Method for removing photoresist
By using a combination of hydrogen and oxygen to remove the photoresist hard layer and generate an oxide layer, the problems of photoresist residue and uneven oxide layer are solved, and the product yield and production efficiency of the semiconductor manufacturing process are improved.
Patent Information
- Application Number
- CN202410330181.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-21
- Publication Date
- 2025-09-23
AI Technical Summary
The prior art easily generates residues when removing the photoresist hard layer, and the thickness of the generated oxide layer is uneven, which affects the subsequent source and drain ion implantation and NiSi growth.
Hydrogen is used to remove the hard layer on the photoresist, and then oxygen is used to remove the remaining photoresist and generate a uniform oxide layer. The removal effect and uniformity are ensured by controlling the gas composition and injection time.
It effectively avoids the residual photoresist hard layer, improves the in-plane uniformity of the oxide layer, enhances the process window and product yield of subsequent processes, and ensures production capacity.
Smart Images
Figure CN120686554A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a method for removing photoresist. Background Art
[0002] In semiconductor manufacturing process, photolithography is a kind of technology often used, after forming patterned photoresist, can doping and etching etc. process to the part not covered by photoresist, and then photoresist is removed.At present, adopt O2 and N2H2 mixed gas to remove photoresist, can realize that generally speaking there is no residue substantially after removing photoresist.But, when carrying out source-drain ion implantation, if ion implantation amount increases, injection number of times is more, photoresist surface can form very close and hard hard layer (mainly by C polymer, dopant, sputtering Si / SiO2 composition), oxygen is faster to the etch rate of photoresist, but easily produces residue when removing hard layer, and after O2 is oxidized to form oxide layer with substrate, the in-plane uniformity of oxide layer thickness is poor, not only can affect implantation depth and implantation area, and affects subsequent source-drain NiSi growth.
[0003] Therefore, how to solve the above technical problems should be the focus of those skilled in the art. Summary of the Invention
[0004] The purpose of this application is to provide a method for removing photoresist, thereby avoiding residue when removing the hard layer on the photoresist and improving the uniformity of the generated oxide layer.
[0005] To solve the above technical problems, the present application provides a method for removing photoresist, comprising:
[0006] Using a first target gas to dry-strip the photoresist on the silicon wafer and remove the hard layer on the photoresist; the first target gas includes hydrogen;
[0007] When the hard layer is completely removed and the photoresist is partially removed, the first target gas is stopped and the second target gas is introduced to remove the remaining photoresist and generate an oxide layer of uniform thickness on the surface of the silicon wafer; the second target gas includes oxygen.
[0008] Optionally, after stopping the introduction of the first target gas and before introducing the second target gas, the process further includes:
[0009] The conversion gas is introduced to remove the residual hydrogen.
[0010] Optionally, the conversion gas may include:
[0011] A mixed gas of N2H2 and N2 is introduced.
[0012] Optionally, the first target gas further includes an inert gas, and the volume content of hydrogen is in the range of 20% to 50%.
[0013] Optionally, the inert gas includes nitrogen.
[0014] Optionally, the second target gas also includes a carrier gas, and the volume content of oxygen ranges from 30% to 90%.
[0015] Optionally, the carrier gas includes N2H2.
[0016] Optionally, when the hard layer is completely removed and the photoresist is partially removed, and before the introduction of the first target gas is stopped, the method further includes:
[0017] The introduction time of the hydrogen gas is determined by tracking the etching end point curve when the hydrogen gas is used for dry stripping.
[0018] Optionally, before introducing the second target gas, the process further includes:
[0019] The oxygen introduction time is determined according to the target thickness of the oxide layer and the oxygen introduction rate.
[0020] A method for removing photoresist provided in the present application includes: using a first target gas to dry-strip the photoresist on a silicon wafer and remove a hard layer located on the photoresist; the first target gas includes hydrogen; when the hard layer is completely removed and the photoresist is partially removed, the first target gas is stopped from being introduced and a second target gas is introduced to remove the remaining photoresist and generate an oxide layer of uniform thickness on the surface of the silicon wafer; the second target gas includes oxygen.
[0021] As can be seen, hydrogen is used in this application to remove the hard layer on the photoresist. Hydrogen has a good effect on removing the hard layer, which can completely remove the hard layer on the photoresist to avoid residue. It also has a good etching uniformity on the photoresist, making the surface uniformity of the silicon wafer better after the photoresist is removed, and thus making the thickness uniformity of the generated oxide layer better, avoiding the impact on subsequent processes, effectively improving the process window of subsequent processes, and thus improving product yield. A portion of the photoresist is first removed with hydrogen, and the remaining photoresist is removed with oxygen. Oxygen has a faster etching rate for photoresist, ensuring that the etching rate will not decrease and ensuring production capacity. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0023] Figure 1 Schematic diagram of the mechanism of oxide layer residue blocking NiSi growth;
[0024] Figure 2 A process for removing photoresist provided in an embodiment of the present application Figure 1 ;
[0025] Figure 3 A process for removing photoresist provided in an embodiment of the present application Figure 2 . DETAILED DESCRIPTION
[0026] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present application.
[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0028] Please refer to Figure 1 Taking PMOS as an example, this article explains the mechanism by which residual oxide layers hinder NiSi growth. After debonding, the oxide layers on both sides of the PMOS source and drain are relatively thick and uneven, resulting in a low degree of Si amorphization during the subsequent PAI (self-aligned silicide amorphization) process. Prior to NiSi growth, a SiCoNi WET (wet removal) process is performed on the underlying oxide layer. However, this oxide layer cannot be completely removed, preventing the deposited Ni from fully bonding with the Si, thus hindering NiSi growth.
[0029] As described in the background technology section, in the related art, when oxygen is used to remove photoresist, residue is easily generated when removing the hard layer on the photoresist. Furthermore, the thickness uniformity of the oxide layer generated on the silicon wafer surface is relatively poor, which not only affects the injection depth and injection area, but also affects the subsequent NiSi growth.
[0030] In view of this, the present application provides a method for removing photoresist, please refer to Figure 2 , the method comprising:
[0031] Step S101: using a first target gas to perform dry stripping on the photoresist on the silicon wafer and remove the hard layer on the photoresist; the first target gas includes hydrogen.
[0032] During the ashing reaction, hydrogen (H2) reacts with the photoresist, and the reaction formula is as follows:
[0033] H2+nC X H Y (photoresist)→nC X H Y+1 .
[0034] The hydrogen stripping rate is slow and uniform, which can reduce the normal photoresist consumption when removing the hard layer, improve the hard layer removal ability, effectively reduce the residue, and thus avoid the residue affecting the in-plane uniformity of the oxide.
[0035] In order to control the etching rate of hydrogen on the photoresist and the hard layer and ensure the safety of the etching process, in one embodiment of the present application, the first target gas also includes an inert gas, and the volume content of hydrogen is in the range of 20% to 50%. For example, the volume content of hydrogen can be 20%, 30%, 40%, 50%, etc.
[0036] If the volume content of hydrogen is lower than 20%, the ability to remove the hard layer will be very weak, affecting the removal effect. If the volume content of hydrogen is higher than 50%, hydrogen will penetrate into the semiconductor device and affect the device performance.
[0037] In order to reduce the removal cost, as an embodiment, the inert gas includes nitrogen. Of course, in other embodiments, other inert gases such as helium, neon, etc. can also be used.
[0038] Step S102: When the hard layer is completely removed and the photoresist is partially removed, the first target gas is stopped and the second target gas is introduced to remove the remaining photoresist and generate an oxide layer of uniform thickness on the surface of the silicon wafer; the second target gas includes oxygen.
[0039] Oxygen (O2) reacts with the photoresist according to the following reaction formula:
[0040] O2+nC X H Y (photoresist)→CO2+H2O.
[0041] Oxygen has a faster etching rate for photoresist and higher etching efficiency.
[0042] In order to control the etching rate of oxygen on the photoresist and ensure the safety of the etching process, in one embodiment of the present application, the second target gas also includes a carrier gas, and the volume content of oxygen ranges from 30% to 90%. For example, the volume content of oxygen can be 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc.
[0043] If the volume content of oxygen is lower than 30%, the ability to remove the photoresist will be very weak, affecting the removal effect. If the volume content of oxygen is higher than 90%, oxygen will penetrate into the semiconductor device and affect the device performance.
[0044] The carrier gas includes but is not limited to an inert gas and N2H2. When the carrier gas is N2H2, the cost can be reduced and a better process effect can be obtained.
[0045] After removing the remaining photoresist, the oxygen in the second target gas reacts with the silicon wafer to form a silicon dioxide oxide layer.
[0046] When oxygen is introduced, the oxygen flow rate of the machine is constant. The amount of oxygen introduced can be determined by adjusting the oxygen introduction time. The amount of oxygen introduced is not limited in this application.
[0047] In one embodiment of the present application, before the second target gas is introduced, the method further includes:
[0048] The oxygen introduction time is determined according to the target thickness of the oxide layer and the oxygen introduction rate.
[0049] The hydrogen reacts with the photoresist, and the hydrogen introduction time can be determined based on the etching endpoint tracking curve (EPD curve). As an embodiment, when the hard layer is completely removed and the photoresist is partially removed, before the introduction of the first target gas is stopped, the method further includes:
[0050] The introduction time of the hydrogen gas is determined by tracking the etching end point curve when the hydrogen gas is used for dry stripping.
[0051] The method of the present application can be applied in source-drain ion implantation processes.
[0052] In this embodiment, hydrogen is used to remove the hard layer on the photoresist. Hydrogen is highly effective at removing hard layers, completely removing the hard layer from the photoresist and preventing residue. It also provides improved photoresist etching uniformity, resulting in a more uniform silicon wafer surface after photoresist removal. This, in turn, improves the thickness uniformity of the resulting oxide layer, preventing any impact on subsequent processes and effectively increasing the process window for subsequent processes, thereby improving product yield. A portion of the photoresist is first removed with hydrogen, while the remaining photoresist is removed with oxygen. Oxygen has a faster etching rate for photoresist, ensuring that the etching rate does not decrease and maintaining production capacity.
[0053] Based on the above embodiments, in one embodiment of the present application, please refer to Figure 3 , the method of removing the photoresist includes:
[0054] Step S201: using a first target gas to perform dry stripping on the photoresist on the silicon wafer and remove the hard layer on the photoresist; the first target gas includes hydrogen.
[0055] Step S202: When the hard layer is completely removed and the photoresist is partially removed, the introduction of the first target gas is stopped and the conversion gas is introduced to remove the residual hydrogen.
[0056] Since the mixture of hydrogen and oxygen has certain safety risks, in order to ensure the safety of goods passing, the hydrogen remaining when removing the hard layer and photoresist is removed by introducing conversion gas, and then oxygen is introduced.
[0057] The flow rate and volume of the conversion gas introduced are not limited in this application, as long as the hydrogen is completely removed. For example, the flow rate of the conversion gas introduced can be 5000 sccm (standard cubic centimeter per minute).
[0058] In order to enable the conversion gas to have the effect of connecting the first target gas and the second target gas, the conversion gas is a mixed gas of an inert gas and a carrier gas.
[0059] As an implementable embodiment, when the inert gas is nitrogen and the carrier gas is N2H2, introducing the conversion gas includes introducing a mixed gas of N2H2 and N2.
[0060] Step S203: introducing a second target gas to remove the remaining photoresist and form an oxide layer with a uniform thickness on the surface of the silicon wafer; the second target gas includes oxygen.
[0061] The following describes the photoresist removal process in this application using a specific example. The ventilation process includes nine steps, as shown in Table 1. The introduction of the first target gas (a mixture of hydrogen and nitrogen) is described in Steps 1 to 4 of Table 1. The flow rates of hydrogen and nitrogen are selected appropriately. Step 5 introduces the conversion gas (a mixture of nitrogen and N2H2). The flow rates of nitrogen and N2H2 are both 5000 sccm. The second target gas (a mixture of oxygen and N2H2) is then introduced. These steps are described in Steps 6 to 9. The flow rates of oxygen and N2H2 are selected appropriately.
[0062] Table 1
[0063] Recipe Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Step 9 <![CDATA[O2 / sccm]]> 0 0 0 0 0 fixed fixed fixed fixed <![CDATA[N2H2 / sccm]]> 0 0 0 0 5000 fixed fixed fixed fixed <![CDATA[H2 / sccm]]> fixed fixed fixed fixed 0 0 0 0 0 <![CDATA[N2 / sccm]]> fixed fixed fixed fixed 5000 0 0 0 0
[0064] In Table 1, the flow rate "fixed" is set according to actual conditions (such as the thickness of the photoresist, the thickness of the hard layer, etc.).
[0065] The technical solution of this application was verified through simulation experiments on bare silicon wafers. After photoresist patterning and high-energy particle implantation, the dry stripping step used the H2 and N2 mixed gas solution of this application solution. This significantly reduced photoresist and hard layer residue, controlled the O2 injection duration, protected the device's WAT (wafer acceptance test) performance, and enabled complete removal of the oxide layer in the subsequent oxide removal process.
[0066] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.
[0067] The method for removing photoresist provided by the present application is described in detail above. Specific examples are used herein to illustrate the principle and implementation of the present application. The description of the above embodiments is only used to help understand the scheme and core idea of the present application. It should be pointed out that, for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can also be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.
Claims
1. A method for removing photoresist, characterized in that, include: Using a first target gas to dry-strip the photoresist on the silicon wafer and remove the hard layer on the photoresist; the first target gas includes hydrogen; When the hard layer is completely removed and the photoresist is partially removed, the first target gas is stopped and the second target gas is introduced to remove the remaining photoresist and generate an oxide layer of uniform thickness on the surface of the silicon wafer; the second target gas includes oxygen.
2. The method for removing photoresist according to claim 1, wherein After stopping the introduction of the first target gas and before introducing the second target gas, the method further includes: The conversion gas is introduced to remove the residual hydrogen.
3. The method for removing photoresist according to claim 2, wherein: The conversion gas includes: A mixed gas of N2H2 and N2 is introduced.
4. The method for removing photoresist according to claim 1, wherein: The first target gas also includes inert gas, and the volume content of hydrogen is in the range of 20% to 50%.
5. The method for removing photoresist according to claim 4, wherein: The inert gas includes nitrogen.
6. The method for removing photoresist according to claim 1, wherein: The second target gas also includes carrier gas, and the volume content of oxygen ranges from 30% to 90%.
7. The method for removing photoresist according to claim 6, wherein: The carrier gas includes N2H2.
8. The method for removing photoresist according to claim 1, wherein: When the hard layer is completely removed and the photoresist is partially removed, and before the introduction of the first target gas is stopped, the method further includes: The introduction time of the hydrogen gas is determined by tracking the etching end point curve when the hydrogen gas is used for dry stripping.
9. The method for removing photoresist according to claim 1, wherein: Before introducing the second target gas, the method further includes: The oxygen introduction time is determined according to the target thickness of the oxide layer and the oxygen introduction rate.