Leon I. Maissel

Hardware design and description languages in IBM

Hardware design languages (HDLs) allow computer hardware to be described in sufficient detail to be simulated and built, such a description being at a sufficiently high level of abstraction to make the complete design readily intelligible to anyone skilled in that language. A number of HDLs have been developed and are in use in IBM. To date, no overwhelming case can be made for choosing any one HDL over the others. The major trends in HDL are discussed. Several examples of HDLs are presented in some detail. VHDL, the yet-to-be released HDL which is to serve as a front end to the U. S. Governments Very High Speed Integrated Circuits program, is among these.

Sputter-etching of heterogeneous surfaces

In conventional sputter etching, heterogeneous surfaces are eroded at generally unpredictable rates. The reasons for this are discussed and a solution to the problem is given: Based on control of redeposition, the technique involves the use of a device called a “catcher,” which is placed near the target of the sputtering chamber to trap re-emitted particles. Experiments are described which confirm the effectiveness of the approach. Introduction The technique of rf sputter-etching[ 11 is now widely used. Its chief attraction is that it will cause the erosion of materials without regard to whether they are insulating or conducting. The rf sputter-etch rates for a wide range of different materials are relatively close (within a factor of 10) so that many of the restrictions associated with chemical etching are not apparent. Furthermore, the sharpness of the edge that is eroded away is limited only by the sharpness of the mask since no undercutting can take place. Masks of several conventional photoresist materials have been successfully used for this purpose. To implement the technique, the substrate that is to be sputter-etched is made a part of the target of an rf sputtering system. Then, when the rf glow discharge is initiated, the entire target (including the substrate assembly) is eroded away at some rate dependent on a number of parameters such as rf power, gas pressure, etc. Most workers have found that it is good practice to make the body that is to be etched and the target on which it is placed of the same material, if possible, and relative rates for the sputter-etching of various materials have been measured [ 1 ] for such an arrangement. Several workers have noted that when the surface to be sputter-etched consists of more than one material, particularly if each has a markedly different sputtering rate, the resultant rate for the erosion of the entire surface cannot be readily predicted [2]. Thus, to construct a hypothetical situation, if material A is known to sputter at a different rate from material B, and a pattern is prepared that consists of alternating lines of A and B, it will be found that neither A nor B etches at the relative rates determined using surfaces of pure A and pure B. Further investigation would show that the actual rates observed depend on the type of pattern used as well as on the various puttering parameters employed. The purpose of this paper is to present an explanation of this phenomenon and to indicate how it can be avoided. Discussion It is now firmly established that during rf sputtering a significant fraction of the deposited material is re-emitted during the entire sputtering cycle[3]. The exact amount of this re-emission is a complex function of the relative areas of the target, the substrate assembly, and the chamber walls as well as of the rf and dc coupling between these respective surfaces[4]. This re-emission can have several causes, the principal ones being: 1 ) Resputtering of the deposited material as the result of bombardment by energetic ions from the discharge[4]; 2) resputtering due to bombardment by energetic neutrals present in the sputtering gas [ 3 51 ; 3) resputtering due to energetic negative ions which originate at the target surface and are accelerated across the Crookes dark space[4]; and 4) thermal re-emission [ 61. It has been found that even if re-emission due to mechanism 1 is largely eliminated (by seeing to it that no significant potential difference exists between the depositing film and the rf plasma), re-emission due to the other three causes is still generally around 30%[3]. Thus, in any rf sputter-etching system, it is possible that as much as 30% 67 JANUARY 1972 SPUTTER-ETCHING Figure 1 Sketch of the catcher. The backside is a flat plate. Figure 2 Sketch of sputtering chamber showing position and relative size of catcher.

Sputtered SiO2 deposited over a step

Abstract Measurements have been made of the thickness distribution and etch rate of sputtered SiO2 films in the vicinity of steps of various heights and of various materials. Thickness distribution near a step can be calculated approximately, and deviations from the calculated values are related to the re-emission coefficient of SiO2 as influenced by sputtering parameters. The etch rate of the film near the step is influenced by the material that composed the step, and it is shown that material from the step is incorporated in the film.

Interactive Design Language: A Unified Approach to Hardware Simulation, Synthesis and Documentation

IDL is a hardware design language in use in the VLSI environment. It incorporates a significant number of high-level features such as groups, subroutines, and labels and is particularly well adapted to dealing with parallelism at the hardware level. In addition to being human intelligible (and therefore appropriate as a documentation medium), IDL code can be used to generate 2-level logic which, under the IDL system, can be manipulated in a number of ways, including product term factoring and minimization, feedback minimization, partitioning, merging, and verification. The IDL system contains several simulators that are driven by IDL code. The most common embodiment of IDL output in hardware is a PLA.