EPE Association: 03 - Madep - M03 - MATERIAL AND PROCESSES 03

03 - Madep - M03 - MATERIAL AND PROCESSES 03
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - EPE-MADEP Joint Sessions > 03 - Madep - M03 - MATERIAL AND PROCESSES 03

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   APPLICATIONS OF ION IMPLANTATION TO THE CONTROL OF DYNAMIC CHARACTERISTICS IN POWER DEVICES
By F. Frisina; N. Tavolo; G. Ferla; S. U. Campisano; S. Coffa [View]
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Abstract: Ion implantation and diffusion of platinum and gold has been used to reduce to optimum values the minority carrier lifetime in power MOS and in insulated gate bipolar transistors (IGBT) without appreciable worsening of their static characteristics. Ion implantation of metallic impurities offers the unique advantage of a precise control of the total amount of trap centers and the possibility to get impurity profiles that cannot be obtained by conventional deposition and diffusion methods. In order to fully characterize the process we have investigated the diffusion mechanism and the compensating effects of implanted metals. We have applied the method to the fabrication of high voltage power MOS devices in order to increase the switching speed of the internal diodes thus optimizing the unavoidable increase of the on- resistance. As an example, for platinum implantation at a dose of 10to13 / cm² we get a 10% increase in Ron and a 90% reduction of the reverse recovery charge. These values, that can be varied by changing the Pt fluence, are compared with those obtained by gold implantation or deposition. Platinum implantation has been also adopted in the fabrication of IGBT; it has been measured an increase of the latch-up current density (to values larger than 600 A / cm² at 100°c) and a fall time of less than 200ns. The trade off between static and dynamic characteristics (V-cesat vs t-fall) is compared with figures obtained by other methods of lifetime reduction.

   A position-sensitive method for determination of high-level carrier lifetimes in power devices
By M. Rosling; H. Bleichner; E. Nordlander [View]
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Abstract: A position-sensitive method for ambipolar lifetime measurements is developed. The measurement technique is applicable to lowly doped devices in high-level injection. The decay of excess carriers (OCCD) is utilized for the evaluation of the lifetime values. The ambipolar diffusion length may also be independently estimared. Furthermore, the diffusion constant is extracted when plotting the the information in a special manner. The investigation was performed on p-i-n diodes subject to different lifetime affection, e. g. proton and/or electron irradiations. The results from OCCD measurements are compared with results from electrical OCVD measurements.

   USING CARRIER LIFETIME DEPENDENCES ON TEMPERATURE AND CURRENT DENSITY IN DIAGNOSTICS OF SILICON STRUCTURES
By V. Benda [View]
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Abstract: This paper presents a simple method for determining the deep energy level, which influences predominantly the carrier lifetime in the working temperature range of a semiconductor device, using the dependence of carrier lifetime on the current density and temperature. The type of carrier lifetime dependence on current density (excess carrier concentration) is connected with the position of a dominant deep level with respect to the Fermi energy level in the gap. When measuring dependences of the carrier lifetime on the current density at different temperatures, the dominant deep level position may be found from the change of the Fermi level position with temperature with respect to that deep level. The experimental verification was performed on power silicon diodes using the DCVD method in a larger interval of current densities and temperatures.

   OXYGEN BEHAVIOUR IN CZOCHRALSKI SILICON SUBSTRATES AND IN EPITAXIAL LAYERS
By A. Stella; A. Borghesi; M. Geddo; B. Pivac; A. Sassella [View]
[Download]

Abstract: The quality of epitaxial silicon layers grown on Czochralski single crystal substrates directly influences device parameters and yield. Unintentional doping of these layers from the substrate has been well studied. However we found no reports on unintentional oxygen contamination of epilayers due to its presence in the substrate. The use of high spatial resolution Fourier transform infrared spectroscopy in transversal mode is shown to be a powerful technique for both oxygen profiling and precipitation studies. A significant difference in oxygen behaviour during the epitaxial layer growth, even for lightly P doped substrates, is found. Oxygen, that in some cases diffuses significantly into the grown epitaxial layer, tends to form precipitates there. This is an important consequence of outdiffusion, since it directly influences the quality of the epitaxial layer.

03 - Madep - M03 - MATERIAL AND PROCESSES 03
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - EPE-MADEP Joint Sessions > 03 - Madep - M03 - MATERIAL AND PROCESSES 03
	[return to parent folder]

	APPLICATIONS OF ION IMPLANTATION TO THE CONTROL OF DYNAMIC CHARACTERISTICS IN POWER DEVICES By F. Frisina; N. Tavolo; G. Ferla; S. U. Campisano; S. Coffa	[View] [Download]
Abstract: Ion implantation and diffusion of platinum and gold has been used to reduce to optimum values the minority carrier lifetime in power MOS and in insulated gate bipolar transistors (IGBT) without appreciable worsening of their static characteristics. Ion implantation of metallic impurities offers the unique advantage of a precise control of the total amount of trap centers and the possibility to get impurity profiles that cannot be obtained by conventional deposition and diffusion methods. In order to fully characterize the process we have investigated the diffusion mechanism and the compensating effects of implanted metals. We have applied the method to the fabrication of high voltage power MOS devices in order to increase the switching speed of the internal diodes thus optimizing the unavoidable increase of the on- resistance. As an example, for platinum implantation at a dose of 10to13 / cm² we get a 10% increase in Ron and a 90% reduction of the reverse recovery charge. These values, that can be varied by changing the Pt fluence, are compared with those obtained by gold implantation or deposition. Platinum implantation has been also adopted in the fabrication of IGBT; it has been measured an increase of the latch-up current density (to values larger than 600 A / cm² at 100°c) and a fall time of less than 200ns. The trade off between static and dynamic characteristics (V-cesat vs t-fall) is compared with figures obtained by other methods of lifetime reduction.

	A position-sensitive method for determination of high-level carrier lifetimes in power devices By M. Rosling; H. Bleichner; E. Nordlander	[View] [Download]
Abstract: A position-sensitive method for ambipolar lifetime measurements is developed. The measurement technique is applicable to lowly doped devices in high-level injection. The decay of excess carriers (OCCD) is utilized for the evaluation of the lifetime values. The ambipolar diffusion length may also be independently estimared. Furthermore, the diffusion constant is extracted when plotting the the information in a special manner. The investigation was performed on p-i-n diodes subject to different lifetime affection, e. g. proton and/or electron irradiations. The results from OCCD measurements are compared with results from electrical OCVD measurements.

	USING CARRIER LIFETIME DEPENDENCES ON TEMPERATURE AND CURRENT DENSITY IN DIAGNOSTICS OF SILICON STRUCTURES By V. Benda	[View] [Download]
Abstract: This paper presents a simple method for determining the deep energy level, which influences predominantly the carrier lifetime in the working temperature range of a semiconductor device, using the dependence of carrier lifetime on the current density and temperature. The type of carrier lifetime dependence on current density (excess carrier concentration) is connected with the position of a dominant deep level with respect to the Fermi energy level in the gap. When measuring dependences of the carrier lifetime on the current density at different temperatures, the dominant deep level position may be found from the change of the Fermi level position with temperature with respect to that deep level. The experimental verification was performed on power silicon diodes using the DCVD method in a larger interval of current densities and temperatures.

	OXYGEN BEHAVIOUR IN CZOCHRALSKI SILICON SUBSTRATES AND IN EPITAXIAL LAYERS By A. Stella; A. Borghesi; M. Geddo; B. Pivac; A. Sassella	[View] [Download]
Abstract: The quality of epitaxial silicon layers grown on Czochralski single crystal substrates directly influences device parameters and yield. Unintentional doping of these layers from the substrate has been well studied. However we found no reports on unintentional oxygen contamination of epilayers due to its presence in the substrate. The use of high spatial resolution Fourier transform infrared spectroscopy in transversal mode is shown to be a powerful technique for both oxygen profiling and precipitation studies. A significant difference in oxygen behaviour during the epitaxial layer growth, even for lightly P doped substrates, is found. Oxygen, that in some cases diffuses significantly into the grown epitaxial layer, tends to form precipitates there. This is an important consequence of outdiffusion, since it directly influences the quality of the epitaxial layer.