Preparation method of self-coiled inductor without negative magnetic coupling effect

Abstract

The present application belongs to the technical field of electronic device manufacturing, and particularly relates to a preparation method of a self-coiled inductor without negative magnetic coupling effect. The preparation operation steps mainly comprise: (1) sequentially depositing a sacrifice layer, an oxidation protection layer and a double-frequency silicon nitride strain layer on a substrate, and determining an operation mesa by first photoetching; (2) depositing a metal conductive layer by second photoetching; (3) punching holes on adjacent inductor units by third photoetching, and filling the holes with metal to form connecting metal columns; and (4) opening etching windows by fourth photoetching, etching the sacrifice layer by dry etching or wet etching, and triggering coiling by using the film stress of the double-frequency silicon nitride to obtain a self-coiled inductor without negative magnetic coupling. The self-coiled inductor without negative magnetic coupling effect utilizes the punching process, designs a new structure, changes the current direction of adjacent inductor units, and further eliminates the magnetic coupling effect. Compared with a classical one-way coiled structure, the inductance value is increased by 25%, and compared with a two-way coiled structure, the inductance value is increased by 12%.

Description

Technical Field

[0001] This invention belongs to the field of electronic device manufacturing technology, specifically relating to a method for preparing a self-curling inductor without negative magnetic coupling effect. Background Technology

[0002] Inductors are a crucial component of integrated circuits, and their miniaturization and high performance remain key research focuses. While commonly used planar spiral inductors offer advantages such as simple structure and low manufacturing cost, they generally occupy a large area. For example, a 10nH planar spiral inductor has a large footprint and a maximum quality factor of 6. Recent developments in self-rolling inductors have significantly reduced the inductor's footprint while maintaining or even improving its quality factor, driving the miniaturization of passive devices. Classical self-rolling inductors are based on silicon nitride thin films, achieved by etching a sacrificial layer and utilizing the film stress of low-frequency and high-frequency silicon nitride to achieve the roll-up. However, in classical self-rolling inductors, the current flows in opposite directions within adjacent inductor cells, resulting in negative magnetic coupling and impacting inductor performance. Existing bidirectional self-curling inductors, compared to classic unidirectional self-curling inductors, have half of their adjacent inductor units with the same current direction, which reduces the negative magnetic coupling effect to some extent and can increase the inductance value by 10%. However, it does not completely eliminate the negative magnetic coupling effect. Summary of the Invention

[0003] To eliminate the negative magnetic coupling effect of existing self-curling inductors, this invention provides a method for fabricating a self-curling inductor without negative magnetic coupling. This invention is achieved through the following technical solution:

[0004] A method for fabricating a self-curling inductor without negative magnetic coupling effect, the specific operation steps are as follows:

[0005] Step 1): Clean the substrate.

[0006] Clean substrate 1 according to the standardized cleaning process and blow it dry;

[0007] Step 2): Deposit a germanium sacrificial layer

[0008] A germanium sacrificial layer 2 is deposited on a cleaned substrate 1 using a vacuum deposition machine;

[0009] Step 3): Deposit an oxide protective layer using the ALD atomic layer deposition method.

[0010] An oxide protective layer 3 was deposited on the germanium sacrificial layer 2 using ALD atomic layer deposition;

[0011] Step 4): Deposit dual-frequency silicon nitride

[0012] Using PECVD plasma-enhanced chemical vapor deposition, a low-frequency silicon nitride thin film, namely the lower stress layer 4, is first deposited on the oxide protective layer 3 as a stretching layer, and then a high-frequency silicon nitride thin film, namely the upper stress layer 5, is deposited as a compression layer.

[0013] Step 5): First photolithography step to determine the operating table surface

[0014] Step 5.1): First application of adhesive, exposure, and development.

[0015] HMDS hexamethylsilane is spin-coated onto the surface of the upper stress layer 5 to form a film, followed by spin-coating of liquid positive photoresist. Using an i-line contact lithography machine, the photoresist portion to be retained is blocked, and the mesa pattern on the first mask is transferred to the surface of the upper stress layer 5. After exposure and development, a positive photoresist layer 8 is obtained on the upper stress layer 5. The positive photoresist layer 8 includes spaced and uniformly distributed square photoresist blocks, i.e., the transferred mesa pattern.

[0016] Step 5.2): Reactive Ion Etching (RIE)

[0017] Using a reactive ion etching (RIE) apparatus, the upper stress layer 5, lower stress layer 4, oxide protective layer 3, and germanium sacrificial layer 2 that are not covered by the positive photoresist layer 8 are etched away, and a shallow layer is etched downwards onto the substrate 1.

[0018] Step 5.3): Remove the liquid phase positive photoresist.

[0019] Remove the positive photoresist layer 8, and retain the upper stress layer 5, lower stress layer 4, oxide protective layer 3 and germanium sacrificial layer 2 below the positive photoresist layer 8 to obtain multiple unit substrates;

[0020] Step 6): Second photolithography deposition of the conductive metal layer

[0021] Step 6.1): Second application of adhesive, exposure, and development.

[0022] HMDS hexamethylsilane is spin-coated onto the surface of the upper stress layer 5 of the unit substrate for film formation, followed by spin-coating of liquid negative photoresist. Using an i-line contact lithography machine, a second mask is used for overlay alignment, exposure, and development to obtain the upper first liquid negative photoresist layer 9. The first liquid negative photoresist layer 9 has a second mask cutout pattern 91, and the second mask cutout pattern 91 is a Z-shape arranged side by side.

[0023] Step 6.2): ​​Deposit a conductive metal layer

[0024] On the substrate obtained in the previous step, a metal conductive layer 6 is vacuum deposited using an electron beam evaporation device.

[0025] Step 6.3): Prepare a metal substrate with a metallic pattern.

[0026] The first liquid negative photoresist layer 9 is completely removed with a photoresist remover. At this time, the metal conductive layer 6 located on the first liquid negative photoresist layer 9 is also removed, resulting in a metal substrate 61 with the pattern of the second photomask.

[0027] Step 7): Third photolithography drilling

[0028] Steps: 7.1) Third coating of adhesive, exposure, development, etching

[0029] HMDS hexamethylsilane is spin-coated onto the substrate after the previous step to form a film. Liquid negative photoresist is then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate is exposed and developed on a third mask. The liquid negative photoresist above the third mask is removed to obtain a second liquid negative photoresist layer 10. The second liquid negative photoresist layer 10 has a third mask cutout pattern 101. The third mask cutout pattern 101 is a series of circles arranged side by side, so that the circles correspond one-to-one with the horizontal upper end of the Z-shape of the metal substrate 61.

[0030] Step 7.2): ICP inductively coupled plasma etching

[0031] Using an ICP inductively coupled plasma etching device, the metal substrate 61, upper stress layer 5, lower stress layer 4 and oxide protective layer 3 corresponding to the bottom of the circle are etched away to obtain a cylindrical hole;

[0032] Step 7.3): Plate the bonding metal layer and remove the adhesive.

[0033] On the substrate after the previous step, a connecting metal layer is deposited using a magnetron sputtering device. This will fill the cylindrical hole and obtain a connecting metal pillar 11 that penetrates the conductive metal layer 6, the upper stress layer 5, the lower stress layer 4, and the oxide protective layer 3.

[0034] Then, the second liquid negative photoresist layer 10 is removed using a photoresist remover, and the connecting metal layer attached to the second liquid negative photoresist layer 10 is removed accordingly.

[0035] Step 8): Fourth photolithography to determine the etching window

[0036] HMDS hexamethylsilane is spin-coated onto the substrate obtained in the previous step to form a film. Liquid negative photoresist is then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate is exposed and developed using a fourth mask. The liquid negative photoresist above the third mask is removed to obtain a third liquid negative photoresist layer 12. The third liquid negative photoresist layer 12 has a fourth mask cutout pattern 121. The fourth mask cutout pattern 121 is elongated and serves as an etching window. The etching window is opened on one side of the third liquid negative photoresist layer 12 corresponding to the metal pillar 11.

[0037] Step 9): Remove the oxide protective layer inside the etching window.

[0038] Using reactive ion etching (RIE), the metal substrate 61, upper stress layer 5, lower stress layer 4, and oxide protective layer 3 below the etching window are vertically etched downwards.

[0039] Step 10): Fabrication of a metal structure self-rolling inductor

[0040] The substrate obtained in the previous step is placed in the resist remover to remove the remaining third liquid negative photoresist layer 12; the germanium sacrificial layer 2 is etched through the etching window using dry or wet etching, so that the upper stress layer 5 and the lower stress layer 4, i.e., the dual-frequency silicon nitride, roll forward with the metal substrate 61 to obtain a micro-nano tubular self-rolling inductor.

[0041] Step 11): Rapid annealing

[0042] The micro-nano tubular self-rolling inductor obtained above is placed in a tubular annealing furnace and rapidly annealed under nitrogen pressure at a temperature of 250℃-500℃ and an annealing time of 60s-120s. This will melt the connecting metal pillar 11. The melted connecting metal pillar 11 can connect the upper and lower horizontal ends of adjacent Z-shapes of the metal substrate 61, that is, connect adjacent inductor units.

[0043] Furthermore, in step 1), when the material of the substrate 1 is silicon, a silicon dioxide insulating layer needs to be grown on the silicon surface to achieve electrical isolation between layers.

[0044] Further, in step 2), the thickness of the germanium sacrificial layer 2 is 30-120 nm; in step 3), the thickness of the oxide protective layer 3 is 1-20 nm, and the material is aluminum oxide or hafnium dioxide; in step 4), the low-frequency silicon nitride thin film, i.e., the lower stress layer 4, serves as a stretching layer, and the thickness is 15 nm-40 nm; the high-frequency silicon nitride thin film, i.e., the upper stress layer 5, serves as a compression layer, and the thickness is 15 nm-40 nm; the thickness of the metal conductive layer 6 is 40 nm-200 nm, and the material is one of silver, gold, aluminum, copper, or zinc.

[0045] Furthermore, in step 10), the inner diameter of the self-curling inductor is 1-300 μm, the spacing between adjacent inductor units is 1-70 μm, and the number of curling turns is one turn.

[0046] Furthermore, in step 10), when the material of the metal substrate 61 is copper, dry etching is used;

[0047] Dry etching involves placing the substrate in a chamber containing xenon difluoride gas. The xenon difluoride gas enters the etching window to etch the germanium sacrificial layer 2, thereby achieving curling.

[0048] Furthermore, in step 10), when the material of the selected substrate 1 is silicon, wet etching is used;

[0049] Wet etching involves immersing the substrate in a hydrogen peroxide solution and etching the germanium sacrificial layer 2 through the etching window 7 to achieve curling. Further, in step 11), the connecting metal pillar 11 is made of tin metal with a melting point of 231.89°C. Rapid annealing will melt the connecting metal pillar 11, and the melted metal will enable the metal substrates 61 of adjacent inductor units to connect, i.e., adjacent inductor units are connected.

[0050] The beneficial technical effects of the present invention are as follows:

[0051] (1) The present invention provides a method for preparing a self-rolling inductor without negative magnetic coupling effect. Based on self-rolling technology, the method uses dry etching or wet etching to etch the germanium sacrificial layer through the etching window, so that the upper stress layer and the lower stress layer, i.e., the dual-frequency silicon nitride, roll forward with the metal substrate to obtain a micro-nano tubular self-rolling inductor. The self-rolling inductor occupies a small area. At the same time, the method uses a drilling process to obtain a connecting metal pillar that penetrates the metal conductive layer, the upper stress layer, the lower stress layer and the oxide protective layer. When the self-rolling inductor is placed in a tubular annealing furnace and rapidly annealed under nitrogen pressure, the connecting metal pillar will melt. The melted connecting metal pillar can connect the horizontal upper and lower ends of the adjacent Z-shaped metal substrate, i.e., connect adjacent inductor units. This connection method of adjacent inductor units can make the current direction of the entire inductor consistent, thereby eliminating the magnetic coupling effect.

[0052] (2) The curling thickness, curling radius, spacing between adjacent inductor units, and number of inductor units connected in series are all adjustable in the self-curling inductor without negative magnetic coupling effect of the present invention. Moreover, it can realize the combination of an odd number of inductor units. Adjusting the parameters mentioned above can further optimize the device performance of the self-curling inductor without negative magnetic coupling. For example, under the same parameters in Example 1, the inductance value of the self-curling inductor of the present invention is increased by 25% compared with the classic unidirectional curling inductor and by 12% compared with the bidirectional curling inductor. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of a self-curling inductor without negative magnetic coupling effect according to the present invention.

[0054] Figure 2 for Figure 1 A partial structural diagram.

[0055] Figure 3 for Figure 1 A cross-sectional view.

[0056] Figure 4 This is a schematic diagram of step 5.1) of the present invention.

[0057] Figure 5 This is a schematic diagram of step 5.2 of the present invention.

[0058] Figure 6 This is a schematic diagram of the substrate obtained in step 5.3 of the present invention.

[0059] Figure 7 This is a schematic diagram of step 6.1 of the present invention.

[0060] Figure 8 This is a schematic diagram of step 6.2 of the present invention.

[0061] Figure 9 This is a schematic diagram of step 6.3 of the present invention.

[0062] Figure 10 This is a schematic diagram of step 7.1 of the present invention.

[0063] Figure 11 This is a schematic diagram of step 7.2 of the present invention.

[0064] Figure 12 This is a schematic diagram of step 7.3 of the present invention.

[0065] Figure 13 This is a schematic diagram of step 8) of the present invention.

[0066] Figure 14 This is a schematic diagram of step 9) of the present invention.

[0067] Figure 15 A schematic diagram of step 10) of the present invention.

[0068] Figure 16 This is a mask pattern for a classic unidirectional coiled inductor, including a schematic diagram of the current flow direction.

[0069] Figure 17 A mask pattern for a bidirectional coiled inductor, including a schematic diagram of the current flow direction.

[0070] Figure 18 This is a schematic diagram showing the current flow direction of the mask pattern for the novel coiled structure inductor of the present invention.

[0071] Figure 19 The graph shows the relationship between the effective inductance and the operating frequency for unidirectional coiled, bidirectional coiled, and the novel coiled inductor structure of this invention.

[0072] Figure 20 This is a schematic diagram of the structure of the second mask in Example 1.

[0073] Figure 21 This is a schematic diagram of the structure of the second mask in Example 2.

[0074] Figure 22This is a schematic diagram of the structure of the self-curling inductor in Example 2.

[0075] Figure 23 This is a schematic diagram of the structure of the second mask in Example 3.

[0076] Figure 24 This is a schematic diagram of the structure of the self-curling inductor in Example 3.

[0077] The labels are as follows: 1. Substrate; 2. Germanium sacrificial layer; 3. Alumina protective layer or hafnium dioxide protective layer; 4. Lower stress layer; 5. Upper stress layer; 6. Metal conductive layer; 6. Metal substrate; 8. Positive photoresist layer; 9. First liquid negative photoresist layer; 9. Second mask cutout pattern; 10. Second liquid negative photoresist layer; 10. Third mask cutout pattern; 11. Connecting metal pillar; 12. Third liquid negative photoresist layer; 12. Fourth mask cutout pattern. Detailed Implementation

[0078] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0079] Example 1

[0080] See Figures 1-3 A method for fabricating a self-curling inductor without negative magnetic coupling effect is described below, with the specific steps as follows:

[0081] Step 1): Clean the substrate.

[0082] The sapphire substrate 1 was cleaned and dried according to the standardized cleaning process.

[0083] Step 2): Deposit a germanium sacrificial layer

[0084] A 60nm germanium sacrificial layer 2 was deposited on a cleaned substrate 1 using a vacuum deposition machine.

[0085] Step 3): Deposit an oxide protective layer using the ALD atomic layer deposition method.

[0086] A 10 nm aluminum oxide protective layer 3 was deposited on the germanium sacrificial layer 2 using ALD atomic layer deposition;

[0087] Step 4): Deposit dual-frequency silicon nitride

[0088] Using PECVD plasma-enhanced chemical vapor deposition, a 30nm low-frequency silicon nitride thin film, i.e., the lower stress layer 4, is first deposited on the alumina protective layer 3 as a stretching layer, and then a 30nm high-frequency silicon nitride thin film, i.e., the upper stress layer 5, is deposited as a compression layer.

[0089] Step 5): First photolithography step to determine the operating table surface

[0090] Step 5.1): First application of adhesive, exposure, and development.

[0091] HMDS (hexamethylsilane) was spin-coated onto the surface of the upper stress layer 5 for film formation, followed by spin-coating of liquid positive photoresist. Using an i-line contact lithography machine, the portion of photoresist to be retained was blocked, and the mesa pattern on the first mask was transferred to the surface of the upper stress layer 5. Exposure and development were performed to obtain a positive photoresist layer 8 on the upper stress layer 5. The positive photoresist layer 8 comprises spaced and uniformly distributed square photoresist blocks, i.e., the transferred mesa pattern. See [link to relevant documentation]. Figure 4 .

[0092] Step 5.2): Reactive Ion Etching (RIE)

[0093] Using a reactive ion etching (RIE) apparatus, the upper stress layer 5, lower stress layer 4, alumina protective layer 3, and germanium sacrificial layer 2, which are not covered by the positive photoresist layer 8, are etched away, and a shallow layer is then etched downwards onto the substrate 1; see Figure 5 .

[0094] Step 5.3): Remove the liquid phase positive photoresist.

[0095] Remove the positive photoresist layer 8, retaining the upper stress layer 5, lower stress layer 4, aluminum oxide protective layer 3, and germanium sacrificial layer 2 beneath the positive photoresist layer 8, to obtain multiple unit substrates; see Figure 6 .

[0096] Step 6): Second photolithography deposition of the conductive metal layer

[0097] Step 6.1): Second application of adhesive, exposure, and development.

[0098] HMDS (hexamethylsilane) is spin-coated onto the surface of the upper stress layer 5 of the unit substrate for film formation, followed by spin-coating of liquid negative photoresist. Using an i-line contact lithography machine, a second mask is used for overlay alignment, exposure, and development to obtain the upper first liquid negative photoresist layer 9. The first liquid negative photoresist layer 9 has a second mask cutout pattern 91; and the second mask cutout pattern 91 is a Z-shape arranged side-by-side. (See...) Figure 7 .

[0099] Step 6.2): ​​Deposit a conductive metal layer

[0100] On the substrate obtained in the previous step, a 100nm copper conductive layer 6 is vacuum deposited using an electron beam evaporation apparatus; see Figure 8 .

[0101] Step 6.3): Prepare a metal substrate with a metallic pattern.

[0102] The first liquid negative photoresist layer 9 is completely removed using a photoresist remover. At this time, the metal conductive layer 6 located on the first liquid negative photoresist layer 9 is also removed, resulting in a metal substrate 61 with the pattern of the second photomask; see... Figure 9 .

[0103] Step 7): Third photolithography drilling

[0104] Step 7.1): Third coating of adhesive, exposure, development, etching

[0105] HMDS hexamethylsilane is spin-coated onto the substrate after the previous step to form a film. Liquid negative photoresist is then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate is exposed and developed using a third mask. The liquid negative photoresist above the third mask is removed, resulting in a second liquid negative photoresist layer 10. This second liquid negative photoresist layer 10 has a third mask cutout pattern 101. The third mask cutout pattern 101 consists of parallel circular patterns, with each circle corresponding to the upper horizontal position of the Z-shape on the metal substrate 61. See [link / description]. Figure 10 .

[0106] Step 7.2): ICP etching

[0107] Using an ICP (Inductively Coupled Plasma) device, the metal substrate 61, upper stress layer 5, lower stress layer 4, and alumina protective layer 3 corresponding to the bottom of the circular hole were etched away to obtain a cylindrical hole; see [link / reference]. Figure 11 .

[0108] Step 7.3): Plate the bonding metal layer and remove the adhesive.

[0109] On the substrate after the previous step, a 170nm tin metal layer is deposited as a connecting metal layer using a magnetron sputtering device. This will fill the cylindrical hole and obtain a connecting metal pillar 11 that penetrates the conductive metal layer 6, the upper stress layer 5, the lower stress layer 4 and the aluminum oxide protective layer 3.

[0110] Then, the second liquid negative photoresist layer 10 is removed using a resist remover, at which point the bonding metal layer attached to the second liquid negative photoresist layer 10 is also removed; see Figure 12 .

[0111] Step 8): Fourth photolithography to determine the etching window

[0112] HMDS hexamethylsilane was spin-coated onto the substrate obtained in the previous step to form a film. Liquid negative photoresist was then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate was exposed and developed using a fourth mask. The liquid negative photoresist above the third mask was removed, resulting in a third liquid negative photoresist layer 12. This third liquid negative photoresist layer 12 has a fourth mask cutout pattern 121. The fourth mask cutout pattern 121 is elongated and serves as an etching window. The etching window is located on one side of the third liquid negative photoresist layer 12 corresponding to the metal pillar 11. (See...) Figure 13 .

[0113] Step 9): Remove the oxide protective layer inside the etching window.

[0114] Using reactive ion etching (RIE), the metal substrate 61, upper stress layer 5, lower stress layer 4, and aluminum oxide protective layer 3 below the etching window were vertically etched downwards; see [link to RIE]. Figure 14 .

[0115] Step 10): Fabrication of a metal structure self-rolling inductor

[0116] The substrate obtained in the previous step is placed in the resist stripping solution to remove the retained third liquid negative photoresist layer 12; see Figure 15 Using dry etching, the substrate is placed in a chamber filled with xenon difluoride gas, and the germanium sacrificial layer 2 is etched through the etching window. This causes the upper stress layer 5 and the lower stress layer 4, i.e., the dual-frequency silicon nitride, to curl forward along with the metal substrate 61, resulting in a micro-nanotube-shaped self-curling inductor.

[0117] Step 11): Rapid annealing

[0118] The micro-nano tubular self-rolling inductor obtained above is placed in a tubular annealing furnace and rapidly annealed under nitrogen pressure at a temperature of 250℃-500℃ and an annealing time of 60s-120s. This will melt the connecting metal pillar 11. The melted connecting metal pillar 11 can connect the upper and lower horizontal ends of adjacent Z-shapes of the metal substrate 61, that is, connect adjacent inductor units.

[0119] Furthermore, in step 11), the connecting metal pillar 11 is tin metal with a melting point of 231.89°C. Rapid annealing will melt the connecting metal pillar 11, and the melted metal will enable the metal substrate 61 of adjacent inductor units to be connected, that is, adjacent inductor units are connected.

[0120] See Figure 20 The diagram shown is a schematic representation of the second mask in Example 1. The self-curling inductor obtained in Example 1 consists of six series-connected inductor units. The spacing between adjacent inductor units is 30 μm, and the inner diameter of one complete curl is 140 μm. (See [link to documentation]). Figure 1In this embodiment 1, the self-curling inductance is 1.10 nH, the self-resonant frequency is 18.4 GHz, and the quality factor Q is 3.12. See [link / reference]. Figure 16 , Figure 17 and Figure 18 Under the same parameters, the current flow diagrams of the self-curling inductor of the present invention and the classic unidirectional and bidirectional curling inductors are shown below. Figure 19 The simulation results of the self-curling inductor of the present invention and the classic unidirectional and bidirectional curling inductors are compared under the same parameters. The conclusion is that the inductance value of the self-curling inductor of the present invention is 25% higher than that of the classic unidirectional curling inductor and 12% higher than that of the bidirectional curling inductor.

[0121] Example 2

[0122] A method for fabricating a self-curling inductor without negative magnetic coupling effect, the specific operation steps are as follows:

[0123] The process conditions and operating steps of steps (1) to (6.1) are the same as in Example 1, wherein a 50nm germanium sacrificial layer 2, a 5nm hafnium dioxide protective layer 3, a 20nm low-frequency silicon nitride thin film 4, and a 20nm high-frequency silicon nitride thin film 5 are deposited. Step (6.2) deposits a metal conductive layer, using a mask pattern as shown in the image. Figure 21 As shown, the thickness of the deposited copper conductive layer 6 is 100 nm.

[0124] The process conditions and operating steps of steps (6.3) to (10) are the same as in Example 1, resulting in a three-unit micro / nanotube-shaped self-rolling inductor. See [link to example]. Figure 22 The self-curling inductor has an inner diameter of 100 μm for one turn, a self-curling inductance of 0.38 nH, a self-resonant frequency of 25.3 GHz, and a quality factor Q of 3.1.

[0125] Example 3

[0126] A method for fabricating a self-curling inductor without negative magnetic coupling effect, the specific operation steps are as follows:

[0127] The steps are the same as in Example 1, except that in step (6.2), a conductive metal layer is deposited, and the mask pattern used is as follows. Figure 23 As shown. A four-unit micro / nanotube self-rolling inductor was obtained; see [reference]. Figure 24The self-curling inductor has an inner diameter of 150 μm for one turn, a self-curling inductance of 0.59 nH, a self-resonant frequency of 18.58 GHz, and a quality factor Q of 2.59. It will be readily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a self-curling inductor without negative magnetic coupling effect, comprising the following steps: Step 1): Clean the substrate. The substrate (1) was cleaned and dried according to the standardized cleaning process; Step 2): Deposit a germanium sacrificial layer A germanium sacrificial layer (2) was deposited on a cleaned substrate (1) using a vacuum coating machine; Step 3): Deposit an oxide protective layer using the ALD atomic layer deposition method. An oxide protective layer (3) was deposited on the germanium sacrificial layer (2) using ALD atomic layer deposition; Step 4): Deposit dual-frequency silicon nitride Using PECVD plasma-enhanced chemical vapor deposition, a low-frequency silicon nitride thin film, i.e., the lower stress layer (4), is first deposited on the oxide protective layer (3) as a stretching layer, and then a high-frequency silicon nitride thin film, i.e., the upper stress layer (5), is deposited as a compression layer. Step 5): First photolithography step to determine the operating table surface Step 5.1): First application of adhesive, exposure, and development. HMDS hexamethylsilane was spin-coated onto the surface of the upper stress layer (5) to form a film, and then liquid phase positive photoresist was spin-coated. Using an i-line contact lithography machine, the photoresist portion that needs to be retained is blocked, and the mesa pattern on the first mask is transferred to the surface of the upper stress layer (5). After exposure and development, a positive photoresist layer (8) is obtained on the upper stress layer (5). The positive photoresist layer (8) includes spaced and uniformly distributed square photoresist blocks, i.e., the transferred mesa pattern. Step 5.2): Reactive Ion Etching (RIE) Using a reactive ion etching (RIE) apparatus, the upper stress layer (5), lower stress layer (4), oxide protection layer (3), and germanium sacrificial layer (2) not covered by the positive photoresist layer (8) are etched away, and a shallow layer is etched down onto the substrate (1). Step 5.3): Remove the liquid phase positive photoresist. Remove the positive photoresist layer (8), and retain the upper stress layer (5), lower stress layer (4), oxide protection layer (3) and germanium sacrificial layer (2) below the positive photoresist layer (8) to obtain multiple unit substrates; Step 6): Second photolithography deposition of the conductive metal layer Step 6.1): Second application of adhesive, exposure, and development. HMDS hexamethylsilane was spin-coated onto the surface of the upper stress layer (5) of the unit substrate to form a film, and then liquid negative photoresist was spin-coated. Using an i-line contact lithography machine, the second mask is used for overlay alignment, exposure, and development to obtain the upper first liquid negative photoresist layer (9), which has a second mask cutout pattern (91). Furthermore, the second mask plate's cutout pattern (91) is a Z-shape arranged side by side; Step 6.2): ​​Deposit a conductive metal layer On the substrate obtained in the previous step, a metal conductive layer is vacuum deposited using an electron beam evaporation device (6); Step 6.3): Prepare a metal substrate with a metallic pattern. The first liquid negative photoresist layer (9) is completely removed with a photoresist remover. At this time, the metal conductive layer (6) on the first liquid negative photoresist layer (9) is also removed, and a metal substrate (61) with the pattern of the second photomask is obtained. Step 7): Third photolithography drilling Step 7.1): Third coating of adhesive, exposure, development, etching HMDS hexamethylsilane was spin-coated onto the substrate after the previous step to form a film. Liquid negative photoresist was then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate was exposed and developed on the third mask. The liquid negative photoresist above the third mask was removed to obtain a second liquid negative photoresist layer (10). The second liquid negative photoresist layer (10) has a third mask cutout pattern (101). The third mask cutout pattern (101) is a circle arranged side by side, so that the circles correspond one-to-one with the horizontal upper end of the Z-shape of the metal substrate (61). Step 7.2): ICP inductively coupled plasma etching Using an ICP inductively coupled plasma device, the metal substrate (61), upper stress layer (5), lower stress layer (4) and oxide protective layer (3) corresponding to the bottom of the circle are etched away to obtain a cylindrical hole; Step 7.3): Plate the bonding metal layer and remove the adhesive. On the substrate after the previous step, a connecting metal layer is deposited using a magnetron sputtering device. This will fill the cylindrical hole and obtain a connecting metal pillar (11) that penetrates the conductive metal layer (6), the upper stress layer (5), the lower stress layer (4), and the oxide protective layer (3). Then the second liquid negative photoresist layer (10) is removed using a photoresist remover, and the bonding metal layer attached to the second liquid negative photoresist layer (10) is removed accordingly. Step 8): Fourth photolithography to determine the etching window HMDS hexamethylsilane was spin-coated onto the substrate obtained in the previous step to form a film. Liquid negative photoresist was then spin-coated onto the substrate. Using an i-line contact lithography machine, the substrate was exposed and developed using a fourth mask. The liquid negative photoresist above the fourth mask was removed to obtain a third liquid negative photoresist layer (12). The third liquid negative photoresist layer (12) has a fourth mask cutout pattern (121). The fourth mask cutout pattern (121) is elongated and serves as an etching window. The etching window is located on one side of the third liquid negative photoresist layer (12) corresponding to the metal pillar (11). Step 9): Remove the oxide protective layer inside the etching window. Using reactive ion etching (RIE), the metal substrate (61), upper stress layer (5), lower stress layer (4) and oxide protection layer (3) below the etching window are vertically etched downwards. Step 10): Fabrication of a metal structure self-rolling inductor The substrate obtained in the previous step is placed in the resist stripping solution to remove the retained third liquid negative photoresist layer (12); using dry etching or wet etching, the germanium sacrificial layer (2) is etched through the etching window, so that the upper stress layer (5) and the lower stress layer (4), i.e., the dual-frequency silicon nitride, roll forward with the metal substrate (61) to obtain a micro-nano tubular self-rolling inductor; Step 11): Rapid annealing The micro-nano tubular self-rolling inductor obtained above is placed in a tubular annealing furnace and rapidly annealed under nitrogen pressure. The annealing temperature is 250℃-500℃ and the annealing time is 60s-120s. This will melt the connecting metal pillar (11). The melted connecting metal pillar (11) can connect the upper and lower horizontal ends of the adjacent Z-shapes of the metal substrate (61), that is, connect the adjacent inductor units.

2. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 1), when the material of the substrate (1) is silicon, a silicon dioxide insulating layer needs to be grown on the silicon surface to achieve electrical isolation between layers.

3. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 2), the thickness of the germanium sacrificial layer (2) is 30-120 nm; in step 3), the thickness of the oxide protective layer (3) is 1-20 nm, and the material is aluminum oxide or hafnium dioxide; in step 4), the low-frequency silicon nitride thin film, i.e. the lower stress layer (4), serves as a stretching layer and has a thickness of 15 nm-40 nm; the high-frequency silicon nitride thin film, i.e. the upper stress layer (5), serves as a compression layer and has a thickness of 15 nm-40 nm; the thickness of the metal conductive layer (6) is 40 nm-200 nm, and the material is one of silver, gold, aluminum, copper or zinc.

4. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 10), the inner diameter of the self-curling inductor is 1-300 μm, the spacing between adjacent inductor units is 1-70 μm, and the number of curling turns is one turn.

5. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 10), when the material of the metal substrate (61) is copper, dry etching is used. Dry etching involves placing the substrate in a chamber containing xenon difluoride gas, and the xenon difluoride gas enters the etching window to etch the germanium sacrificial layer (2), thereby achieving curling.

6. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 10), when the material of the selected substrate (1) is silicon, wet etching is used; wet etching is to put the substrate into a hydrogen peroxide solution and etch the germanium sacrificial layer (2) through the etching window (7) to achieve curling.

7. The method for preparing a self-curling inductor without negative magnetic coupling effect according to claim 1, characterized in that: In step 11), the connecting metal pillar (11) is made of tin metal and has a melting point of 231.89°C. Rapid annealing will melt the connecting metal pillar (11), and the melted metal will enable the metal substrate (61) of the adjacent inductor unit to be connected, that is, the adjacent inductor units are connected.

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