TW449861B - Schottky diode with dielectric trench - Google Patents

Abstract

An improved diode or rectifier structure and method of fabrication is disclosed involving the incorporation in a Schottky rectifier, or the like, of a dielectric filled isolation trench structure formed in the epitaxial layer adjacent the field oxide layers provided at the edge of the active area of the rectifier, for acting to enhance the field plate for termination of the electric field generated by the device during operation. The trench is formed in a closed configuration about the drift region and by more effectively terminating the electric field at the edge of the drift region the field is better concentrated within the drift region and acts to better interrupt reverse current flow and particularly restricts leakage current at the edges.

Description

44986 1 V. Description of the Invention Field of the Invention The present invention relates to the structure and fabrication of Schottky diodes or rectifiers, and particularly to the dielectric isolation trenches of such elements. )structure. Background of the Invention L; i. BALIGA in US Patent No. 5612567 discusses in detail different forms of Schottky rectifiers and how they operate. Basically, these rectifiers are formed by a first A semiconductor N + -type substrate layer and a second N-type semiconductor layer epitaxially grown on its opposite surface. The second N-layer system serves as a drift region, and typically has a discontinuous P + region located on the opposite surface of the drift region. A metal anode contact is formed on the opposite surface of the second N-layer, which forms a Schottky contact region with the P + region. As mentioned in this patent, the reduced operating voltage required to reduce power loss and increase energy efficiency requires a reduced on-state voltage drop across the rectifier 'but maintains a high forward bias current density and minimizes reverse bias Voltage leakage current. However, 'for a Schottky barrier (bar r i e r) rectifier' it is difficult to minimize the voltage drop generated during forward bias and the leakage current generated during reverse bias at the same time. Although the degree of doping of the semiconductor region can be used to affect the height of the Schottky barrier, in the case of a higher degree of doping, there is an impact ionization effect. ^ Previous techniques:

Page 4 449861 V. Description of the invention (2) In the solution to the problem of leakage current, U.S. Patent No. 5 36 5 10 2 proposes a trench metal-oxygen half barrier Schottky (TMBS) rectifier. Among them, the theoretically superior breakdown voltage characteristics are achieved, which is achieved by a trench structure that allows the epitaxial / drift region of the trench structure to have a ii 抆 portion. The main charge carriers and the liner in the trench structure (1 ini ng) chargec .oup 1 ing of the metal of the insulating wall causes redistribution of the electric field _. (profile) under Schottky contact, has a proper doping concentration in the drift region, and selects an appropriate concentration In the case of the thickness of the oxide layer, the result of this change in the electric field profile caused the breakdown voltage to reach about 25 volts, which is significantly better than the ideal collapse parallel-plane rectifier 9.5 volts breakdown voltage. In addition, since the peak electric field of the metal-semiconductor contact in a TMBS rectifier is smaller than that of an ideal rectifier, the leakage current generated by it is also relatively small. Contrary to the results obtained by increasing the trench depth, increasing the oxide thickness reduces the breakdown voltage. However, when the trench depth exceeds a certain value, the breakdown voltage does not increase any more, that is, it does not exceed 25 volts. An earlier and apparently simpler way was discovered, Η-R. CHANG et al., In US Patent No. 4,982,260, describe a method for making a power rectifier with a trench, which is in the form of a Schottky contact area pin diode. It mentioned that Schottky diodes have lower forward voltage drop and faster turn-off speed than p-i-n diodes, at the cost of a high reverse leakage current that increases significantly as the reverse voltage value increases. Here, several individual trenches are formed between the P + regions and extend to the drift region, and include an anode electrode that conforms to form a Schottky contact region between each trench.

449861 V. Description of the invention (3) Between a part of the bottom electrode and the drift region "field oxide layer (fieid oxide layer)" is used to partially cover the edge of the rectifier active area (P + region) edge, which is used as A field plate that terminates the electric field generated during the operation of the element. Problems to be Solved The above-mentioned way to deal with the problem of tritium current in a Schottky diode or rectifier, although it provides its own advantages, still leaves room for improvement to achieve an efficient and simplified rectifier structure that can lead to The reduced pressure drop across the enemy state maintains high forward bias current density and minimizes reverse bias leakage current. The purpose of the present invention is to provide a Schottky diode or rectifier, which has a structure to reduce the on-state voltage drop across the rectifier during operation, but maintain a high forward bias current density and minimize Reverse bias leakage current. SUMMARY OF THE INVENTION According to the present invention, an improved diode or rectifier structure and manufacturing method thereof are specifically embodied by a Schottky diode or rectifier or other similar device, which includes a diode at the edge of the active area of the rectifier. An isolating trench filled with an insulator or a dielectric is formed in the epitaxial layer, and serves as a field plate for enhancing the termination of the electric field generated during the operation at noon. The

_4 4, .986 1 V. Description of the invention (4) The isolation ditch system forms a closed structure (C 1 s s C 0 nfi gur at i 〇η) around the drift region, so as to more effectively terminate the edge of the drift region. The electric field thus allows the electric field to be better concentrated in the drift region and to better stop the reverse current. In particular, the leakage current at the edges is limited to 0. Scheme. Simple 1. The features and advantages of these and other @ of the present invention are as follows The detailed description and accompanying drawings will become more clear, in which: Explanation of the drawings • The first diagram is a schematic diagram of the front, showing a rectifier structure according to the present invention. 0 The second diagram is a rectifier shown in the first diagram. The top view of the structure shows the closed structure of the dielectric trench according to the present invention. Current device 12 Base layer 14 Conductor layer 16 Epitaxial layer 18 Conductor layer 20 Barrier metal layer 22 Insulating layer 24 Dielectric 26 Detailed description of the preferred embodiment of the trench structure The present invention is directed to propose a kind of improved diode Or a rectifier structure such as the one in —Schottky rectifiers> and its manufacturing method, whereby the> isolation trench structure is formed in a crystal containing

"98S1, ______ V. Description of the invention (5) Layer $ 'and adjacent to the field oxide layer provided by the edge of the active area of the rectifier, the trench structure 2 forms a closed structure around the drift area and is filled with an insulator or dielectric This insulating isolation trench is used to enhance the effect of the electric field generated by the field plate termination element at the edges during operation. The first figure provides a first semiconductor in the rectifier 100 according to a preferred embodiment of the present invention. A first conductor layer 14 is formed on one surface of the N + base layer 1-2, and the bottom layer 2 is an ohmic contact as a cathode. Typically, the first conductor layer 14 is a heavy metal such as Chin / Ni / Silver (_ ^ 士 3 [ 1111111 / [11. | ^ 1 / with 1 '-^). The base layer 12 is preferably a silicon doped n + conductive type dopant, such as arsenic or antimony. First semiconductor ^ The opposite surface of the layer ^ grows a second semiconductor layer 16 and is lightly doped with a dopant of N_ conductive type, such as a phosphor. By selecting the concentration and thickness of the doping of the semiconductor layer 16 to support high The reverse voltage does not conduct current, so it acts as a drift region for the rectifier. A barrier metal layer 'for example, molybdenum (; 111〇1 ^ (^ 1111!]]) Is deposited on the other or upper surface of the epitaxial layer 6 to form a Schottky barrier contact 2 0' a Schottky A diode or rectifier is produced. A conductor layer 18 is deposited on the upper surface of the Schottky barrier layer 20 as the anode contact, typically a multilayer metal such as titanium / nickel / silver, or a single layer metal such as aluminum. Before the Schottky barrier layer 20, an insulating layer 22 such as silicon nitride, silicon oxide, silicon oxynitride, etc. can be formed on the edge of the active surface of the rectifier, that is, the upper surface of the epitaxial layer 16. The insulating layer 2 2 is a film grown or deposited on the epitaxial layer 16. The photoresist layer is deposited through known photomask technology and then patterned. The insulating layer 22 is used as a field plate to stop the device from working. Electricity generated when the anode and cathode are applied across a voltage

449861 V. Description of invention (6) Field. According to the adjacent structure 26 in the surface, the photoresist patterning (Reactive etching), #, the width is about 2 8. The non-isotropic rear ditch 26 is covered with glass and used to enhance the effect. According to the crystal layer surface or equivalent size rectifier, but current. The wording of the present invention is intended to furthermore, familiarize yourself with the possible changes in the technique (diode) ° After inventing the area around the absolute movement of the edge of the surface, use the known Ion Etching; trench structure 2 6 is 1 to 2 " Carved (anis 0) filled with insulators or nitrides, or plate 22 termination element trench structure 26 is formed on the edge layer 22 of the epitaxial layer 16. As shown in the second figure, the trench is a closed structure. During the manufacturing process In the method of, for example, reactive ions # 刻 -RI E) or wet lithography (WE lithography into the epitaxial layer 16 to a depth of about i and between the substrate 12 and the epitaxial layer 丨 6 The interface tropic etching) is better: then the dielectric 24, such as an oxide, aggregates its combination to form an insulation isolation trench. In the work, the invention of the electric field generated at the edge is at the edge of the active area of the Schottky rectifier. The surrounding ditch around the trench enables the construction of the same Schottky diode as the previous technology and produces a reduced on-state voltage drop across maintaining a high forward bias current density and minimizing reverse bias leakage Narrative It should be understood as the use of narrative in nature rather than language word limit. Although the invention has been described in terms of a preferred embodiment, those skilled in the art will readily apply these teachings to other aspects of the invention, such as fast recovery

4 49861 *

Page ίο

Claims (1)

449861 6. Scope of patent application 1. A rectifier comprising: a first semiconductor layer of a first conductivity type having a first surface and an opposite surface; a Schottky barrier contacting the first surface Defines an active region; a first electrode layer is conductively contacting the Schottky barrier contact; a second semiconductor layer having the first conductivity type has a resistivity greater than the first semiconductor layer, and Having a surface adjacent to the opposite surface of the first semiconductor layer along the active region and having another opposite surface; a second electrode layer conductively contacting the other opposite surface of the second semiconductor layer; and a trench Means are formed in the edge of the active region below the second electrode layer and in the first surface surrounding the active region, and contain insulating material to limit leakage current from the edge of the main region. 2. The rectifier according to item 1 of the patent application scope, wherein the insulating material fills the trench means and includes a dielectric. 3. The rectifier according to item 1 of the scope of patent application, wherein the insulating material is selected from the group consisting of oxides, polymers, glass and nitrides, and combinations thereof. 4. The rectifier according to item 1 of the scope of patent application, further comprising an oxide layer formed on the first surface of the edge of the active region by the trench means in between. 5. — Schottky diodes, including: Page 1244986 1_ 6. Scope of patent application—epitaxial layer with a Schottky barrier contact layer on one surface; a first electrode layer. The epitaxial layer is located on the epitaxial layer and covers the Schottky S contact. A substrate has a surface on which a second electrode is formed, and the other surface is bonded to a 5 mysterious crystal layer, an insulating layer is located on an edge portion of the surface of the worm crystal layer below the first electrode layer: And an isolation trench is formed in the epitaxial layer between the insulating layer and the Schottky barrier contact layer, and the electric field at the edge of the Schottky barrier contact layer terminates the diode in operation. The electric field is concentrated. 6. The Schottky diode as described in item 5 of the patent application scope, further comprising an insulating material filling the isolation trench. 7. The Schottky diode as described in item 6 of the scope of patent application, wherein the insulating material is selected from the group consisting of oxides, polymers, glass and nitrides and combinations thereof = 8. The Schottky diode as described in the scope item 5, wherein the isolation trench forms a closed structure D 9 around the Schottky barrier contact layer. The Schottky diode as described in the scope of claim 5 Wherein the insulating layer includes a field of oxide. 10. A method for manufacturing a rectifier, including the following steps: providing a first semiconductor layer of a first conductivity type having a first surface-surface and an opposite surface; forming a first electrode layer on the first The opposite surface of the semiconductor layer Page 13 ^ 4986 1 6. The scope of patent application; a second semiconductor layer that forms the first conductivity type and has a resistivity lower than that of the first semiconductor layer, has a first surface that contacts the first layer, And having another opposite surface; forming a Schottky barrier contact layer on the other opposite surface, defining an active area;-shaped, forming a trench in the edge of the active area and surrounding the first area of the active area Inside the opposite surfaces of the two semiconductor layers; filling the trench with an insulating material to limit leakage current from the edge of the active region; and forming a second electrode layer on the other opposite surface of the first semiconductor layer Extend to the trench and the Schottky barrier contact layer, and conductively contact the Schottky barrier contact layer. 11. The method according to item 10 of the scope of patent application, further comprising a step of forming an oxide layer on the other opposite surface of the edge of the active area with the trench in between. 12. The method of claim 10, wherein the insulating material is selected from the group consisting of oxides, polymers, glass and nitrides, and combinations thereof. 13. The method of claim 10, wherein the step of forming a second semiconductor layer includes growing an epitaxial layer on the first surface of the first semiconductor layer. > 14. The method according to item 13 of the scope of patent application, wherein the step of forming a trench includes etching a trench extending within the epitaxial layer to surround the main Page U 449861 Six 'patent application scope. 15 · A rectifier comprising:-a first semiconductor layer of a first conductive form having a first surface and a second surface; and a first electrode layer conductively contacting the first of the first semiconductor layer A surface; a second semiconductor layer of the first conductivity type having a higher resistivity than the first semiconductor layer, a third surface adjacent to the second surface of the first layer, and a fourth surface; -A Schottky barrier contact layer on the fourth surface, defining an active region, and a second electrode layer electrically conducting the Schottky barrier contact layer on the fourth surface; the improvements include: a A trench is formed in the edge of the active region below the second electrode layer and in the fourth surface surrounding the active region; and an insulating material fills the trench, so the leakage current from the edge of the active region is limited. 16. The rectifier according to item 15 of the scope of patent application, further comprising an oxide layer on the fourth surface of the edge of the active area with the trench located therebetween. 17. The rectifier according to item 15 of the scope of patent application, further comprising / including a film layer formed on the edge of the fourth surface by a material selected from the group consisting of silicon oxide, silicon nitride, and silicon oxynitride. Group. Page 15 4 4986 1_ VI. Patent Application Range 1 8. The rectifier described in item 15 of the patent application range, wherein the insulating material is selected from the group consisting of oxides, polymers, glass and nitrides, and combinations thereof. Group. : 19. The rectifier according to item 15 of the scope of patent application, wherein the Schottky barrier contact layer includes molybdenum. 20. The rectifier according to item 15 of the scope of the patent application, wherein the electrode includes an inscription, or a multi-metal titanium / nickel / silver. Page 16