Photolithography of atomic layer resist
In a method of atomic precision advanced manufacturing (APAM), an atomic or molecular resist layer on a substrate surface is selectively depassivated by locally exciting the substrate surface with an optical beam effective to eject adsorbed atoms or molecules from the substrate surface. The substrate surface is further processed by exposing it to a precursor gas, decomposing the precursor gas to release a dopant, and incorporating the dopant into the substrate surface.
1. A method, comprising:
passivating a substrate surface with an atomic or molecular resist species;
selectively depassivating the substrate surface;
exposing the substrate surface to a precursor gas; and
decomposing the precursor gas to release a dopant and incorporating the dopant into the substrate surface,
wherein the selective depassivating comprises locally exciting the substrate surface with an optical beam effective to eject adsorbed resist atoms or molecules from the substrate surface using photothermal heating.
2. The method of claim 1 , wherein the exposing of the substrate surface to the precursor gas is performed after the selective depassivating of the substrate surface.
3. The method of claim 1 , wherein the exposing of the substrate surface to the precursor gas is performed concurrently with the selective depassivating of the substrate surface.
4. The method of claim 1 , wherein the exposing of the substrate surface to the precursor gas is performed concurrently with the selective depassivating of the substrate surface, and wherein the exposing to the precursor gas is performed by flowing precursor gas into a vacuum chamber that contains the substrate.
5. The method of claim 1 , wherein the decomposing of the precursor gas and the incorporating of the dopant into the substrate surface are performed, at least in part, by heating the substrate.
6. The method of claim 1 , wherein the local exciting of the substrate surface with an optical beam comprises impinging the surface of a semiconductor substrate with laser light that is optically absorbed by the semiconductor substrate.
7. The method of claim 1 , wherein the local exciting of the substrate surface with an optical beam is performed by impinging at least one wavelength of light onto the substrate surface that causes photothermal heating of the substrate surface.
8. The method of claim 1 , wherein the substrate surface is a silicon surface.
9. The method of claim 1 , wherein the dopant is phosphorus and the precursor gas is phosphine.
10. The method of claim 1 , wherein the substrate surface is a surface of a semiconductor, and the semiconductor is selected from the group consisting of silicon, germanium, and silicon-germanium alloys.
11. The method of claim 1 , wherein the precursor gas is selected from the group consisting of phosphine, arsine, boron trichloride, and diborane.
12. The method of claim 1 , wherein the local exciting of the substrate surface with an optical beam comprises impinging the substrate surface with laser pulses.
13. The method of claim 1 , wherein the local exciting of the substrate surface with an optical beam comprises impinging the substrate surface with laser pulses, and wherein the method further comprises controlling a pulse energy of the laser pulses to lie between a predetermined threshold for depassivation and a predetermined threshold for surface damage.
14. The method of claim 1 , wherein the local exciting of the substrate surface with an optical beam employs a driven through focus process.
15. The method of claim 14 , wherein the driven through focus process employs a linear rate of approximately 20 μm/s.
16. The method of claim 14 , wherein the driven through focus process employs a pulse repetition rate of approximately 20 Hz.