Pellicle

History

Introduction
	The pellicle is used primarily for two purposes - to increase die yield and reduce overall p handling, i.e. cleaning and inspection. It is a thin film stretched on a frame used to protect a photomask from particle contamination. Today, the pellicle has become an integral component in the manufacturing process for most IC manufacturers and high-resolution projection photolithography systems used in the manufacturing of thin film magnetic reading heads, LCD flat panels, micro electromechanical system (MEMS), etc.
The Use of a Pellicle
	During the printing process the image of any particle on the pellicle film will be out of focus on the wafer plane and therefore has only a blurry shadow which has a minimal effect on the photomask's image on a wafer. Without pellicle protection, a photomask can easily get a particle on its surface and form a distorted image on the wafer, creating a defect on a chip. Before a time when pellicle was used, a photomask would require daily cleaning and inspection. Consequently, the photomask would easily become contaminated from environment or damaged from cleaning process, resulting in a low die yield and high replacement cost. The use of a pellicle in an optical projection system is illustrated below.
	Figure 1: The Use of a Pellicle
	Once a pellicle is properly attached on the photomask, the surface that is covered by the pellicle is free from future outside particle contamination. The original quality of the photomask can therefore be preserved. Now only a brief inspection of the pellicle film and photomask surface is required to insure the quality of the photomask.

ISO 9001-2000 Quality Assurance System:
As a leader in quality with an ISO 9001-2000 certification,
MLI's quality assurance system is governed by 3 principles:

• Customer Satisfaction
• Continuous Improvement
• Quality through Process
  
  

In ensuring a rigid quality control process, each pellicle is assigned a serial number and can be easily traced throughout the entire production process. In addition to effective tracking methods, processes and testing methods that have been refined over years of experience have resulted in top quality pellicle products for nearly two decades.

Born Clean
With a Class 1 cleanroom and years of continuous improvements in manufacturing, MLI has developed a top-rated process for pellicle production. Refinements in automation, process enhancements, cleanroom upgrades, and state-of-the-art manufacturing equipment have resulted in producing pellicles with the utmost cleanliness. In addition, every component of a pellicle (such as the glue, mounting adhesive, frame anodization and coating) has been continuously improved over the years.

Shipped Clean
With a relentless focus on cleanliness, MLI has incorporated the continuous improvement of packing and handling techniques into its daily operations along with a rigorous quality control process. Preventing particle contamination with proper shipping and handling procedures are crucial steps in preserving the integrity and cleanliness of pellicles received by customers. MLI's patented pellicle package designed with an interior adhesive coating captures and holds any loose particles generated during shipping. The inside of the pellicle is also sealed with an adhesive coating to better prevent particle contamination. In addition, MLI has developed a simple packaging and mounting system that eliminates hand contact with the pellicle during the handling and mounting process.

Stays Clean
To ensure that MLI pellicles stay clean, a fluoro-polymer anti-reflective coating (FP ARC) is used during the production process. With low surface energy, the coating not only improves transmission but also allows particles to be easily blown off the pellicle membrane.