| 摘要 |
1319032 Measuring semi-conductor impurity concentration WESTERN ELECTRIC CO Inc 13 Jan 1971 [19 Jan 1970] 1619/71 Heading G1U The deep impurity concentration in a semiconductor wafer 12 is determined by forming a depletion layer in the wafer, using a Schottby diode 13 reverse-biased from a variable D.C. source 18, applying an alternating current signal from a source 20 to the diode, developing across the wafer a voltage of the frequency of the second harmonic of the frequency of the applied signal and, determining the phase difference in a detector 26 between the derived second harmonic voltage and a second harmonic voltage derived from a frequency doubler 30 connected to the source, which phase difference is proportional to the concentration of deep impurities at the edge 19 of the depletion layer and is displayed on on XY recorder 28. As disclosed in Specification 1269263 (see Division G1) the depth of the depletion layer is proportional to the amplitude of the fundamental voltage developed across wafer which is derived by a filter 27 and applied to the X-co-ordinates of the X-Y recorder, the Y co-ordinate being fed from the phase detector 26 to record deep impurity concentration vs. depth. The edge 19 of the depletion layer is caused to move through the wafer by variation of the voltage from source 18. A combined apparatus for measuring deep impurity concentration as above and doping density profile as described in the above-mentioned specification is illustrated in Fig. 3 (not shown) where the amplitude of the second harmonic voltage developed across the wafer 13 derived by a received 37 which amplitude is proportional to the shallow impurity concentration at the edge of the depletion layer. |
