Photoetching line width control method

Abstract

The invention is applicable to the technical field of photoetching, and particularly relates to a photoetching line width control method, which comprises the following steps of: covering a mask layer on a substrate; the mask layer is covered with photoresist, and the photoresist is exposed and developed; growing a metal layer on the developed mask layer, and removing the residual photoresist; and etching is carried out, and after etching is completed, the mask layer and the metal layer are removed to obtain the etched substrate. According to the photoetching line width control method provided by the invention, resolution loss is reduced under simple conditions, parameter adjustment is carried out according to used equipment, reasonable distribution and layout are carried out before the process, the method is simple, a wide photoresist selection range, metal growth types and conditions and selection of etching equipment are provided, and the production efficiency is improved. The scheme is formulated according to actual purposes and requirements, and high practicability and applicability are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of photolithography, and in particular relates to a photolithography line width control method. Background Art

[0002] Transferring the lithographic structure by etching after lithography is an important process in the semiconductor device manufacturing process. It has been studied in many academic studies and process improvements. Since the photoresist needs to be cured before etching, and the etching process is mostly high-temperature etching, the photoresist is likely to be greatly deformed, that is, the actual line width after etching is greater than the lithographic line width, or the side wall shrinks due to heat during the etching process and becomes an arc. The post-etching morphology and line width mentioned here include the morphology after etching of passivation layers such as silicon oxide and silicon nitride, and can also be the morphology after etching of other metal layers, GaAs and other material layers.

[0003] As the requirements for line width are getting smaller and smaller and the semiconductor structure is getting finer and finer, the morphology and line width after etching have a great impact on these requirements. The change of line width after heating and the uneven change of line width after heating have greatly affected the final effect of the device. However, in the actual process, etching after photolithography is a common step. The general solution includes reducing the hardening time, replacing the photoresist, low-temperature etching, etc., but the deformation of the photoresist can only be reduced but not eliminated, and low-temperature etching is not suitable for all etching systems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling the line width of a photolithography, aiming to solve the problem raised in the third part of the background technology.

[0005] The present invention is implemented as follows: a photolithography line width control method, the photolithography line width control method comprising:

[0006] covering the substrate with a mask layer;

[0007] Covering the mask layer with a photoresist, and exposing and developing the photoresist;

[0008] growing a metal layer on the developed mask layer and removing the remaining photoresist;

[0009] Etching is performed, and after the etching is completed, the mask layer and the metal layer are removed to obtain an etched substrate.

[0010] Preferably, the mask layer is silicon oxide.

[0011] Preferably, in the step of growing the metal layer on the developed mask layer, ion beam sputtering, electron beam evaporation or ALD deposition is adopted.

[0012] Preferably, the metal layer is Al, Ti, Au or Pt.

[0013] Preferably, in the step of removing the mask layer and the metal layer, BOE, HF or HCl is used as the mask removal solvent.

[0014] Preferably, after the steps of exposing and developing the photoresist, no hardening treatment is performed, and the metal layer is directly grown on the mask layer.

[0015] Preferably, the photoresist is a positive photoresist, a reverse photoresist or a reverse photoresist.

[0016] The present invention provides a lithography line width control method, which reduces resolution loss under simple conditions, adjusts parameters according to the equipment used, and reasonably allocates and arranges the layout before the process. The method is simple, provides a wide range of photoresist selection, metal growth types and conditions, and etching equipment selection, and formulates a plan according to actual use and needs, with high practicality and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a photolithography line width control method provided by an embodiment of the present invention;

[0018] Figure 2 A schematic diagram of the results of a photolithography line width control method provided by an embodiment of the present invention;

[0019] Figure 3 A schematic diagram of etching results with a line width of 1.5 microns provided in an embodiment of the present invention;

[0020] Figure 4 A schematic diagram of an etching result with a line width of 2 microns provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] Exposure and development: A micro-nano processing technology that mainly involves ultraviolet lithography, which is to apply photoresist on the surface of the substrate sample, and then irradiate ultraviolet light through the mask to the substrate surface, use photochemical reactions to change the properties of the photoresist exposed to light, and then dissolve the area that reacts with light into a specific solution to achieve the purpose of making a specific pattern on the substrate.

[0023] Lift-off technology refers to the process in which, after the substrate is coated with photoresist, exposed and developed, a photoresist with a certain pattern is used as a mask to deposit the required materials, such as metals, through evaporation and other methods. Then, while removing the photoresist, the non-required materials on the photoresist film are stripped off, leaving only the material structure with the original pattern on the substrate.

[0024] Etching: It is an etching process that transfers the photoresist pattern obtained by lithography to the thin film on the surface of the wafer. That is, the covering and protective effect of the photoresist film is used to remove the thin film without photoresist protection by chemical reaction or physical action to complete the purpose of pattern transfer.

[0025] like Figure 1 and Figure 2 As shown, a lithography line width control method provided by an embodiment of the present invention, the lithography line width control method includes:

[0026] covering the substrate with a mask layer;

[0027] Covering the mask layer with a photoresist, and exposing and developing the photoresist;

[0028] growing a metal layer on the developed mask layer and removing the remaining photoresist;

[0029] Etching is performed, and after the etching is completed, the mask layer and the metal layer are removed to obtain an etched substrate.

[0030] In this embodiment, the specific steps include:

[0031] 1. First grow a mask layer on a clean substrate. This layer can be a required or easily removable mask layer according to process requirements.

[0032] 2. Prepare photoresist by spin coating, spray coating or other methods on the substrate behind the growth mask layer. The thickness of the photoresist needs to be much larger than the thickness of the metal to be grown. It is recommended to use positive thick photoresist and bake it.

[0033] 3. Expose the prepared photoresist, develop it after exposure, and blow dry it with nitrogen without performing heating treatment such as baking.

[0034] 4. Grow metal on the substrate prepared in step 2 at room temperature, and then peel and remove the glue after growth.

[0035] 5. Etch the substrate prepared in step 3 to achieve patterned transfer.

[0036] 6. Optionally, the mask is removed after the patterned transfer, and the metal on the mask surface is removed at the same time.

[0037] Example 1: Precision Etching with 1.5 μm Line Width

[0038] like Figure 3 As shown:

[0039] 1. First grow a mask layer on a clean substrate, where the required silicon oxide is selected as the mask layer as required.

[0040] 2. Spin-coat photoresist on the substrate behind the growth mask layer. Use positive thick photoresist Az12XT to prepare a thickness of 8 microns and bake before photolithography.

[0041] 3. Expose the prepared photoresist, perform post-baking and development after exposure, and blow dry with nitrogen after development without performing any heating treatment such as baking.

[0042] 4. Grow 500nm Ti metal on the substrate prepared in step 2 at room temperature, and perform stripping and degumming after growth.

[0043] 5. Etch the substrate prepared in step 3 to achieve patterned transfer.

[0044] 6. Optionally, the mask is removed after the patterned transfer. Al metal and silicon oxide are selected here, so wet mask removal cannot be used. Carbon tetrafluoride is used to remove the mask and remove the metal on the mask surface at the same time.

[0045] like Figure 4 As shown:

[0046] Example 1: Etching with a line width of 2 microns

[0047] 1. First grow a mask layer on a clean substrate, where the required silicon oxide is selected as the mask layer as required.

[0048] 2. Spin-coat photoresist on the substrate behind the growth mask layer. Use positive thick photoresist Az12XT to prepare a thickness of 8 microns and bake before photolithography.

[0049] 3. Expose the prepared photoresist, perform post-baking and development after exposure, and blow dry with nitrogen after development without performing any heating treatment such as baking.

[0050] 4. Grow 500nm Ti metal on the substrate prepared in step 2 at room temperature, and perform stripping and degumming after growth.

[0051] 5. Etch the substrate prepared in step 3 to achieve patterned transfer.

[0052] 6. Optionally, the mask is removed after the patterned transfer. Al metal and silicon oxide are selected here, so wet mask removal cannot be used. Carbon tetrafluoride is used to remove the mask and the metal on the surface of the mask is removed at the same time. Subsequently, a 500nm circular electrode is grown on the surface again as needed.

[0053] In the embodiment of the present invention, the principle that different surface materials do not participate in the etching reaction is utilized to prepare the desired morphology through photolithography, and then the morphology is inherited through metal growth, and finally etching is performed. The specific steps are as follows:

[0054] First, it is best to grow a silicon-based mask layer on the surface of the substrate, but it is not limited to silicon-based. A suitable mask layer can be selected as needed. The photolithography process prepares a photoresist pattern with a certain thickness as needed to ensure that there is no peeling problem. The photoresist used includes positive photoresist, negative photoresist and reverse photoresist according to the final morphology requirements. It is best to use a photoresist that can prepare a vertical structure. After the photolithography patterning is completed, no hardening is performed, and metal growth is performed immediately. Room temperature is maintained during the metal growth process. The etching step continuously completes the mask opening and substrate etching, and the surface mask is wet removed after etching.

[0055] The finished product is covered with a passivation layer, which is selected from silicon oxide (SiOx), silicon nitride (SiNx), aluminum oxide or silicon oxynitride (SiON); the photoresist types include positive photoresists, negative photoresists, reverse photoresists and other UV photoresists. The metal growth method includes ion beam sputtering, electron beam evaporation, ALD deposition, and the metal growth types include Al, Ti, Au, Pt and the like; continuous etching can optionally include etching with the same equipment and using different equipment to complete multi-step etching; the wet etching solution includes BOE, HF, HCl and other commonly used mask removal solvents.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling a photolithography line width, characterized in that: The photolithography line width control method comprises: covering the substrate with a mask layer; Covering the mask layer with a photoresist, and exposing and developing the photoresist; growing a metal layer on the developed mask layer and removing the remaining photoresist; Etching is performed, and after the etching is completed, the mask layer and the metal layer are removed to obtain an etched substrate.

2. The photolithography line width control method according to claim 1, characterized in that: The mask layer is silicon oxide.

3. The photolithography line width control method according to claim 1, characterized in that: In the step of growing a metal layer on the developed mask layer, ion beam sputtering, electron beam evaporation or ALD deposition is adopted.

4. The photolithography line width control method according to claim 1, characterized in that: The metal layer is Al, Ti, Au or Pt.

5. The photolithography line width control method according to claim 1, characterized in that: In the step of removing the mask layer and the metal layer, BOE, HF or HCl is used as the mask removal solvent.

6. The photolithography line width control method according to claim 1, characterized in that: After the steps of exposing and developing the photoresist, a metal layer is directly grown on the mask layer without performing a hardening treatment.

7. The photolithography line width control method according to claim 1, characterized in that: The photoresist is a positive photoresist, a reverse photoresist or a reverse photoresist.

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