Redeposition Effect Research Articles

A gap reduction technique for obtaining submicron geometries utilizing redeposition effect

A simple technique for obtaining submicron gap patterns is described. The technique utilizes the redeposition effect in ion-beam etching. Gap widths are controlled by the thickness of the sublayer deposited on the target layer. A 0.3 μm gap width is obtained from a 0.8 μm initial photoresist gap pattern using a 0.7 μm thick sublayer. This technique is applied to the fabrications of photomasks and permalloy patterns for bubble memory. It has been confirmed that a 0.5 μm gap structure is easily obtained by this technique using conventional photolithography with 1 μm minimum feature size.

イオンビームエッチングにおける再付着効果のシミュレーション

Redeposition effect is one of the most important factors in determining profiles of fine patterns delinated by ionbeam etching. A three-dimensional simulation of pattern profiles based on the redeposition effect was carried out, first, using revolution ellipsoids as angular distributions of sputtered atoms, and secondly, using experimentally obtained distributions. Consequently, pattern width difference between mask and substrate decreases as the angular distribution changes from undercosine to overcosine. The pattern width difference, which gives a maximum value the bottom of etched patterns, is almost independent of pattern gap width. Pattern sidewalls become steeper with increasing gap width or with decreasing etched depth. The simulated pattern profiles are in good agreement with the experimental results.

イオンエッチングによる微細パターン形成

Ion-beam etched pattern profiles for several kinds of substrate materials have been investigated, using a Kaufman type ion source at an accelerating voltage of 500 V and a current density of 0.5 mA/cm2. A photoresist stripe pattern with a 2.5 μm width is used as an etching mask. SEM observation of etched substrate surfaces reveals that the substrate pattern profile can be characterized by pattern edge angle, pattern width difference between substrate and mask, and wall height of redeposition. These values depend not only on resist thickness or etching time but also on the substrate materials. The dependence of pattern profiles on substrate materials results from the change in the resist etching rate at pattern edge due to the redeposition effect of substrate materials. The effect can be interpreted by analyzing a simple model. The analysis leads to the determination of the optimum resist thickness for high resolution pattern fabrications.

Ion Beam Etching of Silicon Dioxide on Silicon

An argon ion beam, 7.5 cm in diameter, with an energy of 0.6 keV and a current density of 0.5 mA/cm−2 is generated in an ion beam etching system using a Kaufman‐type ion source (1), then neutralized by electrons. The principles of ion beam etching are outlined and SEM micrographs of ion etched grooves in thermally grown layers are shown. Grooves 1 μm wide and 0.4 μm deep were obtained using Shipley AZ 1350 H photoresist. The groove profiles are in good agreement with those predicted with the aid of an ion etching model. The slope angle of the sidewalls of the grooves is typically 65°. Redeposition effects reduce the effective ion etch rates for grooves of small linewidths. If the layer is ion etched down to the silicon substrate, a silicon surface layer of about 100Å thickness will be damaged. This damage can be completely removed by wet chemical etching. The enhanced etch rate of ion‐damaged surface layers in buffered hydrofluoric acid is used to taper steps in thermally grown in a controllable process.

Low-voltage triode sputtering with a confined plasma: Part V—Application to backsputter definition

The concept of backsputter or ion-etch pattern definition is considered. This includes a discussion of ion sources and basic problems encountered in this type of definition. Two types of ion bombardmant are considered which include conventional sputtering systems and ion guns. Five major problem areas in backsputter definition are considered: (i) relative removal rates of mask and pattern films; (ii) secondary mask defects; (iii) redeposition effects; (iv) substrate temperature; and (v) radiation damage. The principles of backsputter definition are then developed. This includes a discussion of sputter yield vs angle of incidence, forward ion scattering effects which result in the trenching phenomenon, redeposition effects, and reactive backsputtering. It was concluded from this analysis that an ion-beam approach with substrate tilt and rotation relative to the ion beam is the optimum configuration for backsputter definition. The design of a low-voltage triode backsputtering system (LVBS) is discussed which is capable of generating low- energy (∠200 eV), high-current-density (1–5 mA/cm2), and large-diameter [in excess of 12 in. (30.48 cm)] ion beams. This system eliminates many of the usual problems associated with conventional sputtering systems and is readily adapted to large-scale manufacturing requirements. A characterization of the system is presented which includes measurements of: (i) plasma and beam properties; (ii) substrate temperatures as a function of beam potential and current density; (iii) film removal rates; (iv) application to pattern definition; and (v) application to device processing.

Principles of performance testing of laundry detergents

SummaryLaboratory performance tests for laundry detergents can fill important needs in laboratory development programs and in control testing, in which cases full scale practical testing is inapplicable. It has been found to be unnecessary and undesirable to attempt close simulation of practice conditions. In order to be most useful to the experimental investigator or the manufacturer of detergents the soil removal and whiteness retention properties should be measured by separate tests.A soil removal test has been devised in which the soil, which consists essentially of carbon black, is applied to the test fabric from aqueous medium. Soiling from aqueous medium has advantages with respect to reproducibility in tenacity and in variation and susceptibility to removal by detergents having different degrees of effectiveness. The quantity of soil removed is measured directly by means of light transmission measurements on the soiled detergent solution. This eliminates uncertainties and limitations inherent in the reflectance method and permits the use of high soil loads in the test cloth, which minimizes redeposition effects. Multiple wash tests are not required.The whiteness retention property is determined by agitating unsoiled swatches in the detergent solution containing carbon black dispersion and measuring the reflectance change of the swatches.The results of both tests are expressed in relative terms, reference detergents being used as controls.The precision of the soil removal tests is approximately ±3.4% in terms of mean deviation and that of the whiteness retention test approximately ±5.1%. Both tests have been used over a period of several years for research and control purposes and have been successfully correlated with actual results in commercial laundries.