Long-distance span air bridge manufacturing method
By forming multiple mesa on the substrate material and depositing metal air bridge surfaces, the photoresist recess problem was solved, and a long-span air bridge structure was realized, improving the controllability of device characteristics and process flow.
Patent Information
- Application Number
- CN202511531490.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-24
- Publication Date
- 2026-03-06
AI Technical Summary
In existing technologies, the photoresist in long-span air bridges is prone to depression after high-temperature baking, which reduces the device characteristics and structural compressive strength. Furthermore, the photoresist is difficult to remove, affecting the long span and design accuracy of the air bridge.
Wet etching is used to form multi-layer mesa on the substrate material, and metal evaporation is used to form air bridges to replace the function of photoresist. The etching depth and time are precisely controlled, and NMP solvent is used to remove the photoresist layer to avoid high-temperature baking.
It achieves a long-span air bridge structure with a flat, dent-free bridge surface, which improves the controllability of device characteristics and process flow, and enhances quality yield.
Smart Images
Figure CN121620191A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for fabricating long-span air bridges. Background Technology
[0002] An air bridge is an interconnect structure used in integrated circuits to electrically connect different metal layers or component surfaces while maintaining physical isolation between the component surfaces. The fabrication process of an air bridge mainly involves steps such as photolithography, sacrificial layer removal, and metal deposition. This is achieved by coating bridge photoresist, followed by exposure / development / high-temperature baking to form an air bridge. Figure 1 The morphology is then further refined through metal vapor deposition to form the bridge surface metal, such as... Figure 2 After removing the light obstruction from the bridge surface, an air bridge is formed, such as... Figure 3 However, in existing technologies, the large span of the bridge deck causes the light obstruction in the central area to become concave after baking, and this trend becomes more pronounced as the span increases, which to some extent limits the long-distance span of the air bridge; for example... Figure 4 As shown, the concavity in the central region of the photoresist affects the height to ground and the characteristics of the device; it causes deviations between the design and actual values; it also reduces the compressive strength of the entire structure; the high-temperature baking of the photoresist may result in incomplete removal; if the baking temperature is insufficient, an arc shape cannot be formed, while bridge surface photoresist requires high-temperature baking to form an arc shape, making the removal of bridge surface photoresist more difficult. Summary of the Invention
[0003] The purpose of this invention is to provide a manufacturing method for long-span air bridges, which can improve the problem of photoresist deformation due to long-distance transconductance and realize long-span air bridge structures.
[0004] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing method for a long-span air bridge, the manufacturing method comprising the following steps:
[0005] Step S1: Deposit a first photoresist layer on the substrate material and expose / develop it. Use wet etching to etch the substrate material with an etching depth of H1 and an etching time of T1 to form a first mesa on the substrate material and remove the first photoresist layer.
[0006] Step S2: Continue to coat the second photoresist layer and perform exposure / development. Use wet etching to etch the substrate material with an etching depth of H2 and an etching time of T2 to form the second mesa on both sides of the first mesa. Remove the second photoresist layer.
[0007] Step S3: Following the operation in step S2, form the third to the nth mesa sequentially, with etching depths from H3 to Hn and etching times from T3 to Tn.
[0008] Step S4: Coat the (n+1)th photoresist layer on the outer side of the nth mesa, expose / develop, and then perform metal evaporation to remove the metal on the outer side of the nth mesa and the (n+1)th photoresist layer, thus completing the air bridge metal deposition.
[0009] Step S5: Coat the (n+2)th photoresist layer, perform exposure / development, and completely etch the substrate material in the vertical direction below the air bridge. The etching depth A satisfies the following conditions: the etching depth A is less than or equal to the horizontal distance E from the leftmost side of the photoresist layer to the bottom of the nth mesa, and the etching depth A is greater than or equal to half of the sum of the etching depths from the first mesa to the nth mesa. Then remove the (n+2)th photoresist layer to complete the air bridge process.
[0010] Furthermore, the etching time in step S5 is the sum of the etching times used from the leftmost mesa of the photoresist layer to the nth mesa.
[0011] Furthermore, the volume ratio of the etching solution used in the wet etching process is ammonia:hydrogen peroxide:water = 1:1.5:10.
[0012] Furthermore, the removal of the first to the nth photoresist layers is performed using NMP solvent.
[0013] Furthermore, the thicknesses of the (n+1)th photoresist layer and the (n+2)th photoresist layer are both greater than the sum of H1, H2...Hn.
[0014] Furthermore, in step S4, the metal used for metal vapor deposition is Ti, Pt, Au, Ti, or Au.
[0015] A long-span air bridge, characterized in that: the air bridge includes piers and a bridge body, with piers connected to both ends of the bridge body, and the bridge body includes a top bridge deck and a stepped bridge deck, with the stepped bridge deck connecting both sides of the top bridge deck.
[0016] Furthermore, the angle between the connecting sections between the steps in the stepped bridge deck and the horizontal plane is 30° to 55°.
[0017] The beneficial effects of this invention are:
[0018] 1. An air bridge surface is formed by etching the substrate, which replaces the function of photoresist, improves the problem of photoresist deformation due to long-distance transconductance, and realizes an air bridge structure with a long span.
[0019] 2. By using a substrate as the bridge surface structure, the air bridge surface formed by metal evaporation replicates the flat substrate interface, achieving an air bridge structure with no depressions in appearance and controllable height to the ground.
[0020] 3. The bridge material is the substrate material. Wet etching is used in the process of forming the air bridge, which effectively avoids the removal difficulties caused by high temperature baking of photoresist, optimizes the process flow, and improves the quality yield.
[0021] 4. The process of this invention is simple, the bridge deck is easy to manufacture, and the platform height is controlled by time, which provides direct data for subsequent etching removal: the time required for complete etching is directly known from the position of the photoresist station. Attached Figure Description
[0022] Figure 1 A schematic diagram of coating photoresist on bridge piers using existing manufacturing methods;
[0023] Figure 2 A schematic diagram of the bridge deck metal formed by metal vapor deposition using existing manufacturing methods;
[0024] Figure 3 A schematic diagram of a bridge deck metal manufactured using existing methods;
[0025] Figure 4 This is a schematic diagram showing a dent that appears after baking using existing manufacturing methods.
[0026] Figure 5 This is a schematic diagram of the deposition of the first photoresist layer using the process method of the present invention.
[0027] Figure 6 A schematic diagram showing the formation of the first mesa using the process method of the present invention;
[0028] Figure 7 This is a schematic diagram of removing the first photoresist layer using the process method of the present invention;
[0029] Figure 8 This is a schematic diagram of the coating of the second photoresist layer using the process method of the present invention;
[0030] Figure 9 This is a schematic diagram illustrating the formation of the second mesa using the process method of the present invention;
[0031] Figure 10 This is a schematic diagram of removing the second photoresist layer using the process method of the present invention.
[0032] Figure 11 This is a schematic diagram of the coating of the third photoresist layer using the process method of the present invention;
[0033] Figure 12 This is a schematic diagram illustrating the formation of the third mesa using the process method of the present invention;
[0034] Figure 13 This is a schematic diagram of removing the third photoresist layer using the process method of the present invention.
[0035] Figure 14 This is a schematic diagram of the fourth photoresist layer being coated using the process method of the present invention;
[0036] Figure 15 This is a schematic diagram of metal vapor deposition using the process method of the present invention;
[0037] Figure 16 This is a schematic diagram of removing the metal and fourth photoresist layer on the outer side of the third mesa using the process method of the present invention.
[0038] Figure 17 This is a schematic diagram of the coating of the fifth photoresist layer using the process method of the present invention;
[0039] Figure 18 This is a schematic diagram of the substrate material under the metal using the process method of the present invention;
[0040] Figure 19 This is a schematic diagram showing the removal of the fifth photoresist layer.
[0041] Among them: 1. Substrate material, 2. First photoresist layer, 3. First mesa, 4. Second photoresist layer, 5. Second mesa, 6. Third photoresist layer, 7. Third mesa, 8. Fourth photoresist layer, 9. Metal, 10. Fifth photoresist layer, 11. Pier, 12. Bridge body, 121. Top bridge deck, 122. Stepped bridge deck. Detailed Implementation
[0042] The invention will now be further described with reference to the accompanying drawings.
[0043] Please see Figures 1 to 19 The present invention provides an embodiment: a manufacturing method for a long-span air bridge, the manufacturing method comprising the following steps:
[0044] Step S1: Deposit a first photoresist layer 2 on 1 and expose / develop it. Use wet etching 1 with an etching depth of H1 and an etching time of T1 to form a first mesa 3 on 1 and remove the first photoresist layer 2.
[0045] Step S2: Continue to coat the second photoresist layer 4 and perform exposure / development. Use wet etching 1 with an etching depth of H2 and an etching time of T2 to form the second mesa 5 on both sides of the first mesa 3 and remove the second photoresist layer 4.
[0046] Step S3: Following the operation in step S2, form the third mesa 7 to the nth mesa sequentially, with etching depths from H3 to Hn and etching times from T3 to Tn.
[0047] Step S4: Coat the (n+1)th photoresist layer on the outer side of the nth mesa, expose / develop, and then perform metal 9 evaporation to remove the metal 9 and the fourth photoresist layer 8 on the outer side of the nth mesa, thus completing the deposition of the air bridge metal 9.
[0048] Step S5: Coat the (n+2)th photoresist layer, perform exposure / development, and completely etch 1 in the vertical direction below the air bridge. The etching depth A satisfies the following conditions: the etching depth A is less than or equal to the horizontal distance E from the leftmost side of the photoresist layer to the bottom of the nth mesa, and the etching depth A is greater than or equal to half of the sum of the etching depths of the first mesa 3 to the nth mesa. Then remove the (n+2)th photoresist layer to complete the air bridge process.
[0049] Please continue reading. Figures 1 to 19 As shown, in one embodiment of the present invention, the etching time in step S5 is the sum of the etching times used from the leftmost mesa of the photoresist layer to the nth mesa.
[0050] Please continue reading. Figures 1 to 19 As shown, in one embodiment of the present invention, the volume ratio of the etching solution used in the wet etching is ammonia: hydrogen peroxide: water = 1:1.5:10.
[0051] Please continue reading. Figures 1 to 19 As shown, in one embodiment of the present invention, the removal of the first photoresist layer 2 to the nth photoresist layer is performed using NMP solvent.
[0052] Please continue reading. Figures 1 to 19 As shown, in one embodiment of the present invention, the thicknesses of the (n+1)th photoresist layer and the (n+2)th photoresist layer are both greater than the sum of H1, H2...Hn.
[0053] Please continue reading. Figures 1 to 19 As shown, in one embodiment of the present invention, the metal 9 deposited in step S4 is Ti, Pt, Au, Ti or Au. Specific Implementation Example 1:
[0055] Taking gallium arsenide as an example, the approach is similar for other materials.
[0056] 1. Deposit the first photoresist layer 2, with a thickness greater than [missing information]. After exposure / development, as Figure 5 The operation involves wet etching with an etching solution volume ratio of ammonia:hydrogen peroxide:water = 1:1.5:10, but this ratio is not strictly limited. The etching rate is R1, and the etching time is T1, so the etching depth is H1 = R1 * T1, forming the first mesa 3. The first photoresist layer 2 is then removed, as follows: Figure 7 As shown; half of the photoresist layer was removed using NMP solvent, and the same solvent was used for the removal of the photoresist layer below;
[0057] II. Coat the second photoresist layer 4, perform exposure / development using the same principle, and then wet etch 1 to form the second mesa 5, with an etching depth of H2 = R1 * T2; (e.g.) Figures 8 to 9 As shown;
[0058] III. Applying the third photoresist layer 6, following the same principle, forms the third mesa 7, such as... Figures 11 to 13 As shown, the etching depth is H3 = R1 * T3; this embodiment takes the air bridge span formed by three platforms as an example, and the platforms can be added according to the design requirements and the air bridge span requirements;
[0059] IV. Coat the fourth photoresist layer 8 with a thickness greater than 1.2µm (this thickness can be adjusted according to the mesa depth; for example, 1.2µm here needs to be greater than the mesa depth H1+H2+H3). After exposure / development, the following morphology is formed: Figure 14 As shown; the operation involves metal 9 vapor deposition. The metal 9 structure commonly uses Ti / Pt / Au / Ti / Au, with a total thickness of generally 2µm, which can be adjusted according to design requirements, such as... Figure 15 As shown; after removing metal 9 and photoresist by NMP, as shown... Figure 16 As shown, air bridge metal 9 deposition was completed;
[0060] 5. Coat the fifth photoresist layer 10 with a thickness greater than 1.2µm (this thickness can be adjusted according to the stage depth; for example, 1.2µm here needs to be greater than the stage depth H1+H2+H3). After exposure / development, the following morphology is formed: Figure 17 As shown; the boundary position of the photoresist pattern must satisfy the following:
[0061] 1. The etching depth A <= E, to ensure complete etching on both sides (measurement refers to both sides of the air bridge cross-section; generally, the lateral etching amount and the ground etching amount in wet etching are 1:1, and the preferred etching ratio is A=E).
[0062] 2. A must be satisfied to ensure that 1 is completely etched in the vertical direction;
[0063] The etching time is determined by the position of the photoresist station's platform. In this embodiment, the photoresist station is on the second platform 5, and etching of the air bridge material can be completed using etching time T2+T3. Figure 18 As shown, if the photoresist is positioned on the first mesa 3, the etching time is T1+T2+T3; and so on, until the photoresist is removed, as... Figure 19 As shown, the air bridge manufacturing process is completed.
[0064] Please see Figure 19 The present invention provides an embodiment of a long-span air bridge, characterized in that: the air bridge includes piers 11 and a bridge body 13, both ends of the bridge body 13 are connected to piers 11, the bridge body 13 includes a top bridge surface 121 and a stepped bridge surface 122, the stepped bridge surface 122 is connected to both sides of the top bridge surface 121.
[0065] Please continue reading. Figure 19As shown, in one embodiment of the present invention, the angle between the connecting segments between the stepped surfaces of the stepped bridge surface 122 and the horizontal plane is 30° to 55°.
[0066] The present invention has the following working principle: an air bridge surface is formed by etching the substrate, which replaces the photoresist and improves the problem of photoresist deformation due to long-distance transconductance, thus realizing an air bridge structure with a long span; the substrate is used as the bridge surface structure, so that the air bridge surface formed by metal 9 vapor deposition replicates the flat substrate interface, realizing an air bridge structure with no appearance depressions and controllable height to ground; the bridge surface material is 1, and wet etching is used in the air bridge formation process, which effectively avoids the removal difficulties caused by high temperature baking of photoresist, optimizes the process flow, and improves the quality yield.
[0067] The above description is only a preferred embodiment of the present invention and should not be construed as a limitation of this application. All equivalent changes and modifications made in accordance with the scope of the patent application of the present invention should be covered by the present invention.
Claims
1. A method for long distance span air-bridge processing, the method comprising: The process method comprises the following steps: Step S1, depositing a first photoresist layer on a substrate material, and performing exposure / development, using wet etching of the substrate material, with an etching depth of H1 and an etching time of T1, to form a first mesa on the substrate material, and removing the first photoresist layer; Step S2, continuing to coat a second photoresist layer, and performing exposure / development, using wet etching of the substrate material, with an etching depth of H2 and an etching time of T2, to form a second mesa on both sides of the first mesa, and removing the second photoresist layer; Step S3, sequentially forming a third mesa to an n-th mesa according to the operation in step S2, with etching depths of H3 to Hn and etching times of T3 to Tn; Step S4, coating an n+1-th photoresist layer on the outside of the n-th mesa, and performing exposure / development, and then performing metal evaporation, to remove the metal on the outside of the n-th mesa and the n+1-th photoresist layer, and complete air bridge metal deposition; Step S5, coating an n+2-th photoresist layer, and performing exposure / development, to etch the substrate material in the vertical direction below the air bridge completely, with an etching depth A satisfying: the etching depth A is less than or equal to a horizontal distance E from the leftmost side of the photoresist layer to the bottom of the n-th mesa, and the etching depth A is greater than or equal to half of the sum of the etching depths of the first mesa to the n-th mesa, and then removing the n+2-th photoresist layer, to complete the air bridge process.
2. The long distance spanned air bridge process method according to claim 1, wherein: The etching time in step S5 is the sum of the etching times of the mesa where the leftmost side of the photoresist layer is located to the n-th mesa.
3. The long distance spanned air bridge process method according to claim 1, wherein: The volume ratio of the etching liquid used in the wet etching is ammonia water: hydrogen peroxide: water = 1:1.5:
10.
4. The long distance span air bridge process method according to claim 1, wherein: The removal of the first photoresist layer to the n-th photoresist layer uses NMP solvent.
5. The long distance span air bridge process method according to claim 1, wherein: The thicknesses of the n+1-th photoresist layer and the n+2-th photoresist layer are both greater than the sum of H1, H2, …, Hn.
6. The process of claim 1, wherein: The metal used in the metal evaporation in step S4 is Ti, Pt, Au, Ti or Au.
7. A long distance span air bridge made by the process of claim 1, wherein: The air bridge comprises a pier and a bridge body, both ends of the bridge body are connected with the pier, the bridge body comprises a top deck and a stepped deck, and the stepped deck is connected to both sides of the top deck.
8. A long distance span airbridge according to claim 7, characterised in that: The angle between the connecting section between the stepped surfaces in the stepped deck and the horizontal plane is 30° to 55°.