Air bridge structure and manufacturing method thereof, and superconducting quantum chip and manufacturing method thereof

1 . A manufacturing method for an air bridge structure, comprising:

forming a first photoresist structure on a substrate, the first photoresist structure comprising a first photoresist layer on the substrate and a second photoresist layer on the first photoresist layer, the first photoresist structure comprising a first opening that reveals the substrate, the first opening comprising a first sub-opening through the second photoresist layer and a second sub-opening through the first photoresist layer, a first width of the first sub-opening being less than a second width of the first sub-opening such that widths of the first sub-opening decrease with increasing distance from the substrate, and the second width of the first sub-opening through the second photoresist layer being greater than a width of the second sub-opening through the first photoresist layer;

forming a bridge supporting structure on the substrate, (i) both the bridge supporting structure and the first photoresist structure being sacrificial structures, (ii) the bridge supporting structure being arranged in the first opening in the first photoresist structure and having a sloped profile that is formed based on the first width of the first sub-opening being less than the second width of the first sub-opening, (iii) both the bridge supporting structure and the first photoresist layer being directly deposited on the substrate, and (iv) a height of the bridge supporting structure being larger than a height of the first photoresist layer;

stripping the first photoresist structure after the deposition of the bridge supporting structure;

forming a second photoresist structure on the substrate, the second photoresist structure comprising at least a second opening that reveals at least a portion of the bridge supporting structure on the substrate; and

forming the air bridge structure by depositing an air bridge material on the substrate based on the second opening and stripping the second photoresist structure after the deposition of the air bridge material.

2 . The manufacturing method according to claim 1 , wherein the forming the first photoresist structure further comprises:

forming a stack of the first photoresist layer and the second photoresist layer on the substrate;

forming the first sub-opening of the first opening in the second photoresist layer using first photolithography reactions without a participation by the first photoresist layer in the first photolithography reactions, the forming the first sub-opening generating an undercut structure; and

forming the second sub-opening of the first opening in the first photoresist layer based on the first sub-opening, the second sub-opening revealing the substrate.

3 . The manufacturing method according to claim 2 , wherein the forming the stack of the first photoresist layer and the second photoresist layer further comprises:

cleaning and oxidizing the substrate;

coating the substrate with the first photoresist layer;

performing a first baking process;

coating the second photoresist layer on the first photoresist layer; and

performing a second baking process.

4 . The manufacturing method according to claim 3 , wherein the coating the substrate with the first photoresist layer and the performing the first baking process comprises:

coating the first photoresist layer with a thickness of h 1 , wherein 5 h 1 SH136 h 1 , and H 1 is a height of the bridge supporting structure; and

performing the first baking process at a soft baking temperature of the first photoresist layer.

5 . The manufacturing method according to claim 4 , wherein:

the coating the second photoresist layer on the first photoresist layer comprises coating the second photoresist layer with a thickness of h 2 , wherein h 1 +h 2 >H 1 ; and

the performing the second baking process comprises performing the second baking at a soft baking temperature of the second photoresist layer.

6 . The manufacturing method according to claim 2 , wherein the forming the first sub-opening of the first opening in the second photoresist layer further comprises:

under-exposing the second photoresist layer based on a pattern associated with the bridge supporting structure;

prebaking the second photoresist layer after the under-exposing; and

developing and fixing the second photoresist layer, to obtain the first sub-opening that comprises the undercut structure, wherein the first photoresist layer is not subjected to the developing and the fixing of the second photoresist layer.

7 . The manufacturing method according to claim 6 , wherein:

the under-exposing the second photoresist layer comprises under-exposing the second photoresist layer using an ultraviolet exposure process or a laser direct writing process; and

the prebaking the second photoresist layer comprises prebaking the second photoresist layer at a prebaking temperature of the second photoresist layer.

8 . The manufacturing method according to claim 2 , wherein the forming the second sub-opening of the first opening in the first photoresist layer further comprises:

etching the first photoresist layer by using the second photoresist layer with the first sub-opening as a mask, to form at least the second sub-opening in the first photoresist layer.

9 . The manufacturing method according to claim 8 , wherein the etching the first photoresist layer comprises:

etching the first photoresist layer based on at least one of a physical etching process and a chemical etching process, to form the second sub-opening through the first photoresist layer.

10 . The manufacturing method according to claim 1 , wherein the forming the bridge supporting structure on the substrate comprises:

depositing, with an electron beam evaporation method or a thermal evaporation method, at least one of silicon dioxide, nickel-gold alloy, zinc oxide, aluminum oxide, or copper oxide as the bridge supporting structure; and

stripping the first photoresist structure in a photoresist stripping liquid at a temperature of 20° C. to 100° C.

11 . The manufacturing method according to claim 1 , wherein the forming the second photoresist structure comprises:

coating, a third photoresist layer on the bridge supporting structure;

performing a third baking process;

under-exposing the third photoresist layer;

prebaking the third photoresist layer;

developing and fixing the third photoresist layer, to obtain the second opening in the third photoresist layer; and

etching, based on the second opening, to remove residual photoresist and an oxidized layer on the substrate.

12 . The manufacturing method according to claim 11 , wherein:

the coating the third photoresist layer further comprises coating the third photoresist layer with a thickness h 3 , wherein H 1 +H 2 ≤3h 3 , H 1 is a height of the bridge supporting structure and H 2 is a thickness of the air bridge structure; and

the performing the third baking process comprises performing the third baking process at a soft baking temperature of the third photoresist layer.

13 . The manufacturing method according to claim 11 , wherein the etching to remove the residual photoresist and the oxidized layer on the substrate comprises:

etching, using at least one of a physical etching process or a chemical etching process, to remove the residual photoresist and the oxidized layer on the substrate.

14 . The manufacturing method according to claim 1 , wherein the forming the air bridge structure comprises:

depositing, based on an electron beam deposition process or a molecular beam deposition process, the air bridge material; and

stripping, based on a soaking process or an ultrasonic process at a temperature of 20° C. to 100° C., the second photoresist structure.

15 . The manufacturing method according to claim 1 , further comprising:

removing the bridge supporting structure with a chemical etching method to obtain the air bridge structure.

16 . The manufacturing method according to claim 15 , wherein the removing the bridge supporting structure further comprises:

using an etching gas that reacts with the bridge supporting structure and lacks reaction with the air bridge material.

17 . The manufacturing method according to claim 15 , wherein the bridge supporting structure is silicon dioxide, the air bridge material is an electrically conductive material that does not react with hydrogen fluoride, and the removing the bridge supporting structure comprises:

introducing a catalytic gas into an etching machine for removing the bridge supporting structure;

introducing a hydrogen fluoride gas into the etching machine to etch the bridge supporting structure; and

introducing a nitrogen gas into the etching machine to remove substances generated during a reaction of the hydrogen fluoride gas with the bridge supporting structure.

18 . The manufacturing method according to claim 17 , wherein the catalytic gas comprises gaseous water, ethanol, methanol, and isopropanol.

19 . The manufacturing method according to claim 17 , wherein the hydrogen fluoride gas is anhydrous hydrogen fluoride gas.