A method for improving the process window of photoresist etching back

Abstract

The present invention provides a method for improving a photoresist process window for etching back. The method comprises providing a substrate, forming an active area on the surface of the substrate, forming a plurality of first structures, a plurality of second structures and a thin film layer in the active area, wherein the first structure is higher than the second structure, and the first structure has an upper structure and a lower structure; forming a carbon filling material layer with a first thickness and covering the plurality of first structures, the plurality of second structures and the thin film layer on the substrate; performing a first etching to remove the carbon filling material layer, so that the remaining thickness on the top surface of the first structure is a second thickness; performing a second etching to etch the upper structure and expose the lower structure, wherein the carbon filling material layer with the second thickness prevents the thin film layer from being etched. The present invention can simultaneously realize nickel silicide protection and defect-free, and form a process window.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for improving a process window for etching back a photoresist. Background Art

[0002] In the existing process flow of 28nm high-k dielectric photolithography materials, the process of etching back the photoresist cannot achieve nickel silicide protection and defect-free at the same time, and there is no process window; the current solution to the problem is to sacrifice the thickness of nickel silicide while ensuring defect-free, resulting in serious nickel silicide loss. At the same time, due to the different fluidity of photoresist in different density areas on the wafer pattern, the photoresist is deposited higher on the gate in the high-density area. Therefore, it is necessary to add a layer of mask to open the gate with higher photoresist accumulation and larger size first, and then perform overall etching.

[0003] The existing process flow of 28nm high-k dielectric lithography materials increases process cost and complexity, which is not conducive to product mass production. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for improving the process window of back-etching photoresist, so as to solve the problem that the back-etching photoresist process in the prior art cannot simultaneously achieve nickel silicide protection and defect-free, and has no process window.

[0005] To achieve the above-mentioned object and other related objects, the present invention provides a method for improving the process window of photoresist etching back, which at least comprises:

[0006] Step 1, providing a substrate, forming an active area on the surface of the substrate, and forming a plurality of first structures, a plurality of second structures and a thin film layer in the active area, wherein the first structure is higher than the second structure, and the first structure has an upper structure and a lower structure;

[0007] Step 2: forming a carbon filling material layer covering the plurality of first structures, the plurality of second structures and the thin film layer on the substrate; the carbon filling material layer has a first thickness;

[0008] Step 3: Perform a first etching to remove the carbon filling material layer in step 2, so that the thickness of the carbon filling material layer remaining on the top surface of the first structure is a second thickness;

[0009] Step 4: Perform a second etching process so that the upper structure is partially etched, wherein the partially etched upper structure prevents the lower structure from being etched, and the carbon filling material layer having the second thickness prevents the thin film layer from being etched.

[0010] Optionally, the thin film layer material in step one is nickel silicide.

[0011] Optionally, the carbon filling material layer in step 2 is a spin-coated carbon filling material used in a 14 nm process.

[0012] Optionally, the lower structure in step one is a gate.

[0013] Optionally, the upper structure in step one is a hard mask layer.

[0014] Optionally, the hard mask layer is divided into two layers, an upper layer is an oxide layer, and a lower layer is a silicon nitride layer.

[0015] Optionally, the second structure in step one is a welding pad.

[0016] Optionally, the carbon filling material layer in step 2 has a thickness of 1000 angstroms to 4000 angstroms.

[0017] Optionally, the second thickness in step three is 210 angstroms to 310 angstroms.

[0018] As described above, the method of improving the back-etching photoresist process window of the present invention has the following beneficial effects: saving a photomask and reducing product cost; the fluidity and gap filling advantages of the spin-coated carbon filling material used in the 14nm process can improve the flatness of the pattern, which is beneficial to reduce the pile-up problem between different density areas; the excellent thermal stability and etching resistance of the spin-coated carbon filling material used in the 14nm process provide a better etching rate process optimization window for etching, and its etching rate is smaller than that of photoresist, which makes it more convenient to maintain the stability of the etching process; compared with the photoresist solution, there is no need to consider the coverage alignment problem, and the process is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a schematic diagram of the method flow of the present invention;

[0020] Figure 2 Shows a schematic diagram of the process flow of high-k dielectric photolithography materials provided by the prior art;

[0021] Figure 3 Shown is a schematic diagram of a method for improving a process window according to the present invention;

[0022] Figure 4 It is a schematic diagram of the cross-sectional structure of a wafer after the first etching of the present invention;

[0023] Figure 5 It is a schematic diagram showing the back etching and the height of the horn of the present invention;

[0024] Figure 6 Shown is a schematic diagram of NiSi loss according to the present invention.

[0025] Among them, 1-substrate, 2-second structure, 3-first structure, 4-thin film layer, 5-carbon filling material layer, 6-lower layer structure, 7-upper layer structure. DETAILED DESCRIPTION

[0026] 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.

[0027] See also Figure 2 In the existing 28nm high-k dielectric photolithography material solution, due to the different fluidity of photoresist in different density areas on the wafer pattern, the photoresist is piled up higher on the gate in the high-density area, and the photoresist cannot be effectively flattened on the pattern. Therefore, it is necessary to add a layer of mask to open the larger gate first, reduce the higher photoresist thickness, and then perform overall etching. However, the photoresist back-etching process cannot achieve nickel silicide protection and defect-free at the same time, and there is no process window; the current solution is to sacrifice the nickel silicide thickness while ensuring defect-free, resulting in serious nickel silicide loss.

[0028] See also Figure 1 , a method for improving a photoresist process window for etching back is provided, comprising:

[0029] Step 1, providing a substrate 1, forming an active region on the surface of the substrate 1, forming a plurality of first structures 3, a plurality of second structures 2 and a thin film layer 4 in the active region, wherein the thin film layer 4 covers a local surface of the active region, wherein the first structure 3 is higher than the second structure 2, and the first structure 3 has an upper structure 7 and a lower structure 6;

[0030] In a possible implementation manner, the upper structure 7 in the first structure 3 is a hard mask layer. In a possible implementation manner, the lower structure 6 in the first structure 3 is a gate.

[0031] In a possible implementation manner, the second structure 2 is a welding pad.

[0032] In a possible implementation, the material of the thin film layer 4 in step 1 is nickel silicide. In the existing process flow of 28nm high-k dielectric lithography materials, nickel silicide loss is serious.

[0033] Step 2, see Figure 3 , forming a carbon filling material layer 5 with a first thickness covering the plurality of first structures 3, the plurality of second structures 2 and the thin film layer 4 on the substrate 1;

[0034] In one possible implementation, the carbon filling material in step 2 is LT80003 with a thickness of 1000 angstroms to 4000 angstroms. Due to the fluidity and gap filling advantages of the spin-on carbon filling material used in the 14nm process, it is not necessary to accumulate high on the pattern, and the flatness of the pattern can be improved, thus helping to reduce the accumulation problem between areas of different densities; the spin-on carbon filling material used in the 14nm process (Spin on Carbon used in 14nm Process) has excellent thermal stability and etching resistance, which provides a better etching rate process optimization window for etching.

[0035] Step 3, see Figure 4 , without the need for mask exposure and development, plasma etching is used to perform a first etching to remove the carbon filling material layer 5 in step 2, so that the remaining thickness of the top surface of the first structure 3 is the second thickness;

[0036] See also Figure 5 and Figure 6 , the horizontal axis is the thickness of the carbon filling material layer 5, and the vertical axis is the horn height, which refers to the height above the gate 6. When the carbon filling material layer 5 is used to replace the photoresist, it can be seen from the experimental results that in a possible implementation, the second thickness in step three is preferably 210 angstroms to 310 angstroms, thereby expanding the process window from 0 angstroms to 100 angstroms.

[0037] Step four, performing a second etching so that the upper structure 7 is partially etched, wherein the partially etched upper structure 7 prevents the lower structure 6 from being etched, and the carbon filling material layer having the second thickness prevents the thin film layer 4 from being etched.

[0038] In a possible implementation manner, the hard mask layer is divided into two layers, an upper layer is an oxide layer, and a lower layer is a silicon nitride layer.

[0039] Specifically, when the thickness of the oxide layer: the thickness of the silicon nitride layer is 3:1 to 4:1, the second etching step requires that the oxide layer be completely etched, and the silicon nitride layer does not need to be completely etched to protect the gate. In the actual process, there is a WET process after the second etching step to clean the silicon nitride layer.

[0040] In one possible implementation, the hard mask layer on the gate is etched until the etching reaches the silicon nitride layer on the top of the gate. As long as the etching of the oxide layer is completed, the silicon nitride layer can be completely removed by subsequent processes, and no defects will be formed. At the same time, the protective effect of the carbon filling material layer 5 will not cause damage to the nickel silicide film when the oxide layer on the gate is etched away.

[0041] 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. Therefore, 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.

[0042] In summary, the present invention saves a photomask and reduces product cost; the fluidity and gap filling advantages of the spin-coated carbon filling material used in the 14nm process can improve the flatness of the pattern, which is conducive to reducing the accumulation problem between different density areas; the excellent thermal stability and etching resistance of the spin-coated carbon filling material used in the 14nm process provide a better etching rate process optimization window for etching, and its etching rate is smaller than that of photoresist, which is more convenient for the etching process to remain stable; compared with the photoresist solution, there is no need to consider the coverage alignment problem, and the process is simpler. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a 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 process window of photoresist etching back, characterized in that: At least: Step 1, providing a substrate, forming an active area on the surface of the substrate, forming a plurality of first structures, a plurality of second structures and a thin film layer on the active area, wherein the thin film layer covers a local surface of the active area, wherein the first structure is higher than the second structure, the first structure has an upper structure and a lower structure, the lower structure is a gate, the upper structure is a hard mask layer, and the hard mask layer is divided into two layers, the upper layer is an oxide layer, and the lower layer is a silicon nitride layer; Step 2: forming a carbon filling material layer on the substrate, covering the plurality of first structures, the plurality of second structures and the thin film layer; the carbon filling material layer has a first thickness; Step 3: performing a first etching process to remove the carbon filling material layer in step 2 without the need for mask exposure and development, so that the thickness of the carbon filling material layer remaining on the top surface of the first structure is a second thickness; Step 4: Perform a second etching to etch away the oxide layer in the upper structure, wherein the retained silicon nitride layer prevents the gate from being etched, and the carbon filling material layer having the second thickness prevents the thin film layer thereunder from being etched.

2. The method for improving the photoresist process window according to claim 1, characterized in that: The material of the thin film layer in step 1 is nickel silicide.

3. The method for improving the photoresist process window according to claim 1, characterized in that: The carbon filling material layer in step 2 is a spin-coated carbon filling material used in the 14 nm process.

4. The method for improving the photoresist process window according to claim 1, characterized in that: The carbon filling material layer in step 2 has a thickness of 1000 angstroms to 4000 angstroms.

5. The method for improving the photoresist process window according to claim 1, characterized in that: The second thickness in step three is 210 angstroms to 310 angstroms.

6. The method for improving the photoresist process window according to claim 1, characterized in that: This method is used in the process flow of 28nm technology node.

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