Method and apparatus for in-situ end-point detection and optimization of a chemical-mechanical polishing process using a linear polisher

In a linear chemical mechanical polishing device of the type comprising:

• at least two rollers;
• a belt comprising a layer of polishing material and mounted to extend between the rollers such that rotation of the rollers drives the belt;
• and a substrate carrier positioned adjacent the belt to press a substrate into contact with the belt intermediate the rollers;
• the improvement comprising:
• the belt having an opening formed therein, the opening positioned to move intermittently into alignment with the substrate as the belt is driven by the rollers;
• and
• the belt further comprising a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the window comprising a flexible material adapted to flex with the belt as the window moves around and between the rollers in use.

In a linear chemical mechanical polishing device of the type comprising:

• at least two rollers;
• a belt comprising a layer of polishing material and mounted to extend between the rollers such that rotation of the rollers drives the belt;
• a platen stationary with respect to the belt;
• and a substrate carrier positioned adjacent the belt to press a substrate into contact with the belt intermediate the rollers;
• the improvement comprising:
• the belt having an opening formed therein, the opening positioned to move intermittently into alignment with the substrate as the belt is driven by the rollers;
• the belt further comprising a first monitoring window secured to the belt to close the opening and to create a first monitoring channel in the belt;
• the platen having an opening formed therein, the opening being positioned to align with the belt opening;
• and the platen further comprising a second monitoring window secured to the platen to close the opening in the platen to create a second monitoring channel in the platen;
• whereby the second monitoring window secured to the platen is stationary with respect to the first monitoring window secured to the belt as the belt moves around and between the rollers in use.

A method for determining an end point of a chemical-mechanical polishing process with an interferometer using a linear polishing belt, the method comprising the steps of:

• (a) providing a belt having an opening formed therein and a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the monitoring window comprising a flexible material adapted to flex with the belt as the belt moves in use;
• (b) measuring a film thickness of a substrate during a chemical-mechanical polishing process with an interferometer when the monitoring channel in the belt aligns with a film thickness monitor;
• and then
• (c) repeating step (b) until the measured film thickness reaches a predefined thickness;
• and then
• (d) indicating that end point has been reached.

A method for determining removal rate per belt revolution at any given circumference of a substrate while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

• (a) providing a belt having an opening formed therein and a monitoring window secured to the belt to close the opening and to create a monitoring channel in the belt, the monitoring window comprising a flexible material adapted to flex with the belt as the belt moves in use;
• (b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the monitoring channel in the belt aligns with a film thickness monitor;
• and then
• (c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the monitoring channel in the belt realigns with the film thickness monitor;
• and then
• (d) calculating a difference between the second film thickness and the first film thickness.

A method for determining average removal rate per belt revolution across a substrate surface while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

• (a) providing a belt having a first and second opening formed therein and a first and second monitoring window secured to the belt to close the respective first and second openings and to create a respective first and second monitoring channel in the belt, the first and second monitoring windows each comprising a flexible material adapted to flex with the belt as the belt moves in use;
• (b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the first monitoring channel in the belt aligns with a first film thickness monitor;
• and then
• (c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the first monitoring channel in the belt realigns with the first film thickness monitor;
• and then
• (d) measuring a third film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt aligns with a second film thickness monitor;
• and then
• (e) measuring a fourth film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt realigns with the second film thickness monitor;
• and then
• (f) calculating a difference between the second film thickness of step (c) and the first film thickness of step (b);
• and
• (g) calculating a difference between the fourth film thickness of step (e) and the third film thickness of step (d);
• and then
• (h) calculating an average of the differences of steps (f) and (g).

A method for determining removal rate variation per belt revolution across a substrate surface while performing a chemical-mechanical polishing process using a linear polishing belt, the method comprising the steps of:

• (a) providing a belt having a first and second opening formed therein and a first and second monitoring window secured to the belt to close the respective first and second openings and to create a respective first and second monitoring channel in the belt, the first and second monitoring windows each comprising a flexible material adapted to flex with the belt as the belt moves in use;
• (b) measuring a first film thickness of a substrate with an interferometer during a chemical-mechanical polishing process when the first monitoring channel in the belt aligns with a first film thickness monitor;
• and then
• (c) measuring a second film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the first monitoring channel in the belt realigns with the first film thickness monitor;
• and then
• (d) measuring a third film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt aligns with a second film thickness monitor;
• and then
• (e) measuring a fourth film thickness of the substrate with the interferometer during the chemical-mechanical polishing process when the second monitoring channel in the belt realigns with the second film thickness monitor;
• and then
• (f) calculating a difference between the second film thickness of step (c) and the first film thickness of step (b);
• and
• (g) calculating a difference between the fourth film thickness of step (e) and the third film thickness of step (d);
• and then
• (h) calculating a variation of the differences of steps (f) and (g).