James L. Speidell

Ion beam oxidation

We describe a new technique for controlled oxide growth using a directed low‐energy ion beam. The technique is evaluated by fabricating Ni‐oxide‐Ni and Cr‐oxide‐Ni tunneling junctions, using oxygen ion beams with energies ranging from 30 to 180 eV. High ion current densities are achieved at these low energies by replacing the conventional dual grid extraction system of the ion source with a single fine mesh grid. Junction resistance decreases with increasing ion energy, and oxidation time dependence shows a characteristic saturation, both consistent with a process of simultaneous oxidation and sputter etching, as in the rf oxidation process. In contrast with rf oxidized junctions, however, ion beam oxidized junctions contain less contamination by backsputtering, and the quantitative nature of ion beam techniques allows greater control over the growth process.

Active-matrix display using ion-beam-processed polyimide film for liquid crystal alignment

Ion-beam bombardment was developed as a substitute for mechanical rubbing of polyimide film as a noncontact liquid crystal (LC) alignment technique. The ion-beam technique was applied to a high-resolution thin-film-transistor-addressed liquid crystal display (TFT/LCD) panel. The results showed that LC alignment was achieved and that the display is capable of showing high-quality images.

Masks for laser ablation technology: new requirements and challenges

Laser ablation is used as a dry patterning process in which an intense beam of light from an excimer laser is used to pattern a material directly. This process has found extensive application in the microelectronics industry for patterning of polymer materials. A typical laser ablation tool is very similar to a conventional optical lithography projection tool; the primary difference is the wavelength and the intensity of the light used in the ablation process. Conventional chromium-coated quartz masks are incompatible with 1 x laser ablation tools because the chromium layer is rapidly damaged. This paper discusses a mask technology which has been developed specifically for excimer laser ablation. The mask consists of a quartz substrate with a stack of dielectric films which have been selected for the laser ablation wavelength. Mask fabrication is accomplished with standard microelectronic processes and equipment. Such masks have been used in IBM manufacturing since 1987 and have met all process specifications such as resolution, defect density, and damage resistance.

Lithographically fabricated fiber guides for optical subassemblies

A new optoelectronic packaging technology is presented which permits highly accurate fiber-to-chip alignment at low cost. Instead of the more common methods employed in fabricating optical subassemblies, which use leadframe, precision plastic-molding, or silicon-optical-bench technology, here fiber guides are fabricated in a photoresist by use of standard photolithographic procedures. By this means the fiber guides are directly created on an entire wafer of either VCSELs or receivers, resulting in structures with very tight dimensional tolerances fabricated at very low cost. After dicing, a fiber is interfaced with a chip under computer control using a very simple semiautomatic tool to insert the fiber into the fiber guide. This new technology may be used in the fabrication of a wide variety of single or multi-channel optoelectronic transceivers.

Improved excimer laser pattern generator for photomask fabrication

This paper describes a laser pattern generator constructed by modifying a GCA 3600F tool for the production of research photomasks. The mercury arc lamp illumination source was replaced with an excimer laser. Extensive modifications made to the subsystems and software are described. The result is a tool with a 25X average throughput improvement, a resolution of 1.0 micrometers , and an 8X increase in overlay precision. The laser pattern generator retains the ease of operation of the original system and exhibits improved reliability. The overall cost of the implemented improvements is a small percentage of a state-of-the-art laser or electron beam mask generation tool. We report on the results of generating 2X, 5X and 10X reticles as well as 1X photomasks from the past three years.

Quality assurance of dielectric masks for laser ablation technology

Dielectric masks are one of several types of masks used for high energy excimer laser ablation. Excimer laser ablation is a process used to directly pattern materials without the use of resists or wet processing. The dielectric masks are formed from a multilayer stack of dielectric films deposited on a quartz substrate. These masks have low reflectivity in visible light, and the dielectric stack thickness ranges from 0.4 micrometer to 1.0 micrometer to achieve an optimum reflectivity for a specific application. These properties present the most significant challenges in the inspection and quality assurance of dielectric masks. This paper discusses the methods of critical dimension measurement and defect inspection that have been developed for dielectric laser ablation masks. Printability of defects and the application of a unique scanning inspection tool which uses ultraviolet light are discussed. Manufacturing performance data also are presented.

Mask technology for excimer laser projection ablation

Excimer laser projection ablation is a dry, precise patterning process in which an intense beam of ultraviolet light from an excimer laser is used to directly pattern a material. This technique has been used in industrial applications for patterning both organic and inorganic materials. In the manufacturing of microelectronics devices, laser ablation is used extensively to pattern insulating layers in the multi- level thin film packages. Excimer laser projection ablation is very similar to optical projection lithography, both using a photomask or reticle which contains a master pattern. The mask used in a 1X projection laser ablation tool, however, must withstand significantly higher energy densities than conventional photolithographic masks. A number of mask technologies have been developed specifically for 1X excimer laser projection ablation. These masks include dielectric layers on quartz masks, thick films of aluminum on quartz masks, binary phase shifted grating masks and holographic masks. This paper presents a review of these mask types. Critical issues such as fabrication processes, advantages and disadvantages, cost and availability of each mask are discussed.

Data-processing improvements for photomask pattern generators

The performance of optical pattern generators as well as other lithographic tools was often limited by the performance of the data processing equipment and software used to control these tools. In fact, many performance attributes of modern pattern generators is due to the power and flexibility of the modern computers and software. For example, imperfections in the stage travel due to the mechanical components are often mapped out and corrected for in the control software. When key components are upgraded, these older tools regain useful life, at relatively low cost, for research and development and certain production applications. This paper describes modifications which have been made to a GCA 3600F pattern generator resulting in improved performance in key categories such as reliability and throughput. The modifications have been done to the operating system, data storage subsystem, job creation and monitoring system. Also, a generator has been constructed to simplify production of photomasks consisting primarily of regular arrayed patterns.

Low-cost mask for excimer laser projection ablation

Excimer laser projection ablation is a dry patterning process in which an intense beam of ultraviolet light from an excimer laser is used to directly pattern a material. This technique has been used extensively in the microelectronics industry for patterning both organic and inorganic materials. Excimer laser projection ablation requires the use of a mask which is similar to a conventional 1X photomask. The laser ablation mask must withstand significantly higher energy densities than conventional photolithographic masks. A dielectric mask structure which consists of a quartz substrate coated with a stack of dielectric thin films has been developed for this process. Although the dielectric mask has been used successfully in a manufacturing environment, it suffers from the disadvantages of a complex fabrication process and high cost. Alternatives to the dielectric mask have been explored and a new mask has been developed which consists of an aluminum film on a quartz substrate. This mask meets the requirements for the laser ablation process and has the advantage of a low cost fabrication process which is similar to conventional chrome on quartz photomasks. The mask development, specifications, fabrication and results are discussed.