CN107256886A - Groove-type Schottky diode and preparation method thereof - Google Patents

Abstract

The invention relates to a trench Schottky diode and a manufacturing method thereof. The trench Schottky diode includes an N-type substrate, an N-type epitaxial layer formed on the surface of the N-type substrate, a plurality of grooves formed in the N-type epitaxial layer, and a plurality of grooves formed in each groove The oxide layer on the inner surface of the groove, the polysilicon formed in the groove and arranged on the surface of the oxide layer, the P-type implantation region formed on the surface of the N-type epitaxial layer between two adjacent grooves, and forming A metal layer on the oxide layer, the polysilicon and the P-type implanted region.

Description

Trench Schottky diode and manufacturing method thereof

【Technical field】

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

【Background technique】

Power diodes are key components of circuit systems, and are widely used in high-frequency inverters, digital products, generators, televisions and other civilian products, as well as satellite receivers, missiles and aircraft and other advanced weapon control systems and instrumentation equipment. Military occasions. Power diodes are expanding in two important directions: (1) to tens of millions or even tens of thousands of amperes, which can be applied to high-temperature arc wind tunnels, resistance welding machines, etc.; (2) reverse recovery time is getting shorter and shorter, showing Developing in the direction of ultra-fast, ultra-soft, and ultra-durable, it is not only used in rectification occasions, but also has different functions in various switching circuits. In order to meet the application requirements of low power consumption, high frequency, high temperature, and miniaturization, its withstand voltage, on-resistance, turn-on voltage drop, reverse recovery characteristics, high temperature characteristics, etc. are getting higher and higher.

Commonly used rectifier diodes, Schottky diodes, and PIN diodes are commonly used. Compared with each other, they have their own characteristics: the Schottky rectifier has a lower on-state voltage drop, a larger leakage current, and the reverse recovery time is almost zero. The PIN fast recovery rectifier has a faster reverse recovery time, but its on-state voltage drop is very high.

Trench Schottky diode, in this device, the electric field intensity distribution is changed by the electric field depletion, and the maximum value of the electric field intensity is transferred from the Schottky junction position to the inside of the silicon, effectively suppressing the reverse bias The Schottky barrier lowering effect appears, thereby reducing the reverse leakage current of the Schottky junction; on the other hand, the trench Schottky diode can also reduce the maximum value of the electric field intensity in the active region, thereby To achieve an increase in the reverse breakdown voltage of the diode, therefore, under the premise of maintaining the same breakdown voltage, an epitaxial layer with a relatively high doping concentration can be used to achieve a lower forward conduction voltage. However, how to improve the device performance of trench Schottky diodes is an important issue.

【Content of invention】

The invention proposes a trench Schottky diode and a manufacturing method thereof, which improves device performance.

A trench type Schottky diode, which includes an N-type substrate, an N-type epitaxial layer formed on the surface of the N-type substrate, a plurality of grooves formed in the N-type epitaxial layer, and formed in each The oxide layer on the inner surface of the groove, the polysilicon formed in the groove and arranged on the surface of the oxide layer, the P-type implanted region formed on the surface of the N-type epitaxial layer between two adjacent grooves, A metal layer formed on the oxide layer, the polysilicon and the P-type implanted region.

In one embodiment, the trench includes a first part and a second part located above the first part, the trench width of the second part is greater than the trench width of the first part, and the oxide layer forms In the inner surface of the groove of the first part and the groove of the second part.

In one embodiment, the polysilicon is located in the trench of the first portion, and the metal layer extends into the trench of the second portion.

In one embodiment, the P-type implantation region connects the oxide layers in the second parts of two adjacent trenches.

In one embodiment, the P-type implant region includes a first region and a second region, the second region is located above the first region, and the second region connects the two adjacent trenches The oxide layer in the second portion of the first region is located between the first portions of the two adjacent trenches.

A kind of manufacture method of trench Schottky diode, it comprises the steps:

An N-type substrate is provided, an N-type epitaxial layer is formed on the surface of the N-type substrate, and an oxide layer is prepared on the surface of the N-type epitaxial layer;

forming a first photoresist on the surface of the first oxide layer, and performing photolithography on the first photoresist to form a mask;

performing wet etching on the first oxide layer using a mask formed by the first photoresist;

Use the first photoresist and the first oxide layer as a mask to perform dry etching on the N-type epitaxial layer to form a plurality of grooves in the N-type epitaxial layer, and remove the first photoresist glue;

thermally oxidizing the N-type epitaxial layer to form a second oxide layer on the surface of the plurality of trenches;

forming polysilicon in the plurality of trenches and on the surface of the second oxide layer, and removing the first oxide layer;

Performing P-type ion implantation on the surface of the N-type epitaxial layer between the plurality of trenches to form a P-type implanted region; and

A metal layer is formed on the P-type implanted region, the second oxide layer and the polysilicon.

In one embodiment, polysilicon is formed in the plurality of trenches, and the step of removing the first oxide layer includes:

forming a polysilicon layer on the surface of the N-type epitaxial layer in and between the plurality of trenches; and

dry etching the polysilicon layer and the first oxide layer on the surface of the N-type epitaxial layer between the trenches to remove the polysilicon layer and the first oxide layer on the surface of the N-type epitaxial layer between the trenches and The polysilicon located in the trench is obtained.

In one embodiment, the groove includes a first portion and a second portion located above the first portion, the groove width of the second portion is larger than the groove width of the first portion, and the second oxide A layer is formed on the inner surface of the trenches of the first portion and in the trenches of the second portion.

In one embodiment, the polysilicon is located in the trench of the first part, the metal layer extends into the trench of the second part, and the P-type implantation region connects two adjacent trenches The second oxide layer in the second part.

In one embodiment, the P-type implant region includes a first region and a second region, the second region is located above the first region, and the second region connects the two adjacent trenches The second oxide layer in the second portion of the first region is located between the first portions of the two adjacent trenches.

On the basis of the structure of the traditional trench Schottky diode, the trench Schottky diode of the present invention performs ion implantation between the trenches to form a P-type implanted region to form an ohmic contact. Compared with the traditional trench type Schottky diode, the maximum field strength in the device of the present invention is still at the bottom edge of the lower trench of the device under the same voltage, but the value of the maximum field strength has decreased, and the ohm between the trenches The contact is protected by the P-type injection area to improve the withstand voltage capability, so the breakdown voltage of the device increases. Before the device breaks down, the leakage current appears in the trench and the ohmic contact position, but the trench Schottky diode of the present invention is compared with the traditional trench Schottky diode, and the electric field strength values at different positions are all decreased. Therefore, the Schottky barrier lowering effect can be effectively weakened, thereby achieving lower leakage current.

【Description of drawings】

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort, wherein:

FIG. 1 is a schematic structural diagram of a trench Schottky diode of the present invention.

FIG. 2 is a flow chart of the manufacturing method of the trench Schottky diode shown in FIG. 1 .

3-10 are structural schematic diagrams of each step of the manufacturing method shown in FIG. 2 .

[Description of main component symbols]

Trench Schottky diode 100; N-type substrate 101; N-type epitaxial layer 102; trench 103; oxide layers 104, 111; polysilicon 105; Part 1032; first area 1061; second area 1062 steps S1-S8

【detailed description】

The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of a trench Schottky diode 100 according to the present invention. The trench Schottky diode 100 includes an N-type substrate 101, an N-type epitaxial layer 102 formed on the surface of the N-type substrate 101, and a plurality of trenches 103 formed in the N-type epitaxial layer 102 , the oxide layer 104 formed on the inner surface of each trench 103, the polysilicon 105 formed in the trench 103 and disposed on the surface of the oxide layer 104, the N formed between two adjacent trenches 103 The P-type implanted region 106 on the surface of the epitaxial layer 102 , and the metal layer 107 formed on the oxide layer 104 , the polysilicon 105 and the P-type implanted region 106 .

The trench 103 includes a first portion 1031 and a second portion 1032 above the first portion 1031, the trench width of the second portion 1032 is greater than the trench width of the first portion 1031, and the oxide layer 104 is formed In the inner surface of the groove of the first part 1031 and the groove of the second part 1032 .

The polysilicon 105 is located in the trench of the first portion 1031, and the metal layer 107 extends into the trench of the second portion 1032.

The P-type implantation region 106 connects the oxide layer 104 in the second portion 1032 of two adjacent trenches 103 . The P-type implant region 106 includes a first region 1061 and a second region 1062, the second region 1062 is located above the first region 1061, and the second region 1062 connects the two adjacent trenches 103 The oxide layer 104 in the second portion 1032 of the first region 1061 is located between the first portions 1031 of the two adjacent trenches 103 .

Please refer to FIG. 2-FIG. 10. FIG. 2 is a flow chart of the manufacturing method of the trench Schottky diode 100 shown in FIG. 1, and FIG. The manufacturing method of the trench Schottky diode 100 includes the following steps S1-S8.

Step S1 , referring to FIG. 3 , provides an N-type substrate 101 , forms an N-type epitaxial layer 102 on the surface of the N-type substrate 101 , and prepares a first oxide layer 111 on the surface of the N-type epitaxial layer 102 . The first oxide layer 111 is a silicon dioxide layer.

Step S2 , please refer to FIG. 4 , forming a first photoresist on the surface of the first oxide layer 111 , and performing photolithography on the first photoresist to form a mask.

Step S3, please refer to FIG. 5 , use the mask formed by the first photoresist to perform wet etching on the first oxide layer 111, so as to form a plurality of A window 112 is etched into the trench of the first oxide layer 111 .

Step S4, please refer to FIG. 6 , using the first photoresist and the first oxide layer 111 as a mask to perform dry etching on the N-type epitaxial layer 102 to form a layer located in the N-type epitaxial layer 102 a plurality of trenches 103, the first photoresist is removed.

Step S5 , please refer to FIG. 7 , thermally oxidizes the N-type epitaxial layer 102 to form a second oxide layer (ie, the oxide layer 104 ) on the surface of the plurality of trenches 103 .

Step S6 , forming polysilicon in the plurality of trenches 103 and on the surface of the second oxide layer 104 , and removing the first oxide layer 111 . Specifically, referring to Fig. 8 and Fig. 9, described step S6 comprises:

Forming a polysilicon layer on the surface of the N-type epitaxial layer 102 in the plurality of trenches 103 and between the trenches 103; and

dry etching the polysilicon layer on the surface of the N-type epitaxial layer 102 between the trenches 103 and the first oxide layer 111 to remove the polysilicon layer on the surface of the N-type epitaxial layer 102 between the trenches 103 and the The first oxide layer 111 obtains the polysilicon 105 located in the trench 103 .

Step S7, please refer to FIG. 10 , perform P-type ion implantation on the surface of the N-type epitaxial layer 102 between the plurality of trenches 103 to form a P-type implanted region 106 .

Step S8 , please refer to FIG. 1 , forming a metal layer 107 on the P-type implanted region 106 , the second oxide layer 104 and the polysilicon 105 .

The trench Schottky diode 100 of the present invention is based on the traditional trench Schottky diode structure, and ion implantation is performed between the trenches 103 to form a P-type implanted region 106 to form an ohmic contact. Compared with the traditional trench Schottky diode, the maximum field strength in the device of the present invention is still at the bottom edge of the lower trench 103 of the device under the same voltage, but the value of the maximum field strength has been reduced, and between the trenches 103 The ohmic contact is protected by the P-type implant region 106 to improve the withstand voltage capability, so the breakdown voltage of the device increases. Before the device breaks down, the leakage current appears in the trench 103 and the ohmic contact position, but the trench Schottky diode 100 of the present invention is compared with the traditional trench Schottky diode, and the electric field intensity values at different positions are all different. Decrease, so the Schottky barrier lowering effect can be effectively weakened, thereby achieving lower leakage current.

What has been described above is only the embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements can be made without departing from the creative concept of the present invention, but these all belong to the present invention. scope of protection.

Claims (10)

1. a kind of groove-type Schottky diode, it is characterised in that：The groove-type Schottky diode includes N-type substrate, shape The N-type epitaxy layer on N-type substrate surface, the multiple grooves being formed in the N-type epitaxy layer described in Cheng Yu, it is formed at each groove The oxide layer of inner surface, be formed in the groove and be arranged at it is described oxidation layer surface polysilicon, be formed at adjacent two The p-type injection zone on the N-type epitaxy layer surface between individual groove and it is formed at the oxide layer, the polysilicon and the p-type Metal level on injection zone.

2. groove-type Schottky diode as claimed in claim 1, it is characterised in that：The groove includes Part I and position Part II above the Part I, the groove width of the Part II is more than the ditch groove width of the Part I Degree, the oxide layer is formed in the groove of the inner surface of the Part I groove and the Part II.

3. groove-type Schottky diode as claimed in claim 2, it is characterised in that：The polysilicon is located at described first In the groove divided, the metal level is extended in the groove of the Part II.

4. groove-type Schottky diode as claimed in claim 2, it is characterised in that：The p-type injection region connection is adjacent Oxide layer in the Part II of two grooves.

5. groove-type Schottky diode as claimed in claim 4, it is characterised in that：The p-type injection region includes the firstth area Domain and second area, the second area are located above the first area, described adjacent two of second area connection Oxide layer in the Part II of groove, the first area is located between the Part I of two adjacent grooves.

6. a kind of preparation method of groove-type Schottky diode, it comprises the following steps：

N-type substrate is provided, N-type epitaxy layer is formed on the N-type substrate surface, oxide layer is prepared on the N-type epitaxy layer surface；

In described first oxidation layer surface the first photoresist of formation, and photoetching is carried out to first photoresist, form mask；

Wet etching is carried out to first oxide layer using the mask of first photoresist formation；

Dry etching is carried out using first photoresist and first oxide layer to the N-type epitaxy layer as mask to be formed Multiple grooves in the N-type epitaxy layer, remove the first photoresist；

Thermal oxide is carried out to the N-type epitaxy layer so as in the multiple flute surfaces the second oxide layer of formation；

In the multiple groove and it is described second oxidation layer surface formation polysilicon, remove the first oxide layer；

N-type epitaxy layer surface between the multiple groove carries out p-type ion implanting formation p-type injection zone；And

Metal level is formed on the p-type injection zone, second oxide layer and the polysilicon.

7. the preparation method of groove-type Schottky diode as claimed in claim 6, it is characterised in that：In the multiple groove Middle formation polysilicon, the step of removing the first oxide layer includes：

N-type epitaxy layer surface in the multiple groove and between groove forms polysilicon layer；And

The polysilicon layer on the N-type epitaxy layer surface between groove described in dry etching and first oxide layer are described so as to remove The polysilicon layer on the N-type epitaxy layer surface between groove and first oxide layer simultaneously obtain the polycrystalline being located in groove Silicon.

8. the preparation method of groove-type Schottky diode as claimed in claim 6, it is characterised in that：The groove includes the A part and the Part II above the Part I, the groove width of the Part II are more than the Part I Groove width, second oxide layer is formed at the inner surface of the Part I groove and the groove of the Part II In.

9. the preparation method of groove-type Schottky diode as claimed in claim 6, it is characterised in that：The polysilicon is located at In the groove of the Part I, the metal level is extended in the groove of the Part II, and the p-type injection region connects phase The second oxide layer in the Part II of two adjacent grooves.

10. the preparation method of groove-type Schottky diode as claimed in claim 6, it is characterised in that：The p-type injection region Including first area and second area, the second area is located above the first area, and the second area connection is described The second oxide layer in the Part II of two adjacent grooves, the first area is located at the of two adjacent grooves Between a part.