CN104183494B - Trench type power metal oxide semiconductor structure and forming method thereof - Google Patents

Abstract

The invention discloses a trench power metal oxide semiconductor structure and a forming method thereof. The method for forming the trench type power metal oxide semiconductor structure comprises the following steps: firstly, an isolation trench is formed, then two doping layers with different doping concentrations are formed, the two doping layers are connected and located on the periphery of the isolation trench, and an isolation structure is formed and located in the isolation trench. Wherein, the two doped layers are connected and positioned at the periphery of the isolation trench, and the interface profile can be formed by ion implantation control, thereby effectively relieving the distribution and conduction loss of the slow electric field.

Description

Trench Power Metal Oxide Semiconductor Structure and Formation Method

technical field

The present invention relates to a trench type power metal oxide semiconductor structure and its forming method, in particular to a trench type power metal oxide semiconductor structure and its forming method through repeated ion implantation to control the contour shape of the interface.

Background technique

In the application field of power semiconductors, withstand voltage capability and low impedance performance are very important performance indicators. Traditional methods cannot control the junction profile, so it is impossible to manufacture higher withstand voltage capability and low impedance.

Contents of the invention

The present invention provides a method for forming a trench-type power metal oxide semiconductor structure, comprising: first forming an isolation trench, and then forming two doped layers with different doping concentrations, and the two doped layers are connected to each other on the isolation trench The periphery of the trench, and an isolation structure is formed in the isolation trench.

In one embodiment, the step of forming the isolation trench in the present invention further includes: forming an epitaxial layer, then forming a gate trench in the epitaxial layer, and then forming a gate structure in the gate trench , and then forming a body region around the periphery of the gate structure, and the isolation trench is located outside the body region.

In one embodiment, forming an isolation trench and forming two doped layers with different doping concentrations in the present invention includes: forming a first isolation trench; forming a first doped layer located at the first isolation The periphery of the trench; etching the first doped layer under the isolation trench to form a second isolation trench; and forming a second doped layer located at the periphery of the second isolation trench.

In one embodiment, the cross-sectional area of the first isolation trench of the present invention is larger than the cross-sectional area of the second isolation trench.

In one embodiment, the two doped layers of the present invention are formed by ion implantation with different angles at different positions.

In one embodiment, the two doped layers of the present invention are formed from top to bottom and the concentration is from light to thick.

The present invention also provides a trench type power metal oxide semiconductor structure, comprising: an isolation trench; an isolation structure located in the isolation trench; and two doped layers with different doping concentrations, and the two doped layers The layer connection is located at the periphery of the isolation trench.

In an embodiment, the present invention further includes: an epitaxial layer; a gate trench located in the epitaxial layer; a gate structure located in the gate trench; a body region surrounding the periphery of the gate structure; Wherein the isolation trench is located outside the body region, and the depth of the isolation trench is higher than that of the gate structure.

In one embodiment, the isolation trench of the present invention includes a first isolation trench and a second isolation trench connected to each other, and the two doped layers are correspondingly formed in the first isolation trench and the second isolation trench Groove perimeter.

In one embodiment, the cross-sectional area of the first isolation trench of the present invention is larger than the cross-sectional area of the second isolation trench.

In one embodiment, the two doped layers of the present invention are formed at different positions by ion implantation with different angles.

In one embodiment, the two doped layers of the present invention are formed from top to bottom and the concentration is from light to thick.

In the trench type power metal oxide semiconductor structure and its forming method of the present invention, the interface profile outside the sidewall of the trench is formed repeatedly. This interface profile can be controlled by the amount of implanted ions to form a wide and narrow design change. When the oxide is backfilled to the inside of the trench, the metal oxide semiconductor (MOSFET) will use the potential effect of this region to form charges during reverse bias operation. Balance (Charge Balance) and reduce the surface electric field effect (RESURF), so that a gentler electric field distribution can be formed in the trench and sidewall electric field, so as to use less space and more efficiently obtain higher potential integration and more Low conduction loss (RON) performance, and this principle can also be used to optimize the resistance and thickness of the required epitaxial layer to reduce the conduction loss more effectively, thereby reducing the conduction loss of components.

The above summary and the following detailed description are exemplary in nature, and are intended to further illustrate the patent scope of the present invention. Other purposes and advantages of the present invention will be described in the subsequent description and accompanying drawings.

Description of drawings

1A to 1J show an embodiment of a method for forming a trench power metal oxide semiconductor structure of the present invention;

Another trench type power metal oxide semiconductor structure of the present invention shown in FIG. 2 ;

Another trench type power metal oxide semiconductor structure of the present invention shown in FIG. 3 ;

The trench type power metal oxide semiconductor structure of the present invention shown in FIG. 4 performs ion implantation at an oblique angle;

Another trench type power metal oxide semiconductor structure of the present invention shown in FIG. 5;

FIG. 6 shows another trench power metal oxide semiconductor structure of the present invention.

detailed description

The main technical feature of the present invention is that at least two doped layers are connected repeatedly to form the interface profile outside the side wall of the trench. And this interface profile can be controlled by the amount of implanted ions (i.e. concentration) to form a design change in width and shape, so as to achieve a gentler electric field distribution in the trench and sidewall electric field, so that the conduction loss can be more effectively reduced, and then reduced. Component conduction loss. The design of this part can be applied to the device region or the trench of the termination region of the metal oxide semiconductor structure to control the amount of implanted ions to achieve a specific interface profile to effectively achieve the withstand voltage and low impedance effect.

1A-1J show an embodiment of the method for forming the trench power metal oxide semiconductor structure of the present invention. In an embodiment where it is applied to the device area, the grooves in the peripheral or both sides of the terminal area can also have similar applications.

First, as shown in FIG. 1A , an epitaxial layer (Epi) 12 is grown on a substrate (Substrate) 10 . Next, a gate trench 14 is formed in the epitaxial layer 12 in FIG. 1B , and a gate dielectric layer 16 is grown inside the gate trench 14 . Then, a gate structure 18 is formed inside the gate trench 14 in FIG. 1C, where polysilicon is deposited (Poly Depostion) to the inside of the gate trench 14 and the upper part of the epitaxial layer 12, and then etched back ( Etch back) removes the deposited polysilicon on the epitaxial layer 12 , only retains the polysilicon inside the gate trench 14 , and forms the gate structure 18 inside the gate trench 14 .

Next, as shown in FIG. 1D , a body region 20 is formed around the periphery of the gate structure 18 , wherein the body region 20 is, for example, a P-type conductivity type ion implantation method, which is different from the use of the N-type conductivity type epitaxial layer 12 . Next, as shown in FIG. 1E , a first isolation trench 22 is formed, located outside the body region 20 , wherein the formation of the first isolation trench 22 , for example, can be preceded by a mask layer 24 covering the gate structure 18 and the body region. 20 , and then etch the body region 20 to form the first isolation trench 22 . The first isolation trench 22 is then ion-implanted into the epitaxial layer 12 with a first concentration (for example, represented by P ⁻ here) to form the first doped layer 26, and then as shown in the direction of the vertical downward arrow 27 Drive (Drive-In; D/I) mode, make the first doped layer 26 of P ^- diffuse to left and right up and down, the first doped layer 26 of P ^- is diffused to the periphery of the first isolation trench 22, the peripheral part is for example for the bottom and bottom sides.

Next, as shown in FIG. 1F ^, the first doped layer 26 of P- is etched downward in the original first isolation trench 22, or further etched to the epitaxial layer 12, so as to expand the first isolation trench 22 to the second isolation trench 28, and then perform ion implantation with different doping concentrations, for example, the second concentration (P ⁺ ) is used here to form the second doped layer 30 in the epitaxial layer 12 through ion implantation, and then vertically The direction of the downward arrow 31 is driven (Drive-In; D/I), so that the second doped layer 30 of P ⁺ is diffused to the left, right, up and down, and the second doped layer 30 of P ⁺ is diffused to the second isolation trench 28. Periphery, such as the bottom and bottom sides.

Next, as shown in FIG. 1G, etch the second doped layer 30 of P ⁺ downwards in the second isolation trench 28, or further etch to the epitaxial layer 12, so as to expand the second isolation trench 28 to the third isolation trench 32, and then perform ion implantation with different doping concentrations, for example, the third doped layer 34 is formed by ion implantation at the third concentration (P ^+' ), wherein the third doped layer 34 can be used for example with the first The second concentration (P ⁺ ) is equal to or greater than the concentration, and then the drive (Drive-In; D/I) method is used in the direction of the vertical downward arrow 31, so that the third doped layer 34 of P ^+' diffuses to the left, right, up and down, And the third doped layer 34 of P ^+′ is located on the periphery of the third isolation trench 32 , such as the bottom and the side of the bottom.

Next, as shown in FIG. 1H, the third doped layer 34 of P ^+' is etched downward in the third isolation trench 32, or further etched to the epitaxial layer 12, so as to expand the third isolation trench 32 to the fourth isolation trench Groove 36, and then carry out the ion implantation process, for example, the fourth doped layer 38 is formed through ion implantation at the fourth concentration (P ⁺⁺ ), wherein the fourth doped layer 38 can use a concentration greater than the third concentration (P ++ ), for example ^+' ) concentration, and then thermally driven (Drive-In; D/I) in the direction of the vertical downward arrow 39, so that the fourth doped layer 38 of P ⁺⁺ diffuses to the left, right, up and down, so that P ⁺⁺ The fourth doped layer 38 is located at the periphery of the fourth isolation trench 36 , such as the bottom and the sides of the bottom.

Next, as shown in FIG. 1I, an isolation structure 40 is formed, located in the fourth isolation trench 36, wherein the isolation structure 40 is made of, for example, an oxide layer (Oxide). Then, as shown in FIG. 1J, N+ source regions 42 are respectively formed on the body In the region 20, the oxide layer 46 is in the N+ source region 42 and the gate structure 18, and the heavily doped layer 48 (for example using P ⁺⁺ ) is in the body and connected to the N+ source region 42 and the isolation structure 40 , has the effect of reducing impedance, and the metal layer 44 is on the isolation structure 40 , the heavily doped layer 48 and the oxide layer 46 . The formation process is as follows: first, etch part of the upper oxide layer 41 in FIG. 1I, and then form an N+ source region 42 in the body region 20 through ion implantation, and then etch both sides, including part of the upper part of the isolation structure 40, part of the N+ The source region 42 and part of the body region 20 are used to form a trench, and then the body region is ion-implanted to form a heavily doped layer 48 , and finally the metal layer 44 is deposited.

In addition, as shown in FIG. 1J , the trench type power metal oxide semiconductor structure is formed, wherein the first doped layer 26, the second doped layer 30, the third doped layer 34 and the fourth doped layer 38 are all connected, of course In terms of design, we can make part of the connection structure according to actual needs, such as controlling at least two doped layers with different doping concentrations to be connected to the interface profile (Junction Profile) obtained at the periphery of the isolation trench, all of which belong to the present invention Examples of possible variations.

In addition, in the embodiment of FIG. 1J , the first doped layer 26 , the second doped layer 30 , the third doped layer 34 and the fourth doped layer 38 are formed from top to bottom in order to change the concentration from light to thick. Trapezoidal interface outline. As shown in FIG. 2, another trench type power metal oxide semiconductor structure of the present invention, wherein multiple doped layers, such as the third doped layer 54 of P ⁺ , the second doped layer 52 of P- ^' , and the second doped layer 52 ^of P- The first doped layer 50 is composed of a plurality of doped layers from top to bottom, and the concentration changes from thick to light to form an inverted trapezoidal interface profile.

In addition, as shown in FIG. 3, another trench type power metal oxide semiconductor structure of the present invention, in which multiple doped layers, such as the third doped layer 60 of P- ^, the second doped layer 62 ^of N- and the P- The composition of the first doped layer 64, that is, different concentrations of different conductivity types (P-type and N-type) can also make the interface profile (Junction Profile), all of which belong to the possible variant embodiments of the present invention.

Next, as shown in FIG. 4 , ion implantation is performed at an oblique angle in the trench power metal oxide semiconductor structure of the present invention. As shown in FIG. 4 , four different steps 210, 220, 230, and 240 are used to perform ion implantation at different oblique angles, and multiple doped layers are formed at different positions of isolation trenches 250, 260, 270, and 280 with different depths. After corresponding to FIG. 1D , you can Skip FIG. 1E and do not need to do vertical downward drive (Drive-In; D/I), go directly to FIG. 1F to perform ion implantation at the first oblique angle (such as step 210) to form the first doped layer 26 ^of P- , and then perform ion implantation at the second oblique angle (such as step 220) in FIG. 1G to form the second doped layer 30 of P ⁺ , and in FIG. The third doped layer 34 of P ^{+ '} and the fourth doped layer 38 of P ++ are formed by performing ion implantation (eg step 240 ).

As shown in FIG. 5, another trench-type power metal-oxide-semiconductor structure of the present invention, wherein a first isolation trench 502, a second isolation trench 504, a third isolation trench 506, and a fourth isolation trench are formed from top to bottom. Groove 508 has different cross-sectional areas (or bottom areas), for example, from top to bottom, the cross-sectional areas become smaller and smaller, and a plurality of doped layers are obtained under different concentration control as a smoother interface profile, wherein the first The inner walls of the first isolation trench 502, the second isolation trench 504, the third isolation trench 506, and the fourth isolation trench 508 can be formed into a spacer (Spacer) 510, wherein any two spacers connected up and down are partially overlapped, Then the isolation trenches 502 , 504 , 506 and 508 are filled with oxide or polysilicon.

As shown in FIG. 6, another trench power metal oxide semiconductor structure of the present invention has the same first isolation trench 602, second isolation trench 604, third isolation trench 606 and fourth isolation trench with different cross-sectional areas as in FIG. The isolation trench 608, the first doped layer 616, the second doped layer 614, the third doped layer 612 and the fourth doped layer 610 formed under different concentration control form an inverted trapezoid with a concentration changing from thick to light interface outline.

The trench-type power metal oxide semiconductor structure and its formation method of the present invention are not limited to the device area or the terminal area, as long as the trench can pass through the control of implanted ion concentration, at least two connection doped layers can be formed to form repeatedly. The interface profile outside the side wall of the trench is used to achieve the design change of the width and shape, so it can form a charge balance (ChargeBalance) and reduce the surface electric field effect (RESURF), and form a relatively gentle electric field distribution between the trench and the side wall electric field, thus improving the endurance. Voltage level and reduce component conduction loss.

As mentioned above, the present invention fully complies with the three requirements of a patent: novelty, creativity and industrial applicability. The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that the embodiments are only for describing the present invention, and should not be construed as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to this embodiment should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope defined by the appended claims.

Claims (10)

1. a kind of forming method of aqueduct type power metal-oxide-semiconductor structure, it is characterised in that include：

Form an isolated groove；

Two doped layers with different levels of doping are formed, and two doped layers are connected positioned at isolated groove periphery, its It is middle to form the isolated groove and form two doped layers with different levels of doping, it is to include：

Form one first isolated groove；

One first doped layer is formed, positioned at the first isolated groove periphery；

First doped layer below first isolated groove is etched, to form one second isolated groove；And

One second doped layer is formed, positioned at the second isolated groove periphery；And

An isolation structure is formed, in the isolated groove.

2. the forming method of aqueduct type power metal-oxide-semiconductor structure according to claim 1, it is characterised in that Formed also includes before the isolated groove step：

Form an epitaxial layer；

A gate trench is formed in the epitaxial layer；

A grid structure is formed in the gate trench；And

A body zone is formed, around the grid structure periphery, and the isolated groove is located at the body zone outside.

3. the forming method of aqueduct type power metal-oxide-semiconductor structure according to claim 1, it is characterised in that Sectional area of the sectional area of first isolated groove more than second isolated groove.

4. the forming method of aqueduct type power metal-oxide-semiconductor structure according to claim 1, it is characterised in that It is to flow into formed on diverse location using different angled ions to form two doped layers.

5. the forming method of aqueduct type power metal-oxide-semiconductor structure according to claim 1, it is characterised in that Two doped layers are from top to bottom to be formed and concentration is to dense by light.

6. a kind of aqueduct type power metal-oxide-semiconductor structure, it is characterised in that include：

One isolated groove；

One isolation structure, in the isolated groove；And

Multiple doped layers with different levels of doping, and the plurality of doped layer is connected peripheral positioned at the isolated groove, wherein The doping content of the plurality of doped layer is from top to bottom incremental.

7. aqueduct type power metal-oxide-semiconductor structure according to claim 6, it is characterised in that also include：

One epitaxial layer；

One gate trench, in the epitaxial layer；

One grid structure, in the gate trench；And

One body zone, around the grid structure periphery, the wherein isolated groove, positioned at the body zone outside, the isolated groove Depth of the depth higher than grid structure.

8. aqueduct type power metal-oxide-semiconductor structure according to claim 6, it is characterised in that the isolated groove Including connected one first isolated groove and one second isolated groove, the plurality of doped layer is correspondingly formed in first isolating trenches Groove and the second isolated groove periphery.

9. aqueduct type power metal-oxide-semiconductor structure according to claim 8, it is characterised in that first isolation Sectional area of the sectional area of groove more than second isolated groove.

10. aqueduct type power metal-oxide-semiconductor structure according to claim 6, it is characterised in that the plurality of It is to flow into formed on diverse location using different angled ions that doped layer is formed.