Methods to improve the effect of BPSG on contact resistance

Abstract

This invention discloses a method for improving the influence of BPSG on contact resistance. Before ion implantation into contact holes or trenches on the wafer, a rapid thermal annealing step is performed to form an oxide film on the sidewalls of the trenches or contact holes in the BPSG layer. Then, the contact hole ion implantation and annealing processes are performed. By forming an oxide film as a barrier layer, impurity ions are confined within the BPSG layer before ion implantation and annealing. This avoids impurity diffusion within the BPSG layer and improves device reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device manufacturing, and in particular to a method for improving the effect of BPSG on contact resistance. Background Technology

[0002] Automotive superjunction MOS devices have high requirements for reverse recovery capability after packaging. The B / P doping in BPSG (borophosphosilicate glass) will diffuse during the annealing process of contact hole injection, affecting the doping concentration at the sidewall of the contact hole. This manifests as unstable contact resistance of the contact hole in the wafer plane, ultimately leading to failure of reverse recovery test at the application end.

[0003] One solution is to increase the implantation dose in the heavily doped N-type implantation region and the implantation dose in the contact holes, which can effectively improve the terminal reverse recovery failure, but will affect the concentration distribution in the channel region and the Vth parameter of the device.

[0004] The existing solution is to use contact hole injection annealing conditions with O2. During the annealing process, an oxide film shielding layer is formed on the sidewall of the BPSG to prevent the diffusion of B / P doped impurities. However, this will affect the contact hole morphology in the terminal area. Compared with the contact hole injection annealing conditions using an N2 gas atmosphere in the existing process, the reliability of the terminal device will be worse. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method to improve the influence of BPSG on contact resistance, thereby improving the reliability of the device without affecting performance.

[0006] To address the aforementioned issues, the present invention provides a method for improving the influence of BPSG on contact resistance by performing a rapid thermal annealing step before ion implantation of the contact hole to form an oxide film on the trench of the BPSG or the sidewall of the contact hole, followed by the contact hole ion implantation and annealing process.

[0007] Furthermore, the upper surface of the wafer is covered with a BPSG layer, and the contact holes or trenches penetrate the BPSG layer, with their bottoms located in the semiconductor substrate or epitaxial layer below the BPSG layer.

[0008] Furthermore, through a rapid thermal annealing process, a thin oxide film is formed on the surface of the BPSG layer and the sidewalls of the BPSG layer in the trench. The thickness of the oxide film is insufficient to affect the morphology of the contact holes or trenches in the terminal area.

[0009] Furthermore, the oxide film can prevent B / P impurity ions at the trench sidewalls of the BPSG from diffusing and affecting the contact resistance of the device during the annealing process after ion implantation.

[0010] Furthermore, the annealing following ion implantation is performed using an annealing process under an N2 atmosphere.

[0011] Furthermore, after the annealing, the oxide film layer is removed using a wet etching process.

[0012] Furthermore, the contact hole ion implantation forms a doped layer on the sidewalls and bottom of the contact hole or trench.

[0013] Furthermore, the contact hole or trench is located in a well in the semiconductor substrate, and the two sides of the contact hole or trench below the BPSG layer also have heavily doped layers.

[0014] The method for improving the effect of BPSG on contact resistance provided by this invention addresses the problem of impurity ion diffusion during annealing after ion implantation of the BPSG layer. Before annealing, a rapid thermal annealing is performed to form an oxide film as a barrier layer, encapsulating impurity ions within the BPSG layer. Then, the ion implantation and annealing processes are carried out, thus preventing impurity diffusion within the BPSG layer. After annealing, the oxide film layer is removed by wet etching. Attached Figure Description

[0015] Figure 1 This is a schematic cross-sectional view of contact hole ion implantation under existing BPSG.

[0016] Figures 2-4 This is a schematic diagram of the steps for improving contact hole ion implantation under BPSG according to the present invention.

[0017] Figure 5 This is a flowchart of the process steps of the present invention.

[0018] Explanation of reference numerals in the attached figures

[0019] 1 is the oxide film. Detailed Implementation

[0020] The following detailed description, in conjunction with the accompanying drawings, provides specific embodiments of the present invention and clearly and completely describes the technical solutions of the present invention. However, the present invention is not limited to the following embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated, and the same reference numerals denote the same elements throughout. In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] This invention relates to a method for improving the effect of BPSG on contact resistance, which involves performing a rapid thermal annealing step before ion implantation of the contact hole to form an oxide film on the trench or sidewall of the BPSG, followed by ion implantation and annealing of the contact hole.

[0023] like Figure 2 As shown, this invention is applicable to contact holes or similar trenches with BPSG layers that require ion implantation processes. Figure 2 The diagram shows a BPSG layer on the surface of a semiconductor substrate. Taking a trench as an example, the trench penetrates the BPSG layer and its bottom is located in the semiconductor substrate or epitaxy. In this embodiment, the trench sidewalls also have an N+ doped layer and a P-type well. The bottom of the trench is located in the P-type well, and the N+ doped layer is located below the BPSG layer. In conventional processes, when ion implantation and annealing are performed on such trenches, the high-temperature process causes B / P impurities in the BPSG layer to diffuse, thus affecting the impurity concentration distribution on the sidewalls. The conventional solution is to change the annealing process after ion implantation from a nitrogen atmosphere to an oxygen atmosphere. The addition of oxygen forms an oxide film on the sidewalls of the BPSG layer to prevent the diffusion of B / P impurities. However, the oxide film formed in this way affects the trench morphology.

[0024] After the contact hole or trench etching is completed and before ion implantation, a thin oxide film 1 is formed on the surface of the BPSG layer and the sidewalls of the BPSG layer in the trench through a rapid thermal annealing process, such as... Figure 3 As shown, the oxide film formed in this way is thin and not thick enough to affect the morphology of the contact holes or trenches in the terminal area.

[0025] After the oxide film forms, conventional ion implantation and annealing processes are then performed. For example... Figure 4As shown, ion implantation under an oxygen atmosphere was abandoned, and a nitrogen atmosphere was still used. After ion implantation, a normal annealing process was performed. Due to the presence of the oxide film, it can act as a barrier layer, preventing the diffusion of B / P impurities in the BPSG layer during annealing.

[0026] After annealing, the oxide film is no longer needed and can be removed using an etching process. This embodiment employs a wet etching process, such as HF acid etching, to remove the oxide film, thus exposing the BPSG layer again.

[0027] The process described in this invention adds a rapid thermal annealing step to form a thin oxide film on the surface of the BPSG layer that does not affect the trench morphology, serving as a barrier layer. This film can prevent the diffusion of B / P impurities in the BPSG layer during the subsequent ion implantation annealing process, keeping the impurity concentration on the trench sidewalls stable. This ensures the reliability of the terminal device while enabling normal reverse recovery testing at the application end.

[0028] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the effect of BPSG on contact resistance, characterized in that: Before ion implantation of contact holes or trenches on the wafer, a rapid thermal annealing step is performed to form an oxide film on the sidewalls of the contact holes or trenches in the BPSG layer, and then the ion implantation and annealing process of the contact holes or trenches is performed; the upper surface of the wafer is covered by the BPSG layer, the contact holes or trenches penetrate the BPSG layer, and the bottom is located in the semiconductor substrate or epitaxial layer below the BPSG layer.

2. The method for improving the effect of BPSG on contact resistance as described in claim 1, characterized in that: A thin oxide film is formed on the surface of the BPSG layer and the sidewalls of the BPSG layer in the contact holes or trenches by a rapid thermal annealing process. The thickness of the oxide film is insufficient to affect the morphology of the contact holes or trenches in the terminal area.

3. The method for improving the effect of BPSG on contact resistance as described in claim 2, characterized in that: The oxide film can prevent B / P impurity ions in the contact holes or trench sidewalls of the BPSG from diffusing and affecting the contact resistance of the device during the annealing process after ion implantation.

4. The method for improving the effect of BPSG on contact resistance as described in claim 1, characterized in that: The annealing following ion implantation is performed using an annealing process under an N2 atmosphere.

5. The method for improving the effect of BPSG on contact resistance as described in claim 1, characterized in that: After the annealing, the oxide film layer is removed by a wet etching process.

6. The method for improving the effect of BPSG on contact resistance as described in claim 1, characterized in that: The ion implantation of the contact hole or trench forms a doped layer on the sidewall and bottom of the contact hole or trench.

7. The method for improving the effect of BPSG on contact resistance as described in claim 1, characterized in that: The contact hole or trench is located in a well in the semiconductor substrate, and the two sides of the contact hole or trench below the BPSG layer also have heavily doped layers.

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