Method of detecting end point of plasma processing and apparatus for the same

A method of detecting an end point of plasma processing, comprising the steps of:

• sequentially detecting, when processing using a plasma is performed for an object to be processed, emission intensities at specific wavelengths of emission from first and second active species in a designated period and after the designated period during the plasma processing by using photodetecting means, and outputting emission detection information;
• obtaining an approximate expression A of the first active species and an approximate expression B of the second active species in a relationship between the emission intensity and time on the basis of the emission detection information in the designated period;
• obtaining an affine approximate expression A' of the first active species by using the approximate expression A of the first active species and the approximate expression B of the second active species;
• obtaining a ratio (A/A') of the approximate expression A of the first active species to the affine approximate expression A' of the first active species and a derivative (d(A/A')/dt) of the ratio;
• obtaining average values and variances of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio in the designated period;
• preparing a graph in which the ratio (A/A') is plotted on an abscissa, the derivative (d(A/A')/dt) of the ratio is plotted on an ordinate, and an intersection between the average value of the ratio (A/A') and the average value of the derivative (d(A/A')/dt) of the ratio in the designated period is an origin, and determining an end point of the plasma processing when a position of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio obtained by using the emission detection information of the first and second active species during the processing after the designated period in the graph deviates from the origin and again comes close to the abscissa.

A method of detecting an end point of plasma processing, comprising the steps of:

• detecting, while processing using a plasma is performed for an object to be processed, emission intensities respectively at specific wavelengths of first and second active species generated by the plasma in a designated period and after the designated period during the processing, and outputting emission detection information;
• obtaining an approximate expression A of the first active species and an approximate expression B of the second active species, each of which approximates a change in the emission intensity with passing of time and represents a straight line or a curve, on the basis of the emission detection information;
• obtaining an affine approximate expression A' of the first active species by substituting an elapsed time of the approximate expression B of the second active species into an elapsed time of the approximate expression A of the first active species;
• obtaining a ratio (A/A') of the approximate expression A of the first active species to the affine approximate expression A' of the first active species and a derivative (d(A/A')/dt) of the ratio;
• obtaining average values and variances of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio in the designated period;
• preparing a graph in which the ratio (A/A') is plotted on one axis of orthogonal coordinates, the derivative (d(A/A')/dt) of the ratio is plotted on the other axis of the orthogonal coordinates, and an intersection between the average value of the ratio (A/A') and the average value of the derivative (d(A/A')/dt) of the ratio in the designated period is an origin, and setting a predetermined region in the graph from a predetermined value of the ratio
• (A/A') and a predetermined value of the derivative (d(A/A')/dt) of the ratio calculated from information of the variances;
• and
• obtaining the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio by using the emission detection information of the first and second active species during the processing after the designated period, and determining an end point of the plasma processing when a position of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio thus obtained deviates from the predetermined region in the graph.

An apparatus for detecting an end point of plasma processing, comprising:

• photodetecting means for detecting, when processing using a plasma is performed for an object to be processed, changes with time in emission intensities at specific wavelengths of first and second active species generated by the plasma, and outputting emission detection information;
• arithmetic means for obtaining an approximate expression A of the first active species and an approximate expression B of the second active species in a relationship between the emission intensity and time on the basis of the emission detection information in the designated period, obtaining an affine approximate expression A' of the first active species by using the approximate expression A of the first active species and the approximate expression B of the second active species, obtaining a ratio (A/A') of the approximate expression A of the first active species to the affine approximate expression A' of the first active species and a derivative (d(A/A')/dt) of the ratio, and obtaining average values and variances of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio in the designated period;
• graph forming means for forming a graph in which the ratio (A/A') is plotted on an abscissa, the derivative (d(A/A')/dt) of the ratio is plotted on an ordinate, and an intersection between the average value of the ratio (A/A') and the average value of the derivative (d(A/A')/dt) of the ratio is an origin;
• and
• determining means for setting a predetermined region from a predetermined value of the ratio (A/A') and a predetermined value of the derivative (d(A/A')/dt) of the ratio calculated from information of the variances, obtaining the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio by using the emission detection information of the first and second active species during the processing after the designated period, and determining an end point of the plasma processing when a position of the ratio (A/A') and the derivative (d(A/A')/dt) of the ratio thus obtained deviates from the predetermined region in the graph.