# Patent

## Title
Method for forming semiconductor device structure

## Abstract

A method for forming a semiconductor device structure is provided. The semiconductor device structure includes forming a film over a substrate. The semiconductor device structure includes forming a first mask layer over the film. The semiconductor device structure includes forming a second mask layer over the first mask layer. The second mask layer exposes a first portion of the first mask layer. The semiconductor device structure includes performing a plasma etching and deposition process to remove the first portion of the first mask layer and to form a protection layer over a first sidewall of the second mask layer. The first mask layer exposes a second portion of the film after the plasma etching and deposition process. The semiconductor device structure includes removing the second portion using the first mask layer and the second mask layer as an etching mask.

## Background
BACKGROUND
The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs. Each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs.
In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometric size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling-down process generally provides benefits by increasing production efficiency and lowering associated costs.
However, since feature sizes continue to decrease, fabrication processes continue to become more difficult to perform. Therefore, it is a challenge to form reliable semiconductor devices at smaller and smaller sizes.



BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
FIGS. 1A-1H are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments.
FIG. 2 is a top view of the semiconductor device structure of FIG. 1C.
FIGS. 3A-3F are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments.
FIGS. 4A-4G are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments.
FIG. 5 is a top view of the semiconductor device structure of FIG. 4A.



DETAILED DESCRIPTION
The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. It should be understood that additional operations can be provided before, during, and after the method, and some of the operations described can be replaced or eliminated for other embodiments of the method.
FIGS. 1A-1H are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. FIG. 2 is a top view of the semiconductor device structure of FIG. 1C, in accordance with some embodiments. As shown in FIG. 1A, a substrate 110 is provided. The substrate 110 includes a semiconductor wafer (such as a silicon wafer) or a portion of a semiconductor wafer, in accordance with some embodiments.
In some embodiments, the substrate 110 is made of an elementary semiconductor material including silicon or germanium in a single crystal, polycrystal, or amorphous structure. In some other embodiments, the substrate 110 is made of a compound semiconductor, such as silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, an alloy semiconductor, such as SiGe, or GaAsP, or combinations thereof. The substrate 110 may also include multi-layer semiconductors, semiconductor on insulator (SOI) (such as silicon on insulator or germanium on insulator), or combinations thereof.
As shown in FIG. 1A, an isolation structure 120 is formed in the substrate 110 to define various active regions 112 of the substrate 110, and to electrically isolate neighboring devices (e.g. transistors) from one another. The isolation structure 120 surrounds the active regions 112.
The isolation structure 120 is made of a dielectric material, in accordance with some embodiments. The dielectric material includes silicon oxide, silicon nitride, silicon oxynitride, fluoride-doped silicate glass (FSG), a low-K dielectric material, other suitable materials, or combinations thereof, in accordance with some embodiments. The isolation structure 120 is formed by using an isolation technology, such as local oxidation of semiconductor (LOCOS), shallow trench isolation (STI), or the like, in accordance with some embodiments.
In some embodiments, the formation of the isolation structure 120 includes patterning the substrate 110 by a photolithography process, etching a trench in the substrate 110 (for example, by using a dry etching, wet etching, or plasma etching process, or a combination thereof), and filling the trench (for example, by using a chemical vapor deposition process) with the dielectric material. In some embodiments, the filled trench may have a multi-layer structure, such as a thermal oxide liner layer filled with silicon nitride or silicon oxide.
As shown in FIG. 1A, a gate dielectric layer 130 is formed over the substrate 110 and the isolation structure 120, in accordance with some embodiments. The gate dielectric layer 130 is made of silicon oxide, silicon oxynitride, a high dielectric constant material (high-k material), or a combination thereof, in accordance with some embodiments. The gate dielectric layer 130 is formed using a chemical vapor deposition process or a physical vapor deposition process, in accordance with some embodiments.
As shown in FIG. 1A, a gate material layer 140a is formed over the gate dielectric layer 130, in accordance with some embodiments. The gate material layer 140a is made of polysilicon or other suitable materials, in accordance with some embodiments. The gate material layer 140a is formed using a chemical vapor deposition process or a physical vapor deposition process, in accordance with some embodiments.
As shown in FIG. 1A, a film 150 is formed over the gate material layer 140a, in accordance with some embodiments. The film 150 is configured to be a hard mask layer during an etching process that is subsequently performed, in accordance with some embodiments. The film 150 includes silicon oxide, silicon nitride (e.g., Si3N4), SiON, SiC, SiOC, a combination thereof, or another suitable material, in accordance with some embodiments. The film 150 may be formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), spin-on coating, or other applicable processes.
As shown in FIG. 1A, an anti-reflection layer 160 is formed over the film 150, in accordance with some embodiments. The anti-reflection layer 160 is also referred to as a mask layer, in accordance with some embodiments. The anti-reflection layer 160 includes a polymer material (such as a bottom anti-reflective coating material) or another suitable material. The anti-reflection layer 160 is formed using a spin coating process or another suitable process.
As shown in FIG. 1A, a mask layer 170 is formed over the anti-reflection layer 160, in accordance with some embodiments. The mask layer 170 includes a polymer material (such as a photoresist material), in accordance with some embodiments. The mask layer 170 includes a photoresist layer, in accordance with some embodiments. The mask layer 170 is formed using a spin coating process or another suitable process. In some embodiments, the film 150, the anti-reflection layer 160, and the mask layer 170 are made of different materials.
As shown in FIG. 1B, a portion of the mask layer 170 is removed, in accordance with some embodiments. The removal process includes a photolithography process, in accordance with some embodiments. The mask layer 170 exposes a portion 162 of the anti-reflection layer 160, in accordance with some embodiments.
As shown in FIGS. 1C and 2, a plasma etching and deposition process is performed over the anti-reflection layer 160 and the mask layer 170, in accordance with some embodiments. The plasma etching and deposition process removes the portion 162 of the anti-reflection layer 160 and form a protection layer 180 over sidewalls 172 of the mask layer 170, in accordance with some embodiments.
The protection layer 180 is further formed over sidewalls 164 of the anti-reflection layer 160, in accordance with some embodiments. The protection layer 180 includes a polymer material, in accordance with some embodiments. In some embodiments, the protection layer 180 continuously covers the sidewalls 164 and 172.
The protection layer 180 surrounds the mask layer 170 and the anti-reflection layer 160, in accordance with some embodiments. The protection layer 180 continuously surrounds the mask layer 170 and the anti-reflection layer 160, in accordance with some embodiments. After the plasma etching and deposition process, the anti-reflection layer 160 and the protection layer 180 expose a portion 152 of the film 150, in accordance with some embodiments.
In some embodiments, the plasma etching and deposition process uses a processing gas. The processing gas is configured to be an etching gas and a polymer gas, in accordance with some embodiments. The polymer gas is configured to provide a polymer deposition during the plasma etching and deposition process, in accordance with some embodiments.
The processing gas includes CHF3, CH2F2, CH3F, or a combination thereof. The processing gas includes pure CHF3 and unavoidable impurity gas(es), in accordance with some embodiments. The processing gas includes pure CH2F2 and unavoidable impurity gas(es), in accordance with some embodiments. The processing gas includes pure CH3F and unavoidable impurity gas(es), in accordance with some embodiments.
During the plasma etching and deposition process, an exposed portion of the mask layer 170 may be etched away. Since the protection layer 180 is formed over sidewalls 172 of the mask layer 170 during the plasma etching and deposition process, the protection layer 180 reduces the etching rate of the mask layer 170 adjacent to the sidewalls 172.
Therefore, the mask layer 170, which has been etched, is able to maintain the desired width W1, which is greater than that of the mask layer, which has been etched without the protection layer 180. Furthermore, the protection layer 180 over the sidewalls 172 may be an etching mask during the removal of the portion 162 of the anti-reflection layer 160.
As a result, the width W2 of the anti-reflection layer 160, which has been etched, is enlarged by the formation of the protection layer 180. Therefore, the anti-reflection layer 160, which has been etched, is able to have the desired width W2. The formation of the protection layer 180 prevents the critical dimension (e.g., the width W2) of the anti-reflection layer 160 from undesirable shrinkage. The formation of the protection layer 180 simplifies the design of the photomask used in the photolithography process of FIG. 1B, which reduces the cost of the photomask.
In some embodiments, the sidewalls 164 of the anti-reflection layer 160 are taper sidewalls. Therefore, the width W2 of the anti-reflection layer 160 increases toward the film 150, in accordance with some embodiments. As a result, the width W2 of the anti-reflection layer 160 is greater than the width W1 of the mask layer 170, in accordance with some embodiments. In some embodiments, the greatest width W2 of the anti-reflection layer 160 is greater than the width W1 of the mask layer 170.
The plasma etching and deposition process is performed using a bias power ranging from about 200 W to about 700 W, in accordance with some embodiments. The plasma etching and deposition process is performed at a pressure ranging from about 3 mTorr to about 10 mTorr, in accordance with some embodiments.
If the bias power is less than 200 W and the pressure is greater than 10 mTorr, the protection layer 180 may be not only formed over the sidewalls 164 and 172, but also formed over a top surface 154 of the portion 152, which hinders the removal process for removing the portion 152 of the film 150 performed subsequently. If the bias power is greater than 700 W and/or the pressure is less than 3 mTorr, the protection layer 180 is not formed or only partially-formed.
As shown in FIG. 1D, the portion 152 of the film 150 is removed using the mask layer 170 and the anti-reflection layer 160 as an etching mask, in accordance with some embodiments. In some embodiments, the protection layer 180 is also used as an etching mask during the removal process for removing the portion 152. The removal process includes a dry etching process, in accordance with some embodiments. After the removal process, the film 150 exposes a portion 142 of the gate material layer 140a, in accordance with some embodiments.
After the removal process, since the mask layer 170 and the anti-reflection layer 160 have the desired widths W1 and W2, the film 150 has the desired width W3. In some embodiments, the protection layer 180 enlarges the width W3. The formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2 and W3) of the anti-reflection layer 160 and the film 150 from undesirable shrinkage.
As shown in FIG. 1E, the mask layer 170, the anti-reflection layer 160, and the protection layer 180 are removed, in accordance with some embodiments. The mask layer 170, the anti-reflection layer 160, and the protection layer 180 are removed using a dry etching process, in accordance with some embodiments. As shown in FIG. 1E, the portion 142 of the gate material layer 140a is removed using the film 150 as an etching mask, in accordance with some embodiments.
After the removal process for removing the portion 142, the remaining portion of the gate material layer 140a forms a gate 140, in accordance with some embodiments. The removal process also removes a portion of the gate dielectric layer 130 under the portion 142, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments.
After the removal process, since the film 150 have the desired width W3, the gate 140 has the desired width W4, in accordance with some embodiments. As shown in FIGS. 1D-1E, the formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2, W3, and W4) of the anti-reflection layer 160, the film 150, and the gate 140 from undesirable shrinkage.
As shown in FIG. 1F, a spacer layer 190a is formed over the substrate 110, the isolation structure 120, the gate dielectric layer 130, the gate 140, and the film 150, in accordance with some embodiments. The spacer layer 190a includes an insulating material, such as silicon oxide or silicon nitride. The spacer layer 190a is formed using a chemical vapor deposition process, in accordance with some embodiments.
As shown in FIG. 1G, an anisotropic etching process is performed to remove a portion of the spacer layer 190a, in accordance with some embodiments. The spacer layer 190a remaining over the sidewalls of the gate dielectric layer 130, the gate 140, and the film 150 forms spacers 190, in accordance with some embodiments. The spacers 190 are configured to electrically isolate a gate formed subsequently from other devices and configured to act as a mask layer in a subsequent ion implantation process, in accordance with some embodiments. The anisotropic etching process includes a dry etching process, in accordance with some embodiments.
As shown in FIG. 1H, heavily doped regions 114 are formed in the substrate 110, in accordance with some embodiments. The heavily doped regions 114 are formed using an ion implantation process, in accordance with some embodiments. The ion implantation process is performed to introduce p-type impurities (e.g., boron) or n-type impurities (e.g., phosphorus) into the substrate 110, in accordance with some embodiments.
The heavily doped regions 114 are a heavily doped source region and a heavily doped drain region, in accordance with some embodiments. The heavily doped regions 114 are located at the two opposite sides of the gate 140, in accordance with some embodiments.
If the thickness of the protection layer 180 is greater than the desired thickness, the protection layer 180 may be thinned or removed. The detailed description is exemplary described as follows.
FIGS. 3A-3F are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. After the step of FIG. 1C, as shown in FIG. 3A, the protection layer 180 is removed, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments. After the removal process, the anti-reflection layer 160 exposes a portion 152 of the film 150, in accordance with some embodiments.
As shown in FIG. 3B, the portion 152 of the film 150 is removed using the mask layer 170 and the anti-reflection layer 160 as an etching mask, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments. After the removal process, the film 150 exposes a portion 142 of the gate material layer 140a, in accordance with some embodiments.
After the removal process, since the mask layer 170 and the anti-reflection layer 160 have the desired widths W1 and W2, the film 150 has the desired width W3. As shown in FIGS. 1C and 3A-3B, the formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2 and W3) of the anti-reflection layer 160 and the film 150 from undesirable shrinkage.
As shown in FIG. 3C, the mask layer 170 and the anti-reflection layer 160 are removed, in accordance with some embodiments. The mask layer 170 and the anti-reflection layer 160 are removed using a dry etching process, in accordance with some embodiments. As shown in FIG. 3C, the portion 142 of the gate material layer 140a is removed using the film 150 as an etching mask, in accordance with some embodiments.
After the removal process for removing the portion 142, the remaining portion of the gate material layer 140a forms a gate 140, in accordance with some embodiments. The removal process also removes a portion of the gate dielectric layer 130 under the portion 142, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments.
After the removal process, since the film 150 have the desired width W3, the gate 140 has the desired width W4, in accordance with some embodiments. As shown in FIGS. 1C and 3A-3C, the formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2, W3, and W4) of the anti-reflection layer 160, the film 150, and the gate 140 from undesirable shrinkage.
As shown in FIG. 3D, a spacer layer 190a is formed over the substrate 110, the isolation structure 120, the gate dielectric layer 130, the gate 140, and the film 150, in accordance with some embodiments. The spacer layer 190a includes an insulating material, such as silicon oxide or silicon nitride. The spacer layer 190a is formed using a chemical vapor deposition process, in accordance with some embodiments.
As shown in FIG. 3E, an anisotropic etching process is performed to remove a portion of the spacer layer 190a, in accordance with some embodiments. The spacer layer 190a remaining over the sidewalls of the gate dielectric layer 130, the gate 140, and the film 150 forms spacers 190, in accordance with some embodiments. The spacers 190 are configured to electrically isolate a gate formed subsequently from other devices and configured to act as a mask layer in a subsequent ion implantation process, in accordance with some embodiments. The anisotropic etching process includes a dry etching process, in accordance with some embodiments.
As shown in FIG. 3F, heavily doped regions 114 are formed in the substrate 110, in accordance with some embodiments. The heavily doped regions 114 are formed using an ion implantation process, in accordance with some embodiments. The ion implantation process is performed to introduce p-type impurities (e.g., boron) or n-type impurities (e.g., phosphorus) into the substrate 110, in accordance with some embodiments.
The heavily doped regions 114 are a heavily doped source region and a heavily doped drain region, in accordance with some embodiments. The heavily doped regions 114 are located at the two opposite sides of the gate 140, in accordance with some embodiments.
FIGS. 4A-4G are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. FIG. 5 is a top view of the semiconductor device structure of FIG. 4A, in accordance with some embodiments.
After the step of FIG. 1B, as shown in FIGS. 4A and 5, a plasma etching and deposition process is performed over the anti-reflection layer 160 and the mask layer 170, in accordance with some embodiments. The plasma etching and deposition process thins out the portion 162 of the anti-reflection layer 160 and form a protection layer 180 over sidewalls 172 of the mask layer 170, in accordance with some embodiments.
After the plasma etching and deposition process, the anti-reflection layer 160 has a portion 166 under the mask layer 170, in accordance with some embodiments. The portion 166 protrudes from an upper surface 168 of the portion 162 that is thinned out, in accordance with some embodiments. The portion 166 has sidewalls 164, in accordance with some embodiments.
The protection layer 180 is formed further over the sidewalls 164 of the portion 166, in accordance with some embodiments. The protection layer 180 covers the sidewalls 164 of the portion 166, in accordance with some embodiments. The protection layer 180 includes a polymer material, in accordance with some embodiments. In some embodiments, the protection layer 180 continuously covers the sidewalls 164 and 172. The protection layer 180 surrounds the mask layer 170 and the portion 166, in accordance with some embodiments. The protection layer 180 continuously surrounds the mask layer 170 and the portion 166, in accordance with some embodiments.
In some embodiments, the plasma etching and deposition process uses a processing gas. The processing gas is configured to be an etching gas and a polymer gas, in accordance with some embodiments. The polymer gas is configured to provide a polymer deposition during the plasma etching and deposition process, in accordance with some embodiments.
The processing gas includes CHF3, CH2F2, CH3F, or a combination thereof. The processing gas includes pure CHF3 and unavoidable impurity gas(es), in accordance with some embodiments. The processing gas includes pure CH2F2 and unavoidable impurity gas(es), in accordance with some embodiments. The processing gas includes pure CH3F and unavoidable impurity gas(es), in accordance with some embodiments.
As shown in FIG. 4B, the protection layer 180 and the portion 162 of the mask layer 160 are removed, in accordance with some embodiments. After the removal process, the anti-reflection layer 160 exposes a portion 152 of the film 150, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments.
As shown in FIG. 4C, the portion 152 of the film 150 is removed using the mask layer 170 and the anti-reflection layer 160 as an etching mask, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments. After the removal process, the film 150 exposes a portion 142 of the gate material layer 140a, in accordance with some embodiments.
After the removal process, since the mask layer 170 and the anti-reflection layer 160 have the desired widths W1 and W2, the film 150 has the desired width W3. As shown in FIGS. 4A-4C, the formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2 and W3) of the anti-reflection layer 160 and the film 150 from undesirable shrinkage.
As shown in FIG. 4D, the mask layer 170 and the anti-reflection layer 160 are removed, in accordance with some embodiments. The mask layer 170 and the anti-reflection layer 160 are removed using a dry etching process, in accordance with some embodiments. As shown in FIG. 4D, the portion 142 of the gate material layer 140a is removed using the film 150 as an etching mask, in accordance with some embodiments.
After the removal process for removing the portion 142, the remaining portion of the gate material layer 140a forms a gate 140, in accordance with some embodiments. The removal process also removes a portion of the gate dielectric layer 130 under the portion 142, in accordance with some embodiments. The removal process includes a dry etching process, in accordance with some embodiments.
After the removal process, since the film 150 have the desired width W3, the gate 140 has the desired width W4, in accordance with some embodiments. As shown in FIGS. 4A-4D, the formation of the protection layer 180 prevents the critical dimensions (e.g., the widths W2, W3, and W4) of the anti-reflection layer 160, the film 150, and the gate 140 from undesirable shrinkage.
As shown in FIG. 4E, a spacer layer 190a is formed over the substrate 110, the isolation structure 120, the gate dielectric layer 130, the gate 140, and the film 150, in accordance with some embodiments. The spacer layer 190a includes an insulating material, such as silicon oxide or silicon nitride. The spacer layer 190a is formed using a chemical vapor deposition process, in accordance with some embodiments.
As shown in FIG. 4F, an anisotropic etching process is performed to remove a portion of the spacer layer 190a, in accordance with some embodiments. The spacer layer 190a remaining over the sidewalls of the gate dielectric layer 130, the gate 140, and the film 150 forms spacers 190, in accordance with some embodiments. The spacers 190 are configured to electrically isolate a gate formed subsequently from other devices and configured to act as a mask layer in a subsequent ion implantation process, in accordance with some embodiments. The anisotropic etching process includes a dry etching process, in accordance with some embodiments.
As shown in FIG. 4G, heavily doped regions 114 are formed in the substrate 110, in accordance with some embodiments. The heavily doped regions 114 are formed using an ion implantation process, in accordance with some embodiments. The ion implantation process is performed to introduce p-type impurities (e.g., boron) or n-type impurities (e.g., phosphorus) into the substrate 110, in accordance with some embodiments.
The heavily doped regions 114 are a heavily doped source region and a heavily doped drain region, in accordance with some embodiments. The heavily doped regions 114 are located at the two opposite sides of the gate 140, in accordance with some embodiments.
In accordance with some embodiments, methods for forming semiconductor device structures are provided. The methods (for forming the semiconductor device structure) perform a plasma etching and deposition process to remove a portion of a first mask layer exposed by a second mask layer and to form a protection layer over a sidewall of the second mask layer. The protection layer is able to substantially maintain a critical dimension of the second mask layer during the plasma etching and deposition process. Therefore, the first mask layer, which has been etched, has a desired critical dimension. As a result, the methods improve the process yield.
In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes forming a film over a substrate. The method includes forming a first mask layer over the film. The method includes forming a second mask layer over the first mask layer. The second mask layer exposes a first portion of the first mask layer. The method includes performing a plasma etching and deposition process to remove the first portion of the first mask layer and to form a protection layer over a first sidewall of the second mask layer. The first mask layer exposes a second portion of the film after the plasma etching and deposition process. The method includes removing the second portion using the first mask layer and the second mask layer as an etching mask.
In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes forming a film over a substrate. The method includes forming a first mask layer over the film. The method includes forming a second mask layer over the first mask layer. The second mask layer exposes a first portion of the first mask layer. The method includes performing a plasma etching and deposition process to remove the first portion of the first mask layer and to form a protection layer over a first sidewall of the second mask layer. The first mask layer exposes a second portion of the film after the plasma etching and deposition process. The method includes removing the protection layer. The method includes removing the second portion of the film using the first mask layer and the second mask layer as an etching mask.
In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes forming a film over a substrate. The method includes forming a first mask layer over the film. The method includes forming a second mask layer over the first mask layer. The second mask layer exposes a first portion of the first mask layer. The method includes performing a plasma etching and deposition process to thin out the first portion of the first mask layer and to form a protection layer over a first sidewall of the second mask layer. The method includes removing the protection layer and the first portion of the first mask layer. The first mask layer exposes a second portion of the film after the removal of the first portion of the first mask layer. The method includes removing the second portion of the film using the first mask layer and the second mask layer as an etching mask.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.

## Claims

1. A method for forming a semiconductor device structure, comprising:
forming an insulating film over a substrate;
forming a first mask layer over the insulating film;
forming a second mask layer over the first mask layer;
partially removing the second mask layer to leave a second mask exposing the first mask layer;
performing a plasma etching and deposition process to remove the first mask layer not covered by the second mask so as to leave a first mask and to form a protection layer continuously covering a first sidewall of the second mask and a second sidewall of the first mask, wherein the first mask and the protection layer expose the insulating film; and
etching the insulating film using the first mask, the second mask, and the protection layer as an etching mask.

2. The method for forming a semiconductor device structure as claimed in claim 1, wherein the first mask layer comprises an anti-reflection layer, and the second mask layer comprises a photoresist layer.

3. The method for forming a semiconductor device structure as claimed in claim 1, further comprising:
before the formation of the insulating film, forming a semiconductor layer over the substrate, wherein the insulating film is formed over the semiconductor layer; and
after the etching of the insulating film, removing the semiconductor layer exposed by the insulating film.

4. The method for forming a semiconductor device structure as claimed in claim 1, wherein the second sidewall of the first mask is a taper sidewall.

5. The method for forming a semiconductor device structure as claimed in claim 4, wherein a width of the first mask increases toward the insulating film.

6. The method for forming a semiconductor device structure as claimed in claim 1, wherein the plasma etching and deposition process uses a processing gas comprising CHF3, CH2F2, CH3F, or a combination thereof.

7. The method for forming a semiconductor device structure as claimed in claim 1, wherein the protection layer comprises a polymer material.

8. The method for forming a semiconductor device structure as claimed in claim 1, wherein after the plasma etching and deposition process, a first width of the first mask is greater than a second width of the second mask.

9. The method for forming a semiconductor device structure as claimed in claim 1, wherein the protection layer continuously surrounds the first mask layer and the second mask.

10. A method for forming a semiconductor device structure, comprising:
forming an insulating film over a substrate;
forming a first mask layer over the insulating film;
forming a second mask layer over the first mask layer;
partially removing the second mask layer to leave a second mask exposing the first mask layer;
performing a plasma etching and deposition process to remove the first mask layer not covered by the second mask so as to leave a first mask and to form a protection layer continuously covering a first sidewall of the second mask and a second sidewall of the first mask, wherein the first mask exposes the insulating film;
removing the protection layer; and
etching the insulating film using the first mask and the second mask as an etching mask.

11. The method for forming a semiconductor device structure as claimed in claim 10, wherein the removal of the protection layer comprises:
performing a dry etching process over the protection layer.

12. The method for forming a semiconductor device structure as claimed in claim 10, further comprising:
before the formation of the insulating film, forming a semiconductor layer over the substrate, wherein the insulating film is formed over the semiconductor layer; and
after the etching of the insulating film, removing the semiconductor layer exposed by the insulating film.

13. The method for forming a semiconductor device structure as claimed in claim 10, wherein the plasma etching and deposition process uses a processing gas comprising CHF3, CH2F2, CH3F, or a combination thereof.

14. The method for forming a semiconductor device structure as claimed in claim 10, wherein the protection layer surrounds the second mask.

15. The method for forming a semiconductor device structure as claimed in claim 14, wherein the protection layer further surrounds the first mask.

16. A method for forming a semiconductor device structure, comprising:
forming an insulating film over a substrate;
forming a first mask layer over the insulating film;
forming a second mask layer over the first mask layer;
partially removing the second mask layer to leave a second mask exposing the first mask layer;
performing a plasma etching and deposition process to thin out the first mask layer not covered by the second mask so as to form a thinned portion of the first mask layer and to form a protection layer continuously covering a first sidewall of the second mask and a second sidewall of the first mask layer;
removing the protection layer and the thinned portion of the first mask layer to leave a first mask, wherein the first mask exposes the insulating film; and
etching the insulating film using the first mask and the second mask as an etching mask.

17. The method for forming a semiconductor device structure as claimed in claim 16, wherein the first mask layer further has a third portion under the second mask, and the portion protrudes from an upper surface of the thinned portion.

18. The method for forming a semiconductor device structure as claimed in claim 17, wherein the protection layer covers a third sidewall of the portion.

19. The method for forming a semiconductor device structure as claimed in claim 18, wherein the protection layer surrounds the portion and the second mask.

20. The method for forming a semiconductor device structure as claimed in claim 16, wherein the protection layer comprises a polymer material.