The Impact of IGZO Channel Composition on DRAM Transistor Performance

The main limitations of the current dynamic random access memory (DRAM) technology are its scalability and power consumption. These constraints can be overcome by using an In–Ga–Zn–oxide (IGZO) transistor that offers a low OFF-current and high scalability. For that, the IGZO device performance needs to be optimized, which includes increasing its
${I}_{ \mathrm{\scriptscriptstyle ON}}$
and
${V}_{\text {TH}}$
. By combining experiments on scaled industry-relevant devices with ab initio calculations, we show that IGZO composition impacts
${I}_{ \mathrm{\scriptscriptstyle ON}}$
and
${V}_{\text {TH}}$
through modifying channel mobility and carrier concentration. In the studied composition range,
${I}_{ \mathrm{\scriptscriptstyle ON}}$
increases with higher In % and lower Ga %, which is opposite to the
${V}_{\text {TH}}$
trend. Scanning the whole IGZO composition space with ab initio calculations, we predict that films with In < 10% and 20% < Ga < 80% might be beneficial for improving
${I}_{ \mathrm{\scriptscriptstyle ON}}$
and
${V}_{\text {TH}}$
.