A-C:H ISFET device, manufacturing method, and testing methods and apparatus thereof

A method for fabricating an a-C:H gate ISFET device, comprising steps of:

• providing a semiconductor substrate;
• forming an virtual gate on the semiconductor substrate to define the gate area of the ISFET;
• forming a source/drain in the semiconductor substrate beside the virtual gate;
• removing the virtual gate;
• forming an a-C:H gate in the gate area to form a ISFET by PE-LPCVD.

A method of measuring the temperature parameters of an ISFET with an a-C:H as a detection membrane, comprising:

• immersing the detection membrane in a buffer solution;
• changing the pH of the buffer solution at a predetermined temperature;
• measuring and recording the source-drain current and the gate voltage of the ISFET to obtain a curve;
• selecting a fixed current from the curve to obtain the sensitivity of the ISFET at the predetermined temperature;
• changing the temperature of the buffer solution and repeating immersion, pH change, measurement, recording and selection, to obtain the sensitivities of the ISFET at different temperatures.

An apparatus for measuring the temperature of an ISFET with a-C:H as a detection membrane, comprising:

• a semiconductor substrate where the ISFET is formed, comprising a pair of sources and drains separated from each other and the detection membrane insulated from the surface of the semiconductor substrate;
• a buffer solution contacting the ISFET;
• a light-isolating container for the buffer solution;
• a heater for the buffer solution;
• a temperature controller for the solution heater;
• a test fixer connected to the source and drain of the ISFET;
• and
• a current/voltage measuring device connected to the test fixer to measure and record the source-drain current and the gate voltage of the ISFET.

A method of measuring the hysteresis width of an ISFET with a-C:H as a detection membrane, comprising the steps of:

• fixing the drain-source current and the drain-source voltage of the ISFET by a constant voltage/current circuit;
• immersing the detection membrane in a buffer solution;
• recording the gate/source output voltage of the ISFET by a voltage-time recorder;
• and
• changing the pH of the buffer solution and repeating fixing, immersion and recording to measure the hysteresis width of the ISFET.

An apparatus of measuring the hysteresis width and the drift rate, comprising:

• an a-C:H ISFET formed on a semiconductor substrate, comprising a pair of source/drain regions within the semiconductor and a detection membrane of a-C:H isolated from the surface of the semiconductor substrate;
• a buffer solution for receiving the a-C:H ISFET;
• a light-isolation container for isolating light and carrying buffer solution and the a-C:H ISFET;
• a heater for heating the buffer solution;
• a constant current/voltage circuit coupled to the source and drain of the a-C:H ISFET to fix the drain/source current and the drain/source voltage of the a-C:H ISFET;
• a current/voltage measuring device coupled to the constant current/voltage circuit;
• and
• a voltage-time recorder coupled to the constant current/voltage circuit to record the gate/source output voltage of the a-C:H ISFET.