Memory first process flow and device
A semiconductor device and method of making the same are disclosed. The semiconductor device includes a memory gate on a charge storage structure formed on a substrate, a select gate on a gate dielectric on the substrate proximal to the memory gate, and a dielectric structure between the memory gate and the select gate, and adjacent to sidewalls of the memory gate and the select gate, wherein the memory gate and the select gate are separated by a thickness of the dielectric structure. Generally, the dielectric structure comprises multiple dielectric layers including a first dielectric layer adjacent the sidewall of the memory gate, and a nitride dielectric layer adjacent to the first dielectric layer and between the memory gate and the select gate. Other embodiments are also disclosed.
1. A method of fabricating a semiconductor device, comprising:
forming a multi-layered charge storage structure over a channel in a substrate including;
forming a nitride layer including silicon rich nitride over the channel and a shallow trench isolation (STI), wherein the STI is disposed to separate the semiconductor device from an adjacent semiconductor device;
forming a sacrificial layer over the nitride layer,
removing completely the sacrificial layer and the nitride layer disposed over the STI; and
removing the sacrificial layer over the channel;
forming a memory gate on the charge storage structure;
forming a dielectric structure adjacent to a sidewall of the memory gate, the dielectric structure comprising a plurality of dielectric layers substantially parallel to the sidewall of the memory gate; and
forming a select gate on a gate dielectric on the substrate adjacent to the dielectric structure, proximal to the memory gate and separated therefrom by a total thickness of the dielectric structure.
2. The method of claim 1 , wherein forming the dielectric structure comprises forming at least one L-shaped dielectric layer including a first portion substantially parallel to the sidewall of the memory gate and a second portion on the surface of the substrate, and wherein the gate dielectric comprises the second portion of the L-shaped dielectric layer.
3. The method of claim 1 , wherein the sacrificial layer includes at least one of an oxide layer, a photoresist layer, and a bottom anti-reflectant coating (BARC) layer.
4. The method of claim 1 , wherein the STI includes a top surface having a higher elevation than the channel.
5. The method of claim 2 , wherein forming the dielectric structure further comprises forming a second dielectric layer substantially parallel to the first portion of the L-shaped dielectric layer, and a third dielectric layer between the L-shaped dielectric layer and the second dielectric layer.
6. The method of claim 1 , further comprising an initial step of forming the channel in the surface of the substrate, and wherein forming the memory gate comprises forming the memory gate overlying a first portion of the channel, and wherein forming the select gate comprises forming the select gate overlying a second portion of the channel.
7. The method of claim 1 , wherein forming the select gate comprises forming a select gate having a top surface proximal to the memory gate that is higher than a top surface of the memory gate, and further comprising forming a spacer adjacent to a sidewall of the select gate, and between the sidewall of the select gate and the top surface of the memory gate.
8. The method of claim 1 , further comprising forming a first self-aligned silicide (SALICIDE) on a top surface of the memory gate and a second SALICIDE on a top surface of the select gate.