CN111200007A

CN111200007A - Super junction device and manufacturing method thereof

Info

Publication number: CN111200007A
Application number: CN201811381169.0A
Authority: CN
Inventors: 姜峰; 肖胜安
Original assignee: Shenzhen Sanrise Tech Co ltd
Current assignee: Shenzhen Shangyangtong Technology Co ltd
Priority date: 2018-11-20
Filing date: 2018-11-20
Publication date: 2020-05-26
Anticipated expiration: 2038-11-20
Also published as: CN111200007B

Abstract

The invention discloses a super junction device, wherein a super junction structure is formed by adopting a multiple-time groove etching and filling process, the corresponding groove is divided into more than two sub-grooves in the longitudinal direction, and a second conductive type sub-column is filled in each sub-groove and overlapped to form a second conductive type column. And the first pinch-off voltage at the superposition position of each sub-groove is reduced, and the second pinch-off voltage corresponding to each longitudinal position of the second conductive type sub-column corresponding to the bottom of the superposition position is adjusted to be smaller than the first pinch-off voltage, so that the second conductive type sub-column at the bottom of each superposition position is guaranteed to be pinched off before the superposition position in reverse bias. The invention also provides a manufacturing method of the super junction device. According to the super-junction device and the manufacturing method thereof, the super-junction structure formed by etching and filling the grooves for multiple times can be adopted, so that the process difficulty is reduced, the second conductive type column at the bottom of the superposition position of the sub-grooves can be ensured to be clamped off first, and the breakdown voltage of the super-junction device can be improved.

Description

Super junction device and manufacturing method thereof

Technical Field

The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a super junction (junction) device; the invention also relates to a manufacturing method of the super junction device.

Background

A super-junction structure is adopted in a super-junction device such as a super-junction MOSFET, and the super-junction structure is formed by alternately arranging N-type columns and P-type columns. If a super junction structure is used for replacing an N-type drift region in a Vertical Double-diffused metal-Oxide-Semiconductor (VDMOS) device, a conduction path is provided through an N-type column in a conduction state, and the P-type column does not provide the conduction path when the conduction state is conducted; and under the cut-off state, the PN columns bear reverse bias voltage together, so that the super-junction MOSFET is formed. Therefore, the super junction MOSFET is based on a VDMOS, and a P-type column with a longitudinal structure is added in the transverse direction. Under the condition of very low breakdown voltage, the P-type column is transversely depleted with the N-type column formed by the N-type drift region, so that the on-resistance of the drift region can be greatly reduced under the condition of not reducing the breakdown voltage, and the smaller chip area and the faster switching speed can be realized.

The super junction structure of the super junction MOSFET is usually realized by forming a P-type column in an N-type epitaxial layer, and the P-type column is formed by two realization modes, namely a process based on multi-time epitaxy, and a process based on etching of a deep groove, namely a groove corresponding to the super junction structure. The multi-time epitaxial process has the advantages of simple implementation mode, multiple process steps and long flow. For the current 600V super junction MOSFET device, a multi-time epitaxy technology is adopted, and the number of layers needing epitaxy is usually more than 7 times, even up to 13 times. And the P-type column is formed based on the deep groove etching and P-type silicon filling process, the P-type column is formed only by one-time deep groove etching, and the process steps are few. However, in order to ensure that the P-type silicon filling is defect-free, the deep trench etching angle is not vertical, but inclined, and the angle is 88-89 degrees.

As shown in fig. 1A to 1B, there is a device structure diagram in each step of forming a super junction structure by the manufacturing method of the conventional first super junction device; in a method for manufacturing a superjunction device according to a first related art, a step of forming a superjunction structure includes:

as shown in fig. 1A, a semiconductor substrate, such As a silicon substrate, is raised, typically N + doped, and the dopant impurity is typically As, which has a slower diffusion rate. The resistivity of the semiconductor substrate is typically between 1 and 2m Ω cm. An N-type epitaxial layer such as an N-type silicon epitaxial layer 101 is formed on the surface of the semiconductor substrate, and the higher the breakdown voltage is, the thicker the required thickness of the N-type epitaxial layer 101 is. For the 600V super junction MOSFET commonly used at present, the thickness of the N-type epitaxial layer 101 is typically 50 μm.

Then, a trench 102 is formed in the N-type epitaxial layer 101 by using a photolithography and etching process. Typically, a Hard Mask layer (Hard Mask)104 is used in the process of forming the trench 102. Usually, the Hard Mask is composed of an Oxide layer (Oxide), or may be an Oxide + Nitride + Oxide (ONO) structure of an Oxide layer plus a Nitride layer plus an Oxide layer.

The method specifically comprises the following steps: forming the hard mask layer 104 on the surface of the N-type epitaxial layer 101, and defining a formation region of the trench 102 by lithography; and then, sequentially etching the hard mask layer 104 and the N-type epitaxial layer 101 to form the trench 102. The angle of etching the trench 102 is typically inclined to be between 88 degrees and 89 degrees. This results in a large opening above the trench 102 and a small opening below. Taking a 600V super junction device as an example, the opening of the trench 102 is 4 μm, the depth of the trench 102 etching is 40 μm, the inclination angle of the trench 102 etching is typically 88.5 degrees, and the opening at the bottom of the trench 102 is only 1.9 μm and is less than 50% of the opening at the top.

Thereafter, as shown in fig. 1B, the trench 102 is filled with a P-type epitaxial layer such as a P-type silicon epitaxial layer 103. After the P-type epitaxial layer 103 is filled, a Chemical Mechanical Polishing (CMP) process is usually used to perform planarization, the CMP process uses the remaining film layer of the hard mask layer 104 as a stop layer, and the CMP process removes the remaining hard mask layer 104 after planarization. And then, P-type columns 103 composed of P-type epitaxial layers 103 filled in the trenches 102 are formed, N-type columns 101 composed of N-type epitaxial layers 101 between the P-type columns 103, and the P-type columns 103 and the N-type columns 101 are alternately arranged to form a super junction structure. As shown in fig. 1B, the total amount of P-type impurities is large and the total amount of N-type impurities is small in the top region of the super junction structure; the total amount of P-type impurities and the total amount of N-type impurities in the bottom area of the super junction structure are small, so that PN balance, namely impurity balance matching of a P-type column and an N-type column, deviates from an ideal state, and the PN balance is damaged. This forms a peak of the electric field intensity in the longitudinal direction in the body of the super junction structure such as a P-type column, and ideally the distribution of the electric field intensity in the longitudinal direction in the body of the super junction structure such as a P-type column is approximately flat. Curve 401 in fig. 4 corresponds to the vertical distribution curve of the electric field strength of the P-type column of the superjunction device formed by the prior art first method, and it can be seen that there is only one peak of the electric field strength.

In order to reduce the phenomenon that PN balance is damaged and the electric field intensity distribution generates a peak value corresponding effect, a process method for forming a super junction structure by adopting two grooves is provided. As shown in fig. 2, it is a structural diagram of a superjunction structure formed by the second existing superjunction device manufacturing method; the second conventional method is mainly to divide the trench of the first conventional method into two sub-trenches in the longitudinal direction, such as dividing the trench 202 into

sub-trenches

202a and 202b in the longitudinal direction. The method of forming the

sub-trenches

202a and 202b is the same as the method of forming the trenches in the first method, and is also formed by using the photolithography and etching processes; the N-type epitaxial layer 201 is formed by stacking N-

type sub-epitaxial layers

201a and 201 b. The specific process sequence is as follows: firstly, providing a bottom N-type sub-epitaxial layer 201a in the N-type epitaxial layer 201; then, forming a sub-groove 202a in the N-type sub-epitaxial layer 201a by adopting the same process as the process for forming the groove by the existing first method, namely, by adopting the photoetching and etching process; then, the same process of filling the trenches in the first method is used to fill the P-type sub-epitaxial layer in the sub-trenches 202a and form P-type sub-pillars 203a, and the N-type sub-pillars 201a are formed by the N-type sub-epitaxial layer 201a between the P-type sub-pillars 203 a.

Then, an N-type sub-epitaxial layer 201b is formed, sub-trenches 202b are formed in the N-type sub-epitaxial layer 201b, the sub-trenches 202b are filled and P-type sub-pillars 203b are formed, and the N-type sub-pillars 201b are formed by the N-type sub-epitaxial layer 201b between the P-type sub-pillars 203 b.

Finally, a trench 202 formed by overlapping the

sub-trenches

202a and 202b, a P-type column 203 formed by overlapping the P-

type sub-columns

203a and 203b, and an N-type column 201 formed by overlapping the N-

type sub-columns

201a and 201b are formed, and the entire overlapped N-type epitaxial layer is also denoted by reference numeral 201. The super junction structure is formed by alternating arrangement of N-type columns 201 and P-type columns 203.

The front side structure and the back side structure of the device are formed at the super junction structure to form the corresponding super junction device. Taking a 600V super junction MOSFET as an example, the structure formed by the second method has the following characteristics:

the width of the top opening of the first time of trench etching, namely the etching corresponding to the sub-trench 202a, namely w201a, is also 4 μm, and the top opening is directly defined by a photoetching process; however, the depth of the first groove etching is only 20 μm, so that the difficulty of the first groove etching is reduced, and the difficulty of the subsequent groove filling process is also reduced; and the opening width at the bottom of the sub-trench 202a becomes 2.95 μm, which is increased with respect to 1.9 μm of the first method; the comparison of the widths above assumes that the tilt angle of the first trench etch is the same as the trench etch of the prior first method. In fact, the shallower the depth of the trench etching, the easier the process of P-type silicon filling is realized, and the inclination angle of the trench etching can be closer to the vertical. Because the opening at the bottom of the sub-trench 202a is widened, the P N balance will be closer to ideal. The second trench etch, which is the same as the first trench etch, also provides sub-trenches 202b with similar advantages as sub-trenches 202a and finally improves the PN balance characteristics between the top P-type sub-pillars 203b and N-type sub-pillars 201 b. For the case that the depth of the trench 202 is 20 microns, the thickness of the N-type sub-epitaxial layer 201b is 20 microns, and the depth of the second trench etching is generally greater than the thickness of the N-type sub-epitaxial layer 201b, so that the

sub-trenches

202b and 202a can be connected. In consideration of process fluctuation (Variation), in practical cases, the depth of etching of the sub-trenches 202b is usually taken to be 1.1 times the thickness of the N-type sub-epitaxial layer 201b, for example, 22 μm. The depths of the

sub-trenches

202b and 202a are shown to be the same in fig. 2, and may be chosen to be different in practical processes.

Although the process steps of the second method are increased relative to the first method, the complexity of each process step is reduced. For example, the depth of each groove etching is only half of the original depth, and the depth-to-width ratio of the groove etching is reduced to half of the original depth-to-width ratio. The difficulty of the P-type silicon filling process is reduced due to the reduced depth of the groove etching. More importantly, in the first conventional method, if the step (Pitch) of the superjunction device, i.e., the width of the superjunction cell, is continuously reduced, including the width of the P-type pillars 103 and the Pitch of the P-type pillars 103, i.e., the width of the N-type pillars 101, the width of the P-type pillars 103 needs to be reduced. Reducing the width of the P-type pillar 103 further increases the aspect ratio of the trench etch, which makes the process very difficult. With the second method, the width of the P-type pillar 203 can be reduced to half of the original width if the aspect ratio is not changed. Therefore, the stepping method of the super junction device can be reduced under the condition of not increasing the process complexity.

With the second method, the distribution of the electric field strength in the body becomes more uniform because PN balance is better. Curve 402 in fig. 4 corresponds to the longitudinal distribution curve of the electric field strength of the P-type column of the superjunction device formed by the second conventional method, and it can be seen that the electric field strength in the P-type column has two peaks; comparing

curves

401 and 402, it can be seen that the in-vivo distribution of the electric field strength of curve 402 is more uniform, the covered area is larger, and the breakdown voltage of the device is higher. Through tape flow verification, the breakdown voltage of the super-junction MOSFET formed by the second conventional method of twice trench etching can be improved by more than 150V compared with the first conventional method of once trench etching under the condition that the doping concentrations of the epitaxial layers, namely the N-type epitaxial layer and the P-type epitaxial layer, are not changed. As shown in fig. 5, which is a breakdown voltage curve of the superjunction device formed by the second existing method and the first existing method, the curve corresponds to a curve of the drain current and the drain voltage, the drain voltage at which the drain current suddenly becomes larger corresponds to the breakdown voltage, a curve 403 corresponds to a breakdown voltage curve of the superjunction device formed by the first existing method, and a curve 404 corresponds to a breakdown voltage curve of the superjunction device formed by the second existing method, it can be seen that the breakdown voltage of the second existing method is improved and can be improved by more than 150V. And if the breakdown voltage of the device is ensured to be unchanged, the epitaxial layer with lower resistivity can be adopted in the two-time groove process, so that lower specific on-resistance is obtained. Theoretical calculation shows that if the groove etching is carried out twice under the condition that the breakdown voltage is kept unchanged, the specific on-resistance which can be realized by the groove etching method is only half of that of the deep groove etching once.

Disclosure of Invention

The invention aims to solve the technical problem of providing a super junction device, which can adopt a super junction structure formed by multiple times of groove etching and filling, and can ensure that the pinch-off voltage (ping off) at the superposition position of each sub-groove is greater than the pinch-off voltage at each position of the bottom corresponding to the superposition position, thereby ensuring the voltage-resisting capability of the super junction structure and improving the breakdown voltage of the super junction device. Therefore, the invention also provides a manufacturing method of the super junction device.

In order to solve the above technical problem, the super junction device provided by the present invention includes a super junction structure formed by alternately arranging first conductivity type pillars and second conductivity type pillars.

The second conductive type column is composed of a second conductive type epitaxial layer filled in a groove, the groove is formed in a first conductive type epitaxial layer, and the first conductive type column is composed of a first conductive type epitaxial layer between the grooves.

A drift region of the super junction device has a first conductivity type and includes the first conductivity type column and the first conductivity type epitaxial layer at the bottom of the super junction structure.

The groove is formed by overlapping more than two sub-grooves in the longitudinal direction, each sub-groove is formed in the corresponding first conduction type sub-epitaxial layer, each sub-groove is filled with a second conduction type sub-epitaxial layer formed by single epitaxy, a second conduction type sub-column is formed by the second conduction type sub-epitaxial layers filled in the corresponding sub-grooves, and the second conduction type sub-columns are overlapped to form a second conduction type column; the first conductive type sub-epitaxial layers between the sub-grooves form first conductive type sub-columns, and the first conductive type columns are formed by overlapping the first conductive type sub-columns; and each first conduction type sub-column and the corresponding second conduction type sub-column in the same layer are alternately arranged to form a super junction sub-structure in the corresponding layer, and the super junction sub-structures in all layers are superposed to form the super junction structure.

The process difficulty of groove etching and epitaxial filling is reduced by utilizing the characteristic that the depth-to-width ratio of the sub-groove is smaller than that of the groove; each sub-groove is provided with an inclined side face, and the process difficulty of groove etching and epitaxial filling is reduced through the inclined side faces.

At the superposition position of each sub-trench, the superposition position corresponds to the bottom of the second conductive type sub-column at the top of the superposition position and the top of the second conductive type sub-column corresponding to the lower part of the superposition position, the second conductive type sub-column at the superposition position has a first pinch-off voltage corresponding to the complete transverse depletion, the first pinch-off voltage can be reduced along with the reduction of the width of the bottom of the sub-trench corresponding to the top of the superposition position, and the second pinch-off voltage at each longitudinal position of the second conductive type sub-column corresponding to the bottom of the superposition position is adjusted and is smaller than the first pinch-off voltage, so as to ensure that the second conductive type sub-column at the bottom of the superposition position is pinched off before the superposition position when the super-junction structure is reversely biased and further ensure that the second conductive type sub-column can be completely pinched off in the longitudinal direction Is laterally depleted, thereby improving the withstand voltage of the super junction structure.

In a further improvement, the doping concentration of the second conductivity type sub-column corresponding to the bottom of the stacking position is lower than the doping concentration of the second conductivity type sub-column corresponding to the top of the stacking position; and reducing the second pinch-off voltage by reducing the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position.

In a further improvement, the doping concentration of the first conductivity-type sub-column corresponding to the bottom of the stacking position is also reduced, and the doping concentration of the first conductivity-type sub-column corresponding to the bottom of the stacking position is lower than the doping concentration of the first conductivity-type sub-column corresponding to the top of the stacking position.

In a further improvement, before the epitaxial filling of the second-conductivity-type sub-pillars corresponding to the bottoms of the stacking positions, first-conductivity-type implantation impurities formed by ion implantation are formed on the bottom surfaces and the side surfaces of the corresponding sub-trenches, and the first-conductivity-type implantation impurities are stacked into the corresponding first-conductivity-type sub-pillars, so that the lateral depletion of the second-conductivity-type sub-pillars is increased, and the second pinch-off voltage is reduced.

The further improvement is that the implantation energy of the ion implantation of the first conductive type implantation impurity is 50kev to 200kev, and the implantation dosage is 3e11cm^-2～2e12cm^-2The implantation angle is 0 degree or angled implantation is used.

In a further improvement, the super junction device is a super junction MOSFET.

The gate structure of the super junction MOSFET is a planar gate structure or a trench gate structure.

The further improvement is that the first conductive type is N type, and the second conductive type is P type; or the first conduction type is P type, and the second conduction type is N type.

In order to solve the technical problem, the super junction device in the manufacturing method of the super junction device provided by the invention comprises a super junction structure formed by alternately arranging a first conductive type column and a second conductive type column; the super junction structure forming step comprises the following steps:

providing a first conduction type sub-epitaxial layer at the bottommost part, and forming a sub-groove at the bottommost part in the first conduction type sub-epitaxial layer at the bottommost part by adopting a photoetching and etching process.

And step two, filling a second conduction type sub-epitaxial layer in the bottommost sub-groove to form a bottommost second conduction type sub-column, forming a bottommost first conduction type sub-column by the second conduction type sub-epitaxial layer between the bottommost second conduction type sub-columns, and forming a bottommost super junction sub-structure by alternately arranging the bottommost first conduction type sub-columns and the second conduction type sub-columns.

And thirdly, forming a next layer of corresponding first conduction type epitaxial sub-layer on the surface of the formed topmost super junction sub-structure, and forming a next layer of corresponding sub-groove in the next layer of corresponding first conduction type sub-epitaxial layer by adopting a photoetching and etching process.

And fourthly, filling a second conductive type sub-epitaxial layer in the next corresponding sub-groove to form a next corresponding second conductive type sub-column, forming a next corresponding first conductive type sub-column by the second conductive type sub-epitaxial layer between the next corresponding second conductive type sub-columns, and forming a next corresponding super-junction sub-structure by the next corresponding first conductive type sub-column and the next corresponding second conductive type sub-column in an alternating arrangement mode.

And fifthly, repeating the third step and the fourth step to obtain the super junction structure with the required thickness, wherein the super junction structure is formed by overlapping all the super junction sub-structures, all the first conduction type sub-epitaxial layers are overlapped to form a first conduction type epitaxial layer, all the sub-grooves are overlapped to form grooves, all the second conduction type sub-columns are overlapped to form second conduction type columns, all the first conduction type sub-columns are overlapped to form first conduction type columns, and all the first conduction type columns and the second conduction type columns are alternately arranged to form the super junction structure.

A further improvement is that the doping concentration of the second conductivity type sub-column corresponding to the bottom of the stacking position is lower than the doping concentration of the second conductivity type sub-column corresponding to the top of the stacking position, the doping concentration of the corresponding second conductivity type sub-column is adjusted when the sub-trench is filled with the second conductivity type sub-epitaxial layer, and the second pinch-off voltage is reduced by reducing the doping concentration of the second conductivity type sub-column corresponding to the bottom of the stacking position.

In a further improvement, the super junction device is a super junction MOSFET.

The second conductive type column of the super junction structure is composed of the second conductive type epitaxial layer filled in the groove, the groove is divided into a plurality of sub grooves which are longitudinally overlapped, and the sub grooves are respectively formed through corresponding groove etching processes, so that the depth of each sub groove can be reduced, and the difficulty of the groove etching and epitaxial filling processes of each sub groove is reduced.

Meanwhile, aiming at the technical problems provided by the invention, according to the situation that the width of each sub-trench is suddenly reduced at the superposition position of each sub-trench to reduce the corresponding pinch-off voltage, namely the first pinch-off voltage, the invention adjusts the second pinch-off voltage corresponding to each longitudinal position of the corresponding second conductive type sub-column at the bottom of the superposition position and reduces the second pinch-off voltage at each longitudinal position to be less than the first pinch-off voltage, so that the second conductive type sub-column at the bottom of each superposition position is guaranteed to be pinched off before the superposition position when the super-junction structure is reversely biased, and the second conductive type column is guaranteed to be completely and transversely exhausted in the longitudinal direction, thereby improving the withstand voltage of the super-junction structure and improving the breakdown voltage of the super-junction device.

Drawings

The invention is described in further detail below with reference to the following figures and detailed description:

fig. 1A to 1B are device structure diagrams in steps of forming a super junction structure by a manufacturing method of a prior art first super junction device;

fig. 2 is a structural diagram of a superjunction structure formed by a second conventional superjunction device manufacturing method;

fig. 3 is a simulation diagram of a superjunction device formed by a second prior art method;

fig. 4 is a graph obtained by simulating the electric field strength of the P-type column of the superjunction device formed by the second conventional method and the first conventional method along the AA line in fig. 3;

fig. 5 is a breakdown voltage curve of a superjunction device formed by the second prior art method and the first prior art method;

fig. 6 is a simulation diagram of defects of a superjunction device formed by a second prior art method;

FIG. 7 is a simulation graph of electric field intensity distribution of the P-type columns along the AA line in FIG. 3 for the simulation device of FIG. 3 and the simulation device of FIG. 6;

fig. 8 is a schematic diagram of a super junction structure of the super junction device of the first embodiment of the present invention.

Detailed Description

The defect analysis of the existing second method comprises the following steps:

the structure of the super junction device and the corresponding manufacturing method of the super junction device in each embodiment of the invention are obtained on the basis of analyzing the defects of the existing second method, the technical problems which need to be solved and are corresponding to the embodiments of the invention are solved by analyzing the defects of the existing second method, and finally the structure of the super junction device and the corresponding manufacturing method of the super junction device in each embodiment of the invention are obtained.

In the super junction structure of the super junction device formed by the second method, because the width of the opening etched by each trench, that is, the width of the top opening of each sub-trench is relatively narrow, the widths of the top openings of the sub-trenches 202a and 202b are both 2 μm, the depth of the first-stage trench, that is, the sub-trench 202a, is 20 μm, and the depth of the second-stage trench, that is, the sub-trench 202b, is 22 μm. As shown in the area 405 corresponding to the oval circle of fig. 6, the area 405 is the overlapping position of the P-

type sub-pillars

203a and 203b, because the top opening of the sub-trench 202b is narrower, and because the side surface of the sub-trench 202b is inclined, the width of the bottom opening of the sub-trench 202b, that is, the opening at the area 405, becomes narrower. Since the bottom opening of the sub-trench 202b is narrow, the P-type impurity at this location, i.e., the region 405, is easily completely depleted at a low voltage. If the P-type impurity at region 405 is completely depleted, the potential of P-type column 203 in the trench at the bottom of region 405 is not connected to the source, i.e., 0 potential, but to the drain high potential. Thus, depletion between the P-type sub-column 203a and the corresponding lateral N-type sub-column 201a in the trench 202a at the bottom of the first segment at the bottom of the region 405 no longer occurs because the potentials of the two are connected to the drain and equal, and there is no lateral potential difference for depletion, which results in that the depth of the effective P-type column 203 of the super junction device is only the depth of the P-type sub-column 203b, and the breakdown voltage of the device is reduced by half. This situation where the bottom P-type sub-column 203a is not depleted is more likely to occur where the P-type impurity is filled at a lower concentration, in which case the P-type impurity at the region 405 is more likely to be completely depleted, thereby preventing the bottom P-type sub-column 203a from being depleted.

Fig. 7 is a simulation curve of the electric field intensity distribution of the P-type column at the position corresponding to the AA line in fig. 3 for the simulation device in fig. 3 and the simulation device in fig. 6, where the corresponding simulation is TCAD simulation, and a curve 402 in fig. 7 is the same as a curve 402 in fig. 4, and both the P-

type columns

203a and 203b are completely depleted under reverse bias in a case where the filling of the P-type column 203 is ideal. When the concentration of the P-type column 203 is weak, which is 10% weak in the simulation corresponding to fig. 7, the impurity of the P-type column portion at the position of the region 405 is depleted in advance, that is, the P-type impurity at the position of the region 405 is completely depleted under the condition that the P-type sub-column 203a at the bottom is not depleted, and the simulation curve of the electric field intensity distribution of the corresponding P-type column is the curve 406, it can be seen that, below the region 405, the P-type sub-column 203a is directly connected to the drain, so that the internal electric field of the P-type sub-column 203a is reduced to 0, and depletion cannot be achieved. The depth of the P-type column 203 is only equivalent to the depth of the second segment, i.e., the P-type sub-column 203b, and the breakdown voltage of the device is sharply reduced at this time, which is only 46% of the breakdown voltage under normal conditions.

The first embodiment of the invention is a super junction device:

as shown in fig. 8, is a schematic diagram of a super junction structure of a super junction device of the first embodiment of the present invention; the super junction device of the first embodiment of the present invention includes a super junction structure formed by alternating arrangement of first conductive type pillars 301 and second conductive type pillars 303.

The second conductive type column 303 is composed of a second conductive type epitaxial layer 303 filled in a trench 302, the trench 302 is formed in a first conductive type epitaxial layer 301, and the first conductive type column 301 is composed of the first conductive type epitaxial layer 301 between the trenches 302. Here, the second conductive type pillars and the second conductive type epitaxial layer are both denoted by reference numeral 303, and the first conductive type pillars and the first conductive type epitaxial layer are both denoted by reference numeral 301.

The drift region of the superjunction device has a first conductivity type and includes the first conductivity type column 301 and the first conductivity type epitaxial layer 301 at the bottom of the superjunction structure.

The groove 302 is divided into two or more sub-grooves superimposed in the longitudinal direction, two of which are shown in fig. 8 and indicated by

reference numerals

302a and 302b, respectively. Each sub-trench is formed in the corresponding sub-epitaxial layer of the first conductivity type, each sub-trench is filled with a sub-epitaxial layer of the second conductivity type formed by single epitaxy, a sub-column of the second conductivity type is formed by the sub-epitaxial layer of the second conductivity type filled in the corresponding sub-trench, in fig. 8, the sub-column of the second conductivity type in the sub-trench 302a is denoted by a mark 303a, the sub-column of the second conductivity type in the sub-trench 302b is denoted by a mark 303b, and the sub-columns of the second conductivity type are overlapped to form a column 303 of the second conductivity type; the first-conductivity-type sub-epitaxial layer between the sub-trenches forms first-conductivity-type sub-pillars, the first-conductivity-type sub-pillars between the sub-trenches 302a are denoted by reference numeral 301a, the first-conductivity-type sub-pillars between the sub-trenches 302b are denoted by reference numeral 301b, and the first-conductivity-type pillars 301 are formed by overlapping the first-conductivity-type sub-pillars; and each first conduction type sub-column and the corresponding second conduction type sub-column in the same layer are alternately arranged to form a super junction sub-structure in the corresponding layer, and the super junction sub-structures in all layers are superposed to form the super junction structure.

The process difficulty of etching and epitaxial filling of the trench 302 is reduced by using the feature that the aspect ratio of the sub-trench is smaller than that of the trench 302; each sub-trench has inclined side faces, and the inclined side faces reduce the difficulty of the process of etching and epitaxial filling the trench 302.

At the superimposed position of each sub-trench 302, the superimposed position corresponds to the bottom of the second-conductivity-type sub-column at the top of the superimposed position and the top of the second-conductivity-type sub-column at the lower part of the superimposed position, the second-conductivity-type sub-column at the superimposed position has a first pinch-off voltage corresponding to the complete lateral depletion, the first pinch-off voltage decreases with the decrease of the width of the bottom of the sub-trench corresponding to the top of the superimposed position, and by adjusting the second pinch-off voltage corresponding to each longitudinal position of the second-conductivity-type sub-column at the bottom of the superimposed position and making the second pinch-off voltage at each longitudinal position smaller than the first pinch-off voltage, the second-conductivity-type sub-column at the bottom of the superimposed position is ensured to pinch off before the superimposed position when the super junction structure is reversely biased, thereby ensuring that the second-conductivity-type column 303 is longitudinally capable of being pinched off at the superimposed position Is completely laterally depleted, thereby improving the withstand voltage of the super junction structure.

In the first embodiment of the present invention, the doping concentration of the second conductive-type sub-column corresponding to the bottom of the stacking position is lower than the doping concentration of the second conductive-type sub-column corresponding to the top of the stacking position; and reducing the second pinch-off voltage by reducing the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position. In the first embodiment of the present invention, the trench 302 is formed by overlapping two sub-trenches in the longitudinal direction, and the distribution of the two sub-trenches is indicated by the

marks

302a and 302 b. In fig. 8, the doping concentration of the second-conductivity-type sub-column 303a is lower than that of the second-conductivity-type sub-column 303b, so that the second pinch-off voltage corresponding to the second-conductivity-type sub-column 303a at the bottom layer can be reduced, and the bottom of the second-conductivity-type sub-column 303b, i.e., the overlapping position, is prevented from being depleted before the second-conductivity-type sub-column 303a is completely depleted.

The doping concentration of the first conductive-type sub-column 301a corresponding to the bottom of the stacking position is also reduced, and the doping concentration of the first conductive-type sub-column 301a corresponding to the bottom of the stacking position is lower than the doping concentration of the first conductive-type sub-column 301b corresponding to the top of the stacking position. This can be achieved by reducing the doping concentration of the first-conductivity-type sub-epitaxial layer corresponding to the first-conductivity-type sub-column 301 a. In this way, the doping concentration of the super junction substructure at the bottom layer is reduced as a whole and good PN balance is maintained, and since the doping concentrations of the P-type column and the N-type column of the super junction substructure are reduced, the pinch-off voltage of the P-type column and the N-type column can be reduced, thereby realizing the adjustment of the second pinch-off voltage of the first embodiment of the present invention.

in the first embodiment of the present invention, the super-junction device is a super-junction MOSFET, the gate structure of the super-junction MOSFET is a planar gate structure or a trench 302 gate structure, the first conductivity type is N-type, the second conductivity type is P-type, in other embodiments, the first conductivity type is P-type, and the second conductivity type is N-type, compared to the conventional structure shown in fig. 2, the process structures of the sub-trenches 302a and 302b of the first embodiment of the present invention, such as depth, opening width, and side tilt angle, can be the same as the conventional structure shown in fig. 2, in fig. 8, the top opening width w301a of the sub-trench 302a and the top opening width w301b of the sub-trench 302b are both defined by photolithography, and the top opening widths w301a and w301b can both be 4 μm, and the side tilt angles α 301a and α 301b of the sub-trench 302a and 302b are both 88 to 89 degrees.

The second conductive type column 303 of the super junction structure according to the first embodiment of the present invention is formed by the second conductive type epitaxial layer 303 filled in the trench 302, and the trench 302 is divided into a plurality of longitudinally stacked sub-trenches 302 according to the first embodiment of the present invention, and the sub-trenches 302 are respectively formed by the corresponding trench 302 etching process, so that the depth of each sub-trench 302 can be reduced, thereby reducing the difficulty of the trench 302 etching and epitaxial filling process of each sub-trench 302.

Meanwhile, in view of the technical problem proposed by the present invention, according to the situation that the width of each sub-trench 302 is suddenly reduced at the overlapping position of each sub-trench 302 to reduce the corresponding pinch-off voltage, that is, the first pinch-off voltage, the first embodiment of the present invention adjusts the second pinch-off voltage corresponding to each longitudinal position of the corresponding second conductive type sub-column at the bottom of the overlapping position and reduces the second pinch-off voltage at each longitudinal position to be smaller than the first pinch-off voltage, so as to ensure that the second conductive type sub-column at the bottom of each overlapping position is pinched off before the overlapping position when the super junction structure is reversely biased, and thus ensure that the second conductive type column 303 is completely laterally depleted in the longitudinal direction, thereby improving the withstand voltage of the super junction structure and improving the breakdown voltage of the super junction device.

The second embodiment of the invention is a super junction device:

the second embodiment superjunction device of the present invention is different from the first embodiment superjunction device of the present invention in that:

in the second embodiment superjunction device of the present invention, before the epitaxial filling of the second conductivity-type sub-column 303a corresponding to the bottom at the superimposed position, first conductivity-type implantation impurities formed by ion implantation are formed on the bottom surface and the side surface of the corresponding sub-trench 302a, and the first conductivity-type implantation impurities are superimposed into the corresponding first conductivity-type sub-column 301a, increasing the lateral depletion of the second conductivity-type sub-column 303a and thereby reducing the second pinch-off voltage. That is, for the superjunction sublayer at the bottom layer, since the first conductivity-type impurities of the first conductivity-type sub-column 301a increase, it is possible to accelerate depletion of the second conductivity-type sub-column 303a and thus to lower the second pinch-off voltage.

The implantation energy of the ion implantation of the first conductive type implantation impurities is 50kev to 200kev, and the implantation dose is 3e11cm^-2～2e12cm^-2The implantation angle is 0 degree or angled implantation is used. Since the first conductive type is N-type and the second conductive type is P-type in the second embodiment of the present invention, the first conductive type implantation impurity is phosphorus or arsenic.

Other embodiments superjunction devices:

in other embodiments of the superjunction device, the second pinch-off voltage can be adjusted together with the adjustment of the doping concentration of the second conductivity-type sub-column of the first embodiment superjunction device of the present invention and the ion implantation in the corresponding sub-trench of the second embodiment superjunction device of the present invention to form the first conductivity-type implanted impurity superimposed into the first conductivity-type sub-column.

The method of the first embodiment of the invention:

the super junction device in the manufacturing method of the super junction device of the first embodiment of the present invention includes a super junction structure formed by alternately arranging first conductive type pillars 301 and second conductive type pillars 303; the super junction structure forming step comprises the following steps:

step one, providing the first conductive type sub-epitaxial layer 301a at the bottommost, and forming a sub-trench 302a at the bottommost in the first conductive type sub-epitaxial layer 301a at the bottommost by adopting a photoetching and etching process.

Step two, filling a second conductivity type sub-epitaxial layer 303a in the bottommost sub-trench 302a to form a bottommost second conductivity type sub-column 303a, forming a bottommost first conductivity type sub-column 301a by the second conductivity type sub-epitaxial layer 301a between the bottommost second conductivity type sub-columns 303a, and forming a bottommost super junction sub-structure by the alternating arrangement of the bottommost first conductivity type sub-columns 301a and the second conductivity type sub-columns 303 a.

And thirdly, forming a next layer of corresponding first conduction type epitaxial sub-layer 301b on the surface of the formed topmost super junction sub-structure, and forming a next layer of corresponding sub-groove 302b in the next layer of corresponding first conduction type sub-epitaxial layer 301b by adopting a photoetching and etching process.

Step four, filling a second conductive type sub-epitaxial layer 303b in the next corresponding sub-trench 302b to form a next corresponding second conductive type sub-column 303b, forming a next corresponding first conductive type sub-column 301b by the second conductive type sub-epitaxial layer 301b between the next corresponding second conductive type sub-columns 303b, and forming a next corresponding super junction sub-structure by alternately arranging the next corresponding first conductive type sub-column 301b and the next corresponding second conductive type sub-column 303 b.

Step five, repeating the step three and the step four to obtain the super junction structure with the required thickness, wherein the super junction structure is formed by overlapping all the super junction sub-structures, a first conduction type epitaxial layer 301 is formed by overlapping all the first conduction type sub-epitaxial layers, a groove 302 is formed by overlapping all the sub-grooves, a second conduction type column 303 is formed by overlapping all the second conduction type sub-columns, a first conduction type column 301 is formed by overlapping all the first conduction type sub-columns, and the super junction structure is formed by alternately arranging all the first conduction type columns 301 and the second conduction type columns 303.

In the method according to the first embodiment of the present invention, the doping concentration of the second conductive-type sub-column corresponding to the bottom of the stacking position is lower than the doping concentration of the second conductive-type sub-column corresponding to the top of the stacking position; and reducing the second pinch-off voltage by reducing the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position. In the method according to the first embodiment of the present invention, the trench 302 is formed by overlapping two sub-trenches in the longitudinal direction, and the distribution of the two sub-trenches is indicated by the

marks

compared with the prior structure shown in FIG. 2, the process structure of the sub-trenches 302a and 302b formed by the method of the first embodiment of the invention, such as depth, opening width and side inclination angle, can be the same as the prior structure shown in FIG. 2. in FIG. 8, the top opening width w301a of the sub-trench 302a and the top opening width w301b of the sub-trench 302b are defined by photolithography, the top opening widths w301a and w301b can be 4 micrometers, and the side inclination angles α 301a and α 301b of the sub-trench 302a and 302b are generally 88-89 degrees.

The method of the second embodiment of the invention:

the manufacturing method of the super junction device of the second embodiment of the present invention is different from the manufacturing method of the super junction device of the first embodiment of the present invention in that:

in the method according to the second embodiment of the present invention, before the epitaxial filling of the second conductive-type sub-column 303a corresponding to the bottom of the overlap position, a first conductive-type implantation impurity formed by ion implantation is formed on the bottom surface and the side surface of the corresponding sub-trench 302a, and the first conductive-type implantation impurity is overlapped into the corresponding first conductive-type sub-column 301a, so as to increase the lateral depletion of the second conductive-type sub-column 303a and thereby reduce the second pinch-off voltage. Since there are only two layers of the super junction sub-structure in the method according to the second embodiment of the present invention, after the sub-trench 302a is formed in the first step, ion implantation is directly performed to form the first conductive type implantation impurities on the side surfaces and the bottom surface of the sub-trench 302 a; and then, performing epitaxial filling in the second step to form the second conductive sub-epitaxial layer 303 a. After the method according to the second embodiment of the present invention is adopted, since the first conductive type impurities of the first conductive type sub-column 301a are increased, the depletion of the second conductive type sub-column 303a can be accelerated and the second pinch-off voltage can be reduced.

Other embodiments a method of manufacturing a superjunction device:

in other embodiments of superjunction devices, the adjustment of the doping concentration of the second-conductivity-type sub-column in combination with the first-embodiment supermethod of the present invention and the ion implantation in the corresponding sub-trench in the second-embodiment method of the present invention form the first-conductivity-type implanted impurity superimposed into the first-conductivity-type sub-column to adjust the second pinch-off voltage together.

The present invention has been described in detail with reference to the specific embodiments, but these should not be construed as limitations of the present invention. Many variations and modifications may be made by one of ordinary skill in the art without departing from the principles of the present invention, which should also be considered as within the scope of the present invention.

Claims

1. A super junction device is characterized by comprising a super junction structure formed by alternately arranging first conductive type columns and second conductive type columns;

the second conductive type column is composed of a second conductive type epitaxial layer filled in a groove, the groove is formed in a first conductive type epitaxial layer, and the first conductive type column is composed of a first conductive type epitaxial layer between the grooves;

a drift region of the super junction device has a first conductivity type and comprises the first conductivity type column and the first conductivity type epitaxial layer at the bottom of the super junction structure;

the groove is formed by overlapping more than two sub-grooves in the longitudinal direction, each sub-groove is formed in the corresponding first conduction type sub-epitaxial layer, each sub-groove is filled with a second conduction type sub-epitaxial layer formed by single epitaxy, a second conduction type sub-column is formed by the second conduction type sub-epitaxial layers filled in the corresponding sub-grooves, and the second conduction type sub-columns are overlapped to form a second conduction type column; the first conductive type sub-epitaxial layers between the sub-grooves form first conductive type sub-columns, and the first conductive type columns are formed by overlapping the first conductive type sub-columns; each first conduction type sub-column and the corresponding second conduction type sub-column in the same layer are alternately arranged to form a super junction sub-structure in the corresponding layer, and the super junction sub-structures in all layers are overlapped to form the super junction structure;

the process difficulty of groove etching and epitaxial filling is reduced by utilizing the characteristic that the depth-to-width ratio of the sub-groove is smaller than that of the groove; each sub-groove is provided with an inclined side face, and the process difficulty of groove etching and epitaxial filling is reduced through the inclined side faces;

2. The superjunction device of claim 1, wherein: the doping concentration of the second conductive type sub-column corresponding to the bottom of the stacking position is lower than that of the second conductive type sub-column corresponding to the top of the stacking position; and reducing the second pinch-off voltage by reducing the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position.

3. The superjunction device of claim 2, wherein: the doping concentration of the first conductive type sub-column corresponding to the bottom of the stacking position is also reduced, and the doping concentration of the first conductive type sub-column corresponding to the bottom of the stacking position is lower than that of the first conductive type sub-column corresponding to the top of the stacking position.

4. The superjunction device of claim 1, wherein: before the epitaxial filling of the second conductive type sub-column corresponding to the bottom of the superposition position, first conductive type injection impurities formed by ion injection are formed on the bottom surface and the side face of the corresponding sub-groove, the first conductive type injection impurities are superposed into the corresponding first conductive type sub-column, the transverse depletion of the second conductive type sub-column is increased, and therefore the second pinch-off voltage is reduced.

5. The superjunction device of claim 4, wherein: the implantation energy of the ion implantation of the first conductive type implantation impurities is 50kev to 200kev, and the implantation dose is 3e11cm^-2～2e12cm^-2The implantation angle is 0 degree or angled implantation is used.

6. The superjunction device of claim 1, wherein: the super junction device is a super junction MOSFET.

7. The superjunction device of claim 6, wherein: the gate structure of the super junction MOSFET is a planar gate structure or a trench gate structure.

8. The superjunction device of claim 1, wherein: the first conductive type is N type, and the second conductive type is P type; or the first conduction type is P type, and the second conduction type is N type.

9. A manufacturing method of a super junction device is characterized in that the super junction device comprises a super junction structure formed by alternately arranging first conductive type columns and second conductive type columns; the super junction structure forming step comprises the following steps:

providing a bottommost first conduction type sub-epitaxial layer, and forming a bottommost sub-groove in the bottommost first conduction type sub-epitaxial layer by adopting a photoetching and etching process;

filling a second conductive type sub-epitaxial layer in the bottommost sub-groove to form a bottommost second conductive type sub-column, forming a bottommost first conductive type sub-column by the second conductive type sub-epitaxial layer between the bottommost second conductive type sub-columns, and forming a bottommost super junction sub-structure by alternately arranging the bottommost first conductive type sub-columns and the second conductive type sub-columns;

thirdly, forming a next layer of corresponding first conduction type epitaxial sub-layer on the surface of the formed topmost super junction sub-structure, and forming a next layer of corresponding sub-groove in the next layer of corresponding first conduction type sub-epitaxial layer by adopting a photoetching and etching process;

filling a second conductive type sub-epitaxial layer in the next corresponding sub-groove to form a next corresponding second conductive type sub-column, forming a next corresponding first conductive type sub-column by the second conductive type sub-epitaxial layer between the next corresponding second conductive type sub-columns, and forming a next corresponding super-junction sub-structure by the next corresponding first conductive type sub-column and the next corresponding second conductive type sub-column in an alternating arrangement manner;

step five, repeating the step three and the step four to obtain the super junction structure with the required thickness, wherein the super junction structure is formed by overlapping all the super junction sub-structures, a first conduction type epitaxial layer is formed by overlapping all the first conduction type sub-epitaxial layers, a groove is formed by overlapping all the sub-grooves, a second conduction type column is formed by overlapping all the second conduction type sub-columns, a first conduction type column is formed by overlapping all the first conduction type sub-columns, and the super junction structure is formed by alternately arranging all the first conduction type columns and the second conduction type columns;

10. The method of manufacturing a superjunction device of claim 9, wherein: the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position is lower than that of the second conductive type sub-column corresponding to the top of the superposition position, the doping concentration of the corresponding second conductive type sub-column is adjusted when the second conductive type sub-epitaxial layer is filled in the sub-groove, and the second pinch-off voltage is reduced by reducing the doping concentration of the second conductive type sub-column corresponding to the bottom of the superposition position.

11. The method of manufacturing a superjunction device of claim 10, wherein: the doping concentration of the first conductive type sub-column corresponding to the bottom of the stacking position is also reduced, and the doping concentration of the first conductive type sub-column corresponding to the bottom of the stacking position is lower than that of the first conductive type sub-column corresponding to the top of the stacking position.

12. The method of manufacturing a superjunction device of claim 9, wherein: before the epitaxial filling of the second conductive type sub-column corresponding to the bottom of the superposition position, first conductive type injection impurities formed by ion injection are formed on the bottom surface and the side face of the corresponding sub-groove, the first conductive type injection impurities are superposed into the corresponding first conductive type sub-column, the transverse depletion of the second conductive type sub-column is increased, and therefore the second pinch-off voltage is reduced.

13. The method of manufacturing a superjunction device of claim 12, wherein: the implantation energy of the ion implantation of the first conductive type implantation impurities is 50kev to 200kev, and the implantation dose is 3e11cm^-2～2e12cm^-2The implantation angle is 0 degree or angled implantation is used.

14. The method of manufacturing a superjunction device of claim 9, wherein: the super junction device is a super junction MOSFET.

15. The method of manufacturing a superjunction device of claim 14, wherein: the gate structure of the super junction MOSFET is a planar gate structure or a trench gate structure.