Air liner for through substrate via
A first conductive pad disposed over a first side of a substrate in a first direction. A second conductive pad is disposed over a second side of the substrate in the first direction. A through-substrate via (TSV) extends into the substrate in the first direction. The TSV is disposed between the first conductive pad and the second conductive pad in the first direction. An air liner disposed between the TSV and the substrate in a second direction different from the first direction.
1 . A method, comprising:
etching an opening that extends partially into a structure that includes a substrate and an interconnect structure formed over a first side of the substrate, wherein the opening is formed from the first side toward a second side and extends past the interconnect structure;
depositing a liner structure in the opening;
forming a through-substrate via (TSV) structure in the opening, wherein the TSV structure is formed over the liner structure;
thinning the substrate from the second side, wherein the TSV structure is exposed to the second side after the thinning of the substrate; and
removing a portion, but not all, of the liner structure, thereby forming an air liner in place of the removed portion of the liner structure, wherein a remaining portion of the liner structure is disposed laterally adjacent to the interconnect structure.
2 . The method of claim 1 , wherein:
the removing forms a first air liner and a second air liner in place of the removed portion of the liner structure in a cross-sectional side view;
at least a first guard ring structure and a second guard ring structure are formed as a part of the interconnect structure and are disposed over the first side of the substrate in the cross-sectional side view;
the opening separates the first guard ring structure from the second guard ring structure in the cross-sectional side view; and
the first air liner is formed between the first guard ring structure and the TSV structure in the cross-sectional side view, and the second air liner is formed between the second guard ring structure and the TSV structure in the cross-sectional side view.
3 . The method of claim 1 , further comprising, after the removing, sealing the air liner from the second side with an isolation film.
4 . The method of claim 3 , further comprising:
after the forming the TSV structure but before the thinning, forming a first conductive pad over the TSV from the first side; and
after the sealing, forming a second conductive pad over the TSV from the second side, wherein the TSV is electrically coupled to the first conductive pad and the second conductive pad.
5 . The method of claim 4 , further comprising:
forming a third conductive pad over the first side of the first conductive pad; and
forming a conductive bump over the first side of the third conductive pad, wherein the conductive bump, the third conductive pad, and the first conductive pad are electrically coupled together.
6 . The method of claim 3 , wherein the sealing the air liner is performed at least in part by depositing a dielectric material as the isolation film from the second side, and wherein the dielectric material protrudes into the air liner.
7 . The method of claim 1 , wherein the depositing the liner structure comprises depositing a dielectric liner having a dielectric constant lower than a dielectric constant of silicon dioxide.
8 . The method of claim 1 , wherein:
the depositing comprises depositing a first liner layer as a bottom layer of the liner structure, a second liner layer as a middle layer of the liner structure, and a third liner layer as a top layer of the liner structure;
the TSV structure is deposited over the third liner layer; and
the removing comprises at least partially removing the second liner layer without substantially affecting the first liner layer or the third liner layer.
9 . The method of claim 8 , wherein the removing comprises completely removing the second liner layer.
10 . The method of claim 8 , wherein:
the depositing comprises depositing a first type of oxide material as the first liner layer and the third liner layer, and depositing a second type of oxide material as the second liner layer; and
the removing comprises performing an etching process having an etching selectivity between the first type of oxide material and the second type of oxide material.
11 . The method of claim 1 , wherein a portion of the liner structure is deposited over a first side of the interconnect structure, and wherein the forming of the TSV structure removes the portion of the liner structure deposited over the first side of the interconnect structure.
12 . A method, comprising:
forming an opening in a structure that includes a substrate and an interconnect structure that is disposed over a first side of the substrate, the opening extending from a first side toward a second side and extending past the interconnect structure;
forming a dielectric liner in the opening, wherein the dielectric liner contains a material having a dielectric constant that is lower than a dielectric constant of silicon dioxide;
forming a through-substrate via (TSV) in the opening, the TSV being formed over the dielectric liner;
removing portions of the substrate from the second side until a portion of the TSV is exposed to the second side;
etching away a portion, but not all, of the dielectric liner, wherein an air gap is formed in place of the portion of the dielectric liner that has been etched away, and wherein a remaining portion of the dielectric liner is disposed laterally adjacent to the interconnect structure; and
sealing the air gap from the second side with an isolation film.
13 . The method of claim 12 , wherein:
a first guard ring and a second guard ring are formed as a part of the interconnect structure; and
the opening is formed such that it separates the first guard ring from the second guard ring.
14 . The method of claim 12 , further comprising:
after the TSV has been formed but before the portion of the dielectric liner has been etched away, forming a first conductive pad over the TSV from the first side; and
after the sealing, forming a second conductive pad over the TSV from the second side, wherein the TSV is electrically coupled to the first conductive pad and the second conductive pad.
15 . The method of claim 12 , wherein:
the dielectric liner includes a bottom segment, a middle segment, and a top segment;
the TSV is formed over the top segment; and
the etching away comprises removing the middle segment but not the bottom segment or the top segment.
16 . The method of claim 15 , wherein:
the bottom segment and the top segment have a first material composition;
the middle segment has a second material composition different from the first material composition; and
the middle segment is removed at least in part via an etching process having an etching selectivity between the first material composition and the second material composition.
17 . A method, comprising:
etching an opening into a structure that includes a substrate and an interconnect structure, wherein the opening extends from a first side of the substrate toward a second side of the substrate, and wherein a portion of the opening is formed laterally adjacent to the interconnect structure;
depositing a liner structure in the opening, wherein the liner structure includes a dielectric material;
forming a conductive via in the opening, wherein the conductive via is formed over the liner structure;
reducing a thickness of the substrate from the second side until the conductive via is exposed to the second side;
removing a portion, but not all, of the liner structure, wherein an air liner is formed in place of the removed portion of the liner structure, and wherein a remaining portion of the liner structure is located laterally adjacent to the interconnect structure; and
forming an isolation film over the air liner from the second side of the substrate.
18 . The method of claim 17 , wherein:
at least a first guard ring structure and a second guard ring structure are formed as a part of the interconnect structure; and
the air liner is formed between the first guard ring structure and the conductive via.
19 . The method of claim 18 , further comprising:
after the forming the conductive via but before the reducing the thickness, forming a first conductive pad over the conductive via from the first side of the substrate; and
after the forming the isolation film, forming a second conductive pad over the conductive via from the second side of the substrate, wherein the conductive via is electrically coupled to the first conductive pad and the second conductive pad.
20 . The method of claim 17 , wherein:
the depositing the liner structure comprises depositing a first liner layer containing a first type of dielectric material, a second liner layer containing a second type of dielectric material, and a third liner layer containing the first type of dielectric material;
the conductive via is formed over the third liner layer; and
the removing the portion of the liner structure comprises performing an etching process having a greater etching rate with respect to the second type of dielectric material than with respect to the first type of dielectric material.