CN107946374A - A kind of Schottky rectifier and manufacture method with surface impurity concentration regulatory region - Google Patents

Abstract

The invention discloses a kind of Schottky rectifier and manufacture method with surface impurity concentration regulatory region；The Schottky rectifier with surface impurity concentration regulatory region includes the first conductivity type substrate of heavy doping layer, the first conductive type epitaxial layer, the second conduction type protection ring region, the first conduction type surface impurity concentration regulatory region, field dielectric layer, anode metal layer and cathode metal layer is lightly doped.The Schottky rectifier and its manufacture method with surface impurity concentration regulatory region, can make obtained product keep high breakdown reverse voltage, on the premise of the characteristic such as low forward voltage drop and high impact-resistant reliability, also have the advantages that low-leakage current.

Description

A Schottky rectifier with a surface impurity concentration adjustment region and its manufacturing method

technical field

The invention relates to the technical field of power semiconductor power electronic devices, in particular to a Schottky rectifier with a surface impurity concentration adjustment region and a manufacturing method.

Background technique

Power semiconductor rectifiers are widely used in power converters and power supplies. Two common semiconductor rectifier structures are PIN rectifiers and Schottky rectifiers.

Among them, the PIN rectifier has a large forward voltage drop and a long reverse recovery time, but has a small leakage and has excellent high temperature stability. It is mainly used in the medium and high voltage range above 300V.

Schottky rectifiers are mainly used in the medium and low voltage range below 200V, especially in the 100V voltage level. The Schottky rectifier has a small forward voltage drop and a short reverse recovery time, but has a high reverse leakage current and poor high temperature reliability.

In the practical application of Schottky rectifiers, high reverse breakdown voltage, low forward voltage drop, low leakage current and high reliability have always been the performance goals pursued by products. In a typical Schottky rectifier that has been disclosed, in order to achieve high shock resistance reliability, a layer of surface high impurity concentration region with an impurity concentration higher than that of the epitaxial layer is generally formed on the surface of the active region. Such a Schottky rectifier has high shock resistance reliability, but it is precisely because of the existence of a high impurity concentration region on the surface that its leakage current becomes larger.

Contents of the invention

The purpose of the present invention is to solve the problems of large leakage current in the prior art, and propose a Schottky rectifier with low leakage current under the premise of maintaining high reverse breakdown voltage, low forward voltage drop and high impact resistance reliability. advantage device.

The technical solution adopted to realize the purpose of the present invention is as follows, a Schottky rectifier with a surface impurity concentration adjustment region, which is characterized in that: it includes a heavily doped first conductive type substrate layer, a lightly doped first conductive type Type epitaxial layer, second conductivity type guard ring region, first conductivity type surface impurity concentration adjustment region, field dielectric layer, anode metal layer and cathode metal layer.

The heavily doped first conductive type substrate layer covers the cathode metal layer.

The lightly doped first conductive type epitaxial layer covers the heavily doped first conductive type substrate layer.

Both the guard ring region of the second conductivity type and the surface impurity concentration adjustment region of the first conductivity type cover part of the surface above the epitaxial layer of the lightly doped first conductivity type. The upper surfaces of the guard ring region of the second conductivity type and the surface impurity concentration adjustment region of the first conductivity type are coplanar.

The field dielectric layer covers part of the surface on the epitaxial layer of the first conductivity type.

The anode metal layer covers the dielectric layer and the first conductivity type surface impurity concentration adjustment region. The anode metal layer also covers part of the surface above the second conductivity type guard ring area.

A method for manufacturing a Schottky rectifier with a surface impurity concentration adjustment region, characterized in that it comprises the following steps:

1) Covering the lightly doped epitaxial layer of the first conductivity type on the heavily doped first conductivity type substrate layer.

2) Covering the field dielectric layer on the lightly doped epitaxial layer of the first conductivity type.

3) Using the first mask layer to form the second conductivity type guard ring region of the closed ring structure. Its annular surrounding part is the active area.

4) Etching the field dielectric layer above the active region by using the second mask layer.

5) Forming an implantation window on a part of the surface above the active region by using the third mask layer.

6) Low-energy implantation of impurities of the first conductivity type into the implantation window formed in step 5).

7) After removing the photoresist, high temperature annealing is performed to form the first conductivity type surface impurity concentration adjustment region.

8) Forming an anode metal layer on the dielectric layer, the upper surface of the first conductivity type surface impurity concentration adjustment region and the part of the surface above the second conductivity type guard ring region.

9) Covering the cathode metal layer on the lower surface of the heavily doped substrate layer of the first conductivity type.

Further, the guard ring area of the second conductivity type is a closed ring structure. The middle area surrounded by the ring is the active area.

Further, the field dielectric layer is located outside the active area. The first conductivity type surface impurity concentration adjustment region is located inside the active region.

Further, the first conductivity type surface impurity concentration adjustment region is an independent connected region or a plurality of independent connected regions.

The surface impurity concentration adjustment region of the first conductivity type may or may not be in contact with the guard ring region of the second conductivity type.

The first conductivity type surface impurity concentration adjustment region covers a part of the active region.

Further, the field dielectric layer also covers part of the surface above the guard ring region of the second conductivity type.

The field dielectric layer is not in contact with the first conductivity type surface impurity concentration adjustment region.

Further, the anode metal layer includes a conventional metal layer and a Schottky barrier layer. The Schottky barrier layer is located between the surface of the silicon layer and the conventional metal layer. The Schottky barrier layer is made of an alloy formed of platinum, nickel platinum and other metals and silicon.

The technical effect of the present invention is unquestionable. The Schottky rectifier with the surface impurity concentration adjustment region and its manufacturing method in the present invention can maintain high reverse breakdown voltage, low forward voltage drop and high rectifier. Under the premise of anti-shock reliability, it has the advantage of low leakage current.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of a new device 1 according to an embodiment of the present invention;

Fig. 2 is a schematic cross-sectional structure diagram of a new device 2 according to an embodiment of the present invention;

Fig. 3 is the comparison schematic diagram of the forward characteristic curve of the new device of the embodiment of the present invention;

Fig. 4 is the comparative schematic diagram of the reverse characteristic curve of the new device of the embodiment of the present invention;

In the figure: heavily doped first conductivity type substrate layer 10, lightly doped first conductivity type epitaxial layer 20, second conductivity type guard ring region 21, first conductivity type surface impurity concentration adjustment region 22, field dielectric layer 30, Anode metal layer 40 and cathode metal layer 50 .

Detailed ways

The present invention will be further described below in conjunction with the examples, but it should not be understood that the scope of the subject of the present invention is limited to the following examples. Without departing from the above-mentioned technical ideas of the present invention, various replacements and changes made according to common technical knowledge and conventional means in this field shall be included in the protection scope of the present invention.

Example 1:

A Schottky rectifier with a surface impurity concentration adjustment region, characterized in that it includes a heavily doped first conductivity type substrate layer 10, a lightly doped first conductivity type epitaxial layer 20, and a second conductivity type guard ring region 21 , the first conductivity type surface impurity concentration adjustment region 22 , the field dielectric layer 30 , the anode metal layer 40 and the cathode metal layer 50 .

The heavily doped first conductive type substrate layer 10 covers the cathode metal layer 50 .

The lightly doped first conductive type epitaxial layer 20 covers the heavily doped first conductive type substrate layer 10 .

Both the guard ring region 21 of the second conductivity type and the surface impurity concentration adjustment region 22 of the first conductivity type cover part of the surface on the epitaxial layer 20 of the lightly doped first conductivity type. The upper surfaces of the guard ring region 21 of the second conductivity type and the surface impurity concentration adjustment region 22 of the first conductivity type are coplanar. The guard ring region 21 of the second conductivity type is a closed ring structure. The middle area surrounded by the ring is the active area.

The first conductivity type surface impurity concentration adjustment region 22 is an independent connected region or a plurality of independent connected regions. The surface impurity concentration adjustment region 22 of the first conductivity type may or may not be in contact with the guard ring region 21 of the second conductivity type. The first conductivity type surface impurity concentration adjustment region 22 covers a part of the active region.

The field dielectric layer 30 covers part of the surface of the epitaxial layer 20 of the first conductivity type. The field dielectric layer 30 is located outside the active area. The first conductivity type surface impurity concentration adjustment region 22 is located inside the active region. The field dielectric layer 30 also covers part of the surface above the guard ring region 21 of the second conductivity type. The field dielectric layer 30 is not in contact with the first conductivity type surface impurity concentration adjustment region 22 .

The anode metal layer 40 covers the dielectric layer 30 and the first conductivity type surface impurity concentration adjustment region 22 . The anode metal layer 40 also covers part of the surface above the second conductivity type guard ring region 21 .

The anode metal layer 40 includes a conventional metal layer and a Schottky barrier layer. The Schottky barrier layer is located between the surface of the silicon layer and the conventional metal layer. The Schottky barrier layer is made of an alloy formed of platinum, nickel platinum and other metals and silicon.

Example 2:

A method for manufacturing a Schottky rectifier with a surface impurity concentration adjustment region in embodiment 1, is characterized in that it comprises the following steps:

1) Covering the lightly doped first conductivity type epitaxial layer 20 on the heavily doped first conductivity type substrate layer 10 .

2) Covering the field dielectric layer 30 on the lightly doped epitaxial layer 20 of the first conductivity type.

3) Forming a guard ring region 21 of the second conductivity type in a closed ring structure by using the first mask layer. Its annular surrounding part is the active area.

4) Etching the field dielectric layer 30 above the active region by using the second mask layer.

5) Forming an implantation window on a part of the surface above the active region by using the third mask layer.

6) Low-energy implantation of impurities of the first conductivity type into the implantation window formed in step 5).

7) After removing the photoresist, perform high temperature annealing to form the first conductivity type surface impurity concentration adjustment region 22 .

8) Form an anode metal layer 40 on the dielectric layer 30 , the upper surface of the first conductivity type surface impurity concentration adjustment region 22 and the part of the surface above the second conductivity type guard ring region 21 .

9) Covering the cathode metal layer 50 on the lower surface of the heavily doped substrate layer 10 of the first conductivity type.

The selection of typical parameters in the main steps is:

The first conductivity type is N type, and the second conductivity type is P type.

The N+ type substrate layer is an arsenic impurity substrate with a doping concentration above the 19th power, and the N-type epitaxial layer is a phosphorus impurity epitaxial layer with an impurity concentration of 15 to 16 power;

The P-type guard ring region is formed by high-temperature annealing after boron implantation with a dosage of 13 powers;

The N-type surface impurity concentration adjustment region is formed by high-temperature annealing after phosphorus implantation with a dose of 12th power and an energy of about 60KeV;

The Schottky barrier layer is composed of platinum, nickel platinum and other metals and silicon alloys;

The field dielectric layer is about 1 micron.

Example 3:

Using the method in Example 2, a Schottky rectifier with a surface impurity concentration adjustment region is manufactured; wherein, the first conductivity type is N-type, and the second conductivity type is P-type.

As shown in Figure 1, the surface impurity concentration adjusted high-voltage Schottky rectifier produced in this embodiment is characterized in that it includes a heavily doped first conductivity type substrate layer 10, a lightly doped first conductivity type epitaxial layer 20, a second The second conductivity type guard ring region 21 , the first conductivity type surface impurity concentration adjustment region 22 , the field dielectric layer 30 , the anode metal layer 40 and the cathode metal layer 50 .

The N-type epitaxial layer 20 covers the N+ type substrate layer 10 . The N+ type substrate layer 10 is an arsenic impurity substrate with a doping concentration above the 19th power. The N-type epitaxial layer 20 is a phosphorus impurity epitaxial layer with an impurity concentration of 2×10 ¹⁵ cm ⁻³ .

The P-type guard ring region 21 covers a part of the N-type epitaxial layer 20 . The P-type guard ring region 21 is a closed ring structure, and the middle region surrounded by it is called an active region. The P-type guard ring region 21 is formed by boron implantation at a dose of 3×10 ¹³ cm ⁻² and then annealed at 1100°C.

The N-type surface impurity concentration adjustment region 22 is composed of a plurality of independent connected regions; the N-type surface impurity concentration adjustment region 22 is located in a part of the N-type epitaxial layer 20, and is located in the active region, but there is no Covers the entire surface of the active region and is in contact with the P-type guard ring region 21; the N-type surface impurity concentration adjustment region 22 is implanted with phosphorus with a dose of 1×10 ¹² cm ^-2 and an energy of 100KeV, and then undergoes high-temperature annealing form.

The field dielectric layer 30 covers part of the surface of the N-type epitaxial layer 20 . The field dielectric layer 30 is located outside the active area. The field dielectric layer 30 also covers part of the surface above the P-type guard ring region 21 ; the field dielectric layer 30 is not in contact with the N-type surface impurity concentration adjustment region 22 . The field dielectric layer 30 is about 1 micron.

The anode metal layer 40 includes a conventional metal layer and a Schottky barrier layer; the Schottky barrier layer is located between the surface of the silicon layer and the conventional metal layer; the Schottky barrier layer is formed of platinum and silicon alloy composition. The anode metal layer 40 also covers the field dielectric layer 30 .

The cathode metal layer 50 is located under the N+ type substrate layer 10 .

Example 4:

The Schottky rectifier with the surface impurity concentration adjustment region was fabricated by the fabrication method in Example 2. Wherein, the first conductivity type is N type, and the second conductivity type is P type.

As shown in Figure 2, the surface impurity concentration adjustment high-voltage Schottky rectifier produced in this embodiment is characterized in that it includes a heavily doped first conductivity type substrate layer 10, a lightly doped first conductivity type epitaxial layer 20, a second The second conductivity type guard ring region 21 , the first conductivity type surface impurity concentration adjustment region 22 , the field dielectric layer 30 , the anode metal layer 40 and the cathode metal layer 50 .

The N-type epitaxial layer 20 covers the N+ type substrate layer 10 . The N+ type substrate layer 10 is an arsenic impurity substrate with a doping concentration above the 19th power. The N-type epitaxial layer 20 is a phosphorus impurity epitaxial layer with an impurity concentration of 2×10 ¹⁵ cm ⁻³ .

The P-type guard ring region 21 covers a part of the N-type epitaxial layer 20 . The P-type guard ring region 21 is a closed ring structure, and the middle region surrounded by it is called an active region. The P-type guard ring region 21 is formed by boron implantation at a dose of 3×10 ¹³ cm ⁻² and then annealed at 1100°C.

The N-type surface impurity concentration adjustment region 22 is located in a part of the N-type epitaxial layer 20, and is located in the active region, and is not in contact with the P-type guard ring region 21; the N-type surface impurity concentration adjustment region 22 It is formed by high-temperature annealing after implanting phosphorus with a dose of 1×10 ¹² cm ^-2 and an energy of 100KeV.

The field dielectric layer 30 covers part of the surface of the N-type epitaxial layer 20 . The field dielectric layer 30 is located outside the active area. The field dielectric layer 30 also covers part of the surface above the P-type guard ring region 21 ; the field dielectric layer 30 is not in contact with the N-type surface impurity concentration adjustment region 22 . The field dielectric layer 30 is about 1 micron.

The anode metal layer 40 includes a conventional metal layer and a Schottky barrier layer; the Schottky barrier layer is located between the surface of the silicon layer and the conventional metal layer; the Schottky barrier layer is formed of platinum and silicon alloy composition. The anode metal layer 40 also covers the field dielectric layer 30 .

The cathode metal layer 50 is located under the N+ type substrate layer 10 .

Figure 3 shows the forward characteristic curve of the new device of the embodiment. Compared with the conventional device, under the same anode current, the forward conduction voltage of the new device is almost the same as that of the conventional device, so the new device maintains the characteristics of low forward voltage drop.

Figure 4 shows the reverse characteristic curve of the new device of the embodiment. It can be seen that the new device maintains a high reverse breakdown voltage characteristic and has a lower leakage current compared with the conventional device.

Claims (7)

1. A kind of 1. Schottky rectifier with surface impurity concentration regulatory region, it is characterised in that：It is conductive including heavy doping first Type substrates layer (10), be lightly doped the first conductive type epitaxial layer (20), the second conduction type protection ring region (21), the first conduction Type surface impurity concentration regulatory region (22), field dielectric layer (30), anode metal layer (40) and cathode metal layer (50)；

   The first conductivity type substrate of heavy doping layer (10) is covered on cathode metal layer (50)；

   First conductive type epitaxial layer (20) that is lightly doped is covered on heavy doping the first conductivity type substrate layer (10)；

   The second conduction type protection ring region (21) and the first conduction type surface impurity concentration regulatory region (22) are covered in The part surface on the first conductive type epitaxial layer (20) is lightly doped；The second conduction type protection ring region (21), first The upper surface of conduction type surface impurity concentration regulatory region (22) is coplanar；

   The field dielectric layer (30) is covered in the part surface on the first conductive type epitaxial layer (20)；

   The anode metal layer (40) be covered in dielectric layer (30) and the first conduction type surface impurity concentration regulatory region (22) it On；The anode metal layer (40) is also covered in the part surface on the second conduction type protection ring region (21).
2. 2. a kind of manufacture method of the Schottky rectifier with surface impurity concentration regulatory region, it is characterised in that including following Step：

   1) the first conductive type epitaxial layer (20) will be lightly doped to be covered on heavy doping the first conductivity type substrate layer (10)；

   2) field dielectric layer (30) is covered in and be lightly doped on the first conductive type epitaxial layer (20)；

   3) the second conduction type protection ring region (21) of closed annular structure is formed using the first mask layer；Its annular circle segment For active area；

   4) the field dielectric layer (30) of the active region is etched using the second mask layer；

   5) using the 3rd mask layer, square part surface forms injection window on the active area；

   6) impurity of the first conduction type is injected to the injection window low energy that step 5) is formed；

   7) after removing photoresist, high annealing forms the first conduction type surface impurity concentration regulatory region (22)；

   8) protected in dielectric layer (30), the upper surface of the first conduction type surface impurity concentration regulatory region (22) and the second conduction type Anode metal layer (40) is formed on part surface on retaining ring area (21)；

   9) cathode metal layer (50) is covered on the lower surface of heavy doping the first conductivity type substrate layer (10).
3. A kind of 3. Schottky rectifier with surface impurity concentration regulatory region according to claim 1, it is characterised in that： The second conduction type protection ring region (21) is the loop configuration of closed form；The intermediate region that annular is surrounded is active area.
4. 4. a kind of Schottky rectifier with surface impurity concentration regulatory region according to claim 1 or 3, its feature exist In：The field dielectric layer (30) is located at outside active area；The first conduction type surface impurity concentration regulatory region (22) is located at Inside active area.
5. 5. a kind of Schottky rectifier with surface impurity concentration regulatory region according to claim 1 or 3, its feature exist In：The first conduction type surface impurity concentration regulatory region (22) is an independent connected region or multiple independent connections Region；

   The first conduction type surface impurity concentration regulatory region (22) can contact with the second conduction type protection ring region (21), It can not also contact；

   The first conduction type surface impurity concentration regulatory region (22) is covered in the subregion of active area.
6. A kind of 6. Schottky rectifier with surface impurity concentration regulatory region according to claim 1, it is characterised in that： The field dielectric layer (30) is also covered in the part surface on the second conduction type protection ring region (21)；

   The field dielectric layer (30) does not contact with the first conduction type surface impurity concentration regulatory region (22).
7. 7. a kind of Schottky rectifier and manufacturer with surface impurity concentration regulatory region according to claim 1 or 2 Method, it is characterised in that：The anode metal layer (40) includes conventional metal layer and schottky barrier layer；The schottky barrier layer Between silicon surface and conventional metal layer；The alloy structure that metal and the silicon such as the schottky barrier layer You platinum, Nie platinum are formed Into.