4.16. Collector Hall Effect Resistor, Structure 3.26

Collector Hall effect resistor, structure 3.26, is a four-terminal resistor formed when this test pattern, fabricated on a silicon wafer, is scribed into a square chip 100 mil (2.54 mm) on a side. The backside metal must be removed for this structure to operate properly. Scribe lines were purposefully omitted from the BASE and EMITTER masks to prevent doping the periphery of this structure. Contacts are formed in the four corners by an emitter diffused in a square 4.5 mil (114 μm) on a side. (This is the net size of the emitter contacts after the wafer is scribed into chips where the chip has separated in the middle of the scribe line.) For this case the ratio of the length of the contact to the length of the chip is 0.045. For this ratio the correction factor for the Hall coefficient is less than 2 percent and the correction factor for the resistivity is much less than 1 percent [26]. The resistivity, c is calculated from [12]

where Xt is the wafer thickness, Vp is the voltage difference measured betwee nearest neighbor contacts for a current, I, passed between the remaining two contacts. The Hall coefficient, RH, is calculated from [12]

=

RH (VHXt)/(BI)

(13) where VH is the voltage difference measured between opposite contacts for a current, I, passed between the remaining two contacts and B is the magnetic field density perpendicular to the plane of the chip. The collector dopant density, N, is calculated from

where q is the electronic charge and r is the scattering factor [8], [9]. The recommended measurement procedures for these measurements are described elsewhere [13].

5.1. MOS Capacitor Over Collector (FP, CS), Structure 3.8

MOS capacitor over collector (FP, CS), structure 3.8, consists of a main gate,
G1, 15.0 mil (381 μm) in diameter which is surrounded by a field plate (FP),
G2 that overlaps a channel stop (CS) which also serves as a topside collector,
C, contact. The collector dopant density, N, is calculated from the high
frequency C-V Cmax-Cmin method [7] by using the transcendental relation:

where Co is the maximum (oxide) capacitance, Ci is the minimum (inversion) capacitance, A is the main gate area, k is the Boltzmann constant, T is temperature, Ɛs is the silicon dielectric constant, q is the electronic charge, and ni is the intrinsic carrier concentration. The value for N calculated from this method is a surface value which may be different from the bulk value due to dopant redistribution during oxidation [7].

To determine the bulk collector value a dopant profile is obtained by use of the high frequency C-V deep depletion method [6] where the collector dopant density, Ni (W), in an incremental region is calculated from

Ni (W) = (2/qEgA2) [AV/A (C-2)]

(16)

where AV is an incremental change in the gate voltage. The measured MOS capacitance, C, is

where Cs is the semiconductor capacitance. The depth, W, from the oxidesilicon interface to the edge of the depletion region is

(17)

(18)

MOS Capacitor Over Collector, Structure 3.19

5.2. MOS capacitor over collector, structure 3.19, consists of a circular main gate 15.0 mil (381 μm) in diameter without a peripheral field plate. structure is useful in evaluating charge spreading (ion migration) phenomena [27].

This

5.3. MOS Capacitor Over Collector, Structure 3.25

MOS capacitor over collector, structure 3.25, consists of a small square main gate 4.0 mil (102 um) on a side without a peripheral field plate. This structure is useful in evaluating measurement limitations due to small gate

areas.

BBB

5.4. MOS Capacitor Over Base, Structure 3.2

MOS capacitor over base, structure 3.2, consists of a metal gate, G, 15.0 mil (381 um) in diameter on top of an oxide layer over a diffused base, B. A diffused emitter surrounds the base and serves as a topside collector, C, contact. This structure is used to evaluate the base surface dopant density by the methods described in section 5.1 for structure 3.8. This structure is also useful as a base-oxide pinhole test. It can also be used for basecollector diode C-V measurements; however, the junction area calculation is somewhat complicated by the fact that the junction is not circular.

5.2.

MOS Capacitor Over Collector, Structure 3.19

MOS capacitor over collector, structure 3.19, consists of a circular main gate 15.0 mil (381 μm) in diameter without a peripheral field plate. This structure is useful in evaluating charge spreading (ion migration) phenomena [27].

5.3. MOS Capacitor Over Collector, Structure 3.25

MOS capacitor over collector, structure 3.25, consists of a small square main gate 4.0 mil (102 μm) on a side without a peripheral field plate. This structure is useful in evaluating measurement limitations due to small gate

areas.