1. A calibration system for a portable locator, comprising:
a frame for supporting a locator;
a pair of coil windings mounted on the frame for generating a substantially symmetrical electromagnetic field surrounding the locator when supported on the frame when the coil windings are energized with a predetermined signal generated by a transmitter;
a drive assembly for rotating the locator; and
an interface that enables a computer to sample field strength signals from the locator at different rotational positions of the locator.
2. A calibration system for a portable locator, comprising:
a frame for supporting a locator;
a pair of coil windings mounted on the frame for generating a symmetrical electromagnetic field surrounding the locator when supported on the frame when the coil windings are energized with a predetermined signal generated by a transmitter;
a drive assembly for rotating the locator; and
an interface that enables a computer to sample field strength signals from the locator at different rotational positions of the locator;
wherein the system is configured so that the computer can control the rotation of the drive assembly and store position signals generated by the drive assembly corresponding to the sampled field strength signals.
3. The calibration system of claim 1 wherein the coil windings are substantially matched Helmholtz coils.
4. The calibration system of claim 3 wherein the coil windings are each made of a single turn of Copper tape.
5. The calibration system of claim 1 wherein the support for the locator includes a mount that receives an antenna node of the locator.
6. The calibration system of claim 5 wherein the mount that supports the antenna node is rotated by the drive assembly.
7. The calibration system of claim 1 wherein the frame is made of non-metallic parts.
8. The calibration system of claim 1 wherein the mount is connected to the frame by a coupling that permits a vertical position of the locator with respect to the frame to be adjusted.
9. The calibration system of claim 1 wherein the drive assembly includes a drive motor and a rotary encoder assembly.
10. The calibration system of claim 1 wherein the interface includes a USB hub.
11. A calibration system for a portable locator, comprising:
means for supporting a portable locator;
means for generating an electromagnetic field around the locator; and
means for enabling a plurality of field strength samples to be extracted from the locator representing different angular andor vertical positional relationships of the locator and the electromagnetic field.
12. The calibration system of claim 11 wherein the field generating means includes a pair of matched Helmholtz coils.
13. The calibration system of claim 11 wherein the supporting means includes a mount that receives an antenna node of the locator.
14. The calibration system of claim 11 wherein the extracting means includes a computer interface.
15. The calibration system of claim 11 wherein the supporting means includes means mounted on the frame for rotating the locator.
16. The calibration system of claim 15 wherein the extracting means includes means connected to locator rotating means and the locator for sampling field strength signals from the locator at a plurality of different rotational positions of the locator relative to the electromagnetic field.
17. The calibration system of claim 11 wherein the supporting means includes means for raising and lowering the locator relative to the electromagnetic field.
18. The calibration system of claim 17 wherein the extracting means includes means for enabling field strength samples to be extracted from the locator at a plurality of different vertical positions of the locator relative to the electromagnetic field.
19. The calibration system of claim 11 and further comprising means connected to the extracting means for calculating corrective values and uploading the corrective values to the locator to thereby calibrate the locator.
20. A locator calibration system, comprising:
a frame that supports a portable locator;
at least one coil that generates an electromagnetic field around the locator when a suitable signal is applied to the coil;
a motor assembly capable of rotating the locator;
a sensor that outputs a signal representative of a rotational position of the locator relative to the magnetic field; and
a computer interface that enables a computer to sample a plurality of field strength samples from the locator at each of a plurality of different rotational positions of the locator, calculate at least one corrective value, and upload the corrective value to the locator to calibrate the locator.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A semiconductor memory device having a semiconductor substrate, comprising:
a field oxide film which is formed to a forward taper shape on the semiconductor substrate, and
a floating gate which is formed to a reverse taper shape between the field oxide film over the semiconductor substrate,
wherein sidewall angle is less than 90 degrees in the forward taper shape while sidewall angle is more than 90 degrees in the reverse taper shape.
2. A device as claimed in claim 1, wherein:
a tunnel oxide film is formed between the floating gate and the semiconductor substrate.
3. A device as claimed in claim 1, wherein:
the semiconductor substrate comprises a p-type silicon substrate.
4. A device as claimed in claim 1, wherein:
the field oxide film has a thickness within a range between 300 nm and 500 nm.
5. A device as claimed in claim 1, wherein:
the tunnel oxide film has a thickness within a range between 8 nm and 10 nm.
6. A device as claimed in claim 1, wherein:
a word line is formed via an insulating film on the floating gate.
7. A device as claimed in claim 1, wherein:
the semiconductor memory device comprises a flash memory.
8. A method of manufacturing a semiconductor memory device on a semiconductor substrate, comprising the steps of:
depositing a first oxide film on the semiconductor substrate;
forming a field oxide film in the first oxide film such that a plurality of grooves extend in a predetermined direction and exposes the semiconductor substrate, the field oxide film having a forward taper shape;
depositing a second oxide film having on the exposed semiconductor substrate; and
forming a floating gate to a reverse taper shape between the field oxide film on the second oxide film,
wherein sidewall angle is less than 90 degrees in the forward taper shape while sidewall angle is more than 90 degrees in the reverse taper shape.
9. A method as claimed in claim 8, wherein:
the semiconductor substrate comprises a p-type silicon substrate.
10. A method as claimed in claim 8, wherein:
the first oxide film has a thickness within a range between 300 nm and 500 nm.
11. A method as claimed in claim 8, wherein:
the field oxide film is deposited by the use of anisotropic etching.
12. A method as claimed in claim 8, wherein:
the second oxide film comprises a tunnel oxide film formed by the use of a thermal oxidation method, and
the tunnel oxide film has a thickness within a range between 8 nm and 10 nm.
13. A method as claimed in claim 8, wherein:
the floating gate is formed by burying polysilicon in the groove with a film thickness of the field oxide film or thicker, and by removing the buried polysilicon with a predetermined film thickness.
14. A method as claimed in claim 13, wherein:
the polysilicon is buried by the use of a CVD method.
15. A method as claimed in claim 13, wherein:
the polysilicon is removed by the use of a CMP method.
16. A method as claimed in claim 13, wherein:
the polysilicon is removed by the use of a dry-etching method.
17. A method as claimed in claim 8, wherein:
the floating gate is formed in a self-alignment manner with the field oxide film.