Method of epitaxially growing silicon by atomic layer deposition for TFT flash memory cell
A method of growing an epitaxial silicon layer is provided. The method comprising providing a substrate including an oxygen-terminated silicon surface and forming a first hydrogen-terminated silicon surface on the oxygen-terminated silicon surface. Additionally, the method includes forming a second hydrogen-terminated silicon surface on the first hydrogen-terminated silicon surface through atomic-layer deposition (ALD) epitaxy from SiH 4 thermal cracking radical assisted by Ar flow and flash lamp annealing continuously. The second hydrogen-terminated silicon surface is capable of being added one or more layer of silicon through ALD epitaxy from SiH 4 thermal cracking radical assisted by Ar flow and flash lamp annealing continuously. In one embodiment, the method is applied for making devices with thin-film transistor (TFT) floating gate memory cell structures which is capable for three-dimensional integration.
1. A method of growing an epitaxial silicon layer, the method comprising:
providing a substrate including an oxygen-terminated silicon surface;
performing a hydrogenation process to replace the oxygen-terminated silicon surface with a hydrogen-terminated silicon surface, the hydrogen-terminated silicon surface having a single Si—H bond for each surface silicon atom;
forming a first layer of silicon with a hydrogen-terminated surface on the hydrogen-terminated silicon surface by breaking the Si—H bond through atomic-layer deposition (ALD) epitaxy from SiH 4 thermal cracking radical assisted by Ar flow and flash lamp annealing continuously, the hydrogen-terminated surface having two Si—H bonds for each surface silicon atom; and
subsequently forming second or more layers of silicon with a hydrogen terminated surface through ALD epitaxy from SiH 4 thermal cracking assisted by Ar flow and flash lamp annealing continuously, the H-termination of the subsequent second or more atomic layers of silicon having two S—H bonds for each surface silicon atom.
2. The method of claim 1 wherein the substrate including an oxygen-terminated silicon surface comprises a silicon oxide surface.
3. The method of claim 1 wherein the substrate including an oxygen-terminated silicon surface comprises an insulation layer on active devices.
4. The method of claim 1 wherein performing the hydrogenation process comprises using hydrogen plasma and/or annealing with H radical supplied.
5. The method of claim 1 wherein SiH 4 thermal cracking produces SiH 2 radical capable of bonding a surface silicon atom of the first and subsequent second or more layers of silicon which has a broken Si—H bond induced by Ar flow.
6. The method of claim 1 wherein forming the layers of silicon comprises a doping process by thermal cracking certain impurity gas mixed with SiH 4 .
7. The method of claim 1 further comprising annealing the epitaxial silicon layer after deposition.
8. The device of claim 1 wherein the epitaxial silicon layer is undoped.
9. The device of claim 1 wherein the epitaxial silicon layer is lightly p-type doped and capable of forming a p-channel of a TFT with a N+ polysilicon source or drain region.
10. The device of claim 8 wherein the undoped epitaxial silicon layer is capable of forming a floating gate.