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Self-Aligned Heterojunction MISFET

IP.com Disclosure Number: IPCOM000046547D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Fowler, AB: AUTHOR [+2]

Abstract

A heterojunction Metal-Insulator-Semiconductor Field-Effect Transistor (MISFET) device, such as GaAlAs on GaAs, as illustrated in Fig. 1, can have an effective connection between the source and drain provided by implanted ions. In Fig. 1, if the device is an enhancement-mode device, there will be no charge arising from, for instance, a doped GaAlAs region, as in a modulation-doped structure that can provide a channel between the carriers induced in the GaAs surface under the gate and the source and drain. The problem can be overcome by ion implantation. The first solution is to implant n-dopants after the formation of the structure in Fig. 1. This implantation is shallow so that the ions are far from the interface and the desired high mobility is retained. The structure is shown in Fig.

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Self-Aligned Heterojunction MISFET

A heterojunction Metal-Insulator-Semiconductor Field-Effect Transistor (MISFET) device, such as GaAlAs on GaAs, as illustrated in Fig. 1, can have an effective connection between the source and drain provided by implanted ions. In Fig. 1, if the device is an enhancement-mode device, there will be no charge arising from, for instance, a doped GaAlAs region, as in a modulation-doped structure that can provide a channel between the carriers induced in the GaAs surface under the gate and the source and drain. The problem can be overcome by ion implantation. The first solution is to implant n-dopants after the formation of the structure in Fig. 1. This implantation is shallow so that the ions are far from the interface and the desired high mobility is retained. The structure is shown in Fig. 2 wherein the gate and source and drain self-align the implantation. The transferred electrons provide the connections to the gate region. Naturally, this implantation would have to be annealed and either a suitable short anneal or a laser anneal would be needed and a cap to prevent crystal dissociation would be required. An alternative solution requires a deeper implant centered at the interface, as shown in Fig. 3. This implant would require annealing also. However, here laser annealing would have distinct advantages because a wavelength can be selected to favor a particular material such that hn < Eg GaAlAs but hn > Eg GaAs . Then the laser po...