Method for film thickness endpoint control

A method for controlling thickness of a film or film portion on a substrate comprising the steps of:

• positioning the substrate in a chamber,
• controlling environment in said chamber to cause a change in thickness of a film on said substrate, said substrate and film thereon comprising a workpiece on which film is to be deposited or at least partially removed,
• employing ellipsometry to measure delta and psi coordinates of said film, said step of measuring comprising:
• directing light at said workpiece as said film thickness is changed, and
• receiving light reflected from said workpiece,
• determining delta and psi coordinates of an endpoint representing a predetermined target film thickness,
• defining a control line through said endpoint and transverse to the direction of a plot of delta and psi coordinates of points representing film thickness near said endpoint, said last mentioned step comprising defining a control line through said endpoint in accordance with the equation A (D.sub.e) +B (P.sub.e)+C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the measured delta and psi coordinates of said endpoint,
• generating an error indicative of a relation between said line and points defined by said measured coordinates, and
• employing said error to terminate change in film thickness.

A method for controlling thickness of film on a substrate comprising the steps of:

• positioning the substrate in a chamber,
• controlling environment within said chamber to cause a change in thickness of film on said substrate,
• employing ellipsometry to measure delta and psi coordinates of said film,
• determining delta and psi coordinates of an endpoint of desired thickness,
• defining a control line through said endpoint in accordance with the equation A (D.sub.e)+B (.sub.e)+C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the delta and psi coordinates of said endpoint,
• said control line being a function of delta and psi that is zero for points on said control line passing through said endpoint and extending transverse to a plot of points of measured delta and psi coordinates near said endpoint
• generating an error that represents said function of measured delta and psi coordinates, and
• employing said error to signal attainment of said endpoint of desired thickness.

A method of controlling thickness of a film or film portion on a substrate comprising the steps of:

• positioning the substrate in a chamber,
• controlling environment within said chamber to cause thickness of said film to change,
• measuring ellipsometric parameters of said film as said film thickness changes, thereby defining points related to thickness of said film,
• defining, in a plane of said parameters, an unbounded line having a predetermined relation to a desired endpoint of target thickness of said film in accordance with the equation defining a control line through said endpoint that is defined by he equation A (D.sub.e)+B (P.sub.e)+C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the delta and psi coordinates of said endpoint and
• terminating the changing of film thickness when measured parameters have a predetermined relation to said unbounded line.

A method of controlling thickness of a film on a substrate comprising the steps of:

• subjecting the substrate to an environment that causes a change in thickness of film on the substrate,
• reflecting light from said film,
• repetitively measuring first and second ellipsometric parameters of light reflected from said film that define coordinates of points related to a film thickness endpoint,
• generating, in a coordinated system of said parameters, a locus of points for which a predetermined function of said first and second parameters is substantially zero, said step of generating comprising defining a control line through said endpoint in accordance with the equation A (D.sub.e)+B (P.sub.e)+C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the delta and psi coordinates of said endpoint,
• generating an error indicative of the relation between points defined by pairs of measured parameters and said locus, and
• employing said error to terminate change of thickness of the film.

Apparatus for rapid thermal processing of a workpiece comprising:

• a processing chamber,
• heater means for raising the temperature of a workpiece in said chamber,
• means in said chamber for supporting a workpiece to be heated by said heating means,
• means for introducing gas into said chamber,
• an ellipsometer comprising:
• polarizer module means for directing a polarized light beam into said chamber to a point on a workpiece supported on said workpiece support means,
• analyzer module means or receiving light reflected from a workpiece mounted on said workpiece support means,
• ellipsometer control means for generating measured delta and psi coordinates of light received by said analyzer module means, and
• endpoint control means responsive to said ellipsometer control means for receiving delta and psi coordinates measured by said ellipsometer during processing of a heated workpiece within said chamber, said endpoint control means comprising:
• means for defining a control line through a target endpoint of desired thickness in accordance with the equation A (D.sub.e)+B (.sub.e) +C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the delta and psi coordinates of said endpoint,
• detecting means for detecting a relation between a pair of measured delta and psi coordinates and said control line, and
• means responsive to said detecting means for providing an end of process signal.

Rapid thermal processing apparatus comprising:

• lamp means,
• means to support a workpiece, and
• means to optically couple said lamp means to a workpiece supported on said workpiece support means, to effect relatively uniform heating of said workpiece, said optical coupling means being a hollow, integrating light pipe that extends at lest substantially to said workpiece support means and that causes the intensity of light from said lamp means to be relatively uniform across said light pipe at said workpiece, said lamp means being disposed within said light pipe, the aspect ratio in aid light pipe being at least 1,
• means for directing a beam of polarized light at a workpiece on said workpiece support means,
• means for receiving polarized light reflected from said workpiece,
• ellipsometric means for computer delta and psi ellipsometric coordinates of received light reflected from said workpiece,
• means for determining delta and psi ellipsometric coordinates of a target endpoint of desired thickness of a film on aid substrate,
• means for defining a control line through said target endpoint transverse to the direction of a plot of delta and psi coordinates of film thickness at said endpoint in accordance with the equation A (D.sub.e)+B (P.sub.e)+C=0 wherein A, B, and C are constants of an unbounded line passing through the endpoint, and D.sub.e and P.sub.e are the delta and psi coordinates of said endpoint,
• means for reading measured delta and psi coordinates as thickness of film on said substrate is varied,
• means for generating an error signal representing a relation between said line and said measured coordinates,
• means for sensing a change in sign of said error signal,
• means for generating a stop signal in response to a sensed change of said sign, and
• means for deenergizing said lamp means and rapidly decreasing temperature of said substrate upon occurrence of said change of sign.