US3882319A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic melt level control for growth of semiconductor crystals
Assignee: Motorola Solutions Inc
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Filing: 1973-10-23
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Granted: 1975-05-06
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Expires: 1993-10-23
Abstract
Abstract Apparatus for controlling the melt level in a Czochralski crystal pulling method is disclosed. The melt level control has a feedback loop including level sensing means which controls a lift motor for moving the melt containing crucible up or down as called for. The melt level is sensed by alternately transmitting two pulsed beams, or rays, of narrow band visible red light radiation to the melt level surface and measuring the radiation level in the reflected pulse rays after transmission through a lens system. When the melt level is correct the magnitudes of the reflected pulses are equal and no control signal results. When the melt level falls, the magnitudes of the reflected pulses change and a difference signal in one direction is generated causing the crucible to rise. When the melt level rises, the magnitudes of the reflected pulses change and a difference signal in the opposite direction is generated causing the crucible to fall. The red light radiation preferably has a wavelength of 6500 A plus or minus 50 A.
Inventors
- 👤 Donald R Clement
- 👤 Larry D Mason
- 👤 Carl A Helber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:27
CPC Classifications
C; C30; C30B; C30B15/00; C30B15/30; C30B15/20; C30B15/22; Y; Y10; Y10T; Y10T117/00; Y10T117/10; Y10T117/1004; Y10T117/1008
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
135 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; source means for transmitting, at one angle to the vertical, a red radiation beam having a wavelength of approximately 6500A to the levEl surface of said melt; sensor means for receiving the reflection of said radiation beam; said sensor means being disposed at the same angle to the vertical as said source beam; said sensor means including means for detecting changes in said reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said detecting means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 2
Dependent Claim
135 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; source means for transmitting, at one angle to the vertical, a red radiation beam having a wavelength of approximately 6500A to the levEl surface of said melt; sensor means for receiving the reflection of said radiation beam; said sensor means being disposed at the same angle to the vertical as said source beam; said sensor means including means for detecting changes in said reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said detecting means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 3
Dependent Claim
19 words
Apparatus according to claim 1 wherein the angle between said source beam and said reflected beam is approximately 45*.
Claim 4
Dependent Claim
21 words
Apparatus according to claim 2 wherein one of said source means and said sensor means includes a narrow bandpass red filter.
Claim 5
Dependent Claim
21 words
Apparatus according to claim 2 wherein each of said source means and said sensor means includes a narrow bandpass red filter.
Claim 6
Dependent Claim
19 words
Apparatus according to claim 3 wherein said bandpass filter transmits at approximately 6500 A + or - 50 A.
Claim 7
Dependent Claim
165 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; first source means for transmitting, at one angle to the vertical, a first radiation beam to the level surface of said melt; second source means for transmitting, at another angle to the vertical, a second radiation beam to the level of said melt; sensor means for receiving the reflections of said first and said second radiation beams; said sensor means being disposed at an angle to the vertical to encompass the reflections of said first and said second radiation beams; said sensor means including means responsive to changes in said first and second reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said responsive means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 8
Dependent Claim
165 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; first source means for transmitting, at one angle to the vertical, a first radiation beam to the level surface of said melt; second source means for transmitting, at another angle to the vertical, a second radiation beam to the level of said melt; sensor means for receiving the reflections of said first and said second radiation beams; said sensor means being disposed at an angle to the vertical to encompass the reflections of said first and said second radiation beams; said sensor means including means responsive to changes in said first and second reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said responsive means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 9
Dependent Claim
12 words
Apparatus according to claim 6 wherein said radiation is red light radiation.
Claim 10
Dependent Claim
16 words
Apparatus according to claim 7 wherein said red radiation has a wavelength of approximately 6500 A.
Claim 11
Dependent Claim
20 words
Apparatus according to claim 7 wherein one of said first and second source means includes a narrow bandpass red filter.
Claim 12
Dependent Claim
21 words
Apparatus according to claim 7 wherein each of said source means and said sensor means includes a narrow bandpass red filter.
Claim 13
Dependent Claim
20 words
Apparatus according to claim 9 wherein said bandpass filters transmit at approximately 6500 A units + or - 50 A.
Claim 14
Dependent Claim
27 words
Apparatus according to claim 7 wherein said sensor means is responsive to the sum of the reflected radiation received from said first and said second radiation beams.
Claim 15
Dependent Claim
23 words
Apparatus according to claim 6 wherein the angle between said first and said second source beams and said reflected beams is approximately 45*.
Claim 16
Dependent Claim
209 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; first red source means for transmitting, at one angle to the vertical, a first radiation beam to the level surface of said melt; second red source means for transmitting, at another angle to the vertical, a second radiation beam to the level surface of said melt; sensor means for receiving the sum of the reflections of said first and said second radiation beams; said sensor means being disposed at an angle to the vertical to encompass the reflections of said first and said second radiation beams; means for alternately energizing said first and said second source means at a high frequency rate; means for focusing each of said first and said second radiation beams on the same spot at a designated melt level; said sensor means including means responsive to changes in said first and said second reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said responsive means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 17
Dependent Claim
209 words
Apparatus for pulling solid crystals from a melt wherein the level of said melt is maintained constant during the time that the crystal is being pulled comprising: a container for said melt; motor means for raising and lowering said container; first red source means for transmitting, at one angle to the vertical, a first radiation beam to the level surface of said melt; second red source means for transmitting, at another angle to the vertical, a second radiation beam to the level surface of said melt; sensor means for receiving the sum of the reflections of said first and said second radiation beams; said sensor means being disposed at an angle to the vertical to encompass the reflections of said first and said second radiation beams; means for alternately energizing said first and said second source means at a high frequency rate; means for focusing each of said first and said second radiation beams on the same spot at a designated melt level; said sensor means including means responsive to changes in said first and said second reflected radiation beams caused by corresponding changes in said melt level; and means controlled by said responsive means for effecting energization of said motor means to raise and lower, respectively, said container.
Claim 18
Dependent Claim
82 words
Apparatus according to claim 12 wherein said sensor means includes focusing means whereby the reflected beam from one of said first and said second radiation beams is greater in magnitude than that of said another reflected beam when said melt level is below a predetermined value, and whereby the reflected beam from said one of said first and said second radiation beams is lesser in magnitude than that of said another reflected beam when said melt level is above said predetermined value.
Claim 19
Dependent Claim
32 words
Apparatus according to claim 15 including a high frequency oscillator for energizing said first and said second radiation sources and for controlling the demodulation of the signals received by said sensor means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-05 | 1978-11-04 | 1979-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-05 | 1982-11-04 | 1983-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-05 | 1986-11-04 | 1987-05-06 | $7700.00 | Window Closed / Lapsed |