Methods for fabricating semiconductor devices having reduced implant contamination
View Patent ↗A method of fabricating a semiconductor device includes selecting an element for implanting into a substrate. The element has at least a first isotope and a second isotope. At least one implant contaminant is identified as having a particle weight that is substantially identical to an atomic weight of the first isotope of the element. As such, ions of the second isotope of the element are selectively implanted into a region of the substrate. The second isotope has an atomic weight that is different from the particle weight of the at least one implant contaminant. For example, the selected element may be silicon (Si), the implant contaminant may be nitrogen (N 2 ), the first isotope having the substantially identical atomic weight may be silicon-28, and the second isotope having the different atomic weight may be silicon-29. Related methods, apparatus, and devices are also discussed.
1. A method of fabricating a semiconductor device, the method comprising:
selecting an element for implanting into a substrate, the element having at least a first isotope and a second isotope;
identifying a presence of at least one implant contaminant by comparing a theoretical isotope ratio for the element to an actual isotope ratio for the element calculated from beam current measurements of the isotopes of the element generated during an ionization process; and
selectively implanting ions of the second isotope of the element into a region of the substrate responsive to identifying the presence of the at least one implant contaminant, wherein the first isotope has an atomic weight that is substantially identical to a particle weight of the at least one identified implant contaminant, and wherein the second isotope has an atomic weight that is different from the particle weight of the at least one implant contaminant.
2. The method of claim 1 , wherein the first isotope comprises a more naturally abundant isotope of the element, and wherein the second isotope comprises a less naturally abundant isotope of the element.
3. The method of claim 1 , wherein the selected element comprises silicon (Si), and wherein the substrate comprises a Group-III nitride.
4. The method of claim 3 , wherein the at least one implant contaminant comprises nitrogen (N 2 ), wherein the first isotope comprises silicon-28, and wherein the second isotope comprises silicon-29 or silicon-30.
5. The method of claim 3 , wherein the at least one implant contaminant comprises boron fluoride (BF), wherein the first isotope comprises silicon-30, and wherein the second isotope comprises silicon-29.
6. The method of claim 1 , further comprising:
verifying an ion concentration of the implanted region of the substrate based on the atomic weight of the second isotope that is different from the particle weight of the implant contaminant.
7. The method of claim 6 , wherein verifying the ion concentration comprises:
detecting a presence of silicon-29 ions in the implanted region of the substrate using mass spectrometry.
8. A method of implanting silicon (Si) ions into a gallium nitride (GaN) substrate, the method comprising:
generating a plurality of silicon ions comprising silicon-28 ions, silicon-29 ions, and/or silicon-30 ions from an ion source;
identifying at least one implant contaminant having a particle weight that is substantially identical to an atomic weight of at least one isotope of silicon by comparing a theoretical isotope ratio for silicon to an actual isotope ratio for silicon calculated from beam current measurements using the plurality of silicon ions generated from the ion source;
identifying silicon-29 as an isotope of silicon having an atomic weight different from the particle weight of the at least one implant contaminant; and
selectively implanting the silicon-29 ions into a region of the gallium nitride substrate responsive to identifying the implant contaminant.
9. The method of claim 8 , wherein generating the plurality of silicon ions comprises:
ionizing a solid and/or a gas containing silicon to produce the plurality of silicon ions comprising silicon-28 ions, silicon-29 ions, and/or silicon-30 ions.
10. The method of claim 9 , wherein selectively implanting comprises:
accelerating the plurality of silicon ions to a predetermined energy;
isolating the silicon-29 ions from the plurality of silicon ions and/or the at least one implant contaminant; and
directing the silicon-29 ions to the region of the substrate.
11. The method of claim 10 , wherein isolating the silicon-29 ions comprises:
adjusting an ion beam comprising the plurality of silicon ions to isolate the silicon-29 ions therefrom.
12. The method of claim 11 , wherein adjusting the ion beam comprises:
altering a magnetic field applied to the plurality of silicon ions to separate the silicon-28 and silicon-30 ions from the silicon-29 ions.