Method and structure for performing a chemical mechanical polishing process
View Patent ↗A method for fabricating flash memory devices, e.g., NAND, NOR, is provided. The method includes providing a semiconductor substrate. The method includes forming a second polysilicon layer overlying a plurality of floating gate structures to cause formation of an upper surface provided on the second polysilicon layer. The upper surface has a first recessed region and a second recessed region. The method includes depositing a dielectric material overlying the upper surface to fill the first recessed region and the second recessed region to form a second upper surface region and cover a first elevated region, a second elevated region, and a third elevated region. The method subjects the second upper surface region to a chemical mechanical polishing process to remove the first elevated region, the second elevated region, and the third elevated region to cause formation of a substantially planarized second polysilicon layer free from the fill material.
1. A method for fabricating flash memory devices, the method comprising:
providing a semiconductor substrate;
forming a plurality of isolation regions on portions of the semiconductor substrate;
forming a plurality of floating gate structures from at least a first polysilicon layer overlying the semiconductor substrate, the plurality of floating gate structures including a first floating gate structure, a second floating gate structure, and a third floating gate structure, the first floating gate structure being spaced from the second floating gate structure by at least a first isolation region, the second floating gate structure being spaced from the third floating gate structure by at least a second isolation region, the first isolation region and the second isolation region being from the plurality of isolation regions;
forming a second polysilicon layer overlying the first floating gate structure, the second floating gate structure, and the third floating gate structure;
causing formation of an upper surface provided on the second polysilicon layer, the upper surface having a first recessed region having a first depth within a first vicinity overlying the first isolation region and a second recessed region having a second depth within a second vicinity overlying the second isolation region, the first recessed region being between a first elevated region within a vicinity overlying the first floating gate structure and a second elevated region within a vicinity overlying the second floating gate structure, the second recessed region being between the second elevated region and a third elevated region within a vicinity overlying the third floating gate structure;
depositing a dielectric material overlying the upper surface provided on the second polysilicon layer to fill the first recessed region and the second recessed region to form an upper surface region and cover the first elevated region, the second elevated region, and the third elevated region;
subjecting the upper surface region to a chemical mechanical polishing process to remove a first thickness of the dielectric material while maintaining a first portion of the dielectric material within the first recessed region and while maintaining a second portion of the dielectric material within the second recessed region to form an exposed region of the dielectric material, and maintaining attachment of the second polysilicon layer to the first floating gate structure, second floating gate structure, and third floating gate structure; and
subjecting the exposed region of the dielectric material to the chemical mechanical polishing process to remove the first elevated region, the second elevated region, and the third elevated region to cause formation of a substantially planarized second polysilicon layer free from the dielectric material.
2. The method of claim 1 further comprising forming an oxide on nitride on oxide layer overlying the first floating gate structure, the second floating gate structure, and the third floating gate structure.
3. The method of claim 1 wherein the first floating gate structure, the second floating gate structure, and the third floating gate structure are provided overlying a dielectric layer.
4. The method of claim 1 wherein the first isolation region and the second isolation region are provided by a high density plasma process.
5. The method of claim 1 wherein the first elevated region, the second elevated region, and the third elevated region are characterized by a height of about 500 Angstroms and greater above the first depth or the second depth.
6. The method of claim 1 wherein the first portion of dielectric material provides mechanical support between the first elevated region and the second elevated region; wherein the second portion of the dielectric material provides mechanical support between the second elevated region and the third elevated region.
7. The method of claim 1 wherein the dielectric material comprises a TEOS material.
8. The method of claim 1 wherein the subjecting the exposed region step is free from a breakage of at least the first elevated region, the second elevated region, or the third elevated region.
9. The method of claim 1 wherein the chemical mechanical polishing process comprises a first chemical mechanical polishing process and a second chemical mechanical polishing process.
10. The method of claim 1 wherein the planarized second polysilicon layer is provided for a control gate.
11. A method for fabricating flash memory devices, the method comprising:
providing a semiconductor substrate;
forming at least a first polysilicon layer including at least a first floating gate structure, a second floating gate structure, and a third floating gate structure, the first floating gate structure being spaced from the second floating gate structure by at least a first isolation region, the second floating gate structure being spaced from the third floating gate structure by at least a second isolation region;
forming a second polysilicon layer overlying the first floating gate structure, the second floating gate structure, and the third floating gate structure to cause formation of an upper surface provided on the second polysilicon layer, the upper surface having a first recessed region having a first depth within a first vicinity overlying the first isolation region and a second recessed region having a second depth within a second vicinity overlying the second isolation region, the first recessed region being between a first elevated region within a vicinity overlying the first floating gate structure and a second elevated region within a vicinity overlying the second floating gate structure, the second recessed region being between the second elevated region and a third elevated region within a vicinity overlying the third floating gate structure;
depositing a dielectric material overlying the upper surface provided on the second polysilicon layer to fill the first recessed region and the second recessed region to form an upper surface region and cover the first elevated region, the second elevated region, and the third elevated region to form a upper surface region;
subjecting the upper surface region to a chemical mechanical polishing process to remove a first thickness of the dielectric material while maintaining a first portion of the dielectric material within the first recessed region and while maintaining a second portion of the dielectric material within the second recessed region to form an exposed region of the dielectric material, and maintaining attachment of the second polysilicon layer to the first floating gate structure, second floating gate structure, and third floating gate structure; and
subjecting the exposed region to a chemical mechanical polishing process to remove the first elevated region, the second elevated region, and the third elevated region to cause formation of a substantially planarized second polysilicon layer free from the dielectric material.
12. The method of claim 11 further comprising forming an oxide on nitride on oxide layer overlying the first floating gate structure, the second floating gate structure, and the third floating gate structure.
13. The method of claim 11 wherein the first floating gate structure, the second floating gate structure, and the third floating gate structure are provided overlying a dielectric layer.
14. The method of claim 11 wherein the first isolation region and the second isolation region are provided by a high density plasma process.
15. The method of claim 11 wherein the first elevated region, the second elevated region, and the third elevated region are characterized by a height of about 500 Angstroms and greater above the first depth or the second depth.
16. The method of claim 11 wherein the first portion of the dielectric material provides mechanical support between the first elevated region and the second elevated region.
17. The method of claim 11 wherein the second portion of the dielectric material provides mechanical support between the second elevated region and the third elevated region.
18. The method of claim 11 wherein the subjecting the upper surface region is free from a breakage of at least the first elevated region, the second elevated region, or the third elevated region.
19. The method of claim 11 wherein the chemical mechanical polishing process comprises a first chemical mechanical polishing process and a second chemical mechanical polishing process.
20. The method of claim 11 wherein the planarized second polysilicon layer is provided for a control gate.