Split gate non-volatile flash memory cell having metal-enhanced gates and method of making same
View Patent ↗A non-volatile memory cell including a substrate having first and second regions with a channel region therebetween. A floating gate is disposed over and insulated from a first portion of the channel region which is adjacent the first region. A select gate is disposed over and insulated from a second portion of the channel region which is adjacent to the second region. The select gate includes a block of polysilicon material and a work function metal material layer extending along bottom and side surfaces of the polysilicon material block. The select gate is insulated from the second portion of the channel region by a silicon dioxide layer and a high K insulating material layer. A control gate is disposed over and insulated from the floating gate, and an erase gate is disposed over and insulated from the first region, and disposed laterally adjacent to and insulated from the floating gate.
1. A non-volatile memory cell comprising:
a substrate of a first conductivity type, having a first region of a second conductivity type, a second region of the second conductivity type spaced apart from the first region, forming a channel region therebetween;
a floating gate disposed over and insulated from a first portion of the channel region which is adjacent the first region;
a select gate disposed over and insulated from a second portion of the channel region which is adjacent to the second region, the select gate comprising:
a block of polysilicon material, and
a layer of work function metal material extending along bottom and side surfaces of the block of polysilicon material,
wherein the select gate is insulated from the second portion of the channel region by a layer of silicon dioxide and a layer of high K insulating material;
a control gate disposed over and insulated from the floating gate; and
an erase gate disposed over and insulated from the first region, and disposed laterally adjacent to and insulated from the floating gate.
2. The memory cell of claim 1 , wherein the high K insulating material is at least one of HfO 2 , ZrO 2 , and TiO 2 .
3. The memory cell of claim 1 , wherein the erase gate comprises:
a second block of polysilicon material; and
a layer of work function metal material extending along bottom and side surfaces of the second block of polysilicon material.
4. The memory cell of claim 3 , further comprising:
silicide disposed on an upper surface of the block of polysilicon material; and
silicide disposed on an upper surface of the second block of polysilicon material.
5. The memory cell of claim 4 , wherein the erase gate is insulated from the floating gate by silicon dioxide and by a layer of high K insulating material.
6. The memory cell of claim 1 , further comprising:
silicide disposed on a portion of the substrate in the second region.
7. A method of forming a non-volatile memory cell comprising:
forming, in a substrate of a first conductivity type, spaced apart first and second regions of a second conductivity type, defining a channel region therebetween;
forming a floating gate disposed over and insulated from a first portion of the channel region which is adjacent the first region;
forming a control gate disposed over and insulated from the floating gate;
forming a select gate over and insulated from a second portion of the channel region which is adjacent to the second region, the select gate comprising:
a block of polysilicon material, and
a layer of work function metal material extending along bottom and side surfaces of the block of polysilicon material,
wherein the select gate is insulated from the second portion of the channel region by a layer of silicon dioxide and a layer of high K insulating material;
forming an erase gate disposed over and insulated from the first region, and disposed laterally adjacent to and insulated from the floating gate.
8. The method of claim 7 , wherein the high K insulating material is at least one of HfO 2 , ZrO 2 , and TiO 2 .
9. The method of claim 7 , wherein the erase gate comprises:
a second block of polysilicon material; and
a layer of work function metal material extending along bottom and side surfaces of the second block of polysilicon material.
10. The method of claim 9 , further comprising:
forming silicide on an upper surface of the block of polysilicon material; and
forming silicide on an upper surface of the second block of polysilicon material.
11. The method of claim 9 , wherein the erase gate is insulated from the floating gate by silicon dioxide and by a layer of high K insulating material.
12. The method of claim 7 , further comprising:
forming silicide on a portion of the substrate in the second region.