阅读说明：本技术 一种肖特基二极管及其制造方法 (Schottky diode and manufacturing method thereof ) 是由 吴勐 郭昊鑫 杨旭 孙传帮 麻建国 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种肖特基二极管及其制造方法,所述二极管包括：衬底；制作于所述衬底一侧的外延层；制作于所述外延层一侧的P型保护环；制作于所述外延层一侧的氧化层,从器件边缘延伸到引线窗口边缘位置；制作于所述引线窗口一侧的势垒金属；制作于所述氧化层和势垒金属上的多层金属结构一,从P型保护环外侧向内侧覆盖；制作于所述多层金属结构一外侧的多层金属结构二,从多层金属结构一外层向内侧覆盖,中心区域露出多层金属结构一窗口；制作于所述多层金属结构二外侧钝化薄膜,从多层金属结构二外层向内覆盖,止于向内侧100um距离,本发明的肖特基二极管能够解决贴片烧结封装的肖特基二极管存在的PCT、金属迁移和焊料偏移导致的失效风险。(The invention discloses a Schottky diode and a manufacturing method thereof, wherein the diode comprises: a substrate; an epitaxial layer formed on one side of the substrate; the P-type protection ring is manufactured on one side of the epitaxial layer; the oxide layer is manufactured on one side of the epitaxial layer and extends from the edge of the device to the edge of the lead window; the barrier metal is manufactured on one side of the lead window; a first multilayer metal structure which is manufactured on the oxide layer and the barrier metal and covers from the outer side to the inner side of the P-type protection ring; a second multilayer metal structure which is manufactured on the outer side of the first multilayer metal structure and covers the outer layer of the first multilayer metal structure to the inner side, and a window of the first multilayer metal structure is exposed in the central area; the passivation film is manufactured on the outer side of the multilayer metal structure, covers the outer layer of the multilayer metal structure inwards, and stops at a distance of 100um towards the inner side.)

1. A Schottky diode and a manufacturing method thereof are characterized in that the diode comprises:

a substrate;

an epitaxial layer formed on one side of the substrate;

the P-type protection ring is manufactured on one side of the epitaxial layer;

the oxide layer is manufactured on one side of the epitaxial layer and extends from the edge of the device to the edge of the lead window;

the barrier metal is manufactured on one side of the lead window;

a first multilayer metal structure which is manufactured on the oxide layer and the barrier metal and covers from the outer side to the inner side of the P-type protection ring;

a second multilayer metal structure which is manufactured on the outer side of the first multilayer metal structure and covers the outer layer of the first multilayer metal structure to the inner side, and a window of the first multilayer metal structure is exposed in the central area;

the passivation film is manufactured on the outer side of the multilayer metal structure, covers inwards from the outer layer of the multilayer metal structure and stops at a distance of 100um towards the inner side.

2. The schottky diode and the method of manufacturing the same as claimed in claim 1, wherein the epitaxial layer and the substrate have N-and N + structures from top to bottom, respectively, and the N-structure resistivity is determined according to the product voltage range.

3. The schottky diode and method of claim 1 wherein the etching of the center of the first multilayer metal structure exposes the first multilayer metal structure.

4. The schottky diode and the method of claim 1 wherein the outer metal of the multilayer metal structure is silver metal in the present structure.

5. The schottky diode and the method of claim 1 wherein the multilayer metal structure is divided into an inner layer metal and an outer layer metal, the outer layer metal is aluminum metal in the structure, and the inner layer metal is used to adhere the first multilayer metal structure.

6. The schottky diode as claimed in claim 1, wherein the passivation film is silicon nitride.

Technical Field

The invention relates to the field of power semiconductor device manufacturing, in particular to a Schottky diode and a manufacturing method thereof.

Background

In the prior art, a passivation layer film is usually adopted to protect the schottky diode, and at present, the passivation layer mostly adopts structures such as silicon nitride, silicon oxynitride, polyimide, glass, phosphorosilicate glass and the like.

The surface roughness of the metal aluminum is high, the bonding capacity with the passivation film is good, but the passivation layer covering difficulty on the surface of the metal silver is high, the adhesion capacity of the silicon nitride on the surface of the metal silver is poor, and the problem of falling off of the passivation layer film is easy to occur. Polyimide has a much larger thermal expansion coefficient than silicon nitride, and is easily subjected to internal stress in a high-temperature process, and is easily converted into a glass state in a sintering process, so that soldering tin splashed on polyimide cannot be cleaned.

The frame and the front metal are easy to misplace and deviate in the sintering and packaging process, and if the deviating frame is welded at the terminal position of a chip, the risk of short circuit or large failure of electric leakage of a device exists in the long-term working process.

Therefore, there is a need to address the failure risk of the chip-sinter packaged schottky diode due to PCT, metal migration, and solder migration.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a Schottky diode and a manufacturing method thereof, and the invention adopts the technical scheme that:

a schottky diode and method of making the same, the diode comprising:

a substrate;

an epitaxial layer formed on one side of the substrate;

the P-type protection ring is manufactured on one side of the epitaxial layer;

the oxide layer is manufactured on one side of the epitaxial layer and extends from the edge of the device to the edge of the lead window;

the barrier metal is manufactured on one side of the lead window;

a first multilayer metal structure which is manufactured on the oxide layer and the barrier metal and covers from the outer side to the inner side of the P-type protection ring;

a second multilayer metal structure which is manufactured on the outer side of the first multilayer metal structure and covers the outer layer of the first multilayer metal structure to the inner side, and a window of the first multilayer metal structure is exposed in the central area;

the passivation film is manufactured on the outer side of the multilayer metal structure, covers inwards from the outer layer of the multilayer metal structure and stops at a distance of 100um towards the inner side.

Preferably, the epitaxial layer and the substrate are respectively of an N-structure and an N + structure from top to bottom, and the resistivity of the N-structure is determined according to the voltage range of the product.

Preferably, the center of the first multilayer metal structure is corroded to expose the first multilayer metal structure.

Preferably, the multilayer metal structure has a metal silver as the outer metal in the structure.

Preferably, the multilayer metal structure is divided into an inner layer metal and an outer layer metal, in the structure, the outer layer metal is metal aluminum, and the inner layer metal is used for adhering the first multilayer metal structure.

Preferably, the passivation film is silicon nitride.

The invention has the beneficial effects that:

the invention can solve the problems of the peeling of the passivation layer caused by poor adhesion of the silicon nitride passivation layer on the silver surface or the high-temperature leakage caused by tin bead embedding and large thermal expansion coefficient of the silver surface in the sintering process by using polyimide as the passivation layer, can effectively block the influence of water vapor and movable ions on products, prevents the failure risk caused by silver ion migration and sintering frame offset, and improves the reliability of the products.

Drawings

FIG. 1 is a schematic view of example 1;

FIG. 2 is a schematic view of example 2;

the reference symbols shown in the figures are: 101-substrate, 102-epitaxial layer, 103-oxide layer, 104-P type guard ring structure, 105-Schottky barrier structure, 106-multilayer metal structure I, 107-multilayer metal structure II, 108-passivation film and 109-back metal.

Detailed Description

The following describes the present design in detail with reference to the accompanying drawings.

A schottky diode and method of making the same, the diode comprising:

a substrate 101;

an epitaxial layer 102 formed on one side of a substrate 101;

a P-type guard ring formed on one side of the epitaxial layer 102;

an oxide layer 103 which is manufactured on one side of the epitaxial layer 102 and extends from the edge of the device to the edge of the lead window;

a barrier metal formed on one side of the lead window;

a first multilayer metal structure 106 which is manufactured on the oxide layer 103 and the barrier metal and covers from the outer side to the inner side of the P-type protection ring;

a second multilayer metal structure 107 which is manufactured on the outer side of the first multilayer metal structure 106 and covers the outer layer of the first multilayer metal structure 106 to the inner side, and a window of the first multilayer metal structure 106 is exposed in the central area;

and a passivation film 108 which is manufactured on the outer side of the second multilayer metal structure 107 and covers the outer layer of the second multilayer metal structure 107 inwards and stops at a distance of 100um from the inner side.

The epitaxial layer 102 and the substrate 101 are respectively of an N-structure and an N + structure from top to bottom, and the resistivity of the N-structure is determined according to the voltage range of a product.

Wherein, multilayer metal structure two 107 center corrosion exposes multilayer metal structure one 106 for the fixed soldering pad face forms inboard pit structure, and at the paster encapsulation soldering paste sintering and melts the in-process, the front frame can be from positioning chip central zone, plays the effect of welding and connection chip, prevents that the welding position skew from leading to the chip to have the internal stress, leads to the product electric leakage to exceed standard.

The outer layer metal of the multilayer metal structure I106 in the structure is metal silver, and the metal silver ensures that the surface mount device can be fully welded and combined with the frame in the sintering process.

The second multilayer metal structure 107 is divided into an inner layer metal and an outer layer metal, in the structure, the outer layer metal is metal aluminum, the inner layer metal is used for adhering the first multilayer metal structure 106, the metal aluminum is not infiltrated with soldering tin in the sintering process, the sputtering and adhesion of the sintering soldering tin are prevented, and the migration of silver ions of the first multilayer metal structure 106 can be blocked.

The passivation film 108 is made of silicon nitride, which can resist acid and alkali corrosion, and block water vapor and mobile ions.

Example 1

As shown in fig. 1, an epitaxial layer 102 is formed on one side of a substrate 101, which may be one of silicon, silicon carbide, sapphire, gallium nitride, or aluminum nitride.

An oxide layer 103 is formed on one side of the epitaxial layer 102.

And coating photoresist on the surface of the oxide layer 103, and corroding a P-type guard ring injection window on the surface of the oxide layer 103 through a photoetching mask.

After ion implantation and high temperature diffusion, the P-type guard ring structure 104 is formed.

And coating photoresist on the surface of the oxide layer 103 again, and corroding a lead window pattern on the surface of the oxide layer 103 through a photoetching mask.

A barrier metal is sputtered in the via area using a sputtering method to form a schottky barrier structure 105 through a high temperature alloy.

An evaporation process is used on the schottky barrier structure 105 to form a multi-layer metal structure one 106, and the outermost layer metal is silver.

And coating photoresist on the surface of the first multilayer metal structure 106, and corroding the surface of the first multilayer metal structure 106 to remove metal outside the welding area through a photoetching mask.

And forming a second multilayer metal structure 107 on the surface of the first multilayer metal structure 106 by using an evaporation process, wherein the outermost layer of the second multilayer metal structure is aluminum.

And coating photoresist on the surface of the second multilayer metal structure 107, corroding the surface of the second multilayer metal structure 107 through a photoetching mask, exposing the first multilayer metal structure 106 in the central welding area, and ensuring that the front frame and the center of the chip are aligned when the soldering paste melts in the packaging and sintering process. Meanwhile, the outer layer edge of the first multilayer metal structure 106 is covered by the second multilayer metal structure 107, and the oxide layer is exposed outside the second multilayer metal structure 107.

And depositing a layer of passivation film 108 of silicon nitride on the surface of the second multilayer metal structure 107 by using a PECVD method.

And coating photoresist on the surface of the passivation film 108, corroding the surface of the passivation film 108 through a photoetching mask, exposing the oxide layer on the outer side of the passivation film 108, covering the outer side edge of the second multilayer metal structure 107, and extending the passivation film 108 inwards by 100 microns.

Then, a substrate thinning process is performed on the opposite side of the substrate 101 to thin the chip to a desired thickness.

A back metal 109 is evaporated as a back electrode on the thinned side of the substrate 101 using an evaporation process.

Example 2

As shown in fig. 2, in this embodiment, based on embodiment 1, the edge length of the first multilayer metal structure 106 is shortened, the distance between the first multilayer metal structure 106 and the chip edge is extended, and the possibility of outward migration of the silver ions in the first multilayer metal structure 106 is reduced.