Manufacturing method of deep trench isolation

Abstract

The invention provides a manufacturing method of deep trench isolation, which comprises the following steps of: providing a substrate of a first conductive type, and performing impurity injection of a second conductive type on the surface of the substrate to form a buried layer of the second conductive type; forming at least two epitaxial layers of a second conductive type, after each epitaxial layer is formed, performing impurity injection of the second conductive type on the surface of the epitaxial layer to form a deep trap of the second conductive type, and after the deep trap of the uppermost epitaxial layer is formed, performing annealing to enable the deep trap to be connected with the buried layer, injection is carried out on each epitaxial layer, so that diffusion of ions injected into the buried layer and the substrate in the whole annealing process is reduced; shallow trench isolation is formed on the epitaxial layer to define an active region, and then a deep trench isolation structure is formed. According to the invention, the deep trap and the buried layer can be connected with less annealing, so that the upper and lower expansion of the deep trap is reduced, the depth of the deep trench isolation structure can be reduced, the upper expansion of the heavily doped ions of the substrate is reduced, and the thickness of the lightly doped substrate can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a manufacturing method for deep trench isolation. Background Art

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

[0003] Existing DTI (deep trench isolation) structures such as Figure 1 As shown, the DTI penetrates the P-type epitaxy 103 and the N-type buried layer 102 into the P-type substrate 101, and the P-type injection at the bottom of the DTI prevents the N-type regions on both sides from punching through. The annealing temperature of the N-type buried layer 102 and the deep N-well 107 step of 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, thus requiring more upper epitaxial layers, substrate epitaxial layers and deeper DTI.

[0004] In order to solve the above problems, it is necessary to propose a novel method for manufacturing deep trench isolation. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a manufacturing method for deep trench isolation, which is used to solve the problem that the annealing temperature of the buried layer and deep well steps in the DTI process in 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, thus requiring more upper epitaxial layers, substrate epitaxial layers and deeper DTI.

[0006] To achieve the above objectives and other related objectives, the present invention provides a method for manufacturing deep trench isolation, comprising:

[0007] Step 1: providing a substrate of the first conductivity type, and implanting impurities of the second conductivity type on the surface of the substrate to form a buried layer of the second conductivity type;

[0008] Step 2, forming at least two layers of epitaxial layers of the second conductivity type, after each epitaxial layer is formed, second conductivity type impurities are implanted on the surface thereof to form a second conductivity type deep well, and annealing is performed after the deep well of the top epitaxial layer is formed, so that the deep well is connected to the buried layer, and the diffusion of the implanted ions in the buried layer and the substrate during the entire annealing process is reduced by implanting each epitaxial layer;

[0009] Step 3, forming a shallow trench isolation on the epitaxial layer to define an active area, and then forming the deep trench isolation structure, wherein a doped region of a first conductivity type is formed at the bottom of the deep trench isolation structure, and the deep trench isolation structure extends from the upper surface of the epitaxial layer to the substrate;

[0010] Step 4: forming a second conductivity type well and a second conductivity type heavily doped region located on the second conductivity type well on the epitaxial layer by ion implantation.

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

[0012] Preferably, the epitaxial layer in step 2 consists of a first epitaxial layer and a second epitaxial layer stacked in sequence from bottom to top.

[0013] Preferably, the shallow trench isolation material 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 for forming the deep trench isolation structure and the doped region in step three includes: forming a deep trench by photolithography and etching; forming a doped region of the first conductivity type at the bottom of the deep trench by ion implantation; and forming a deep trench isolation structure filling the deep trench by deposition and grinding.

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

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

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

[0019] The present invention can connect the deep well with the buried layer with less annealing, so that the up and down expansion of the deep well is reduced, the depth of the deep trench isolation structure can be reduced, the up expansion of heavily doped ions in the substrate is reduced, and the thickness of the shallowly doped substrate can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown is a schematic diagram of a deep trench isolation structure in the prior art;

[0021] Figure 2 Shown is a schematic diagram of the process flow of the present invention;

[0022] Figure 3Shown is a schematic diagram of forming a buried layer according to the present invention;

[0023] Figure 4 It is a schematic diagram of forming a first epitaxial layer according to the present invention;

[0024] Figure 5 It is a schematic diagram showing the formation of the second epitaxial layer of the present invention;

[0025] Figure 6 It is a schematic diagram of forming shallow trench isolation according to the present invention;

[0026] Figure 7 It is a schematic diagram showing a deep trench isolation structure formed according to the present invention;

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

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] See also Figure 2 The present invention provides a method for manufacturing deep trench isolation, comprising:

[0030] Step 1: Provide a substrate 101 of a first conductivity type, and implant impurities of a second conductivity type into the surface of the substrate 101 to form a buried layer 102 of a second conductivity type. Figure 3 The structure shown;

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

[0032] Step 2: forming at least two epitaxial layers of the second conductivity type, and after each epitaxial layer is formed, second conductivity type impurities are implanted on its surface to form a second conductivity type deep well, and annealing is performed after the deep well of the top epitaxial layer is formed. The deep well can be connected to the buried layer 102 with less annealing, and the diffusion of implanted ions in the buried layer 102 and the substrate 101 is reduced during the entire annealing process by implanting each epitaxial layer;

[0033] In some embodiments, the epitaxial layer in step 2 is composed of a first epitaxial layer and a second epitaxial layer stacked in sequence from bottom to top, that is, the first epitaxial layer is first formed, and the first epitaxial layer is doped to form a first deep well 103-1, so as to form Figure 4 The structure shown in FIG. 1 is then formed on the first epitaxial layer, and the second epitaxial layer is doped to form a second deep well 103-2, forming a structure as shown in FIG. Figure 5 In other embodiments, the number of epitaxial layers may be greater.

[0034] Step 3: forming shallow trench isolation 104 on the epitaxial layer to define the active area, forming Figure 6 The structure shown in FIG. 1 is then formed into a deep trench isolation structure 105. A doped region 106 of the first conductivity type is formed at the bottom of the deep trench isolation structure 105. The deep trench isolation structure 105 extends from the upper surface of the epitaxial layer to the substrate 101, forming a structure as shown in FIG. Figure 7 The structure shown;

[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 for forming the deep trench isolation structure 105 and the doped region 106 in step three includes: forming a deep trench by photolithography and etching; forming a first conductive type doped region 106 at the bottom of the deep trench by ion implantation; and forming a deep trench isolation structure 105 filling the deep trench by deposition and grinding.

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

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

[0040] Step 4: Form a second conductivity type well 107 and a second conductivity type heavily doped region 108 located on the second conductivity type well 107 on the epitaxial layer by ion implantation, so as to form Figure 8 The structure shown.

[0041] For example, the benchmark conditions use the deep N-well diffusion conditions of 1200°C and 450 min. Through simulation, the present invention selects the annealing and corresponding ion implantation conditions of 1100°C and 500 min, and fits the existing doping cross-sectional view, so that the deep N-well upper expansion is reduced by 1.5um, the deep N-well lower expansion is reduced by 3um, the depth of the deep trench isolation structure 105 can be reduced by 3um, the substrate 101P+ upper expansion is reduced by 3um, and the P-substrate 101 thickness can be reduced by 3um.

[0042] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0043] In summary, the present invention can connect the deep well with the buried layer with less annealing, so that the up and down expansion of the deep well is reduced, the depth of the deep trench isolation structure can be reduced, the up expansion of the heavily doped ions in the substrate is reduced, and the thickness of the shallowly doped substrate can be reduced. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for manufacturing deep trench isolation, characterized in that: At least: Step 1: providing a substrate of the first conductivity type, and implanting impurities of the second conductivity type on the surface of the substrate to form a buried layer of the second conductivity type; Step 2, forming at least two layers of epitaxial layers of the second conductivity type, after each epitaxial layer is formed, second conductivity type impurities are implanted on the surface thereof to form a second conductivity type deep well, and annealing is performed after the deep well of the top epitaxial layer is formed, so that the deep well is connected to the buried layer, and the diffusion of the implanted ions in the buried layer and the substrate during the entire annealing process is reduced by implanting each epitaxial layer; Step 3, forming a shallow trench isolation on the epitaxial layer to define an active area, and then forming the deep trench isolation structure, wherein a doped region of a first conductivity type is formed at the bottom of the deep trench isolation structure, and the deep trench isolation structure extends from the upper surface of the epitaxial layer to the substrate; Step 4: forming a second conductivity type well and a second conductivity type heavily doped region located on the second conductivity type well on the epitaxial layer by ion implantation.

2. The method for manufacturing deep trench isolation according to claim 1, characterized in that: The first conductivity type is P type, and the second conductivity type is N type.

3. The method for manufacturing deep trench isolation according to claim 1, wherein: The epitaxial layer in step 2 is composed of a first epitaxial layer and a second epitaxial layer stacked in sequence from bottom to top.

4. The method for manufacturing deep trench isolation according to 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 for manufacturing deep trench isolation according to claim 1, wherein: The material of the deep trench isolation structure in step three is polysilicon.

6. The method for manufacturing deep trench isolation according to claim 1, characterized in that: The method for forming the deep trench isolation structure and the doped region in step three includes: forming a deep trench by photolithography and etching; forming a doped region of the first conductivity type at the bottom of the deep trench by ion implantation; and forming a deep trench isolation structure filling the deep trench by deposition and grinding.

7. The method for manufacturing deep trench isolation according to claim 6, wherein: The etching method in step three is dry etching.

8. The method for manufacturing deep trench isolation according to claim 6, wherein: The grinding method in step three is chemical mechanical planarization grinding.

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