Page images
PDF
EPUB

4. RESISTORS

4.1. Base Sheet Resistor (VDP), Structure 3.22

se sheet resistor (VDP), structure 3.22, is a four-terminal resistor ranged in an orthogonal van der Pauw (VDP) configuration [12] and consists a base diffused into the collector. As indicated below the active base gion is a square whose side, S, is 1.50 mil (38.1 μm) which is typical of tegrated circuit device geometries. The sheet resistance, Rç (VDP), is lculated from

Rg (VDP) = (V/I) (π/2n2)

(1)

ere the potential, V, is V1-V2 for a current, I, passed into I1 and out of

[merged small][merged small][ocr errors][ocr errors]

4.2. Base Sheet Resistor (B), Structure 3.28

Base sheet resistor (B), structure 3.28, is a four-terminal resistor arranged in a bridge (B) configuration and consists of a base diffused into the colle tor. This structure was designed according to ASTM standard F 76 [13]. The photomask dimension for the oxide window width, W (mask), is 1.50 mil (38.1 and the length, L (mask), between voltage taps is 6.0 mil (152 μm). The shee: resistance, Rg, is calculated from

Rs = (V/I) [We/L (mask)]

(2 where the potential, V, is V1-V2 for a current, I, passed into I1 and out of 12. The effective window width, We' is

We = W (mask) + aXj+ Woe

(3

where X is the junction depth, a is a coefficient which accounts for latera diffusion effects [14], Woe is the over-etch width. These quantities are illustrated in figure 3. Combination of the I/V ratio measured from this

[merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small]

structure with the sheet resistance Rg (VDP) measured from structure 3.22 leads to an equation for the effective base window width, We, [15]:

[merged small][merged small][merged small][subsumed][ocr errors][ocr errors][subsumed][subsumed][ocr errors][graphic]

4.3. Base Sheet Resistor (VDP, FP, CS), Structure 3.11

Base sheet resistor (VDP, FP, CS), structure 3.11, is a four-terminal resistor arranged in a van der Pauw (VDP) configuration [12] and consists of a base diffused into the collector. An emitter is diffused around the base and acts as a channel stop (CS). A metal field plate (FP) lies on top of the collector oxide between the base and channel stop and serves to shut off surface currents when it is biased so as to accumulate the collector. The active region is a circle 17.0 mil (432 um) in diameter. The sheet resistance, Rs is calculated from

Rs = (V/I) (π/Zn2)

[ocr errors]

(5)

where the potential, V, is V1-V2 for a current, I, passed into I1 and out of 12. This structure is useful when evaluating sheet resistances greater than 1000 /0.

[graphic][subsumed][subsumed][subsumed]

4.4.

Incremental Base Sheet Resistor (VDP), Structure 3.30

Incremental base sheet resistor (VDP) structure 3.30, is a four-terminal resistor arranged in a van der Pauw (VDP) configuration [12] and consists of a base diffused into the collector. The active region is 30.0 mil (762 μm) in diameter. The sheet resistance, Rg, is calculated from

Rs

=

(V/I) (T/Zn2)

(6) where the potential, V, and the current, I, are measured at the ends of the four legs. This structure was designed to facilitate the measurement of dopant profiles by the incremental sheet resistance method [16]. The resistivity, Pi, of the increment is

[merged small][subsumed][merged small][ocr errors][merged small]

where AX is the thickness of the increment and ARg is the sheet resistance of the increment. This method requires a method for determining AX and, in order to obtain dopant density values, requires a knowledge of the resistivity dopant density relation. An apparatus for automating this measurement is described elsewhere [17].

[graphic][ocr errors][subsumed][subsumed]

4.5. Emitter Sheet Resistor (VDP), Structure 3.21

Emitter sheet resistor (VDP), structure 3.21, is a four-terminal resistor arranged in an orthogonal van der Pauw (VDP) configuration [12] and consists of an emitter diffused into a base. The discussion for structure 3.22, section 4.1, is applicable to structure 3.21.

[graphic][subsumed][subsumed][merged small]

Emitter sheet resistor (B), structure 3.27, is a four-terminal resistor arranged in a bridge (B) configuration and consists of an emitter diffused into a base. The discussion for structure 3.28, section 4.2, is applicable to structure 3.27.

[graphic][subsumed]
« PreviousContinue »