Manufacturing process for non-volatile floating gate memory cells and control circuitry

摘要

A process for manufacturing floating gate non-volatile memory cells (10), integrated in a semiconductor substrate (1) and incorporated to a cell matrix (30) with associated control circuitry (40) comprising both N-channel and P-channel MOS transistors (20), which process comprises the following steps:forming a plurality of active areas in the matrix and the circuitry regions;- forming N wells to provide N-channel transistors, and P wells to provide P-channel transistors;depositing a first thin oxide layer (3) and a first POLY 1 polysilicon layer (4) onto all the active areas to produce floating gate regions of the memory cells;carrying out a step of doping the first polysilicon layer (4);depositing a second dielectric layer (5) onto all the active areas; and is characterized in that it comprises the following steps:depositing a second polysilicon layer onto all the active areas;carrying out a step of doping the second polysilicon layer (6) in order to reduce its resistance;removing the stack structure, comprising the second POLY CAP polysilicon layer (6), second ONO dielectric layer (5), first POLY 1 polysilicon layer (4), and first thin oxide layer (3), from the circuitry (40) by a photolithographic technique using a so-called "matrix" mask;depositing at least one additional thin oxide layer (7) and a third undoped POLY 2 polysilicon layer (8) onto the whole semiconductor;defining the third polysilicon layer (8) to produce the gate regions of the circuitry transistors by a photolithographic technique using a so-called "transistor gate" mask (11), and simultaneously removing the third polysilicon layer (8) from the matrix (30);carrying out a self-aligned etching step above the matrix active areas of the stack structure (6,5,4) and the first thin oxide layer in order to define the gate regions of the memory cell (10) by means of a so-called "cell gate" mask (12) covering and protecting the circuitry (40);implanting dopant in the junction areas to produce the source/drain regions of the memory cells (30).