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Wide planar MOSFET with uniaxial strain

IP.com Disclosure Number: IPCOM000235797D
Publication Date: 2014-Mar-25
Document File: 3 page(s) / 37K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to form a wide planar Metal-Oxide Semiconductor Field Effect Transistor (MOSFET) with uniaxial strain. The approach forms narrow Si:C stripes in the active region. The space between these stripes is filled with relaxed Si. Since there is very small difference in the conduction band of Si:C and Si, both channel materials contribute to the drive current.

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Wide planar MOSFET with uniaxial strain

Embedded stressors and stress liners are less effective in future technology nodes with small device pitch. Channel strain engineering using epitaxially grown semiconductors in the channel with an equilibrium lattice constant different from that of the substrate is a viable method for extending the transistor performance. To get the most benefit from channel strain it is essential that the channel is made narrow so that the initial biaxial strain is transformed to uniaxial strain. This mandates the use of multi-finger Metal-Oxide Semiconductor Field Effect Transistors (MOSFETs) which come with area penalty. So, there is a need to widen transistors with uniaxial strain.

The solution is to form narrow Si:C stripes in the active region. The space between these stripes is filled with relaxed Si. Since there is very small difference in the conduction band of Si:C and Si, both channel materials contribute to the drive current. Assuming that narrow Si:C gives a 20-30% increase in the drive current, the average increase in the drive current is 10-15%.

Figures 1-6 illustrate the process.

Figure 1: Starting with a substrate that can be relaxed Si or relaxed SiGe on Si, isolation regions are formed

Figure 2: Optionally Si is recessed and Si:C is epitaxially grown

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Figure 3: A hardmask is placed on the Si:C and patterned to narrow stripes. Si:C is patterned to narrow stripes

The initial biaxial strain is transformed into...