1. Technical Field
This disclosure relates to semiconductor fabrication and more particularly, to a method for applying and removing an inorganic anti-reflection coating for semiconductors.
2. Description of the Related Art
Anti-reflection coatings (ARCs) are typically deposited in semiconductor fabrication prior to the deposition of a resist material. ARC coatings absorb radiation to form an optical opaque film which enhances the optical contrast of the imaging resist. ARC coatings effectively reduce reflection (anti-reflection) of the incident radiation back into the overlying resist layer. This prevents overexposure of the resist material.
Dielectric anti-reflection coatings (DARCs) have become more attractive for deep ultraviolet (DUV) lithographic ARC applications. It may be desirable for DARCs to replace organic ARC processes in semiconductor industry depending on the application of the coating. DARC processes have many advantages over organic ARC processes. Both the thickness and the chemical composition of the DARC can be optimized to minimize optical reflections from an underlying film stack to provide lithographic control of feature sizes. DARC can provide higher dry etch selectivity to DUV resist in mask open processes for at least two reasons. One, the DARC layer may be substantially thinner than organic ARC. Second, the etch selectivity of DARC to resist can be optimized to be greater than one, whereas organic ARC selectivity to resists is usually limited to less than or equal to one. Additionally, since the DARC thickness can be precisely controlled, DARC, DARC have the potential for better critical dimension control during the ARC open processes.
However, DARC is not usable for some applications because it is difficult to remove DARC after a lithographic process. DARC is more difficult to remove relative to removing an organic ARC or a resist. For example, when DARC is used on the top of a silicon nitride layer such as for processing at an active area (AA) level of a semiconductor device, it is extremely difficult to eliminate DARC without nitride loss because DARC is very similar to nitride in terms of its chemical composition.
Organic ARC layers tend to be thick since they are etched at about a same rate as the resist layer deposited thereon. Typically, organic ARC layers tend to be about 900 xcex94 to about 1100 xcex94 in thickness. This thickness is not desirable since the thickness may adversely affect dimension control for patterning structures in the semiconductor device.
Therefore, a need exists for a for a method for forming a DARC layer and removing the DARC layer in semiconductor fabrication processes. A further need exists for a thinner anti-reflection layer with higher selectivity to resist.
In accordance with the present invention, a method for employing and removing inorganic anti-reflection coatings, includes the steps of providing a first dielectric layer on a semiconductor device structure to be processed, the first dielectric layer being selectively removable relative to the semiconductor device structure, and forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer, the DARC being selectively removable relative to the first dielectric layer. A resist layer is patterned on the DARC. The resist is selectively removable relative to the DARC. The semiconductor device structure is etched, and the resist layer, the DARC and the first dielectric layer are selectively removed.
A method for etching an active area, in accordance with the invention includes providing a substrate having deep trenches formed therein and a pad stack formed thereon, the trenches including storage nodes and buried straps formed in the trenches. A first dielectric layer is provided on the pad stack, on sidewalls of the trenches and over the buried straps. The first dielectric layer is selectively removable relative to the pad stack, the sidewalls of the trenches and the buried straps. An inorganic dielectric anti-reflection coating (DARC) is formed on the first dielectric layer. The DARC is selectively removable relative to the first dielectric layer. A resist layer is patterned on the DARC, and the resist is selectively removable relative to the DARC. Positions are etched for shallow trench isolation regions in accordance with the patterned resist layer. The resist layer, the DARC and the first dielectric layer are selectively removed.
In other methods, the step of providing a first dielectric layer may include the step of forming a conformal first dielectric layer. The method may include the step of forming an overhang structure with the first dielectric layer to prevent at least some coverage of vertical surfaces by the DARC. The first dielectric layer may include a silicon oxide or a polymer. The step of forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer may include the step of forming the DARC including a silicon oxynitride. The step of forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer may include the step of annealing the DARC to prevent interactions between the resist layer and the DARC. The step of forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer may also include the step of depositing the DARC by one of a chemical vapor deposition process and a physical vapor deposition process. The method may include the step of forming a second dielectric layer on the DARC, the second dielectric layer being selectively removable relative to the DARC.
A method for employing inorganic anti-reflection coatings, in accordance with the present invention, includes providing a first dielectric layer on a semiconductor device structure to be processed, the first dielectric layer being selectively removable relative to the semiconductor device structure, and forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer, the DARC being selectively removable relative to the first dielectric layer. A resist layer is patterned on the DARC, the resist being selectively removable relative to the DARC. A portion of the DARC and the first dielectric layer are etched in accordance with resist layer. The resist layer is selectively removed with respect to the DARC, and the semiconductor device structure is etched by employing the DARC as a hard mask.
In other methods, the step of selectively removing the DARC and the first dielectric layer is included. The step of etching the semiconductor device structure by employing the DARC as a hard mask may include the step of consuming the DARC during the etching of the semiconductor device structure. The first dielectric layer may include a silicon oxide. The step of forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer may include the step of annealing the DARC to prevent interactions between the resist layer and the DARC. The step of forming an inorganic dielectric anti-reflection coating (DARC) on the first dielectric layer may include the step of forming the DARC with silicon oxynitride.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.