Threshold voltage adjustment

Step 6. The doping concentration of the "typ substrate under the gate oxide is adjusted by another boron implantation. Boron passes through the thin gate oxide. This provides the threshold voltage adjustment for the final device. 

Fig. 14.6. Application of ion implantations in advanced CMOS structure at several stages of the process, (a) Ion implants for retrograde well formation, punch-through-stop, and threshold voltage adjust (b) shallow source/drain (S/D) implant and (c) halo implant...

Medium current implantation typically refers to doses in the 1011—1014 cm"2 range at maximum energies of several hundred keV and as low as 3 keV. The most common applications for which medium current implanters are used include threshold voltage adjustment halo or pocket implants field isolation and channel engineering. 

MOS transistor Ion implantation is used for threshold voltage adjustment. Can also be used for self-. alignment with practically no gate overlap capacitance decouples parasitic capacitances. Can be used to obtain small channel lengths (30). 

For a given choice of gate materials, the gate oxide thickness, / , and the doping concentration, NB, are two parameters which can be used to adjust the threshold voltage. tox determines the value of Vox by... 

The threshold voltage can be adjusted to accommodate direct interfacing with TTL circuitry. 

The triple quadrupole mass spectrometer consists of a linear combination of three quadrupole mass analyzers. Figure 9.15 [2,56,111]. Only the first and third quadrupole have scan capability. The middle quadrupole, which is sometimes a multipole device of higher order, is a radio frequency-only, gas-filled collision cell with ion focusing properties. All ions above a certain threshold m/z value are transmitted by the middle quadrupole. An offset voltage between the ion source and collision cell can be adjusted to allow the collision energy to be varied between zero and about 200 eV. Inert gases (e.g. He, Ar, Xe) at a pressure of about 2-4 mTorr are commonly used as targets to... 

---