Patent US5625170A successfully refreshed from Google Patents.
US5625170A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Precision weighing to monitor the thickness and uniformity of deposited or etched thin film
Assignee: Nanometrics Inc
•
Filing: 1994-01-18
•
Granted: 1997-04-29
•
Expires: 2014-01-18
Abstract
Abstract A time delayed differential weighing procedure used with an electronic analytical balance is optimized for samples exhibiting a small change in mass, for example from deposition, etching, plating or corroding, relative to the sample mass to minimize all significant sources of error that could otherwise degrade the measurement results, such as errors resulting from air density and temperature changes that occur during the interval between the first measurement of a sample, before the sample is processed, and a subsequent measurement of the sample, after the sample is processed. A calibration standard having substantially the same density as that of the sample is weighed both times the sample is weighed, i.e. before and after processing, to track the change in the sample balance reading due to air density and temperature changes, and thereby eliminate sample related errors. Balance and weighing procedure accuracy and precision are tested by a gauge study procedure. A procedure for determining area exposed after photoresist develop on a semiconductor wafer application is also provided.
Inventors
- 👤 Jaime Poris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 14:15
CPC Classifications
G; G01; G01G; G01G23/00; G01G23/01; G01G23/012; G01G17/00
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
140 words
A time delayed differential weighing process, comprising the steps of: weighing at least one sample with a balance before sample processing to obtain a first value corresponding to sample mass; weighing a calibration standard of substantially the same density as said sample at substantially the same time as the sample is weighed before said sample processing to obtain a first value corresponding to calibration standard mass; reweighing said sample after sample processing to obtain a second value corresponding to sample mass; reweighing said calibration standard at substantially the same time as the sample is weighed after sample processing to obtain a second value corresponding to calibration standard mass; and compensating for temperature and air density changes during a sample processing interval by comparing calibration standard mass values obtained before and after sample processing to eliminate temperature and air density errors.
Claim 2
Dependent Claim
140 words
A time delayed differential weighing process, comprising the steps of: weighing at least one sample with a balance before sample processing to obtain a first value corresponding to sample mass; weighing a calibration standard of substantially the same density as said sample at substantially the same time as the sample is weighed before said sample processing to obtain a first value corresponding to calibration standard mass; reweighing said sample after sample processing to obtain a second value corresponding to sample mass; reweighing said calibration standard at substantially the same time as the sample is weighed after sample processing to obtain a second value corresponding to calibration standard mass; and compensating for temperature and air density changes during a sample processing interval by comparing calibration standard mass values obtained before and after sample processing to eliminate temperature and air density errors.
Claim 3
Dependent Claim
23 words
The method of claim 1, further comprising the step of: automatically calibrating said balance when about a 1.5° C. temperature change is detected.
Claim 4
Dependent Claim
28 words
The method of claim 1, further comprising the step of: waiting for a predetermined number of identical readings after balance stability is achieved before recording a balance result.
Claim 5
Dependent Claim
35 words
The method of claim 1, further comprising the step of: loading and unloading an internal balance calibration weight a predetermined number of times of selected duration to precondition said balance and compensate for balance dormancy.
Claim 6
Dependent Claim
46 words
The method of claim 1, further comprising the step of: converting a calculated mass measurement for a flat sample having a film formed thereon to an average sample thickness value by dividing said sample mass measurement by a sample area value and a sample density value.
Claim 7
Dependent Claim
66 words
The method of claim 1, wherein said compensating step further comprises: determining a value representing change in sample weight by calculating the difference between the second sample mass value and the first sample mass value, where the first sample mass value is first multiplied by an adjustment factor expressed as the ratio of the second calibration standard mass value to the first calibration standard mass value.
Claim 8
Dependent Claim
87 words
The method of claim 6, further comprising the steps of: calibrating said balance with an internal balance calibration weight; and determining film mass for a sample comprising a flat substrate having a thin film formed thereon by multiplying said value representing change in sample weight by an average correction factor f derived according to the following: f=[(1-a/dcal)/(1-a/df)]*[1+(T-Tcal)*Terr]; where: a=density of air; dcal=density of an internal balance calibration weight; df=density of said film; T=temperature when a balance reading is made; Tcal=temperature when calibration is performed; and Terr=temperature error.
Claim 9
Dependent Claim
26 words
The method of claim 1, wherein said calibration standard is weighed at least twice at such times as a series of sample measurements is being performed.
Claim 10
Dependent Claim
134 words
A time delayed differential weighing apparatus, comprising: a balance for weighing at least one sample to obtain first and second values corresponding to sample mass before and after sample processing, respectively; a calibration standard of substantially the same density as said sample, wherein said calibration standard is weighed at substantially the same time as said sample before said sample processing to obtain a first value corresponding to calibration standard mass, and wherein said calibration standard is reweighed at substantially the same time as said sample after sample processing to obtain a second value corresponding to calibration standard mass; and means for compensating for temperature and air density changes during a sample processing interval by comparing calibration standard mass values obtained before and after sample processing to derive a temperature and air density adjustment value.
Claim 11
Dependent Claim
134 words
A time delayed differential weighing apparatus, comprising: a balance for weighing at least one sample to obtain first and second values corresponding to sample mass before and after sample processing, respectively; a calibration standard of substantially the same density as said sample, wherein said calibration standard is weighed at substantially the same time as said sample before said sample processing to obtain a first value corresponding to calibration standard mass, and wherein said calibration standard is reweighed at substantially the same time as said sample after sample processing to obtain a second value corresponding to calibration standard mass; and means for compensating for temperature and air density changes during a sample processing interval by comparing calibration standard mass values obtained before and after sample processing to derive a temperature and air density adjustment value.
Claim 12
Dependent Claim
22 words
The apparatus of claim 9, further comprising: means for automatically calibrating said balance when about a 1.5° C. temperature change is detected.
Claim 13
Dependent Claim
28 words
The apparatus of claim 9, further comprising: a counter adapted to detect a predetermined number of identical readings after balance stability is achieved before recording a balance result.
Claim 14
Dependent Claim
34 words
The apparatus of claim 9, further comprising: means for loading and unloading an internal balance calibration weight a predetermined number of times of selected duration to precondition said balance and compensate for balance dormancy.
Claim 15
Dependent Claim
45 words
The apparatus of claim 9, further comprising: means for converting a calculated mass measurement for a flat sample having a film formed thereon to an average sample thickness value by dividing said sample mass measurement by a sample area value and a sample density value.
Claim 16
Dependent Claim
68 words
The apparatus of claim 9, wherein said means for compensating further comprises: means for determining a value representing change in sample weight by calculating the difference between the second sample mass value and the first sample mass value, where the first sample mass value is multiplied by an adjustment factor expressed as the ratio of the second calibration standard mass value to the first calibration standard mass value.
Claim 17
Dependent Claim
88 words
The apparatus of claim 14, further comprising: at least one internal balance calibration weight for calibrating said balance; and means for determining film mass for a sample comprising a flat substrate having a thin film formed thereon by multiplying said value representing change in sample weight by an average correction factor f derived according to the following: f=[(1-a/dcal)/(1-a/df)]*[1+(T-Tcal)*Terr]; where: a=density of air; dcal=density of an internal balance calibration weight; df=density of said film; T=temperature when a balance reading is made; Tcal=temperature when calibration is performed; and Terr=temperature error.
Claim 18
Dependent Claim
26 words
The apparatus of claim 9, wherein said calibration standard is weighed at least twice at such times as a series of sample measurements is being performed.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-04-28 | 2000-10-28 | 2001-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-04-28 | 2004-10-28 | 2005-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-04-28 | 2008-10-28 | 2009-04-29 | $7700.00 | Window Closed / Lapsed |