Method for the solid phase crystallisation of an amorphous layer
A method for crystallising an amorphous layer included in a stack, extending directly in contact with a crystalline layer of the stack by forming an interface with the crystalline layer, and having a first face opposite the interface, and having a melting threshold E M corresponding to the energy density to be provided to the amorphous layer to achieve its melting, for a thickness Ep of the amorphous layer defined between the first face and the interface, the method including a crystallisation annealing of the amorphous layer by subjecting it, by zones, to laser pulses, and in each zone, the laser pulses are emitted by series, each laser pulse having an energy density ED i different from one series to another so as to maintain the energy density of the pulses of each series below the melting threshold.
1 . A method for crystallizing at least a portion of an amorphous layer based on a first material, the amorphous layer being included in a stack that further comprises a crystalline layer, the amorphous layer extending in direct contact with the crystalline layer so as to define an interface with the crystalline layer, the amorphous layer having a first face opposite the interface, and the amorphous layer having a melting threshold energy density E M corresponding to an energy density required to melt the first material for a thickness Ep of the amorphous layer defined between the first face and the interface, the method comprising:
performing a crystallization annealing of the amorphous layer by subjecting the amorphous layer, zone by zone to laser pulses,
wherein, in each zone, the laser pulses are emitted in a plurality of series of pulses, each series having pulse energy density ED i , the pulse energy density ED i differing from one series to another, and
wherein, for each of the series, the pulse energy density ED i is maintained below the melting threshold energy density E M , the melting threshold energy density E M evolving as the amorphous layer crystallizes.
2 . The method according to claim 1 , wherein the pulse energy density ED i of each of the series satisfies: ED i <E M −8%×E M .
3 . The method according to claim 1 , wherein the pulse energy density ED i of each of the series satisfies: ED i ≥E M −20%×E M .
4 . The method according to claim 1 , further comprising, prior to the crystallization annealing, performing a first implantation configured to dope the amorphous layer by implanting dopants into the amorphous layer.
5 . The method according to claim 4 , further comprising, prior to the crystallization annealing, performing a second implantation configured to form the amorphous layer by implanting heavy ions into the amorphous layer.
6 . The method according to claim 5 , wherein the second implantation is performed before the first implantation for doping the amorphous layer.
7 . The method according to claim 1 , wherein an initial thickness of the amorphous layer is greater than 20 nm.
8 . The method according to claim 1 , wherein at least one of the first material and a material forming the crystalline layer is selected from a group including Si, SiGe, Ge, SiC, GeSn and diamond.
9 . The method according to claim 1 , wherein each of the series of laser pulses comprises between 1 and 1000 laser pulses.
10 . The method according to claim 1 , wherein a difference δED in pulse energy density ED i between successive series is between 5 mJ/cm 2 and 100 mJ/cm 2 .
11 . The method according to claim 1 , wherein a time interval between two successive laser pulses applied to a same zone is selected such that the stack substantially returns to a temperature present before receipt of a first of the two successive laser pulses.
12 . The method according to claim 1 , wherein a time interval between two successive laser pulses applied to a same zone is at least 1 ms.
13 . The method according to claim 1 , wherein the laser pulses have a wavelength located in a ultraviolet spectral domain, the wavelength being selected from a group including 293 nm, 308 nm, and 355 nm.
14 . The method according to claim 1 , wherein a duration of each of the laser pulses is less than or equal to 3000 ns.
15 . The method according to claim 1 , wherein the stack is included in a microelectronic or nanoelectronic structure.