Annealing Al/Si contact increases resistance?

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SUMMARY

The discussion centers on the unexpected increase in resistance observed in Al/Si contacts after annealing p-type doped silicon with aluminum. The user performed 2-point probe measurements, noting a resistance increase of approximately three orders of magnitude following a one-hour annealing process. This contradicts the common expectation that annealing would reduce resistance and improve the linearity of the I-V curve. The potential cause identified is the diffusion of aluminum into the silicon, which acts as a donor, possibly leading to increased resistance.

PREREQUISITES
  • Understanding of p-type doping in silicon
  • Familiarity with aluminum as a contact material
  • Knowledge of photolithography techniques
  • Experience with 2-point probe measurement methods
NEXT STEPS
  • Research the effects of aluminum diffusion in silicon
  • Learn about the principles of ohmic contacts in semiconductor devices
  • Investigate the role of annealing in semiconductor processing
  • Explore techniques for minimizing contamination during aluminum deposition
USEFUL FOR

This discussion is beneficial for materials scientists, semiconductor engineers, and researchers involved in the fabrication of electronic devices, particularly those working with aluminum contacts on silicon substrates.

Hyo X
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I'm trying to make an ohmic contact with p-type doped silicon. Using Aluminum.
Under what condition of an Al/Si contact would annealing increase the resistance of the contact? or the silicon?
two regions are defined using photolithography. A brief exposure to buffered oxide etch (6:1 H2O to HF) is followed by placing the sample in a vacuum chamber and, several hours later, with aluminum depostion.
Initially, 2-pt probe measurements from two separated aluminum regions were somewhat non-linear.
After annealing the sample, for 1 hr, the resistance increased by ~3 orders of magnitude!
I would have thought that annealing would decrease the resistance and increase the linearity of the i-v curve.
What is the problem? is there contamination or some other issue? thanks for your help or opinion.
 
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Hyo X said:
I'm trying to make an ohmic contact with p-type doped silicon. Using Aluminum.
Under what condition of an Al/Si contact would annealing increase the resistance of the contact? or the silicon?
two regions are defined using photolithography. A brief exposure to buffered oxide etch (6:1 H2O to HF) is followed by placing the sample in a vacuum chamber and, several hours later, with aluminum depostion.
Initially, 2-pt probe measurements from two separated aluminum regions were somewhat non-linear.
After annealing the sample, for 1 hr, the resistance increased by ~3 orders of magnitude!
I would have thought that annealing would decrease the resistance and increase the linearity of the i-v curve.
What is the problem? is there contamination or some other issue? thanks for your help or opinion.
You could have diffusion of aluminium into the silicon. Aluminium would be a donor in silicon.
 

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