Memory effects in MOS capacitors with silicon quantum dots

To form crystalline Si dots embedded in SiO2 We have deposited thin films o f silicon-rich oxide (SRO) by plasma-enhanced chemical vapor deposition of SiH4 and O-2 Then the materials have been annealed in N-2 ambient at temper atures between 950 degreesC and 1100 degreesC. Under such processing, the s upersaturation of Si in the amorphous SRO film produces the formation of cr ystalline Si dots embedded in SiO2 The narrow dot size distributions, analy zed by transmission electron microscopy, are characterized by average grain radii and standard deviations down to about 1 nm. The memory function of s uch structures has been investigated in MOS capacitors with a SRO film sand wiched between two thin SiO2 layers as insulator and with an n(+) polycryst alline silicon gate. The operations of write and storage are clearly detect ed by measurements of hysteresis in capacitance- voltage characteristics. A model which explains both the occurrence of steady-state conduction throug h the SiO2/SRO/SiO2, stack at a relatively low voltage and the shift of fla t-band voltage is presented and discussed. (C) 2001 Elsevier Science B.V. A ll rights reserved.