Filter chip and processing method thereof

Abstract

The application provides a filter chip and a processing method thereof, and relates to the technical field of filters.The filter chip comprises a wafer, and the wafer is provided with a chip effective area;the wafer is provided with a scribing channel outside the chip effective area;the chip effective area is provided with a resonator and a bonding pad;the bonding pad is connected with the resonator through a metal circuit;the bonding pad is provided with a solder ball in a solder ball planting area;the solder ball and the surface of the chip effective area outside the resonator are covered with a silicon dioxide protective layer.The resonator area of the filter chip is not covered with the silicon dioxide protective layer, the flexible input and output and high-frequency conversion functions of the resonator are maintained, the influence of the silicon dioxide protective layer on the performance of the filter chip is reduced, the resonant energy efficiency of the filter is improved, and the anti-interference effect of the high-frequency filter is stronger.In addition, the half-etching cavity corresponding to the resonator on the wafer is arranged on the flux brushing solder ball steel mesh, so that the resonator is prevented from being damaged in the processing process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, in particular to a filter chip and a processing method thereof. BACKGROUND

[0002] The resonant region of the low-middle-high frequency filter is covered by the silicon dioxide protective layer, which has the advantages of helping to protect the resonator from external damage and environmental pollution, and the disadvantages of having certain influence on the performance of the filter, and the protective layer has greater influence on the performance of the high frequency filter compared with the middle-low frequency filter.

[0003] In the traditional Bumping processing process, the soldering flux brush glue ball steel mesh is attached to the surface of the filter wafer, and when the brush glue and the ball implantation are pressed, foreign matter or scratches on the two steel meshes are easy to cause damage to the resonator in the chip. When the resonator region is not covered by the silicon dioxide protective layer, the resonator is easily damaged. SUMMARY

[0004] The present application aims to provide a filter chip and a processing method thereof to solve the above technical problems.

[0005] A filter chip, comprising a wafer, characterized in that the wafer is provided with a chip effective area; a scribing channel is arranged outside the chip effective area; a resonator and a pad are arranged in the effective area of the chip; the pad is connected to the resonator through a metal line; a solder ball is implanted in the ball implantation area of the pad; and a silicon dioxide protective layer is arranged on the surface of the effective area of the chip outside the solder ball and the resonator.

[0006] A processing method of a filter chip, comprising the following steps:

[0007] Step 1: designing and processing the wafer of the filter; processing the scribing channel on the wafer; installing the resonator, the metal line and the pad in the effective area of the chip; and covering the silicon dioxide protective layer on the ball implantation area of the pad and the surface of the effective area of the chip outside the resonator;

[0008] Step 2: implanting the solder ball on the pad by the Bumping processing method; the Bumping processing method comprises the following steps:

[0009] Step 2.1: removing contaminants and activating micro-etching; using weak acid medicine to remove contaminants on the surface of the wafer; preferably, the temperature of the tank body is 60° when the weak acid medicine removes contaminants and activates micro-etching.

[0010] Step 2.2: pattern protection; coating anti-gold plating photoresist, pressing the photoresist mask plate on the dry film after drying, and developing to remove the photoresist in the ball implantation area of the pad after exposure;

[0011] Step 2.3: Nickel plating; chemical deposition of a nickel layer and a gold layer on the ball mount area of the pad; preferably, the thickness of the nickel layer is 2-5 microns; the thickness of the gold layer is 0.05 microns.

[0012] Step 2.4: dry film removal; the exposed photoresist dry film is etched clean by removing the resist developer;

[0013] Step 2.5: flux brushing; the flux-coated ball mounting steel mesh is aligned and attached above the wafer, and the flux is printed on the pad position of the wafer;

[0014] Step 2.6: ball mounting; the solder balls are adhered to the surface of each pad through the flux;

[0015] Step 2.7: reflow soldering; the wafer with the solder balls is put into a reflow furnace for soldering; the reflow soldering is first raised from room temperature to 260°C, and then cooled to room temperature;

[0016] Step 2.8: the bumping process is completed after the appearance inspection is qualified.

[0017] Further, the wafer incoming material needs to be inspected before the cleaning and activation micro-etching, including checking the wafer incoming material information, confirming the traceability; inspecting the appearance of the incoming material wafer, confirming whether the wafer is damaged and the surface is contaminated, etc.

[0018] Further, the brush-coated ball mounting steel mesh is aligned and attached to the wafer in the following manner; the wafer is provided with an alignment cursor; the brush-coated ball mounting steel mesh is provided with an alignment search box corresponding to the alignment cursor; the alignment search box is two 450x450μm square windows symmetrically arranged on the brush-coated ball mounting steel mesh; when the wafer is 4 inches, the alignment search box is arranged within a radius of 80-100μm from the center of the brush-coated ball mounting steel mesh; when the wafer is 6 inches, the alignment search box is arranged within a radius of 100-150μm from the center of the brush-coated ball mounting steel mesh.

[0019] Further, in order to prevent damage to the resonator during the brushing of the flux and the ball mounting, a half-etching cavity corresponding to the resonator on the wafer is provided on the brush-coated ball mounting steel mesh; when the brush-coated ball mounting steel mesh is aligned and attached above the wafer, the resonator is located in the half-etching cavity, and the resonator and the brush-coated ball mounting steel mesh are in a non-contact state.

[0020] Preferably, the half-etching cavity of the brush-coated ball mounting steel mesh is overall an isosceles trapezoid; the included angle between the base and the waist is 75°; the thickness of the brush-coated ball mounting steel mesh is 80μm; the vertical distance between the half-etching cavity of the brush-coated ball mounting steel mesh and the resonator is 40μm; and the horizontal distance between the half-etching cavity of the brush-coated ball mounting steel mesh and the side of the resonator is 50μm.

[0021] Advantages

[0022] The resonator region of the filter chip of the present application is not covered by a silicon dioxide protective layer, keeping the resonator flexible input and output and high frequency conversion functions; the influence of the silicon dioxide protective layer on the performance of the filter chip is reduced, the resonant energy efficiency of the filter is improved, and the anti-interference effect of the high frequency filter is stronger. Since there is no silicon dioxide protective layer, when brushing flux and ball planting, the brushing glue ball planting steel mesh will be attached to the surface of the filter wafer. If there are foreign matters or scratches on the steel mesh, the resonator in the chip is easy to be damaged. The present application sets a half-etching cavity corresponding to the resonator on the brushing glue ball planting steel mesh, which avoids damage to the resonator during processing. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 The present application is a schematic diagram of the planar structure of the filter wafer.

[0024] Fig. 2 The present application is a schematic diagram of the structure of the chip region of the filter wafer.

[0025] Fig. 3 The present application is a schematic diagram of the planar structure of the brushing glue ball planting steel mesh.

[0026] Fig. 4 The present application is a schematic diagram of the structure of the brushing glue ball planting steel mesh corresponding to the wafer chip region.

[0027] Fig. 5 The present application is a schematic diagram of the state of the brushing glue ball planting steel mesh and the wafer.

[0028] Fig. 6 The present application is a schematic diagram of the wafer structure after bumping ball planting. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should be understood as the usual meaning understood by those skilled in the art. The words such as "include" and similar words used herein mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, without excluding other elements or objects.

[0030] In view of the problems in the prior art, the embodiments of the present application provide a filter chip and a processing method thereof.

[0031] Embodiment 1

[0032] As shown in Figs. 1-2 , a filter chip includes a wafer, and a chip active area is arranged on the wafer; a scribe lane 1 is arranged outside the chip active area; a resonator 2 and a pad 3 are arranged in the chip active area; the pad 3 is connected to the resonator 2 through a metal line 4; a solder ball 5 is arranged in a ball mounting area of the pad 3; and a silicon dioxide protective layer 6 is arranged on the surface of the chip active area outside the resonator 2 and the solder ball 5.

[0033] Embodiment 2

[0034] A processing method of a filter chip includes the following steps:

[0035] Step 1: design and process a wafer of a filter; the wafer structure is as shown in Figs. 1-2 ; determine an alignment coordinate 7; process a scribe lane on the wafer; install a resonator, a metal line and a pad in the chip active area; and cover a silicon dioxide protective layer on the surface of the chip active area outside the resonator and the ball mounting area of the pad;

[0036] Step 2: implant a solder ball 5 on the pad 3 through a bumping processing method.

[0037] Before the bumping processing, a photoresist mask plate and a glue brushing and ball mounting steel mesh need to be designed.

[0038] (1) design and process a photoresist mask plate: open a window in the position corresponding to the ball mounting area of the pad on the photoresist mask plate;

[0039] (2) design and process a glue brushing and ball mounting steel mesh 8, as shown in Figs. 3-5 ; the glue brushing and ball mounting steel mesh 8 is provided with an opening 9 corresponding to the ball mounting area of the pad 3; the opening 9 is used for brushing glue and mounting balls; the bottom of the glue brushing and ball mounting steel mesh 8 is provided with a half-etching cavity 10 corresponding to the position of the resonator 2; and the glue brushing and ball mounting steel mesh 8 is provided with an alignment search frame 11 corresponding to the alignment cursor on the wafer;

[0040] The alignment search frame 11 is a 450*450 μm square window symmetrically arranged on the glue brushing and ball mounting steel mesh 8, so that the glue brushing and ball mounting steel mesh 8 is accurately and effectively attached to the wafer. Corresponding to a 4-inch wafer; two alignment search frames 11 are located within a center radius of 80-100 μm of the glue brushing and ball mounting steel mesh 8; corresponding to a 6-inch wafer; two alignment search frames 11 are located within a center radius of 100-150 μm of the glue brushing and ball mounting steel mesh 8.

[0041] The brush glue ball planting steel mesh 8 is attached to the wafer and needs to be supported by the support ring 12 arranged outside the wafer; the support ring and the wafer are provided with a patch film 13 below; the half-etching cavity of the brush glue ball planting steel mesh 8 is overall an isosceles trapezoid; the included angle between the bottom surface and the waist is 75°; the thickness of the brush glue ball planting steel mesh 8 is 80 μm, and the spacing of the half-etching cavity 10 of the brush glue ball planting steel mesh 8 in the vertical direction is 40 μm compared with the resonator, and the spacing of each side of the brush glue ball planting steel mesh 8 in the horizontal direction is 50 μm compared with the resonator 2.

[0042] The diameter of the opening 9 is 90±5 μm; the tin ball of 80 μm can be leaked in; the brush glue ball planting steel mesh 8 and the wafer keep contact in the scribing channel area, and effective support and attachment are provided; the radius of the support ring 12 is 2 mm larger than that of the wafer; the wafer is 4 inches or 6 inches.

[0043] More specifically, the bumping processing method comprises:

[0044] Step 2.1. Activating and etching; using weak acid medicine in a 60-degree tank to activate and remove surface contamination;

[0045] Step 2.2. Pattern protection; after the wafer is activated, it is placed on the platform of the yellow light room equipment, and the anti-gold plating photoresist is coated. After drying, the photoresist mask plate is pressed on the dry film, and after exposure, the photoresist in the ball planting area is developed and removed; the ball planting area on the pad is exposed, and the other areas are protected by dry photoresist film;

[0046] Step 2.3. Electroplating nickel gold; the wafer after pattern protection is placed in the electroplating equipment line in the non-yellow light room, and a 2-5 μm nickel layer and a 0.05 μm gold layer are chemically deposited on the ball planting area of the pad.

[0047] Step 2.4. Dry film removal; the exposed photoresist dry film is etched clean by removing the photoresist, and at this time, only a 2-5 μm nickel layer and a 0.05 μm gold layer are left on the pad area on the wafer surface.

[0048] Step 2.5. Brushing flux; after electroplating, the wafer is placed in the ball planting equipment, the brush glue ball planting steel mesh is attached to the wafer by aligning the search frame and the alignment cursor on the wafer; the flux is printed on the pad with a squeegee;

[0049] Step 2.6. Ball planting; the tin ball is adhered to the surface of each pad through the flux;

[0050] Step 2.7. Reflow soldering; the wafer with tin balls is put into the reflow furnace, and after passing through the reflow equipment of once normal temperature to 269 degree peak and then to normal temperature, the soldering is completed, and the tin ball and the pad are effectively combined in the form of tin-aluminum alloy;

[0051] Step 2.8. Appearance inspection

[0052] The wafer is placed on an appearance confirmation platform, tin ball height is confirmed, and wafer appearance is checked, and after abnormal products are screened out, wafer tin ball bumping processing is completed.

[0053] Before activating micro-etching, the wafer incoming material needs to be inspected, including checking wafer incoming material information, confirming traceability, checking incoming wafer appearance, confirming whether the wafer is damaged and surface contamination and the like.

[0054] The application provides a filter chip without a silicon dioxide protective layer for a resonator, reduces the influence of the silicon dioxide protective layer on the performance of the filter, especially the influence on the performance of a high-frequency filter. In addition, a processing method for processing the filter chip is provided. In order to solve the technical problem that the resonator area is damaged due to the absence of the silicon dioxide protective layer in the processing process, the glue brushing and ball planting steel mesh used in the processing method is improved accordingly, and a semi-etching cavity is newly added to the glue brushing and ball planting steel mesh to prevent the resonator area from being damaged.

[0055] Although the embodiments of the application have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to the embodiments. However, it should be understood that such modifications and changes are within the scope and spirit of the application described in the claims. Moreover, the application described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. A filter chip, comprising a wafer, characterized in that: A chip active area is provided on the wafer; a dicing lane is provided outside the chip active area; a resonator and a solder pad are provided within the chip active area; the resonator area of ​​the chip is not covered with a silicon dioxide protective layer; the solder pad is connected to the resonator through a metal line; a solder ball is planted in the ball planting area of ​​the solder pad; and the surface of the chip active area other than the solder ball and the resonator is covered with a silicon dioxide protective layer.

2. A method for processing a filter chip according to claim 1; characterized in that: The processing method comprises the following steps: Step 1: Design and process the filter wafer; create scribe lines on the wafer; install the resonator, metal traces, and pads within the active chip area; and cover the pad bumping area and the active chip surface outside the resonator with a protective layer of silicon dioxide. Step 2: Implant solder balls on the pads using a bumping process. The bumping process includes the following steps: Step 2.1: Decontamination and activation micro-etching: Use weak acid solution to remove contaminants on the wafer surface; Step 2.2: Pattern protection: Apply anti-gold plating photoresist, dry it, and then press the photoresist mask on the colloid dry film. After exposure, develop and remove the photoresist in the pad bump area. Step 2.3: Electroless nickel-gold plating; chemically depositing a stack of nickel and gold layers in the ball-planting area of ​​the pad; Step 2.4: Remove the dry film; use a degumming solution to etch away the exposed photoresist dry film; Step 2.5: Apply flux; align the ball-planting stencil with the glue applied to the top of the wafer, and print flux on the pads of the wafer; Step 2.6: Ball planting: Use flux to bond solder balls to each pad surface; Step 2.7: Reflow soldering: The wafer with solder balls enters the reflow oven for soldering. Step 2.8: Bumping process is completed after the appearance inspection is passed.

3. The method for processing a filter chip according to claim 2, wherein: Before decontamination and activation micro-etching, the incoming wafers need to be inspected, including verifying the incoming wafer information and confirming traceability; inspecting the appearance of the incoming wafers to confirm whether the wafers are damaged and have surface contamination.

4. The method for processing a filter chip according to claim 2, wherein: The temperature of the tank body is 60° when the weak acid solution is used for decontamination and activation micro-etching.

5. The method for processing a filter chip according to claim 2, wherein: The thickness of the nickel material layer is 2 to 5 microns; the thickness of the gold material layer is 0.05 microns.

6. The method for processing a filter chip according to claim 2, wherein: The wafer is provided with an alignment cursor; and the glue-brushing ball-planting steel net is provided with an alignment search box corresponding to the alignment cursor.

7. The method for processing a filter chip according to claim 6, wherein: The alignment search box is two 450×450μm square windows symmetrically set on the glue-brush ball planting steel mesh. When the wafer is 4 inches, the alignment search box is set within a radius of 80~100μm from the center of the glue-brush ball planting steel mesh; when the wafer is 6 inches; the alignment search box is set within a radius of 100~150μm from the center of the glue-brush ball planting steel mesh.

8. The method for processing a filter chip according to claim 2, wherein: A semi-etched cavity corresponding to the resonator on the wafer is provided on the glue-brush ball-planting steel mesh; when the glue-brush ball-planting steel mesh is aligned and attached to the top of the wafer, the resonator is located in the semi-etched cavity, and the resonator and the glue-brush ball-planting steel mesh are in a non-contact state.

9. The method for processing a filter chip according to claim 2, wherein: During reflow soldering, the temperature is first raised from room temperature to 260°C, and then cooled back to room temperature.

10. The method for processing a filter chip according to claim 8, wherein: The half-etched cavity of the brushed glue ball planting steel mesh is an isosceles trapezoid as a whole; the angle between the bottom and the waist is 75°; the thickness of the brushed glue ball planting steel mesh is 80μm, and the spacing between the half-etched cavity of the brushed glue ball planting steel mesh and the resonator in the vertical direction is 40μm, and there is a spacing of 50μm on each side of the resonator in the horizontal direction.

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