Laser annealing for 3-D chip integration
View Patent ↗A laser annealing method for annealing a stacked semiconductor structure having at least two stacked layers is disclosed. A laser beam is focused on a lower layer of the stacked layers. The laser beam is then scanned to anneal features in the lower layer. The laser beam is then focused on an upper layer of the stacked layers, and the laser beam is scanned to anneal features in the upper layer. The laser has a wavelength of less than one micrometer. The beam size, depth of focus, energy dosage, and scan speed of the laser beam are programmable. Features in the lower layer are offset from features in the upper layer such that these features do not overlap along a plane parallel to a path of the laser beam. Each of the stacked layers includes active devices, such as transistors. Also, the first and second layers may be annealed simultaneously.
1. A method for laser annealing a stacked semiconductor structure having at least two stacked layers, comprising the steps of:
focusing a first laser beam on a lower layer of the stacked layers;
scanning the first laser beam to anneal features in the lower layer;
focusing a second laser beam on an upper layer of the stacked layers; and
scanning a second laser beam to anneal features in the upper layer.
2. The method according to claim 1 , wherein the laser for the first and second laser beams has a wavelength of less than one micrometer.
3. The method according to claim 1 , wherein spot size, depth of focus, and energy density of the first and second laser beams are programmable.
4. The method according to claim 1 , wherein the scanning speed of the first and second laser beams is programmable.
5. The method according to claim 1 , wherein features in the lower layer are offset from features in the upper layer such that these features do not overlap along a plane parallel to a path of the first and second laser beams.
6. The method according to claim 1 , wherein the first and second laser beams are originated from a single laser.
7. The method according to claim 1 , wherein the first and second laser beams are respectively originated from separate lasers.
8. The method according to claim 1 , wherein each of the stacked layers includes an active device, a passive device, or a combination thereof.
9. The method according to claim 8 , wherein at least one of the devices is a transistor.