e.g., at 1x10 20 cm -3 or above. Thus, it can be observed that in some embodiments, attempting to combine regions 111 and 112 may be undesirable, for example, in the case of a charge-balanced Schottky rectifier that requires a high surge current.

[0044] Furthermore, the high (effective) Gummel number of the injection layer 112 prevents electron recombination at the top contact 150. As described above, this recombination can mitigate the effect of the tunnel contact layer 111 during a short-term I FM surge current event.

[0045] Similarly as described above, the Schottky rectifier 100 is provided with a charge balance between acceptors in the deep p-body 113 and donors in the n-channel 102. This charge balance effectively means that within region 109, the total charge of uncompensated acceptors and donors in the corresponding p-type and n-type materials exists in substantially similar numbers. Otherwise, an excessive charge difference in the region may deteriorate the reverse blocking performance.

[0046] More specifically, in an exemplary embodiment, the average lateral donor charge Qd of uncompensated donors in the charge balance channel 102 can be defined as the total number of uncompensated donors in region 109 divided by the active device area. The acceptor charge Qa can be defined as the total number of uncompensated acceptors within the charge balance region 109 divided by the active device area. In some embodiments, the donor charge Qd and the acceptor charge Qa can have a deviation (e.g., charge imbalance) of about 1x10 13 cm -2 or lower. In some embodiments, a charge imbalance greater than 1x10 13 cm -2 in the rectifier 100 may result in premature avalanche breakdown (e.g., avalanche breakdown below the desired blocking voltage).

[0047] Figure 2A is Figure 1 a schematic cross-sectional view of an exemplary embodiment of a SiC Schottky rectifier. As described above, and with reference to Figures 2A to 2C described, Figure 1 the Schottky rectifier 100 in

[0048] can be defined as a unit cell of a larger circuit such as a multi-rectifier circuit, and this unit cell can be sized and spaced relative to each other and other circuit elements in a manner that provides additional surge current protection as well as other features and advantages.

[0048] More specifically, with regard to Figure 2A Figure 1 the SiC charge balance Schottky rectifier 100 in Figure 1 benefits from additional design requirements related to the lateral component of the electric field. For example, the lateral electric field may undesirably increase with an increase in the width and / or donor concentration of the n-channel (e.g., Figure 1 the n-channel 102 in

[0049] ), which may lead to premature breakdown.

[0050] To avoid such early breakdown, the rectifier device 200 includes an active region 270, which is surrounded by a p-n diode edge 215 and a terminal region 280. The terminal region 280 prevents excessive electric fields and early breakdown at the periphery of the diode.

[0050] The active region 270 is formed by, as Figure 1The unit cell array shown is formed. In FIG. 2, the corresponding cell includes a multi-layer p-body that includes degenerate doped regions providing a tunnel contact layer 211, an implanted p-body 212, and a deep p-body 213, and an adjacent n-channel 202. The array forming the active region can be one-dimensional (a linear array of p-type and n-type stripes), or a two-dimensional array with a mesh structure.

[0051] The diode edge 215 is formed by a continuous p-body surrounding the unit cell array. The top portion of the p-n diode edge 215 is preferably provided with heavy doping, and the doping profile may include a top region having the same doping and thickness as regions 212 and 213. An array of deep p-bodies 223a, 223b, 223c is also formed, which may have similar dimensions and doping as the deep p-body 213. The deep p-bodies 223a, 223b, 223c are preferably distributed on the diode edge with the same period as the period of the p-body 213 in the active region to maintain charge balance. This design can provide an avalanche breakdown voltage in the edge region, which is preferably equal to or greater than the avalanche breakdown voltage of the active region. Although three deep p-bodies 223a, 223b, 223c are shown in FIG. 2, example embodiments may use a greater number of such deep p-bodies, depending on the desired width of the p-type edge 215.

[0052] The metal contact 250 covers the unit cell array and at least the inner portion of the p-n diode edge 215. The ohmic contact 260 is provided on the back surface of the substrate.

[0053] A junction termination (JT) region 280 is provided outside the p-n diode edge 215 to block or mitigate the electric field that accumulates at the periphery of the device. Different strategies can be applied to achieve this goal. In an example embodiment, for example Figure 2A , an array of deep p-bodies 233a-233e surrounding the p-n diode edge 215 can be provided. Although five deep p-bodies 233a to 233e are shown in Figure 2A , the total number of such p-bodies can be greater. A passivation dielectric can be provided on top of the SiC in the junction termination region 280, and the dielectric can be silicon dioxide, silicon nitride, polyimide, or a combination thereof.

[0054] The average acceptor dose per unit area in the deep p-bodies 233a - 233e can be approximately equal to the acceptor dose in the p-n diode edge region 215 of the inner part of the junction termination region 280. The average acceptor dose of the junction termination region 280 can be defined in a similar manner as the active cell, for example, defined as the total amount of acceptors in the deep p-bodies 233a - 233e divided by the area of a unit cell. More specifically, the average acceptor dose near the p-body 233d can be defined by selecting a pseudo unit cell 239d that extends laterally halfway to the centroid of the adjacent p-body. Then, the average donor / acceptor dose near the p-body 233d can be defined as the total amount of the relevant dopants contained in 239d divided by the area of the element 239d. The same definition will apply to the elements 233a, 233b, and 233c. The width of the outermost cell of the junction termination can be the same as its nearest neighbor.

[0055] The average acceptor dose can gradually decrease as the distance from the p-n diode edge 215 increases. For example, as Figure 2A shown, the width of each deep p-body 233a - 233e can be decreased. A characteristic length Ljt can be defined to characterize the variation of the average acceptor dose. Thus, Ljt can be defined as the distance at which the average acceptor dose drops to 1 / 3 of its peak value. The characteristic length Ljt should preferably be at least 3 times the total thickness of the drift region.

[0056] In one aspect, the junction termination region 280 can be provided with an interconnected, continuous, shallow, low-doped acceptor junction termination body 235, interconnecting all the p-bodies 233a - 233e and the p-n diode edge 215. Such a continuous low-doped JT p-body 235 can be provided to minimize the voltage drop between adjacent p-bodies during the switching transients of the rectifier device.

[0057] The acceptor dose in the region 235 can be, for example, between approximately 20% and 70% of a characteristic dose Qchar, where Qchar = ε*E cr / q, where E cr is the critical field of SiC for the required breakdown voltage, ε is the absolute dielectric constant of SiC, and q is the electron charge. The characteristic charge Qchar is the charge required to generate the electric field E cr where E cr is the avalanche breakdown field in SiC at the electrodes of a one-dimensional rectifying diode. Thus, before reaching the avalanche breakdown voltage, the acceptor dose in the interconnected body 235 should ensure that this region is fully depleted. Example values of E cr in 4H SiC are between 2 MV / cm and 3 MV / cm, depending on the rated voltage of the diode.

[0058] In an exemplary embodiment, the interconnecting terminal p-body 235 may extend laterally beyond the position of the last deep p-body 223c by a certain distance. The extension distance should preferably exceed the drift layer thickness. In this way, the extended p-body 235 will further reduce the electric field concentration at the deep b-body.

[0059] In an exemplary embodiment, the unit cell deep p-body 213 may extend through the entire or almost the entire depth of the drift region such that Lpbody is approximately equal to Ldrift. As shown and described below, regarding Figure 3 , these conditions are suitable for achieving the lowest on-state voltage of the injection.

[0060] Figure 2B is Figure 2A a first top view of an exemplary embodiment of. In Figure 2B a top view of the p-n diode edge region 215 is shown. The region 215 shows the continuous p-body of the junction termination region 280, while the region 235 is the continuous lightly doped p-body. The outer edge of the metal contact 250 completely overlaps at least a portion of the active region and the p-n diode edge 935.

[0061] Figure 2C is Figure 2A a second top view of an exemplary embodiment of. More specifically, Figure 2C shows the top view configuration of the deep charge balancing p-body 213 relative to other device regions, where the footprint of the p-body 213 is shown with hatching. In this embodiment, the charge balancing p-bodies 213 of the active region form a linear array.

[0062] The p-bodies 223x below the p-n diode edge may form a concentric linear array. The inner and outer edges of the p-n diode edge are shown by lines 215i and 215o respectively. A concentric linear array 233x of deep p-bodies is also formed in the junction termination region 280, whose outer edge is represented by the line 235o. As described above regarding Figure 2A , the average charge of the deep p-bodies 233x in the terminal region 280 gradually decreases as the distance from the p-n diode edge 215 increases.

[0063] Figure 2C shows only one of the many possible configurations of the deep p-bodies. For example, the deep p-bodies 213 may form a concentric pattern of the same type as the p-bodies 223x and 233x. The p-bodies may also be a two-dimensional network array of p-type islands, which may represent a two-dimensional hexagonal lattice.

[0064] Figure 3 is a view showing Figure 1 and Figures 2A to 2CGraph of the first current-voltage curve of a Schottky diode rectifier. More specifically, Figure 3 Shows an example result 302 of a TCAD simulation of a 650V Schottky rectifier with a deep p-body doping of 5x10 16 cm -3 where the deep p-body extends into the substrate.

[0065] For comparison, simulations of a reference Schottky rectifier without a deep P-body were also performed, as shown by the IV curve 304. As can be observed from the kink or turn in each of the curves 302, 304, both rectifiers undergo injection, where the start of injection is regarded as the kink of the I-V curve.

[0066] It can be observed that the Schottky rectifier represented by curve 302 enters injection at a much lower voltage than the reference rectifier device without a deep p-body 113 / 213. This is a significant advantage from the perspective of device reliability, as such a rectifier has a lower forward voltage drop and is capable of withstanding higher surge currents without being damaged. The simulation used a temperature of 250C because surge events can cause the diode to overheat severely, and its temperature is typically higher than the standard operating junction temperature.

[0067] Figure 4 Is a graph showing the Figure 1 and Figures 2A to 2C second current-voltage curve of a Schottky diode rectifier. In Figure 4 the forward current IF is shown against the forward voltage VF for the Figure 1 Schottky rectifier in Figure 1 where the multi-layer p-body 110 propagates downwards about half the way into the n-type substrate 101. The deep p-body 113 has a net acceptor doping of 8x10 16 . As with Figure 3 a reference curve 404 of a Schottky rectifier without a multi-layer p-body is shown in Figure 4 .

[0068] Comparing Figure 4 the curves 402, 404 plotted in Figure 1 it can be observed that the Figure 5 Schottky rectifier has a distinct reliability / stability advantage compared to a conventional MPS / JBS device with a shallow p-body. This effect is illustrated and explained in more detail in Figure 5 which shows the electron distribution (502) along the center of the n-channel and the electron distribution (504) through the center of the p-body. From Figure 5 this it can be seen that strong electron injection occurs in both the n-channel and the P-body, where electrons are minority carriers.

[0069] Figure 6 is Figure 1 a cross-sectional view of a rectifier unit cell thereof having a dedicated ohmic contact 640 with a multi-layer p-body 611 / 612 / 613. More specifically, Figure 6 a rectifier device with surge capability having a deep p-body 611 / 612 / 613 in is provided with a dedicated ohmic contact 640 with a degenerate doped sub-contact p-type region forming a tunnel contact layer 611.

[0070] Meanwhile, the ohmic contact 610 with the n-type substrate 601 is illustrated as region 660, and the solder metal stack is represented as region 670. The solder metal stack 670 can be, for example, Ti / Ni / Ag commonly used in power devices. The back contact 610 can be thermally annealed or laser-annealed Ni. In an exemplary embodiment, the back contact 610 can be formed by laser-induced silicidation of a Ni / Ti stack. The upper-side ohmic contact 640 can be, for example, a nickel silicide layer, where the silicide is formed by sintering Ni into SiC at a temperature between approximately 700°C and 950°C.

[0071] The typical resistivity value of the NiSi ohmic contact with SiC is about 0.1 mOhm*cm 2 , which is generally too high to withstand a high surge current of, for example, about 20 kA / cm 2 - 100 kA / cm 2 through the p-body 611 / 612 / 613. However, due to the aforementioned tunneling effect, when maintaining the degenerate doping level in the aforementioned region 611, the voltage drop at the 640-611 interface will be a relatively low value, such as a few tenths of a volt.

[0072] Figures 7A to 7J shows the first to tenth operations for forming Figures 1 to 2C a Schottky rectifier device according to an exemplary embodiment. In Figures 7A to 7J , a device with surge current capability having a deep p-body is formed using a sequential cycle of ion implantation and epitaxial regrowth. In some embodiments, donors for the n-channel layer can be provided by doping during epitaxial layer growth, while in other embodiments, implant doping can be used, especially in cases where relatively higher doping precision is required. Figures 1 to 2C In FIG. 7a, fabrication can start from a 4H SiC substrate 701. In FIG. 7b, a desired doped n-type epitaxial layer 702a is provided. In

[0073] FIG. 7c, Figure 7CIn [reference], the epitaxial layer 702a is blanket-implanted with donor ions 7020, which may be, for example, nitrogen, phosphorus, As, or Sb. Implanting the donor 7020 forms the lower part of the drift region channel 702 (e.g., similar to Figure 1 and Figure 2A the channels 102 and 202 in [[reference]]).

[0074] In Figure 7D a mask layer 7131 is deposited from photoresist or other suitable mask material, such as silicon dioxide, silicon nitride, or tungsten. The mask layer 7131 is patterned, and acceptor ions 7130 are implanted. In an exemplary embodiment, the acceptor dopant may be Al. However, the deep p-bodies 113 / 213 / 713 may also employ Ga or B, or a combination thereof with Al.

[0075] In Figure 7E after removing the mask, the crystal is regrown with an additional epitaxial layer 7021a, as shown in Figure 7F The implantation stages 7C to 7F may be repeated to gradually increase the thickness of the charge balance regions 702 and 713, as shown in Figure 7G and 7H respectively.

[0076] It should be understood that the deep p-bodies of the p-type edge of the diode (e.g., the regions 223a - 223c in [[reference]]) and the deep p-bodies of the terminal regions (regions 233a - 233c) may be formed simultaneously with the formation of the deep p-body regions of the active region cells 213 (corresponding to 713 in [[reference]]). These regions are omitted in Figure 2A and only the formation of the active structure is shown. However, their manufacturing processes may use the same or similar stages. Similarly, alignment marks may be formed in regions outside the device locations on the wafer such that the marks are not explicitly shown in Figures 7D - 7H either. Figures 7A to 7J In Figures 7A to 7J As shown in Figures 7A to 7J the regions 711 and 712 may be implanted with doping levels corresponding to the similar regions 111 / 211 and 112 / 212 respectively. Device fabrication may continue with the implantation of the junction termination region 235, which is not shown in

[0077] As Figure 7I shown, the fabrication may further include high-temperature annealing to activate the implanted dopants, and the formation of metal contacts 750 and 770 on the top and bottom of the wafer respectively. Figures 7A to 7J As shown, the fabrication may further include high-temperature annealing to activate the implanted dopants, and the formation of metal contacts 750 and 770 on the top and bottom of the wafer respectively.

[0078] In additional or alternative embodiments, the Schottky rectifier device with surge capability described herein having a deep p-body 113 / 213 / 713 can be formed using ion implantation and subsequent acceptor dopant annealing. The deep p-body 113 / 213 / 713 can be formed by acceptor ion implantation using a high-energy ion implanter at an acceleration voltage, for example, between approximately 1 MV and 5 MV. The ion implantation annealing can be performed at a temperature between approximately 1500°C and 1800°C in argon.

[0079] In some embodiments, a carbon coating can be disposed on the upper surface of the SiC wafer prior to high-temperature annealing to avoid roughening of the SiC surface. The carbon coating can be removed after high-temperature annealing using oxygen plasma, by annealing in an oxygen environment, or a combination of both.

[0080] In yet another exemplary embodiment, channeled room-temperature Al ion implantation of the deep p-body 113 / 213 can be utilized. For example, the channeled implantation can be performed along the

[0001] SiC crystal orientation, which is perpendicular to the substrate (0001) SiC crystal plane. For the (0001) substrate crystal plane, the surface of the epitaxial SiC crystal is typically tilted by approximately a few degrees, which means that the ion beam must be tilted at an equal angle in order to align with the

[0001] crystal orientation.

[0081] Alignment of the Al beam to the

[0001] crystal orientation can be performed with high precision, for example, within better than 0.5 degrees, or with a precision within 0.01 degrees to 0.2 degrees. Compared to so-called random implantation, channeled Al implantation penetrates deeper into the SiC. Random implantation is a general name for ion implantation that deviates from a low-index crystal orientation by more than approximately 1.5 degrees to 2 degrees.

[0082] Figure 8 is a schematic diagram of a secondary ion mass spectrometry (SIMS) chart 802 of channeled Al implantation into SiC at room temperature along the

[0001] 4H SiC crystal orientation at a dose of 1 x 10 13 cm -3 and an ion energy of 450 keV. In contrast, for random implantation, achieving the same ion penetration may disadvantageously require an acceleration energy of several MeV. However, using deeper channeled implantation as described above and as shown in Figure 8 can minimize the number of implantation and regrowth cycles while avoiding the need for an implantation tool capable of MeV ion acceleration. Room-temperature conditions are preferred for channeled implantation because the implantation depth decreases with increasing crystal temperature.

[0083] In an example embodiment, thermal implantation can be used to form regions 111 and 112. Attempting to implant the tunnel contact layers 111 / 211 / 711 at room temperature may cause the SiC material to amorphize. Additionally, unlike silicon, fully amorphous SiC cannot fully recover its structure after annealing. Therefore, amorphization during the ion implantation process can be avoided, for example, by using an elevated substrate temperature during implantation, such as between approximately 200°C and 700°C.

[0084] In an additional embodiment, a low-doped, deep p-body 113 / 213 channeling room temperature implantation is performed in a first stage, and a thermal high-dose implantation of regions 112 / 212 and 111 / 211 is performed after the room temperature channel implantation. Attempting to perform a channeling implantation of region 113 after a high-dose implantation of region 111 or 112 may result in a severely suppressed channeling effect, and thus the channeling implantation is much shallower compared to other possible cases for a given implant ion energy. High-dose implantations like those for regions 112 and 111 create significant ion damage, even at high temperatures. For example, if the channeling implantation follows a high-dose implantation of region 111 or 112, this damage may unfavorably suppress the ion channel.

[0085] In an additional or alternative embodiment, as Figure 9 shown, donor doping of the drift regions 102 / 202 / 702 can be performed using channeling implantation of phosphorus. For example, a channeling P implantation can be established along the

[0001] crystal direction of 4H SiC, which provides a property that is more than 3 times deeper than random implantation. Such a property is generally unexpected because more common donors such as nitrogen do not exhibit such a strong channeling effect in SiC. For example, when changing the beam direction from 4 degrees off-axis (referred to as "random") to the channeling condition, nitrogen typically only increases its ion range by approximately 40%. The SIMS profile 902 of channeled phosphorus is plotted together with the profile 904 of random implantation in Figure 9 which is calculated using the available Pearson IV approximation for early experimental data.

[0086] In some example embodiments of the Schottky rectifier device, the implanted layer has at least 2x10 14 cm -2The effective Gummel number, and / or a multi-layer body of the entire distance extending from the metal contact to the SiC substrate, wherein an epitaxial layer of a first conductivity type is formed on the SiC substrate. The metal contact may extend over the active region of the Schottky rectifier device, the active region including a channel region and the multi-layer body, and the Schottky rectifier device may further include a p-n diode edge that surrounds the active region with a continuous body of a second conductivity type and an array of deep edge bodies of the second conductivity type parallel to the multi-layer body. An embodiment of the Schottky rectifier device may include a junction termination region outside the p-n diode edge, and the junction termination region may include a junction termination body that surrounds the p-n diode edge and is connected to a plurality of deep JT bodies extending parallel to the multi-layer body and the deep edge body. An embodiment of the Schottky rectifier device may include a silicide ohmic contact between the tunnel contact layer and the metal contact.

[0087] It should be understood that in the foregoing description, when an element such as a layer, region, substrate, or component is referred to as being "on", "connected to", "electrically connected to", "coupled to", or "electrically coupled to" another element, it may be "directly on", "directly connected to", or "directly coupled" to the other element, or there may be one or more intervening elements. Conversely, when an element is referred to as being "directly on", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. Although the terms "directly on", "directly connected to", or "directly coupled to" may not be used throughout the detailed description, elements shown as "directly on", "directly connected to", or "directly coupled to" may be referred to as such. If so, the claims of the present application may be modified to recite the exemplary relationships described in the specification or shown in the drawings.

[0088] As used in the specification and claims, the singular forms may include the plural forms unless the context clearly dictates otherwise for a particular case. Spatially relative terms (e.g., "on", "above", "upper", "under", "below", "lower", etc.) are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. In some embodiments, the relative terms above and below may include vertically above and vertically below, respectively. In some embodiments, the term adjacent may include laterally adjacent or horizontally adjacent.

[0089] Some embodiments may be implemented using a variety of semiconductor processes and / or packaging technologies. Some embodiments may be implemented using a variety of types of semiconductor processing techniques associated with a semiconductor substrate, which includes but is not limited to, for example, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), and / or the like.

[0090] Although certain features of the embodiments have been shown as described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. Accordingly, it is to be understood that the appended claims are intended to cover all such modifications and changes that fall within the scope of the embodiments. It should be understood that they are presented by way of example only and not by way of limitation, and various changes may be made in form and detail. Any part of the apparatus and / or method described herein may be combined in any combination, except for mutually exclusive combinations. The embodiments described herein may include various combinations and / or sub-combinations of the functions, components, and / or features of the different embodiments described.

[0091] Although certain features of the embodiments have been shown as described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. Accordingly, it is to be understood that the appended claims are intended to cover all such modifications and changes that fall within the scope of the examples.

Claims

1. A Schottky rectifier device, characterized in that, the Schottky rectifier device comprises: a silicon carbide (SiC) layer; a channel region of a first conductivity type formed on the SiC layer; a metal contact formed on the channel region; a multi-layer body of a second conductivity type formed within the channel region and extending from the metal contact along the direction of the SiC layer, the multi-layer body comprising a first layer adjacent to the metal contact and having a first doping concentration, a second layer adjacent to the first layer and having a second doping concentration less than the first doping concentration, and a third layer adjacent to the second layer and having a third doping concentration less than the second doping concentration; and A charge balance region comprising the third layer and a portion of the channel region adjacent to the third layer, wherein within the charge balance region, charges of uncompensated acceptors and donors in the third layer and a portion of the channel region have a value of about 1×10 13 cm -2 or lower deviation.

2. The Schottky rectifier device according to claim 1, wherein the second layer has a doping concentration between 1x10 18 cm -3 and 1x10 19 cm -3 .

3. The Schottky rectifier device according to claim 1, wherein the first layer is degenerate doped and provides a tunneling contact between the metal contact and the second layer.

4. The Schottky rectifier device according to claim 1, wherein the multi-layer body extends at least 30% of the distance between the metal contact and the SiC layer.

5. The Schottky rectifier device according to claim 1, wherein the metal contact extends over an active region of the Schottky rectifier device, the active region comprising the channel region and the multi-layer body, and the Schottky rectifier device further comprises: a p-n diode edge that surrounds the active region with a continuous body of a second conductivity type and an array of deep edge bodies of a second conductivity type parallel to the multi-layer body.

6. The Schottky rectifier device according to claim 5, comprising a junction termination region outside the p-n diode edge, the junction termination region comprising: a junction termination body that surrounds the p-n diode edge and is connected to a plurality of deep JT bodies extending parallel to the multi-layer body and the deep edge body.

7. The Schottky rectifier device according to claim 1, wherein the multi-layer body extends the entire distance from the metal contact to the SiC layer.

8. A method for manufacturing a Schottky rectifier device, the method comprises: forming a silicon carbide (SiC) substrate; forming an epitaxial layer of a first conductivity type on the SiC substrate; forming a part of a charge balancing body having a donor of a second conductivity type; Repeat the formation of the epitaxial layer and the formation of a portion of the charge balance body until the charge balance body reaches a specified thickness, wherein within a charge balance region including the charge balance body and the surrounding portion of the epitaxial layer, the charges of uncompensated acceptors and donors within the charge balance body and the surrounding portion of the epitaxial layer have a deviation of approximately 1x10 13 cm -2 or less; forming an implantation layer on the charge balancing body, the implantation layer having a doping concentration of a second conductivity type that is higher than the doping concentration of the charge balancing body; forming a contact layer on the implantation layer; and forming a metal contact on the contact layer and the epitaxial layer.

9. The method according to claim 8, wherein the contact layer, the implantation layer, and the charge balancing body extend at least 30% of the distance between the metal contact and the SiC substrate.

10. The method according to claim 8, wherein the contact layer has a doping concentration higher than that of the implantation layer.

11. A Schottky rectifier device, characterized in that, the Schottky rectifier device comprises: a silicon carbide (SiC) layer; a channel region of a first conductivity type formed on the SiC layer; A metal contact formed on the channel region; A multi-layer body of a second conductivity type formed within the channel region and extending from the metal contact in the direction of the SiC layer, the multi-layer body including a tunnel contact layer adjacent to the metal contact, an implantation layer adjacent to the tunnel contact layer, and a deep layer adjacent to the implantation layer; and A charge balance region including the deep layer and a portion of the channel region adjacent to the deep layer, wherein within the charge balance region, the charges of uncompensated acceptors and donors in the deep layer and the portion of the channel region have a deviation of about 1x10 13 cm -2 or less, Wherein the multi-layer body extends at least 30% of the distance between the metal contact and the SiC layer.

12. The Schottky rectifier device according to claim 11, wherein the metal contact extends over an active region of the Schottky rectifier device, the active region including the channel region and the multi-layer body, the Schottky rectifier device further comprises: A p-n diode edge that surrounds the active region with a continuous body of a second conductivity type and an array of deep edge bodies of a second conductivity type parallel to the multi-layer body.

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