Method of measuring etched state of semiconductor wafer using optical impedence measurement

A method for measuring a semiconductor wafer which has been subjected to an etching process, the method comprising the steps of:

• radiating light at the semiconductor wafer;
• measuring light within a selected wavelength band reflected from the semiconductor wafer to provide an output value;
• determining a ratio of the output value and a reference value, the reference value being based on light within the selected wavelength band reflected from a reference surface;
• and
• determining that the semiconductor wafer is under-etched if the determined ratio does not meet a reference ratio;
• and
• measuring light in the selected wavelength band reflected from a bare silicon reference surface to provide the reference value.

A method for measuring a semiconductor wafer which has been subjected to an etching process, the method comprising the steps of:

• radiating light at the semiconductor wafer;
• measuring light within a selected wavelength band reflected from the semiconductor wafer to provide an output value;
• determining a ratio of the output value and a reference value, the reference value being based on light within the selected wavelength band reflected from a reference surface;
• and
• determining that the semiconductor wafer is under-etched if the determined ratio does not meet a reference ratio;
• and
• wherein the step of measuring the light reflected from the semiconductor wafer further comprises the step of measuring a polarization ratio of light reflected from the semiconductor wafer to provide the output value.

A method of determining the etched state of a semiconductor wafer, the method comprising the steps of:

• radiating light a t bare silicon and obtaining a reference value from an electrical signal generated by light within a predetermined wavelength band of the light reflected from the bare silicon;
• radiating light within the predetermined wavelength band at a target of measurement, i.e., a wafer that has undergone an over-etching process;
• obtaining an output value corresponding to the reference value from an electrical signal generated by light within the predetermined wavelength band of the light reflected from the wafer;
• calculating the ratio of the output value to the reference value;
• and
• comparing the calculated ratio with a predetermined reference ratio to determine whether or not the wafer is under-etched.

A method of determining the etched state of a semiconductor wafer, the method comprising the steps of:

• radiating light at bare silicon and obtaining a reference value by integrating an electrical signal generated by light within a predetermined wavelength band which is reflected from the bare silicon;
• radiating light within the predetermined wavelength band at a target of measurement, i.e., a wafer that has undergone an over-etching process;
• obtaining an output value by integrating an electrical signal of the predetermined wavelength band of light reflected from the wafer;
• calculating a ratio of the output value to the reference value;
• and
• comparing the calculated ratio with a predetermined reference ratio to determine whether or not the wafer is under-etched.

A method of measuring the etched state of a semiconductor wafer, the method comprising:

• a first step of radiating light within a predetermined wavelength band at a wafer that has undergone a plasma over-etching process;
• a second step of obtaining a predetermined output value from an electrical signal corresponding to light reflected from the wafer;
• a third step of determining whether an optical impedance of the light reflected from the wafer changes based on the output value;
• a fourth step of determining whether the over-etching process is successfully completed depending on the change in the optical impedance determined in the third step;
• a fifth step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching completed film stack when it is determined that the over-etching process is successfully completed;
• and
• a sixth step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching incompleted film stack when it is determined that the over-etching process is not successfully completed.

A method of measuring the etched state of a semiconductor wafer, the method comprising:

• a first step of radiating light at bare silicon and obtaining a reference value 1 from an electrical signal generated by light within a predetermined wavelength band among the light reflected from the bare silicon;
• a second step of radiating light within the predetermined wavelength band at a target of measurement, i.e., a wafer that has undergone an over-etching process;
• a third step of obtaining an output value 1 corresponding to the reference value 1 from an electrical signal of light within the predetermined wavelength band among the light reflected from the wafer;
• a fourth step of calculating a ratio of the output value 1 to the reference value 1;
• a fifth step of comparing the calculated ratio with a predetermined reference ratio to determine whether or not the wafer is under-etched;
• a sixth step of measuring the thickness of remaining oxide using a predetermined under-etch recipe when it is determined that the wafer is under-etched;
• a seventh step of obtaining a predetermined output value 2 from an electrical signal corresponding to light reflected from the wafer when it is determined that the wafer is not under-etched;
• an eighth step of determining whether an optical impedance to the light reflected from the wafer changes based on the output value 2;
• a ninth step of determining whether or not the over-etching process is successfully completed depending on the change in the optical impedance determined in the above step;
• a tenth step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching completed film stack when it is determined that the over-etching process is successfully completed;
• and
• an eleventh step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching incompleted film stack when it is determined that the over-etching process is not successfully completed.

A method of measuring the etched state of a semiconductor wafer, the method comprising:

• a first step of radiating light within a predetermined wavelength band at a wafer that has undergone a plasma over-etching process;
• a second step of obtaining predetermined optical impedances 1 and 2 from an electrical signal corresponding to light reflected from the wafer;
• a third step of comparing the optical impedance 1 with a predetermined reference impedance 1 to determine whether or not the wafer is completely over-etched;
• a fourth step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching completed film stack when it is determined that the over-etching process is successfully completed in the third step;
• a fifth step of comparing the optical impedance 1 with a predetermined reference impedance 1 to determine whether or not the wafer is completely over-etched when it is determined that the over-etching process is not completed in the third step;
• a sixth step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching completed film stack when it is determined that the over-etching process is successfully completed in the fifth step;
• and
• a seventh step of measuring the thickness of a wafer film according to a recipe employing a predetermined over-etching incompleted film stack when it is determined that the over-etching process is not successfully completed.

A method for measuring a semiconductor wafer which has been subjected to an etching process, the method comprising the steps of:

• Radiating light at the semiconductor wafer;
• Measuring light within a selected wavelength band reflected from the semiconductor wafer to provide an output value;
• Determining a ratio of the output value and a reference value, the reference value being based on light within the selected wavelength band reflected from a reference surface different from the semiconductor wafer;
• and
• Determining that the semiconductor wafer is under-etched if the determined ratio does not meet a reference ratio.