Control Wafer Research Articles

Diffusion in Thin Silicon Films Formed by Electrochemical Etching

The diffusion of dopant atoms into thin silicon films formed by an electrochemical ‐etching technique has been investigated. Dopant atoms have been diffused from boron‐ and phosphorus‐doped, vapor‐deposited oxides into both thin‐film samples of the opposite conductivity type and into bulk control wafers. The diffusion characteristics of the impurity atoms are generally similar in the thin films and in bulk wafers. Second‐order effects include slightly higher sheet conductances in the thin films than in the bulk control wafers and slightly shallower diffusion of phosphorus into p‐type films than into bulk wafers. The oxidation rate of the thin films is the same as that of bulk silicon.

Measurement of resistivity and mobility in silicon epitaxial layers on a control wafer : W. J. Patrick. Solid-State Electronics9 (1966), p. 203

Measurement of resistivity and mobility in silicon epitaxial layers on a control wafer : W. J. Patrick. Solid-State Electronics9 (1966), p. 203

Measurement of resistivity and mobility in silicon epitaxial layers on a control wafer

When resistivity measurements are performed on high sheet resistance layers deposited on substrates of the opposite conductivity type, an apparent dependence of resistivity upon measuring current is observed. A description of this effect is given, and its relation to the accuracy of four-point probe measurements on control wafers is discussed. An explanation is given in terms of the influence of leakage currents on the biasing of the isolating p− n junction. If precautions are taken, the errors for a given sample can be minimized, but often they cannot be eliminated. Hall mobility measurements on epitaxial films are not severely affected by this leakage problem, and the experimental results obtained are in good agreement with published values.

A Novel Four‐Point Probe for Epitaxial and Bulk Semiconductor Resistivity Measurements

A novel configuration for a four‐point probe with points on opposite sides of the wafer is proposed. The potential distribution from a small area contact on a two resistivity epitaxial structure is given. The effects of the layer and substrate parameters on this potential distribution are discussed. A consideration of these potential distributions indicates that a probe of this design would be usable for epitaxial layer resistivity measurement under the design considerations discussed. These same potential distributions indicate that a two‐point probe is also usable. Brief experimental results of the over‐under four‐point probe on bulk silicon are given. The two point probe is contrasted experimentally with the P‐type control wafer, and three point breakdown for measurement of N on N+ epitaxial silicon.

The Effect of Barometric Pressure Changes upon Temperature Control in Incubators Equipped with Gas Wafer Thermostats

It does not seem to be recognized sufficiently among operators of incubators and other precision temperature equipment that the flexible gas wafer thermostat is affected by barometric pressure as well as by temperature changes. An increase in barometric pressure has the effect of compressing the wafer slightly, this compression acting the same as a decrease in temperature; consequently, the machine responds by building up heat to compensate for the increase in pressure upon the control wafer. This resulting change in the temperature of the incubator is therefore an additional variation to the normal lag between the “make” and “break” of the control mechanism.PROCEDUREThe observations herein recorded were made upon a standard, well-known incubator in good mechanical condition. The thermometer used was a number 19245-B made by the Central Scientific Company, and was graduated in 1/10°C. increments, but could be read fairly easily to 1/100°C. increments by means of .