Seung-ki Chae

Sizing Accuracy, Counting Efficiency, Lower Detection Limit and Repeatability of a Wafer Surface Scanner for Ideal and Real‐World Particles

The performance characteristics of a Tencor Surfscan 4000 wafer surface scanner have been evaluated using ideal polystyrene latex (PSL) spheres and irregularly shaped real-world particles of Si and SiO 2 . The particles were uniform in size and were deposited on bare silicon wafers and used as standard calibration wafers to study the scanner response. Particles in the 0.1 to 1.0 μm diam range were used. The sizing accuracy, counting efficiency, lower detection limit, and count repeatability of the scanner were studied systematically. The full Maxwells electromagnetic equations also have been solved numerically on a supercomputer to obtain the light-scattering cross section of the particles on bare silicon wafers

Changes in vertical PAG distribution inside photoresist due to the variation of concentration

Vertical distribution of photo acid generator (PAG) inside CA-type photoresist is inferred from X-ray reflectivity (XRR) analysis which gives the information on the vertical electron density profile of thin film. The difference between the density distribution of normal photoresist and pure resin indicates the approximate distribution of PAG. The electron density profile of each film is obtained by fitting method for the XRR results based on distorted wave Born approximation (DWBA) approach. In this study, trends in density distributions varied by concentration of PAG suggest that the inhomogeneous distributions of PAG near the surface or interface of photoresist film occurs due to interactions between PAG molecules and substrate, or polymer resin. Distributions with low concentration of PAG (2 wt%) show that the PAG molecules tend to be concentrated near the surface of photoresist, while over-load of PAG (20 wt%) results in the density increase near the interface region.

Nonoxidative Aqueous Cleaning Solutions for Tungsten Layers

Aqueous cleaning solutions were developed for postetch cleaning of tungsten layers to replace the amine-based organic strippers. They are composed of tetramethylammonium hydroxide, HF, and two additives. Even the cleaning recipes without a strong oxidant, such as hydrogen peroxide, could remove postetch residues formed by reactive ion etching and they also had the same particle removal efficiency compared to ammonium and hydrogen peroxide mixture known as RCA Standard Clean. The concentration of metal ion on the wafer surface after cleaning by them was under 1010 atoms/cm 2 . The effects of the cleaning could be explained by applying Pans double-layer model [J. Electrochem. Soc., 148, G315 (2001)]. In fact, these cleaning solutions made it possible to decrease the resistances of tungsten bit lines and metal contacts and contributed to yield enhancement.

The Novel Highly-Selective Etching Process of SiO2 to TiSix for Nano-Scale Device Fabrication

Among various methods to embody the corresponding contact area for a required contact resistance, it is a common and widely used way to enlarge the contact by the treatment of HF-based silicon oxide etchant after contact patterning followed by dry etching. Although the wet etch process is very helpful to enhance the process margin, an unexpected failure could take place as the feature size decreases to less than 80nm, especially with 6F2 cell design, where little lithographic margin between contact exists. As shown in Fig. 1, when TiSix interfaced with contact pad underlying bit-line is disclosed to HF-based solution during contact enlarging process, it is etched easily by this solution, which results in the significant increase of contact resistance.

Real-time detection of resist strip failure at metal etch process equipment

Metal etch process is to form the electrical metal lines of device on a wafer. DPS of AMAT, the one of metal etch process equipments, is assembled chambers for metal etch process and resist strip process. The wafer proceeds metal etch process and resist strip process continuously. If resist were not removed clearly in the strip process chamber, its ash induces serious defect to metal lines. Despite such a failure has been randomly occurred in resist strip chamber, real-time detection of it was impossible under interlock system by using classical SPC. This paper shows how it is possible to detect resist strip failure in real-time by modeling. As a result, wafer loss by resist ash could be decreased effectively in the metal etch process.

Throughput analysis and productivity enhancement for CVD equipment

A method for throughput analysis and productivity enhancement of FAB equipment is introduced in this paper. The simultaneous movement of the wafers in the equipment was observed from the graph that was generated based on the wafer history log or the event log of the equipment. The efficiency of the equipment and the productivity of the cluster tool were analyzed based on the tables and the graph. It was verified from the analysis that the equipment was in the transfer bottleneck or the process bottleneck condition. If the equipment was in the transfer bottleneck, actions for the productivity enhancement of the equipment were carried out in transfer viewpoint. Or, if the equipment was in the process bottleneck, the actions were carried out in process viewpoint. Some examples of the throughput analysis and the productivity enhancement for the CVD equipment were shown.

Study of heavy metal contamination from dry etching process and its effects on subsequent wet processing

Summary form only given. Dry etching process can cause a significant level of heavy metal contamination on process wafers, and the degree is dependent on the type of dry etcher. Most of these contaminants are removed through subsequent wet cleaning processes, but Cu seems to remain on the wafer surface. The effect of these contaminants on process wafers as well as chemical baths including filters will be discussed.