Method of manufacturing deep trench isolation

Abstract

The application provides a manufacturing method of deep trench isolation. A substrate of a first conductive type is provided, impurity injection of a second conductive type is performed on the surface of the substrate to form a buried layer of the second conductive type; at least two layers of epitaxial layers of the second conductive type are formed, after each layer of the epitaxial layers is formed, impurity injection of the second conductive type is performed on the surface of the epitaxial layer to form a deep well of the second conductive type, annealing is performed after the deep well of the uppermost layer of the epitaxial layer is formed, so that the deep well is connected with the buried layer, and the diffusion of the implanted ions of the buried layer and the substrate in the whole annealing process is reduced by performing injection on each layer of the epitaxial layer; shallow trench isolation is formed on the epitaxial layer to define an active region, and then a deep trench isolation structure is formed. The deep well is connected with the buried layer by using less annealing, the up and down expansion of the deep well is reduced, the depth of the deep trench isolation structure is reduced accordingly, the up expansion of the heavily doped ions of the substrate is reduced, and therefore the thickness of the shallowly doped substrate can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a manufacturing method of deep trench isolation. BACKGROUND

[0002] Deep Trench Isolation (DTI) is an isolation technology in integrated circuit manufacturing, which uses photolithography and etching technology to create vertical insulating trenches on the silicon substrate to reduce the charge coupling and parasitic capacitance between adjacent active devices, and improve the circuit performance and stability.

[0003] The prior art DTI (Deep Trench Isolation) structure is shown in Figure 1 The DTI penetrates the P-type epitaxial layer 103 and the N-type buried layer 102 into the P-type substrate 101, and the P-type implantation at the bottom of the DTI prevents the N-type regions on both sides from passing through. The annealing temperature of the N-type buried layer 102 and the deep N-well 107 steps in the prior art DTI process is too high and the time is too long, causing the deep N-well 107 to diffuse upward and downward, and the P+ substrate to diffuse upward more, so that more upper epitaxial layers, substrate epitaxial layers and deeper DTIs are needed.

[0004] To solve the above problems, a new manufacturing method of deep trench isolation needs to be proposed. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a manufacturing method of deep trench isolation, which solves the problem that the annealing temperature of the buried layer and the deep well step in the DTI process of the prior art is too high and the time is too long, causing the deep well to diffuse upward and downward, and the substrate heavily doped ions to diffuse upward more, so that more upper epitaxial layers, substrate epitaxial layers and deeper DTIs are needed.

[0006] To achieve the above-mentioned purposes and other related purposes, the present application provides a manufacturing method of deep trench isolation, comprising:

[0007] Step one, providing a substrate of a first conductive type, performing impurity implantation of a second conductive type on the surface of the substrate to form a buried layer of the second conductive type;

[0008] Step two, forming at least two layers of epitaxial layer of the second conductive type, after each layer of the epitaxial layer is formed, performing impurity implantation of the second conductive type on the surface thereof to form a deep well of the second conductive type, and performing annealing after the deep well of the uppermost layer of the epitaxial layer is formed, so that the deep well is connected with the buried layer, and the diffusion of the implanted ions of the buried layer and the substrate is reduced during the entire annealing process by implanting each layer of the epitaxial layer;

[0009] Step three, forming shallow trench isolation on the epitaxial layer to define active region, then forming the deep trench isolation structure, the bottom of the deep trench isolation structure is formed with a doped region of the first conductive type, the deep trench isolation structure extends from the upper surface of the epitaxial layer into the substrate;

[0010] Step four, forming a second conductive type well and a second conductive type heavily doped region on the second conductive type well on the epitaxial layer by ion implantation.

[0011] Preferably, the first conductive type is P type and the second conductive type is N type.

[0012] Preferably, the epitaxial layer in step two is composed of first and second epitaxial layers stacked from bottom to top.

[0013] Preferably, the material of the shallow trench isolation in step three is spin-on glass, dense oxide formed by high density plasma chemical vapor deposition, silicon dioxide or double filling of silicon dioxide and silicon nitride.

[0014] Preferably, the material of the deep trench isolation structure in step three is polysilicon.

[0015] Preferably, the method of forming the deep trench isolation structure and the doped region in step three comprises: forming a deep trench by photolithography and etching; forming the doped region of the first conductive type on the bottom of the deep trench by ion implantation; forming the deep trench isolation structure filling the deep trench by deposition and polishing.

[0016] Preferably, the etching method in step three is dry etching.

[0017] Preferably, the polishing method in step three is chemical mechanical planarization polishing.

[0018] As described above, the method of manufacturing deep trench isolation of the present application has the following beneficial effects:

[0019] The present application connects deep well and buried layer with less annealing, reduces the extension of deep well, reduces the depth of deep trench isolation structure, reduces the extension of substrate heavy doping ions, and thus reduces the thickness of shallow doped substrate. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Deep trench isolation structure schematic diagram of prior art is shown;

[0021] Figure 2 Process flow schematic diagram of the present application is shown;

[0022] Figure 3A schematic diagram showing the formation of a buried layer according to the present application;

[0023] Figure 4 A schematic diagram showing the formation of a first epitaxial layer according to the present application;

[0024] Figure 5 A schematic diagram showing the formation of a second epitaxial layer according to the present application;

[0025] Figure 6 A schematic diagram showing the formation of a shallow trench isolation according to the present application;

[0026] Figure 7 A schematic diagram showing the formation of a deep trench isolation structure according to the present application;

[0027] Figure 8 A schematic diagram showing the formation of a second conductivity type well and a second conductivity type heavily doped region according to the present application. DETAILED DESCRIPTION

[0028] Other advantages and effects of the present application will be apparent to those skilled in the art from the above description of the embodiments of the present application. The present application can also be implemented or applied in other different embodiments, and the details in the present specification can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0029] Reference will now be made to Figure 2 The present application provides a method for manufacturing a deep trench isolation, comprising:

[0030] Step one, providing a substrate 101 of a first conductivity type, and performing an impurity implantation of a second conductivity type on the surface of the substrate 101 to form a buried layer 102 of the second conductivity type, forming a structure as shown in Figure 3

[0031] In some embodiments, the first conductivity type is P type, and the second conductivity type is N type. For example, the substrate 101 can be composed of a P-substrate 101 and a P+ substrate 101.

[0032] Step two, forming at least two layers of epitaxial layers of the second conductivity type, after each layer of epitaxial layer is formed, performing an impurity implantation of the second conductivity type on the surface of the epitaxial layer to form a deep well of the second conductivity type, and performing an annealing after the deep well of the uppermost layer of epitaxial layer is formed, so that the deep well is connected to the buried layer 102 by using less annealing, and the diffusion of implanted ions of the buried layer 102 and the substrate 101 in the whole annealing process is reduced by performing the implantation through each layer of epitaxial layer;

[0033] ​In some embodiments, the epitaxial layer in step two is composed of first and second epitaxial layers stacked from bottom to top, i.e. the first epitaxial layer is formed first, the first deep well 103-1 is formed by doping the first epitaxial layer, the structure as shown in Figure 4 is formed, then the second epitaxial layer is formed on the first epitaxial layer, the second deep well 103-2 is formed by doping the second epitaxial layer, the structure as shown in Figure 5 is formed. In other embodiments, the number of epitaxial layers can be more.

[0034] Step three, shallow trench isolation 104 is formed on the epitaxial layer to define the active region, the structure as shown in Figure 6 is formed, then the deep trench isolation structure 105 is formed, the bottom of the deep trench isolation structure 105 forms the doped region 106 of the first conductivity type, the deep trench isolation structure 105 extends from the upper surface of the epitaxial layer to the substrate 101, the structure as shown in Figure 7 is formed.

[0035] In some embodiments, the material of the shallow trench isolation 104 in step three is spin-on glass, dense oxide formed by high-density plasma chemical vapor deposition, silicon dioxide or double filling of silicon dioxide and silicon nitride.

[0036] In some embodiments, the material of the deep trench isolation structure 105 in step three is polysilicon.

[0037] In some embodiments, the method of forming the deep trench isolation structure 105 and the doped region 106 in step three includes: forming a deep trench by using photolithography and etching; forming the doped region 106 of the first conductivity type at the bottom of the deep trench by using ion implantation; forming the deep trench isolation structure 105 filling the deep trench by using deposition and grinding.

[0038] In some embodiments, the etching method in step three is dry etching.

[0039] In some embodiments, the grinding method in step three is chemical mechanical planarization grinding.

[0040] Step four, the second conductivity type well 107 and the second conductivity type heavily doped region 108 on the second conductivity type well 107 are formed on the epitaxial layer by using ion implantation, the structure as shown in Figure 8 is formed.

[0041] For example, the benchmark condition uses 1200C, 450min deep N-well diffusion condition, through simulation, the present application selects 1100C, 500min annealing and corresponding ion implantation condition, fits the existing doping profile, so that the deep N-well upper extension is reduced by 1.5um, the deep N-well lower extension is reduced by 3um, the deep trench isolation structure 105 depth can be reduced by 3um, the substrate 101 P+ upper extension is reduced by 3um, and the P- substrate 101 thickness can be reduced by 3um.

[0042] It should be noted that the diagrams provided in the embodiments only schematically illustrate the basic concepts of the present application, and only the components related to the present application are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The shapes, number and proportions of the components in actual implementation can be arbitrarily changed, and the component layout pattern can be more complex.

[0043] In summary, the present application connects the deep well and the buried layer with less annealing, reduces the deep well upper and lower extension, reduces the deep trench isolation structure depth, reduces the substrate heavily doped ion upper extension, and thus reduces the thickness of the shallowly doped substrate. Therefore, the present application effectively overcomes the shortcomings of the prior art and has high industrial utilization value.

[0044] The above embodiments only illustratively explain the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method of manufacturing a deep trench isolation, characterized by, At least comprising: Step one, providing a substrate of first conductive type, implanting impurities of second conductive type on the surface of the substrate to form a buried layer of second conductive type; Step two, forming at least two epitaxial layers of second conductive type, after forming each epitaxial layer, implanting impurities of second conductive type on the surface of the epitaxial layer to form a deep well of second conductive type, after forming the deep well of the uppermost epitaxial layer, annealing to connect the deep well with the buried layer, implanting through each epitaxial layer to reduce the diffusion of implanted ions of the buried layer and the substrate during the whole annealing process; Step three, forming shallow trench isolation on the epitaxial layer to define active region, then forming deep trench isolation structure, the bottom of the deep trench isolation structure is formed with a doped region of first conductive type, the deep trench isolation structure extends from the upper surface of the epitaxial layer to the substrate; Step four, forming a well of second conductive type and a heavily doped region of second conductive type on the well of second conductive type by ion implantation on the epitaxial layer.

2. The method of claim 1, wherein: The first conductive type is P type, and the second conductive type is N type.

3. The method of claim 1, wherein: The epitaxial layer in step two is composed of first and second epitaxial layers stacked from bottom to top.

4. The method of claim 1, wherein: The material of the shallow trench isolation in step three is spin-on glass, dense oxide formed by high-density plasma chemical vapor deposition, silicon dioxide or double filling of silicon dioxide and silicon nitride.

5. The method of claim 1, wherein: The material of the deep trench isolation structure in step three is polysilicon.

6. The method of manufacturing a deep trench isolation of claim 1, wherein: The method for forming the deep trench isolation structure and the doped region in step three comprises: forming a deep trench by photolithography and etching; forming the doped region of first conductive type on the bottom of the deep trench by ion implantation; forming the deep trench isolation structure filling the deep trench by deposition and polishing.

7. The method of claim 6, wherein: The etching method in step three is dry etching.

8. The method of claim 6, wherein: The polishing method in step three is chemical mechanical planarization polishing.

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