Method for improving residues formed after mandrel removal
Through the multi-step processing of using TEOS layer and SOC layer in the semiconductor manufacturing process, the problem of silicon carbon polymer residue after removal of amorphous silicon mandrel is solved, effectively removing residues and protecting the hard mask, ensuring pattern transfer The smoothness.
Patent Information
- Application Number
- CN202310736001.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-20
- Publication Date
- 2024-12-20
AI Technical Summary
During semiconductor manufacturing, after the amorphous silicon mandrel is removed, it is difficult to completely remove the silicon carbon polymer remaining on the surface of the carbon coating, which affects the subsequent process and the transfer of the underlying pattern. The overstrengthening method will lose the TiO hard mask. Causes unfavorable graphics transfer.
The TEOS layer is used to form a mandrel structure spaced from each other, covering the SOC layer and etching to remove the mandrel structure to form a groove, and then covering the second SOC layer to fill the groove and planarize it, performing dry back-etching to remove the polymer, and finally passing through In situ ash removes the SOC layer to avoid residue retention and hard mask loss.
Effectively remove carbon-silicon polymer residues, prevent them from affecting the transfer of the underlying pattern, and avoid excessive loss of hard mask height, ensuring the smooth progress of the subsequent process.
Smart Images
Figure CN119170489A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor technology, and in particular to a method for improving residues formed after core shaft removal. Background Art
[0002] With the development of semiconductor technology, especially at 24nm and below nodes, double patterning process has been widely used due to its ability to effectively reduce line width. This solution first forms a mandrel that meets the line width and morphology requirements, and then obtains a mask layer that meets the size requirements through processes such as sidewall formation and mandrel removal to form the final small line width structure.
[0003] At present, amorphous silicon mandrels can effectively control line width and morphology and are widely used. The industry often uses a sandwich structure to directly etch out the amorphous silicon mandrel, then grow a layer of TiO on the surface of the mandrel, and finally form an amorphous silicon and TiO hard mask through sidewall etching and mandrel removal.
[0004] In the actual production process, after the amorphous silicon etching is completed, the surface of the carbon coating (SOC, spin-on-carbon) accumulates silicon-carbon polymers that are difficult to remove, forming residues after ashing (ASH, one step in-situ ashing), which causes defects in subsequent processes. Over-enhanced ASH can remove the residues, but it will lose the TiO height, which is not conducive to the transfer of the underlying pattern. Summary of the invention
[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a method for improving the residue formed after the removal of the core shaft, so as to solve the problem that in the self-aligned double patterning process in the prior art, after the amorphous silicon is removed, the carbon coating surface contains polymers, which causes residues to be formed after subsequent ashing, thereby affecting the transfer of the underlying pattern.
[0006] To achieve the above-mentioned and other related purposes, the present invention provides a method for improving the residue formed after the mandrel is removed.
[0007] Step 1, providing a TEOS layer, on which mutually spaced core shaft structures are formed, and side walls of the core shaft structures are attached with side walls;
[0008] Step 2: forming a first SOC layer to cover the surface of the TEOS layer, the mandrel structure and its sidewalls; forming a SOC structure covering the sidewalls and exposing the top of the mandrel structure by photolithography and etching;
[0009] Step 3, etching away the mandrel structure along the sidewall of the SOC structure, and forming a first groove between the sidewalls attached to the removed sidewall of the mandrel structure; after the mandrel structure is removed, a polymer is attached to the surface of the SOC structure;
[0010] Step 4: forming a second SOC layer to cover the SOC structure and fill the first groove;
[0011] Step 5: planarizing the top of the second SOC layer until the top of the SOC structure is exposed;
[0012] Step 6: performing dry etching back on the SOC structure and the second SOC layer, and etching back to the top of the sidewall to remove the portion of the SOC structure with the polymer attached to the surface;
[0013] Step seven, removing the remaining SOC structure and the remaining second SOC layer. After removing the remaining SOC structure, the area between the side walls covered by the SOC structure is exposed to form a second groove; after removing the remaining second SOC layer, the first groove is exposed.
[0014] Preferably, the method for forming the sidewall in step one includes: (1) depositing a hard mask layer on the TEOS layer to cover the core shaft structure; (2) removing the hard mask layer on the TEOS layer and the hard mask layer on the top of the core shaft structure, and the hard mask layer remaining on the sidewall of the core shaft structure is formed as the sidewall.
[0015] Preferably, the core shaft structure in step one is amorphous silicon.
[0016] Preferably, the hard mask layer in step (2) is TiO.
[0017] Preferably, the method for forming the SOC structure in step 2 includes: (a) forming a bottom anti-reflective coating on the first SOC layer and a photoresist on the bottom anti-reflective coating layer; (b) exposing and developing to form a photoresist pattern for etching the mandrel structure; (c) etching the first SOC layer according to the photoresist pattern to form a SOC structure covering the sidewalls and exposing the top of the mandrel structure.
[0018] Preferably, the polymer attached to the surface of the SOC structure in step three is a carbon silicon polymer generated during the process of etching and removing the mandrel structure.
[0019] Preferably, in step seven, an in-situ ashing method is used to remove the remaining SOC structure and the remaining second SOC layer.
[0020] Preferably, the lateral thickness of the side wall in step 3 is
[0021] As described above, the method of improving the residue formed after core shaft removal of the present invention has the following beneficial effects: the method adopted by the present invention, by covering the SOC layer twice, fills and flattens the etched grooves again, then performs SOC back etching to remove most of the SOC containing silicon-carbon polymer, and then removes the SOC by in-situ ashing, finally improving the gaps between the side walls where the residues are retained, and also avoiding the problem of excessive loss of hard mask height. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figures 1 to 6 It is a schematic diagram of the structure formed by each step of the method for improving the residue formed after the mandrel is removed in the present invention;
[0023] Figure 7 Shown is a flow chart of a method for improving residue formation after mandrel removal according to the present invention. DETAILED DESCRIPTION
[0024] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.
[0025] See also Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0026] The present invention provides a method for improving the residue formed after the mandrel is removed, such as Figure 7 As shown, including at least:
[0027] Step 1, providing a TEOS layer, wherein the TEOS layer (tetraethyl orthosilicate) has spaced-apart mandrel structures formed thereon, and the sidewalls of the mandrel structures are attached with sidewalls; Figure 1 As shown, in step 1, mutually spaced core shaft structures 02 are formed on the TEOS layer 01, and sidewalls of the core shaft structures 02 are attached with sidewalls 03.
[0028] The present invention further comprises the method for forming the sidewall 03 in step one of the present embodiment, comprising: (1) depositing a hard mask layer on the TEOS layer 01 to cover the core shaft structure; (2) removing the hard mask layer on the TEOS layer and the hard mask layer on the top of the core shaft structure, and retaining the hard mask layer on the sidewall of the core shaft structure to form the sidewall.
[0029] According to the present invention, the core shaft structure 02 in step 1 of this embodiment is amorphous silicon.
[0030] In the present invention, the hard mask layer in step (2) of this embodiment is TiO.
[0031] Step 2: forming a first SOC layer to cover the surface of the TEOS layer, the mandrel structure and its sidewalls; forming a SOC structure covering the sidewalls and exposing the top of the mandrel structure by photolithography and etching; Figure 1 As shown, in step 2, a first SOC layer 04 is formed to cover the surface of the TEOS layer 01, the mandrel structure 02 and its sidewall 03; Figure 2 As shown, a SOC structure 07 is formed by photolithography and etching to cover the sidewall 03 and expose the top of the mandrel structure 02. The SOC layer in the present invention is a carbon coating (SOC, spin-on-carbon).
[0032] The present invention further comprises the method for forming the SOC structure 06 in step 2 of the present embodiment, comprising: (a) forming a bottom anti-reflective coating layer on the first SOC layer 04 and a photoresist on the bottom anti-reflective coating layer; (b) exposing and developing to form a photoresist pattern 06 for etching the mandrel structure (the bottom anti-reflective coating layer 05 after development is located below the photoresist pattern 06); and (c) etching the first SOC layer 04 according to the photoresist pattern 06 to form a SOC structure 07 covering the sidewall 03 and exposing the top of the mandrel structure 02. Figure 2 After the SOC structure 07 is formed, the bottom anti-reflection coating 05 still remains on the top of the SOC structure 07.
[0033] Step 3: The mandrel structure is removed by etching along the sidewall of the SOC structure, and a first groove is formed between the sidewalls attached to the removed sidewall of the mandrel structure; after the mandrel structure is removed, a polymer is attached to the surface of the SOC structure; Figure 3 As shown, in step three, the core shaft structure is removed by etching along the side wall of the SOC structure 07, and a first groove 08 is formed between the side walls 03 attached to the removed side wall of the core shaft structure; after the core shaft structure is removed, a polymer is attached to the surface of the SOC structure 07.
[0034] In the present invention, further, the polymer attached to the surface of the SOC structure in step three of this embodiment is a carbon silicon polymer generated during the process of etching and removing the mandrel structure.
[0035] The present invention further comprises that the lateral thickness of the side wall 03 in step 3 of this embodiment is Figures 1 to 3 The lateral thickness of the side wall 03 is the width in the left-right direction.
[0036] Step 4: forming a second SOC layer to cover the SOC structure and fill the first groove; Figure 4 As shown, a second SOC layer 09 is formed to cover the SOC structure and fill the first groove.
[0037] Step 5: planarizing the top of the second SOC layer until the top of the SOC structure is exposed; Figure 4 As shown, in step five, the second SOC layer 09 is top-planarized until the top of the SOC structure 07 is exposed.
[0038] Step 6: Perform dry etching on the SOC structure and the second SOC layer, and etch back to the top of the sidewall to remove the portion of the SOC structure with the polymer attached to the surface; Figure 5 As shown, in step six, the SOC structure 07 and the second SOC layer 09 are dry-etched back, and the etching is continued to the top of the side wall 03 to remove the portion of the SOC structure with the polymer attached to the surface. Therefore, after the dry-etching back of the SOC structure in step six, the polymer attached to the surface of the SOC structure is also removed.
[0039] Step 7: remove the remaining SOC structure and the remaining second SOC layer. After removing the remaining SOC structure, the area between the sidewalls covered by the SOC structure is exposed to form a second groove. After removing the remaining second SOC layer, the first groove is exposed. Figure 6 As shown, step seven removes Figure 5 The remaining SOC structure 07 and the remaining second SOC layer 09 are removed, and after the remaining SOC structure 07 is removed, the area between the sidewalls 03 covered by the SOC structure 07 is exposed to form a second groove 10; after the remaining second SOC layer 09 is removed, the first groove 08 is exposed. Figure 6 It can be seen that after step seven, the core shaft structure 02 in step one is removed, and the spaced-apart sidewalls 03 are formed to serve as a small line width structure.
[0040] Furthermore, in step seven of the present embodiment, an in-situ ashing (ASH) method is used to remove the remaining SOC structure and the remaining second SOC layer.
[0041] The present invention re-covers the SOC layer, fills and flattens the etched grooves again, then performs SOC back etching to remove most of the SOC containing silicon-carbon polymer, and then removes the SOC by ashing method, and finally removes the residue, thereby avoiding the problem of excessive loss of hard mask height and facilitating the transfer of lower-layer graphics.
[0042] In summary, the method adopted by the present invention is to cover the SOC layer twice, fill and flatten the etched groove again, then perform SOC back etching, remove most of the SOC containing silicon carbon polymer, and then remove the SOC by in-situ ashing, finally improving the gap between the sidewalls where the residue is retained, and also avoiding the problem of excessive loss of hard mask height. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.
[0043] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A method for improving the formation of residues after mandrel removal, characterized in that: At least: Step 1, providing a TEOS layer, on which mutually spaced core shaft structures are formed, and side walls of the core shaft structures are attached with side walls; Step 2: forming a first SOC layer to cover the surface of the TEOS layer, the mandrel structure and its sidewalls; forming a SOC structure covering the sidewalls and exposing the top of the mandrel structure by photolithography and etching; Step 3, etching away the mandrel structure along the sidewall of the SOC structure, and forming a first groove between the sidewalls attached to the removed sidewall of the mandrel structure; after the mandrel structure is removed, a polymer is attached to the surface of the SOC structure; Step 4: forming a second SOC layer to cover the SOC structure and fill the first groove; Step 5: planarizing the top of the second SOC layer until the top of the SOC structure is exposed; Step 6: performing dry etching back on the SOC structure and the second SOC layer, and etching back to the top of the sidewall to remove the portion of the SOC structure with the polymer attached to the surface; Step seven, removing the remaining SOC structure and the remaining second SOC layer. After removing the remaining SOC structure, the area between the side walls covered by the SOC structure is exposed to form a second groove; after removing the remaining second SOC layer, the first groove is exposed.
2. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: The method for forming the sidewall in step 1 includes: (1) depositing a hard mask layer on the TEOS layer to cover the core shaft structure; (2) removing the hard mask layer on the TEOS layer and the hard mask layer on the top of the core shaft structure, and the hard mask layer remaining on the sidewall of the core shaft structure is formed into the sidewall.
3. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: The core shaft structure in step one is amorphous silicon.
4. The method for improving the residue formation after mandrel removal according to claim 2, characterized in that: The hard mask layer in step (2) is TiO.
5. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: The method for forming the SOC structure in step 2 includes: (a) forming a bottom anti-reflective coating on the first SOC layer and a photoresist located on the bottom anti-reflective coating layer; (b) exposing and developing to form a photoresist pattern for etching the mandrel structure; (c) etching the first SOC layer according to the photoresist pattern to form a SOC structure covering the sidewalls and exposing the top of the mandrel structure.
6. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: The polymer attached to the surface of the SOC structure in step three is a carbon silicon polymer generated during the process of etching and removing the mandrel structure.
7. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: In step seven, an in-situ ashing method is used to remove the remaining SOC structure and the remaining second SOC layer.
8. The method for improving the residue formation after mandrel removal according to claim 1, characterized in that: The lateral thickness of the side wall in step 3 is