Photoresist removing method

Abstract

The invention discloses a photoresist removing method. The method comprises the following steps: providing a processing object with a metal layer on the surface; forming an opening pattern penetrating through the metal layer through photoetching and etching; using a first treatment method to perform first removal treatment on the photoresist on the metal layer for the first time after etching under the condition that etching and oxidation effects are not generated on the metal layer; using a second treatment method to carry out second removal treatment on photoresist residues existing on the treatment object for a second time under the condition that the metal layer is not oxidized; a third treatment method is used, and particles existing on the treatment object are subjected to third removal treatment for a third time under the condition that etching and oxidation effects are not generated on the metal layer; the first time and the third time are longer than the second time. According to the invention, effective photoresist removal can be realized without causing treatment residues.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuit processes, and particularly to a method for removing photoresist. Background Art

[0002] In the packaging stage after the production of the back-end aluminum wire layer of power device products, usually three layers of metals, namely titanium, nickel vanadium and silver, are further laid. Then, a photoresist is coated on the silver layer for lithography, and a wet etching method is adopted to etch the above three layers of metals by using the photoresist pattern to form an opening pattern in the three layers of metals for subsequent packaging and probing tests. After the opening pattern is formed, how to effectively remove the photoresist and avoid photoresist residue has become an urgent problem to be solved in the industry. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for removing photoresist.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] The present invention provides a method for removing photoresist, including:

[0006] Providing a processing object with a metal layer on its surface;

[0007] Forming an opening pattern penetrating the metal layer through lithography and etching;

[0008] Using a first processing method to perform a first removal process on the photoresist located on the metal layer after etching for a first time without etching and oxidizing the metal layer;

[0009] Using a second processing method to perform a second removal process on the photoresist residue existing on the processing object for a second time without oxidizing the metal layer;

[0010] Using a third processing method to perform a third removal process on the particles existing on the processing object for a third time without etching and oxidizing the metal layer;

[0011] The first time and the third time are greater than the second time.

[0012] Further, the first processing method includes a wet photoresist removal process method, the second processing method includes a dry photoresist removal process method, and the third processing method includes a cleaning process method.

[0013] Further, the wet photoresist removal process method includes a wet photoresist removal process using propylene glycol monomethyl ether acetate.

[0014] Further, the first time is greater than the theoretical time required for over-etching the photoresist with propylene glycol methyl ether acetate.

[0015] Further, a tank wet stripping machine with 1 cleaning tank is used to soak the object to be processed in propylene glycol methyl ether acetate in the cleaning tank for the first removal treatment; alternatively, a tank wet stripping machine with 2 cleaning tanks is used to soak the object to be processed in propylene glycol methyl ether acetate in 2 cleaning tanks in sequence for 1 pass of the first removal treatment each, and the sum of the treatment times of the 2 passes is equal to the first time.

[0016] Further, the dry stripping process method includes a dry ashing stripping process method using a process gas without oxygen.

[0017] Further, the process gas includes hydrogen and nitrogen.

[0018] Further, the concentration of the hydrogen is 2% to 3%, and the flow rate is 100 sccm / s to 200 sccm / s.

[0019] Further, the cleaning process method includes ultrasonic atomization cleaning with deionized water or aerated bubbling cleaning with deionized water.

[0020] Further, the metal layer includes a titanium layer, a nickel vanadium layer, and a silver layer sequentially stacked on the surface of the object to be processed. During lithography, the photoresist covers the surface of the silver layer.

[0021] It can be seen from the above technical solutions that the present invention replaces the existing single stripping process with a three-step combined stripping treatment method including a wet stripping process, a dry stripping process, and a cleaning process. First, the wet stripping process (using propylene glycol methyl ether acetate) is used to effectively remove the photoresist, then the dry stripping process (using hydrogen and nitrogen) is used to remove the photoresist residues after the wet stripping, and finally the cleaning process is used to remove the particles generated by the dry stripping process, so as to achieve complete stripping without etching and oxidizing the metal layer and without causing treatment residue problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flowchart of a method for stripping a photoresist according to a preferred embodiment of the present invention.

[0023] Figures 2 - 5 It is a schematic diagram of process steps when stripping is performed according to a method of Figure 1 according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The words such as "including" used herein are intended to mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0025] The following further elaborates on the specific implementation manners of the present invention with reference to the accompanying drawings.

[0026] Reference Figure 1 A method for removing photoresist of the present invention includes the following steps:

[0027] Step S1: Provide a processing object with a metal layer on its surface.

[0028] One or more metal layers may be provided on the surface of the processing object. Hereinafter, a case where multiple metal layers are provided on the surface of the processing object will be described in detail.

[0029] As Figure 2 shown, the processing object may be a wafer product with multiple metal layers stacked on its surface. For example, it is a wafer of a power device product in the packaging stage. At this stage, the power device product has completed the production of the back-end aluminum wire layer, and three metal layers, such as a titanium layer 15, a nickel-vanadium layer 12, and a silver layer 14, are continuously laid on the etch stop layer 11 located on the aluminum wire layer.

[0030] Step S2: Form an opening pattern penetrating the metal layer through photolithography and etching.

[0031] As Figure 2 shown, then, through photolithography and etching processes, an opening pattern needs to be formed on the three metal layers of the titanium layer 15, the nickel-vanadium layer 12, and the silver layer 14 for subsequent packaging and probing tests. Therefore, first, a photoresist needs to be covered on the silver layer 14 and photolithography is performed to form a photoresist pattern 13 for the etching of the opening pattern on the silver layer 14.

[0032] As Figure 3 shown, then, a wet etching process is adopted, and using the photoresist pattern 13, the above three metal layers are etched to form an opening pattern 16 penetrating the three metal layers on the surface of the silver layer 14, and the etching stops at the etch stop layer 11.

[0033] Step S3: Using the first processing method, without etching or oxidizing the metal layer, perform the first removal process on the photoresist on the metal layer after etching for the first time.

[0034] Use the wet stripping process method as the first processing method to remove the remaining photoresist pattern 13 after etching on the three-layer metal layer after the opening pattern 16 is etched (the first removal process). The thickness of the remaining photoresist pattern 13 is generally 1.5 - 5 μm.

[0035] For this step of removing the photoresist using the wet stripping process, it needs to be carried out without etching or oxidizing the three-layer metal layer. Therefore, propylene glycol methyl ether acetate (PGMEA) with the above characteristics is used as the wet stripping process liquid to achieve the effect of stripping without etching or oxidizing each layer of metal.

[0036] The first time for performing the first removal process needs to be greater than the theoretical time required for over-etching the photoresist using propylene glycol methyl ether acetate.

[0037] In some embodiments, a batch wet stripping machine with 1 cleaning tank can be used to immerse the wafer with the opening pattern 16 on the three-layer metal layer in the propylene glycol methyl ether acetate in the cleaning tank to perform the first removal process on the remaining photoresist pattern 13 after wet etching.

[0038] In some embodiments, a batch wet stripping machine with 2 cleaning tanks can also be used to immerse the wafer with the opening pattern 16 on the three-layer metal layer in the propylene glycol methyl ether acetate in the 2 cleaning tanks in sequence, each performing 1 pass of the first removal process on the remaining photoresist pattern 13 after wet etching, and the sum of the processing times for the 2 passes is equal to the first time.

[0039] After the above first removal process using propylene glycol methyl ether acetate, although the photoresist can be effectively removed, serious residues will be caused. Therefore, photoresist residues 131 usually remain on the surface of the silver layer 14 and the inner wall of the opening pattern 16, as Figure 4 shown.

[0040] Step S4: Using the second processing method, without oxidizing the metal layer, perform the second removal process on the photoresist residues on the wafer for the second time.

[0041] Regarding Figure 4 the photoresist residues 131 therein, they can be removed through further processing. The method is to use the dry stripping process method as the second processing method to perform the second removal process on the photoresist residues 131 on the wafer.

[0042] In some embodiments, a dry ashing degluing process method (ASH) can be used to remove the photoresist residue 131. It should be noted that when performing dry ashing degluing, process gases containing oxygen should be avoided to prevent oxidation of metals such as silver. That is, the photoresist residue 131 present on the wafer needs to be removed for the second time without causing oxidation to each metal layer.

[0043] In this embodiment, hydrogen and nitrogen are used as process gases during dry ashing degluing to remove the photoresist residue 131 present on the wafer. Since the thickness of the photoresist residue 131 formed after treatment with propylene glycol monomethyl ether acetate is relatively thin, the dry ashing degluing process method can achieve a relatively fast removal effect on the photoresist residue 131, such that the second time for the second removal treatment will be less than the first time for the first removal treatment, and thus will not cause obvious damage to the morphology of the opening pattern 16.

[0044] In some embodiments, in the process gas during dry ashing degluing, the concentration of hydrogen is 2% to 3%, and the flow rate is 100 sccm / s to 200 sccm / s, which can achieve a good and relatively fast effect of removing the photoresist residue 131.

[0045] Step S5: Use a third treatment method to perform a third removal treatment on the particles present on the wafer for a third time without causing etching and oxidation to the metal layer.

[0046] When using the dry ashing degluing process method (ASH) to remove the photoresist residue 131, due to the cumulative effect, particle dropping problems usually occur. Therefore, a cleaning process method can be used as the third treatment method to perform a third removal treatment on the particles present on the wafer.

[0047] In some embodiments, using a deionized water cleaning process, the particles present on the wafer can be removed for the third time without causing etching and oxidation to the three metal layers.

[0048] In some embodiments, a single wafer cleaning machine with ultrasonic atomization cleaning function can be used. The wafer after the second removal treatment is placed in the single wafer cleaning machine, and ionized water is used to perform ultrasonic atomization cleaning on the surface of the wafer, which can effectively remove the particles dropped on the wafer.

[0049] In some embodiments, a tank-type cleaning machine with a gas-blowing function can also be used. The wafer after the second removal treatment is placed in a water tank filled with deionized water in the tank-type cleaning machine, and the gas-blowing function is turned on to introduce gas into the deionized water. For example, nitrogen can be introduced to produce a foaming effect in the deionized water, so as to perform overall deionized water aeration and foaming cleaning on the wafer after the second removal treatment, and the particles dropped on the wafer can also be effectively removed.

[0050] Since the deionized water cleaning process will not cause etching and oxidation to the three metal layers, the third time during cleaning can be greater than the second time during dry ashing for removing photoresist.

[0051] The surface effect of the wafer after removing particles is as Figure 5 shown. It can be seen that through the three-step combined photoresist removal process of the above-mentioned first removal treatment to the third removal treatment of the present invention, there are no longer contaminants such as photoresist, residues, and particles on the surface of the power device product wafer and inside the opening pattern 16, thus ensuring the reliability of subsequent package needle-punch testing.

[0052] In summary, the present invention replaces the existing single photoresist removal process with a three-step combined photoresist removal method including a wet photoresist removal process, a dry photoresist removal process, and a cleaning process. First, the wet photoresist removal process using propylene glycol methyl ether acetate is used to effectively remove the photoresist. Then, the dry photoresist removal process using hydrogen and nitrogen as process gases is used to remove the photoresist residue 131 after wet photoresist removal. Finally, the deionized water cleaning process is used to remove the particles generated by the dry photoresist removal process. Thus, under the condition of not causing etching and oxidation to multiple metal layers on the device, complete photoresist removal at the silver contamination level is achieved without causing treatment residues, effectively solving the serious residue problem existing in the prior art.

[0053] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. A method for removing photoresist, characterized in that, Comprising: Providing a processing object with a metal layer on its surface; Forming an opening pattern penetrating the metal layer through photolithography and etching; Using a first processing method, without etching and oxidizing the metal layer, performing a first removal treatment on the photoresist on the metal layer after etching for a first time; Using a second processing method, without oxidizing the metal layer, performing a second removal treatment on the photoresist residue on the processing object for a second time; Using a third processing method, without etching and oxidizing the metal layer, performing a third removal treatment on the particles on the processing object for a third time; The first time and the third time are greater than the second time.

2. The method for removing photoresist according to claim 1, characterized in that, The first processing method includes a wet stripping process method, the second processing method includes a dry stripping process method, and the third processing method includes a cleaning process method.

3. The method for removing photoresist according to claim 2, characterized in that, The wet stripping process method includes a wet stripping process using propylene glycol monomethyl ether acetate.

4. The method for removing photoresist according to claim 3, characterized in that, The first time is greater than the theoretical time required for over-etching the photoresist with propylene glycol monomethyl ether acetate.

5. The method for removing photoresist according to claim 3, characterized in that, Using a tank-type wet stripping machine with 1 cleaning tank, immersing the processing object in propylene glycol monomethyl ether acetate in the cleaning tank for the first removal treatment; or, using a tank-type wet stripping machine with 2 cleaning tanks, immersing the processing object in propylene glycol monomethyl ether acetate in 2 cleaning tanks in sequence for 1 pass of the first removal treatment each, and the sum of the treatment times for the 2 passes is equal to the first time.

6. The method for removing photoresist according to claim 2, characterized in that, The dry stripping process method includes a dry ashing stripping process method using a process gas without oxygen.

7. The method for removing photoresist according to claim 6, characterized in that, The process gas includes hydrogen and nitrogen.

8. The method for removing photoresist according to claim 7, characterized in that, The concentration of the hydrogen is 2% to 3%, and the flow rate is 100 sccm / s to 200 sccm / s.

9. The method for removing photoresist according to claim 2, characterized in that, The cleaning process method includes ultrasonic atomization cleaning with deionized water or aerated bubbling cleaning with deionized water.

10. The method for removing photoresist according to claim 1, characterized in that, The metal layer includes a titanium layer, a nickel vanadium layer, and a silver layer sequentially stacked on the surface of the processing object. During photolithography, the photoresist covers the surface of the silver layer.

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