Method for Solving Local Loading of Exposure and Etching in Self-Calibration Process

Abstract

The present invention provides a method for solving the local loading of self-calibration process exposure and etching. A substrate is provided, and a stack is formed on the substrate, and sidewalls are formed on the stack; a first mask layer covering the sidewalls is formed, and then the first mask layer is etched back to a first height so that the upper ends of the sidewalls are exposed; a second mask layer is formed on the surface of the exposed sidewalls; the first mask layer is removed, and then the lower ends of the sidewalls are etched so that the sidewalls are formed into a rectangular profile. The present invention changes the sidewall profile from inclined to vertical; since the profiles of the amorphous silicon core and the outer space region are uniform, the plasma load can be reduced, and it is easier to clean the polymer during the fin or polysilicon etching process, and bridging and block etching defects can be solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a method for solving the local loading problem of exposure and etching in a self-calibration process. Background Art

[0002] With the scaling down of FINFET (Fin Field-Effect Transistor) technology, it is necessary to generate fins or gates through SADP (Self-Aligned Double Patterning) or SAQP (Self-Aligned Quadruple Patterning) process.

[0003] The SADP or SAQP pattern transfer is based on the spacer profile, including fin generation and polycrystal generation.

[0004] Since the sidewall of amorphous silicon is controlled by the etching process, the topography of the sidewall (core) is like a sailboat, and it is difficult for the plasma to cover the core and the outer space. The etching load will cause block etching or bridging defects during the etching process.

[0005] Therefore, a method for solving the local loading problem of exposure and etching in a self-calibration process is needed. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for solving the local loading problem of exposure and etching in a self-calibration process, which is used to solve the problem that in the prior art, the topography of the sidewall is like a sailboat because of the control of the amorphous silicon core RM and the spacer etching process. Then, it is difficult for the plasma to cover the core and the outer space, and the etching load will cause block etching or bridging defects during the etching process.

[0007] To achieve the above purpose and other related purposes, the present invention provides a method for solving the local loading problem of exposure and etching in a self-calibration process, including:

[0008] Step 1: Provide a substrate, on which a stack layer is formed, and an inclined sidewall is formed on the upper surface of the stack layer;

[0009] Step 2: Form a first mask layer covering the sidewall, and then etch back the first mask layer to a first height so that the upper end of the sidewall is exposed;

[0010] Step 3: Form a second mask layer on the exposed surface of the sidewall;

[0011] Step 4: Remove the first mask layer to expose the lower end of the sidewall, and then etch the lower end of the sidewall so that the upper and lower ends of the sidewall form a vertical structure profile.

[0012] Preferably, the stack layer in Step 1 is composed of a first oxide layer, a second silicon nitride layer, and a third oxide layer stacked from bottom to top.

[0013] Preferably, the substrate in step one is a silicon substrate.

[0014] Preferably, the material of the sidewall in step one is silicon nitride.

[0015] Preferably, the material of the first mask layer in step two is a spin-on carbon mask.

[0016] Preferably, the thickness of the first mask layer in step two is 1500 Å to 2000 Å.

[0017] Preferably, the first height in step two is 400 Å to 600 Å.

[0018] Preferably, in step three, the exposed sidewall is oxidized to form the second mask layer.

[0019] Preferably, the thickness of the second mask layer in step three is 30 Å.

[0020] Preferably, in step four, the first mask layer is removed by wet cleaning.

[0021] Preferably, the etching method in step four is dry etching.

[0022] As described above, the method for solving the exposure etching local loading of the self-calibration process of the present invention has the following beneficial effects:

[0023] The present invention changes the similar sidewall profile from inclined to vertical; since the profiles of the amorphous silicon core and the outer space region are uniform, the plasma load can be reduced, and it is easier to clean the polymer during the fin or polysilicon etching process, and the bridging and block etching defects can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It shows a schematic process flow diagram of the present invention;

[0025] Figure 2 It shows a schematic diagram of the substrate of the present invention;

[0026] Figure 3 It shows a schematic diagram of forming the first mask layer of the present invention;

[0027] Figure 4 It shows a schematic diagram of the invention's back-etching of the first mask layer of the present invention;

[0028] Figure 5 It shows a schematic diagram of forming the second mask layer of the present invention;

[0029] Figure 6 It shows a schematic diagram of removing the first mask layer of the present invention;

[0030] Figure 7Shown is a schematic diagram of the etched sidewall of the present invention with a vertical profile;

[0031] Figure 8 Shown is a schematic diagram of etching a stack using the sidewall with a vertical profile as a mask according to the present invention. Specific Embodiments

[0032] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the 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. 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.

[0033] Please refer to Figure 1 , the method provided by the present invention for solving the local loading problem of self-calibration process exposure and etching includes:

[0034] Step 1, please refer to Figure 2 , provide a substrate 10, a stack is formed on the substrate 10, and a sidewall 14 is formed on the stack. Usually, the sidewall 14 (core or mandrel) has an inclined structure that is narrower at the top and wider at the bottom;

[0035] In an alternative embodiment, the stack in Step 1 is composed of a first oxide layer 11, a second nitride layer 12, and a third oxide layer 13 stacked from bottom to top. The materials of the first oxide layer 11 and the third oxide can be silicon dioxide, and usually can be formed by chemical vapor deposition process.

[0036] In an alternative embodiment, the substrate 10 in Step 1 is preferably a silicon substrate 10, and other types of materials can also be used according to actual production needs. A stack and a sidewall 14 can be formed on the silicon substrate 10, or an epitaxial layer can be formed on the substrate 10, and then a stack and a sidewall 14 can be formed on the epitaxial layer.

[0037] In an alternative embodiment, the material of the sidewall 14 in Step 1 is silicon nitride.

[0038] Step 2, please refer to Figure 3 , form a first mask layer 15 covering the sidewall 14, and then etch back the first mask layer 15 to a first height so that the upper end of the sidewall 14 is exposed, obtaining the structure as shown in Figure 4 ;

[0039] In an alternative embodiment, the material of the first mask layer 15 in Step 2 is a spin-on carbon mask of 1500 Å to 2000 Å. The spin-on carbon mask has good fluidity and can fully fill the gaps between the sidewalls 14 in the process of smaller nodes.

[0040] In an alternative embodiment, the first height in step two is 400 angstroms to 600 angstroms, that is, the lower end of the sidewall 14 is protected.

[0041] Step three, refer to Figure 5 , and form a second mask layer 16 on the surface of the exposed sidewall 14;

[0042] In an alternative embodiment, in step three, the exposed sidewall 14 is oxidized to form the second mask layer 16.

[0043] Specifically, after ozone is dissolved in water, the liquid dissolved with ozone is used to react with the exposed first mask layer 15. When the first mask layer 15 is silicon nitride, the silicon nitride can be oxidized by ozone to form an oxide layer.

[0044] In an alternative embodiment, the thickness of the second mask layer 16 in step three is 30 angstroms.

[0045] Step four, refer to Figure 6 , remove the first mask layer 15, that is, expose the lower end of the inclined sidewall 14, and then etch the lower end of the sidewall 14. A protective second mask layer 16 is formed on the upper surface of the sidewall 14, and the lower end of the exposed sidewall 14 is easy to remove, so that the upper and lower ends of the sidewall 14 form a vertical structure profile, and the structure shown in Figure 7 is obtained.

[0046] In an alternative embodiment, in step four, the first mask layer 15 is removed by wet cleaning.

[0047] Specifically, an etching solution containing sulfuric acid and hydrogen peroxide can be used to soak for 90 seconds to 120 seconds to remove the spin-on carbon mask.

[0048] In an alternative embodiment, the etching method in step four is dry etching, and the exposed lower end of the sidewall 14 can be etched into a vertical profile.

[0049] In an alternative embodiment, continuing dry etching with the sidewall 14 with a vertical profile as a mask, the structure shown in Figure 8 can be formed.

[0050] It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and ratios of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0051] In summary, the present invention changes the similar sidewall profile from inclined to vertical; due to the uniform profiles of the amorphous silicon core and the outer space region, the plasma load can be reduced, and it is easier to clean polymers during the fin or polysilicon etching process, which can solve the bridging and block etching defects. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0052] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for solving the local loading problem of exposure and etching in the self-calibration process, characterized in that, it at least includes: Step 1: Provide a substrate, on which a stack layer is formed, and an inclined sidewall is formed on the upper surface of the stack layer. The material of the sidewall is silicon nitride, and the sidewall has a sailboat shape that is narrower at the top and wider at the bottom; Step 2: Form a first mask layer covering the sidewall, and then etch back the first mask layer to a first height so that the upper end of the sidewall is exposed; Step 3: Oxidize the exposed sidewall to form a second mask layer; Step 4: Remove the first mask layer to expose the lower end of the sidewall, and then etch the lower end of the sidewall so that the upper and lower ends of the sidewall form a vertical structure profile.

2. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The stack layer in Step 1 is composed of a first oxide layer, a second silicon nitride layer, and a third oxide layer stacked from bottom to top.

3. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The substrate in Step 1 is a silicon substrate.

4. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The material of the first mask layer in Step 2 is a spin-on carbon mask.

5. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The thickness of the first mask layer in Step 2 is 1500 Å to 2000 Å.

6. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The first height in Step 2 is 400 Å to 600 Å.

7. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The thickness of the second mask layer in Step 3 is 30 Å.

8. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: In Step 4, the first mask layer is removed by wet cleaning.

9. The method for solving the local loading problem of exposure and etching in the self-calibration process according to claim 1, characterized in that: The etching method in Step 4 is dry etching.

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