Method for removing photoresist on surface of metal film

Abstract

The invention discloses a method for removing photoresist on the surface of a metal film. The method comprises the following steps: providing a semiconductor substrate; depositing a metal film on the substrate containing the etching stop layer at low temperature; photoresist is spin-coated to form a photoresist mask layer, and photoetching is carried out on the photoresist mask layer to form a metal patterned window; and etching the metal thin film through the metal graphical window, removing the photoresist by using an ashing photoresist removal process, and cleaning to obtain the graphical metal thin film. According to the invention, by changing the deposition temperature of the metal film to influence the crystal grains and the crystal boundary form after film formation, the characteristics of the contact surface of the metal film surface and the photoresist (the contact area between the metal surface with smaller crystal grains and the photoresist is larger) are further changed, so that the adhesion is better, the heat dissipation efficiency of the surface of the photoresist in the process is higher, and the heat dissipation efficiency of the surface of the photoresist is improved. The problem of residues caused by high-temperature carbonization in the ashing and degumming process of the surface of the metal film is solved; and the patterned metal film is subjected to post-treatment through annealing, so that the performance loss of the product is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a method for removing photoresist from the surface of a metal film. Background Art

[0002] Aluminum / aluminum copper (0-0.5% wt Cu) is the most commonly used metal material in metal etching in semiconductor manufacturing. The aluminum / aluminum copper film formed by thin film deposition technology exhibits irregular grains. There are differences in the physical and chemical properties at the grain boundary and inside the grain. Different deposition temperatures will change the grain and grain boundary morphology after film formation, including but not limited to grain size, grain spacing, roughness, etc. These differences will change the surface properties of the metal film.

[0003] During the ashing and degumming process after the aluminum / aluminum-copper (Al / AlCu) patterning process, the residual photoresist on the metal surface may not be completely removed. To solve the problem of degumming residue after metal etching, it is usually solved by reducing the photoresist thickness or using UV curing and other pre-etching pretreatment methods; due to the limited penetration ability of plasma, the efficiency of ashing and degumming will decrease with the increase of photoresist thickness. For thicker photoresists, more reaction time is required. If the thermal conductivity is not high, the photoresist surface will overheat as the degumming time increases, while the internal part still fails to fully react and produces photoresist carbonization residue. It is usually difficult to eliminate the abnormal residue by increasing the degumming over-etching amount. Summary of the invention

[0004] The present application affects the grain and grain boundary morphology after film formation by changing the deposition temperature of the metal film, thereby changing the characteristics of the contact surface between the metal film surface and the photoresist (the metal surface with smaller grains has a larger contact area with the photoresist), thereby improving the adhesion and making the heat dissipation efficiency of the photoresist surface higher in the process, solving the problem of residues due to high-temperature carbonization during the ashing and degumming process of the metal film surface; and post-processing the patterned metal film by annealing without causing loss of product performance.

[0005] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0006] To achieve one, part or all of the above purposes or other purposes, the present invention provides a method for removing photoresist from the surface of a metal film.

[0007] A method for removing photoresist from the surface of a metal film, comprising:

[0008] Providing a semiconductor substrate, wherein the substrate is deposited with an etch stop layer;

[0009] Low temperature deposition of a metal film on a substrate including an etch stop layer, the deposition temperature being 20+ / -3°C;

[0010] Spin-coating photoresist to form a photoresist mask layer, performing photolithography on the photoresist mask layer to form a metal patterned window, wherein the metal film is exposed to the metal patterned window;

[0011] The metal film is etched through the metal patterned window, and the photoresist is removed by an ashing stripping process, and a patterned metal film is obtained after cleaning.

[0012] The patterned metal film is treated by an annealing process, wherein the temperature of the annealing process is 370±50° C. and the time is between 60 and 180 minutes.

[0013] The annealing process is furnace tube alloying.

[0014] The metal film is deposited by physical / chemical vapor deposition or electroplating process.

[0015] The thickness of the photoresist mask layer is greater than or equal to 4 μm.

[0016] Multiple layers of metal films can be deposited, and the patterned multiple layers of metal films only need to undergo one annealing process.

[0017] The photoresist mask layer is exposed and developed through a mask plate to form a metal circuit pattern required for metal patterning;

[0018] The exposure treatment uses an exposure light source with a wavelength of 365nm for exposure for 360 to 540s;

[0019] The exposed wafer is placed in a developer for development for 30 to 90 seconds.

[0020] The metal film is etched according to the metal circuit pattern using wet etching or dry etching technology to remove unnecessary metal film.

[0021] The etching gas used in the ashing and degumming process is a mixed gas of oxygen and argon;

[0022] The mixed gas is excited by a radio frequency power supply in a plasma reaction chamber to generate plasma;

[0023] The active oxygen molecules in the plasma react with the photoresist, oxidizing it and decomposing it into volatile substances, thereby achieving the removal of the photoresist.

[0024] The oxygen flow rate in the plasma reaction chamber is 1000-5000 sccm, the argon flow rate is 0-1000 sccm, the RF power supply power is 700-900 W, the pressure is 0.7-1.1 T, the temperature is 250+ / -5° C., and the time is 120-300 s.

[0025] Compared with the prior art, the beneficial effects of the present invention mainly include:

[0026] The present application affects the grain and grain boundary morphology after film formation by changing the deposition temperature of the metal film, thereby changing the characteristics of the contact surface between the metal film surface and the photoresist (the metal surface with smaller grains has a larger contact area with the photoresist), thereby improving the adhesion and making the heat dissipation efficiency of the photoresist surface higher in the process, solving the problem of residues due to high-temperature carbonization during the ashing and degumming process of the metal film surface; and post-processing the patterned metal film by annealing without causing loss of product performance.

[0027] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 Schematic diagram comparing the grain and grain boundary morphology of metal films at different temperatures provided in the embodiments of the present application.

[0030] Figure 2 A schematic flow chart of a method for removing photoresist from the surface of a metal film provided in an embodiment of the present application.

[0031] Figure 3 A comparison chart of the photoresist adhesion provided in the embodiments of the present application.

[0032] Figure 4 This is a grain size comparison chart provided in the embodiments of the present application. DETAILED DESCRIPTION

[0033] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0034] The present application affects the grain and grain boundary morphology after film formation by changing the deposition temperature of the metal film, thereby changing the characteristics of the contact surface between the metal film surface and the photoresist (the metal surface with smaller grains has a larger contact area with the photoresist), thereby improving the adhesion and making the heat dissipation efficiency of the photoresist surface higher in the process, solving the problem of residues due to high-temperature carbonization during the ashing and degumming process of the metal film surface; and post-processing the patterned metal film by annealing without causing loss of product performance.

[0035] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0036] Example

[0037] Figure 2 Shown is a schematic flow chart of a method for removing photoresist from the surface of a metal film provided in an embodiment of the present application.

[0038] like Figure 2 As shown, a method for removing photoresist from the surface of a metal film comprises:

[0039] Providing a semiconductor substrate 1, on which an etch stop layer 11 is deposited;

[0040] Step a: depositing a metal film 3 at a low temperature on a substrate 1 including an etch stop layer 11, wherein the deposition temperature is 20+ / -3°C;

[0041] Step b: spin-coating a photoresist to form a photoresist mask layer 4, performing photolithography on the photoresist mask layer 4 to form a metal patterned window, and exposing the metal film 3 to the metal patterned window;

[0042] Step c: etching the metal film 3 through the metal patterning window;

[0043] Step d: Use an ashing process to remove the photoresist, and obtain a patterned metal film after cleaning.

[0044] Figure 1 Shown is a schematic diagram comparing the grain and grain boundary morphology of a metal film at different temperatures provided in an embodiment of the present application.

[0045] like Figure 1 As shown, Figure 1 1-A represents the grain and grain boundary morphology of the metal film under high temperature deposition conditions. Figure 11-B represents the grain and grain boundary morphology of the metal film under low temperature deposition conditions. Different deposition temperatures will change the grain and grain boundary morphology after film formation, including but not limited to grain size, grain spacing, roughness, etc. These differences will change the surface properties of the metal film.

[0046] The present application changes the surface properties of the metal film 3 by changing the temperature of metal film deposition, thereby changing the adhesion and thermal conductivity of the contact surface between the metal film 3 and the photoresist mask layer 4.

[0047] Figure 3 Shown is a comparison diagram of photoresist adhesion provided in an embodiment of the present application.

[0048] like Figure 3 As shown, Figure 3 Figure 3-A is the result of the hundred-grid knife test of the adhesion between AlCu and photoresist at 270°C (poor adhesion → poor thermal conductivity); Figure 3 3-B is the result of the cross-cutting test of the adhesion between AlCu and photoresist at a temperature of 20°C (good adhesion → good thermal conductivity); the present application changes the adhesion between AlCu and photoresist by changing the temperature of metal film deposition, thereby changing the adhesion between the contact surface of the metal film 3 and the photoresist mask layer 4.

[0049] Figure 4 Shown is a grain size comparison diagram provided in an embodiment of the present application.

[0050] like Figure 4 As shown, Figure 4 4-A is the AlCu surface morphology (small grains) deposited at 20°C; Figure 4 4-B is the AlCu surface morphology (large grains) deposited at 270°C; the present application changes the surface morphology (grain size) of the AlCu metal film grains by changing the temperature of metal film deposition, thereby changing the surface properties of the metal film.

[0051] The method of changing the deposition temperature of the metal film in this application has little impact and restriction on the subsequent photolithography / etching, and because the low-temperature deposition of the metal film can significantly improve the degumming effect, this application uses a furnace tube alloy annealing method with a temperature of 370±50°C and a time of 60 to 180 minutes as an annealing process to post-process the metal film after patterning, and will not cause any loss of product performance.

[0052] The metal film deposition of the present application adopts physical / chemical vapor deposition or electroplating process, the thickness of the photoresist mask layer is greater than or equal to 4μm, and the thickness ratio of the photoresist mask layer to the metal film is 1 to 10:1.

[0053] As a preferred embodiment of the present invention, other processes can be inserted between the furnace tube alloying and other process steps in this embodiment.

[0054] As a preferred embodiment of the present invention, in this embodiment, multiple layers of metal films can be deposited, and the patterned multiple layers of metal films only need to undergo one annealing process; and if there are no requirements for the metal crystal phase and grain size (such as optimizing electromigration issues), annealing treatment may not be performed.

[0055] The specific process of photolithography in this application includes:

[0056] The photoresist mask layer is exposed and developed through a mask plate to form a metal circuit pattern required for metal patterning; the exposure process uses an exposure light source with a wavelength of 365nm for exposure for 360 to 540 seconds; the exposed wafer is placed in a developer for development for 30 to 90 seconds.

[0057] The present application etches the metal film according to the metal circuit pattern through wet etching or dry etching technology to remove unnecessary metal film.

[0058] The etching gas used in the ashing stripping process is a mixture of oxygen and argon. The mixed gas is excited by a radio frequency power supply in a plasma reaction chamber to generate plasma. The active oxygen molecules in the plasma react with the photoresist, oxidizing it and decomposing it into volatile substances, thereby removing the photoresist.

[0059] As a preferred embodiment of the present invention, in this embodiment, the oxygen flow rate in the plasma reaction chamber is 1000-5000sccm, the argon flow rate is 0-1000sccm, the RF power supply power is 700-900W, the pressure is 0.7-1.1T, the temperature is 250+ / -5°C, and the time is 120-300s.

[0060] The present application affects the grain and grain boundary morphology after film formation by changing the deposition temperature of the metal film, thereby changing the characteristics of the contact surface between the metal film surface and the photoresist (the metal surface with smaller grains has a larger contact area with the photoresist), thereby improving the adhesion and making the heat dissipation efficiency of the photoresist surface higher in the process, solving the problem of residues due to high-temperature carbonization during the ashing and degumming process of the metal film surface; and post-processing the patterned metal film by annealing without causing loss of product performance.

[0061] In order to facilitate the description, some common English nouns or letters used in the present invention are only used for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0062] It should also be noted that, in this document, relational terms such as "first" and "second" are merely 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.

Claims

1. A method for removing photoresist from the surface of a metal film, characterized in that: include: Providing a semiconductor substrate, wherein the substrate is deposited with an etch stop layer; Low temperature deposition of a metal film on a substrate including an etch stop layer, the deposition temperature being 20+ / -3°C; Spin-coating a photoresist to form a photoresist mask layer, performing photolithography on the photoresist mask layer to form a metal patterned window, wherein the metal film is exposed to the metal patterned window; The metal film is etched through the metal patterned window, and the photoresist is removed by an ashing stripping process, and a patterned metal film is obtained after cleaning.

2. A method for removing photoresist from the surface of a metal film according to claim 1, characterized in that: The patterned metal film is treated by an annealing process, wherein the temperature of the annealing process is 370±50° C. and the time is between 60 and 180 minutes.

3. A method for removing photoresist from the surface of a metal film according to claim 2, characterized in that: The annealing process is furnace tube alloying.

4. A method for removing photoresist from the surface of a metal film according to claim 3, characterized in that: The metal film is deposited by physical / chemical vapor deposition or electroplating process.

5. A method for removing photoresist from the surface of a metal film according to claim 4, characterized in that: The thickness of the photoresist mask layer is greater than or equal to 4 μm.

6. A method for removing photoresist from the surface of a metal film according to claim 4, characterized in that: Multiple layers of metal films can be deposited, and the patterned multiple layers of metal films only need to undergo one annealing process.

7. A method for removing photoresist from the surface of a metal film according to claim 1, characterized in that: The photoresist mask layer is exposed and developed through a mask plate to form a metal circuit pattern required for metal patterning; The exposure treatment uses an exposure light source with a wavelength of 365nm for exposure for 360 to 540s; The exposed wafer is placed in a developer for development for 30 to 90 seconds.

8. A method for removing photoresist from the surface of a metal film according to claim 7, characterized in that: The metal film is etched according to the metal circuit pattern using wet etching or dry etching technology to remove unnecessary metal film.

9. The method for removing photoresist from the surface of a metal film according to claim 1, characterized in that: The etching gas used in the ashing and degumming process is a mixed gas of oxygen and argon; The mixed gas is excited by a radio frequency power supply in a plasma reaction chamber to generate plasma; The active oxygen molecules in the plasma react with the photoresist, oxidizing it and decomposing it into volatile substances, thereby achieving the removal of the photoresist.

10. A method for removing photoresist from the surface of a metal film according to claim 9, characterized in that: The oxygen flow rate in the plasma reaction chamber is 1000-5000 sccm, the argon flow rate is 0-1000 sccm, the RF power supply power is 700-900 W, the pressure is 0.7-1.1 T, the temperature is 250+ / -5° C., and the time is 120-300 s.

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