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Oxide photocurrent measurements and capacitance-voltage shift measurements were performed with a 10-keV x-ray source on metal-oxide semiconductor (MOS) buried-oxide (BOX) capacitors to characterize the charge motion and trapping in SIMOX buried-oxide layers. Photocurrents measured in the BOX are about one-half of the expected theoretical current that would be measured if both charge carriers moved through the oxide. Results from the photocurrent measurements together with capacitance-voltage (C-V) measurements and theoretical modeling indicate (for radiation generated charges escaping initial recombination) that holes are essentially trapped in place and most electrons move through the bulk oxide.

We characterize the radiation-induced charge trapping and transport propehes of the buried-oxide (BOX) layer using the photocurrent response technique and capacitance-voltage shift measurements for a variety of silicon-on-insulator (SOI) materials. We observe dramatic differences as a result of different BOX processing conditions. The radiation response of the SO1 as a whole is shown to be consistent with the basic properties of the material(s) contained in the BOX layer. In comparison to standard separation by implantation of oxygen (SIMOX) material, SIMOX receiving a supplemental oxygen implant and lowtemperature anneal produces large normalized photocurrent values indicating that both radiation-generated charge carriers move through the BOX. Of the materials examined, the bond-andetch-back silicon-on-insulator (BESOI) material containing a silicon nitride layer produced the lowest normalized photocurrents, heavy trapping of both carriers. By comparison BESOI with thermal oxide layers traps neither carrier in the oxide bulk.The results of this study should be considered in the design of radiation-hardened components and when considering processing variations.In our previous work [2], we examined bond-and-etch-back silicon-on-insulator (BESOI) material from several different vendors. We recorded a range of values for the normalized currents, depending on the vendor, with Zc,,,/lco typically in the range 0.7 to 1.1. Using standard pre-and post-irradiation capacitancevoltage (C-V) measurements, laTge mid-gap voltage shifts, AVw, were also measured. These results led us to conclude that most of the radiation-generated charge carriers move through the BOX layer, but that a substantial fraction become trapped at one of the interfaces.Separation by implantation of oxygen (SIMOX) is the leading SO1 material for future radiation-hardened microelectronics. Much research has been performed on standard SIMOX material and we, along with many others, have shown that this material traps holes in the bulk oxide layer very heavily and that the electrons move large distances in the BOX]. Through the use of the photocurrent technique, measurements obtained on all SIMOX material examined to date yield values of Ic,,,/Zco = 0.55 k 0.05, consistent with this interpretation of the transport properties. Additionally, large AVq relative to dose are measured in this material, indicating a large fraction of hole trapping. INTRODUC~ION EXPERIMENTAL DETAILSThe photoconduction current technique is an important tool in the analysis of the charge-trapping and transport properties in the buried-oxide (BOX) layer of silicon-on-insulator (SOI) material. This method, developed in our earlier work [l], provides a way to determine the amount of radiation-generated charge moving through the BOX layer. The experiment measures the photocurrent,fcm, resulting from the motion of the x-raygenerated electrons and holes in the BOX. In our analysis,Icm is normalized U, a theoretic maximum value, Ice, yielding a fraction lc,JIco. Values of the fractional cur...

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