Patent Application
20140120476
1. Field of the Invention
The present invention relates to a method of forming a photoresist pattern.
2. Description of the Prior Art
The use of 193 nm immersion lithography is considered a solution for future device nodes in the semiconductor industry. One important issue of immersion lithography is pattern defect control. The fall-on defect becomes worse after the exposure step, in which for example, an immersion hood (IH) with an immersion media is utilized. Thus, the dirty issue is enhanced. It is difficult to remove fall-on particles, and especially sticky particles, in track side only through development with rinse material after post-exposure bake (PEB). Once the fall-on particle with a significant size remains on the developed patterned photoresist layer, for example, the particle size is greater than the line width of the patterned photoresist layer or the particle is stuck on the sidewall of the patterned photoresist layer, it results in a poor resolution for patterning the layer beneath the patterned photoresist layer.
Accordingly, a novel process of lithography is still needed for more efficiently solving the fall on defect issues.
One objective of the present invention is to provide a method of forming a photoresist pattern, in which, contaminants in track side, from previous processes or from an immersion hood can be reduced or removed.
According to an embodiment of the present invention, a method of forming a photoresist pattern includes steps as follows. A substrate is coated with a photoresist layer. An immersion exposure process is performed on the photoresist layer to expose the photoresist layer. The photoresist layer is rinsed with a surfactant after the immersion exposure process is performed. The photoresist layer is post-exposure baked after the photoresist layer is rinsed with the surfactant.
In the method according to an embodiment of the present invention, the photoresist layer is rinsed with a surfactant between a step of performing an immersion exposure process and a step of post-exposure baking, so as to efficiently remove or minimize contaminants such as fall-on particles including water droplet residue generated from, for example, an immersion hood, or polymer from for example wafer edge exposure (WEE) or edge bead removal (EBR) process.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Referring to
Next, Step 102, performing an immersion exposure process on the photoresist layer to expose the photoresist layer, is performed. Specifically, an immersion exposure process may be performed through movement of an immersion lens with an immersion hood together with respect to the photoresist layer to expose the photoresist layer, and an immersion media such as water, but not limited thereto, is disposed between the photoresist layer and the immersion lens with the immersion hood together.
After the immersion exposure process is performed, the fall-on particle 20 may remain on the photoresist layer, and a residue of the immersion liquid may remain, too. Step 103 is performed to rinse the photoresist layer with a surfactant. As shown in
The fall-on particle 20 is not particularly limited and it may be a pollutant from the environment where the substrate is in, or it may be from a dirty immersion hood used in the immersion exposure process. The fall-on particle 20 may become stickier after it is immersed in or swelled by the immersion liquid, especially when it is a polymer particle.
The surfactant suitable for use in the present invention may include a chemical, which may a hydrocarbon or a fluorochemical, containing both hydrophobic group and hydrophilic group. Among these, the surfactant may include an ionic or non-ionic surfactant. The ionic surfactant may include anionic surfactant, cationic surfactant or amphoteric surfactant. The surfactant may be usually used in a form of solution, such as a water solution, but not limited thereto. The surfactant can be appropriately selected according to the properties of the fall-on particles and immersion liquid and photoresist layer employed in the method. Some of the properties may be for example adhesion of the fall-on particle to the photoresist layer and the contact angle of the immersion liquid with respect to the photoresist layer. AZ® FIRM™ solution, commercially available from AZ Electronic Materials Taiwan Co., Ltd., Hu Kou Township, Hsinchu County, Taiwan R.O.C., is one of preferred solutions of surfactant.
Thereafter, Step 104 is performed to post-exposure bake the photoresist layer, so as to remove residual solvent in the resist layer and to reduce standing waves. The post-exposure bake may be performed according to a conventional technology.
One or more additional steps as those can be performed in conventional lithography technology can be performed optionally in addition to the main steps described above. Please refer to the flow chart shown in
The embodiment described above relates to a photolithography process without forming a top-coat on the photoresist layer, which process may be referred to as a NTC PR process (non-top coat photoresist process). In conventional NTC PR processes, fall-on defect can be aggravated by the immersion hood with the immersion media together. By using the method of forming a photoresist pattern according to the present invention, such fall-on defect can be well minimized or avoided.
The method of forming a photoresist pattern according to another embodiment of the present invention may be also applicable to a TC PR process (top coat photo-resist process), for example, as illustrated by
The method of forming a photoresist pattern according to the present invention may be also applicable to those using an exposure process not limited to the immersion exposure process.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
