Method and apparatus for transferring a thin layer of semiconductor material

A method of transferring a thin layer of semiconductor material comprising:

• depositing a small amount of charged, light ions at a certain depth underneath the surface of a first semiconductor substrate wherein this first substrate is covered with an protective layer of a thickness smaller than the average penetration depth of the ions and the ion source is first kept at a high electrical potential with regards to the substrate, resulting in an acceleration of the ions towards the substrate, penetrating the the oxide layer and finally coming to rest at a certain depth underneath the surface and underneath the the oxide layer and the potential being in the range of 20 kV to 500 kV and preferably between 50 and 200 kV if the the substrate is a silicon wafer and the ion plasma density is controlled in such manner that the dose of ions deposited into the substrate is not less than 10exp13 but no more than 10exp 18 ions/cm2 and preferably about 10exp15 ions/cm2;
• and the ions are made from a light element such as H, D, He, Li, B, Ne, or Si such that the penetration depth is larger than the penetration depth of most other unwanted heavier elements that may be present in the ion source, and reach the surface with the same energy as the light elements;
• the temperature of the substrate is kept between 100 and 800K and is preferably controlled to be between 500 and 600K during this first implantation;
• in a second implantation stage the potential of the ion source is reduced to a very small potential with regards to said substrate and the element supplied to the plasma source is optionally switched to a second element which is preferably hydrogen or deuterium;
• the energy of these ions is adjusted such that said ions are stopped within said protective layer;
• the implantation dose is high to provide an excess of hydrogen for diffusion into the donor wafer and capture by the gettering sites provided by first implantation;
• said substrate is kept at a temperature between 300 and 800K and preferably between 500 an 600K such that the damage to the crystalline structure cause by deposition said first element will remain to a large degree and can act as trap for said second element while the diffusion of said second ions is fast enough to achieve economically feasible throughput;
• said protective layer is removed or reduced in thickness and the donor wafer is bonded to a second substrate, wherein the bonding strength of the composite structure is increased by annealing at a temperature between 400 and 600K as a first step followed by annealing at a temperature between 700 and 800K as a second step, which will form an internal, hydrogen rich layer at a depth determined by the deposition of first element and which is mechanically weakened by said second element such that the composite structure can be separated at this layer by adding an small amount of energy from thermal or mechanical stress, sound waves, infra-red radiation or other means;
• finishing the new structure by further annealing at higher temperature, preferably between 1000 and 1400K for a duration between 30 min and several hours;
• and finally smoothing the surface of this new structure by chemical mechanical polishing and cleaning in aqueous solutions of HF, alkaline and acidic chemicals followed by thorough rinsing and drying.