### 6.3.4 Summary to: 6.4 Physical Processes for Layer Deposition

| Sputter Deposition |  |
|  | Simple in principle: Shoot off any mixture of atom contained in a target be an ion beam produced by applying high (RF) voltage between target and Si wafer; see picture. |
|  | Great advantage is easy deposition of mixtures of elements, e.g. Al plus traces of Cu etc. |
|  | Disadvantage: 1. target should be conducting; no (easy) deposition of insulators like SiO2. Target atoms are emitted in all directions, leading to: |
| "Contact hole filling problem" |  |
|  | The picture tells it all. At some point you need to go back to CVD processes. |
| Ion implantation. Might be considered to be a "deposition" technique but actually shoots ions into the Si target. |
|  | The technique of choice for doping selected areas with typically B, As or P.. Depth distribution and concentrations finely adjustable in a wide range. |
|  | Major problems: 1. The Si crystals gets more or less destroyed; in the extreme it turns amorphous. Implantation thus always need a follow-up annealing process that changes dopant distribution by diffusion and may not be able to restore perfectness of the lattice 2. Implanters are huge, complex and very expensive machines. |
| Other physical deposition techniques. There are plenty, often quite specialized. Of special important for chip making are. |  |
|  | Evaporations. Easy but very limited. Rarely used in chip production |  |
|  | Spin-on techniques (for deposition the light sensitive "resist" needed for lithography |  |
|  | Molecular Beam Epitaxy (MBE);: hugely important for III-V technology. Galvanic techniques. Hated but used Many other. |  |
Questionaire
Multiple Choice questions to all of 6.4

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