Endpoint determination for recess etching to a precise depth

A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μm, or 15-20 or more times shallower than 10 μm deep trenches, and a width of less than approximately 0.5 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow recess is etched at approximately the predetermined final recess depth within a specified tolerance,
• and the method further comprising a breakthrough step, wherein a residual layer is first etched prior to etching the recess and prior to the etch start time, and wherein the etch start time is after a plasma ignition time.

A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μm, or 15-20 or more times shallower than 10 μm deep trenches, and a width of less than approximately 0.5 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow recess is etched at approximately the predetermined final recess depth within a specified tolerance,
• wherein said calculating steps include factoring in a reduction in reflectance intensity based on the depth of the recess.

A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μm, or 15-20 or more times shallower than 10 μm deep trenches, and a width of less than approximately 0.5 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow recess is etched at approximately the predetermined final recess depth within a specified tolerance,
• wherein said calculating steps further include factoring in an etching of a top reference layer during said etch time.

A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μm, or 15-20 or more times shallower than 10 μm deep trenches, and a width of less than approximately 0.5 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow recess is etched at approximately the predetermined final recess depth within a specified tolerance,
• wherein an array detector is used for measuring the reflectance intensity, and wherein the wavelength of the light is determined from the reflectance model.

A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μm, or 15-20 or more times shallower than 10 μm deep trenches, and a width of less than approximately 0.5 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said recess;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final recess depth;
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow recess is etched at approximately the predetermined final recess depth within a specified tolerance;
• and
• reflecting light away using a chamber window that is not exactly parallel to the wafer surface so that light reflected from the window is not collected.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time based on at least one of a plasma ignition time, a detection of a beginning of a wafer reflectance change, and a time after plasma ignition determined by observing a change of reflectance intensity in the data indicating that a breakthrough step of etching a residual oxide layer has been completed;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, said shallow trench being etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow trench is etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%,
• and the method further comprising a breakthrough step, wherein a residual layer is first etched prior to etching the trench and prior to the etch start time, and wherein the etch start time is after a plasma ignition time.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow trench is etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%,
• wherein said calculating steps include factoring in a reduction in reflectance intensity based on the depth of the trench.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow trench is etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%,
• wherein said calculating steps further include factoring in an etching of a top reference layer during said etch time.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• and
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow trench is etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%,
• wherein an array detector is used for measuring the reflectance intensity, and wherein the wavelength of the light is determined from the reflectance model.

A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μm by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of:

• determining an etch start time;
• measuring reflectance intensities of light reflected from the wafer a number of times during said etching of said trench;
• calculating an etch rate from data of the measured reflectance intensities;
• calculating an etch stop time based on the etch start time, the etch rate, and the predetermined final trench depth;
• triggering an endpoint such that etching is stopped approximately at the determined etch stop time, whereby a shallow trench is etched at approximately the predetermined final trench depth within a specified tolerance of substantially 6%;
• and
• reflecting light away using a chamber window that is not exactly parallel to the wafer surface so that light reflected from the window is not collected.