Via in substrate with deposited layer
An opening such as a small-diameter via is formed in a semiconductor substrate such as a monocrystalline silicon chip or wafer by a high etch rate process which leaves the opening with a rough interior surface. A smoothing layer such as a polysilicon layer is applied over the interior surfaces of the openings. The smoothing layer presents a surface smoother than the original interior surface. An insulating layer is formed over the smoothing layer or formed from the smoothing layer, and a conductive element such as a metal is formed in the opening. In a variant, a glass-forming material such as BPSG is applied in the opening. The glass-forming material is reflowed to form a glassy insulating layer which presents a smooth surface. The interface between the metal conductive element and the insulating or glassy layer is smooth, which improves mechanical and electrical properties.
1. A method of treating a microelectronic substrate, comprising:
forming an opening extending at least partially through a semiconductor region of the microelectronic substrate such that a monocrystalline semiconductor material of the semiconductor region is exposed at an interior surface of the opening and the interior surface has a surface roughness, the interior surface of the opening being comprised of a sidewall surface, a bottom surface joined to the sidewall surface, and a plurality of recesses in at least the sidewall surface;
depositing a smoothing layer by:
exposing the opening to a vapor comprising a silicon-bearing material, wherein at least some silicon material from the silicon-bearing material preferentially deposits in the plurality of recesses upon a decomposition of the silicon-bearing material, and
maintaining the interior surface at a temperature that enables at least a portion of the silicon material to crystallize onto the monocrystalline semiconductor material as crystals of polysilicon preferentially filling-in the plurality of recesses to provide the smoothing layer;
wherein the smoothing layer has an exposed surface with surface roughness less than the surface roughness of the interior surface; and
forming an insulating layer overlying or integral with the smoothing layer within the opening.
2. The method of claim 1 , further comprising the step of forming an electrically conductive element overlying a surface of the insulating layer within the opening, such that the insulating layer is disposed between the electrically conductive element and the interior surface of the opening.
3. The method of claim 1 , wherein the step of forming the opening is performed using an anisotropic etching process with an etch rate greater than 10 microns per minute.
4. The method of claim 1 , wherein the interior surface has a surface roughness of at least 100nanometers, the smoothing layer is formed to an average thickness of less than 300 nanometers, and the insulating layer is formed to a thickness of less than 50 nanometers.
5. The method of claim 1 , wherein the semiconductor region has a monocrystalline structure and the step of forming the opening is performed such that the exposed semiconductor material has monocrystalline structure.
6. The method of claim 1 wherein the silicon-bearing material consists essentially of polysilicon.
7. The method of claim 1 wherein the silicon-bearing material consists essentially of silicon alone or in combination with at least one of N, C, H, and O.
8. The method of claim 1 further comprising depositing a buffer layer on the interior surface before depositing the smoothing layer, the buffer layer being thinner than the smoothing layer.
9. The method of claim 1 , wherein the step of forming the opening includes anisotropically etching the semiconductor region.
10. The method of claim 1 , wherein the step of forming the opening forms the opening extending from a first surface of the substrate only partially through the semiconductor region, the method further comprising exposing at least a portion of the electrically conductive element from a side of the substrate opposite the first surface of the substrate.
11. The method of claim 10 , wherein the step of exposing the portion of the electrically conductive element includes thinning the substrate from the side of the substrate opposite the first surface of the substrate.
12. The method of claim 1 , wherein step of forming the insulating layer includes depositing a dielectric material over the smoothing layer within the opening.
13. The method of claim 12 , wherein the dielectric material is deposited using a tetraethylorthosilicate (“TEOS”) precursor.
14. The method of claim 12 , wherein the insulating layer comprises a glass.
15. The method of claim 12 , further comprising the step of forming an electrically conductive element which includes copper within the opening, such that the insulating layer is disposed between the electrically conductive element and the interior surface of the opening.
16. The method of claim 15 wherein the glass includes a boron-containing glass.
17. The method of claim 1 wherein the step of forming an insulating layer includes treating the smoothing layer with a reactant to convert at least a portion of the smoothing layer to a dielectric.
18. The method of claim 17 wherein the smoothing layer includes silicon and the step of treating the smoothing layer includes converting at least a portion of the silicon in the smoothing layer to silicon dioxide.
19. A method of treating a microelectronic substrate comprising:
forming an opening extending at least partially through a body of the microelectronic substrate such that a material of the body is exposed at an interior surface of the opening and the interior surface has surface roughness, the interior surface of the opening being comprised of a sidewall surface, a bottom surface joined to the sidewall surface, and a plurality of recesses in at least the sidewall surface;
exposing the opening to a vapor comprising a silicon-bearing material, wherein at least a component of the silicon-bearing material preferentially deposits into the plurality of recesses in the material of the body;
maintaining the interior surface at a temperature to enable the component of the silicon-bearing material to deposit into the plurality of recesses to provide a smoothing layer with an exposed surface having a surface roughness less than the surface roughness of the interior surface; and
forming an electrically conductive element within the opening so that the smoothing layer is disposed between the electrically conductive element and the interior surface.
20. The method of claim 19 wherein the step of exposing the opening to a vapor is performed by a low temperature chemical vapor deposition (“CVD”) process.
21. The method of claim 19 , wherein the step of forming the electrically conductive element includes depositing at least one of copper or copper alloy within the opening.
22. The method of claim 19 wherein the body includes photochromic glass and the step of forming an opening includes selectively exposing portions of the glass to radiant energy, heat-treating the body to convert the exposed portions to a glass ceramic, and then exposing the body to an etchant which preferentially attacks the glass ceramic.
23. The method of claim 1 , wherein a diameter of the opening is between approximately 1 micron to approximately 20 microns.
24. The method of claim 1 , wherein the temperature is between approximately 250° C. to approximately 550° C.
25. The method of claim 1 , wherein the smoothing layer provides a crystallinity transition between the monocrystalline semiconductor material of the semiconductor region and the insulating layer;
wherein the smoothing layer possesses physical properties including a lattice constant and a coefficient of thermal expansion closer to that of the monocrystalline semiconductor material than to that of the insulating layer; and
wherein the smoothing layer provides a crystallinity transition buffer between the monocrystalline semiconductor material of the body and the insulating layer.
26. The method of claim 8 , wherein the buffer layer comprises a few atomic layers of carbon.
27. The method of claim 1 , wherein the plurality of recesses comprise jagged, undercut recesses, the plurality of recesses undercut in the opening with respect to a main surface of the microelectronic substrate; and
wherein at least a silicon of the silicon-bearing material preferentially deposits in the plurality of jagged and undercut recesses.