International Business Machines Corporation

Other

Kla Tencor Corporation

Keithley Instruments, Inc.

Min-Su Fung

Roger L Verkuil

Gregory S Horner

William H Howland

Huntington W Curtis

Bob H Yun

Frederick Albert Flitsch

Corona charges are used to bias a wafer to push down mobile charges and then pull them up during temperature cycles. Mobile charge is measured from the drops in the corona voltage due to the mobile charges. Corrections are made in the measurements for dipole potentials, leakage and silicon band-bending.

Non-contact mobile charge measurement with leakage band-bending and dipole correction

A semi conductor manufacturing process including uniform negative polarity wafer charging to remove or immobilize alkali ions such that the device becomes immune to their presence. The wafer is charged with a corona discharge at a 1MV/cm-2MV/cm bias field and low temperature (200.degree. C.-300.degree. C.) heating to bring mobile ions to the wafer's surface. Surface mobile ions are removed with a deionized (DI) water rinse or a standard sequential wafer wet cleaning step, immobilized with a normal gate (polysilicon) or metal contact formation step or both, thereby effectively removing mobile ions from the semiconductor structure.

Mobile charge immune process

An apparatus for measuring charge in an oxide layer overlying a silicon substrate containing very high density product chips characterized by thick oxides and high substrate doping levels in the field regions. A specially designed extremely thin conductive probe is pressed against the oxide layer whose charge is to be measured. A bias is applied to the probe for biasing the underlying silicon surface into accumulation or inversion. An intensity modulated light beam is focussed at the point of probe contact. The resulting amplitude modulated photovoltage is detected and applied to a computer to derive the value of the oxide charge therefrom.

Photovoltaic oxide charge measurement probe technique

A method and apparatus comprises heating a wafer to a temperature sufficient to temperature stress the wafer and enable ion motion. The wafer is then initialized in a measurement region with a non-contact corona discharge of a first polarity until a first dielectric field is developed, wherein any mobile ions present in the dielectric layer or at an air/dielectric interface move to a substrate/dielectric interface. A non-contact pulsed corona discharge of a second polarity, opposite the first polarity, is then applied to the wafer until a second dielectric field is developed and an amount of corona discharge Q.sub.MEASURED necessary to change the dielectric field from the first dielectric field to the second dielectric field is measured, wherein any mobile ions present at the dielectric/substrate interface move to the air/dielectric interface. An ideal amount of corona discharge Q.sub.IDEAL, in the absence of any highly mobile ionic species, necessary to change the dielectric field voltage of a dielectric layer of known thickness from a third dielectric field to a fourth dielectric field is then established. Lastly, measured corona discharge Q.sub.MEASURED is compared to ideal corona discharge Q.sub.IDEAL, wherein a quantitative difference between Q.sub. MEASURED and Q.sub.IDEAL is indicative of the amount of mobile charge Q.sub.MOBILE, Q.sub.MOBILE being representative of the amount of mobile ionic species in the dielectric layer.

Contactless corona-oxide-semiconductor Q-V mobile charge measurement

A contactless technique for semiconductor wafer testing comprising: depositing charges on the top surface of an insulator layer over the wafer to create an inverted surface with a depletion region and thereby a field-induced junction therebelow in the wafer, with an accumulated guard ring on the semiconductor surface therearound. The technique further includes the step of changing the depth to which the depletion region extends below the inverted semiconductor wafer surface to create a surface potential transient, and the step of measuring a parameter of the resultant surface potential transient. This technique may be utilized to make time retention and epi doping concentration measurements. It is especially advantageous for reducing the effects of surface leakage on these measurements. In a preferred embodiment, corona discharges are used to effect the charge deposition configuration. Either corona discharge or photon injection are used to change the depletion region depth.

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Lagrangeville, NY, United States of America

Min-Su Fung