Method for manufacturing cutting structure
By forming an isolation layer and a protective layer on the surface of the mandrel structure, and by using high and low concentration cleaning solutions, the problem of repeated etching at the overlap of the mandrel pattern and the cutting pattern is solved, ensuring the integrity of the hard mask layer and the underlying material, and improving the process window and yield of semiconductor manufacturing.
Patent Information
- Application Number
- CN202511784146.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-03-03
AI Technical Summary
In the prior art, there is a problem of repeated etching at the overlap of the mandrel pattern and the cutting pattern, which leads to the loss of the hard mask layer and the underlying material. Furthermore, the mandrel material is oxidized and removed during the cutting process, affecting critical dimensions and subsequent process windows.
An isolation layer is formed on the surface of the mandrel structure, and a protective layer is formed on the sidewall and hard mask layer during the cutting and etching process. The isolation layer and the protective layer are removed by a combination of high and low concentration cleaning solutions in stages to protect the mandrel structure from oxidation.
It effectively prevents repeated etching at the overlap of the mandrel/cut-off pattern, protects the integrity of the hard mask layer and the underlying material, maintains the stability of the mandrel's critical dimensions, and improves the process window and yield of subsequent processes.
Smart Images
Figure CN121604740A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for manufacturing a cutting structure. Background Technology
[0002] As the pattern size of back-end semiconductor (BEOL) processes continues to shrink, the simple self-aligned double patterning (SADP) process can no longer meet the process requirements, and self-aligned quadruple patterning (SAQP) technology needs to be introduced, usually in conjunction with a "final cut-off" process.
[0003] However, existing manufacturing processes have many shortcomings. Figure 1 A schematic diagram illustrating the manufacturing process and failure phenomena of a cutting structure in the prior art is shown. (See also...) Figure 1 It shows the process from mandrel etching (MDL2 ET), cut-off lithography (BB PH) to cut-off etching (BB ET), as well as the corresponding top view (Top), cross-sectional view (X) perpendicular to the mandrel direction and cross-sectional view (Y) parallel to the mandrel direction.
[0004] like Figure 1 As shown, existing processes typically form amorphous silicon (A-Si) mandrels over a stack of tetraethyl orthosilicate (TEOS) and organic dielectric carbon (ODC). During the cut-off lithography (BB PH) step, the cut-off region is defined by spin-coating a carbon layer (SOC) and photoresist (PR). However, in the subsequent cut-off etching (BB ET) step, severe repeated etching problems occur at the overlap between the mandrel pattern and the cut-off pattern.
[0005] Specifically, such as Figure 1 A schematic diagram of the X-section of the BB ET stage shows that, due to the material properties of ODC, the cleaving etching step not only removes the mandrel in the target area but also causes significant ODC loss, even penetrating the ODC layer and leading to loss of the underlying TEOS layer. Furthermore, the sidewalls of the mandrel (A-Si) are highly susceptible to oxidation during etching and resist removal. Combined with the high-concentration hydrofluoric acid (HF) wet cleaning required in subsequent processes to remove residues, these oxidized mandrel surfaces are removed by the HF solution. Figure 1 As shown in the top view, this unintended oxide removal caused a significant shrinkage in the critical dimension (CD) of the mandrel and formed pits in the etch stop layer, severely compressing the process window for subsequent sidewalls or carbon hard masks and reducing yield.
[0006] Therefore, there is an urgent need in the field for a new manufacturing method that can solve the problem of loss of the mandrel and hard mask layer in the cutting process without changing the main film structure. Summary of the Invention
[0007] The technical problem to be solved by this application is that in the existing multi-patterning process, there is a problem of repeated etching at the overlapping area of the mandrel pattern and the cut pattern, which leads to the loss of hard mask layer (such as ODC) and the loss of underlying material (such as TEOS). At the same time, the mandrel material and hard mask layer are oxidized and then removed by cleaning solution during the cut process, resulting in shrinkage of the mandrel's critical dimensions and affecting the subsequent process window.
[0008] To address the aforementioned technical problems, this application provides a method for manufacturing a cutting structure, comprising the following steps:
[0009] Step 1: Provide a substrate, on which a hard mask layer is formed, and on which a mandrel structure is formed;
[0010] Step 2: Form an isolation layer on the surface of the mandrel structure;
[0011] Step 3: Perform at least one cut-off photolithography and cut-off etching process to remove the isolation layer and core structure in the predetermined area; in step 3, during the cut-off etching process, a protective layer is formed on the sidewalls of the core structure and the surface of the hard mask layer not covered by the core structure.
[0012] Step 4: Perform wet cleaning process;
[0013] In step four, if the cut-off photolithography and cut-off etching processes are performed multiple times, a first concentration of cleaning solution is used for cleaning after each cut-off etching process before the last cut-off etching process; after the last cut-off etching process, a second concentration of cleaning solution is used for cleaning to remove the isolation layer and protective layer; and the second concentration is greater than the first concentration.
[0014] Preferably, in step one, the hard mask layer includes a second stop layer and a first stop layer from bottom to top, and the mandrel structure is located above the first stop layer.
[0015] Preferably, the material of the first stop layer is organic medium carbon.
[0016] Preferably, the material of the second stop layer is a silicon-containing oxide or nitride.
[0017] Preferably, the material of the second stop layer is tetraethyl orthosilicate.
[0018] Preferably, in step one, the material of the mandrel structure is amorphous silicon.
[0019] Preferably, in step two, the isolation layer is formed by atomic layer deposition.
[0020] Preferably, the isolation layer is an oxide layer.
[0021] Preferably, in step three, the protective layer is a protective oxide layer.
[0022] Preferably, in step three, the protective oxide layer is formed in situ during the cutting etching process, or by adding an oxidation process step.
[0023] Preferably, the gas used in the cutting etching process or oxidation process includes oxygen, carbon dioxide or carbon monoxide.
[0024] Preferably, in step three, the thickness of the protective layer is 20 to 40 angstroms.
[0025] Preferably, in step four, the cleaning solution is a hydrofluoric acid solution.
[0026] Preferably, the ratio of hydrofluoric acid to water in the first concentration of cleaning solution is 1:1000 to 1:5000.
[0027] Preferably, the ratio of hydrofluoric acid to water in the second concentration of cleaning solution is 1:50 to 1:500.
[0028] As described above, the manufacturing method of the cutting structure of the present invention has the following beneficial effects:
[0029] This application, by covering the surface of the formed mandrel structure with an isolation layer and forming a protective layer on the mandrel sidewall and hard mask layer surface during the cutting etching process, combined with a subsequent staged high- and low-concentration cleaning strategy, can effectively prevent repeated etching at the mandrel / cut pattern overlap without changing the main film structure of SAQP / SADP. This avoids additional loss of the hard mask layer (such as ODC) and lower-layer materials (such as TEOS) below the mandrel. At the same time, the low-concentration cleaning solution protects the oxide layer in the intermediate process, and the sacrificial isolation layer and protective layer are removed only at the end with a high-concentration cleaning solution. This ensures the integrity of the mandrel sidewall, successfully suppresses the shrinkage of the mandrel's critical dimensions, controls the critical dimension changes to a very small range, and improves the process window and yield of subsequent processes. Attached Figure Description
[0030] Figure 1 This diagram illustrates the manufacturing process and failure phenomena of cutting structures in existing technologies.
[0031] Figure 2 The diagram shows a manufacturing process flow chart of the cutting structure of the present invention.
[0032] Figure 3 The diagram shown is a schematic diagram of the device structure provided in step one of this invention.
[0033] Figure 4 The diagram shows the device structure of the present invention after the formation of the isolation layer;
[0034] Figure 5 The diagram shows the device structure of the present invention after cutting photolithography;
[0035] Figure 6 The diagram shows the device structure after cutting and etching according to the present invention.
[0036] Figure 7 The diagram shown is a schematic of the device structure after wet cleaning according to the present invention. Detailed Implementation
[0037] 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.
[0038] Figure 2 A schematic diagram of the manufacturing process of the cutting structure in one embodiment of this application is shown below. Figure 2 and subsequent intermediate structure diagrams ( Figures 3 to 7 The manufacturing method is described in detail.
[0039] This application provides a method for manufacturing a cutting structure, including:
[0040] Step 1: Provide a substrate on which a hard mask layer is formed, and a core structure 103 is formed on the hard mask layer. The substrate (not shown) may include bulk silicon, doped or undoped silicon, or an active layer of a silicon-on-insulator (SOI) substrate. Typically, the substrate may include other semiconductor materials, such as compound semiconductors like germanium, silicon carbide, gallium arsenide, indium phosphide, or silicon-germanium carbide. The substrate may also include various device structures, such as transistors, diodes, and multilayer interconnect structures.
[0041] In some embodiments, the hard mask layer includes, from bottom to top, a second stop layer 101 and a first stop layer 102, with the mandrel structure 103 located above the first stop layer 102. See also... Figure 3 , Figure 3This is a schematic diagram of the structure corresponding to step one, where the upper view is a cross-sectional view perpendicular to the mandrel extension direction (X direction), and the lower view is a cross-sectional view parallel to the mandrel extension direction (Y direction). The mandrel structure 103 is typically referred to as the second mandrel in the Self-Aligned Quadruple Patterning (SAQP) process. The SAQP process typically involves two sidewall formation and pattern transfer processes for fabricating extremely small-pitch semiconductor devices. At this stage, the mandrel structure 103 has been defined and shaped through the first round of the SADP process (including first mandrel formation, first sidewall formation, first mandrel removal, and pattern transfer). Hard mask layers (101 and 102) are located between the mandrel structure 103 and the target layer, used for the subsequent high-fidelity transfer of the final fine pattern defined by the mandrel structure 103 and the sidewalls to the target layer.
[0042] In some embodiments, the mandrel structure 103 is made of amorphous silicon. Alternatively, the material of the mandrel structure 103 may be selected from other semiconductor materials capable of being oxidized to form an oxide layer, such as polycrystalline silicon, amorphous silicon carbide compounds, or combinations thereof. The mandrel structure 103 can be deposited with an amorphous silicon layer using methods such as chemical vapor deposition (CVD), low-pressure chemical vapor deposition (LPCVD), or plasma-enhanced chemical vapor deposition (PECVD), and patterned into lines using photolithography and etching processes (i.e., the aforementioned first round of SADP pattern transfer). Amorphous silicon is chosen as the mandrel material not only because it provides good support when forming sidewalls, but also because it has the chemical property of being easily oxidized under certain conditions, which provides a basis for the subsequent formation of a protective layer.
[0043] In some embodiments, the first stop layer 102 is made of organic dielectric carbon. The first stop layer 102 is commonly referred to as ODC (Organic Dielectric Carbon) or spin-coated hard mask (SOH). It is typically formed via a spin-on coating process to planarize the underlying surface topography and serve as an anti-reflection layer during photolithography. The primary function of the ODC layer is to act as an etching stop layer during subsequent etching of the mandrel structure 103 or sidewalls. However, because carbon-based materials are extremely sensitive to oxygen plasma, conventional dicing processes often cause significant damage to them.
[0044] In some embodiments, the material of the second stop layer 101 is a silicon-containing oxide or nitride. In some embodiments, the material of the second stop layer 101 is tetraethyl orthosilicate. The second stop layer 101 can be formed by CVD or PECVD deposition using tetraethyl orthosilicate (TEOS) as a precursor. Furthermore, the material of the second stop layer 101 can also be selected from silicon oxycarbide (SiOC), silicon oxynitride (SiON), silicon nitride (SiN), or other dielectric materials. The second stop layer 101 has high mechanical strength and chemical stability, serving as a primary hard mask layer to protect the underlying target etched layer (such as a metal layer, dielectric layer, or substrate).
[0045] Step 2: Form an isolation layer 104 on the surface of the mandrel structure 103. (See also...) Figure 4 , Figure 4 This is a schematic diagram of the structure corresponding to step two. The isolation layer 104 continuously covers the top surface, side walls, and exposed upper surface of the first stop layer 102 of the mandrel structure 103.
[0046] In some embodiments, the isolation layer 104 is formed by an atomic layer deposition (ALD) process. ALD controls film growth at the single-atom-layer level by alternating pulses of precursor and reactive gases. This ensures that the isolation layer 104 has high conformability, i.e., in the densely lined regions of the mandrel structure 103 (e.g., as shown in the X-direction view), its sidewall thickness is substantially the same as its top thickness.
[0047] In some embodiments, the isolation layer 104 is an oxide layer. In some embodiments, the isolation layer 104 is a low-temperature oxide layer (LTO). Using a low-temperature process (e.g., deposition temperature below 400°C or lower) can reduce the thermal budget and prevent thermal damage to precision devices formed in previous processes. The isolation layer 104 can be made of silicon oxide (SiO2) or other metal oxides that can be removed by hydrofluoric acid. The function of the isolation layer 104 is to physically isolate the mandrel structure 103 from the subsequently coated photoresist-related materials, prevent possible chemical reactions or contamination, and serve as an initial etching buffer layer.
[0048] Step 3: Perform at least one cut-off photolithography and cut-off etching process to remove the isolation layer 104 and the core structure 103 in the predetermined area; in Step 3, during the cut-off etching process, a protective layer 108 is formed on the sidewall of the core structure 103 and the surface of the hard mask layer not covered by the core structure 103.
[0049] Please combine Figure 5 and Figure 6 .like Figure 5As shown, a filler layer 105 (e.g., SOC) is formed over the isolation layer 104 by spin coating to fill the mandrel gap, followed by the formation of an anti-reflective layer 106 (e.g., SiARC or BARC) and photoresist 107. The photoresist 107 is exposed and developed to expose the areas where the mandrel structure 103 needs to be cut.
[0050] Dry etching is then performed, such as Figure 6 As shown. The etchant sequentially passes through the anti-reflective layer 106 and the filler layer 105, removing the isolation layer 104 and the mandrel structure 103 within the opening. Crucially, during the etching of the mandrel structure 103 (amorphous silicon), a protective layer 108 is formed on the exposed sidewalls of the mandrel structure 103 and on the surface of the first stop layer 102 (see...). Figure 6 (As shown in the Y-direction view). The formation of the protective layer 108 effectively seals the sidewalls of the mandrel structure 103, preventing lateral etching and thus maintaining the perpendicularity of the lines. At the same time, the protective layer 108 covers the first stop layer 102, greatly improving the etching selectivity of the first stop layer 102, preventing excessive consumption of the ODC material by the etching gas and perforation, and ensuring the integrity of the underlying second stop layer 101.
[0051] In some embodiments, the protective layer 108 is a protective oxide layer. The main chemical component of this layer is silicon oxide, which is a surface oxidation product of the silicon-based mandrel structure 103.
[0052] In some embodiments, the protective oxide layer is formed in situ during a cut-off etching process, or by adding an oxidation process step. In some embodiments, the gases used in the cut-off etching or oxidation process steps include oxygen, carbon dioxide, or carbon monoxide. During inductively coupled plasma (ICP) or capacitively coupled plasma (CCP) etching, O2, CO2, or CO are mixed in proportion to the etching gas formulation. These oxygen-containing gases act not only as cleaners of etching byproducts but also as oxidants. Under the bombardment of high-energy plasma and chemical reactions, the exposed silicon surface is rapidly oxidized to form the protective layer 108. This in-situ formation method eliminates the need for additional equipment transfer time, improving yield.
[0053] In some embodiments, the thickness of the protective layer 108 is 20 to 40 angstroms. For example, the thickness can be controlled at around 30 angstroms. The thickness range of 20 to 40 angstroms has been rigorously process-validated: it is dense enough to withstand subsequent low-concentration cleaning, but thin enough to be completely removed without residue in the final high-concentration cleaning step.
[0054] Step 4: Perform wet cleaning process; wherein, in step 4, if the cut-off photolithography and cut-off etching processes are performed multiple times, a first concentration of cleaning solution is used for cleaning after each cut-off etching process before the last cut-off etching process; after the last cut-off etching process, a second concentration of cleaning solution is used for cleaning to remove the isolation layer 104 and the protective layer 108; and the second concentration is greater than the first concentration.
[0055] In complex SAQP pattern designs, multiple masks are often required for multiple cuts. Please refer to [link / reference]. Figure 7 This demonstrates the final state after completion. The cleaning strategy of this application is as follows: after each intermediate cutting step, only a first concentration (low concentration) of cleaning solution is used. This low concentration cleaning solution is sufficient to remove photoresist residue and polymer, but due to the dual protection of the isolation layer 104 (in the uncut area) and the protective layer 108 (on the sidewalls of the cut area), and because the concentration is insufficient to rapidly etch these oxide layers, the mandrel structure 103 is protected. After all cutting steps are completed, a second concentration (high concentration) cleaning solution is used. The high concentration cleaning solution has a higher oxide etching rate, enabling the removal of both the top isolation layer 104 and the sidewall protective layer 108. Figure 7 As shown, after removing these sacrificial layers, the remaining mandrel structure 103 not only maintains the original design's CD width (e.g., about 186 to 188 angstroms), but also has smooth, vertical sidewalls, and no pitting defects are found in the lower first stop layer 102.
[0056] In some embodiments, the cleaning solution is a hydrofluoric acid solution. Hydrofluoric acid (HF) is a standard reagent for removing silicon oxide and its derivatives, and has extremely high selectivity for amorphous silicon and carbon-based materials.
[0057] In some embodiments, the ratio of hydrofluoric acid to water in the first concentration of the cleaning solution is 1:1000 to 1:5000. This extremely dilute formulation (e.g., 1:1000) reflects strict control over membrane loss during the process.
[0058] In some embodiments, the ratio of hydrofluoric acid to water in the second concentration of the cleaning solution is 1:50 to 1:500. For example, HF solutions of 1:50, 1:100, or 1:500 can be used. This concentration is sufficient to thoroughly remove all oxide hard masks / protective layers within a short time, exposing the final semiconductor structure. Subsequently, subsequent SAQP processes can be performed on this structure, such as depositing a second sidewall material and performing anisotropic etching, ultimately forming a structure or metal interconnect structure with twice the core density.
[0059] 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 drawings 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.
[0060] 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 manufacturing a cutting structure, characterized in that, At least including: Step 1: Provide a substrate, on which a hard mask layer is formed, and on which a mandrel structure is formed; Step 2: Form an isolation layer on the surface of the mandrel structure; Step 3: Perform at least one cut-off photolithography and cut-off etching process to remove the isolation layer and the mandrel structure within the predetermined area; during the cut-off etching process, a protective layer is formed on the sidewall of the mandrel structure and the surface of the hard mask layer not covered by the mandrel structure. Step 4: Perform wet cleaning process; Wherein, if the cut-off photolithography and cut-off etching processes are performed multiple times, a first concentration of cleaning solution is used for cleaning after each cut-off etching process before the last cut-off etching process; after the last cut-off etching process, a second concentration of cleaning solution is used for cleaning to remove the isolation layer and the protective layer; and the second concentration is greater than the first concentration.
2. The manufacturing method of the cutting structure according to claim 1, characterized in that: In step one, the hard mask layer includes a second stop layer and a first stop layer from bottom to top, and the mandrel structure is located above the first stop layer.
3. The manufacturing method of the cutting structure according to claim 2, characterized in that: The material of the first stop layer is organic medium carbon.
4. The manufacturing method of the cutting structure according to claim 2, characterized in that: The material of the second stop layer is a silicon-containing oxide or nitride.
5. The method for manufacturing the cutting structure according to claim 4, characterized in that: The material of the second stop layer is tetraethyl orthosilicate.
6. The method for manufacturing the cutting structure according to claim 1, characterized in that: In step one, the material of the mandrel structure is amorphous silicon.
7. The method for manufacturing the cutting structure according to claim 1, characterized in that: In step two, the isolation layer is formed by atomic layer deposition.
8. The method for manufacturing the cutting structure according to claim 7, characterized in that: The isolation layer is an oxide layer.
9. The method for manufacturing the cutting structure according to claim 1, characterized in that: In step three, the protective layer is a protective oxide layer.
10. The method for manufacturing the cutting structure according to claim 9, characterized in that: In step three, the protective oxide layer is formed in situ during the cutting etching process, or it is formed by adding an oxidation process step.
11. The method for manufacturing the cutting structure according to claim 10, characterized in that: The gases used in the cutting etching process or the oxidation process include oxygen, carbon dioxide or carbon monoxide.
12. The method for manufacturing the cutting structure according to claim 1, characterized in that: In step three, the thickness of the protective layer is 20 to 40 angstroms.
13. The method for manufacturing the cutting structure according to claim 1, characterized in that: In step four, the cleaning solution is a hydrofluoric acid solution.
14. The method for manufacturing the cutting structure according to claim 13, characterized in that: The ratio of hydrofluoric acid to water in the first concentration of cleaning solution is 1:1000 to 1:5000.
15. The method for manufacturing the cutting structure according to claim 13, characterized in that: The ratio of hydrofluoric acid to water in the second concentration of cleaning solution is 1:50 to 1:500.