Manufacturing method of U-shaped gate groove for reducing electric field concentration effect

Abstract

The invention provides a manufacturing method of a U-shaped gate groove for reducing an electric field concentration effect, and the method comprises the steps: transferring a pattern to an epitaxial layer on the surface of a silicon carbide epitaxial layer through a mask; performing ion implantation on the epitaxial layer by an ion implanter according to set parameters to form a U-shaped implantation region; carrying out corrosion by adopting a wet-process liquid medicine to obtain a U-shaped gate groove; the wet-process liquid medicine comprises 50 parts by mass of nitric acid, 20 parts by mass of water, 2 parts by mass of acetic acid and 1 part by mass of hydrofluoric acid, the etching efficiency is improved, and smooth corners of the grid groove are guaranteed.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a U-shaped gate groove for reducing electric field concentration effect. Background Art

[0002] Silicon carbide (SiC) materials have excellent electrical properties, including wide bandgap, high breakdown electric field, high saturation drift velocity and high thermal conductivity. These properties enable SiC devices to operate under special conditions of high temperature, high power and high frequency. At present, SiC MOSFET devices have become an ideal substitute for silicon-based bipolar power devices. Among them, trench SiC MOSFET has received extensive attention and research due to its low characteristic on-resistance. The electric field concentration effect at the bottom corner of the gate trench in its structure will lead to reduced stability of the gate oxide layer or even breakdown. The existing technology uses dry etching, which takes about 10 minutes to etch a depth of 1μm. The dry etching does not produce smooth morphology at the corners, which makes the electric field concentration phenomenon more serious. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for manufacturing a U-shaped gate groove which reduces the electric field concentration effect, improves the etching efficiency, and ensures that the corners of the gate groove are smooth.

[0004] The present invention is implemented as follows: a method for manufacturing a U-shaped gate groove for reducing electric field concentration effect, comprising the following steps:

[0005] Step 1: On the surface of the silicon carbide epitaxial layer, a pattern is transferred to the epitaxial layer using a mask;

[0006] Step 2, implanting ions into the epitaxial layer using an ion implanter according to set parameters to form a U-shaped implantation region;

[0007] Step 3, using a wet chemical solution for etching to obtain a U-shaped gate groove; the wet chemical solution includes 50 parts by mass of nitric acid, 20 parts by mass of water, 2 parts by mass of acetic acid and 1 part by mass of hydrofluoric acid.

[0008] Furthermore, the ions implanted are nitrogen ions or phosphorus ions.

[0009] Further, the step 2 is specifically as follows: according to the required U-shaped gate groove, the implantation energy is set, and the implantation concentration threshold is set. The ion implanter implants ions into the epitaxial layer according to the set implantation energy and the implantation concentration threshold to form a U-shaped implantation area. The implantation concentration threshold is 1E20-5E20cm -3 .

[0010] The advantages of the present invention are as follows: a method for manufacturing a U-shaped gate groove for reducing the electric field concentration effect of the present invention ensures the lateral size of the U-shaped gate groove and ensures that the bottom of the gate groove has a smooth corner, thereby reducing the electric field concentration effect at the corner and improving the reliability and stability of the gate oxide layer; and through the method of the present invention, etching at a depth of 1 micron only takes about 6 minutes, greatly improving the etching efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0012] Figure 1 The present invention is a flow chart of a method for manufacturing a U-shaped gate groove for reducing electric field concentration effect.

[0013] Figure 2 It is a structural diagram of embodiment 1 of the present invention. DETAILED DESCRIPTION

[0014] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0016] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "in contact with ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, doping type or part discussed below can be represented as a second element, component, region, layer or part.

[0017] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of one element or feature described in the figures to other elements or features. It should be understood that, in addition to the orientations described in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0018] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, in this specification, the term "and / or" includes any and all combinations of the relevant listed items.

[0019] like Figure 1 As shown, the embodiment of the present application provides a method for manufacturing a U-shaped gate groove for reducing the electric field concentration effect, comprising the following steps:

[0020] Step 1: On the surface of the silicon carbide epitaxial layer, a pattern is transferred to the epitaxial layer using a mask;

[0021] Step 2: According to the required U-shaped gate groove, the injection energy and the injection concentration threshold are set. The ion implanter implants ions into the epitaxial layer according to the set injection energy and injection concentration threshold to form a U-shaped injection area. The injection concentration threshold is 1E20-5E20cm -3 , the ions implanted are nitrogen ions or phosphorus ions;

[0022] Step 3, using a wet chemical solution for etching to obtain a U-shaped gate groove; the wet chemical solution includes 50 parts by mass of nitric acid, 20 parts by mass of water, 2 parts by mass of acetic acid and 1 part by mass of hydrofluoric acid.

[0023] Embodiment 1

[0024] like Figure 2As shown, the U-shaped gate groove includes an N+ type silicon carbide substrate layer 201, an N-type silicon carbide epitaxial layer 202, and a U-shaped gate groove 203 formed by ion implantation on the N-type silicon carbide epitaxial layer 202 and then wet etching.

[0025] A mask, which may be silicon oxide or metal, is deposited on the N-type silicon carbide epitaxial layer 202. The same pattern on the mask is copied to the N-type silicon carbide epitaxial layer 202 by using a photolithography process. The mask material above the implantation area is removed. High-energy, high-dose ion implantation is performed according to the designed depth of the U-shaped gate groove. The bombardment of silicon carbide by high-energy impurity ions will damage the crystal structure. When high-energy ions enter the crystal and collide with the atoms of the N-type silicon carbide epitaxial layer 202, energy is transferred and some atoms on the lattice are replaced, causing the silicon carbide lattice structure to change. At this time, it can be corroded by a wet chemical solution. The wet solution is not corrosive to the area not injected, avoiding the disadvantage of lateral drilling by wet etching, ensuring the lateral size of the U-shaped gate groove and ensuring that the bottom of the gate groove has a smooth corner, thereby reducing the electric field concentration effect at the corner and improving the reliability and stability of the gate oxide layer; the wet solution includes 50 parts by mass of nitric acid, 20 parts by mass of water, 2 parts by mass of acetic acid and 1 part by mass of hydrofluoric acid; at this time, it only takes about 6 minutes to etch a depth of 1μm, while if dry etching is used, it takes about 10 minutes, which reduces the time by nearly 40%, greatly improving the etching efficiency.

[0026] The injection concentration is 1E20~5E20cm -3 , within this implantation concentration, the implanted area can be corroded by the wet chemical solution; the distribution of ion implantation by the ion implanter is Gaussian, and the implantation morphology is U-shaped; the actual concentration distribution of ion implantation is expressed by a Gaussian function:

[0027]

[0028] Among them, R P is the average projection range, △R P is the standard deviation, Q T is the total number of ions implanted per unit area.

[0029] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a U-shaped gate groove for reducing electric field concentration effect, characterized in that: The steps include: Step 1: On the surface of the silicon carbide epitaxial layer, a pattern is transferred to the epitaxial layer using a mask; Step 2, implanting ions into the epitaxial layer using an ion implanter according to set parameters to form a U-shaped implantation region; Step 3, using a wet chemical solution for etching to obtain a U-shaped gate groove; the wet chemical solution includes 50 parts by mass of nitric acid, 20 parts by mass of water, 2 parts by mass of acetic acid and 1 part by mass of hydrofluoric acid.

2. The method for manufacturing a U-shaped gate groove for reducing electric field concentration effect according to claim 1, characterized in that: The ions implanted are nitrogen ions or phosphorus ions.

3. The method for manufacturing a U-shaped gate groove for reducing electric field concentration effect according to claim 1, characterized in that: The step 2 specifically includes: setting the implantation energy and the implantation concentration threshold according to the required U-shaped gate groove, and the ion implanter implants ions into the epitaxial layer according to the set implantation energy and the implantation concentration threshold to form a U-shaped implantation area, wherein the implantation concentration threshold is 1E20-5E20cm -3 .

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