Endpoint determination for recess etching to a precise depth
First Claim
1. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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 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, said shallow recess being etched at approximately the predetermined final recess depth within a specified tolerance of substantially 6%.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for plasma etching a shallow recess or shallow trench at a predetermined depth by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer begins with a step of detecting an etch start time, either by detecting a time of plasma ignition, as extracted from reflectance data, or a time extracted from the reflectance data when a wafer reflectance signal is observed to begin to change after a residual layer is etched away prior to beginning a recess or trench etch. The next step is measuring a reflectance intensity of light reflected from the wafer. Preferably, a plasma background signal is removed from this measurement and an array detector is used wherein the wavelength is determined using the reflectance model. Next, an etch rate is determined by fitting data representing the collected reflectance signal to the wafer reflectance model as a function of time, and extracting the etch rate from the model. The model preferably takes into account each of a weakening of the reflectance signal as the recess or trench becomes deeper, any residual oxide layer breakthrough step performed prior to etching the recess or trench and preferably as well any etching of the mask or top reference layer. An etch stop time is determined based on the etch rate, the etch start time and the predetermined recess or trench depth. Preferably, a software timer will then trigger the endpoint such that etching is stopped at the determined etch stop time.
22 Citations
63 Claims
-
1. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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 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, said shallow recess being etched at approximately the predetermined final recess depth within a specified tolerance of substantially 6%. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- m, or 15-20 or more times shallower than 10 μ
-
17. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
- m, or 15-20 or more times shallower than 10 μ
-
26. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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. - View Dependent Claims (27, 28, 29, 30, 31)
- m, or 15-20 or more times shallower than 10 μ
-
32. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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. - View Dependent Claims (33)
- m, or 15-20 or more times shallower than 10 μ
-
34. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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.
- m, or 15-20 or more times shallower than 10 μ
-
35. A method for plasma etching a shallow recess at a predetermined final depth of less than approximately 0.67 μ
- m, or 15-20 or more times shallower than 10 μ
m deep trenches, and a width of less than approximately 0.5 μ
m 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.
- m, or 15-20 or more times shallower than 10 μ
-
36. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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%. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45)
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
-
46. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54)
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
-
55. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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. - View Dependent Claims (56, 57, 58, 59, 60)
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
-
61. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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.
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
-
62. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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.
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
-
63. A method for plasma etching a shallow trench at a predetermined final depth of less than approximately 0.6 μ
- m 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.
- m by illuminating a wafer with a light source and using a spectrometer to receive the light reflected from the wafer, comprising the steps of;
Specification