A preparation method of a radio frequency thin film capacitor

Abstract

The present invention discloses a preparation method of a radio frequency thin film capacitor, relating to the technical field of capacitors. The method includes: preparing a layer of photoresist on a substrate, and sequentially performing exposure and development operations on the photoresist to obtain a first mask structure; sputtering a layer of gold layer on the first mask structure to obtain a bottom electrode mask structure; depositing a layer of thin film dielectric layer on the bottom electrode mask structure to obtain a dielectric layer mask structure; sputtering a layer of gold layer on the dielectric layer mask structure to obtain a top electrode mask structure; preparing a layer of photoresist on the top electrode mask structure, and sequentially performing exposure and development operations on the photoresist prepared on the top electrode mask structure to obtain a second mask structure; sequentially performing etching, scribing and photoresist removal operations on the second mask structure to obtain a radio frequency thin film capacitor. The present invention can minimize the insertion loss introduced due to the sample size and improve the operating frequency of the capacitor.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and particularly to a preparation method of a radio frequency thin film capacitor. Background Art

[0002] For the current surface mount technology of multi-layer ceramic capacitors (MLCCs), the normal usage mode is as Figure 1 shown. They are connected to the chip through external metal strip lines. In this way, the leads generate a large parasitic inductance, which limits their actual operating frequency range, generally below 1 GHz. If the traces on the circuit board during installation are taken into account, their operating frequency is only a few hundred MHz. To solve the problem of using capacitors at higher frequencies, single-layer ceramic capacitors (SLCCs) have emerged.

[0003] The structure of SLCC is: metal electrode - ceramic dielectric - metal electrode. The entire capacitor functions with the ceramic dielectric layer in the middle. It has a certain thickness (ceramics are composed of grains, that is, the thickness of the ceramic cannot be less than the size of the grains. Generally, it is very good if the thickness of the ceramic can be controlled at 0.1 mm, otherwise internal defects, voids, and cracks will occur) and must have a certain mechanical strength to function as a capacitor. The assembly method of SLCC is a micro-assembly process of wire bonding. It can be directly installed next to the chip and then encapsulated, leaving the SLC inside the encapsulated chip. This greatly shortens the length of the leads, has a small parasitic inductance, and can achieve a high operating frequency. Although this method shortens the connection distance and achieves an operating frequency of 40 GHz +, SLCC uses a ceramic dielectric with a thickness still in the range of 0.1 - 0.2 mm. During the assembly process, impedance mismatch will still be caused due to the excessive thickness of the product, resulting in low insertion loss and limiting the operating frequency of the capacitor.

[0004] Currently, the mainstream application frequency band of SLCC is from 3 GHz to dozens of GHz. With the development of microwave communication technology, future signal frequencies may develop to 100 GHz +, posing higher requirements for the operating frequency of SLCC. It is required that SLCC has excellent transmission impedance matching in the circuit to achieve ultra-low insertion loss. Therefore, it has become crucial to improve the operating frequency of SLCC by thinning the capacitor product (thickness 0.1 mm), designing a structure with a smaller introduced series equivalent inductance (ESL), and lower dielectric loss.

[0005] Ceramics are brittle materials and are prone to breakage or cracking during the thinning process. It is very difficult to achieve a thickness below 0.1 mm. At higher usage frequencies, SLCC is restricted. Therefore, it is necessary to design a new capacitor to increase the usage frequency of the capacitor. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method for a radio frequency thin film capacitor, which can minimize the insertion loss introduced by the sample size and increase the usage frequency of the capacitor.

[0007] To achieve the above object, the present invention provides the following solution:

[0008] A preparation method for a radio frequency thin film capacitor, comprising:

[0009] Preparing a layer of photoresist on a substrate, and sequentially performing exposure and development operations on the photoresist to obtain a first mask structure;

[0010] Sputtering a layer of gold layer on the first mask structure to obtain a bottom electrode mask structure, and the gold layer sputtered on the first mask structure is the bottom electrode of the radio frequency thin film capacitor;

[0011] Depositing a thin film dielectric layer on the bottom electrode mask structure to obtain a dielectric layer mask structure, and the thin film dielectric layer deposited on the bottom electrode mask structure is the dielectric layer of the radio frequency thin film capacitor;

[0012] Sputtering a layer of gold layer on the dielectric layer mask structure to obtain a top electrode mask structure, and the gold layer deposited on the dielectric layer mask structure is the top electrode of the radio frequency thin film capacitor;

[0013] Preparing a layer of photoresist on the top electrode mask structure, and sequentially performing exposure and development operations on the photoresist prepared on the top electrode mask structure to obtain a second mask structure;

[0014] Sequentially performing etching, scribing and photoresist removal operations on the second mask structure to obtain a radio frequency thin film capacitor.

[0015] Optionally, the step of sequentially performing etching, scribing and photoresist removal operations on the second mask structure to obtain a radio frequency thin film capacitor specifically includes:

[0016] Sequentially etching the top electrode, dielectric layer and bottom electrode in the second mask structure along a preset channel to obtain an etched second mask structure;

[0017] Scribing the etched second mask structure along the preset channel to obtain a plurality of capacitors;

[0018] Soaking each capacitor in acetone to wash away the photoresist;

[0019] The capacitor with the photoresist cleaned off is placed in an oven for heat baking to obtain a radio frequency thin film capacitor.

[0020] Optionally, the step of sequentially etching the top electrode, dielectric layer, and bottom electrode in the second mask structure along a preset channel to obtain the etched second mask structure specifically includes:

[0021] Wet etching is used to etch the top electrode in the second mask structure along the preset channel to obtain a top electrode etching structure;

[0022] ICP etching is used to etch the dielectric layer in the top electrode etching structure along the preset channel to obtain a dielectric layer etching structure;

[0023] Wet etching is used to etch the bottom electrode in the dielectric layer etching structure along the preset channel to obtain the etched second mask structure.

[0024] Optionally, the step of placing the capacitor with the photoresist cleaned off in an oven for heat baking to obtain a radio frequency thin film capacitor specifically includes:

[0025] The capacitor in the acetone solution is taken out with a vacuum suction pen and placed in an oven for heat baking to obtain a radio frequency thin film capacitor.

[0026] Optionally, the substrate is alumina, aluminum nitride, or a wafer.

[0027] Optionally, the thickness of the photoresist is greater than 3 μm and less than 5 μm.

[0028] Optionally, the thickness of the gold layer is greater than 4 μm and less than 6 μm.

[0029] Optionally, the thickness of the thin film dielectric layer is greater than 200 nm and less than 300 nm.

[0030] Optionally, the material of the thin film dielectric layer is silicon oxide, alumina, zirconia, or silicon nitride.

[0031] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: The present invention adopts a thin film process to greatly reduce the thickness of the capacitor, reduce the insertion loss, and increase the operating frequency of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0033] Figure 1 Schematic diagram of the usage mode of an existing multi-layer ceramic chip capacitor;

[0034] Figure 2 Flow chart of a preparation method of a radio frequency thin film capacitor provided by the present invention;

[0035] Figure 3 Structural schematic diagram of the radio frequency thin film capacitor provided by the present invention. Specific embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0038] As Figure 2 shown, the present invention provides a preparation method of a radio frequency thin film capacitor, including:

[0039] Step 101: Prepare a layer of photoresist on the substrate, and perform exposure and development operations on the photoresist in sequence to obtain a first mask structure.

[0040] Step 102: Sputter a layer of gold layer on the first mask structure to obtain a bottom electrode mask structure, and the gold layer sputtered on the first mask structure is the bottom electrode 3 of the radio frequency thin film capacitor.

[0041] Step 103: Deposit a thin film dielectric layer on the bottom electrode mask structure to obtain a dielectric layer mask structure, and the thin film dielectric layer deposited on the bottom electrode mask structure is the dielectric layer 2 of the radio frequency thin film capacitor.

[0042] Step 104: Sputter a layer of gold layer on the dielectric layer mask structure to obtain a top electrode mask structure, and the gold layer deposited on the dielectric layer mask structure is the top electrode 1 of the radio frequency thin film capacitor.

[0043] Step 105: Prepare a layer of photoresist on the top electrode mask structure, and perform exposure and development operations on the photoresist prepared on the top electrode mask structure in sequence to obtain a second mask structure.

[0044] Step 106: Perform etching, scribing, and photoresist removal operations on the second mask structure in sequence to obtain the radio frequency thin film capacitor.

[0045] In practical applications, the operations of etching, scribing, and removing photoresist from the second mask structure in sequence to obtain a radio frequency thin film capacitor specifically include:

[0046] Etch the top electrode 1, dielectric layer 2, and bottom electrode 3 in the second mask structure along a preset channel in sequence to obtain an etched second mask structure.

[0047] Scribe the etched second mask structure along the preset channel to obtain a plurality of capacitors, and a plurality of discrete capacitors are formed on the entire substrate.

[0048] Immerse each of the capacitors in acetone to wash away the photoresist, and the capacitors are separated from the substrate.

[0049] Place the capacitors with the photoresist washed away in an oven for heat baking to obtain a radio frequency thin film capacitor.

[0050] In practical applications, the operation of etching the top electrode 1, dielectric layer 2, and bottom electrode 3 in the second mask structure along a preset channel in sequence to obtain an etched second mask structure specifically includes:

[0051] Use wet etching to etch the top electrode 1 in the second mask structure along the preset channel to obtain a top electrode etched structure.

[0052] Use ICP etching to etch the dielectric layer 2 in the top electrode etched structure along the preset channel to obtain a dielectric layer etched structure.

[0053] Use wet etching to etch the bottom electrode 3 in the dielectric layer etched structure along the preset channel to obtain an etched second mask structure.

[0054] In practical applications, the operation of placing the capacitors with the photoresist washed away in an oven for heat baking to obtain a radio frequency thin film capacitor specifically includes:

[0055] Use a vacuum suction pen to take out the capacitors in the acetone solution and place them in an oven for heat baking to obtain a radio frequency thin film capacitor. As Figure 3 shown, specifically, use a vacuum suction pen to take out the capacitors in the solution and place them in an oven at 120 °C for heat baking for 30 minutes to obtain the desired capacitors (length × width × height = 0.1 mm × 0.1 mm × (0.2 - 0.3 μm)).

[0056] In practical applications, the substrate is alumina, aluminum nitride, or a wafer.

[0057] In practical applications, the thickness of the photoresist is greater than 3 μm and less than 5 μm.

[0058] In practical applications, the thickness of the gold layer is greater than 4 μm and less than 6 μm.

[0059] In practical applications, the thickness of the thin film dielectric layer is greater than 200 nm and less than 300 nm.

[0060] In practical applications, the material of the thin film dielectric layer is silicon oxide, aluminum oxide, zirconium oxide or silicon nitride. In practical applications, preparing a layer of photoresist on the substrate specifically means using a spin coater to prepare a layer of photoresist on the substrate.

[0061] In practical applications, the operations of exposing and developing the photoresist in sequence specifically are:

[0062] Through a hard mask, using an exposure machine to expose the photoresist, and developing the exposed photoresist to obtain a first photoresist pattern after exposure.

[0063] In practical applications, sputtering a layer of gold on the first mask structure to obtain a bottom electrode mask structure specifically means: sputtering a layer of gold on the photoresist by means of magnetron sputtering.

[0064] In practical applications, depositing a thin film dielectric layer on the bottom electrode mask structure to obtain a dielectric layer mask structure specifically includes: in-situ depositing a thin film dielectric layer on the bottom electrode by means of magnetron sputtering.

[0065] In practical applications, sputtering a layer of gold on the dielectric layer mask structure to obtain a top electrode mask structure specifically includes: sputtering a layer of gold on the dielectric layer by means of magnetron sputtering.

[0066] In practical applications, preparing a layer of photoresist on the top electrode mask structure, and performing the operations of exposing and developing the photoresist prepared on the top electrode mask structure in sequence to obtain a second mask structure specifically means: using a spin coater to prepare a layer of photoresist on the gold layer, through a hard mask, using an exposure machine to expose the photoresist, and developing the exposed photoresist to obtain a second photoresist pattern after exposure.

[0067] The present invention has the following technical effects:

[0068] 1. The capacitor has the characteristics of low parasitic inductance, high impedance matching degree and high operating frequency. The operating frequency can reach 100 GHz +, meeting the use of capacitors at high frequencies.

[0069] 2. Adopting a thin film process can greatly reduce the thickness of the capacitor. The dielectric layer can be controlled at the nanometer level, improving the impedance matching of the product after installation and greatly reducing the insertion loss.

[0070] 3. It can be used as a discrete capacitor, avoiding the use of an integrated method, reducing costs, being highly practical, matching with radio frequency circuits, having high compatibility, and enabling discrete capacitors in high-frequency circuits to meet the high operating frequency requirements of the circuit.

[0071] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0072] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a radio frequency thin film capacitor, characterized in that, Including: Prepare a layer of photoresist on a substrate, and sequentially perform exposure and development operations on the photoresist to obtain a first mask structure; Specifically: Through a hard mask, use an exposure machine to expose the photoresist, and develop the exposed photoresist to obtain a first photoresist pattern after exposure; Sputter a layer of gold layer on the first mask structure to obtain a bottom electrode mask structure, and the gold layer sputtered on the first mask structure is the bottom electrode of the RF thin film capacitor; Deposit a thin film dielectric layer on the bottom electrode mask structure to obtain a dielectric layer mask structure, and the thin film dielectric layer deposited on the bottom electrode mask structure is the dielectric layer of the RF thin film capacitor; Sputter a layer of gold layer on the dielectric layer mask structure to obtain a top electrode mask structure, and the gold layer deposited on the dielectric layer mask structure is the top electrode of the RF thin film capacitor; Prepare a layer of photoresist on the top electrode mask structure, and sequentially perform exposure and development operations on the photoresist prepared on the top electrode mask structure to obtain a second mask structure; Perform etching, dicing, and photoresist removal operations on the second mask structure in sequence to obtain an RF thin film capacitor. Specifically: Etch the top electrode, dielectric layer, and bottom electrode in the second mask structure along a preset channel in sequence to obtain the second mask structure after etching; Dice the second mask structure after etching along the preset channel to obtain a plurality of capacitors; Soak each of the capacitors in acetone to wash off the photoresist; Put the capacitors with the photoresist washed off into an oven for heat baking to obtain an RF thin film capacitor.

2. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The step of etching the top electrode, dielectric layer, and bottom electrode in the second mask structure along a preset channel in sequence to obtain the second mask structure after etching specifically includes: Use wet etching to etch the top electrode in the second mask structure along the preset channel to obtain a top electrode etching structure; Use ICP etching method to etch the dielectric layer in the top electrode etching structure along the preset channel to obtain a dielectric layer etching structure; Use wet etching to etch the bottom electrode in the dielectric layer etching structure along the preset channel to obtain the second mask structure after etching.

3. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The step of putting the capacitors with the photoresist washed off into an oven for heat baking to obtain an RF thin film capacitor specifically includes: Use a vacuum suction pen to take out the capacitors in the acetone solution and put them into an oven for heat baking to obtain an RF thin film capacitor.

4. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The substrate is alumina, aluminum nitride, or a wafer.

5. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The thickness of the photoresist is greater than 3μm and less than 5μm.

6. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The thickness of the gold layer is greater than 4um and less than 6um.

7. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The thickness of the thin film dielectric layer is greater than 200nm and less than 300nm.

8. The method for preparing a radio frequency thin film capacitor according to claim 1, characterized in that, The material of the thin film dielectric layer is silicon oxide, aluminum oxide, zirconium oxide, or silicon nitride.

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