Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Grooved and refilled with deposited dielectric material
Reexamination Certificate
2000-01-11
2002-11-19
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Grooved and refilled with deposited dielectric material
C438S435000
Reexamination Certificate
active
06482716
ABSTRACT:
BACKGROUND
1. Technical Field
This disclosure relates to semiconductor processing and more particularly, to a semiconductor fabrication method which improves uniformity of recess depths among areas of different trench densities.
2. Description of the Related Art
Semiconductor devices may include trenches formed in semiconductor substrates. These trenches may be filled with a resist material during processing. The resist material may be recessed into the trenches to enable the formation of other structures for the semiconductor devices. Trenches may vary in density across a semiconductor device. For example, some areas of the device may include more trenches in a given area than the number of trenches in another area. The different trench densities often result in non-uniformity of the recess depth of recessed resist layers over areas of different trench densities.
The different trench densities within an area of a semiconductor wafer may lead to a varying thickness of layers deposited on the wafer (for example, due to the volume effect of the trenches). If these layers need to be recessed into the trenches, the different thickness of the deposited layer over areas of high or low trench density leads to different recess etch depths in the trenches. Areas with a high trench density will be recessed deeper into the trenches than areas with a lower trench density, where the deposited layer is thicker.
Therefore, a need exists for a method for recessing trench filler materials which compensates for different trench densities to obtain a substantially even recess depth across the different trench densities.
SUMMARY OF THE INVENTION
A method for forming uniform-depth recesses across areas of different trench density, in accordance with the present invention, includes providing a substrate having trenches formed therein. The substrate includes regions of different trench density. The trenches are filled with a first filler material, and the first filler material is removed from a surface of the substrate. A second filler material is formed over the surface of the substrate such that the depth of the second filler material is substantially uniform across the regions of different trench density. Recesses are formed in the trenches such that the recess depth below the surface of the substrate is substantially uniform across the regions of different trench density.
Another method for forming uniform-depth recesses across areas of different trench density includes providing a substrate having trenches formed therein. The substrate includes at least two regions. Each of the at least two regions has a different trench density. A first filler material is formed over the substrate, and the first filler material fills the trenches in the at least two regions. The first filler material has a depth above the substrate which is a function of the different trench densities. The first filler material is etched to substantially remove the first filler material from a surface of the substrate while leaving the trenches substantially filled with the first filler material. A second filler material is formed over the substrate. The trenches are refilled in the at least two regions. The second filler material has a depth above the substrate which is substantially uniform across the different trench densities of the at least two regions. The first and second filler materials are etched to form recesses in the trenches, and the recesses have a substantially same depth across the different trench densities of the at least two regions.
In other methods of the invention, the first filler material and the second filler material may have a same etch rate. The first filler material and the second filler may include the same material. The first filler material and the second filler may include a resist material. The step of removing the first filler material from a surface of the substrate may include the step of etching the first filler material to form a recess in trenches in a region having a highest density of trenches. The step of removing the first filler material may include etching the first filler material by employing one of an isotropic etching, anisotropic etching and a development process. The step of forming recesses in the trenches may include etching the first and second filler materials by employing one of an isotropic etching, anisotropic etching and a development process. The step of providing a substrate having trenches formed therein may include providing a monocrystalline substrate including regions of different trench density. The step of providing a substrate having trenches formed therein may include providing a dielectric layer including regions of different trench density. The step of providing a substrate having trenches formed therein, the substrate including regions of different trench density may include the step of providing an array region having a first density of trenches and a support region having a second density of trenches.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
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Chaudhuri Olik
Duy Mai Anh
Infineon Technologies North America Corp.
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