Recently described procedures for the elimination of oxidation‐induced stacking faults have been incorporated into a device processing line to yield data on the leakage in p‐n junction tester diodes. The gettering processes, which take place on the back side of a wafer before the first oxidation, include the deliberate introduction of misfit dislocations and/or the deposition of a highly strained layer of
Si3N4
. The results show that leakage currents can be reduced by several orders of magnitude and diode yields increased from about 10% to greater than 90%. By doing “post mortem” chemical etch pit studies on previously electrically mapped
10normalthinsp;×normalthinsp;10
arrays of diodes the relative effectiveness of the two gettering schemes are compared. Factors such as the type of stacking fault, whether it be related to a native or process‐induced source, or whether it is clean or decorated are discussed as well as the influence of slip‐type dislocations.
The properties of CVD tungsten films, produced by the hydrogen reduction of WF6 or WCl6, have been investigated to determine the suitability of the films for use as silicon integrated circuit metallization.s. Both low pressure and atmospheric pressure flow system have been investigated.The tur~gsten films show excellent adhesion to silicon substrates, have resistivities between 6 and 15 #ohm-cm depending on thickness, and are easily etched into submicron patterns. In addition, data on the contact resistance to silicon and MOS properties of tungsten films from both deposition reactions have been measured.The use of chemical vapor deposition (CVD) to deposit thin tungsten films for integrated circuit metallizations has been investigated for several years (1, 2). Usually the tungsten is deposited using the hydrogen reduction of tungsten hexafluoride at temperatures between 600 ~ and 800~ The process is easily controlled and produces excellent tungsten films which are suitable for some integrated circuit applications (2).However, the corrosive nature of the reactants and products tends to degrade the thermally oxidized silicon wafers used for the integrated circuits. This fact has generated additional interest in the use of tungsten hexachloride, which is less corrosive toward SIO2, and has been used to deposit tungsten films in a similar manner to the hexafluoride (3, 4) although less information is available on their subsequent use for integrated circuit metallizations.Consequently we have compared the two reactions for application to silicon integrated circuits, extending previous studies to include the use of CVD tungsten as a gate metallization for unipolar devices.
ExperimentalTungsten films were deposited in both atmospheric and low pressure (1-10 Torr) flow systems from the hexafluoride and at atmospheric pressure from the hexachloride. Schematic diagrams of the deposition systems are shown in Fig. 1 and 2. The systems were rf heated using graphite or molybdenum susceptors. The temperature was controlled by a thermocouple embedded in the susceptor. The low pressure system proved somewhat unsatisfactory for two reasons. Firstly, at low pressure good thermal contact between the susceptor and the substrate is difficult to achieve and an inevitable uncertainty exists as to the substrate surface temperature in a fast flow system. Secondly, the use of rf heating at low pressure resulted in a plasma in the deposition chamber, the effect of which could result in ion bombardment damage to sensitive substrates.The tungsten hexachloride saturator and the gas lines leading from the saturator to the reaction chamber were heated to 150 ~ 4-5oC. Chemicals used were: hydrogen, purified using a palladium diffuser; argon, purified using a titanium chip furnace; helium (99.-9999%); hydrogen chloride (99.99%); tungsten hexafluoride (99.5%); and tungsten hexachloride (c9%). The major impurity in the tungsten hexachloride was tungsten oxychloride (WOC14) which was removed by sub]imation at 100~ The thickness of the deposited tungs...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.