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Critical Microstructure for Ion Implanted Gettering

IP.com Disclosure Number: IPCOM000087993D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Geipel, HJ: AUTHOR [+2]

Abstract

Dramatic differences are found in the backside-implant-gettering efficiencies in semiconductor wafers for a given dose between boron and the noble gases. In the range of ion dose of 10/14/ ions/cm/2/ through 10/15/ ions/cm/2/, noble gases are superior in gettering efficiency to similar doses of boron.

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Critical Microstructure for Ion Implanted Gettering

Dramatic differences are found in the backside-implant-gettering efficiencies in semiconductor wafers for a given dose between boron and the noble gases. In the range of ion dose of 10/14/ ions/cm/2/ through 10/15/ ions/cm/2/, noble gases are superior in gettering efficiency to similar doses of boron.

The ability of ion-damaged regions in Si to getter metallic impurities has previously been investigated quantitatively by He backscattering [1,2]. The relative gettering efficiency was found to be specie dependent and ranked in the order of A > O > P > Si > As > B. A correlation with the amount and type of disorder remaining after annealing, to the efficiency of gettering Au in Si, was suggested. Experimental correlation of the density of high free energy unit dislocations with gettering efficiency indicates that 1/2 <110> dislocations are critical in providing an improvement in gettering efficiency.

Using silicon material consisting of 2 ohm-cm, p-type [001] wafers known to contain Cu as the principal metallic contaminant, Xe was implanted at 170 keV with a dose range of 1 X 10/13/ to 6 X 10/15/ ions/cm/2/ on one wafer side, hereafter referred to as "the backside". Wafers were all misoriented 7 degrees from the ion beam to prevent channeling. An annealing treatment of 80 minutes at 1000 degrees C in O(2), followed by an in situ N(2) anneal, was used to induce recrystallization and form 450 angstroms of SiO(2). Metallization to complete 30 mil MOS (metal-oxide semiconductor) capacitor structures on the wafer front side was accomplished by E-gun Al evaporation. This was followed by a 30 minute, 400 degree C forming gas anneal.

Electrical characterization was carried out by pulsing YOS capacitors into deep depletion and calculating an equivalent leakage current for the relaxation to a quasi-equilibrium value. Slower relaxation time for the depletion width, in such circumstances, implies a smaller leakage current, and a more effective gettering process.

After electrical characterization, gettering centers were delineated by diffusion of Cu into the implanted region. To accomplish this diffusion, Cu was plated onto the EF-stripped front side of the wafers from a saturated Cu(NO(3))(2) - HF solution. The sample was then heated to approximately 1000 degrees C for 15 seconds as a drive-in.

Foils from all samples were prepared for transmission electron microscope (TEM) study by chemical jet polishing with HF-HNO from the front side. Suitable diffraction contrast conditions were employed to characterize disloc...