Method for removing photoresist after ion implantation

Abstract

The invention provides a method for removing photoresist after ion implantation, which comprises the following steps: providing a semiconductor structure subjected to ion implantation, the semiconductor structure comprises a semiconductor substrate and a photoresist layer located on the semiconductor substrate, the photoresist layer comprises a photoresist main body layer and a graphite carbon hard shell layer covering the photoresist main body layer, an ozone treatment device is provided, the ozone treatment device comprises a liquid tank and an ozone bubbler arranged on the bottom surface of the liquid tank, a treatment solution is placed in the liquid tank, the ozone bubbler is communicated with an ozone gas tank through a gas pipe so as to eject ozone-containing bubbles in the treatment solution, and the semiconductor structure is placed in the liquid tank, and removing the graphite carbon hard shell layer, taking out the semiconductor structure in the liquid tank, and removing the photoresist main body layer by adopting an SPM solution. According to the method for removing the photoresist after ion implantation, the photoresist which is subjected to cross-linking reaction after ion implantation can be efficiently removed with low damage, so that the process efficiency and the reliability of a device are improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor integrated circuit manufacturing technology, and relates to a method for removing photoresist after ion implantation. Background Technology

[0002] In semiconductor manufacturing, ion implantation is a core step for precisely controlling the electrical properties of materials. By selectively doping the wafer surface with a high-energy ion beam, specific conductive properties can be formed in target areas, laying the foundation for device functionality. During this process, photoresist, as a crucial masking material, must precisely block ion bombardment of non-target areas to ensure the accuracy of the doped pattern. However, the intense interaction between high-energy ions and the photoresist polymer chains can trigger significant structural modification. This triggers cross-linking reactions and causes the breakage of CH bonds within the photoresist, leading to the reconstruction of C=C double bonds or graphite-like carbon structures. These graphite-like carbon materials condense on the photoresist surface to form a dense graphite-like carbon shell with extremely high chemical stability, which is difficult to remove effectively using conventional cleaning methods.

[0003] Currently, the industry commonly employs a multi-step combined process of dry ashing and wet stripping for photoresist removal after high-dose ion implantation. For example, low-temperature oxygen plasma dry ashing weakens the cross-linked structure of the surface graphite carbon, followed by wet stripping using a strong oxidizing chemical solution, namely a sulfuric acid-hydrogen peroxide mixture (SPM solution). However, this process has significant limitations. It easily causes physical and chemical damage to the wafer substrate, such as the dielectric layer and metal wiring, and the process steps are cumbersome and the equipment investment costs are high, making it difficult to adapt to the mass production requirements of advanced processes. Furthermore, as semiconductor devices evolve towards advanced processes below 28nm, more stringent requirements are being placed on the cleaning of photoresist after high-energy ion implantation.

[0004] Therefore, how to provide a method for removing photoresist after ion implantation to efficiently and with low damage remove the graphite carbon hard shell layer formed on the surface of the photoresist after ion implantation, thereby improving process efficiency and device reliability, has become an important problem that urgently needs to be solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for removing photoresist after ion implantation, which solves the problem of difficulty in efficiently and with low damage removing photoresist after ion implantation in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a method for removing photoresist after ion implantation, comprising the following steps:

[0008] An ion-implanted semiconductor structure is provided, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer;

[0009] An ozone treatment device is provided, the ozone treatment device includes a liquid tank and an ozone bubbler disposed on the bottom surface of the liquid tank. The liquid tank contains a treatment solution, the treatment solution including NH4OH, H2O2 and H2O. The ozone bubbler is connected to an ozone cylinder through a gas pipe to spray ozone-containing bubbles into the treatment solution. The diameter of the bubbles ranges from 0.001 μm to 100 μm.

[0010] The semiconductor structure is placed in the liquid tank, and the graphite carbon hard shell layer is removed;

[0011] The semiconductor structure located in the liquid bath is removed, and the photoresist body layer is removed using an SPM solution with a temperature range of 90 ℃ to 152 ℃.

[0012] Optionally, the following steps are also included:

[0013] The semiconductor structure is placed in a fast-draining hot water bath to remove the SPM solution from the semiconductor substrate.

[0014] Remove the semiconductor substrate from the fast-drain hot water tank and use a cleaning solution to remove the residual SPM solution and photoresist particles on the semiconductor substrate;

[0015] The semiconductor structure is then placed back into the fast-drain hot water tank to remove any residual cleaning solution from the semiconductor substrate.

[0016] The semiconductor substrate located in the fast-drain hot water tank is removed and dried using an isopropanol solution.

[0017] Optionally, the temperature range of the cleaning fluid is 40 ℃ to 70 ℃.

[0018] Optionally, the temperature range of the treatment solution is 40 ℃ to 65 ℃.

[0019] Optionally, the treatment solution includes ammonia, hydrogen peroxide, and an aqueous solution, wherein the volume ratio of hydrogen peroxide to the aqueous solution is in the range of 0.03 to 0.05, and the concentration of hydrogen peroxide is in the range of 28% to 32%.

[0020] Optionally, the pH range of the treatment solution is 7 to 10.

[0021] Optionally, the frequency range of the ozone bubbler is no greater than 0.55 kW.

[0022] Optionally, the ozone intake flow rate in the trachea is in the range of 0.1 L / min to 1.5 L / min.

[0023] Optionally, the solubility of ozone in the treatment solution ranges from 85% to 98%, and the concentration of ozone ranges from 5 mg / L to 20 mg / L.

[0024] Optionally, the SPM solution comprises a concentrated sulfuric acid solution and a hydrogen peroxide solution, wherein the volume ratio of the concentrated sulfuric acid solution to the hydrogen peroxide solution is in the range of 2 to 4, the concentration of the concentrated sulfuric acid solution is in the range of 96% to 100%, and the concentration of the hydrogen peroxide solution is in the range of 28% to 32%.

[0025] As described above, the method for removing photoresist after ion implantation according to the present invention includes the following steps: providing an ion-implanted semiconductor structure, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer; providing an ozone treatment device, the ozone treatment device including a liquid tank and an ozone bubbler disposed at the bottom of the liquid tank, the liquid tank containing a treatment solution including NH4OH, H2O2 and H2O, the ozone bubbler being connected to an ozone cylinder through a gas pipe to spray ozone-containing bubbles into the treatment solution, the diameter of the bubbles being in the range of 0.001 μm to 100 μm; placing the semiconductor structure in the liquid tank; removing the graphite carbon hard shell layer; removing the semiconductor structure located in the liquid tank; and removing the photoresist body layer using an SPM solution, the temperature range of the SPM solution being 90 ℃ to 152 ℃. The photoresist removal method of the present invention generates highly oxidizing hydroxyl radicals by breaking up O3 micro-nano bubbles. The hydroxyl radicals and O3 work together to destroy the graphite carbon hard shell layer on the surface of the photoresist. Then, a relatively low-temperature SPM solution is used to remove the residual photoresist. This method can efficiently and with low damage oxidize and degrade the photoresist that has undergone cross-linking reaction after ion implantation, and ultimately achieve the dual goals of improving process efficiency and ensuring device reliability. Attached Figure Description

[0026] Figure 1 The diagram shown is a process flow diagram of the photoresist removal method after ion implantation according to the present invention.

[0027] Figure 2 The diagram shows a schematic of the ozone treatment apparatus in the method for removing photoresist after ion implantation according to the present invention.

[0028] Figure 3 The diagram shows the pathway of the ozone oxidation degradation reaction of graphene oxide in a graphite carbon hard shell.

[0029] Figure 4 The graph shows the degradation kinetics of the graphite carbon hard shell at different pH values.

[0030] Figure 5 The diagram shows the rupture process of macroscopic bubbles and micro / nano bubbles.

[0031] Figure 6 The image shows the Fourier transform infrared spectra of graphite before and after oxidation.

[0032] Figure 7 The image shows the Fourier transform infrared spectra of graphene oxide in a graphite carbon hard shell before and after oxidation.

[0033] Explanation of reference numerals in the attached figures

[0034] 1 Ozone treatment device 11 liquid tank 12 Ozone bubbler 13 Treatment solution 14 trachea 15 Ozone tank 16 bubble 17 flow equalizer 18 overflow channel S1~S4 step Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0037] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0038] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0039] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0040] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0041] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] Please see Figure 1 The diagram shows a process flow chart of the photoresist removal method after ion implantation according to the present invention, which includes the following steps:

[0043] S1: Provide an ion-implanted semiconductor structure, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer;

[0044] S2: An ozone treatment device is provided, the ozone treatment device includes a liquid tank and an ozone bubbler disposed on the bottom surface of the liquid tank, the liquid tank contains a treatment solution, the treatment solution includes NH4OH, H2O2 and H2O, the ozone bubbler is connected to an ozone cylinder through a gas pipe to spray ozone-containing bubbles into the treatment solution, the diameter of the bubbles is in the range of 0.001 μm to 100 μm;

[0045] S3: Place the semiconductor structure in the liquid tank and remove the graphite carbon hard shell layer;

[0046] S4: Remove the semiconductor structure located in the liquid tank, and remove the photoresist body layer using an SPM solution. The temperature range of the SPM solution is 90 ℃ to 152 ℃.

[0047] The following section, using a structural diagram, details the specific implementation methods for each of the above steps.

[0048] First, step S1 is performed: an ion-implanted semiconductor structure is provided, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer.

[0049] Please see again Figure 2 Step S2: Provide an ozone treatment device 1, which includes a liquid tank 11 and an ozone bubbler 12 disposed on the bottom surface of the liquid tank 11. The liquid tank 11 contains a treatment solution 13, which includes NH4OH, H2O2 and H2O. The ozone bubbler 12 is connected to an ozone cylinder 15 through a gas pipe 14 to spray ozone-containing bubbles 16 into the treatment solution 13. The diameter of the bubbles 16 ranges from 0.001 μm to 100 μm.

[0050] As an example, the temperature range of the treatment solution 13 is 40 ℃ to 65 ℃.

[0051] As an example, the treatment solution 13 includes ammonia, hydrogen peroxide, and an aqueous solution, wherein the volume ratio of hydrogen peroxide to the aqueous solution is in the range of 0.03 to 0.05, and the concentration of hydrogen peroxide is in the range of 28% to 32%.

[0052] As an example, the pH range of the treatment solution 13 is 7-10.

[0053] As an example, the frequency range of the ozone bubbler 12 is no greater than 0.55 kW.

[0054] As an example, the ozone intake flow rate in the trachea 14 is in the range of 0.1 L / min to 1.5 L / min.

[0055] As an example, the ozone treatment device 1 also includes a flow equalization plate 17 and an overflow trough 18. The flow equalization plate 17 is fixed on the side wall of the liquid tank 11 and close to the ozone bubbler 12. The uniformly opened through holes in the flow equalization plate 17 can evenly distribute the bubbles 16. The overflow trough 18 is located at the top of the liquid tank 11 to prevent the liquid level of the treatment solution 13 from being too high after the semiconductor structure is completely immersed in the liquid tank 11, which would easily cause the solution to overflow and contaminate the equipment.

[0056] Then perform step S3: place the semiconductor structure in the liquid tank 11 and remove the graphite carbon hard shell layer.

[0057] Specifically, after the ozone (O3) bubbles 16 in the liquid tank 11 burst, the ozone dissolves into the treatment solution 13 and reacts with H2O2 to generate hydroxyl radicals (·OH). The chemical formula for the reaction is H2O2 + 2O3 → 2·OH + 3O2. This results in the treatment solution 13 containing both oxidizing O3 and strongly oxidizing ·OH. Under the combined action of ·OH and ozone, the graphite carbon hard shell is oxidized and degraded, allowing it to be removed. Please refer to [link to relevant documentation]. Figure 3 The diagram shows the ozone oxidation degradation mechanism of graphene oxide in the graphite carbon hard shell. The reason why ·OH and ozone are needed is that O3 only reacts with the functionalized aromatic hydrocarbon rings. ·OH can non-selectively functionalize the aromatic hydrocarbon rings and then further oxidize them into CO2, H2O and PHA with O3.

[0058] In particular, please see Figure 4 The graph shows the degradation kinetics of graphite carbon hard shells at different pH values. It can be seen that as the pH increases from 5 to 8, the reaction kinetics of ·OH decreases from 0.216 g / L. -1 Ls -1 Increased to 0.250 g -1 Ls -1 This indicates that the reaction rate constant of ·OH increases with increasing pH, and the enhanced reactivity of ·OH free radicals contributes to increasing the rate constant during the ozonation process. Therefore, the presence of NH4OH in the treatment solution 13 can significantly enhance the reactivity of ·OH, promote the synergistic effect of ·OH and ozone, and thus improve the efficiency of removing the graphite carbon hard shell, thereby providing a basis for achieving efficient and low-damage oxidative degradation of photoresist that has undergone cross-linking reaction after ion implantation.

[0059] Please see Figure 5 The diagram illustrates the rupture process of macroscopic and micro / nanobubbles. The left side shows macroscopic bubbles 16 with a diameter greater than 100 μm, while the right side shows bubbles 16 in this embodiment with a diameter between 0.001 μm and 100 μm. Macroscopic bubbles 16 rise rapidly, and their rupture often occurs at the liquid surface, which is detrimental to the incorporation of O3 and the generation of ·OH. In contrast, the bubbles 16 in this embodiment are micro / nanobubbles (i.e., bubbles with a diameter range of 0.001 μm to 100 μm). Due to Brownian motion and buoyancy balance, they remain in the solution for a longer time than macroscopic bubbles 16 and have a strong collapse effect, rupturing inside the liquid to generate ·OH. This enables efficient removal of the graphite carbon hard shell layer. Furthermore, micro / nanobubbles 16 cause less damage to the wafer surface, thus avoiding the need for dry ashing for resist removal and reducing damage to the target cleaning structure (e.g., silicon substrate). In this embodiment, the damage rate of the semiconductor substrate can be less than 0.8%.

[0060] As an example, the diameter of the bubble 16 ranges from 1 nm to 1000 nm.

[0061] As an example, the ozone solubility in the treatment solution 13 ranges from 85% to 98%, and the ozone concentration ranges from 5 mg / L to 20 mg / L.

[0062] Then perform step S4: Remove the semiconductor structure located in the liquid tank 11, and remove the photoresist body layer using SPM solution. The temperature range of the SPM solution is 90 ℃~152 ℃.

[0063] As an example, the SPM solution includes H2SO4 and H2O2, and the volume ratio of H2SO4 to H2O2 is in the range of 2 to 4.

[0064] As an example, the following steps are also included:

[0065] (1) The semiconductor structure is placed in a fast-drain hot water bath to remove the SPM solution from the semiconductor substrate.

[0066] (2) Remove the semiconductor substrate located in the fast-drain hot water tank and use a cleaning solution to remove the residual SPM solution and photoresist particles on the semiconductor substrate.

[0067] (3) The semiconductor structure is placed back into the fast-drain hot water tank to remove the cleaning solution remaining on the semiconductor substrate.

[0068] (4) Remove the semiconductor substrate located in the fast-drain hot water tank and dry the semiconductor substrate with isopropanol solution.

[0069] Specifically, the temperature range of the cleaning solution is 40 ℃ to 70 ℃.

[0070] Specifically, the SPM solution includes a concentrated sulfuric acid solution and a hydrogen peroxide solution, wherein the volume ratio of the concentrated sulfuric acid solution to the hydrogen peroxide solution is in the range of 2 to 4, the concentration of the concentrated sulfuric acid solution is in the range of 96% to 100%, and the concentration of the hydrogen peroxide solution is in the range of 28% to 32%.

[0071] Please see Figure 6 and Figure 7 ,in, Figure 6 The images shown are Fourier transform infrared spectra of graphite before and after oxidation. Figure 7 The image shows the Fourier transform infrared spectra of graphene oxide in a graphitic carbon hard shell before and after oxidation. Figure 6In the ozonolysis process, significant changes occurred in the o-functional group both in the absence of t-BuOH (i.e., when both O3 and ·OH are reactive substances) and with t-BuOH (i.e., in the absence of ·OH). Measurements were taken... Figure 6 and Figure 7 Tables 1 and 2 are obtained by corresponding to the total C and O content in each sample:

[0072] Table 1. Comparison of total C and total O in the 6 samples shown in the figure.

[0073]

[0074] Table 2. Comparison of total C and total O in the 7 samples shown in the figure.

[0075]

[0076] Tables 1 and 2 more accurately show that the o-functional group changes in both the absence and presence of t-BuOH during ozonation, proving that both ・OH and O3 are important substances that catalyze oxidation reactions.

[0077] In summary, the method for removing photoresist after ion implantation according to the present invention includes the following steps: providing an ion-implanted semiconductor structure, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer; providing an ozone treatment device, the ozone treatment device including a liquid tank and an ozone bubbler disposed at the bottom of the liquid tank, the liquid tank containing a treatment solution including NH4OH, H2O2 and H2O; the ozone bubbler being connected to an ozone cylinder through a gas pipe to spray ozone-containing bubbles into the treatment solution, the diameter of the bubbles being in the range of 0.001 μm to 100 μm; placing the semiconductor structure in the liquid tank; removing the graphite carbon hard shell layer; removing the semiconductor structure located in the liquid tank; and removing the photoresist body layer using an SPM solution, the temperature range of the SPM solution being 90 ℃ to 152 ℃. The photoresist removal method of this invention utilizes the rupture of O3 micro / nano bubbles to generate highly oxidizing hydroxyl radicals. These hydroxyl radicals, in conjunction with O3, break down the graphite carbon hard shell layer on the photoresist surface. Then, a relatively low-temperature SPM solution is used to remove the residual photoresist. This method efficiently and with low damage oxidizes and degrades the photoresist that has undergone cross-linking reactions after ion implantation, ultimately achieving the dual goals of improved process efficiency and guaranteed device reliability. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for removing photoresist after ion implantation, characterized in that, Includes the following steps: An ion-implanted semiconductor structure is provided, the semiconductor structure including a semiconductor substrate and a photoresist layer on the semiconductor substrate, the photoresist layer including a photoresist body layer and a graphite carbon hard shell layer covering the photoresist body layer; An ozone treatment device is provided, the ozone treatment device includes a liquid tank and an ozone bubbler disposed on the bottom surface of the liquid tank. The liquid tank contains a treatment solution, the treatment solution including NH4OH, H2O2 and H2O. The ozone bubbler is connected to an ozone cylinder through a gas pipe to spray ozone-containing bubbles into the treatment solution. The diameter of the bubbles ranges from 0.001 μm to 100 μm. The semiconductor structure is placed in the liquid tank, and the graphite carbon hard shell layer is removed; The semiconductor structure located in the liquid bath is removed, and the photoresist body layer is removed using an SPM solution with a temperature range of 90 ℃ to 152 ℃.

2. The method for removing photoresist after ion implantation according to claim 1, characterized in that, It also includes the following steps: The semiconductor structure is placed in a fast-draining hot water bath to remove the SPM solution from the semiconductor substrate; Remove the semiconductor substrate from the fast-drain hot water tank and use a cleaning solution to remove the residual SPM solution and photoresist particles on the semiconductor substrate; The semiconductor structure is then placed back into the fast-drain hot water tank to remove any residual cleaning solution from the semiconductor substrate. The semiconductor substrate located in the fast-drain hot water tank is removed and dried using an isopropanol solution.

3. The method for removing photoresist after ion implantation according to claim 2, characterized in that: The temperature range of the cleaning solution is 40 ℃ to 70 ℃.

4. The method for removing photoresist after ion implantation according to claim 1, characterized in that: The temperature range of the treatment solution is 40 ℃ to 65 ℃.

5. The method for removing photoresist after ion implantation according to claim 4, characterized in that: The treatment solution includes ammonia, hydrogen peroxide, and an aqueous solution, wherein the volume ratio of hydrogen peroxide to the aqueous solution is in the range of 0.03 to 0.05, and the concentration of hydrogen peroxide is in the range of 28% to 32%.

6. The method for removing photoresist after ion implantation according to claim 4, characterized in that: The pH range of the treatment solution is 7 to 10.

7. The method for removing photoresist after ion implantation according to claim 1, characterized in that: The frequency range of the ozone bubbler is no greater than 0.55 kW.

8. The method for removing photoresist after ion implantation according to claim 1, characterized in that: The ozone intake flow rate in the trachea is in the range of 0.1 L / min to 1.5 L / min.

9. The method for removing photoresist after ion implantation according to claim 1, characterized in that: The ozone solubility in the treatment solution ranges from 85% to 98%, and the ozone concentration ranges from 5 mg / L to 20 mg / L.

10. The method for removing photoresist after ion implantation according to claim 1, characterized in that: The SPM solution comprises a concentrated sulfuric acid solution and a hydrogen peroxide solution, wherein the volume ratio of the concentrated sulfuric acid solution to the hydrogen peroxide solution is in the range of 2 to 4, the concentration of the concentrated sulfuric acid solution is in the range of 96% to 100%, and the concentration of the hydrogen peroxide solution is in the range of 28% to 32%.

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