Phosphorus and boron implantation in 6H–SiC

Abstract

Comparison of the annealing behavior of high-dose nitrogen-, aluminum-, and boron-implanted 4H-SiC Appl.Phosphorus and boron ion implantations were performed at various energies in the 50 keV-4 MeV range. Range statistics of P ϩ and B ϩ were established by analyzing the as-implanted secondary ion mass spectrometry depth profiles. Anneals were conducted in the temperature range of 1400-1700°C using either a conventional resistive heating ceramic processing furnace or a microwave annealing station. The P implant was found to be stable at any annealing temperature investigated, but the B redistributed during the annealing process. The implant damage is effectively annealed as indicated by Rutherford backscattering measurements. For the 250 keV/1.2ϫ10 15 cm Ϫ2 P implant, annealed at 1600°C for 15 min, the measured donor activation at room temperature is 34% with a sheet resistance of 4.8ϫ10 2 ⍀/ᮀ. The p-type conduction could not be measured for the B implants.

Donor ion-implantation doping into SiC

“…It is well known that the stoichiometric disturbances caused by ion-implantation in compound semiconductors are in the form of lattice vacancies at the surface. 20,27,28 The concentration of vacancies at the surface increases with the atomic mass of the implant species. Since As and Sb are heavier than N and P, the concentration of Si and C vacancies at the surface is greater than the peak-implant concentration.…”

“…These were developed by using secondary ion mass spectrometry (SIMS) experimental results published by us earlier. 11,20 Validity of these empirical formulas is checked by fitting the experimental SIMS profiles using the Pearson IV distribution function and the range statistics obtained from the empirical formulas. It has been observed that the skewness and kurtosis are necessary for accurate modeling of the implant distribution.…”

Al, B, and Ga ion-implantation doping of SiC

“…Lattice damage that occurs in SiC during implantation can be minimized by performing ion implantation at a high temperature, around 800°C. [15][16][17] While aluminum implants in SiC have been found to be stable during annealing, [18][19][20] substantial dopant re-distribution of boron 10 and gallium 21 has been observed during annealing leading to dopant loss or gettering at the SiC surface as a result of Si evaporation from the lattice. Additionally, degradation of the surface leads to an increase in the number of surface traps and an unwanted decrease in carrier mobility in surface channel regions.…”

“…Extensive research has been performed on donor implants such as nitrogen and phosphorus due to their low ionization energies and ease of electrical activation in SiC. [4][5][6][7] There are several reports on acceptor implantation in SiC [8][9][10][11][12] but more work needs to be done. Some of the issues that need more attention are high-energy (MeV) implantation to form deep junctions, activation of acceptor implants (especially at low doses), Ga implant behavior, and the stability of the SiC surface during high-temperature annealing, needed for activation of acceptor implants.…”

Ion Implantation Doping in SiC and its Device Applications

“…At present N and Al are widely used for donor and acceptor ion implantation doping in Sic, respectively, due to their low activation energies in S i c (-80 meV for N and 240 meV for Al in 6H-Sic) compared to other impurities of the same type. Recently, the P donor has been reported [ 11 to have almost the same activation energy ( -8 0 6 meV) with an electrical activation comparable to that of N for elevated temperature implants [2]. Using N or P dopants, the maximum obtainable carrier concentration at room temperature is limited to -10" cm3 [2-51. Since N occupies C sites and P occupies Si sites, implanting both N and P successively in S i c helps to obtain higher carrier concentrations by populating both Si and C vacancies with P and N atoms, respectively.…”