Determining semiconductor characteristic

• US 4,168,212 A
• Filed: 04/25/1978
• Issued: 09/18/1979
• Est. Priority Date: 05/16/1974
• Status: Expired due to Term

• Current Assignee: British Telecommunications (BT Group Plc) (BT Group PLC)
• Original Assignee: Post Office Limited (International Distributions Services plc)
• Inventors: Faktor, Marc M., Bremner, Ean G., Ambridge, Thomas
• Primary Examiner(s): Tung, T.
• Application Number:
  US05/899,990
• Time in Patent Office: 511 Days
• Field of Search: 204/1 T, 204/195 R, 204/129.2, 204/129.3
• US Class Current: 205/790.5
• CPC Class Codes: G01N 27/227 Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors G01N27/225 takes precedence
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

The electrochemical measuring technique of the present invention employs, as the barrier material, a concentrated electrolyte, which also forms a medium for the controlled dissolution of a surface of the semiconductor so as to provide a continuous depth profile. The depth profile characteristic may be determined by capacitance-voltage measurements on n-type bulk GaAs, using KOH as the electrolyte.

Claims

1. A method for determining carrier concentration as a function of depth in a semiconductor material comprising mounting the semiconductor material in an electrolytic cell so that electrolyte in the cell is in contact with the semiconductor material, applying a d.c. voltage to the material and electrolyte to simultaneously form a Schottky diode between the material and electrolyte and bring about anodic etching at the surface of the material with the aid of the electrolyte, applying an a.c. voltage to said Schottky diode, and measuring the capacitance of the depletion layer of the Schottky diode.

2. A method according to claim 1, including the step of modulating the a.c. voltage and measuring the differential capacitance of the depletion layer.

3. A method according to claim 1, including illuminating the surface of said material to provide minority carriers at the surface.

4. A method according to claim 3, wherein the surface is illuminated by light having a predetermined range of frequency.

5. A method according to claim 1, including the step of providing a continuous graphical plot of the relationship between carrier concentration at the surface of the Schottky diode and the thickness of the semiconductor etched from said area.