Wafering process

A second area of development that has impacted faciUty design is the trend to single-wafer processing, allowing enhanced control in processing individual wafers. This should carry greater importance as wafer size goes beyond 200-mm diameter to 300—400 mm. 

Reactive Hquid infiltration (45,68,90,93,94) is similar to the CVI process used to make RBSN. Driven by capillarity, a reactive Hquid infiltrates a porous preform and reacts on free surfaces. Reactive Hquid infiltration is used to make reaction bonded siHcon carbide (RBSC), which is used in advanced heat engines and as diffusion furnace components for semiconductor wafer processing. 

EqiJlpment Includes Wafer Processing- Test - Assembly... 

Rothman (52) investigated the planarization of polyimide films over features tens of micrometers in size and separation. Bassous and Pepper (55) studied planarization of PMMA and AZ1350J over features pertinent to Si wafer processing. A mechanical stylus was used to determine the topography of the wafer and the corresponding surface variation of the resist thickness as shown in Figure 29 where a 1.7 - pm thick AZ1350J layer was spun on steps of different space and width combinations. 

The old scrubber technique is in fact very attractive for post-CMP cleaning as the same mechanical effect is active for all the materials present at the surface (insulators, metal barriers). Doubled-sided scrubbers for cleaning the frontside and the backside of the wafer and lateral brushes to take care of the wafer side are now proposed on the market. Furthermore, the implementation of megasonic sprays in the scrubber can sometimes help for difficult cases. The major limitation is in terms of cost of ownership (COO) as a single-wafer process is involved. Indeed according to Witt et al. [17] who used the standard SEMATECH COO model, brush cleaning is more than three times more expensive than wet cleaning, which was confirmed by other economic studies [18]. 

G. Miner, G. Xing, H.S. Joo, E. Sanchez, Y. Yokota, C. Chen, D. Lopes, and A. Bal-akrishna. Enabling Single-Wafer Process Technologies for Reliable Ultra-thin Gate Dielectrics. Electrochem. Soc. Proc., 99(10) 3—13,1999. 

Every wafer processing step is a potential source of contamination, each step with its specific type of contaminant. This means that an efficient cleaning process consists of several cleaning steps in order to remove all contamination from the crystal. 

What is accomplished by adhesion promotion treatments in IC manufacturing should actually be referred to as wafer substrate preparation, and not adhesion. Adhesion in the structural sense, as experienced in airplane composite material parts attachment, is not accomplished by silane wafer processing treatments except for the PI applications discussed early in this paper. The term adhesion, as it is used here, refers to a more practical definition—that is, resist image adhesion. Nevertheless, this type of adhesion is essential to the huge international semiconductor business, and the early silane work of Plueddemann and others was essential to early wafer adhesion process development. 

The sensors do not show any dependence on interferences [77]. They exhibit extended linear ranges with high sensitivities and low residual currents. Due to the wafer processing a high reproducibility can be obtained [77]. 

Due to the high deposition rates possible at atmospheric pressure, approximately 1000 A/mtn, wafer throughput can be as high as 200 to 400 per hour. Also, since this is an atmospheric pressure reactor, there is no expensive vacuum system, and the capital cost of the reactor system is modest. These two facts contribute to a low cost per wafer processed, and has allowed this system to remain in commercial use for over 13 years. 

Obviously, defects can be seen with an optical microscope. What is needed is a quick way to count different types of defects on each wafer processed. For this purpose, a commercial computerized unit has been developed that can distinguish between point, tine and area defects. The measurement and wafer-handling unit is shown in Figure 13. 

The recently developed modified PTFE (e.g., Teflon NXT), because of its improved processing, lower creep, improved permeation, less porosity and better insulation than standard PTFE, finds use in pipe and vessel linings, gaskets and seals, fluid-handling components, wafer processing, and electric and electronic industries. An example of a molded part from modified PTFE is shown in Figure 4.15. 

Modifed PTFE can be used in practically all applications, where the conventional polymer is used. In addition to that, new applications are possible because of its improved flow and overall performance. In the chemical process industry, it is used for equipment linings, seals, gaskets, and other parts, where its improved resistance to creep is an asset. In semiconductor manufacturing, modified PTFE is used in fluid handling components and in wafer processing components. Typical applications in electrical and electronic industries are connectors and capacitor films. Other applications are in unlubricated bearings, laboratory equipment, seal rings for hydraulic systems, and antistick components.103... 

The principal purpose of these experiments is to demonstrate that extremely sharp thresholds in optical transmittance can be obtained from laser photobleaching of a copolymerized absorber. It is not clear that these results can be applied directly to wafer processing conditions. Since the thermal characteristics of the sample are probably quite important in our experiments, the results obtained from a single polymer film on fused silica may not be the same as those found with a multilayer film on silicon. Clearly considerable additional experimentation is necessary before one can consider practical applications. 

FIGURE 3.1 A typical wafer processing flow that shows that CMP is an integral part of the manufacturing process (from Ref. 1). 

The slurry distribution and mixing system operates in the background of the actual wafer processing. However, a slurry with consistent physical and chemical properties is critical for maintaining a repeatable W CMP process with steady yield. Two of the most important parameters to monitor are etchant (oxidizer) and solid (abrasive particle) concentrations. 

Gianchandi YB, Ma KJ, Najafi K. A CMOS dissolved wafer process for integrated P + + microelectromechanical systems. In Proceesings of The 8th International Conference on Solid State Sensors and Actuators 1995. p 79-82. 

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