A manufacturing method for a trench Schottky structure

Abstract

The present application provides a method for fabricating a trench Schottky structure, which relates to the field of semiconductor process technologies. First, trenches are etched on an epitaxial layer by using a patterned photoresist layer, then a dielectric layer is grown on the inner walls of the trenches, and then polysilicon is deposited along the surface of the epitaxial layer, where the polysilicon is located on the surface of the epitaxial layer and in the trenches. Then, the polysilicon on the surface of the epitaxial layer is oxidized to form an oxide layer. Then, contact holes are etched based on the oxide layer to expose the trenches. Finally, barrier metal and front metal are deposited based on the contact holes to form a trench Schottky structure. The method for fabricating a trench Schottky structure provided by the present application has the advantages of simple manufacturing process and cost savings in manufacturing.

Description

Technical Field

[0001] The present application relates to the field of semiconductor process technologies, and more particularly, to a method for fabricating a trench Schottky structure. Background Art

[0002] During the production of semiconductor devices, especially in the manufacture of trench Schottky devices, it is usually necessary to remove the polysilicon on the surface of the epitaxial layer while retaining the polysilicon in the trenches to enable subsequent processes.

[0003] Currently, the conventional manufacturing process is to remove the polysilicon on the surface of the epitaxial layer by means of polysilicon planarization after polysilicon filling.

[0004] However, since polysilicon planarization generally uses a dry etching process and requires dry etching equipment, its process cost is relatively high, and its process flow is also relatively complex.

[0005] In summary, in the prior art, when removing polysilicon, there are problems of high cost and complex process. Summary of the Invention

[0006] The purpose of the present application is to provide a method for fabricating a trench Schottky structure to solve the problems of high cost and complex process existing in the prior art when removing polysilicon.

[0007] To achieve the above purpose, the technical solutions adopted in the embodiments of the present application are as follows:

[0008] The embodiments of the present application provide a method for fabricating a trench Schottky structure, and the method for fabricating a trench Schottky structure includes:

[0009] Etching trenches on the epitaxial layer by using a patterned photoresist layer;

[0010] Growing a dielectric layer on the inner wall of the trench;

[0011] Depositing polysilicon along the surface of the epitaxial layer, where the polysilicon is located on the surface of the epitaxial layer and in the trench;

[0012] Oxidizing the polysilicon on the surface of the epitaxial layer to form an oxide layer;

[0013] Etching contact holes based on the oxide layer and exposing the trenches;

[0014] Depositing a barrier metal and a front metal based on the contact holes to form a trench Schottky structure.

[0015] Optionally, oxidizing the polysilicon on the surface of the epitaxial layer includes:

[0016] Oxidize all the polysilicon on the surface of the epitaxial layer, and do not oxidize the polysilicon in the trenches; or

[0017] Oxidize all the polysilicon on the surface of the epitaxial layer and the polysilicon at a preset depth in the trenches.

[0018] Optionally, when the photomask layer is a SiO2 layer, the step of etching the contact holes based on the oxide layer includes:

[0019] Etch the oxide layer and the photomask layer synchronously in a preset area to form contact holes.

[0020] Optionally, when the photomask layer is a non-SiO2 layer, the step of etching the contact holes based on the oxide layer includes:

[0021] First etch the oxide layer in a preset area, and then etch the photomask layer to form contact holes.

[0022] Optionally, the step of depositing a barrier metal and a front metal based on the contact holes to form a trench Schottky structure includes:

[0023] Deposit a barrier metal based on the contact holes;

[0024] Etch the barrier metal to etch out a preset pattern.

[0025] Optionally, the step of depositing a barrier metal and a front metal based on the contact holes to form a trench Schottky structure includes:

[0026] Deposit a front metal on the surface of the barrier metal;

[0027] Etch the front metal to etch out a preset pattern.

[0028] Optionally, the step of depositing a front metal on the surface of the barrier metal includes:

[0029] Deposit one or more metals of Al, Ti, Ni, and Ag on the surface of the barrier metal.

[0030] Optionally, the step of growing a dielectric layer on the inner wall of the trench includes:

[0031] Grow a SiO2 layer on the inner wall of the trench.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] The present application provides a method for fabricating a trench Schottky structure. First, a trench is etched on an epitaxial layer using a patterned photoresist layer. Then, a dielectric layer is grown on the inner wall of the trench. Next, polysilicon is deposited along the surface of the epitaxial layer, where the polysilicon is located on the surface of the epitaxial layer and inside the trench. Then, the polysilicon on the surface of the epitaxial layer is oxidized to form an oxide layer. Subsequently, contact holes are etched based on the oxide layer to expose the trench. Finally, a barrier metal and a front metal are deposited based on the contact holes to form a trench Schottky structure. Since, after depositing the polysilicon in the present application, the polysilicon on the surface of the epitaxial layer is oxidized, the polysilicon on the surface of the epitaxial layer can be transformed into an oxide layer for use, eliminating the need to deposit an additional oxide layer, simplifying the fabrication process, and saving the fabrication cost.

[0034] To make the above objects, features, and advantages of the present application more obvious and understandable, the following specific preferred embodiments are given, in conjunction with the accompanying drawings, and are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can be obtained based on these drawings.

[0036] Figure 1 It is a schematic cross-sectional view corresponding to the first step of fabricating a trench Schottky structure in the prior art.

[0037] Figure 2 It is a schematic cross-sectional view corresponding to the second step of fabricating a trench Schottky structure in the prior art.

[0038] Figure 3 It is a schematic cross-sectional view corresponding to the third step of fabricating a trench Schottky structure in the prior art.

[0039] Figure 4 It is a schematic cross-sectional view corresponding to the fourth step of fabricating a trench Schottky structure in the prior art.

[0040] Figure 5 It is a schematic cross-sectional view corresponding to the fifth step of fabricating a trench Schottky structure in the prior art.

[0041] Figure 6 It is a schematic cross-sectional view corresponding to the sixth step of fabricating a trench Schottky structure in the prior art.

[0042] Figure 7 It is a schematic cross-sectional view corresponding to the seventh step of fabricating a trench Schottky structure in the prior art.

[0043] Figure 8It is a schematic cross-sectional view corresponding to the eighth step of fabricating a trench Schottky structure in the prior art.

[0044] Figure 9 It is a schematic cross-sectional view corresponding to the ninth step of fabricating a trench Schottky structure in the prior art.

[0045] Figure 10 It is a schematic flow chart provided by an embodiment of the present application.

[0046] Figure 11 It is a schematic cross-sectional view corresponding to S104 in the method for fabricating a trench Schottky structure provided by an embodiment of the present application.

[0047] Figure 12 It is a schematic cross-sectional view corresponding to S106 in the method for fabricating a trench Schottky structure provided by an embodiment of the present application.

[0048] Figure 13 It is a schematic cross-sectional view corresponding to S108 in the method for fabricating a trench Schottky structure provided by an embodiment of the present application.

[0049] Figure 14 It is a schematic cross-sectional view corresponding to S110 in the method for fabricating a trench Schottky structure provided by an embodiment of the present application.

[0050] Figure 15 It is a schematic cross-sectional view corresponding to depositing a barrier metal in the method for fabricating a trench Schottky structure provided by an embodiment of the present application.

[0051] Figure 16 It is a schematic cross-sectional view corresponding to depositing a front metal in the method for fabricating a trench Schottky structure provided by an embodiment of the present application. Detailed Description of the Invention

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. The components of the embodiments of the present application described and illustrated herein can be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0054] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present application, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0055] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0056] The following will describe in detail some embodiments of the present application with reference to the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0057] As described in the background art, in the prior art, when performing polycrystalline etching, there are problems of high cost and complex process.

[0058] For example, Figures 1-9 shows a cross-sectional schematic diagram in the process of manufacturing a trench Schottky product in the prior art. As Figure 1 shown, after growing an epitaxial layer on a substrate, for a trench Schottky product, trenches need to be etched on the epitaxial layer. In the actual etching process, a mask layer is first deposited, then etching holes are made on the mask layer, and trenches are etched on the epitaxial layer based on the mask layer using an etching process.

[0059] As Figure 2 shown, after the trench etching is completed, the mask layer on the epitaxial layer needs to be removed, and at this time, an epitaxial layer with trenches is formed. Among them, two trenches are provided on the epitaxial layer shown in the figure, but in actual applications, the number of trenches is not limited. For example, the number of trenches can be 6 or 8. In the prior art, when removing the mask layer, watermarks are likely to be generated, affecting the performance of the manufactured trench Schottky product.

[0060] Please continue to refer to Figure 3 , after manufacturing the epitaxial layer with trenches, a field plate oxide layer is continuously grown on the surface of the epitaxial layer, where the field plate oxide layer is located on the inner wall of the trench and the surface of the epitaxial layer at this time. As Figure 4 shown, polysilicon is continuously grown, where the polysilicon is grown by a deposition method and the polysilicon is located in the trench and on the surface of the epitaxial layer. It should be noted that in order to ensure that the trench is filled with polysilicon, when growing polysilicon, its thickness can be relatively thick.

[0061] Please refer to Figure 5, after growing polysilicon, it is necessary to remove the polysilicon on the surface of the epitaxial layer, that is, adopt a polysilicon planarization process to remove the polysilicon on the surface of the epitaxial layer. Generally, in the prior art, polysilicon planarization can adopt the CMP (chemical mechanical polish) process or the dry etching process. Among them, the CMP process is the key process to achieve wafer surface planarization in the integrated circuit manufacturing process. Different from the traditional pure mechanical or pure chemical polishing methods, the CMP process realizes the removal of different materials on the wafer surface at the micron / nanometer level through the combination of surface chemical action and mechanical grinding technology, so as to achieve nanometer-level planarization of the wafer surface. The main working principle of CMP is that under a certain pressure and in the presence of a polishing liquid, the wafer to be polished makes a relative movement to the polishing pad. With the highly organic combination between the mechanical grinding action of nano-abrasives and the chemical action of various chemical reagents, the surface of the wafer to be polished can meet the requirements of high planarization, low surface roughness and low defects.

[0062] Dry etching is a technology for thin film etching using plasma. When the gas exists in the form of plasma, it has two characteristics: on the one hand, the chemical activity of these gases in the plasma is much stronger than that in the normal state. According to the different materials to be etched, by selecting the appropriate gas, it is possible to react with the material faster to achieve the purpose of etching and removal; on the other hand, the electric field can be used to guide and accelerate the plasma, so that it has a certain energy. When it bombards the surface of the material to be etched, it will knock out the atoms of the material to be etched, so as to achieve the purpose of etching by using physical energy transfer. Therefore, dry etching is the result of the balance of physical and chemical processes on the wafer surface.

[0063] However, using the CMP process requires special grinding equipment, and using the dry etching process requires dry etching equipment. Whether it is grinding equipment or dry etching equipment, their prices are relatively expensive. Therefore, the production cost of trench Schottky products is relatively high.

[0064] Please refer to Figure 6 , continue to deposit a dielectric layer on the surface of the epitaxial layer. This dielectric layer can be an SiO2 layer or a nitride layer, which is not limited here.

[0065] Continue to refer to Figure 7 , it is necessary to etch the dielectric layer to form contact holes. Of course, the field plate oxide layer on the surface of the epitaxial layer is also etched away together with the dielectric layer.

[0066] Continue to refer to Figure 8 And Figure 9, in order to achieve a Schottky contact, a barrier metal is continuously deposited on the surfaces of the epitaxial layer and the dielectric layer. A Schottky contact is formed between the barrier metal and the epitaxial layer. At the same time, in order to lead out pins during packaging, a front metal is continuously grown on the surface of the barrier metal, and then subsequent conventional manufacturing steps are continued, such as steps of fabricating a passivation layer, etc., to form a trench Schottky product, which will not be elaborated here.

[0067] The conventional manufacturing process of trench Schottky products is relatively mature, and the thickness of the dielectric layer can be adjusted arbitrarily. However, for the entire process, the entire process is relatively complex. Watermarks are likely to be generated when removing the hardmask after trench etching, and polycrystalline dry etching equipment and dielectric layer deposition equipment are required, resulting in a relatively high production cost of trench Schottky products.

[0068] In view of this, in order to solve the above technical problems, the present application provides a method for fabricating a trench Schottky structure, which simplifies the process and reduces the production cost by oxidizing and then removing the polysilicon on the surface of the epitaxial layer.

[0069] The following is an exemplary description of the method for fabricating a trench Schottky structure provided by the present application:

[0070] As an optional implementation manner, please refer to Figure 10 , the method for fabricating a trench Schottky structure includes:

[0071] S102, etching a trench on the epitaxial layer by using a patterned photoresist layer.

[0072] S104, growing a dielectric layer on the inner wall of the trench.

[0073] S106, depositing polysilicon on the surface of the epitaxial layer, where the polysilicon is located on the surface of the epitaxial layer and in the trench.

[0074] S108, oxidizing the polysilicon on the surface of the epitaxial layer to form an oxide layer.

[0075] S110, etching a contact hole based on the oxide layer and exposing the trench.

[0076] S112, depositing a barrier metal and a front metal based on the contact hole to form a trench Schottky structure.

[0077] Among them, similar to the prior art, when depositing polysilicon, the processes of trench etching, dielectric layer growth, and polycrystalline filling are also carried out, which will not be elaborated here. Different from the prior art, in this application, after etching the trench, there is no need to remove the photoresist layer, but directly deposit polysilicon, and then remove the photoresist layer in the subsequent process. In the prior art, the removal of the photoresist generally adopts the process of wet etching. Therefore, compared with the prior art, this application reduces one step of wet etching process at this time, thereby reducing the possibility of defect generation. It should be noted that the dielectric layer provided in this application can be an oxide layer or a nitride layer.

[0078] When the dielectric layer is an oxide layer, it can be a SiO2 layer. And when fabricating the dielectric layer, actually, the dielectric layer is first deposited along the surface of the epitaxial layer, and then the dielectric layer is etched. To form a dielectric layer connected to the inner wall of the trench, and the thickness of this dielectric layer is relatively thin.

[0079] Please refer to Figure 11 , after fabricating the dielectric layer, at this time, the inner wall of the trench is connected with the dielectric layer, and at the same time, the surface of the epitaxial layer is connected with the photoresist layer.

[0080] At this time, polysilicon is deposited along the surface of the epitaxial layer to form a structure as shown in Figure 12 . At this time, the polycrystalline is located in the trench and on the surface of the epitaxial layer. And the surface of the epitaxial layer is also connected with the photoresist layer.

[0081] As shown in Figure 13 , the polysilicon on the surface of the epitaxial layer is oxidized to form an oxide layer, so that in the subsequent process, there is no need to deposit an additional oxide layer, which simplifies the manufacturing process. At the same time, there is no need for an oxide layer deposition device, achieving the effect of reducing production costs.

[0082] It should be noted that during the oxidation process, the oxidation depth of the polysilicon needs to be controlled. As one implementation, all the polysilicon on the surface of the epitaxial layer can be oxidized, and the polysilicon in the trench is not oxidized. As another implementation, all the polysilicon on the surface of the epitaxial layer and the polysilicon at a preset depth in the trench are oxidized. For example, during the oxidation process, the polysilicon with a depth of 500 - 600 angstroms on the surface of the trench flush with the epitaxial layer can be oxidized simultaneously, which can be adjusted according to actual needs.

[0083] In other words, in this application, in order to prevent the polysilicon on the surface of the epitaxial layer from not being completely oxidized and affecting the subsequent etching process, it is necessary to ensure that the oxidation depth is greater than or equal to the thickness of the polysilicon on the surface of the epitaxial layer. At the same time, when removing the polysilicon on the surface of the epitaxial layer, it can also be directly removed by removing the oxide layer, improving the uniformity of polysilicon removal and the precise control of the polysilicon removal depth.

[0084] Please refer to Figure 14, continue to etch the contact holes based on the oxide layer and expose the trenches. At this time, only the oxide layer needs to be removed, and there is no need to use the equipment for removing polysilicon in the prior art. Therefore, the process is simpler and the cost is lower.

[0085] It should be noted that when the photolithography mask layer is a SiO2 layer, since the oxide formed by the oxidation of polysilicon is also SiO2, the steps of etching the contact holes based on the oxide layer include:

[0086] Etch the oxide layer and the photolithography mask layer synchronously in a preset area to form contact holes.

[0087] When the photolithography mask layer is a non - SiO2 layer, the steps of etching the contact holes based on the oxide layer at this time include:

[0088] Etch the oxide layer first in a preset area, and then etch the photolithography mask layer to form contact holes.

[0089] That is, if the materials of the oxide layer and the photolithography mask layer are the same, the oxide layer and the photolithography mask layer can be removed together when etching the contact holes. If the materials of the oxide layer and the photolithography mask layer are different, the oxide layer can be etched first and then the photolithography mask layer can be etched when etching the contact holes.

[0090] Such as Figure 15 and Figure 16 As shown, the barrier metal and the front - side metal can be deposited successively based on the contact holes. Among them, the barrier metal is used for the Schottky base, and the front - side metal is used as the packaging trace.

[0091] Optionally, in the actual process, S112 includes:

[0092] Deposit the barrier metal based on the contact holes;

[0093] Etch the barrier metal to etch out a preset pattern.

[0094] Then deposit the front - side metal on the surface of the barrier metal;

[0095] Etch the front - side metal to etch out a preset pattern.

[0096] And the front - side metal can be one or more of Al, Ti, Ni, and Ag.

[0097] It can be understood that the method for fabricating the trench Schottky structure provided by this application has at least the following beneficial effects:

[0098] First, since the photolithography mask layer is not directly removed after etching the trenches using the photolithography mask layer, one wet etching process is reduced.

[0099] Second, the oxidation process of polysilicon can effectively control the polycrystalline retention depth and uniformity.

[0100] Thirdly, the use of the oxidation process for polysilicon can reduce the surface damage of polysilicon.

[0101] Fourthly, the use of the oxidation process for polysilicon can reduce the first polysilicon etching and dielectric layer deposition, thereby reducing equipment investment and production costs, and at the same time simplifying the manufacturing process.

[0102] In summary, the present application provides a method for fabricating a trench Schottky structure. First, a trench is etched on an epitaxial layer using a patterned photoresist layer, then a dielectric layer is grown on the inner wall of the trench, and then polysilicon is deposited on the surface of the epitaxial layer. Among them, the polysilicon is located on the surface of the epitaxial layer and in the trench. Then, the polysilicon on the surface of the epitaxial layer is oxidized to form an oxide layer. Then, a contact hole is etched based on the oxide layer to expose the trench. Finally, a barrier metal and a front metal are deposited based on the contact hole to form a trench Schottky structure. Since the polysilicon on the surface of the epitaxial layer is oxidized after the polysilicon is deposited in the present application, the polysilicon on the surface of the epitaxial layer can be transformed into an oxide layer for use, without depositing an additional oxide layer, which simplifies the manufacturing process and saves the manufacturing cost at the same time.

[0103] The foregoing is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0104] For those skilled in the art, it is obvious that the present application is not limited to the details of the above-described exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present application is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present application. Any reference numerals in the claims should not be regarded as limiting the claimed rights.

Claims

1. A manufacturing method of a trench Schottky structure, characterized in that, The manufacturing method of the trench Schottky structure includes: Etching trenches on the epitaxial layer by using a patterned photoresist layer; Growing a dielectric layer on the inner wall of the trench; Depositing polysilicon on the surface of the epitaxial layer, where the polysilicon is located on the surface of the epitaxial layer and in the trench; Oxidizing the polysilicon on the surface of the epitaxial layer to form an oxide layer; When the photoresist layer is a SiO2 layer, etching the oxide layer and the photoresist layer synchronously in a preset area to form a contact hole; Depositing a barrier metal and a front metal based on the contact hole to form a trench Schottky structure.

2. The manufacturing method of the trench Schottky structure according to claim 1, characterized in that, Oxidizing the polysilicon on the surface of the epitaxial layer includes: Oxidizing all the polysilicon on the surface of the epitaxial layer and not oxidizing the polysilicon in the trench; or Oxidizing all the polysilicon on the surface of the epitaxial layer and the polysilicon at a preset depth in the trench.

3. The manufacturing method of the trench Schottky structure according to claim 1, characterized in that, The step of depositing a barrier metal and a front metal based on the contact hole to form a trench Schottky structure includes: Depositing a barrier metal based on the contact hole; Etching the barrier metal to etch out a preset pattern.

4. The manufacturing method of the trench Schottky structure according to claim 1, characterized in that, The step of depositing a barrier metal and a front metal based on the contact hole to form a trench Schottky structure includes: Depositing a front metal on the surface of the barrier metal; Etching the front metal to etch out a preset pattern.

5. The manufacturing method of the trench Schottky structure according to claim 4, characterized in that, The step of depositing a front metal on the surface of the barrier metal includes: Depositing one or more metals of Al, Ti, Ni, and Ag on the surface of the barrier metal.

6. The manufacturing method of the trench Schottky structure according to claim 1, characterized in that, The step of growing a dielectric layer on the inner wall of the trench includes: Growing a SiO2 layer on the inner wall of the trench.

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