CN116314246A

CN116314246A - Superjunction device and method of manufacturing the same

Info

Publication number: CN116314246A
Application number: CN202111495126.7A
Authority: CN
Inventors: 肖胜安
Original assignee: Shenzhen Shangyangtong Technology Co ltd
Current assignee: Shenzhen Shangyangtong Technology Co ltd
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2023-06-23

Abstract

The invention discloses a super junction device, the structure of the super junction device in an active region comprises: the planar gate structures are formed at the tops of the first conductive type columns and are of an integral structure; the second well region is formed by annealing an ion implantation region of a second conductivity type taking a planar gate structure as a self-alignment condition; the second well region is laterally diffused to the bottom region of the planar gate structure under the action of annealing treatment; the channel region is comprised of a second well region covered by a planar gate structure, and a self-aligned structure between the second well region and the planar gate structure is used to improve device uniformity. The invention also discloses a manufacturing method of the superjunction device. The invention can improve the consistency of devices.

Description

Superjunction device and method of manufacturing the same

Technical Field

The present invention relates to the field of semiconductor integrated circuit fabrication, and in particular to a super junction device; the invention also relates to a manufacturing method of the superjunction device.

Background

The existing superjunction device comprises a current flow region, namely an active region, a transition region and a terminal region; a superjunction structure is formed in the current flow region, and the superjunction structure is composed of P-type columns and N-type columns which are alternately arranged, namely P-N type columns. Taking the structure of strip-shaped P-N type columns as an example, a planar gate structure is arranged above each N type column, the planar gate structure can partially cover peripheral P type columns or not, a P type well (Pwell) is arranged above each P type column, an N+ source region is arranged in the P type well, a contact hole is formed in the P type well, source metal is connected with the source region through the contact hole, and the contact hole of the source metal is connected with the P region through a P+ contact region with high concentration. In the transition region, there is a P-type ring, which covers 1 to a plurality of P-type pillars, the P-type ring can be completed by the same process as the P-type well, there is a p+ contact region with high concentration in the P-type ring, the p+ contact region in the P-type ring and the p+ contact region in the current flow region are formed in the same process, and the concentration and junction depth are the same.

In the device structure, the width of the P-type well below the planar gate structure is actually the channel length of the device, and the size of the channel length influences the on-resistance and the switching characteristic of the device. In the N-type region between P-type wells at the bottom of the planar gate structure, N-type impurities are typically implanted to reduce on-resistance and form an anti-JFET region whose width directly affects the reverse transfer capacitance (Crss) of the device, which consists of gate-drain capacitance (Cgd), which is also Miller capacitance (Miller).

In the prior art, a general Pwell is formed after or before a P-type column, a P-type ring forming area of a transition region is defined by photoetching, the width of the P-type ring is 1-50 microns, and a P-type well forming area of a current flowing region is defined; then, P-type impurities, such as B, or BF2, are implanted by an ion implantation process, thus forming a P-type well.

Thereafter forming a dielectric guard ring, comprising: and forming a dielectric film of the dielectric protection ring, namely a G-field dielectric film, photoetching and etching the G-field dielectric film to ensure that the G-field dielectric film only covers the surfaces of the transition region and the terminal region, and removing the G-field dielectric film on the surface of the active region completely, thereby forming the dielectric protection ring surrounding the active region.

And forming a planar gate structure, namely forming a gate oxide film and a polysilicon gate, defining a gate region in the active region by gate photoetching and etching, defining a gate longitudinal direction (Bus) on the transition region, and defining a gate region in the terminal region or not in the terminal region.

After the planar gate structure is formed, the region where the P-type well and the planar gate structure overlap in the active region forms a channel region, and the length of the channel region is actually influenced by the size of the P-type region formed by photoetching and etching of the P-type well, and also influenced by the position, namely the photoetching overlay accuracy, and also influenced by the size and the position of the polysilicon gate of the active region formed by photoetching and etching of the polysilicon gate. Therefore, the uniformity of the length of the channel regions formed by the prior method, namely the uniformity of the channel length, is poor, and the uniformity of the width of the anti-JFET regions among the channel regions is poor, so that the uniformity of the on-resistance and the threshold voltage of the device is affected, and the uniformity of the device Cgd and the gate-source capacitance (Cgs) is also affected, wherein the Cgd comprises the capacitance formed by covering the anti-JFET regions among the channel regions by a planar gate structure, and the Cgd comprises the capacitance formed by covering the channel regions by the planar gate structure.

The following description will be made on the existing superjunction device with reference to fig. 1:

FIG. 1 is a schematic diagram of a structure of a conventional superjunction device; in fig. 1, only the cross-sectional structure of the active region is shown, taking an N-type superjunction MOSFET as an example, the conventional superjunction device includes:

a superjunction structure is formed in the semiconductor substrate 101, the superjunction structure is formed by alternately arranging a plurality of N-type columns and P-type columns 103, and a superjunction unit is formed by one of the N-type columns and an adjacent one of the P-type columns 103.

Typically, the semiconductor substrate 101 comprises a silicon substrate. Typically, an N-type epitaxial layer 102 is formed on the surface of the semiconductor substrate 101, and the N-type pillars are composed of the N-type epitaxial layer 102 between the P-type pillars 103.

The structure of the superjunction device in the active region includes:

a P-type well region (PWell) 106 formed on top of the P-type pillar 103, the P-type well region 106 further extending into the N-type pillar on both sides of the P-type pillar 103, the P-type well region 106 being defined by photolithography and formed by ion implantation.

The planar gate structures are formed at the top of each N-type column and are of an integral structure; the planar gate structure is formed by overlapping a gate dielectric layer 104 and a gate conductive material layer 105.

Typically, the gate dielectric layer 104 includes a gate oxide layer. The gate conductive material layer 105 comprises a polysilicon gate.

The planar gate structure also needs to be patterned by adopting a photoetching definition and etching process.

N+ doped source regions 107 are self-aligned to the surfaces of the P-type well regions 106 formed on either side of the planar gate structure.

The P-type well region 106 and the planar gate structure need to overlap and the P-type well region 106 located at the bottom of the planar gate structure forms a channel region, and in fig. 1, the length of the channel region, that is, the channel length, adopts the Lc surface.

The area between the P-well regions 106 at the bottom of the planar gate structure is the area where JFET effect occurs, the width of which is Wj, and N-type ion implantation is typically required to form the JFET resistant region.

The front side structure of the superjunction device further comprises:

an interlayer film 108, a contact hole 109 penetrating the interlayer film 108; a body contact region 110 consisting of a P-type heavily doped region is also formed at the bottom of the contact hole 109 at the top of the source region 108, so that the body region 104 is connected to the contact hole 109 at the top through the body contact region 110 and the source region 108 together.

Source metal and gate metal are patterned from the front side metal layer 111.

The back structure of the superjunction device comprises:

thinning the semiconductor substrate 101, and forming a drain region; the drain region is directly formed by thinning the heavily doped semiconductor substrate 101, or is formed by N-type heavily doped back side ion implantation after thinning the semiconductor substrate 101.

A back metal layer 112 is formed.

FIG. 2 is a flow chart of a method of fabricating a prior art superjunction device for fabricating the prior art superjunction structure shown in FIG. 1; the steps are represented in fig. 2 using a mask level. The manufacturing method of the existing superjunction device comprises the following steps:

proceeding to step S101 to form the Zero Mark (Zero Mark) requires a photolithography (photo) plus etch (etch) process, step S201 is also denoted by Zero photo & etch in fig. 2.

Step S102 is performed to form the anti-JFET region, which needs to be defined by a photolithography process, so in fig. 2, step S101 is denoted by JFET photo & IMP.

Step S103 is performed to form a super junction structure, i.e., to form P-type pillars 103 shown in fig. 1, where the P-type pillars 103 are formed by a trench (trench) etching and filling process, and the N-type epitaxial layer 102 between the P-type pillars 103 constitutes an N-type pillar. The formation of the superjunction structure requires the use of a mask defining trenches, so step S103 in fig. 2 is denoted by Trench photo & etch.

Step S104 is performed to form P-type well region 106. The P-well 106 is first defined by photolithography and then ion implantation, so in fig. 1, step S104 is denoted by Pwell photo & IMP.

Step S105 is performed to form a dielectric guard ring, where growth of a material layer (Gfield) of the dielectric guard ring is required, and then a photolithography and etching process is performed to remove the material layer of the dielectric guard ring in the active region, and the material layer of the dielectric guard ring remaining in the dielectric guard ring is formed into the dielectric guard ring. Therefore, in fig. 2, step S105 is represented by the Gfield photo & tech.

Step S106 is carried out to form a planar gate structure, wherein the planar gate structure is required to be formed into a superposition structure of a gate oxide layer and a polysilicon gate, and then a photoetching and etching process is carried out to pattern the planar gate structure. Therefore, in fig. 2, step S106 is represented by poly photo & tech.

Step S107 is performed to form a source region 107. In which the source region 107 and the planar gate structure are self-aligned. The source region 107 is an n+ region (Nplus), and a photomask is used to define the formation region of the source region 107 in the step of forming the source region 107, so in fig. 1, step S107 is also denoted as Nplus photo & IMP.

Proceeding to step S108, comprising: an interlayer film 108 is formed, and a contact hole (Cont) 109 is formed through the interlayer film 108. In the process of forming the contact hole 109, a photolithography process is used to define a formation region of the contact hole 109, then etching is performed to form an opening of the contact hole 109, and then metal is filled in the opening of the contact hole 109 to form the contact hole. In the step of forming the contact hole 109, a photomask is used to define the formation area of the contact hole 109, so in fig. 1, step S108 is also denoted by contphoto & etch.

The method further comprises the step of performing P-type heavily doped ion implantation to form the body contact region 211 after opening the contact hole 109 and before filling the metal

Step S109 is performed, which includes: a front side metal layer (metal) 111 is formed and the front side metal layer 111 is patterned to form a source metal and a gate metal. In the step of forming the front Metal layer 111, a photomask is used to define the pattern area of the front Metal layer 111, so in fig. 1, step S109 is also denoted by Metal photo & etch.

As can be seen from fig. 1 and fig. 2, the P-type well region 106 needs to be implemented by photolithography definition and ion implantation, and in the photolithography process, the thickness, the exposure intensity, the developing process and the ion implantation process of the photoresist all have corresponding deviations, so that the dimension of the P-type well region 106 changes, that is, the dimension of the photolithography and the ion implantation processes changes; meanwhile, the photolithography overlay accuracy may also change the pattern position of the P-type well region 106.

Also, the planar gate structure needs to be realized by adopting photoetching definition and etching, and the planar gate structure can generate dimensional changes due to photoetching and etching process parameters and pattern position changes due to photoetching alignment precision in the same line.

On the same semiconductor substrate 101, the channel length Lc is changed by the dimensional change of the P-type well region 106 due to the photolithography and implantation process, the pattern position change due to the photolithography and etching process, and the pattern position change of the planar gate structure due to the photolithography and etching process. The channel length Lc has a great influence on the on-resistance, the threshold voltage, and the input capacitance, cgs, of the device, which affects the uniformity of the device performance, such as the uniformity of the channel length Lc, the on-resistance, the threshold voltage, and Cgs, is deteriorated.

Because JFET effects are easily generated in the N-type region between the channel regions, an anti-JFET implant is performed to form an anti-JFET region having an N-type impurity concentration higher than that of the N-type epitaxial layer 102, for example, by 1 order of magnitude or more, and a width Wj of the anti-JFET region directly affects the Cgd of the device. The width Wj also varies and therefore affects the uniformity of Cgd of the device.

The adverse effects of the prior art methods on device uniformity are described below in conjunction with specific parameters:

as can be seen from fig. 2, the width and position of the P-type well region 106 are determined by the photolithography process of the P-type well region 106, because the critical dimensions (Critical Dimension, CD) after photolithography vary with the thickness of the photoresist, the energy of the photolithography, the process of development, and the position of the pattern will always vary (for example, within +/-0.2 micrometers, depending on the size of the photolithography pattern, the process selection, etc.), and the overlay accuracy will also vary within a certain range (for example, 60nm-150 nm); similarly, the width of the polysilicon gate is also related to the photoetching process of the polysilicon gate, the etching process is changed within a certain range, and the photoetching alignment precision also fluctuates within a certain range. If a photoresist thickness of approximately 1 micron is used, using a 248nm lithography machine, the single layer width schedule may fluctuate + -0.1 micron, and if the overlay schedule fluctuates + -0.06 microns, the channel length Lc may fluctuate + -0.32 microns, taking into account the difference between the two layers of lithography, which has a significant impact on device uniformity for a 9 micron step (pitch) device, where the poly gate width is set to 7.5 microns (which has been considered in a very wide direction), and the single channel length Lc is designed to be 2-3 microns. If one should scale down the step of the superjunction to a level of 5 microns, for example, the step is set to be less than 3.5 microns, then the contact width is subtracted by 0.5 microns, the contact to poly edge spacing is 0.5 microns, then the width of the entire poly gate is only 3.5 microns, the single sided channel length Lc must be less than 1.7 microns, and this + -0.32 micron variation will result in very poor uniformity.

Even though this range of variation can be reduced by optimization of the lithography and etching processes, in particular the management of the process conditions, on the one hand these solutions require higher manufacturing costs, for example because of the photolithography with increased critical dimensions and overlay accuracy of the lithography process, resulting in an increased photolithography rework rate and increased manufacturing costs. While this variation or consistency must exist, the problem is increasingly accentuated as the superjunction step decreases.

Disclosure of Invention

The invention aims to provide a super junction device which can improve the consistency of the device. Therefore, the invention also provides a manufacturing method of the super junction device.

In order to solve the above technical problems, the super junction device provided by the present invention includes:

a superjunction structure is formed in the semiconductor substrate, the superjunction structure is formed by alternately arranging a plurality of first conductive type columns and second conductive type columns, and a superjunction unit is composed of one first conductive type column and one adjacent second conductive type column.

The structure of the superjunction device in the active region includes:

a planar gate structure formed on top of each of the first conductivity type pillars, the planar gate structure being of unitary construction; the planar gate structure is formed by laminating a gate dielectric layer and a gate conductive material layer.

The second well region is formed by annealing an ion implantation region of a second conductivity type taking the planar gate structure as a self-alignment condition; and the second well region is laterally diffused to the bottom region of the planar gate structure under the action of annealing treatment.

The channel region is formed by covering the second well region by the planar gate structure, and a self-aligned structure between the second well region and the planar gate structure is used for improving the uniformity of the device.

A further improvement is that the structure of the superjunction device in the active region further comprises:

and the first well region consists of ion implantation regions of the second conductivity type formed on the tops of the second conductivity type columns, and the forming region of the first well region is defined by photoetching.

In the lateral direction, a space is formed between the first well region and the side surface of the planar gate structure, the first well region is aligned with the side surface of the planar gate structure, or the first well region extends to the bottom of the planar gate structure.

The body region is formed by longitudinally superposing the first well region and the second well region, the junction depth of the first well region is larger than that of the second well region, and the doping concentration of the first well is smaller than that of the second well region, so that leakage current of the device is reduced.

In a further improvement, a dielectric protection ring is formed on the surface of the semiconductor substrate, the dielectric protection ring covers a transition area and a terminal area and opens the active area, the area surrounded by the dielectric protection ring is the active area, the transition area surrounds the periphery of the active area, and the terminal area surrounds the periphery of the transition area.

And an anti-JFET region is formed in the active region, and the anti-JFET region consists of an ion implantation region of a first conductivity type which is comprehensively formed on the surface of the super junction structure of the active region by taking the dielectric protection ring as a self-alignment condition.

The anti-JFET region is used for improving the first-conductivity-type doping concentration of the first-conductivity-type doping region and reducing the JFET effect.

The anti-JFET region is used for compensating second-conductivity-type doped impurities of the first P well in the surface area of the active region at the same time in the second-conductivity-type doped region so as to reduce the influence of the first P well on the second-conductivity-type doped in the surface area of the active region, and the second-conductivity-type doped in the channel region is determined by the second well region.

A further improvement is that a heavily doped source region of the first conductivity type is formed on the surface of the body region, the source region and the planar gate structure being self-aligned.

A further improvement is that the first well region covers at least the center position of the second conductive type column and the width of the first well region on both sides of the center position of the second conductive type column is 0.2 μm or more in the lateral direction; or the width of the first well region covering the second conductive type column is more than 1 micrometer to 2 micrometers.

In the longitudinal direction, the depth of the first well region is 1-2 microns; alternatively, the depth of the first well region is 2 microns or more.

When the depth of the first well region is 1-2 microns, the dielectric protection ring is formed by laminating a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxidation process and a deposition process, the thermal oxidation layer of the dielectric protection ring consumes the surface of the semiconductor substrate, the surface area of the first well region is removed in the process of removing the dielectric protection ring of the active region, and the doping concentration of the removed surface area of the first well region is higher than that of the bottom reserved area, so that the uniformity of devices is improved.

When the depth of the first well region is more than 2 microns, the dielectric protection ring is formed by superposing a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a deposition process, and the deposition dielectric layer of the dielectric protection ring reduces the thermal process of the device so as to reduce the specific on-resistance of the device.

A further improvement is that a second conductivity type ring is formed in the transition region, and the first well region and the second conductivity type ring have the same process structure.

A further improvement is that the semiconductor substrate comprises a silicon substrate;

forming a first epitaxial layer doped with a first conductivity type on the surface of the semiconductor substrate;

the second conductive type column is composed of a second epitaxial layer doped with a second conductive type filled in the groove;

the first conductive type pillars are composed of the first epitaxial layer between the second conductive type pillars;

a spacing between a bottom surface of the second conductivity type pillar and a top surface of the semiconductor substrate is 5 microns or more for improving a body diode characteristic of the device;

the gate dielectric layer comprises a gate oxide layer;

the gate conductive material layer includes a polysilicon gate.

Further improvements are that the superjunction device comprises a superjunction MOSFET or a superjunction IGBT.

The super junction device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type; or the super junction device is a P-type device, the first conduction type is P-type, and the second conduction type is N-type.

In order to solve the technical problems, the manufacturing method of the super junction device provided by the invention comprises the following steps:

and firstly, forming a super junction structure in the semiconductor substrate, wherein the super junction structure is formed by alternately arranging a plurality of first conductive type columns and second conductive type columns, and a super junction unit consists of one first conductive type column and one adjacent second conductive type column.

And step two, defining an active region on the semiconductor substrate.

Forming a planar gate structure in the active region, wherein each planar gate structure is formed on the top of each first conductive type column, and the planar gate structure is of an integral structure; the planar gate structure is formed by laminating a gate dielectric layer and a gate conductive material layer.

And fourthly, performing ion implantation of a second conduction type to form a second well region by taking the planar gate structure as a self-alignment condition, and performing annealing treatment on the second well region, wherein the second well region is laterally diffused to the bottom region of the planar gate structure under the action of the annealing treatment.

In a further improvement, the first step further comprises the following steps of forming the first well region:

and photoetching to define a forming area of the first well region, wherein the first well region is positioned at the top of the second conductive type column in the active region.

And performing ion implantation of a second conductivity type to form the first well region.

Annealing and propelling the first well region; in the transverse direction, a space is reserved between the first well region and the side face of the planar gate structure after annealing is advanced, the first well region is aligned with the side face of the planar gate structure, or the first well region extends to the bottom of the planar gate structure.

The further improvement is that the step two comprises the following sub-steps:

and forming a material layer of the dielectric protection ring on the surface of the semiconductor substrate.

And photoetching to define a forming area of the active area.

And etching the material layer of the medium protection ring to form the medium protection ring, wherein the medium protection ring covers the transition area and the terminal area and opens the active area, the area surrounded by the medium protection ring is the active area, the transition area surrounds the periphery of the active area, and the terminal area surrounds the periphery of the transition area.

A further improvement is that after the completion of step two and before the performance of step three, the method comprises the steps of forming the anti-JFET region as follows:

and performing first conduction type ion implantation on the surface of the active region by taking the dielectric protection ring as a self-alignment condition to comprehensively form the anti-JFET region.

The further improvement is that the step four further comprises: ion implantation of first conductive type heavy doping taking the plane gate structure as a self-alignment condition is conducted in the active region to form a source region.

When the depth of the first well region is 1-2 microns, the dielectric protection ring is formed by adopting a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxidation process and a deposition process, the thermal oxidation layer of the dielectric protection ring causes the surface of the semiconductor substrate to be consumed, the surface area of the first well region is removed in the process of removing the dielectric protection ring of the active region, and the doping concentration of the removed surface area of the first well region is higher than that of a bottom reserved area, so that the uniformity of devices is improved;

A further improvement is that a second conductivity type ring is formed in the transition region, the first well region and the second conductivity type ring being formed simultaneously using the same process.

the gate dielectric layer comprises a gate oxide layer;

the gate conductive material layer includes a polysilicon gate.

A further improvement is that, prior to step three, after the formation of the anti-JFET region, the anti-JFET region inverts the surface of the second conductivity type doped region to be doped of the first conductivity type.

In the prior art, the channel region is formed by an ion implantation region defined by a photomask, and the channel region is formed by a second well region which is self-aligned with a planar gate structure.

In addition, if the second well region which is self-aligned with the planar gate structure is independently adopted as the whole body region, the depth of the body region formed by independently adopting the second well region is shallower, and the electric leakage of the device is larger because the forming process of the second well region is limited by the planar gate structure; therefore, the invention can also form a body region together by adopting the first well region formed by the photomask before the basic gate of the second well region is combined with the planar gate structure, thus improving the uniformity of the device by utilizing the second well region and reducing the leakage current of the device by utilizing the deeper junction depth of the first well region and the graded structure.

In addition, after the first well region is introduced into the body region, the first well region extends downwards from the surface of the active region, so that the first well region positioned on the surface of the active region can be used as a component of the channel region, the length of the channel region is affected, and finally the uniformity of the device is affected.

The region in the anti-JFET region, which actually generates the reduced JFET effect, is a region between the channel regions and covered by the planar gate structure, the width of the region is only influenced by the width of the planar gate structure, the width of the planar gate structure is influenced by photoetching and etching processes of the planar gate structure, and the photoetching registration accuracy of the planar gate structure does not influence the width of the anti-JFET region between the channel regions and covered by the planar gate structure, so that the uniformity of the gate-drain capacitance (Cgd) of the device is also greatly improved.

In addition, when the junction depth of the first well region is smaller, the surface region with higher doping concentration of the first well region can be removed through the thermal oxidation layer such as the thermal oxidation layer for forming the medium protection ring, so that adverse effects of the surface region with higher doping concentration of the first well region on the channel region are reduced, and the consistency of devices is further improved.

When the junction depth of the first well region is deeper, the deeper junction depth is utilized to slow down the doping concentration of the whole first well region, so that the doping concentration of the surface region of the first well region is also reduced, the adverse effect of the surface region of the first well region on the channel region can be reduced, and the consistency of devices is further improved.

Drawings

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

FIG. 1 is a schematic diagram of a prior art superjunction device;

FIG. 2 is a flow chart of a method of manufacturing a prior art superjunction device;

FIG. 3 is a schematic diagram of the structure of a superjunction device according to an embodiment of the present invention;

FIG. 4 is a flow chart of a method of fabricating a superjunction device according to an embodiment of the present invention;

fig. 5A to 5E are schematic views of device structures at each step in a method for manufacturing a superjunction device according to an embodiment of the present invention.

Detailed Description

FIG. 3 is a schematic structural diagram of a superjunction device according to an embodiment of the present invention; the superjunction device of the embodiment of the invention comprises:

a superjunction structure is formed in the semiconductor substrate 201, the superjunction structure being formed by alternately arranging a plurality of first conductive type pillars and second conductive type pillars 203, and a superjunction unit being composed of one of the first conductive type pillars and an adjacent one of the second conductive type pillars 203.

In an embodiment of the present invention, the semiconductor substrate 201 includes a silicon substrate. In general, a first conductive type epitaxial layer 202 is formed on the surface of the semiconductor substrate 201, and the first conductive type pillars are composed of the first conductive type epitaxial layer 202 between the second conductive type pillars 203.

The spacing between the bottom surface of the second conductivity-type pillars 203 and the top surface of the semiconductor substrate 201 is 5 microns or more, typically set to 5 microns to 10 microns, for improving the body diode characteristics of the device.

Only the structure of the superjunction device in the active region is shown in fig. 3, the structure of the superjunction device in the active region comprising:

a planar gate structure formed on top of each of the first conductivity type pillars, the planar gate structure being of unitary construction; the planar gate structure is formed by overlapping a gate dielectric layer 206 and a gate conductive material layer 207.

In some preferred embodiments, the gate dielectric layer 206 comprises a gate oxide layer.

The gate conductive material layer 207 includes a polysilicon gate.

A second well region 2042 formed by annealing an ion implantation region of a second conductivity type having the planar gate structure as a self-aligned condition; the second well region 2042 is laterally diffused into the bottom region of the planar gate structure by the annealing process. The second well region 2042 also diffuses longitudinally downward at the same time as the annealing process.

The channel region is formed by the second well region 2042 being covered by the planar gate structure, and the self-aligned structure between the second well region 2042 and the planar gate structure is used to improve device uniformity. In fig. 3, the length of the channel region is denoted by Lc, and the channel region is also the second well region 2042 between two straight lines corresponding to the channel length Lc in fig. 3. A conductive channel is formed after inversion of the surface of the channel region.

Because the second well region 2042 is limited by self-alignment with the planar gate structure, the junction depth of the second well region 2042 is shallow, and if the second well region 2042 is solely used as the body region 204, larger leakage current will occur, which is only applicable to occasions with low requirements for leakage current.

Preferably, in order to reduce leakage, a structure of the superjunction device in the active area according to the embodiment of the present invention further includes:

the first well region 2041 is composed of an ion implantation region of the second conductivity type formed on top of each of the second conductivity type pillars 203, and a formation region of the first well region 2041 is defined by photolithography.

In the lateral direction, there is a space between the first well region 2041 and the side surface of the planar gate structure, an alignment between the first well region 2041 and the side surface of the planar gate structure, or the first well region 2041 may extend to the bottom of the planar gate structure. In fig. 3, the first well region 2041 is shown with an overlap between the planar gate structure.

The body 204 is formed by vertically stacking the first well 2041 and the second well 2042, where the junction depth of the first well 2041 is greater than the junction depth of the second well 2042 and the doping concentration of the first well is less than the doping concentration of the second well 2042, so as to reduce the leakage current of the device. In fig. 3, the first well region 2041 is also denoted by P1 and the second well region 2042 is also denoted by P2.

In the embodiment of the present invention, the first well region 2041 is formed by photolithography definition and ion implantation and annealing and propulsion, and after the annealing and propulsion are completed, at least the following is ensured: in the lateral direction, the first well region 2041 covers at least the center position of the second conductivity type pillar 203 and the width of the first well region 2041 on both sides of the center position of the second conductivity type pillar 203 is 0.2 μm or more; alternatively, the first well region 2041 covers the second conductivity type pillars 203 with a width of 1 μm to 2 μm or more.

In the longitudinal direction, the depth of the first well region 2041 is 1 to 2 micrometers; alternatively, the depth of the first well region 2041 is 2 microns or more.

A dielectric guard ring (not shown) is formed on the surface of the semiconductor substrate 201, the dielectric guard ring covers a transition region and a terminal region and opens the active region, the region surrounded by the dielectric guard ring is the active region, the transition region surrounds the periphery of the active region, and the terminal region surrounds the periphery of the transition region.

The active region includes the super junction structure of the area surrounded by the dielectric guard ring, since the first well region 2041 may extend downward from the surface of the active region, when the doping concentration of the first well region 2041 on the surface of the active region is higher, the second well region 2042 on the surface of the active region may be adversely affected, and finally, uniformity of the size and doping concentration of the channel region may be affected. To this end, in some preferred embodiments, it can further comprise:

when the depth of the first well region 2041 is 1-2 micrometers, the dielectric guard ring is formed by laminating a thermal oxide layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxide layer formed by a deposition process, the thermal oxide layer of the dielectric guard ring consumes the surface of the semiconductor substrate 201, the surface area of the first well region 2041 is removed in the process of removing the dielectric guard ring of the active region, and the doping concentration of the removed surface area of the first well region 2041 is higher than that of the bottom reserved area, so as to improve the uniformity of the device.

When the depth of the first well region 2041 is more than 2 micrometers, the dielectric guard ring is formed by stacking a thermal oxide layer formed by a thermal oxidation process, a deposition dielectric layer formed by a deposition process or a deposition dielectric layer formed by a deposition process, and the deposition dielectric layer of the dielectric guard ring reduces the thermal process of the device so as to reduce the specific on-resistance of the device.

An anti-JFET region 205 is also formed in the active region, and the anti-JFET region 205 is composed of an ion implantation region of the first conductivity type formed on the surface of the superjunction structure of the active region in a self-aligned condition with the dielectric guard ring.

The anti-JFET region 205 is used to increase the first conductivity type doping concentration of the first conductivity type doped region to reduce the JFET effect.

The anti-JFET region 205 is used to compensate for the second conductivity type dopant impurities of the first well region 2041 at the same time in the second conductivity type dopant region of the active region surface region to reduce the effect of the first P-well on the second conductivity type dopant of the active region surface region, such that the second conductivity type dopant of the channel region is determined by the second well region 2042.

The super junction structure comprises the first conductive type column and the second conductive type column 203, so that the surface of the active region is distributed with a first conductive type doping region and a second conductive type doping region; after the first well region 2041 is formed on the surface of the active region, a second conductivity type doped region on the surface of the active region is added. The anti-JFET region 205 can invert the second conductivity type doped region to the first conductivity type entirely prior to formation of the first well region 2042, and obviously, can eliminate the adverse effect of the surface area of the first well region 2041 on the channel region, thereby improving device uniformity.

A heavily doped source region 208 of the first conductivity type is formed on the surface of the body region 204, the source region 208 and the planar gate structure being self-aligned.

A second conductivity type ring is formed in the transition region, and the process structures of the first well region 2041 and the second conductivity type ring are the same.

In an embodiment of the invention, the superjunction device comprises a superjunction MOSFET. Other embodiments can also be: alternatively, the superjunction device is a superjunction IGBT.

As shown in fig. 3, the front structure of the superjunction device further includes:

An interlayer film 209, a contact hole 210 passing through the interlayer film 209; a body contact region 211 consisting of a heavily doped region of the second conductivity type is also formed at the bottom of the contact hole 210 at the top of the source region 208, so that the body region 204 is connected to the contact hole 210 at the top through the body contact region 211 together with the source region 208.

Source metal and gate metal are patterned from the front side metal layer 212.

The back structure of the superjunction device comprises:

thinning the semiconductor substrate 201, and forming a drain region; the drain region is directly formed by thinning the heavily doped semiconductor substrate 201, or is formed by back side ion implantation of the first conductivity type heavily doped semiconductor substrate 201.

A back metal layer 213 is formed on the back of the drain region, and the drain is composed of the back metal layer 213.

In the embodiment of the invention, the super junction device is an N-type device, the first conduction type is N-type, and the second conduction type is P-type. In other embodiments can also be: the super junction device is a P-type device, the first conductive type is P-type, and the second conductive type is N-type.

In the embodiment of the invention, the channel region is formed by adopting a second well region 2042 which is self-aligned with the planar gate structure, and the second well region 2042 is not required to be defined by adopting the photomask, so that the influence of a photoetching process on the pattern width and the photoetching alignment on the pattern position can be eliminated, namely the length of the channel region formed by the second well region 2042 is not influenced by the photoetching process and the photoetching alignment precision corresponding to the well region, and the length of the channel region is not influenced by the photoetching and etching processes and the photoetching alignment precision of a polysilicon gate, so that the length consistency of the channel region can be improved, the consistency of the on-resistance of a device and the consistency of threshold voltage can be improved, the consistency of a gate source capacitor (Cgs) can be improved, and finally the consistency of the device can be greatly improved.

In addition, if the second well region 2042 self-aligned to the planar gate structure is adopted alone as the whole body region 204, the depth of the body region 204 formed by adopting the second well region 2042 alone is shallower, and the device leakage is larger because the formation process of the second well region 2042 is limited by the planar gate structure; therefore, the body region 204 can also be formed by using the first well region 2041 formed by using a photomask before the base gate of the second well region 2042 is combined with the planar gate structure, so that the uniformity of the device can be improved by using the second well region 2042, and the leakage current of the device can be reduced by using the deeper junction depth and the graded structure of the first well region 2041.

In addition, after the first well region 2041 is introduced into the body region 204, the first well region 2041 may extend downward from the surface of the active region, so that the first well region 2041 located on the surface of the active region may be used as a component of the channel region, thereby affecting the length of the channel region and finally affecting the uniformity of the device.

The region of the anti-JFET region 205 where the JFET effect is actually reduced is a region between the channel regions covered by the planar gate structure, where the width of the region is only affected by the width of the planar gate structure, and the width of the planar gate structure is affected by the photolithography and etching processes of the planar gate structure, so that the photolithography alignment accuracy of the planar gate structure does not affect the width of the anti-JFET region 205 between the channel regions covered by the planar gate structure, and the uniformity of the gate-drain capacitance (Cgd) of the device is also greatly improved.

In addition, when the junction depth of the first well region 2041 is smaller, the surface region with higher doping concentration of the first well region 2041 can be removed through a thermal oxide layer, such as a thermal oxide layer for forming a dielectric protection ring, so that adverse effects of the surface region with higher doping concentration of the first well region 2041 on a channel region are reduced, and uniformity of devices is further improved.

When the junction depth of the first well region 2041 is deeper, the deeper junction depth is utilized to slow down the doping concentration of the whole first well region 2041, so that the doping concentration of the surface region of the first well region 2041 is also reduced, thereby reducing the adverse effect of the surface region of the first well region 2041 on the channel region and further improving the uniformity of the device.

As can be seen from the above, in the embodiment of the present invention, since the self-alignment is adopted, the second well region 2042 is not inconsistent in position due to the alignment progress, and is not different due to the different widths of the polysilicon gates. Therefore, the uniformity of the channel length of the device is obviously improved, the uniformity of the threshold voltage is improved, the uniformity of the on-resistance is improved, and the uniformity of Cgs is improved. The width of the N-type anti-JFET region between channels with the Cgd size is directly influenced, and the width of the N-type anti-JFET region only changes along with the width change of a polysilicon gate, so that the influence of the alignment precision of the photoetching of the polysilicon gate and the size and the alignment precision of a Pwell in the prior art are eliminated, and the consistency is greatly improved.

The first well region 2041 in the embodiment of the present invention is set before the polysilicon gate in the process, and different depths can be obtained by adjusting the implantation energy, the annealing temperature and the annealing time according to the process requirements, and the leakage current Ids of the device can be reduced by increasing the depth generally. Meanwhile, because the impurity concentration of the first well region 2041 can be designed to be relatively low, particularly, by designing the dielectric guard ring such as the guard ring oxide film to be made of the thermal oxide film, the process will adsorb more P-type impurities of the first well region 2041 to the interface between the oxide film and SI, and the surface P-type impurity concentration with higher concentration will be depleted, only the P-type impurities pushed into the deeper position remain, thus further improving the uniformity of the device.

FIG. 4 is a flow chart of a method of fabricating a superjunction device according to an embodiment of the present invention; the steps are represented in fig. 4 using a mask level. Fig. 5A to 5E are schematic views of device structures in steps of a method for manufacturing a superjunction device according to an embodiment of the present invention; the manufacturing method of the superjunction device provided by the embodiment of the invention comprises the following steps:

first, step S201 is performed, where step S201 is used to form a Zero Mark (Zero Mark), and a photolithography (photo) plus etching (etching) process is required to form the Zero Mark, and in fig. 4, step S201 is also denoted by Zero photo & etching.

Step one, as shown in fig. 5A, a superjunction structure is formed in the semiconductor substrate 201, the superjunction structure is formed by alternately arranging a plurality of first conductivity type pillars and second conductivity type pillars 203, and a superjunction unit is composed of one first conductivity type pillar and one adjacent second conductivity type pillar 203.

In the method of the embodiment of the present invention, the semiconductor substrate 201 includes a silicon substrate. In general, a first conductive type epitaxial layer 202 is formed on the surface of the semiconductor substrate 201, and the first conductive type pillars are composed of the first conductive type epitaxial layer 202 between the second conductive type pillars 203.

In the method of the embodiment of the present invention, the second conductive type pillar 203 is formed by using a Trench (Trench) etching and Trench filling process, and step S202 in fig. 4 corresponds to step one, and step S202 in fig. 4 is also denoted by Trench photo & etch.

In the method of the embodiment of the present invention, as shown in fig. 5A, after the step one is completed, the step of forming the first well region 2041 further includes:

patterning the photoresist 301 using a photolithography process defines a formation region of the first well region 2041, and the first well region 2041 is located on top of the second conductivity type pillars 203 in the active region.

Ion implantation of the second conductivity type is performed to form the first well region 2041.

Annealing and advancing the first well region 2041; in the lateral direction, a space is provided between the first well region 2041 and the side surface of the planar gate structure after annealing, the first well region 2041 is aligned with the side surface of the planar gate structure, or the first well region 2041 extends to the bottom of the planar gate structure.

In the lateral direction, the first well region 2041 covers at least the center position of the second conductivity type pillar 203 and the width of the first well region 2041 on both sides of the center position of the second conductivity type pillar 203 is 0.2 μm or more; alternatively, the first well region 2041 covers the second conductivity type pillars 203 with a width of 1 μm to 2 μm or more.

Preferably, a second conductive type ring is formed in the transition region, and the first well region 2041 and the second conductive type ring are formed simultaneously using the same process. Taking an N-type device as an example, the second conductive type ring is a P-type ring (pring). Step S203 in fig. 4 corresponds to a process of forming the P-type ring and the first well region 2041, and in fig. 4, step S203 is also denoted by Pring photo & IMP, and IMP denotes ion implantation. In other embodiments can also be: the second conductivity type ring and the first well region 2041 are formed separately; alternatively, the formation process of the second conductivity type ring and the first well region 2041 is simultaneously canceled; alternatively, the formation process of the first well region 2041 is separately canceled, leaving the formation process of the second conductivity type ring.

Step two, an active region is defined on the semiconductor substrate 201.

In the method of the embodiment of the invention, the second step comprises the following sub-steps:

as shown in fig. 5B, a material layer (Gfield) 303 of a dielectric guard ring is formed on the surface of the semiconductor substrate 201.

And photoetching to define a forming area of the active area.

As shown in fig. 5C, the material layer 303 of the dielectric protection ring is etched to form the dielectric protection ring, the dielectric protection ring covers a transition region and a terminal region, and opens the active region, the area surrounded by the dielectric protection ring is the active region, the transition region surrounds the periphery of the active region, and the terminal region surrounds the periphery of the transition region.

In fig. 5A, surface 302 represents the surface of the active region. When the depth of the first well region 2041 is 1 to 2 micrometers, the doping concentration of the first well region 2041 is higher near the surface 302. In this case, in some preferred embodiments, the surface higher doping concentration of the first well region 2041 is removed by the following method, which includes: the dielectric guard ring is formed by laminating a thermal oxide layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxidation process and a deposition process, and the thermal oxide layer of the dielectric guard ring consumes the surface of the semiconductor substrate 201. As shown in fig. 5B, the surface 304 is located on the bottom surface of the material layer 303 of the dielectric guard ring, and it is obvious that the surface 304 is located below the surface 302, and the material of the semiconductor substrate 201 between the surface 302 and the surface 304 is oxidized, so that the surface area 2041a of the first well region 2041 is oxidized.

And removing the surface area 2041a of the first well region 2041 in the process of removing the dielectric protection ring of the active region, wherein the doping concentration of the removed surface area 2041a of the first well region 2041 is higher than that of the bottom reserved area, so as to improve the uniformity of the device. In fig. 5C, the surface of the active region is shown lowered to surface 304.

In other preferred embodiments, it can also be: when the depth of the first well region 2041 is 2 μm or more, the doping concentration of the first well region 2041 becomes weak near the surface 302 in fig. 5A after diffusion promotion. At this time, the dielectric protection ring is formed by superposing a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a deposition process or by superposing a deposition dielectric layer formed by a deposition process, and the deposition dielectric layer of the dielectric protection ring reduces the thermal process of the device so as to reduce the specific on-resistance of the device. That is, in this case, the material layer 303 of the dielectric protection ring may be formed by a plurality of processes, for example, when the material layer 303 of the dielectric protection ring is formed by depositing a dielectric layer, the thermal process of the device may be reduced, so that the specific on-resistance of the device may be reduced.

Step S204 in fig. 4 corresponds to step two, and since the mask of step two mainly involves lithography and etching of the material layer 303 of the dielectric guard ring, i.e., gfield, step S204 is also denoted by Gfield photo & etch in fig. 4.

As shown in fig. 5D, the method of the embodiment of the present invention includes the following steps of forming the JFET resistant region 205 after the completion of the second step and before the third step is performed:

and performing first conductivity type ion implantation on the surface of the active region by taking the dielectric protection ring as a self-alignment condition to comprehensively form the anti-JFET region 205.

The anti-JFET region 205 is used to compensate for the second conductivity type dopant impurities of the first P-well in the surface region of the active region at the same time in the second conductivity type dopant region to reduce the effect of the first P-well on the second conductivity type dopant in the surface region of the active region, so that the second conductivity type dopant of the channel region is determined by the subsequent second well region 2042.

As shown in fig. 5D, since the width of the first well region 2041 is greater than the width of the second conductivity type pillars 203, the second conductivity type doped region of the surface region of the active region is the surface region of the first well region 2041, and the first conductivity type doped region of the surface region of the active region is the surface region of the first conductivity type pillars between the first well regions 2041. After the anti-JFET region 205 is formed, the anti-JFET region 205 inverts the surface of the second conductivity type doped region to be doped with the first conductivity type, so that the entire surface area of the active region is doped with the first conductivity type, and taking an N-type device as an example, after the anti-JFET region 205 is formed, the surface of the active region is doped with the N-type, thereby preventing the P-type doping of the active region from adversely affecting the uniformity of the channel region.

Step S205 in fig. 4 corresponds to the step of forming the anti-JFET region 205, and step S205 in fig. 4 is also denoted by JFET IMP. As can be seen from comparing the flow chart corresponding to fig. 2, the method of the embodiment of the present invention changes the JFET IMP in flow, and the JFET IMP is not required to be defined by the mask, so the step S205 is located outside the mask flow.

Step three, as shown in fig. 5E, forming planar gate structures in the active region, where each planar gate structure is formed on top of each first conductivity type pillar, and the planar gate structures are in a monolithic structure; the planar gate structure is formed by overlapping a gate dielectric layer 206 and a gate conductive material layer 207.

In the method of the embodiment of the present invention, the gate dielectric layer 206 includes a gate oxide layer.

The gate conductive material layer 207 includes a polysilicon (poly) gate.

Step S206 in fig. 4 corresponds to step three, in which a mask is used to define the polysilicon, so in fig. 4, step S206 is also denoted by poly photo & etch.

Step four, as shown in fig. 5E, performing ion implantation of the second conductivity type with the planar gate structure as a self-aligned condition to form a second well region 2042, and performing annealing treatment on the second well region 2042, wherein the second well region 2042 is laterally diffused to the bottom region of the planar gate structure under the action of the annealing treatment.

The channel region is formed by the second well region 2042 being covered by the planar gate structure, and the self-aligned structure between the second well region 2042 and the planar gate structure is used to improve device uniformity.

The body 204 is formed by vertically stacking the first well 2041 and the second well 2042, where the junction depth of the first well 2041 is greater than the junction depth of the second well 2042 and the doping concentration of the first well is less than the doping concentration of the second well 2042, so as to reduce the leakage current of the device.

Step S207 in fig. 4 corresponds to step four, and step S207 in fig. 4 is also denoted by Pwell IMP. As can be seen from comparing the flow chart corresponding to fig. 2, the method of the embodiment of the present invention changes the flow of the Pwell IMP, and the Pwell IMP does not need to use the mask definition, so the step S207 is located outside the mask flow.

The fourth step further comprises the following steps:

as shown in fig. 3, ion implantation of a first conductivity type heavily doped with the planar gate structure as a self-aligned condition is performed in the active region to form a source region 208. Taking an N-type device as an example, the source region 208 is an n+ region (Nplus), and step S208 in fig. 4 corresponds to a process step of forming the source region 208, in which a photomask is used to define a forming region of the source region 208, so that step S208 is also denoted as Nplus photo & IMP in fig. 4.

After that, an interlayer film 209.

A contact hole (Cont) 210 is formed through the interlayer film 209. In the process of forming the contact hole 210, a photolithography process is used to define a formation region of the contact hole 210, then etching is performed to form an opening of the contact hole 210, and then metal is filled in the opening of the contact hole 210 to form the contact hole. Step S209 in fig. 4 corresponds to a process step of forming the contact hole 210, in which a mask is used to define a formation region of the contact hole 210, so in fig. 4, step S209 is also denoted by contphoto & etch.

A body contact region 211 consisting of a heavily doped region of the second conductivity type is also formed at the bottom of the contact hole 210 at the top of the source region 208, so that the body region 204 is connected to the contact hole 210 at the top through the body contact region 211 together with the source region 208. The body contact region 211 is formed by second conductive type heavily doped ion implantation after the opening of the contact hole 210 is opened.

A front side metal layer (metal) 212 is formed and the front side metal layer 212 is patterned to form source and gate metals. Step S210 in fig. 4 corresponds to a process step of forming the front Metal layer 212, in which a mask is used to define a pattern region of the front Metal layer 212, so in fig. 4, step S210 is also denoted by Metal photo & etch.

In the method of the embodiment of the invention, the super junction device is a super junction MOSFET. Other embodiments of the method can also be: the superjunction device is a superjunction IGBT.

After the front side process is completed, the following back side process is further included:

In the method of the embodiment of the invention, the super junction device is an N-type device, the first conduction type is N-type, and the second conduction type is P-type. Other embodiments of the method can also be: the super junction device is a P-type device, the first conductive type is P-type, and the second conductive type is N-type.

The method of the embodiment of the invention is further described with specific parameters:

taking a 600V N-type superjunction MOSFET as an example, a Superjunction (SJ) structure with a step of 9 microns is used, the top trench width is set to 4 microns, and the top N-type epitaxial layer width is set to 5 microns.

The semiconductor substrate 201 is a high concentration substrate with a resistivity of 0.001-0.003ohm.

The first conductivity type epitaxial layer, i.e., N-type epitaxial layer 202, may be set as follows:

the thickness of N-type epitaxial layer 202 may be 50 microns or other values within 45-55 microns.

If the trenches of the second conductivity type pillars, i.e., P-type pillars 203, are very close to vertical, e.g., at an angle of between 89-90 degrees, then N-type epitaxial layer 202 may be selected to have a single layer N-type epitaxy with a resistivity of 1-1.5 ohm-cm:

if the P-type trench has a certain inclination angle, for example, between 88 and 89 degrees, the P-type trench can be designed into an epitaxial layer with different resistivity according to the central value of the inclination angle of the trench, and the epitaxial layer is mainly designed to ensure that the upper region and the lower region of the trench can obtain better charge balance as much as possible, so that higher breakdown voltage (BVDss) or better BVDss and specific on-resistance (Rsp) balance can be obtained. For example, if the P-type trench of the device is implemented by first depositing 20-30 microns of an N-type epitaxial layer having a resistivity of 1.5 ohm-cm on a high concentration N-type substrate, then depositing a 30-20 micron resistivity of 1.25 ohm-cm N-type epitaxial layer, maintaining the overall N-type epitaxial layer thickness at 50 microns

For a P-type trench with a certain inclination angle, another epitaxy setting scheme is to adopt a PN structure with continuously changing N-type impurity concentration, for example, for a device with the P-type column thickness of 40 micrometers, a resistivity of 1 ohm with 10 micrometers thickness can be designed to be deposited on an N-type high-concentration substrate, then an N-type epitaxy with the thickness of 40 micrometers is deposited, the N-type impurity concentration is continuously changed, the change of the resistivity of the N-type epitaxy is designed according to PN balance on each horizontal plane, namely, the central value of the inclination angle of the P-type column is further improved, the N-type impurity concentration of the top and the bottom reaching charge balance is calculated, and then the resistivity of other positions in the middle is linearly changed between the two values. Setting the concentration of the P-type impurities in the grooves to be consistent, wherein the size of the P-type column is large at the top, the concentration of the N-type impurities requiring charge balance is high, and the resistivity is low; the bottom is small, the concentration of N-type impurities requiring charge balance is low, and the resistivity is high, so that the N-type resistivity can linearly increase from the top to the bottom of the PN column.

The first step of forming the super junction structure mainly comprises forming the P-type column 203 by trench lithography and etching, trench P-type epitaxial filling and planarization

A dielectric film may be deposited on the N-type epitaxial layer 202, where the dielectric film may be a single oxide film, for example, an oxide film having a thickness exceeding 1 micron, and may be used as a hard mask during trench etching, and a certain thickness of oxide film may be left after the trench is formed, for example, an oxide film having a thickness of 0.1-0.2 microns, and during the process of performing the epitaxial filling, the oxide film may be used as a protective layer for N-type epitaxy during CMP, so that SI at the location is not damaged by the CMP process, resulting in leakage or quality problems.

The dielectric film can also be composed of an oxide film with the thickness of 0.1-0.15 microns, an SIN film with the thickness of 0.1-0.2 microns and an oxide film with the thickness of more than 1um on top, so that uniformity can be better controlled in the manufacturing process: for example, after the trench etching is completed, at least a part of the SIN remains on the underlying oxide film, and the SIN is removed before the epitaxial growth, so that the uniformity of the oxide film before the epitaxial growth is good and the uniformity of CMP in the outer eye can be improved.

A further improvement to the above-described multilayer film structure is that the first oxide film is formed by thermal oxidation, which further improves uniformity.

Here, in the P-type filling process, if the trench is very vertical, for example, 89-90 degrees, then epitaxy with a single concentration of impurity concentration can be used; if the P-type trench has a tilt angle, for example, between 88-89 degrees, the P-type impurity concentration in the trench can be divided into different segments according to the optimal charge balance requirement, whether the N-type epitaxy uses a single resistivity or two resistivities. P-type epitaxy with different resistivity is adopted. For example, if N-type epitaxial layer 202 is a single layer, then a high concentration P-type epitaxial layer, which is low resistivity, may be filled at the bottom of the trench and a higher resistivity P-type epitaxial layer may be filled at the top of the trench. If the N-type impurity concentration has set a continuously varying resistivity according to the trench tilt angle, then the P-type epitaxy may employ a single resistivity. The goal is to obtain the best balance of BVdss and Rsp.

In the process steps of forming the first well region 2041 and the P-type ring: by P-type ring lithography, a P-type ring of the transition region is defined, and a region of the first well region 2041 is defined. The P-ring surrounds the active area of the chip and may have a width of 1 micron to 50 microns, and in the case of a very wide gate bus, the P-ring may be widened accordingly because no additional chip area is added, and when the gate bus is small or even some areas do not have a gate bus, the P-ring may be reduced, and the design may be performed in consideration of the capability requirement of EAS. The first well region 2041 may have a certain overlap (overlap) with the later active region poly gate, may be aligned with the poly gate, or even have a certain distance from the poly gate, so long as it is ensured that, when the final process is completed, the first well region 2041 must cover the top 1-2 microns of the P-type pillar 203, or more, or at least cover the top 1-2 microns of the P-type pillar 203 in the longitudinal direction, and cover at least the region about 0.2 microns around the center of the trench in the lateral direction.

The P-type ring implant impurity may be B, BF2, or a combination thereof, the energy may be selected to be 30Kev-2Mev, which is the depth of the P-type column 203 that needs to be covered, and the temperature and time of the subsequent thermal process. The dosage can be 5E12-5E13 atomic number/cm ² The method comprises the steps of carrying out a first treatment on the surface of the Designed as B60 keV 1E13/cm ² I.e. the implantation impurity is B, the implantation energy is 60keV, the implantation dosage is 1E13/cm ² 。

The second step of forming the dielectric protection ring comprises:

the dielectric guard ring will cover the transition region and the termination region except for the outermost n+ region, which is not necessarily required, but will be removed in the active region. In some embodiments, the material layer 303 of the dielectric guard ring is formed by thermal oxidation at a temperature of 850-1050 ℃ and a thickness of 8000-10000 angstroms, or at least partially formed from a thermal oxide film. Thus, the P-type impurity in the first well region 2041 implanted in advance is pushed into the Si depth direction, and at the same time, a part of Si on the surface, for example, 3500A to 4000A, which contains the implanted P-type impurity is oxidized.

At least the surface material layer 303 in the active region is completely removed by dielectric guard ring lithography and etching.

In the step of forming the anti-JFET region 205:

After the photoetching and etching of the dielectric protection ring are completed, the dielectric protection ring is used as a mask to perform at least full anti-JFET injection on the active region to form an N-type anti-JFET region 205 with higher concentration, wherein the injected N-type impurity can be phosphorus or arsenic. The method mainly forms a region with concentration higher than that of N-type epitaxial impurities on the surface of the silicon wafer, and reduces the Rsp of the device. Here, the process may compensate the P-type impurity on the surface of the first well region 2041 at the same time, so that the surface of the active region becomes N-type overall. Therefore, the influence of the first well region 2041 technology on the surface of the device is reduced, namely the influence on the performances such as the threshold voltage (Vth) of the device, which are caused by the photoetching critical dimension and the alignment precision of the first well region 2041 is reduced.

The process of forming the second well region 2042 includes the following parameters:

the ion implantation of the second well region 2042 is self-aligned with a polysilicon gate, and the impurity may be B, BF2, or a combination thereof. In the method of the embodiment of the invention, B is adopted; the energy and dose are set according to the threshold voltage requirement and the desired depth of the second well region 2042, for example: the ion implantation process parameters include: the implantation impurity is B, the implantation energy is 120keV-150keV, and the implantation dosage is 1E14-2E14/cm ² Vth obtained was between 2V-4V.

The thickness of the gate oxide film, i.e., the gate dielectric layer 206, is set to 700A to 1000A, and the temperature of the thermal oxide film is set to 850 c to 1050 c.

The polysilicon gate, i.e., the gate conductive material layer 207, is high-concentration N-type polysilicon doped in situ, and has a thickness of 4000 angstroms to 8000 angstroms, such as 4000 angstroms.

The ion implantation of the second well region 2042 can be performed after the photoresist removal by the polycrystalline lithography, or can be performed after the polycrystalline lithography etching is completed but before the photoresist removal. In the case of implantation with the photoresist left, a higher energy P-type ion implantation may be employed.

After the ion implantation of the second well region 2042 is completed, the second well region 2042 is pushed to a desired lateral and longitudinal position by an annealing process at 1000-1150 ℃ for 30-180 min.

In the process of forming the source region 208, the method includes:

after the polycrystalline electrode is formed, at least the source region 10 of the device is formed through n+ lithography and ion implantation, and meanwhile, a terminal n+ region can be formed in the outermost region of the terminal, the terminal peripheral n+ region can be used for preventing the surface inversion of the terminal region, the stability of the breakdown characteristic of the device is better improved, and the terminal peripheral n+ region can be omitted.

The N + implant of source region 208 may generally be formed by an AS or Phos implant, or a combination thereof. The implantation conditions are generally 30-100keV,1-5E15/cm ² The injection may be followed by activation by a thermal process at 9000-1050 ℃.

The process of forming the interlayer film 209 and the contact hole 210 includes:

the interlayer film 209 is deposited by using undoped oxide film and BPSG film, forming the opening of the contact hole 210 by photolithography and etching of the contact hole 210, and performing high-concentration P injection after forming the opening of the contact hole 210 to form a body contact region 211 with a high-concentration P-type region, thereby ensuring good ohmic contact between the metal and the body region 204. The injection impurity of the body contact region 211 can be B, BF2, the injection energy is set to 20-60keV, and the dose is set to 1E13-3E15/cm ² . After ion implantation, thermal processes at 690-900 ℃ can be used for activation.

In the opening etching of the contact hole 210, silicon in the high concentration region of n+ impurity at the bottom of the interlayer film 209 can be etched, the etching amount can be 2000 to 4000 angstroms, and the thickness of the interlayer film is generally 6000 to 10000 angstroms according to the n+ implantation condition, i.e., implantation energy and dose.

The process of forming the interlayer film 209, the contact hole 210, and the front metal layer 212 includes:

The interlayer film 209 can be deposited by adopting the combination of undoped oxide film and BPSG film, then forming the opening of the contact hole 210 by photoetching and etching the contact hole 210, and then carrying out high-concentration P injection after forming the opening of the contact hole 210 to form a body contact region 211 consisting of a high-concentration P type region so as to ensure good ohmic contact between metal and the body region 204, wherein the injection impurity of the body contact region 211 can be B, BF2 and injection energySetting 20-60keV, and setting dosage to 1E13-3E15/cm ² . After ion implantation, thermal processes at 690-900 ℃ can be used for activation.

The metal filled in the opening of the contact hole 210 can employ: ti and TiN and W, after which W is etched back or CMP. Thereafter, alSi is performed to deposit a front side metal layer 212 on the front side of the wafer. In a preferred embodiment, the width of the contact hole 210 is set to 0.5 μm, the thickness of the interlayer film 209 is set to 8000-10000 angstrom, and the contact hole 210 is formed by filling and etching back Ti/TIN plus W or CMP.

If the contact hole 210 is large enough, ti, tiN, alCu or AlSiCu, or AlSiCu deposition can be used to directly fill the opening of the contact hole 210 and form the front side metal layer 212, and then the front side metal layer 212 is subjected to photolithography to form the active region source metal and the gate metal. The thickness of the barrier layer can be Ti

TiN

The thickness of AlCu or AlSiCu metal is generally 4-6 μm.

Then, the back surface of the silicon wafer 201 is thinned, and then a back metal layer 213 is deposited on the back surface to form a drain electrode.

Such a superjunction MOSFET device is formed.

In some embodiments, after the silicon wafer, that is, the front-side metal layer 212 of the semiconductor substrate 201 is formed, deposition and photolithography of a passivation film and etching can be further performed, or photolithography of polyimide (polyimide) is further performed, and then back-side thinning and deposition of the back-side metal layer 213 are further performed, so as to further improve the reliability of the device. Passivation film thickness is generally

Can be an oxide film, SIN, sia, or a combination thereof. The Polyimide is typically 5-10 microns thick after being subjected to a high temperature bake (bak). The passivation film and polyimide both cover the termination region and the boundary of the front side metal layer 212, typically 5-10 microns, and form a 0-10 micron guard over the scribe line edges.

In a modified example method, the following process parameters can be used:

the photoresist in the formation process of the first well region 2041 has a thickness of more than 3 micrometers, and the P-type implantation of the first well region 2041 has a thickness of 1.5-2Mev, so that the peak concentration of the ion implantation is more than 1 micrometer away from the Si surface, thereby keeping the junction depth of the least first well region 2041 more than 2 micrometers, and reducing the leakage current Idss of the device

In a modified example method, the following process parameters can be used:

after the P-type implantation of the first well region 2041 is completed and before the dielectric guard ring is formed, a high-temperature well pushing process is added, for example, annealing at a temperature of 1000-1150 ℃ for 30-180 minutes is adopted, so that the depth of the region of the first well region 2041 is pushed to a position which is 2 microns or deeper from the surface of Si, the P-type well impurity distribution of the first well region 2041 is reduced and slowly changed in the depth direction, the leakage current Ids of the device is further reduced, and the characteristics of the body diode of the device are improved

In a modified example method, the following process parameters can be used:

the photoresist in the formation process of the first well region 2041 has a thickness of more than 3 micrometers, the P-type implantation of the first well region 2041 has a thickness of 1.5-2Mev, so that the position of the peak concentration of the ion implantation is more than 1 micrometer away from the Si surface, thereby keeping the junction depth of the minimum Pwell more than 2 micrometers, and meanwhile, the material layer of the dielectric protection ring adopts a deposited dielectric film instead of a thermal oxide film, thereby reducing the thermal process of the process flow and improving the Rsp of the device.

In a modified example method, the following process parameters can be used:

after the P-type implantation of the first well region 2041 is completed and before the dielectric guard ring is formed, a high-temperature well pushing process is added, for example, annealing at a temperature of 1000-1150 ℃ for 30-180 minutes is adopted, the depth of the region of the first well region 2041 is pushed to a position which is 2 micrometers or deeper from the surface of Si, the P-type well impurity distribution of the first well region 2041 is reduced and changed slowly in the depth direction, the leakage current Ids of the device is further reduced, and the characteristics of the device body diode are improved. Meanwhile, the material layer of the dielectric protection ring adopts a deposited dielectric film instead of a thermal oxide film, so that the thermal process of the process flow is reduced.

In a modified example method, the following process parameters can be used:

in the process of forming the first well region 2041, the overlap of the first well region 2041 and the polysilicon gate can be set to be between 0.32 and 0.5 micrometers, so that under normal control of the process, the overlap of 0 micrometers or more is ensured between the first well region 2041 and the polysilicon gate of all the cells, and the uniformity of electric leakage Idss of the device can be improved.

In a modified example method, the following process parameters can be used:

In the fourth step, the ion implantation of the second well region 2042 can be performed with high energy implantation, for example, the energy of the B ion implantation is higher than 1Mev, so that increasing the implantation energy can increase the effective channel length of the device, and reduce the leakage current Idss of the device

In a modified example method, the following process parameters can be used:

the formation process of the first well region 2041 is omitted, that is, step S203 in fig. 4 is omitted, and only the second well region 2042 is formed as the body region by the self-aligned process, so that the leakage ids of the device increases, but the uniformity of the switching characteristics, vth, on-resistance (Rdson) and the like further increases.

In a modified example method, the following process parameters can be used:

the formation process of the first well region 2041 is canceled, but the step S203 in fig. 4 is retained, in which step S203, a P-type ring is formed only in the transition region, the first well region 2041 is not formed in the active region, and only the second well region 2042 is formed as the body region by using the self-aligned process, so that the leakage ids of the device increases, but the uniformity of the switching characteristics, vth, rdson, etc. further increases.

The present invention has been described in detail by way of specific examples, but these should not be construed as limiting the invention. Many variations and modifications may be made by one skilled in the art without departing from the principles of the invention, which is also considered to be within the scope of the invention.

Claims

1. A superjunction device, comprising:

a superjunction structure is formed in the semiconductor substrate, the superjunction structure is formed by alternately arranging a plurality of first conductive type columns and second conductive type columns, and a superjunction unit consists of one first conductive type column and one adjacent second conductive type column;

the structure of the superjunction device in the active region includes:

a planar gate structure formed on top of each of the first conductivity type pillars, the planar gate structure being of unitary construction; the planar gate structure is formed by laminating a gate dielectric layer and a gate conductive material layer;

the second well region is formed by annealing an ion implantation region of a second conductivity type taking the planar gate structure as a self-alignment condition; the second well region is laterally diffused to the bottom region of the planar gate structure under the action of annealing treatment;

2. The superjunction device of claim 1, wherein the structure of the superjunction device in the active region further comprises:

A first well region composed of ion implantation regions of a second conductivity type formed on top of each of the second conductivity type pillars, the formation region of the first well region being defined by photolithography;

in the transverse direction, a space is arranged between the first well region and the side surface of the planar gate structure, the first well region is aligned with the side surface of the planar gate structure, or the first well region extends to the bottom of the planar gate structure;

3. The superjunction device of claim 2, wherein: a medium protection ring is formed on the surface of the semiconductor substrate, the medium protection ring covers a transition area and a terminal area and opens the active area, the area surrounded by the medium protection ring is the active area, the transition area surrounds the periphery of the active area, and the terminal area surrounds the periphery of the transition area;

an anti-JFET region is formed in the active region, and consists of an ion implantation region of a first conductivity type which is comprehensively formed on the surface of the super junction structure of the active region by taking the dielectric protection ring as a self-alignment condition;

The anti-JFET region is used for improving the first conduction type doping concentration of the first conduction type doping region and reducing the JFET effect;

4. The superjunction device of claim 3, wherein: and forming a heavily doped source region of the first conductivity type on the surface of the body region, wherein the source region and the planar gate structure are self-aligned.

5. The superjunction device of claim 3, wherein: in the transverse direction, the first well region at least covers the central position of the second conductive type column and the width of the first well region at two sides of the central position of the second conductive type column is more than 0.2 micrometers; or the width of the first well region covering the second conductive type column is more than 1-2 microns;

6. The superjunction device of claim 5, wherein: when the depth of the first well region is 1-2 microns, the dielectric protection ring is formed by laminating a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxidation process and a deposition process, the thermal oxidation layer of the dielectric protection ring consumes the surface of the semiconductor substrate, the surface region of the first well region is removed in the removing process of the dielectric protection ring of the active region, and the doping concentration of the removed surface region of the first well region is higher than that of a bottom reserved region for improving the uniformity of devices;

7. The superjunction device of claim 6, wherein: and a second conductive type ring is formed in the transition region, and the first well region and the second conductive type ring have the same process structure.

8. The superjunction device of claim 1, wherein: the semiconductor substrate comprises a silicon substrate;

the gate dielectric layer comprises a gate oxide layer;

the gate conductive material layer includes a polysilicon gate.

9. The superjunction device of any of claims 1 to 8, wherein: the superjunction device comprises a superjunction MOSFET or a superjunction IGBT.

10. The superjunction device of claim 9, wherein: the super junction device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type; or the super junction device is a P-type device, the first conduction type is P-type, and the second conduction type is N-type.

11. A method of fabricating a superjunction device, comprising the steps of:

Forming a super junction structure in the semiconductor substrate, wherein the super junction structure is formed by alternately arranging a plurality of first conductive type columns and second conductive type columns, and a super junction unit consists of one first conductive type column and one adjacent second conductive type column;

step two, defining an active region on the semiconductor substrate;

forming a planar gate structure in the active region, wherein each planar gate structure is formed on the top of each first conductive type column, and the planar gate structure is of an integral structure; the planar gate structure is formed by laminating a gate dielectric layer and a gate conductive material layer;

performing ion implantation of a second conductivity type to form a second well region by taking the planar gate structure as a self-alignment condition, and performing annealing treatment on the second well region, wherein the second well region is laterally diffused to the bottom region of the planar gate structure under the action of the annealing treatment;

12. The method of fabricating a superjunction device of claim 11, wherein: the first step further comprises the following steps of forming a first well region:

Photoetching to define a forming area of the first well region, wherein the first well region is positioned at the top of the second conductive type column in the active region;

performing ion implantation of a second conductivity type to form the first well region;

annealing and propelling the first well region; in the transverse direction, a space is reserved between the first well region and the side surface of the planar gate structure after annealing is advanced, the first well region is aligned with the side surface of the planar gate structure, or the first well region extends to the bottom of the planar gate structure;

13. The method of fabricating a superjunction device of claim 12, wherein: the second step comprises the following sub-steps:

forming a material layer of a dielectric protection ring on the surface of the semiconductor substrate;

photoetching to define a forming area of the active area;

14. The method of fabricating a superjunction device of claim 13, wherein: after the second step is completed and before the third step is performed, the method comprises the following steps of forming an anti-JFET region:

performing first conduction type ion implantation on the surface of the active region by taking the dielectric protection ring as a self-alignment condition to comprehensively form the anti-JFET region;

15. The method of fabricating a superjunction device of claim 14, wherein: the fourth step further comprises the following steps: ion implantation of first conductive type heavy doping taking the plane gate structure as a self-alignment condition is conducted in the active region to form a source region.

16. The method of fabricating a superjunction device of claim 14, wherein: in the transverse direction, the first well region at least covers the central position of the second conductive type column and the width of the first well region at two sides of the central position of the second conductive type column is more than 0.2 micrometers; or the width of the first well region covering the second conductive type column is more than 1 micrometer to 2 micrometers.

17. The method of fabricating a superjunction device of claim 16, wherein: when the depth of the first well region is 1-2 microns, the dielectric protection ring is formed by laminating a thermal oxidation layer formed by a thermal oxidation process or a deposition dielectric layer formed by a thermal oxidation process and a deposition process, the thermal oxidation layer of the dielectric protection ring consumes the surface of the semiconductor substrate, the surface region of the first well region is removed in the removing process of the dielectric protection ring of the active region, and the doping concentration of the removed surface region of the first well region is higher than that of a bottom reserved region for improving the uniformity of devices;

18. The method of fabricating a superjunction device of claim 16, wherein: a second conductivity type ring is formed in the transition region, and the first well region and the second conductivity type ring are formed simultaneously using the same process.

19. The method of fabricating a superjunction device of claim 11, wherein: the semiconductor substrate comprises a silicon substrate;

the gate dielectric layer comprises a gate oxide layer;

the gate conductive material layer includes a polysilicon gate.

20. The method of fabricating a superjunction device of claim 14, wherein: and step three, before the formation of the anti-JFET region, the anti-JFET region inverts the surface of the second-conductivity-type doped region into first-conductivity-type doped regions.

21. A method of fabricating a superjunction device according to any of claims 11 to 20, characterised in that: the superjunction device comprises a superjunction MOSFET or a superjunction IGBT.

22. The method of fabricating a superjunction device of claim 21, wherein: the super junction device is an N-type device, the first conductivity type is N-type, and the second conductivity type is P-type; or the super junction device is a P-type device, the first conduction type is P-type, and the second conduction type is N-type.