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Annealing behaviors of residual defects in high-dose BF+2-implanted (001)Si under different implantation conditions
Nuclear Instruments North-Holland
and Methods
in Physics
Research
193
B55 (1991) 193-197
Annealing behaviors of residual defects in high-dose BF,f -implanted (001) Si under different implantation conditions C.H. Chu a,l, E.L. Tsai a, W.Y. Chao b and L.J. Chen a a Department of Materials Science and Engineering, National b United Microelectronics Corporation, Hsinchu, Taiwan
Tsing Hua University, Hsinchu,
Taiwan
The annealing behavior of residual defects in high-dose BF,+-implanted (0Ol)Si under different implantation conditions has been studied by cross-sectional transmission electron microscopy and four-point probe sheet resistance measurements. Three kinds of samples were prepared with different implanters. M, MC and H samples were implanted with 80 keV, 4~1O’~/crn~ BF2+ in a medium-current implanter without deliberate end-station cooling, a medium-current implanter with a freon-cooled end station, and a effects were revealed by the high-current implanter with a water-cooled end station, respectively. The BF, + ion dissociation comparison of M or MC and H samples. Rod-like and equi-axial dislocation loops beneath the original a/c interface were observed in the M and MC samples. The dopant activation of the annealed samples was found to correlate well with microstructural changes.
1. Introduction BFC implantation has become an important doping technique in the fabrication of p+-n junctions in microelectronic devices. In order to reduce the cost and to increase the throughput of IC fabrication, the mediumcurrent implanter (with a beam current in the range of tens to hundreds of microamperes) has been replaced by the high-current implanter (with a beam current of a few milliamperes for high-dose implantation). Owing to the differences in configuration of different models of implanters, the implantation conditions are varied. Changes in the implantation conditions, such as endstation cooling, molecular ion dissociation and contamination in the vacuum chamber can all influence the results of ion implantation. The channeling of boron during BF; tmplantation and the presence of a secondary boron peak as seen from SIMS depth profiling have been attributed to the dissociation of BFZ+ ions after the mass analysis [l-4]. The dissociation of BFa+ ions during implantation results in the deep implantation of B+ ions and makes the junction depth uncontrollable. Comparing the dissociation efficiency of BFz, ions from a medium-current implanter and a high-current implanter showed that a high efficiency of BF,+ ion dissociation occurred in the medium-current implanter [5]. The effect of the dissociation of BFC ions on the residual defects is therefore of much importance. In this work we study the annealing behaviors of residual defects and dopant activation in samples implanted by
’ Present address: AT&T Avenue,
Murray
0168-583X/91/$03.50
Bell Laboratories, Hill, NJ 07974, USA.
600 Mountain
0 1991 - Elsevier Science Publishers
medium- and high-current implanters. The residual defects and dopant activation were studied by the crosssectional transmission electron microscopy and fourpoint probe sheet resistance measurements.
2. Experimental procedures Single-crystal, 3-5 &!cm, phosphorus-doped (001)Si wafers were used in the present study. Samples were implanted with 80 keV BF,+ ions at a fluence of 4 x 101’/cm2. Three kinds of samples were prepared using different implanters. Samples designated M were implanted by a medium-current implanter at room temperature with the beam current maintained at less than 20 PA to minimize heating effects. To determine the effect of substrate cooling during ion implantation, samples labeled MC were prepared by a Varian/ Extrion 200-20A2 medium-current implanter with a freon-cooled end station. Finally, in order to determine the effects of high beam current and dissociation of BF,+ ions during ion implantation, samples labeled H were prepared in a Varian 120/10 high-current implanter with a watercooled end station. The beam current was as high as 3 mA. In the Varian/Extrion 200-20A2 implanter, the beam was focused and the scanned area was 60 cm2. The scanning frequency of the ion beam was 70 Hz along the vertical direction and 1000 Hz along the horizontal direction. In the Varian 120/10 implanter, the beam was elliptic in shape with major and minor axes of about 4 and 2 cm in length, respectively. The scanning frequency and rotation speed of the sample holder were 4.5 cycles/mm and 1000 rpm, respectively.
B.V. (North-Holland)
III. THROUGHPUT
& YIELD
194
C.H. Chu et al. / Annealing behavior of defectsin BF,‘-implanted (0Ol)Si
The beam was scanned over a strip 3 to 35 cm from the center of the substrate holder. The wafers were oriented 7” off the incident beam direction to alleviate the channeling effect. Isothermal annealings were performed in a three-zone diffusion furnace at 550-1000° C for 0.5-l h in N, ambient. High-purity N, gas was first passed through a titanium getter tube maintained at 800 o C to reduce the 0, content for annealings in N2 ambient. The residual defects were investigated by cross-sectional transmission electron microscopy conducted in a JEOL ZOOCX STEM. The dopant activation in the annealed samples was determined from the sheet resistances which were measured by the four-point probe technique.
3. Results and discussion The average thicknesses of the surface amorphous layers of the as-implanted M, MC and H samples were measured to be 120, 138 and 122 nm, respectively. The roughness of the a/c (amo~hous/crystalline) interface was found to increase in the order of H, MC and M samples, as shown in fig. 1. A thicker amorphous layer was found in the MC sample than those in the other samples, which is likely to be due to the alleviation of the aggregation of damage clusters by substrate cooling. Solid state epitaxial growth (SPEG) was not completed in M and MC samples annealed at 500°C for 1 h. The a/c interfaces were rather rough. The average thickness of the amorphous layers was about 10 nm and 5 nm in the M and MC samples, respectively. The thickness variation of the amorphous layers was about 40 nm and 30 nm in the M and MC samples, respeetively. A high density of twins was found in the crystalline surface layers. Twins were found to have grown from a depth of about 40 nm and 60 nm above the original a/c interface in the M and MC samples, respectively. The twins were plates grown on all four (111) planes. The a/c interfaces were found to be delineated by (111) planes. Paired dislocations were evident in the M samples but not in the MC samples. In the H samples, SPEG was found to be completed. The regrowth layer was essentially defect free and the spreading of the defect clusters near the original a/c interface was about 30 nm. Examples are shown in fig. 2. SPEG was completed in M, MC and H samples annealed at 600” C. Thick surface twins were formed in the M samples. The width of the region with a high density of twins is about 70 nm. “Y-shaped dislocations, extending from the original a/c interface to the lower boundary of the twin region with a density of 9 x 10s/cm2, were observed. In the MC samples, only a low density of small twins was observed. The lengths of the microtwin plates were about 10 to 30 nm. In the H
Fig. 1. XTEM micrographs of the as-implanted samples: (a) M sample, (b) MC sample and (c) H sample.
samples, the regrowth layer was found to be defect free. Defect clusters were observed near the original a/c interface. In the M samples annealed at 700 o C, - 60-nm-long rod-like defects and 20-nm-diameter dislocation loops were observed in a layer extending from the original a/c interface to a depth of - 320 nm from the surface. Twins near the surface covered about 28% of the surface area. Paired dislocations were found in the regrowth layers. In MC samples, - lo-nm-long rod-like defects and small dislocation loops were observed to be distributed in a lOO-nm-thick layer extending from the original a/c interface further into the substrate. In the H samples, no dislocation loops were observed beneath the original a/c interface. The defect clusters in the original a/c interface had grown into small dislocation loops in the M, MC and H samples. The depth distribution and general features of defects in 800°C annealed samples
C. H. Chu et al. / Annealing behavior of defects in BF,+ -implanted (001)Si
195
The most striking difference in the residual defects among the anneaIed samples is that twins did not form in the H samples, whereas they were annealed out at a lower temperature in the MC samples than in the M samples. Formation of twins in high-dose BF2+ implanted (001)Si has been found previously [7]. Although the implantation was nominally performed at room temperature, the temperature can be much higher with poor thermal conduction in the end station. The self-annealing effect is expected to promote the aggregation of the defect clusters induced by ion implantation. The aggregates are rather difficult to remove by thermal annealing IS]. It is thought that the stabilized defect clusters tend to attract the fluorine atoms and hinder the SPEG of the amorphous layer. As the SPEG is slowed down, twins are formed. Comparison among M, MC and H samples suggested that the formation of twins in the regrowth layer in BF,+-implanted (001)Si is
Fig. 2. Bright-field (BF) XTEM micrographs of the 550 *C, 1 h annealed samples: (a) M sample, (b) MC sample and (c) H sample.
were found to be similar to those observed in 700” C annealed samples. In the M samples annealed at 9OO”C, the rod-like defects beneath the original a/c interface were found to grow into loops. “V-shaped dislocations were found in the near surface regions. A low density of surface twins was observed. In the MC samples, the dislocation loops near the original a/c interface were larger than those in the 800°C annealed samples. For the H samples, similar results were obtained as those in the 800 OC annealed samples. Examples are shown in fig. 3. In the M samples annealed at 1000 ’ C, surface twins and dislocations near the original a/c interface were observed. Discrete and large dislocation loops were observed near the original a/c interface in the MC samples. In the H samples, a lower density of dislocation loops than that found in the MC samples was observed near the original a/c interface.
Fig. 3. WBDF micrographs of the 900°C, l/2 h annealed samples: (a) M sample, (b) MC sample and (c) N sample. III. THROUGHPUT
& YIELD
196
C.H. Chu et al. / Annealing behavior of defects in BF,+ -implanted (0Ol)Si
Fig. 4. Sheet resistances of the 550 to I100 o C annealed M, MC and H samples.
correlated with substrate heating conditions during the implantation. Rod-like dislocations and equi-axial loops in BFCimplanted samples have been characterized previously [lO,ll]. In the M samples, the results were similar to those obtained previously. In the MC samples, the temperature range of formation and the size of these dislocations beneath the original a/c interface are narrower and smaller than those of the M samples, respectively. In the H samples, no dislocations beneath the original a/c interface were observed. Using the highcurrent implanter, BF; dissociation is less prone to occur. The formation of dislocations beneath the original a/c interface in the M and MC samples suggested that the dissociation of BF; ions occurred dqing implantation. The dissociation of BF2+ ions during implantation resulted in the implantation of B+ and F’ with higher energy into the substrate. Channeling effects may further aggravate tailing of the implant profile [4,5]. The electrical activation of implanted boron ions in the M, MC and H samples was measured by the fourpoint probe method. The variations of sheet resistance of these samples, as shown in fig. 4, are correlated well with microstructural changes. The sheet resistances of the H samples are higher than those of the corresponding M and MC samples. This difference may be attributed to the difference in dissociation of BFC ions in the accelerating tubes. In the medium-current implanter, dissociation of BF,+ ions occurred during the acceleration stage. The range of the implanted boron
profiles in the M and MC samples is longer than that of the high-current implanter implanted samples.
4. Summary and couclusious The effects of substrate cooling for BF;-implanted (001)Si were revealed by comparing the residual defects in annealed M and MC samples. A high density of surface twins was observed in the M samples. The BFa+ ion dissociation effects were demonstrated by comparing M or MC and H samples. Rod-like and equi-axial dislocation loops beneath the a/c interface were observed in the M and MC samples but not in H samples. A monotonic decrease in sheet resistance with annealing temperature was observed for M samples. The variation in sheet resistance with annealing temperature for M, MC and H samples was found to correlate well with the changes in microstructures.
This research was supported by the Republic China National Science Council.
of
References [l] T.W. Sigmon, V.R. Deline, CA. Evans Jr. and W.M. Katz, J. Electrochem. Sot. 127 (1980) 981.
C. H. Chu et al. / Annealing behavior of defects in BF,’ -implanted (0Ol)Si [2] R.G. Wilson, J. Appl. Phys. 54 (1983) 6879. [3] S.S. Cohen, J.F. Norton, E.F. Kock and G.J. Weisel, J. Appl. Phys. 57 (1985) 1200. [4] I.W. Wu, R.T. Fulks and J.C. Mikkelsen Jr., J. Appl. Phys. 60 (1986) 2422. [5] G. Queirolo, C. Bresolin, L. Meda, M. Anderle and R. Canteri, J. Electrochem. Sot. 135 (1988) 777. [6] I. Sum, U. Shreter, M-A. Nicolet and J.E. Baker, J. Appl. Phys. 56 (1984) 273.
[7] C.W. Nieh and L.J. Chen, J. Appl. Phys. [S] G. Queirolo, P. Caprara, L. Meda, C. Anderle, G. Otaaviani and A. Armigliato, Sot. 134 (1987) 2950. [9] T. Sands, J. Washburn, R. Gronsky, W. Sandana and G.A. Rozgonyi, Appl. Phys. 982. [lo] L.J. Chen and I.W. Wu, J. Appl. Phys. 52 [ll] I.W. Wu and L.J. Chen, J. Appl. Phys. 58
197 60 (1986) 3114. Guareschi, M. J. Electrochem.
III. THROUGHPUT
Maszara, D.K. Lett. 45 (1984) (1981) 3318. (1985) 3032.
& YIELD
and Methods
in Physics
Research
193
B55 (1991) 193-197
Annealing behaviors of residual defects in high-dose BF,f -implanted (001) Si under different implantation conditions C.H. Chu a,l, E.L. Tsai a, W.Y. Chao b and L.J. Chen a a Department of Materials Science and Engineering, National b United Microelectronics Corporation, Hsinchu, Taiwan
Tsing Hua University, Hsinchu,
Taiwan
The annealing behavior of residual defects in high-dose BF,+-implanted (0Ol)Si under different implantation conditions has been studied by cross-sectional transmission electron microscopy and four-point probe sheet resistance measurements. Three kinds of samples were prepared with different implanters. M, MC and H samples were implanted with 80 keV, 4~1O’~/crn~ BF2+ in a medium-current implanter without deliberate end-station cooling, a medium-current implanter with a freon-cooled end station, and a effects were revealed by the high-current implanter with a water-cooled end station, respectively. The BF, + ion dissociation comparison of M or MC and H samples. Rod-like and equi-axial dislocation loops beneath the original a/c interface were observed in the M and MC samples. The dopant activation of the annealed samples was found to correlate well with microstructural changes.
1. Introduction BFC implantation has become an important doping technique in the fabrication of p+-n junctions in microelectronic devices. In order to reduce the cost and to increase the throughput of IC fabrication, the mediumcurrent implanter (with a beam current in the range of tens to hundreds of microamperes) has been replaced by the high-current implanter (with a beam current of a few milliamperes for high-dose implantation). Owing to the differences in configuration of different models of implanters, the implantation conditions are varied. Changes in the implantation conditions, such as endstation cooling, molecular ion dissociation and contamination in the vacuum chamber can all influence the results of ion implantation. The channeling of boron during BF; tmplantation and the presence of a secondary boron peak as seen from SIMS depth profiling have been attributed to the dissociation of BFZ+ ions after the mass analysis [l-4]. The dissociation of BFa+ ions during implantation results in the deep implantation of B+ ions and makes the junction depth uncontrollable. Comparing the dissociation efficiency of BFz, ions from a medium-current implanter and a high-current implanter showed that a high efficiency of BF,+ ion dissociation occurred in the medium-current implanter [5]. The effect of the dissociation of BFC ions on the residual defects is therefore of much importance. In this work we study the annealing behaviors of residual defects and dopant activation in samples implanted by
’ Present address: AT&T Avenue,
Murray
0168-583X/91/$03.50
Bell Laboratories, Hill, NJ 07974, USA.
600 Mountain
0 1991 - Elsevier Science Publishers
medium- and high-current implanters. The residual defects and dopant activation were studied by the crosssectional transmission electron microscopy and fourpoint probe sheet resistance measurements.
2. Experimental procedures Single-crystal, 3-5 &!cm, phosphorus-doped (001)Si wafers were used in the present study. Samples were implanted with 80 keV BF,+ ions at a fluence of 4 x 101’/cm2. Three kinds of samples were prepared using different implanters. Samples designated M were implanted by a medium-current implanter at room temperature with the beam current maintained at less than 20 PA to minimize heating effects. To determine the effect of substrate cooling during ion implantation, samples labeled MC were prepared by a Varian/ Extrion 200-20A2 medium-current implanter with a freon-cooled end station. Finally, in order to determine the effects of high beam current and dissociation of BF,+ ions during ion implantation, samples labeled H were prepared in a Varian 120/10 high-current implanter with a watercooled end station. The beam current was as high as 3 mA. In the Varian/Extrion 200-20A2 implanter, the beam was focused and the scanned area was 60 cm2. The scanning frequency of the ion beam was 70 Hz along the vertical direction and 1000 Hz along the horizontal direction. In the Varian 120/10 implanter, the beam was elliptic in shape with major and minor axes of about 4 and 2 cm in length, respectively. The scanning frequency and rotation speed of the sample holder were 4.5 cycles/mm and 1000 rpm, respectively.
B.V. (North-Holland)
III. THROUGHPUT
& YIELD
194
C.H. Chu et al. / Annealing behavior of defectsin BF,‘-implanted (0Ol)Si
The beam was scanned over a strip 3 to 35 cm from the center of the substrate holder. The wafers were oriented 7” off the incident beam direction to alleviate the channeling effect. Isothermal annealings were performed in a three-zone diffusion furnace at 550-1000° C for 0.5-l h in N, ambient. High-purity N, gas was first passed through a titanium getter tube maintained at 800 o C to reduce the 0, content for annealings in N2 ambient. The residual defects were investigated by cross-sectional transmission electron microscopy conducted in a JEOL ZOOCX STEM. The dopant activation in the annealed samples was determined from the sheet resistances which were measured by the four-point probe technique.
3. Results and discussion The average thicknesses of the surface amorphous layers of the as-implanted M, MC and H samples were measured to be 120, 138 and 122 nm, respectively. The roughness of the a/c (amo~hous/crystalline) interface was found to increase in the order of H, MC and M samples, as shown in fig. 1. A thicker amorphous layer was found in the MC sample than those in the other samples, which is likely to be due to the alleviation of the aggregation of damage clusters by substrate cooling. Solid state epitaxial growth (SPEG) was not completed in M and MC samples annealed at 500°C for 1 h. The a/c interfaces were rather rough. The average thickness of the amorphous layers was about 10 nm and 5 nm in the M and MC samples, respectively. The thickness variation of the amorphous layers was about 40 nm and 30 nm in the M and MC samples, respeetively. A high density of twins was found in the crystalline surface layers. Twins were found to have grown from a depth of about 40 nm and 60 nm above the original a/c interface in the M and MC samples, respectively. The twins were plates grown on all four (111) planes. The a/c interfaces were found to be delineated by (111) planes. Paired dislocations were evident in the M samples but not in the MC samples. In the H samples, SPEG was found to be completed. The regrowth layer was essentially defect free and the spreading of the defect clusters near the original a/c interface was about 30 nm. Examples are shown in fig. 2. SPEG was completed in M, MC and H samples annealed at 600” C. Thick surface twins were formed in the M samples. The width of the region with a high density of twins is about 70 nm. “Y-shaped dislocations, extending from the original a/c interface to the lower boundary of the twin region with a density of 9 x 10s/cm2, were observed. In the MC samples, only a low density of small twins was observed. The lengths of the microtwin plates were about 10 to 30 nm. In the H
Fig. 1. XTEM micrographs of the as-implanted samples: (a) M sample, (b) MC sample and (c) H sample.
samples, the regrowth layer was found to be defect free. Defect clusters were observed near the original a/c interface. In the M samples annealed at 700 o C, - 60-nm-long rod-like defects and 20-nm-diameter dislocation loops were observed in a layer extending from the original a/c interface to a depth of - 320 nm from the surface. Twins near the surface covered about 28% of the surface area. Paired dislocations were found in the regrowth layers. In MC samples, - lo-nm-long rod-like defects and small dislocation loops were observed to be distributed in a lOO-nm-thick layer extending from the original a/c interface further into the substrate. In the H samples, no dislocation loops were observed beneath the original a/c interface. The defect clusters in the original a/c interface had grown into small dislocation loops in the M, MC and H samples. The depth distribution and general features of defects in 800°C annealed samples
C. H. Chu et al. / Annealing behavior of defects in BF,+ -implanted (001)Si
195
The most striking difference in the residual defects among the anneaIed samples is that twins did not form in the H samples, whereas they were annealed out at a lower temperature in the MC samples than in the M samples. Formation of twins in high-dose BF2+ implanted (001)Si has been found previously [7]. Although the implantation was nominally performed at room temperature, the temperature can be much higher with poor thermal conduction in the end station. The self-annealing effect is expected to promote the aggregation of the defect clusters induced by ion implantation. The aggregates are rather difficult to remove by thermal annealing IS]. It is thought that the stabilized defect clusters tend to attract the fluorine atoms and hinder the SPEG of the amorphous layer. As the SPEG is slowed down, twins are formed. Comparison among M, MC and H samples suggested that the formation of twins in the regrowth layer in BF,+-implanted (001)Si is
Fig. 2. Bright-field (BF) XTEM micrographs of the 550 *C, 1 h annealed samples: (a) M sample, (b) MC sample and (c) H sample.
were found to be similar to those observed in 700” C annealed samples. In the M samples annealed at 9OO”C, the rod-like defects beneath the original a/c interface were found to grow into loops. “V-shaped dislocations were found in the near surface regions. A low density of surface twins was observed. In the MC samples, the dislocation loops near the original a/c interface were larger than those in the 800°C annealed samples. For the H samples, similar results were obtained as those in the 800 OC annealed samples. Examples are shown in fig. 3. In the M samples annealed at 1000 ’ C, surface twins and dislocations near the original a/c interface were observed. Discrete and large dislocation loops were observed near the original a/c interface in the MC samples. In the H samples, a lower density of dislocation loops than that found in the MC samples was observed near the original a/c interface.
Fig. 3. WBDF micrographs of the 900°C, l/2 h annealed samples: (a) M sample, (b) MC sample and (c) N sample. III. THROUGHPUT
& YIELD
196
C.H. Chu et al. / Annealing behavior of defects in BF,+ -implanted (0Ol)Si
Fig. 4. Sheet resistances of the 550 to I100 o C annealed M, MC and H samples.
correlated with substrate heating conditions during the implantation. Rod-like dislocations and equi-axial loops in BFCimplanted samples have been characterized previously [lO,ll]. In the M samples, the results were similar to those obtained previously. In the MC samples, the temperature range of formation and the size of these dislocations beneath the original a/c interface are narrower and smaller than those of the M samples, respectively. In the H samples, no dislocations beneath the original a/c interface were observed. Using the highcurrent implanter, BF; dissociation is less prone to occur. The formation of dislocations beneath the original a/c interface in the M and MC samples suggested that the dissociation of BF; ions occurred dqing implantation. The dissociation of BF2+ ions during implantation resulted in the implantation of B+ and F’ with higher energy into the substrate. Channeling effects may further aggravate tailing of the implant profile [4,5]. The electrical activation of implanted boron ions in the M, MC and H samples was measured by the fourpoint probe method. The variations of sheet resistance of these samples, as shown in fig. 4, are correlated well with microstructural changes. The sheet resistances of the H samples are higher than those of the corresponding M and MC samples. This difference may be attributed to the difference in dissociation of BFC ions in the accelerating tubes. In the medium-current implanter, dissociation of BF,+ ions occurred during the acceleration stage. The range of the implanted boron
profiles in the M and MC samples is longer than that of the high-current implanter implanted samples.
4. Summary and couclusious The effects of substrate cooling for BF;-implanted (001)Si were revealed by comparing the residual defects in annealed M and MC samples. A high density of surface twins was observed in the M samples. The BFa+ ion dissociation effects were demonstrated by comparing M or MC and H samples. Rod-like and equi-axial dislocation loops beneath the a/c interface were observed in the M and MC samples but not in H samples. A monotonic decrease in sheet resistance with annealing temperature was observed for M samples. The variation in sheet resistance with annealing temperature for M, MC and H samples was found to correlate well with the changes in microstructures.
This research was supported by the Republic China National Science Council.
of
References [l] T.W. Sigmon, V.R. Deline, CA. Evans Jr. and W.M. Katz, J. Electrochem. Sot. 127 (1980) 981.
C. H. Chu et al. / Annealing behavior of defects in BF,’ -implanted (0Ol)Si [2] R.G. Wilson, J. Appl. Phys. 54 (1983) 6879. [3] S.S. Cohen, J.F. Norton, E.F. Kock and G.J. Weisel, J. Appl. Phys. 57 (1985) 1200. [4] I.W. Wu, R.T. Fulks and J.C. Mikkelsen Jr., J. Appl. Phys. 60 (1986) 2422. [5] G. Queirolo, C. Bresolin, L. Meda, M. Anderle and R. Canteri, J. Electrochem. Sot. 135 (1988) 777. [6] I. Sum, U. Shreter, M-A. Nicolet and J.E. Baker, J. Appl. Phys. 56 (1984) 273.
[7] C.W. Nieh and L.J. Chen, J. Appl. Phys. [S] G. Queirolo, P. Caprara, L. Meda, C. Anderle, G. Otaaviani and A. Armigliato, Sot. 134 (1987) 2950. [9] T. Sands, J. Washburn, R. Gronsky, W. Sandana and G.A. Rozgonyi, Appl. Phys. 982. [lo] L.J. Chen and I.W. Wu, J. Appl. Phys. 52 [ll] I.W. Wu and L.J. Chen, J. Appl. Phys. 58
197 60 (1986) 3114. Guareschi, M. J. Electrochem.
III. THROUGHPUT
Maszara, D.K. Lett. 45 (1984) (1981) 3318. (1985) 3032.
& YIELD