Low capacitance dual and multi-channel tvs with effective interconnection

Abstract

A transient voltage suppression device includes a plurality of interdigitated fingers arranged laterally along the main surface of an epitaxial layer. The plurality of interdigitated fingers includes a first type of interdigitated finger and a second type of interdigitated finger. Each of the first and second type interdigitated fingers includes a silicon controlled rectifier (SCR) region and a junction diode region. The plurality of second type interdigitated fingers are conductively coupled together through a second metal layer disposed above a first metal layer and electrically insulated from the first metal layer. The first metal layer conductively couples the SCR region and the junction diode region of the first type of interdigitated fingers.

Description

Technical Field

[0001] Embodiments of the present invention relate to semiconductor devices, and more specifically, various aspects of the present invention relate to transient voltage suppressors. Background Technology

[0002] Electronic equipment components are highly susceptible to transient voltage spikes (transients). A transient voltage spike is a brief increase in voltage across a device. These spikes can range from a few millivolts to several kilovolts. These events can be caused by noise in the power supply, such as induced noise from a motor or poorly designed power converter, faulty connections or wiring leading to arcing, or by natural electrical events such as electrostatic discharge. These transient events can damage sensitive equipment components, such as capacitors and resistors, leading to malfunction or equipment failure.

[0003] To prevent transients, various components are used to shunt voltage spikes away from sensitive parts of the device. Components used to prevent transients include decoupling capacitors, Zener diodes, avalanche diodes, metal-oxide varistors, polysilicon switches, and transient voltage suppressor diodes.

[0004] Transient voltage suppressor diodes (TVS) offer numerous advantages over other components used to prevent transients. In particular, TVS diodes operate rapidly, are suitable for medium-frequency applications, can be unidirectional or bidirectional, have low clamping voltage, and safely enter closed circuits.

[0005] Traditional transient voltage suppressor diode designs typically feature high capacitance and large device packages due to suboptimal interconnections between the various components. Therefore, various aspects of this invention have been developed to address these requirements. Summary of the Invention

[0006] To address the issues of suboptimal interconnection between components of transient voltage suppressor diodes, which typically involve high capacitance and large device packaging, this invention provides an improved TVS device.

[0007] The present invention provides a transient voltage suppression device, comprising:

[0008] An epitaxial layer on the surface of a substrate has a light concentration of ions of a first conductivity type, wherein the first conductivity type is opposite to the second conductivity type;

[0009] Multiple interdigitated fingers are arranged laterally along the main surface of the epitaxial layer. These interdigitated fingers include first-type interdigitated fingers and second-type interdigitated fingers. Each first-type interdigitated finger and each second-type interdigitated finger includes a silicon controlled rectifier (SCR) portion and a junction diode portion. The first-type interdigitated finger includes a portion of a first metal layer that electrically couples the SCR portion to the junction diode portion. Multiple second-type interdigitated fingers are coupled together through a second metal layer electrically insulated from the first metal layer. The second metal layer is disposed on top of the first metal layer. A junction diode is formed between the junction diode portions of the first-type interdigitated fingers and the junction diode portions of the second-type interdigitated fingers. An SCR is formed between the SCR portions of the first-type interdigitated fingers and the SCR portions of the second-type interdigitated fingers.

[0010] Preferably, the transient voltage suppression device further includes an input / output (I / O) contact pad coupled to the top edge of the second metal layer, wherein an insulating layer extends above the first metal layer and the first metal layer is below the second metal layer.

[0011] Preferably, in the transient voltage suppression device, the I / O contact pad is a wire connected to the upper part of the second metal layer.

[0012] Preferably, in the transient voltage suppression device, the SCR portion of the first type interdigitated finger and the SCR portion of the second type interdigitated finger are located close to each other in the epitaxial layer, and a portion of the epitaxial layer separates the SCR portion of the first type interdigitated finger from the SCR portion of the second type interdigitated finger.

[0013] Preferably, in the transient voltage suppression device, the first type interdigitated junction diode portion and the second type interdigitated junction diode portion are located close to each other in the epitaxial layer, and wherein a portion of the epitaxial layer separates the first type interdigitated junction diode portion from the second type interdigitated junction diode portion.

[0014] Preferably, in the transient voltage suppression device, the first type of interdigitation includes an SCR cathode region that serves as the cathode of the SCR formed between the SCR portion of the first type of interdigitation and the second type of interdigitation, and the second type of interdigitation includes an SCR anode region that acts as the SCR anode.

[0015] Preferably, in the transient voltage suppression device, the first type interdigit includes a junction diode anode region that serves as the anode of a junction diode formed between the junction diode portion of the first type interdigit and the junction diode portion of the second type interdigit, wherein the second type interdigit includes a junction diode cathode region that serves as the cathode of the junction diode.

[0016] Preferably, in the transient voltage suppression device, a first type of fork leads to electrical coupling to a reference node, and a second type of fork leads to electrical coupling to a protected node.

[0017] Preferably, in the transient voltage suppression device, the first type of interdigitation includes a first well region lightly doped with ions of a first conductivity type formed in the epitaxial layer and a collector region heavily doped with ions of a second conductivity type formed in the first well region, wherein a first metal is conductively coupled to the first well region and the collector region.

[0018] Preferably, in the transient voltage suppression device, the second type of interdigitation includes a second well region of the second conductivity type formed in the epitaxial layer with light doping, and an emitter region of the first conductivity type formed in the second well region with heavy doping, wherein the second metal is conductively coupled to the first well region and the emitter region.

[0019] Preferably, in the transient voltage suppression device, the first type of interdigitated junction diode portion includes a junction diode anode region formed in the epitaxial layer that is heavily doped with ions of the first conductivity type.

[0020] Preferably, in the transient voltage suppression device, the second type interdigitated junction diode portion includes a junction diode cathode region formed in the epitaxial layer heavily doped with ions of the second conductivity type.

[0021] Preferably, in the transient voltage suppression device, the second metal layer is thicker than the first metal layer.

[0022] Preferably, the transient voltage suppression device further includes a third metal layer conductively coupling the second type interdigitated SCR portion and the junction diode portion, wherein the third metal is conductively coupled to the second metal.

[0023] Preferably, in the transient voltage suppression device, the third metal layer is at the same height from the first metal layer as the first metal layer and is insulated from the first metal layer.

[0024] Preferably, in the transient voltage suppression device, a first set of vias through the insulating layer conductively couples the third metal layer to the SCR portion and the junction diode portion, and a second set of vias through the insulating layer couples the third metal to the second metal.

[0025] Preferably, in the transient voltage suppression device, the first metal layer is conductively coupled to a ground plane.

[0026] Preferably, in the transient voltage suppression device, the first type of interdigitated SCR portion includes a heavily doped SCR collector region with second conductivity type ions formed in a first well region of an epitaxial layer doped with first conductivity type ions and a first SCR well contact, and the second type of interdigitated SCR portion includes a heavily doped SCR emitter region with first conductivity type ions formed in a second well region of an epitaxial layer doped with second conductivity type ions and a second SCR well contact.

[0027] Preferably, in the transient voltage suppression device, the SCR emitter region is located near the SCR collector region.

[0028] Preferably, the transient voltage suppression device further includes an insulating layer that insulates the first metal from the epitaxial layer and the second metal, wherein a via through the insulating layer electrically couples the first metal to the corresponding SRC portion and the junction diode portion, and electrically couples the second metal to the corresponding SCR portion and the junction diode portion.

[0029] Compared to existing technologies, various aspects of the present invention provide an improved TVS device with a more optimized configuration of interconnections between its various parts. Due to the improved interconnect configuration, the improved device can have lower capacitance and a more compact device package compared to conventional TVS devices. Attached Figure Description

[0030] Other features and advantages of the invention will become apparent after reading the following detailed description and referring to the following figures, wherein:

[0031] Figure 1A This diagram illustrates an equivalent circuit diagram of a TVS protection device according to various aspects of the present invention.

[0032] Figure 1B The diagram shows a top view of a pair of interdigitated fingers in a single channel of an improved TVS according to various aspects of the present invention, the improved TVS comprising two types of overlapping interdigitated fingers arranged laterally along the main surface of the epitaxial layer.

[0033] Figure 2A This represents a cutaway three-dimensional perspective view of an improved single channel of a TVS device according to various aspects of the present invention.

[0034] Figure 2B This is a top view of an improved multichannel bidirectional or unidirectional TVS device without an insulating layer, according to various aspects of the present invention.

[0035] Figure 3 This represents another embodiment of an improved multichannel bidirectional or unidirectional TVS device without an insulating layer, according to various aspects of the present invention.

[0036] Figure 4This is a top-down view showing another embodiment of an improved multichannel bidirectional or unidirectional TVS device without an insulating layer, according to various aspects of the present invention.

[0037] Figure 5 The image shows a top-down view of an improved multichannel bidirectional or unidirectional TVS device without an insulating layer, and with a portion of a second metal layer, according to various aspects of the present invention.

[0038] Figure 6 This is a top-down view showing another embodiment of an improved multichannel bidirectional or unidirectional TVS device without an insulating layer, according to various aspects of the present invention, and including a portion of the second metal layer.

[0039] Figure 7 This is a cut-out side view of an alternative embodiment of an improved single-channel TVS device according to various aspects of the present invention. Detailed Implementation

[0040] Although the following detailed description contains many specific details for illustrative purposes, those skilled in the art will understand that many variations and modifications to these details are within the scope of the invention. Therefore, the exemplary embodiments of the invention described below do not impose any general limitation or restriction on the claimed invention.

[0041] In the following detailed description, reference is made to the accompanying drawings, which form part of this invention, illustrating by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terms such as “top,” “bottom,” “front,” “rear,” “leading,” “tail,” etc., are used with reference to the orientation of the described figures. Since components of embodiments of the invention can be positioned in multiple different orientations, directional terms are used for illustration and not for limitation in any way. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention. Therefore, the following detailed description should not be considered a limiting description, and the scope of the invention is defined by the appended claims.

[0042] For clarity, not all conventional features of the implementations described herein are shown and described. Those skilled in the art will understand that in any such implementation, numerous implementation-specific decisions must be made to achieve developer-specific goals, such as complying with application and business-related constraints, and these specific goals will vary from implementation to implementation and from developer to developer. Furthermore, it should be understood that such development work can be complex and time-consuming, but will be a routine engineering task for those of ordinary skill in the art who will benefit from this invention.

[0043] This invention relates to silicon doped with ions of a first conductivity type or a second conductivity type. The ions of the first conductivity type can be the opposite of the second conductivity type. For example, the ions of the first conductivity type can be n-type, which generate charge carriers when doped into silicon. Ions of the first conductivity type include phosphorus, antimony, bismuth, lithium, and arsenic. The ions of the second conductivity type can be p-type, which create holes for charge carriers when doped into silicon, and are thus referred to as the opposite of n-type. p-type ions include boron, aluminum, gallium, and indium. Although the above description refers to n-type as the first conductivity type and p-type as the second conductivity type, the invention is not limited thereto; p-type can be the first conductivity type, and n-type can be the second conductivity type.

[0044] In the following detailed description, reference is made to the accompanying drawings, which form part of the invention and illustrate specific embodiments in which the invention may be practiced. For convenience, the use of + or – after specifying conductivity or net impurity carrier type (p or n) generally refers to the relative concentration of the specified type of net impurity carriers within the semiconductor material. Generally, n+ materials have a higher concentration of N-type net dopant (e.g., electrons) than n materials, and n materials have a higher carrier concentration than n- materials. Similarly, p+ materials have a higher concentration of p-type net dopant (e.g., holes) than p materials, and p materials have a higher concentration than p- materials. It should be noted that what is relevant is the net carrier concentration, not necessarily the dopant. For example, a material can be heavily doped with n-type dopant, but if the material is also sufficiently dedoped with p-type dopant, the material will still have a relatively low net carrier concentration. As used herein, a dopant concentration less than about 10¹⁶ / cm³ can be considered “lightly doped,” while a dopant concentration greater than about 10¹⁷ / cm³ can be considered “heavily doped.”

[0045] You can refer to Figure 1AThe equivalent circuit diagram shown illustrates the operation of the depicted TVS device. The TVS device includes a PN junction diode DL1 forward-connected between the protected node (I / O terminal) and ground. That is, the anode of diode DL1 is connected to the ground node, and the cathode of diode DL1 is connected to the protected node. Diode DL1 serves as the low-side switching diode of the TVS protection device. The TVS device includes an SCR device connected in parallel with the PN junction diode DL1. Specifically, the SCR device can be represented as two PNP and NPN bipolar transistors connected back-to-back. The anode of the SCR device is the P-type emitter of the PNP bipolar transistor, which is also connected to the N-type base via a base resistor RNW. The cathode of the SCR device is the N-type emitter of the NPN bipolar transistor, connected to ground and the N-type base of the NPN bipolar transistor via a base resistor RPW. With this configuration, the contribution to the parasitic capacitance of the TVS device at the protected node (I / O terminal) mainly comes from the N-type region of the PN junction diode DL1 and the anode of the SCR device.

[0046] According to various aspects of the present invention, a transient voltage suppression device may include a semiconductor epitaxial layer on the surface of a semiconductor substrate having a low concentration of ions of a first conductivity type opposite to a second conductivity type. A plurality of semiconductor fingers may be arranged laterally along the main surface of the epitaxial layer. Semiconductor interdigitates may include first-type interdigitates and second-type interdigitates. The first and second-type interdigitates may include silicon-controlled rectifier (SCR) portions and junction diode portions.

[0047] The first type of interdigitated fingers includes a first metal layer that conductively couples the SCR portion to the junction diode portion, wherein the first metal layer couples the plurality of interdigitated fingers of the first type together. The plurality of interdigitated fingers of the second type are connected together via a second metal layer, which is electrically insulated from the first metal layer and located on top of the first metal layer. A junction diode is formed between the junction diode portion of the first type of interdigitated fingers and the connection portion of the second type of interdigitated fingers. An SCR is formed between the SCR portion of the first type of interdigitated fingers and the SCR portion of the second type of interdigitated fingers. The SCR portions of the first type of interdigitated fingers and the SCR portions of the second type of interdigitated fingers may be located close to each other in the epitaxial layer. Furthermore, the junction diode portions of the first type of interdigitated fingers and the junction diode portions of the second type of interdigitated fingers may be located close to each other in the epitaxial layer.

[0048] The first type of interdigitation finger may include an SCR cathode region that acts as the cathode of an SCR formed between the SCR portions of the first type of interdigitation finger and the SCR portions of the second type of interdigitation finger, wherein the second type of interdigitation finger may include an SCR anode region that acts as the anode of the SCR. In a bidirectional device, the first type of interdigitation finger may be electrically coupled to a reference node, and the second type of interdigitation finger may be electrically coupled to a protected node. In a unidirectional device, a first metal layer may be conductively coupled to a ground plane. The first type of interdigitation finger may include a lightly doped first well region of a first conductivity type formed in an epitaxial layer, wherein the SCR portion of the first type of interdigitation finger may further include an SCR collector region heavily doped with ions of a second conductivity type in the first well region and the first SCR well contact region. The second type of interdigitation finger may include a lightly doped second well region of a second conductivity type formed in an epitaxial layer, wherein the SCR portion of the second type of interdigitation finger may further include an SCR emitter region heavily doped with ions of the first conductivity type in the second well region and the second SCR well contact region. The junction diode portion of the first type of interdigitation finger may include a junction anode region heavily doped with ions of the first conductivity type. The second type of interdigitated junction diode region may include a junction diode cathode region heavily doped with ions of a second conductivity type. The TVS device may also include an insulating layer that insulates the first metal from the epitaxial layer and the second metal, wherein the first metal is electrically coupled to the respective SRC region and junction diode region through vias in the insulating layer, and the second metal is electrically coupled to the respective SCR region and junction diode region.

[0049] The first type of interdigitated SCR portion may include an SCR collector region heavily doped with ions of the second conductivity type and a first SCR well contact region formed in a first well region of an epitaxial layer doped with ions of the first conductivity type. The second type of interdigitated SCR portion may include an SCR emitter region heavily doped with ions of the first conductivity type formed in a second well region of an epitaxial layer doped with ions of the second conductivity type. The first type of interdigitated SCR portion and the second type of interdigitated SCR portion are located close to each other in the epitaxial layer.

[0050] Input / output (I / O) contact pads can be coupled to the top side of a second metal layer, wherein the first metal layer is below the second metal layer. The I / O contact pads can be wires connected to the upper part of the second metal layer. The second metal layer can be thicker than the first metal layer.

[0051] In the second type, the second metal layer of each fork finger can be interrupted on the first metal layer. The interruption of the second metal layer for each fork finger in the second type can include contact pads. The contact pads for each fork finger in the second type can be electrically coupled to form a single channel. This so-called "top pad" configuration allows for free design of the fork finger geometry and allows the first metal layer to extend across the entire chip. This makes the fork fingers longer, capable of carrying higher currents and lower voltages. In contrast, the conventional configuration uses a top bus connection to ground. In this configuration, the fork fingers are smaller, and their length is limited. Therefore, parasitic capacitance increases due to the bus.

[0052] Figure 1B The diagram shows a top view of a pair of interdigitated fingers in a single channel of an improved TVS comprising two types of overlapping interdigitated fingers arranged laterally along a first direction on the main surface of an epitaxial layer 101 according to an aspect of the invention. For example, the epitaxial layer 101 may be lightly doped with ions of a first conductivity type, and, where not limited, may be doped with p-type ions. The first type of interdigitated fingers may include a silicon controlled rectifier (SCR) portion 121 and a junction diode portion 122. The SCR portion 121 may include a collector and good contact of the SCR in the epitaxial layer formed between the SCR portions of the first and second interdigitated fingers. The SCR portion of the first interdigitated finger 121 may include a first well region 102 doped with ions of the first conductivity type. A heavily doped SCR collector region 103 with ions of a second conductivity type may be formed in the well region, and a portion of the SCR collector region and the first well region may serve as a first SCR well contact 104. The SCR collector region 103 and the first well contact region 104 may serve as an SCR cathode region. For example, the SCR collector region may be heavily doped with N-type ions 103 next to a first SCR well contact region 104, which in turn is heavily doped with P-type ions 104 in a well region 102, which is more heavily doped with P-type ions than the epitaxial layer. The doping concentration of the first SCR well contact region 104 may be the same as that of the well region. The first type interdigitated junction diode portion 122 may include a junction anode region 105 formed in the epitaxial layer 101 and heavily doped with ions of the first conductivity type. The SCR collector region 103, the first SCR well contact region 104, and the junction diode anode region 105 may be electrically coupled via a connection 110, which may include, for example, but is not limited to, conductive vias and a first metal layer. As shown, for a unidirectional device, another connection 110 may also couple a first conductive ground to ground. In some implementations, multiple channels may be connected together with floating conductors to form a bidirectional device.

[0053] The second interdigitated type may include an SCR portion 123 and a junction diode portion 124. The second interdigitated type SCR portion 123 may include a well region 106 in an epitaxial layer doped with ions of a second conductivity type. The second interdigitated SCR portion 123 may also include a heavily doped region of a first conductivity type formed in the well region serving as an SCR emitter region 108. The SCR emitter region and SCR well contact region 107 serve as the anode of the SCR formed in the epitaxial layer. For example, without limitation, the SCR emitter region 108 may be heavily doped with P-type ions adjacent to the second SCR well contact region 107, which is heavily doped with N-type ions in the N-type well region 106. The doping concentration of the second SCR well contact region 107 may be the same as that of the well region 106, and the second SCR well contact region may be only a part of the well region. The SCR portion 123 may be formed as the anode of an SCR generated in the epitaxial layer between the SCR regions of the first and second interdigitated types. As shown, the second interdigitated SCR region 123 is located near the SCR region of the first interdigitated type 121, which allows for reduced capacitance and easier tuning. Note that in the illustrated embodiment, the second well region 106 includes two SCR emitter regions 108, and the first well region 102 includes two SCR collector regions 103, to allow for lateral striping along the main channel of the epitaxial layer and reduce wasted space. The junction diode portion of the interdigitated fingers for the second type 124 is located on the side of the SCR portion 123, which is perpendicular to the side of the SCR portion 123 of the interdigitated fingers of the first types 121, 122, and close to the junction diode portion of the interdigitated fingers for the first type 122. The junction diode portion 124 for the second type interdigitated fingers may include a junction cathode region 109 formed in the epitaxial layer, which is heavily doped with ions of a second conductivity type. The junction diode portion 124 and SCR portion 123 of each interdigit of the second type can be conductively coupled 111 to the conductive coupling of the first type interdigit 110, and the conductive coupling of the second type interdigit 111 can be electrically isolated from the conductive coupling of the first type interdigit 110. As shown, the second type interdigit can also be conductively coupled to the I / O or active portion of the device to be protected. During normal operation, the TVS device operates in a latch-up mode to prevent current from flowing to the ground connection, but when a transient voltage spike occurs at the I / O, the device may adjust to allow current to be shunt through ground, keeping the transient away from the device to be protected.

[0054] Figure 2AThis is a three-dimensional perspective view of a modified single channel of a TVS device according to various aspects of the present invention. An epitaxial layer 202 is disposed on the main surface of a substrate lightly doped with ions of a first conductivity type. The epitaxial layer is lightly doped with ions of the first conductivity type at a concentration relatively greater than that of the substrate 201. As shown, the first type interdigitator includes an SCR portion (regions 203, 205, 206) with transverse stripes formed in the main surface of the epitaxial layer and a junction diode anode region (region 207). A portion of a first metal 221 runs parallel to the sidebands and couples the SCR collector region 204 and the first SCR well contact region 205 to the junction diode anode region 207. An insulating layer 223 insulates the first metal 221 from the epitaxial layer 202 and the second metal 222. A via 241 lined with a conductive material connects the SCR portion and the junction diode portion of the first type interdigitator to the first metal 221. The via can be formed through the insulating layer 223 and lined with a metal (e.g., tungsten, titanium, aluminum, or any combination thereof). The first metal 221 can connect each of the first type of interdigitated fingers in a direction orthogonal to the transverse stripes. The first metal 221 can also couple the first type of interdigitated fingers between different channels of the device. In some embodiments, to create a unidirectional device, the first metal 221 couples the first type of interdigitated fingers to ground. In other embodiments creating a bidirectional device, the first metal 221 can be coupled to a floating node, which can be further coupled to another reverse device.

[0055] The second type of interdigitated region includes an SCR portion with transverse stripes formed along the main surface of the epitaxial layer 202 and a junction diode portion. The SCR portion of the second type of interdigitated region includes an emitter region 213 and a second well contact region 214 formed in the second well region 211. The SCR portions of the second interdigitated regions 211, 213, and 214 are formed in the epitaxial layer 202 near the SCR portions of the first interdigitated regions 203, 205, 206, and 214. Similarly, a junction cathode region 215 is formed in the epitaxial layer near the junction anode region 207. Each junction anode region 207 is located near a corresponding side of the SCR portion of the first interdigitated regions (203, 205, 206), perpendicular to the proximal side of the SCR portion of the second interdigitated regions (211, 213, 214). Similarly, each junction cathode region 215 is located near the corresponding side of the SCR portion of the second interdigitated type (211, 213, 214), perpendicular to the proximal side of the SCR portion of the first interdigitated type (203, 205, 206). A portion of the epitaxial layer 202 separates the first well region 203 from the second well region 211. In the respective second well region 211 and first well region 203, the SCR emitter region 213 and the SCR collector region 205 are doped to a depth of about 0.2 to 0.5 micrometers from the surface of the epitaxial layer. The first well region 203 and the second well region 211 are doped to about 1 to 1.5 micrometers from the surface of the epitaxial layer.

[0056] The second metal layer 222 conductively couples the second type of interdigitates in the channel, and is parallel to and orthogonal to the transverse of the doped stripes in the epitaxial layer. The third metal layer 212 couples the SCR portion of the second interdigitate type (211, 213, 214) to the junction diode portion 215. The third metal layer 212 may be at the same height as the first metal layer 221 at the same level as the substrate, and the third metal layer 212 may be formed simultaneously with the first metal layer 221. The thickness of the third metal layer 212 may be the same as the first metal layer 221, and it is insulated from the first metal layer 221 by an insulating layer 223. The second metal layer 222 is electrically coupled to the second type of interdigitates and the SCR portion of the junction diode cathode region through a via 242 in the insulating layer 223. In some embodiments, the via 242 couples the SCR portion and the junction diode portion of the second type of interdigitates to the third metal, and the third metal is coupled to the second metal through a third via 243, which creates a connection between the second type of interdigitates on the first metal of the first type of interdigitates. The second metal layer 222 can operate orthogonally to the parallel stripes of the SCR portion and the junction diode portion to couple multiple interdigitates of the second type and create channels in a multichannel device. The second type interdigitates can be interrupted in the epitaxial layer to allow the first metal to connect between the first type interdigitates. The first and second metal layers can be made of any suitable conductive metal, such as, but not limited to, gold, silver, copper, tungsten, titanium, aluminum, or any suitable alloy thereof. I / O contact pads 231 can be coupled to the top surface of the second metal layer 222. I / O contact pads 231 can be a redistribution layer (RDL) for channels or wire bonding. I / O contact pads can be made of any suitable metal, such as, but not limited to, copper, aluminum, silver, or gold. I / O contact pads 231 can be formed on the epitaxial layer near the intersection of the SCR portion and the junction diode portion of the first and second type interdigitates.

[0057] The insulating layer 223 can be coupled to the bottom of the second metal layer 222, and the first metal layer 221 can extend beneath at least a portion of the second metal layer 222. The contact pad 231 can couple a second type of interdigitated coupling to a device to be protected against transients. It should be noted that the first metal layer 221 can be thinner than the second metal layer 222. The first metal layer 221 is parallel to the transverse striations in the formed epitaxial layer and orthogonal to the extent that the SCR portion and the junction diode anode region 207 can be connected.

[0058] Figure 2 shows a top view of an improved multi-channel bidirectional or unidirectional TVS device without an insulating layer according to various aspects of the present invention. The TVS device shown includes five channels. Each channel includes a contact pad 231 coupled to a second conductive layer 222. A second metal layer 222 couples a second interdigitated type and forms a channel for the TVS device. In the multi-channel TVS device, each channel is isolated from the other channels. A first metal layer 221 extends below the second metal layer, forming overlapping interdigitated fingers when a portion of the second interdigitated finger is located on either side of the first interdigitated finger and the second metal extends on top of the first metal. As shown, the first metal layer 221 laterally traverses the epitaxial layer, parallel to the stripes of the SCR portion and the junction diode portion below the first metal. The second metal layer 222 runs perpendicular to the first metal and couples the second type of interdigitated finger. The first metal layer 221 may extend laterally to an interconnect 251, which may couple the first metal layer 221 to a floating node or ground. The central contact pad 253 can be coupled to ground, in which case the interconnect 251, the second metal layer 252, and the contact pad 253 will be electrically coupled. As shown, each first metal layer 221 in each channel is coupled to the center ground 251 for unidirectional devices via the interconnect 251. In bidirectional devices, the contact pad 253 can be coupled to another I / O channel of the device to be protected. Furthermore, the second metal layer 252 can be coupled to the contact pad 253 and multiple second fingers (not shown in this figure). In bidirectional TVS devices, the interconnect 251 can serve as the first metal layer and can couple multiple first interdigits, each first finger overlapping a corresponding second interdigit, thereby creating an SCR and a junction diode in the epitaxial layer, as described with respect to the figure. 2A In the case of unidirectional devices, the second metal layer 252 can cover the interconnect 251 to improve conduction and reduce resistance.

[0059] Figure 3 This illustrates another embodiment of an improved multi-channel bidirectional or unidirectional TVS device without an insulating layer, according to various aspects of the invention. In the illustrated embodiment, the I / O contact pads for each channel have been replaced by wire bonding 301, and the ground contact pads in the unidirectional device or central channel of the multi-channel device 302 have also been replaced by wire bonding. The wire bonding reduces manufacturing costs. Furthermore, the device includes interconnects 303 that run orthogonally to the lateral direction of the first and second type interdigitated fingers along the outer edge of the device. Interconnects 303 connect the edges of the first metal layer 221 to other first metal layers 221 via a central first metal layer 251, which may also be a ground layer. In the case of a unidirectional device, a second metal layer 252 may cover the interconnects 251 to improve conductivity and reduce resistance.

[0060] Figure 4This is a top view illustrating another embodiment of an improved multi-channel bidirectional or unidirectional TVS device without an insulating layer according to various aspects of the present invention. In this embodiment, the channels of the improved TVS device are arranged in a row. A first metal layer 421 of each channel may be connected via an interconnect 401. The interconnect 401 may also couple each first interdigitated type of first metal layer 421 to ground. In this embodiment, a second metal layer 422 is both parallel to and orthogonal to the transverse stripes 402 of the SCR portion and the junction diode region, which conductively couples each second type of interdigit in the channel. The interconnect 401 allows current to flow between the devices, thereby reducing resistance and clamping voltage. Furthermore, the interconnect 401 may be covered by a second metal layer to reduce resistance.

[0061] Figure 5 This is a top view of a modified multichannel bidirectional or unidirectional TVS device without an insulating layer and having a portion of an outlined second metal layer. As shown, second-type interdigitated fingers are connected to a second metal layer 502 through vias 501 in the insulating layer. The second metal layer is also orthogonal to the transverse stripes 503 of the SCR and junction diode portions in the epitaxial layer to couple the second metal layer 502 of each interdigitated finger. A first metal layer 421 extends through the device and is coupled together through interconnects 401, which may be formed of the same metal as the first metal layer and are orthogonal to the stripes of the SCR and junction diode portions in the epitaxial layer to connect each first metal layer of the first interdigitated finger type. Here, the second metal 503 creates a contact line array perpendicular to the interdigitated fingers through vias 501.

[0062] Figure 6 This is a top view illustrating another embodiment of a modified multichannel bidirectional or unidirectional TVS device, which lacks an insulating layer and includes a portion of the second metal layer. In this embodiment, the second metal 601 is interrupted on the first metal layer 221. Each second metal layer 601 includes a contact region where the second metal is interrupted on the first metal. Multiple contact regions are conductively coupled to form a single channel. This implementation reduces the capacitance in the first metal layer 221 by eliminating a portion of the second metal on the first metal layer.

[0063] Figure 7A represents a cross-sectional view of an alternative embodiment of a single channel of a TVS device according to various aspects of the present invention. The improved multi-channel TVS device may include a substrate 701 lightly doped with ions of a first conductivity type. An epitaxial layer 702 may be formed on the main surface of the substrate 701, and the epitaxial layer 702 may be doped with more ions of the first conductivity type than the substrate. The channel shown includes three pairs of overlapping interdigitates, wherein each second-type interdigitate is electrically coupled to a second metal layer 722 extending on its top and electrically isolated from a first metal layer 721. I / O contact pads ( Figure 2A (Not shown) It can be coupled to the second metal layer 722 and electrically coupled to the protected device via a second type of fork in a channel. Each channel may include multiple overlapping forks of the first and second channels arranged laterally on the main surface of the epitaxial layer 702. The first type of fork includes an SCR portion and a junction diode portion. The SCR portion includes a well region 703 formed in the epitaxial layer and doped with ions of a first conductivity type. The SCR portion of the first fork type includes the cathode of the SCR formed in the epitaxial layer 731. The first well region 703 is doped at a depth of about 1-1.5 micrometers. The SCR portion also includes a collector region heavily doped with ions of a second conductivity type 705 and a good contact region 706. The collector region 705 and the first SCR well contact region 706 create an SCR cathode for the SCR formed in the epitaxial layer. The SCR collector region 705 may be doped at a depth of about 0.2-0.5 micrometers. The first fork type also includes a junction diode portion, which may be the anode of a junction diode 732 formed in the epitaxial layer between the first and second overlapping forks. As shown in the figure, the junction portion of the first type of interdigitated finger may include a junction anode region 707 formed in the epitaxial layer and heavily doped with ions of a first conductivity type. Both the SCR portion and the junction diode portion of the first interdigitated finger are electrically coupled to a first metal layer 721. An insulating layer 723 electrically insulates the first metal layer from the epitaxial layer 702 and the second metal layer 722. Conductive material in vias through the insulating layer contacts the anode region of the junction diode 707 and heavily doped regions 705, 706 with opposite conductivity types. The first metal layer 721 can electrically couple each interdigitated finger of the first type to ground for a unidirectional device or two second channels for bidirectional devices.

[0064] The second interdigitated type includes an SCR portion and a bonding portion, and includes a second metal layer on a first metal layer electrically isolated from the first metal layer. The SCR portion of the second-type interdigitated finger includes a well region 711 doped with ions of a second conductivity type. The well region of the second-type interdigitated finger is formed at a depth of 1-1.5 micrometers. An SCR emitter region 714 is formed in the second well region 711, and a portion of the well region may create a second SCR well contact region 713. These regions serve as the anode of the SCR formed in the epitaxial layer 731 between the SCR portions of the first and second types of interdigitated fingers. An SCR emitter region heavily doped with ions of the first conductivity type 714 is formed in the well region at a depth of approximately 0.2-0.5 micrometers. The SCR emitter region 714 may include, for example, but not limited to, a region of heavily doped P-type ions 713 adjacent to the second SCR contact region, where the heavily doped N-type ions 714 are formed in a relatively lightly doped N-type epitaxial layer 711. The doping concentration of the second SCR well contact region may be the same as that of the well region. The second type of interdigitation includes a junction diode portion that serves as the cathode of a junction diode formed in the epitaxial layer 732. The junction diode cathode region 715 is a region in the epitaxial layer heavily doped with ions of the second conductivity type. The junction diode cathode region 715 is electrically coupled to the second metal layer 722 through vias in the insulating layer 723. The second metal layer 722 electrically couples the emitter and second well contact regions of the SCR portions 713, 714 to the junction cathode region 715. The second metal layer 722 may also include connections coupled to the top and bottom of the metal layer, which may contact the insulating layer 723. Contact pads (as shown in FIG. 2) and the second metal layer 722 couple the anode for the SCR and the cathode for the junction diode formed in the epitaxial layer to the I / O of the device to be protected from transients. The first and second metal layers may be made of any suitable conductive metal, such as, but not limited to, gold, silver, copper, tungsten, titanium, aluminum, or any suitable alloy thereof.

[0065] also, Figure 7The different directions of the interdigitated fingers are indicated. As shown, the interdigitated fingers can be oriented to the left or right. The left-side orientation has a first SCR portion, which has a first SCR well region 703 and an SCR collector region 705, as well as a first SCR well contact region 706 located near the left side of the substrate. Similarly, a second SCR portion having a second SCR well region 711 and a second SCR well contact region 713, and an SCR emitter region 714 are located near the first SCR portion and the left side of the device. As shown, the anode region 707 of the first interdigitated type junction diode is located near the right side of the device and is located on one side of the first SCR well region 703, opposite to the SCR portions of the second interdigitated types 711, 713, and 714. The junction diode cathode region for the second type interdigitated fingers 715 is located in the epitaxial layer near the side of the junction diode anode region 707, and is located on the side of the junction diode anode region 707 opposite to the SCR portions 703, 705, and 706 of the first interdigitated fingers. As shown to the right, the first interdigitated type SCR portions 704, 708, and 709 are located near the right side of the device. The SCR portions of the second interdigitated types 712, 716, and 717 are also located near the right side of the device, and are situated to the side of the first interdigitated type SCR portions, opposite to the anode region 710 of the first interdigitated type junction diode. Similarly, the cathode region 718 for the second interdigitated type junction diode is located close to the anode region 710 for the first interdigitated type junction diode, and close to the side of the anode region 710 of the junction diode opposite to the SCR portions of the first interdigitated types 704, 708, and 709. Although the orientation of these regions is mirrored, the operation between the interdigitated portions in the left-right direction remains unchanged. Various aspects of the present invention provide an improved TVS device with a more optimized configuration of interconnections between its various portions. Due to the improved interconnect configuration, the improved device can have lower capacitance and a more compact device package compared to conventional TVS devices. While the above is a complete description of preferred embodiments of the invention, various alternatives, modifications, and equivalents can be used. Therefore, the scope of this invention should not be determined by reference to the foregoing description, but rather by reference to the appended claims and their full equivalents. Any feature, whether preferred or not, may be combined with any other feature, whether preferred or not. In the following claims, the indefinite article “A” or “An” refers to the number of one or more items following that article, unless expressly stated otherwise. The appended claims should not be construed as including means plus functional limitations, unless such limitation is expressly recited in a given claim using the phrase “means”. Any element of “means” not expressly stated in the claims as “for” performing a particular function shall not be construed as a “means” or “step” clause as defined in Section 112, Section 6 of Title 35 of the United States Code.

[0066] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A transient voltage suppression device, comprising: An epitaxial layer on the surface of a substrate has a light concentration of ions of a first conductivity type, wherein the first conductivity type is opposite to the second conductivity type; Multiple interdigitated fingers are arranged laterally along the main surface of the epitaxial layer. These interdigitated fingers include first-type interdigitated fingers and second-type interdigitated fingers. Each first-type interdigitated finger includes a silicon controlled rectifier (SCR) portion and a junction diode portion. The first-type interdigitated finger includes a portion of a first metal layer that electrically couples the SCR portion of the first-type interdigitated finger to the junction diode portion of the first-type interdigitated finger. Multiple second-type interdigitated fingers are coupled together through a second metal layer electrically insulated from the first metal layer, which is disposed on top of the first metal layer. A junction diode is formed between the junction diode portions of the first-type interdigitated fingers and the junction diode portions of the second-type interdigitated fingers. An SCR is formed between the SCR portions of the first-type interdigitated fingers and the SCR portions of the second-type interdigitated fingers. The first-type interdigitated finger includes a first well region lightly doped with ions of a first conductivity type formed in the epitaxial layer and a collector region heavily doped with ions of a second conductivity type formed in the first well region. The first metal layer is electrically coupled to the first well region and the collector region through vias lined with conductive material. The second metal layer is thicker than the first metal layer; The transient voltage suppression device further includes a third metal layer conductively coupling a second type interdigitated SCR portion and a second type interdigitated junction diode portion, wherein the third metal layer is conductively coupled to the second metal layer; The third metal layer is at the same height as the first metal layer from the epitaxial layer and is insulated from the first metal layer.

2. The transient voltage suppression device of claim 1 further includes an input / output (I / O) contact pad coupled to the top edge of the second metal layer, wherein an insulating layer extends above the first metal layer and the first metal layer is below the second metal layer.

3. The transient voltage suppression device of claim 2, wherein the I / O contact pad is a wire connected to the upper part of the second metal layer.

4. The transient voltage suppression device of claim 1, wherein the SCR portion of the first type interdigitated finger and the SCR portion of the second type interdigitated finger are located close to each other in the epitaxial layer, and wherein a portion of the epitaxial layer separates the SCR portion of the first type interdigitated finger from the SCR portion of the second type interdigitated finger.

5. The transient voltage suppression device of claim 1, wherein the first type of interdigitated junction diode portion and the second type of interdigitated junction diode portion are located close to each other in the epitaxial layer, and wherein, A portion of the epitaxial layer separates the first type of interdigitated junction diode portion from the second type of interdigitated junction diode portion.

6. The transient voltage suppression device of claim 1, wherein the first type interdigitator includes an SCR cathode region that serves as the cathode of an SCR formed between the SCR portion of the first type interdigitator and the second type interdigitator, and wherein the second type interdigitator includes an SCR anode region that acts as the SCR anode.

7. The transient voltage suppression device of claim 1, wherein the first type interdigitator includes a junction diode anode region that serves as the anode of a junction diode formed between the junction diode portion of the first type interdigitator and the junction diode portion of the second type interdigitator, wherein the second type interdigitator includes a junction diode cathode region that serves as the cathode of the junction diode.

8. The transient voltage suppression device of claim 1, wherein a first type fork is electrically coupled to a reference node and a second type fork is electrically coupled to a protected node.

9. The transient voltage suppression device of claim 1, wherein the second type of interdigitation includes a second well region of the second conductivity type formed in the epitaxial layer and an emitter region of the first conductivity type formed in the second well region by heavy doping, wherein the second metal layer is conductively coupled to the second well region and the emitter region.

10. The transient voltage suppression device of claim 1, wherein the first type interdigitated junction diode portion includes a junction diode anode region formed in the epitaxial layer and heavily doped with ions of the first conductivity type.

11. The transient voltage suppression device of claim 1, wherein the second type interdigitated junction diode portion includes a junction diode cathode region formed in the epitaxial layer heavily doped with ions of the second conductivity type.

12. The transient voltage suppression device of claim 1, wherein a first set of vias through the insulating layer conductively couples the third metal layer to the SCR portion and the junction diode portion, and a second set of vias through the insulating layer couples the third metal to the second metal.

13. The transient voltage suppression device of claim 1, wherein the first metal layer is conductively coupled to a ground plane.

14. The transient voltage suppression device of claim 1, wherein the first type of interdigitated SCR portion includes a heavily doped SCR collector region with second conductivity type ions formed in a first well region of an epitaxial layer doped with first conductivity type ions and a first SCR well contact, and the second type of interdigitated SCR portion includes a heavily doped SCR emitter region with first conductivity type ions formed in a second well region of an epitaxial layer doped with second conductivity type ions and a second SCR well contact.

15. The transient voltage suppression device of claim 14, wherein the SCR emitter region is located near the SCR collector region.

16. The transient voltage suppression device of claim 1 further includes an insulating layer that insulates the first metal from the epitaxial layer and the second metal, wherein a via through the insulating layer electrically couples the first metal to a corresponding SRC portion and a junction diode portion, and electrically couples the second metal to a corresponding SCR portion and a junction diode portion.

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