Sensor chip metal electrode thermal protection structure and preparation method thereof

Abstract

The invention discloses a sensor chip metal electrode thermal protection structure and a preparation method thereof, and belongs to the technical field of metal electrode thermal protection structures. The thermal protection structure comprises a sensor substrate, wherein an electrode buffer layer and a continuous multi-layer Pt-W electrode are sequentially arranged on the sensor substrate. In the structure, the Pt electrode is deposited on the W electrode, and the deposition mode enables the Pt crystal structure to be more stable. The continuous multi-layer Pt-W electrode is prepared by accurately controlling the sputtering process, and the quality of the Pt crystal can be remarkably improved, so that the Pt electrode is effectively prevented from secondary crystallization in a high-temperature environment, namely the so-called'agglomeration 'phenomenon. The thermal protection structure provided by the invention can ensure that the electrode resistance is not sharply increased in a high-temperature environment on the premise of not influencing lead bonding, so that the working reliability of the thermal resistance type sensor in the high-temperature environment is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal electrode thermal protection structures, and in particular to a sensor chip metal electrode thermal protection structure and a preparation method thereof. Background Art

[0002] With the continuous development of sensor technology, the market demand for sensor chips with excellent thermal protection performance is growing, especially in extreme working conditions such as aerospace, oil exploration, and metallurgy, which put forward higher requirements for the thermal protection capabilities of sensor chips. However, under high temperature conditions, the electrical interconnection of sensors faces severe challenges, because metal electrodes are prone to secondary crystallization at high temperatures, that is, the "agglomeration" phenomenon. The originally regularly distributed metal crystals condense into larger crystals and are dispersed, resulting in a sharp increase in electrode resistance.

[0003] At present, sensor chips usually use wire bonding to output electrical signals. Wire bonding is an early bonding process and one of the mainstream packaging technologies at this stage. It is relatively low-cost and is an economical and effective connection method. In sensor chip packaging, wire bonding can adapt to different types of components and leads of different sizes. By firmly connecting the electrodes inside the chip with the external leads, the reliable operation of the integrated circuit is ensured. However, due to its process characteristics, sensor chips adapted to the wire bonding process must have windows above the electrodes to expose the electrodes. The agglomeration of exposed metal electrodes at high temperatures poses a challenge to the use of sensors in high-temperature environments. How to achieve compatible wire bonding and stable and reliable high-temperature resistant electrodes has become a difficult point. Summary of the invention

[0004] In order to solve the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a sensor chip metal electrode thermal protection structure and a preparation method thereof, so as to solve the problem that the existing metal electrodes are prone to agglomeration at high temperatures.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a thermal protection structure for a metal electrode of a sensor chip is provided, the thermal protection structure is a layered structure, including a sensor chip substrate, an electrode buffer layer and a Pt-W electrode layer arranged in sequence.

[0006] Furthermore, the sensor chip substrate is Si wafer, Al2O 3、 SiC, SiN or ceramic materials.

[0007] Furthermore, the thickness of the electrode buffer layer is 3-8 nm.

[0008] Furthermore, the number of Pt-W electrode layers is 15-21, and the thickness of each layer is 10-15 nm.

[0009] The present invention also provides a method for preparing the above-mentioned thermal protection structure, comprising the following steps: (1) Depositing an insulating layer on the sensor chip substrate, patterning the electrode portion on its surface, etching the buried bottom electrode cavity, and then magnetron sputtering metal to obtain an electrode buffer layer; (2) magnetron sputtering Pt metal on the surface of the electrode buffer layer in step (1), and then removing the adhesive to obtain a Pt electrode layer; (3) Dry transfer of a single-layer graphene onto the Pt electrode layer to obtain a temperature-sensitive unit, and then patterning the temperature-sensitive unit; (4) Depositing a Si3N4 film on the surface of the temperature-sensitive unit to obtain a high-temperature protective layer for the temperature-sensitive unit, and then etching a window on the surface of the Pt electrode layer; (5) magnetron sputtering W metal on the surface of the Pt electrode layer in step (4) to obtain a W electrode layer, and then magnetron sputtering Pt metal on the surface of the W electrode layer to obtain a Pt-W electrode layer; (6) Repeat step (5) to obtain.

[0010] Furthermore, in step (1), the insulating layer is SiO2, the thickness is 300-350µm, and the ultrasonic time is 3-10min.

[0011] Furthermore, in step (1), the metal is Cr, Ir, Ti, Al or Ta.

[0012] Furthermore, in step (2), the thickness of the Pt electrode layer is 10-15 nm; and the negative resist is removed by soaking in acetone.

[0013] Furthermore, in step (4), the thickness of the Si3N4 film is 350-400 nm.

[0014] Furthermore, in step (5), the thickness of the W electrode layer is 10-15 nm.

[0015] The present invention has the following beneficial effects: (1) The present invention achieves a significant improvement in the quality of Pt crystals by carefully designing and adopting a Pt-W continuous multilayer electrode structure. This innovative structure effectively curbs the secondary crystallization phenomenon that is prone to occur in Pt electrodes in high-temperature environments above 800°C, the so-called "agglomeration" problem. This successfully avoids the negative impact on the high-temperature reliability of thermal resistance sensors caused by a sharp increase in electrode resistance. In the present invention, W and Pt have a high lattice matching degree, so that the Pt crystals deposited on the W substrate show excellent quality. In particular, when the W substrate and the Pt crystal are kept at a small distance, the quality improvement effect of the deposited crystal is particularly prominent. Therefore, by depositing a thin layer of Pt electrode on the W substrate, it can be ensured that the resulting crystals have high-quality characteristics.

[0016] (2) The thermal protection structure of the present invention can ensure that the electrode surface does not affect the wire bonding when it is in a bare state, effectively prevent the metal electrode layer from agglomerating at high temperatures, avoid a sudden increase in resistance, and thus ensure the stability of the electrical signal output by the sensor and improve its reliability in complex environments. By precisely controlling the number of deposition cycles and overall thickness of the continuous multi-layer Pt-W electrode, the thermal protection performance of the electrode is optimized, meeting the stringent requirements for high-temperature reliability of sensor chips in the fields of aerospace, oil exploration, metallurgy, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the overall structure of the thermal protection structure of Example 1 of the present invention; Figure 2 Schematic diagram of step (2) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 3 Schematic diagram of step (4) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 4 Schematic diagram of step (5) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 5 Schematic diagram of step (6) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 6 is a schematic diagram of step (7) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 7 is a schematic diagram of step (8) in the method for preparing a thermal protection structure according to Example 1 of the present invention; Figure 8 The resistance change diagram of the electrode sensor samples having the heat protection structure of Example 1 and the comparative example at high temperature; Fig. 9 The electron microscope images of the thermal protection structures of Example 1 of the present invention and the comparative example after being heated to 1200°C. DETAILED DESCRIPTION

[0018] The following examples are only used to explain the present invention and are not intended to limit the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0019] Embodiment 1: A thermal protection structure for a metal electrode of a sensor chip comprises: a sensor chip substrate, an electrode buffer layer, and a Pt-W continuous multilayer metal electrode layer; the electrode buffer layer is arranged on the sensor chip substrate, and a Pt-W continuous multilayer metal electrode layer is arranged on the electrode buffer layer. The overall structure is shown in FIG. Figure 1 The preparation method comprises the following steps: (1) Using 350µm thick double-polished Si wafer as substrate material; (2) Deposit a 300nm thick SiO2 insulating layer (see Figure 2 ), clean the chip substrate material, use acetone, anhydrous ethanol, and water ultrasonic for 5 minutes in sequence, and then blow dry with N2; (3) Using negative photolithography, a layer of hexamethyldisilazane was evenly sprayed on the surface of the chip to enhance the adhesion between the photoresist and the substrate. AZ4620 photoresist was evenly applied on the pretreated chip. The forward rotation speed was 600 rpm for 6 seconds to make the photoresist evenly distributed on the substrate. The backward rotation speed was 4000 rpm for 30 seconds to adjust the thickness of the photoresist. The chip with the photoresist was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist. (4) Patterning the electrode part, etching the buried bottom electrode cavity, and then magnetron sputtering 5nm thick Cr metal as the electrode buffer layer (see Figure 3 ); (5) Magnetron sputtering of 10 nm of Pt metal on the surface of the product obtained in step (4) as the electrode bottom layer (see Figure 4 ), and then remove the negative resist by soaking in acetone to obtain a Pt electrode layer; (6) Dry transfer of a single-layer graphene onto the Pt electrode layer to obtain a temperature-sensitive unit, and patterning the temperature-sensitive unit to make the electrode bare for wire bonding (see Figure 5 ); (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit of step (6) by low pressure chemical vapor deposition (LPCVD) as a high temperature protection layer for the temperature-sensitive unit, and a window is etched on the surface of the Pt electrode layer to make the Pt electrode bare for wire bonding (see Figure 6 ); (8) Magnetron sputtering of a 10 nm thick W electrode layer on the Pt electrode layer (see Figure 7 ); (9) 10 nm Pt electrode layer on the W electrode layer; (10) Repeat steps (8) and (9) until a 21×10 nm Pt-W continuous multilayer composite electrode is prepared, with the Pt electrode layer as the top layer to facilitate subsequent wire bonding.

[0020] Embodiment 2: A thermal protection structure for a metal electrode of a sensor chip comprises: a sensor chip substrate, an electrode buffer layer, and a Pt-W continuous multilayer metal electrode layer; the electrode buffer layer is arranged on the sensor chip substrate, and the Pt-W continuous multilayer metal electrode layer is arranged on the electrode buffer layer. The preparation method thereof comprises the following steps: (1) Using 300µm thick double-polished Si wafer as substrate material; (2) Deposit a 350 nm thick SiO2 insulating layer, clean the chip substrate material, and use acetone, anhydrous ethanol, and water ultrasonic treatment for 10 min in sequence, and then blow dry with N2; (3) Using negative photolithography, a layer of hexamethyldisilazane was evenly sprayed on the surface of the chip to enhance the adhesion between the photoresist and the substrate. The pretreated chip was evenly coated with AZ4620 photoresist. The forward rotation speed was 600 rpm for 10 seconds to make the photoresist evenly distributed on the substrate. The backward rotation speed was 5000 rpm for 40 seconds to adjust the thickness of the photoresist. The chip with the photoresist was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist. (4) Patterning the electrode part, etching out the buried bottom electrode cavity, and then magnetron sputtering 8nm thick Cr metal as the electrode buffer layer; (5) magnetron sputtering a 12 nm thick Pt metal as an electrode bottom layer on the surface of the product obtained in step (4), and then removing the negative resist by soaking in acetone to obtain a Pt electrode layer; (6) Dry transfer of a single-layer graphene onto the Pt electrode layer to obtain a temperature-sensitive unit, and patterning the temperature-sensitive unit to expose the electrode for wire bonding; (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit of step (6) by low pressure chemical vapor deposition (LPCVD) as a high temperature protection layer of the temperature-sensitive unit, and a window is etched on the surface of the Pt electrode layer to make the Pt electrode bare for wire bonding; (8) Magnetron sputtering a 12 nm thick W electrode intermediate layer on the Pt electrode layer; (9) 12nm Pt electrode layer on W electrode layer; (10) Repeat steps (8) and (9) until a 19×12 nm Pt-W continuous multilayer composite electrode is prepared, with the Pt electrode layer as the top layer to facilitate subsequent wire bonding.

[0021] Embodiment 3: A thermal protection structure for a metal electrode of a sensor chip comprises: a sensor chip substrate, an electrode buffer layer, and a Pt-W continuous multilayer metal electrode layer; the electrode buffer layer is arranged on the sensor chip substrate, and the Pt-W continuous multilayer metal electrode layer is arranged on the electrode buffer layer. The preparation method thereof comprises the following steps: (1) Using 330µm thick double-polished Si wafer as substrate material; (2) Deposit a 330 nm thick SiO2 insulating layer, clean the chip substrate material, and use acetone, anhydrous ethanol, and water ultrasonic treatment for 3 min in sequence, and then blow dry with N2; (3) Using negative photolithography, a layer of hexamethyldisilazane was evenly sprayed on the surface of the chip to enhance the adhesion between the photoresist and the substrate. The pretreated chip was evenly coated with AZ4620 photoresist. The forward rotation speed was 500 rpm for 5 seconds to make the photoresist evenly distributed on the substrate. The backward rotation speed was 4500 rpm for 30 seconds to adjust the thickness of the photoresist. The chip with the photoresist was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist. (4) Patterning the electrode part, etching out the buried bottom electrode cavity, and then magnetron sputtering 8nm thick Cr metal as the electrode buffer layer; (5) magnetron sputtering a 15 nm thick Pt metal as an electrode bottom layer on the surface of the product obtained in step (4), and then removing the negative resist by soaking in acetone to obtain a Pt electrode layer; (6) Dry transfer of a single-layer graphene onto the Pt electrode layer to obtain a temperature-sensitive unit, and patterning the temperature-sensitive unit to expose the electrode for wire bonding; (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit of step (6) by low pressure chemical vapor deposition (LPCVD) as a high temperature protection layer of the temperature-sensitive unit, and a window is etched on the surface of the Pt electrode layer to make the Pt electrode bare for wire bonding; (8) Magnetron sputtering a 15 nm thick W electrode intermediate layer on the Pt electrode layer; (9) 15nm Pt electrode layer on W electrode layer; (10) Repeat steps (8) and (9) until a 15×15 nm Pt-W continuous multilayer composite electrode is prepared, with the Pt electrode layer as the top layer to facilitate subsequent wire bonding.

[0022] Comparative Example: A thermal protection structure for a metal electrode of a sensor chip comprises: a sensor chip substrate, an electrode buffer layer, and a Pt metal electrode layer; the electrode buffer layer is arranged on the sensor chip substrate, and the Pt metal electrode layer is arranged on the electrode buffer layer. The preparation method thereof comprises the following steps: (1) Using 350µm thick double-polished Si wafer as substrate material; (2) Deposit a 300 nm thick SiO2 insulating layer, clean the chip substrate material, and use acetone, anhydrous ethanol, and water ultrasonic treatment for 5 min in sequence, and then blow dry with N2; (3) Using negative photolithography, a layer of hexamethyldisilazane was evenly sprayed on the surface of the chip to enhance the adhesion between the photoresist and the substrate. AZ4620 photoresist was evenly applied on the pretreated chip. The photoresist was evenly distributed on the substrate by rotating at 600 r / s for 6 seconds, and then the photoresist was evenly distributed on the substrate by rotating at 4000 r / s for 30 seconds. The photoresist thickness was adjusted. The chip with even photoresist was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist. (4) Patterning the electrode part, etching out the buried bottom electrode cavity, and then magnetron sputtering 5 nm thick Cr metal as the electrode buffer layer; (5) A 200 nm thick Pt metal is magnetron sputtered on the surface of the product obtained in step (4) as an electrode layer.

[0023] Experimental example: (1) Platinum wire bonding was performed on the electrode sensor samples with the thermal protection structure of Example 1 and the comparative example respectively, and the samples were placed in a muffle furnace for high temperature testing. When the sensor resistance was stable, a multimeter was used to record the resistance data, and a group of data was recorded every 100°C. The statistical results are as follows: Figure 8 As shown. Figure 8 It can be seen that the single Pt electrode sensor in the comparative example has a resistance surge at about 800°C, while the continuous multilayer Pt-W electrode sensor in Example 1 can effectively suppress the electrode resistance surge and maintain good stability until 1200°C. It can be seen that the use of the Pt-W continuous multilayer electrode structure of the present invention can avoid the sudden increase of electrode resistance at high temperature, thereby ensuring the stability of the electrical signal output by the sensor and improving its reliability in complex environments.

[0024] (2) The thermal protection structures of Example 1 and the comparative example were placed in a muffle furnace and heated to 1200°C for 2 hours, and the electrode surface was observed under an electron microscope. The results are as follows: Fig. 9 As shown, Fig. 9 A is the Pt-W continuous multilayer structure electrode diagram of Example 1, Fig. 9 B is a comparative single Pt metal electrode diagram. As shown in Figure 9, after being treated at 1200°C for 2 hours, the surface of the single Pt metal electrode showed agglomeration under an electron microscope, and the surface roughness of the electrode increased; while the Pt-W continuous multilayer structure electrode showed no obvious changes. It can be seen that the use of the Pt-W continuous multilayer electrode structure of the present invention has achieved a significant improvement in the quality of Pt crystals, and effectively curbed the secondary crystallization phenomenon that is easy to occur in Pt electrodes in high temperature environments above 800°C, namely the so-called "agglomeration" problem.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermal protection structure for a metal electrode of a sensor chip, characterized in that: The thermal protection structure is a layered structure, comprising a sensor chip substrate, an electrode buffer layer and a Pt-W electrode layer arranged in sequence.

2. The heat protection structure according to claim 1, characterized in that: The sensor chip substrate is a Si wafer, Al2O3, SiC, SiN or a ceramic material.

3. The heat protection structure according to claim 1, characterized in that: The thickness of the electrode buffer layer is 3-8 nm.

4. The heat protection structure according to claim 1, characterized in that: The number of layers of the Pt-W electrode layer is 15-21, and the thickness of each layer is 10-15 nm.

5. The method for preparing a heat protection structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Depositing an insulating layer on the sensor chip substrate, patterning the electrode portion on its surface, etching the buried bottom electrode cavity, and then magnetron sputtering metal to obtain an electrode buffer layer; (2) magnetron sputtering Pt metal on the surface of the electrode buffer layer in step (1), and then removing the adhesive to obtain a Pt electrode layer; (3) Dry transfer of a single-layer graphene onto the Pt electrode layer to obtain a temperature-sensitive unit, and then patterning the temperature-sensitive unit; (4) Depositing a Si3N4 film on the surface of the temperature-sensitive unit to obtain a high-temperature protective layer for the temperature-sensitive unit, and then etching a window on the surface of the Pt electrode layer; (5) magnetron sputtering W metal on the surface of the Pt electrode layer in step (4) to obtain a W electrode layer, and then magnetron sputtering Pt metal on the surface of the W electrode layer to obtain a Pt-W electrode layer; (6) Repeat step (5) to obtain.

6. The method for preparing a heat protection structure according to claim 5, characterized in that: In step (1), the insulating layer is SiO2 with a thickness of 300-350 μm, and the ultrasonic time is 3-10 min.

7. The method for preparing a heat protection structure according to claim 5, characterized in that: The metal in step (1) is Cr, Ir, Ti, Al or Ta.

8. The method for preparing a heat protection structure according to claim 5, characterized in that: The thickness of the Pt electrode layer in step (2) is 10-15 nm; the de-resisting step is to remove the negative resist by soaking in acetone.

9. The method for preparing a heat protection structure according to claim 5, characterized in that: The thickness of the Si3N4 film in step (4) is 350-400nm.

10. The method for preparing a heat protection structure according to claim 5, characterized in that: The thickness of the W electrode layer in step (5) is 10-15 nm.

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