Method for removing hard mask layer in self-aligned multiple patterning process

Abstract

The invention provides a method for removing a hard mask layer in a self-aligned multi-pattern process. The method comprises the following steps of: forming a bottom-layer mandrel pattern formed by etching on a front-layer structure and a hard mask layer positioned on the bottom-layer mandrel pattern; forming an etching protection layer covering the bottom core shaft pattern and the hard mask layer, wherein the etching protection layer comprises organic matters; the etching protection layer is etched back until the hard mask layer is completely exposed; etching and removing the hard mask layer by using plasma with a high selection ratio; and removing the etching protection layer by using an ashing process and a wet cleaning method in sequence.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a method for removing a hard mask layer in a self-aligned multiple patterning process. Background Art

[0002] SAQP (Self-aligned Quadruple Patterning) process, which uses two layers of A-Si mandrel (amorphous silicon mandrel pattern) for pattern transfer to compensate for the limitation of exposure limit to complete the design size of smaller semiconductor critical dimensions;

[0003] During the process, due to the process characteristics of SAQP itself, there is a layer of silicon oxide between the first mandrel pattern and the second mandrel pattern as a stop layer for etching the first mandrel pattern and a hard mask for the second mandrel pattern. After etching the second mandrel pattern, the hard mask needs to be removed. Since the bottom of the second mandrel pattern is also a silicon oxide layer, the methods commonly used at present include:

[0004] Step 1: Please refer to Figure 1 , forming a bottom layer mandrel pattern 102 formed by etching on the front layer structure 101 and a hard mask layer 103 located on the bottom layer mandrel pattern 102;

[0005] Step 2: forming an etching protection layer 104 covering the bottom mandrel pattern 102 and the hard mask layer 103, forming a Figure 2 In the structure shown, the etching protection layer 104 is usually a spin-on carbon hard mask layer (SOC);

[0006] Step 3: Etch back the protective layer 104 until the hard mask layer 103 is completely exposed, forming a Figure 3 The structure shown;

[0007] Step 4: Remove the hard mask layer 103 by using a chemical gas dry etching process; the chemical gas dry etching process contains hydrogen fluoride (HF) in the reaction gas, and HF will cause the SOC to shrink, thereby causing a gap between the SOC and the underlying mandrel pattern 102, forming a gap as shown in FIG. Figure 4 In the structure shown, the reaction gas of the chemical gas dry etching process will drill into the bottom along the gap, thereby causing the loss of the bottom front layer structure 101;

[0008] Step 5: Remove the etching protection layer 104 by wet cleaning. Long-term wet etching will cause the bottom front layer structure 101 to be damaged, forming Figure 5 The structure shown.

[0009] Currently, the problem cannot be fundamentally solved by reducing the chemical gas dry etching reaction time by thinning the hard mask layer 103 or by selecting a SOC that is relatively resistant to hydrogen fluoride to reduce the degree of SOC shrinkage, thereby reducing the loss of the bottom front layer structure.

[0010] In order to solve the above problems, it is necessary to propose a novel method for removing the hard mask layer in the self-aligned multi-patterning process. Summary of the invention

[0011] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for removing a hard mask layer in a self-aligned multi-patterning process, so as to solve the problem of etching loss caused to the previous layer structure in the process of removing the hard mask layer and the etching protection layer in the self-aligned multi-patterning process in the prior art.

[0012] To achieve the above-mentioned object and other related objects, the present invention provides a method for removing a hard mask layer in a self-aligned multi-patterning process, comprising:

[0013] Step 1: forming a bottom layer mandrel pattern formed by etching on the front layer structure and a hard mask layer located on the bottom layer mandrel pattern;

[0014] Step 2: forming an etching protection layer covering the bottom mandrel pattern and the hard mask layer, wherein the etching protection layer comprises organic matter;

[0015] Step 3, etching back the etching protection layer until the hard mask layer is completely exposed;

[0016] Step 4: removing the hard mask layer by using high selectivity plasma etching;

[0017] Step 5: Remove the etching protection layer by using an ashing process and a wet cleaning method in sequence.

[0018] Preferably, the front layer structure in step one is a film layer structure formed on the substrate.

[0019] Preferably, the material of the hard mask layer in step 1 is silicon dioxide.

[0020] Preferably, the mandrel pattern in step one is a patterned amorphous silicon layer.

[0021] Preferably, the etching protection layer in step 2 is a spin-coated carbon hard mask layer.

[0022] Preferably, the back etching method in step three is dry etching.

[0023] As described above, the method for removing the hard mask layer in the self-aligned multi-patterning process of the present invention has the following beneficial effects:

[0024] The present invention utilizes high selectivity plasma etching to remove the hard mask layer without causing the etching protection layer to shrink, thereby better protecting the bottom front layer structure from being lost; and utilizes an ashing process and a wet cleaning method to remove the etching protection layer, thereby reducing the wet cleaning time and thus reducing the etching of the bottom front layer structure by the wet cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a bottom mandrel pattern and a hard mask layer of the prior art is shown;

[0026] Figure 2 It is a schematic diagram of forming an etching protection layer in the prior art;

[0027] Figure 3 It is a schematic diagram showing the prior art of etching back the protective layer until the hard mask layer is completely exposed;

[0028] Figure 4 A schematic diagram showing the shrinkage and generation of cracks in the etching protection layer caused by the chemical gas dry etching process in the prior art;

[0029] Figure 5 A schematic diagram showing a prior art wet etching method for forming grooves on a front layer structure;

[0030] Figure 6 Shown is a schematic diagram of the process flow of the present invention;

[0031] Figure 7 Shown is a schematic diagram of the bottom mandrel pattern and hard mask layer of the present invention;

[0032] Figure 8 It is a schematic diagram of forming an etching protection layer according to the present invention;

[0033] Fig. 9 It is a schematic diagram showing the etching back of the protective layer until the hard mask layer is completely exposed according to the present invention;

[0034] Fig.10 It is a schematic diagram showing the removal of the hard mask layer by using high selectivity plasma etching according to the present invention;

[0035] Fig.11 It is a schematic diagram showing that the wet etching of the present invention does not form grooves on the front layer structure. DETAILED DESCRIPTION

[0036] 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.

[0037] See also Figure 6 The present invention provides a method for removing a hard mask layer in a self-aligned multi-patterning process, comprising:

[0038] Step 1: Please refer to Figure 7 , forming a bottom layer mandrel pattern 202 formed by etching on the front layer structure 201 and a hard mask layer 203 located on the bottom layer mandrel pattern 202;

[0039] Specifically, taking the self-aligned quadruple patterning technology as an example, after an upper core shaft pattern is formed on the amorphous silicon layer above the patterning, a side wall located below the upper core shaft pattern is formed by deposition and back etching, and then the upper core shaft pattern is removed. Then, the hard mask layer 203 and the amorphous silicon layer below are self-alignedly etched using the side wall as a mask to form a bottom core shaft pattern 202.

[0040] In some embodiments, the front layer structure 201 in step 1 is a film layer structure formed on a substrate, and its material may be silicon dioxide.

[0041] In some embodiments, the material of the hard mask layer 203 in step 1 is silicon dioxide.

[0042] In some embodiments, the bottom mandrel pattern 202 in step 1 is a patterned amorphous silicon layer.

[0043] Step 2: forming an etching protection layer 204 covering the bottom mandrel pattern 202 and the hard mask layer 203, forming a Figure 8 In the structure shown, the etching protection layer 204 includes organic matter;

[0044] In some embodiments, the etching protection layer 204 in step 2 is a spin-coated carbon hard mask layer 203, which has good fluidity and can cover the pattern in a smaller process node. In other embodiments, the etching protection layer 204 can also be made of other materials with good fluidity and can be removed by an ashing process.

[0045] Step 3: Etch back the protective layer 204 until the hard mask layer 203 is completely exposed, forming a Fig. 9 The structure shown;

[0046] In some embodiments, the etching back method in step three is dry etching.

[0047] Step 4: Remove the hard mask layer 203 by high selectivity plasma etching to form Fig.10 The structure shown; this method does not cause the etching protection layer 204 to shrink, thereby better protecting the bottom front layer structure 201 from being lost;

[0048] Step 5: Remove the etching protection layer 204 by using an ashing process and a wet cleaning method to form a Fig.11 In the structure shown, the ashing process generates oxygen plasma, and the oxygen free radicals in the plasma burn the organic components of the etching protection layer 204, thereby reducing the wet cleaning time and thus reducing the etching of the bottom front layer structure 201 by the wet cleaning.

[0049] In some embodiments, the above method is used for self-aligned quadruple patterning technology. In other embodiments, the method of the present invention can also be used for self-aligned patterning technology with more layers.

[0050] 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.

[0051] In summary, the present invention utilizes high selectivity plasma etching to remove the hard mask layer, which will not cause the etching protection layer to shrink, thereby better protecting the bottom front layer structure from being lost; the etching protection layer is removed by an ashing process and a wet cleaning method, which reduces the wet cleaning time, thereby reducing the etching of the bottom front layer structure by the wet cleaning. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0052] 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 removing a hard mask layer in a self-aligned multi-patterning process, characterized in that: At least: Step 1: forming a bottom layer mandrel pattern formed by etching on the front layer structure and a hard mask layer located on the bottom layer mandrel pattern; Step 2: forming an etching protection layer covering the bottom mandrel pattern and the hard mask layer, wherein the etching protection layer comprises organic matter; Step 3, etching back the etching protection layer until the hard mask layer is completely exposed; Step 4: removing the hard mask layer by using high selectivity plasma etching; Step 5: Remove the etching protection layer by using an ashing process and a wet cleaning method in sequence.

2. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 1, wherein: The front layer structure in step 1 is a film layer structure formed on the substrate.

3. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 2, wherein: The material of the hard mask layer in step 1 is silicon dioxide.

4. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 1, wherein: The mandrel pattern in step one is a patterned amorphous silicon layer.

5. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 1, wherein: The etching protection layer in step 2 is a spin-coated carbon hard mask layer.

6. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 1, wherein: The back etching method in step three is dry etching.

7. The method for removing a hard mask layer in a self-aligned multi-patterning process according to claim 1, wherein: The method is used for self-aligned quadruple patterning technology.

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