What is post exposure bake lithography?
What is post exposure bake lithography?
The term “post exposure bake” (PEB) refers to a baking step of the resist film which follows the exposure. Since the resist film is not yet developed, that is to say closed, the PEB can also be applied without diffi culty above the softening temperature of the photoresist.
What are Prebake and Postbake in lithography?
After coating, the resulting resist film will contain between 20 – 40% by weight solvent. The post-apply bake process, also called a softbake or a prebake, involves drying the photoresist after spin coat by removing this excess solvent. The main reason for reducing the solvent content is to stabilize the resist film.
Why is post exposure bake done?
Depending on the resist system post-exposure bakes are performed to reduce standing wave effects or to thermally catalyze chemical reactions amplifying the latent bulk image.
What are the characteristics of exposure tools used in lithography?
In a lithographic exposure tool, there is a glass mask which is fractional covered with chrome to partial expose areas of the resist. Depending on the type of the resist, exposured areas are solubly or insolubly. With a wet-chemical developer the solubly parts are removed, so that a patterned resist layer remains.
What does post bake mean?
Post bake or hardbake, initially used to harden printing plate resists, is the process of applying heat to enhance the performance of a developed resist image. Postbaking involves the thermochemical (thermolysis) reactions of the resin, sensitizer (if present), and residual solvents with heat and air.
How do we develop a wafer from an exposed photoresist?
Creating a pattern with photolithography depends on the photoresist used, but typically involves the following steps:
- Cleaning and dehydrating the substrate.
- Applying adhesion promoter.
- Applying photoresist.
- Soft baking the resist.
- Exposing it to UV light.
- Post-exposure bake (some resists only)
- Resist development.
Why UV light is used in lithography?
Our first lithography systems used this setup to create blue light with a wavelength of 436 nanometers (nm), known as the mercury g-line. They could print features as small as 1 micron (1,000 nm). To enable smaller features, we soon switched to invisible ultraviolet (UV) light with a wavelength of 365 nm.
What is photoresist and mask?
Photoresist is a light-sensitive material which is layered onto a host substrate by spin coating. A pattern mask is then applied to the surface to block light; therefore, only unmasked regions of the photoresist are exposed to light.
What is a post exposure bake?
The term “post exposure bake” (PEB) refers to a baking step of the resist fi lm which follows the exposure. Since the resist fi lm is not yet developed, that is to say closed, the PEB can also be applied without diffi culty above the softening temperature of the photoresist. There are several completely diff erent possible reasons for a PEB that
What are the steps involved in the process of photolithography?
The general sequence of processing steps for a typical photolithography process is as follows: substrate preparation, photoresist spin coat, prebake, exposure, post-exposure bake, development, and postbake. A resist strip is the final operation in the lithographic process, after the resist pattern has been transferred into the underlying layer.
What is soft baking in photoresist?
Soft baking drives off some of the solvent in the photoresist and partially solidifies it, so that it is ready for exposure to UV light. In the LNF, wafers can be baked in the ovens or on hotplates that are located in 1440A and 1440C.
What is the best way to bake photoresist?
There are several methods that can be used to bake photoresists. The most obvious method is an oven bake. Convection oven baking of conventional photoresists at 90°C for 30 minutes was typical during the 1970s and early 1980s.