1. A method for dividing ions in a gas according to their mobility, comprising:
forming a supersonic gas jet, having gas molecules with substantially equal velocities, by directing the gas through a Laval nozzle into an evacuated chamber;
forming a field barrier, having a substantially uniform height across a cross-section of the supersonic gas jet, by respectively applying potentials U2, U3 and U4 to an arrangement of three apertured diaphragms R2, R3 and R4, which are respectively separated by distances d2 and d3, where (U4\u2212U3)(U3\u2212U2)=d3d2; and
directing the ions in the supersonic gas jet against the field barrier, where ions with a mobility less than a mobility threshold are pushed over the field barrier, and where ions with a mobility higher than the mobility threshold are held back by the field barrier.
2. The method of claim 1, where the apertured diaphragms R2, R3 and R4 have substantially equal aperture diameters.
3. The method of claim 1, further comprising measuring an ion current of the ions pushed over the field barrier.
4. The method of claim 3, further comprising performing the measuring of the ion current with an ion detector without mass separation.
5. The method of claim 3, further comprising performing the measuring of the ion current with a mass analyzer.
6. The method of claim 4, further comprising:
providing a continuous current of the ions from an ion source;
pushing the ions with mobility less than the mobility threshold over the field barrier with the supersonic gas jet;
measuring passing ions in the form of a total ion current curve as a function of the height of the field barrier; and
generating a mobility spectrum by differentiating the total ion current curve.
7. The method of claim 5, further comprising:
providing a continuous current of the ions from an ion source;
pushing the ions with mobility less than the mobility threshold over the field barrier with the supersonic gas jet;
measuring a series of mass spectra of passing ions as a function of the height of the field barrier;
extracting ion current curves for ions of individual mass ranges from the mass spectra; and
generating mass separated mobility spectra by differentiating the ion current curves.
8. The method of claim 7, further comprising:
setting the height of the field barrier to measure fragment ion spectra of ions with lowest mobility; and
lowering the field barrier to measure mixtures of ions of the lowest mobility and ions of higher mobility.
9. An ion mobility spectrometer, comprising:
an ion source that generates ions in a gas in a high pressure region of the ion mobility spectrometer;
a Laval nozzle that generates a supersonic gas jet from the gas with the ions in a lower pressure region of the ion mobility spectrometer;
an arrangement of three or more apertured diaphragms R2, R3 and R4 through which the supersonic gas jet moves axially, where the apertured diaphragms are respectively separated by distances d2 and d3;
a power supply that respectively supplies the apertured diaphragms with potentials U2, U3 and U4, where (U4\u2212U3)(U3\u2212U2)=d3d2; and
an ion detector that measures a current of the ions passing the apertured diaphragms.
10. The ion mobility spectrometer of claim 9, where the Laval nozzle is located between a region maintained at atmospheric pressure and a first vacuum chamber, or in a wall located between two vacuum chambers of a differential pumping system.
11. The ion mobility spectrometer of claim 9, further comprising an additional RF quadrupole rod system located between the Laval nozzle and the arrangement of apertured diaphragms.
12. The ion mobility spectrometer of claim 9, where the ion detector comprises a mass spectrometer.
13. The ion mobility spectrometer of claim 12, where the mass spectrometer comprises a time-of-flight mass spectrometer with orthogonal ion injection.
14. An ion mobility spectrometer, comprising:
an ion source that generates ions in a gas in a high pressure region of the ion mobility spectrometer;
a Laval nozzle that generates a supersonic gas jet from the gas with the ions in a lower pressure region of the ion mobility spectrometer;
a coaxial arrangement of three or more apertured diaphragms R2, R3 and R4 through which the supersonic gas jet axially moves;
a power supply that respectively supplies the apertured diaphragms with potentials U2, U3 and U4 such that a field barrier is generated at the apertured diaphragm R4 having a substantially uniform height across a cross-section of the supersonic gas jet, and such that ions in the supersonic gas jet are directed against the field barrier, where ions with a mobility less than a mobility threshold are pushed over the field barrier, and where ions with a mobility higher than the mobility threshold are held back by the field barrier; and
an ion detector that measures a current of the ions passing the apertured diaphragms.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for detecting soft errors in an integrated circuit (IC) due to transient-particle emission, the IC comprising at least one chip and a substrate, the method comprising:
mixing an epoxy with a radioactive source to form a hot underfill (HUF);
underfilling the chip with the HUF;
sealing the underfilled chip;
measuring a radioactivity of the HUF at an edge of the chip;
measuring the radioactivity of the HUF on a test coupon;
testing the IC for soft errors by determining a current radioactivity of the HUF at the time of testing based on the measured radioactivity; and
after completion of testing the IC for soft errors and after the expiration of a radioactive decay period of the radioactive source, using the IC in a computing device by an end user.
2. The method of claim 1, wherein the radioactive source comprises one of 210 lead (Pb); 210 pollonium (Po); a combination of 210 Pb and 210 Po; 225 actinium (Ac); and 223 radium (Ra).
3. The method of claim 1, wherein the radioactive decay period is equal to about 12 times a half life of the radioactive source.
4. The method of claim 1, further comprising treating the chip with an oxygen plasma treatment before underfilling the chip with the HUF.
5. The method of claim 1, further comprising vacuum degassing the HUF after mixing.
6. The method of claim 1, wherein underfilling the chip with the HUF comprises dispensing the HUF at a leading edge of the chip.
7. The method of claim 6, further comprising forming a barrier comprises a thixotropic, non-radioactive material at the leading edge of the chip to contain the HUF under the chip.
8. The method of claim 6, further comprising placing a glass slide at the leading edge of the chip to contain the HUF under the chip.
9. The method of claim 1, wherein sealing the underfilled chip comprises:
applying a first cold underfill (CUF) over the HUF at an edge of the chip;
applying a second CUF over the first CUF;
determining an alpha count of the HUF, and in the event the alpha count is above a predetermined limit, applying a third CUF over the second CUF;
wherein the first, second, and third CUF each comprise an epoxy.
10. The method of claim 1, wherein the HUF further comprises a fluorescent dye, and further comprising detecting a portion of HUF that is not located under the chip using a fluorescent light after sealing the underfilled chip.
11. The method of claim 1, further comprising determining whether a void is present in the HUF under the chip before testing the IC for soft errors; and
in the event it is determined that a significant void is not present, testing the IC for soft errors; and
in the event it is determined that a significant void is present, discarding the chip.
12. The method of claim 1, wherein determining whether a void is present in the HUF under the chip comprises at least one of acoustic microscopy or two-dimensional beta radiation detection.
13. A system for detecting soft errors in an integrated circuit (IC) due to transient-particle emission, the IC comprising at least one chip and a substrate, the system comprising:
a hot underfill (HUF) located under the chip, the HUF comprising an epoxy mixed with a radioactive source;
a first cold underfill (CUF) located over the HUF at an edge of the chip; and
a second CUF located over the first CUF, wherein the first CUF and the second CUF comprise an epoxy;
wherein the IC is located on a circuit board that is for use by an end user in a computing device after completion of testing the IC for soft errors and after an expiration of a radioactive decay period of the radioactive source.
14. The system of claim 13, wherein the radioactive source comprises one of 210 lead (Pb); 210 pollonium (Po); a combination of 210 Pb and 210 Po; 225 actinium (Ac); and 223 radium (Ra).
15. The system of claim 13, wherein the HUF further comprises a fluorescent dye.
16. The system of claim 13, further comprising a third CUF located over the second CUF, the third CUF comprising an epoxy.
17. The system of claim 13, further comprising forming a barrier comprises a thixotropic, non-radioactive material at the leading edge of the chip to contain the HUF under the chip.
18. The system of claim 17, further comprising placing a glass slide at the leading edge of the chip to contain the HUF under the chip.
19. The system of claim 13, wherein a surface of the chip is cleaned with an oxygen plasma treatment.
20. The system of claim 13, wherein the radioactive decay period is equal to about 12 times a half life of the radioactive source.