Processing method of cantilever beam integrated with heating resistor and wire

Abstract

According to the processing method of the cantilever beam integrated with the heating resistor and the wire, the heating resistor and the low-resistance metal wire are integrated into the cantilever beam film, so that the problems of poor adhesion between a metal circuit and a polyimide film, easiness in cracking due to vibration and the like are solved, and meanwhile, circuit conduction between the front surface and the back surface of the ultrathin polyimide film is realized; after the cantilever beam is welded and integrated with the MEMS device, low-heat-loss structural support is provided for the MEMS device. Heating temperature control can be carried out on the MEMS device within a certain temperature range; the MEMS device can effectively resist certain vibration and impact strength within a certain temperature range; a circuit lead of the MEMS device can be communicated to other structures through a circuit in the cantilever beam film; the structure can bear a supporting structure of various semiconductor micro devices, a circuit wire, a heating resistor and other structures are integrated above the structure, and circuit conduction of the front face and the back face of the thin film can be achieved through welding flux welding.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS device structure support, and particularly to a processing method for a cantilever beam integrated with a heating resistor and a wire. Background Art

[0002] At present, some semiconductor physical devices rely on a cantilever support with a low thermal conductivity coefficient to reduce heat conduction loss and thus reduce the overall power consumption of the device. The material used for the cantilever is mainly a photosensitive polyimide photoresist that can be pattern-designed and formed by high-temperature curing. When designing a circuit pattern on the polyimide film, due to the material characteristics of polyimide, its adhesion to metal is poor. The metal evaporated directly above the film will cause phenomena such as metal cracking and separation of the solder joint metal from the film under certain stress conditions, which cannot meet the subsequent integrated packaging requirements. To solve the above problems, a processing method for a cantilever beam integrated with a heating resistor and a wire is proposed. Summary of the Invention

[0003] According to the above existing technical problems, the present invention provides a processing method for a cantilever beam integrated with a heating resistor and a wire, which is characterized by including the following steps:

[0004] a. Spin-coat a photosensitive polyimide photoresist above a silicon wafer with an oxide layer, and expose it to form a first-layer PI film pattern. Use a mixed developer to dissolve the unexposed area, and cure the photoresist in a low-oxygen atmosphere at a high temperature. The film pattern at the electrode PAD position is opened.

[0005] b. Use a negative stripping photoresist as a mask, and evaporate Ti / Pt metal with a corresponding thickness according to the required resistance value. After stripping the photoresist, a heating resistor wire is obtained.

[0006] c. Use a negative photoresist to cover the area around the wire, leaving an electroplating conduction port at intervals, and at the same time, the photoresist covers and protects the heating resistor wire. The entire wafer is sputter-deposited with a seed layer metal by magnetron sputtering.

[0007] d. Use a negative photoresist to cover the entire wafer. Through photolithography and development, remove the photoresist in the part where the wire needs to be electroplated and at the wafer edge position. Immerse the wafer in an Au electroplating solution, and thicken the wire by electroplating through the seed layer metal connected to the wire position through the wafer edge.

[0008] e. Remove the photoresist on the wafer surface, use a positive anti-corrosion photoresist to cover the electroplated and thickened wire to the isolation area without metal around it, and at the same time cover and protect the heating resistor wire. Immerse the wafer in a metal removal solution to remove the seed layer metal at the remaining positions.

[0009] f. Use a negative photosensitive polyimide photoresist to fabricate the second PI film, and use a mixed developer to dissolve the unexposed area. Both films are subjected to a secondary high-temperature curing in a low-oxygen atmosphere;

[0010] g. Use a positive etching photoresist to protect a partial area on the back of the wafer, and use a silicon etcher to etch the entire wafer from the back to the silicon oxide stop layer on the front;

[0011] h. Use a BOE mixed solution to remove the stop oxide layer on the wafer, exposing the metal electrodes at the PI film PAD positions on the back of the cantilever beam;

[0012] i. Use a dicing machine to divide the wafer to obtain finished cantilevers;

[0013] The mixed developer is a 25% concentration aqueous solution of tetramethylammonium hydroxide. The oxygen content in the low-oxygen atmosphere is less than 50 ppm. The high-temperature in step a is 400 °C, and the thickness of the first PI film after pattern curing is less than 5 microns;

[0014] The distance separated in step c is 1000 microns. The entire wafer is sputter-deposited with a Ti / Au seed layer metal by magnetron sputtering. After removing the photoresist, the entire wafer, except for the wire edge isolation area and the heating wire position, is covered with the seed layer metal and interconnected;

[0015] In step d, after immersing the wafer in the Au electroplating solution, the wire is electroplated and thickened by connecting through the seed layer metal at the edge of the wafer to the wire position;

[0016] In step f, the secondary high-temperature curing temperature is 410 °C. After curing, the total thickness of the two PI films is less than 10 microns, and the second PI film covers the metal at the electrode PAD positions of the first PI film;

[0017] The etching depth in step g is 300 microns;

[0018] In step h, the BOE mixed solution is a mixed solution of hydrofluoric acid and ammonium fluoride.

[0019] Advantages of the present invention:

[0020] The present invention integrates a heating resistor and a low-resistance metal wire into a cantilever beam thin film, solving problems such as poor adhesion between the metal circuit and the polyimide thin film and easy cracking under vibration. At the same time, it realizes the circuit conduction between the front and back sides of the ultra-thin polyimide thin film. After the cantilever beam is welded and integrated with the MEMS device, it provides a structural support with low heat loss for the MEMS device; it can heat and control the temperature of the MEMS device within a certain temperature range; it can effectively resist a certain vibration and impact intensity for the MEMS device within a certain temperature range; it can realize the connection of the circuit wires of the MEMS device to other structures through the internal circuit of the cantilever beam thin film; this structure can bear the support structure of various semiconductor micro-devices, and circuit wires, heating resistors and other structures are integrated above it, and the circuit conduction between the front and back sides of the thin film can be realized through solder welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. is a schematic structural diagram of a cantilever beam integrating a heating resistor and a wire, which is a processing method of the cantilever beam integrating a heating resistor and a wire according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. 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.

[0023] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0024] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example 1

[0026] The present invention provides a processing method for a cantilever beam integrating a heating resistor and a wire, which is characterized by including the following steps:

[0027] a. Spin-coat a photosensitive polyimide photoresist above a silicon wafer with an oxide layer, and expose it to form a first-layer PI thin film pattern. Use a mixed developer to dissolve the unexposed area. The photoresist is cured at a high temperature in a low-oxygen atmosphere, and the thin film pattern at the electrode PAD position is opened;

[0028] b. Use a negative stripping photoresist as a mask, and evaporate Ti / Pt metal with a corresponding thickness according to the required resistance value. After stripping the photoresist, a heating resistor wire is obtained;

[0029] c. Use a negative photoresist to cover the area around the wire, leaving an electroplating conduction opening at intervals. At the same time, the photoresist covers and protects the heating resistor wire. The entire wafer is sputter-deposited with a seed layer metal by magnetron sputtering;

[0030] d. Use a negative photoresist to cover the entire wafer. Through photolithography and development, remove the photoresist in the part where the wire needs to be electroplated and at the wafer edge position. Immerse the wafer in an Au electroplating solution, and thicken the wire by electroplating through the seed layer metal connected to the wire position through the wafer edge;

[0031] e. Remove the photoresist on the wafer surface. Use a positive anti-corrosion photoresist to cover the electroplated and thickened wire to the isolation area without metal around it. At the same time, cover and protect the heating resistor wire. Immerse the wafer in a metal removal solution to remove the seed layer metal at other positions;

[0032] f. Use a negative photosensitive polyimide photoresist to make a second-layer PI thin film. Use a mixed developer to dissolve the unexposed area. The two layers of thin films are simultaneously cured at a high temperature for a second time in a low-oxygen atmosphere;

[0033] g. Use a positive anti-etching photoresist to protect a partial area on the back of the wafer, and use a silicon etcher to etch the entire wafer from the back to the silicon oxide stop layer on the front;

[0034] h. Use a BOE mixed solution to remove the stop oxide layer on the wafer, exposing the metal electrode at the PI thin film PAD position on the back of the cantilever beam;

[0035] i. Use a dicing machine to divide the wafer to obtain the finished cantilever beam;

[0036] The mixed developer is an aqueous solution of 25% tetramethylammonium hydroxide. The oxygen content in the low-oxygen atmosphere is less than 50 ppm. The high temperature in step a is 400 °C. After curing, the thickness of the first layer of PI film pattern is less than 5 microns.

[0037] In step c, the separated distance is 1000 microns. The entire wafer is coated with a Ti / Au seed layer metal by magnetron sputtering. After removing the photoresist, the entire wafer, except for the wire edge isolation area and the heating wire position, is covered with the seed layer metal and interconnected.

[0038] In step d, after immersing the wafer in the Au electroplating solution, the wire is electroplated and thickened by connecting through the seed layer metal at the wafer edge to the wire position.

[0039] In step f, the secondary high-temperature curing temperature is 410 °C. After curing, the total thickness of the two layers of PI film is less than 10 microns. The second layer of PI film covers the metal at the electrode PAD position of the first layer of PI film.

[0040] In step g, the etching depth is 300 microns.

[0041] In step h, the BOE mixed solution is a mixed solution of hydrofluoric acid and ammonium fluoride.

[0042] Example 2

[0043] On top of a silicon wafer with an oxide layer, a photosensitive polyimide photoresist with a certain thickness is spin-coated. The first layer of PI film pattern is exposed using an ultraviolet exposure machine, and the unexposed area is dissolved using an aqueous solution of 25% tetramethylammonium hydroxide. The photoresist is cured at a high temperature of 400 °C in a low-oxygen atmosphere (oxygen content less than 50 ppm). After curing, the thickness is less than 5 microns, and the film pattern at the electrode PAD position is opened.

[0044] Using a negative stripping photoresist as a mask, Ti / Pt metal with a corresponding thickness is evaporated according to the required resistance value, and the heating resistance wire is obtained after stripping the photoresist.

[0045] Using a negative photoresist to cover the area around the wire, an electroplating conduction opening is left every 1000 microns. At the same time, the photoresist covers and protects the heating resistance wire. The entire wafer is coated with a Ti / Au seed layer metal by magnetron sputtering. After removing the photoresist, the entire wafer, except for the wire edge isolation area and the heating wire position, is covered with the seed layer metal and interconnected.

[0046] Cover the entire wafer with a negative photoresist. Through photolithography and development, remove the photoresist in the areas where the wires need to be electroplated and at the wafer edge positions. Immerse the wafer in an Au electroplating solution, and electroplate and thicken the wires through the seed layer metal connected to the wire positions via the wafer edge.

[0047] Remove the photoresist on the wafer surface. Use a positive anti-corrosion photoresist to cover the electroplated and thickened wires and the non-metal isolation areas around them. At the same time, cover and protect the heating resistance wire. Immerse the wafer in a metal removal solution to remove the seed layer metal in the remaining positions.

[0048] Use a negative photosensitive polyimide photoresist to fabricate the second PI film. Use a 25% concentration of tetramethylammonium hydroxide aqueous solution to dissolve the unexposed areas. Both films are secondarily cured under a low-oxygen atmosphere (oxygen content less than 50 ppm) and at a temperature approximately 10 °C higher than the first time. After curing, the total thickness of the two PI films is less than 10 microns, and the second PI film covers the metal at the electrode PAD positions of the first PI film.

[0049] Use a positive anti-etch photoresist to protect some areas on the back of the wafer. Use a silicon etcher to etch the entire wafer from the back to the silicon oxide stop layer on the front, with an etching depth of 300 microns.

[0050] Use a mixed solution of hydrofluoric acid and ammonium fluoride to remove the stop oxide layer on the wafer, exposing the metal electrodes at the PI film PAD positions on the back of the cantilever beam.

[0051] Use a dicing machine to divide the wafer to obtain the finished cantilever beams.

[0052] After the cantilever beams are welded and integrated with the MEMS device, they provide a structural support with low heat loss for the MEMS device; they can control the heating temperature of the MEMS device within a certain temperature range; they can enable the MEMS device to effectively resist a certain vibration and impact intensity within a certain temperature range; they can enable the circuit wires of the MEMS device to be connected to other structures through the internal circuit in the cantilever beam film.

[0053] The above shows and describes the basic principles, main features, and advantages of the present invention. Each component mentioned in the present invention is a common technology in the existing field. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for processing a cantilever beam with integrated heating resistor and wire, characterized in that: The following steps are involved: a. Spin-coat a photosensitive polyimide photoresist on the silicon wafer containing the oxide layer, and expose the first layer of PI film pattern. Use a mixed developer to dissolve the unexposed area. The photoresist is cured at high temperature in a low-oxygen atmosphere, and the film pattern at the electrode PAD position is opened; b. Use negative stripping photoresist as a mask, evaporate Ti / Pt metal of corresponding thickness according to the required resistance value, and obtain the heating resistance wire after stripping the photoresist; c. Use negative photoresist to cover the area around the wire, leaving electroplating holes at intervals. At the same time, the photoresist covers the protective heating resistor wire, and the entire wafer is deposited with a seed layer of metal by magnetron sputtering; d. Use negative photoresist to cover the entire wafer, remove the photoresist at the part where the conductor needs to be plated and the edge of the wafer through photolithography development, immerse the wafer in Au electroplating solution, and connect the metal at the edge of the wafer to the conductor position through the seed layer to perform electroplating thickening of the conductor; e. Remove the photoresist on the wafer surface, use positive anti-corrosion photoresist to cover the electroplated thickened wire to the metal-free isolation area around it, and cover the protective heating resistor wire at the same time, and immerse the wafer in the metal removal liquid to remove the seed layer metal in the remaining positions; f. Use negative photosensitive polyimide photoresist to make the second PI film, use mixed developer to dissolve the unexposed area, and use low-oxygen atmosphere to perform secondary high-temperature curing on the two films at the same time; g. Use positive anti-etching photoresist to protect part of the back side of the wafer, and use a silicon etcher to etch the entire wafer from the back side to the silicon oxide cut-off layer on the front side; h. Use BOE mixed solution to remove the cut-off oxide layer on the wafer to expose the metal electrode at the PI film PAD position on the back of the cantilever beam; i. Use a dicing machine to cut the wafer into pieces to obtain the finished cantilever beam.

2. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 1, characterized in that: The mixed developer is a 25% concentration of tetramethylammonium hydroxide aqueous solution, the oxygen content of the low oxygen atmosphere is less than 50 ppm, the high temperature in step a is 400° C., and the thickness of the first layer of PI film graphics after curing is less than 5 microns.

3. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 2, characterized in that: The distance separated in step c is 1000 microns. The entire wafer is deposited with Ti / Au seed layer metal by magnetron sputtering. After the photoresist is removed, the entire wafer is covered with seed layer metal except for the isolation area at the edge of the wire and the position of the heating wire, and the rest of the positions are connected to each other.

4. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 3, characterized in that: In step d, after the wafer is immersed in the Au electroplating solution, the metal of the seed layer is connected to the position of the conductor through the edge of the wafer to perform electroplating thickening of the conductor.

5. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 4, characterized in that: The secondary high-temperature curing temperature in step f is 410° C. After curing, the total thickness of the two layers of PI film is less than 10 μm, and the second layer of PI film covers the metal at the position of the electrode PAD of the first layer of PI film.

6. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 5, characterized in that: The etching depth in step g is 300 microns.

7. The method for processing a cantilever beam with integrated heating resistor and wire according to claim 6, characterized in that: In step h, the BOE mixed solution is a mixed solution of hydrofluoric acid and ammonium fluoride.

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