vlsi annealing and masking
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The document discusses annealing and characterization of doped layers created through ion implantation. It covers: 1) Annealing repairs implant damage and makes dopants electrically active by recrystallization at 500-600°C or activation at 600-900°C. It affects conductivity, mobility, and lifetime. 2) Annealing classes include pre-amorphized below 600°C and no pre-amorphization above 800-950°C. 3) Masking during implantation leads to a Gaussian dopant profile below the mask. Thicker masks block more dopants. Characterization involves measuring junction depth through techniques like lapping and staining or interference fringes, and determining the doping distribution using SIM
vlsi annealing and masking
- 1. Annealing of damages created by Ionimplantations & Masking during Implantation + characterization of doped layers Presented By : M.Vikas Vardhan Reddy M.Tech in Computational Engg. ID:B61301007 9492634651 mvvr09402@gmail.com
- 2. Annealing and its use… Process of repairing implant damage (i.e., “healing” the surface) is called annealing .Also puts dopant atoms in substitutional sites where they will be electrically active 2 objectives of annealing: 1) healing, recrystallization (500 - 600 oC) 2) renew electrical activity (600 - 900 oC) parameters that get most affected are conductivity, the mobility and the life time. Region of maximum damage? Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 3. Annealing Classes Divided into two classes(based on type of material) they are 1. 2. Pre-amorphised No pre-amorphised Pre-amorphised T<=600 degrees centigrade T<=400 degrees centigrade 1. Partial recovery(clusters disappear) 2. 20% to 30% activation Recovery life time is extreme low 3. 1. Recrystallization takes place 2. 50% to 90% activation 3. Recovery life time is low T>=950 degrees centigrade 1. Fast recovery Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 4. No Pre-amorphisation Low dose , light ion implantation, we can fully recover of all the parameters ,conductivity, mobility, as well as life time by 800 to 950 degree centigrade. Heavy ion implantation, low dose we can fully recover of all the parameters by 1000 degree centigrade. It is difficult to get full activation for high dose heavy ion implantation. if the life time recovery is not very important than pre amorphisation is better than not pre amorphisation material.(at 600c we get 90% activation) Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 5. Practical cases… Phosphorous in silicon Boron in silicon Arsenic in silicon Phosphorous in silicon Phosphorus is a relatively heavy ion, so it loses its energy primarily by the nuclear stopping mechanism Projected range proportional to incident energy lot of energy to put phosphorus deep into the silicon Rp=1.1 μm/M ev. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 6. Annealing of phosphorus and arsenic As the temperature increases the carrier activation increases till eventually at a point it sort of acquires full activation or let us say, 90% of activation. arsenic in silicon, arsenic also behaves in a manner very similar to that of phosphorus. Rp=0.58 μm/M ev. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 7. Annealing of boron boron is a light ion Rp=3.1 μm/M ev. for boron, for the incident energy range in 10 to 100 kilo electron volt Annealing behavior of Boron. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 8. Masking during Implantation + characterization of doped layers
- 9. Masking in ion implantation Ion implantation is a room temperature process and therefore you have a larger choice of mask material. You do not have to use silicon dioxide always, like in case of diffusion. Ion implantation can use photoresist as the mask Silicon and mask layer generate energic ions when ion beam is incident on semiconductor and these energy ions will have Gaussian principle. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 10. Gaussian profile d is the masking layer thickness. If d is large less impurity is put inside silicon If d is less large amount of impurity is put inside silicon Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 11. Masking layer efficiency Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 12. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 13. Amount of impurity not protected by mask Practical case Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 14. Evaluation of doped layer Junction depth Doping profile Junction depth Junction depth is measured by lapping and straining Cylindrical groove technique Interference fringe method Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 15. Junction depth by lapping and straining Angled lapping Cross sectional diagram of the junction Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 16. Cylindrical groove method Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 17. Interference fringe method Third method to find the junction depth Lapped sample Provide optical flat and subject to monochromatic radiation usually sodium vapour lamp. Dull fringes appear in p region and we can count it. Now junction depth=no.of dull fringes * wavelength of monochromatic light. Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 18. Doping distribution doping distribution, the impurity distribution. Now we can measure the total impurity distribution by doing spectroscopy analysis like SIMS, Secondary Ion Mass Spectroscopy, which will tell us exactly how much impurity is put inside the material. But, it will not tell us whether this impurity is electronically active or not, whether it is sitting in the substitutional site or it is just sitting anywhere inside the semiconductor Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers 12/14/2013
- 19. Thank you
Editor's Notes
- #2: Good morning to one and all. I am Vikas Vardhan Reddy Persuing M.Tech first year in RGUKT. Now Iam going to give presentation on Annealing of damages created by Ion-implantations & Masking during Implantation + characterization of doped layers
- #3: After ion implantation conductivity is very Low and electronic activity is minimum. The region become semi Insulating. Mobility is low. So we have to get back the required levels of conductivity, the mobility and the life time. In order to anneal out the damages, the semiconductor must be subjected to high temperature . Damage is created mostly by nuclear stopping mechanism.
- #5: For low dose ,light ion the damages are much less. heavy ions still with low dose,you will get back about 1000 degree centigrade, will give you recovery of all the parameters.
- #6: E 0=1.1 micrometer per mega electron volt, per thousand kilo electron volt. That means if you have 100 kilo electron volt energy, R p will be 0.11 micrometer.
- #7: relative active carrier concentration that is n/ⱷ versus the annealing temperature. ⱷ is the total dose, n is active carrier concentration. annealing schedule depends entirely on the dose, the lighter dose gets annealed faster, the heavier dose gets annealed later.
- #8: if the incident energy is greater than 100 kilo electron volt, then nuclear stopping will no longer dominate. It will be dominated by electronic stopping and in that case R p will be no longer proportional to the energy, but it will be proportional to the square root of energy.
- #9: Masking during Implantation + characterization of doped layers
- #10: Diffusion by contrast, is a high temperature process; therefore you must use a masking material that can withstand this high temperature.
- #11: Q0 that is the total dose.
- #16: Angled lappingprovides an ease of measurement. You are visually magnifying the junction area. Strain it by using a copper sulphate and dilute HF solution.Dilute HF will etch the surface oxide .now under microscope we can measure the junction depth
- #17: A cylinder with particular a radius R and it is used to grind a groove the semiconductor. Destructive technique