Contamination control

Abstract: The transport and behavior of particulates during plasma processing is imaged in real time using rastered laser light scattering combined with video detection. Results show the distribution of particles is highly ordered and predictable. Two effects have major influence on the distribution and location of particles: feed gas drag and electrostatic traps. Particle traps form from plasma disturbances and design properties of the electrode and the tooling. These results are confirmed in normal plasma conditions used in microelectronics fabrication. A strategy is presented for plasma contamination control. Complete elimination of trapping effects is not feasible. Instead, process techniques are used to minimize or defeat the attractive nature of the traps. Several examples are discussed.

Abstract: Contamination levels in plasma processes are reduced during plasma processing, by prevention of formation of particles, by preventing entry of particles externally introduced or by removing particles spontaneously formed from chemical and/or mechanical sources. Some techniques for prevention of formation of particles include interrup­tion of the plasma by pulsing the source of plasma energy periodically, or application of energy to provide mechani­cal agitation such as mechanical shockwaves, acoustic stress, ultrasonic stress, vibrational stress, thermal stress, and pressure stress. Following a period of ap­plied stress, a tool is pumped out (if a plasma is used, the glow is first discontinued), vented, opened and flaked or particulate material is cleaned from the lower elec­trode and other surfaces. A burst of filtered air or nitrogen, or a vacuum cleaner is used for removal of deposition debris while the vented tool is open. Follow­ing this procedure, the tool is then be used.for product runs. Alternatively, improvement of semiconductor process yields can be achieved by addition of reagents to getter chemical precursors of contamination particulates and by filtration of particulates from feedgas before plasma processing. The efficiency and endpoint for the applied stress are determined, by laser light scattering, using a pulsed or continuous laser source, e.g. a HeNe laser.

Abstract: Overview. Part 1 Introduction to integrated circuit manufacturing processes: front-end IC fabrication operations back-end fabrication operations in-line process monitors and test structures. Part 2 Impact of new technologies: circuit design trends changing fabrication techniques packaging technology trends electrical testing of VLSICs and ASICs. Part 3 Contamination and manufacturing errors: contamination human contamination (people) IC processing contamination contamination control computer-based sources of error in design and test circuit design material issues. Part 4 Causes (sources) of IC failures: fabrication-related causes of defects packaging and assembly related causes of IC failures reliability improvement. Part 5 Introduction to screening: screening.

Abstract: Thermal control surfaces, solar arrays, and optical devices may be adversely affected by a small quantity of molecular and/or particulate contamination. What is rarely discussed is how one: (1) quantifies the level of contamination that must be maintained in order for the system to function properly, and (2) enforces contamination control to ensure compliance with requirements. This document is designed to address these specific issues and is intended to serve as a handbook on contamination control for the reader, illustrating process and methodology while providing direction to more detailed references when needed. The effects of molecular contamination on reflecting and transmitting surfaces are examined and quantified in accordance with MIL STD 1246C. The generation, transportation, and deposition of molecular contamination is reviewed and specific examples are worked to illustrate the process a design engineer can use to estimate end of life cleanliness levels required by solar arrays, thermal control surfaces, and optical surfaces. A similar process is used to describe the effect of particulate contamination as related to percent area coverage (PAC) and bi-directional reflectance distribution function (BRDF). Relationships between PAC and surface cleanliness, which include the effects of submicron sized particles, are developed and BRDF is related to specific sensor design parameters such as Point Source Transmittance (PST). The pros and cons of various methods of preventing, monitoring, and cleaning surfaces are examined and discussed.