A sensor chip metal electrode thermal protection structure and preparation method thereof

Abstract

The present invention discloses a sensor chip metal electrode thermal protection structure and a preparation method thereof, which belongs to the technical field of metal electrode thermal protection structures. The thermal protection structure of the present invention comprises: a sensor substrate, on which an electrode buffer layer and a continuous multi-layer Pt-W electrode are sequentially arranged. In this structure, the Pt electrode is deposited on the W electrode, and this deposition method makes the Pt crystal structure more stable. The present invention can significantly improve the quality of Pt crystals by preparing continuous multi-layer Pt-W electrodes through precise control of the sputtering process, thereby effectively avoiding the secondary crystallization of the Pt electrode in a high-temperature environment, the so-called "agglomeration" phenomenon. The thermal protection structure of the present invention can ensure that the electrode resistance does not increase sharply in a high-temperature environment without affecting the wire bonding, thereby improving the reliability of the thermal resistance sensor working in a high-temperature environment.

Description

Technical Field

[0001] The present 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. This is especially true in extreme operating conditions such as aerospace, oil exploration, and metallurgy, which place higher demands on the thermal protection capabilities of sensor chips. However, high-temperature conditions pose a severe challenge to the electrical interconnection of sensors. Metal electrodes are prone to secondary crystallization, or "agglomeration," at high temperatures. This causes the originally regularly distributed metal crystals to condense into larger and more dispersed crystals, 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 earlier 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, it ensures the reliable operation of the integrated circuit. However, due to its process characteristics, sensor chips adapted to the wire bonding process must have windows opened 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 compatibility with 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, the purpose 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, comprising 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 20-30 nm.

[0009] The present invention also provides a method for preparing the above-mentioned thermal protection structure, comprising the following steps:

[0010] (1) Deposit an insulating layer on the sensor chip substrate, then pattern the electrode portion on its surface, etch out the buried bottom electrode cavity, and then magnetron sputter metal to produce the electrode buffer layer;

[0011] (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;

[0012] (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;

[0013] (4) Depositing a Si3N4 thin film on the surface of the temperature-sensitive unit to obtain a high-temperature protective layer for the temperature-sensitive unit, and then etching the surface of the Pt electrode layer to open a window;

[0014] (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;

[0015] (6) Repeat step (5) to obtain.

[0016] Furthermore, in step (1), the insulating layer is SiO2, with a thickness of 300-350µm, and the ultrasonic time is 3-10min.

[0017] Furthermore, in step (1), the metal is Cr, Ir, Ti, Al or Ta.

[0018] 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.

[0019] Furthermore, the thickness of the Si3N4 film in step (4) is 350-400 nm.

[0020] Furthermore, in step (5), the thickness of the W electrode layer is 10-15 nm.

[0021] The present invention has the following beneficial effects:

[0022] (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 is possible to ensure that the resulting crystals have high-quality characteristics.

[0023] (2) The thermal protection structure of the present invention can effectively prevent the metal electrode layer from agglomerating at high temperatures, preventing a sudden increase in resistance, while ensuring that the electrode surface remains bare and does not affect wire bonding. This ensures the stability of the sensor's output signal and improves 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 aerospace, oil exploration, metallurgy, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the overall structure of the thermal protection structure of Example 1 of the present invention;

[0025] Figure 2 Schematic diagram of step (2) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0026] Figure 3 Schematic diagram of step (4) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0027] Figure 4 Schematic diagram of step (5) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0028] Figure 5 Schematic diagram of step (6) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0029] Figure 6 Schematic diagram of step (7) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0030] Figure 7 Schematic diagram of step (8) in the method for preparing a thermal protection structure according to Example 1 of the present invention;

[0031] Figure 8 Graph showing resistance changes of electrode sensor samples having the heat protection structures of Example 1 and the comparative example at high temperatures;

[0032] Figure 9 These are actual images under an electron microscope of the thermal protection structures of Example 1 of the present invention and the comparative example after being heated to 1200°C. DETAILED DESCRIPTION

[0033] The following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, the experiments were performed under conventional conditions or those recommended by the manufacturer. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0034] Example 1:

[0035] A thermal protection structure for a metal electrode of a sensor chip, comprising: 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 includes the following steps:

[0036] (1) Using 350µm thick double-polished Si wafer as substrate material;

[0037] (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;

[0038] (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 6 seconds to evenly distribute the photoresist 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.

[0039] (4) Pattern the electrode part, etch out the buried bottom electrode cavity, and then magnetron sputter 5nm thick Cr metal as the electrode buffer layer (see Figure 3 );

[0040] (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 the negative resist is removed by soaking in acetone to obtain a Pt electrode layer;

[0041] (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 (see Figure 5 );

[0042] (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit in 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 );

[0043] (8) Magnetron sputtering of 10 nm W electrode layer on the Pt electrode layer (see Figure 7 );

[0044] (9) 10 nm Pt electrode layer on the W electrode layer;

[0045] (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.

[0046] Example 2:

[0047] A thermal protection structure for a sensor chip metal electrode comprises: a sensor chip substrate, an electrode buffer layer, and a Pt-W continuous multilayer metal electrode layer; the electrode buffer layer is disposed on the sensor chip substrate, and the Pt-W continuous multilayer metal electrode layer is disposed on the electrode buffer layer. The preparation method comprises the following steps:

[0048] (1) A 300µm thick double-polished Si wafer is used as the substrate material;

[0049] (2) Deposit a 350nm thick SiO2 insulating layer, clean the chip substrate material, and ultrasonicate with acetone, anhydrous ethanol, and water for 10 minutes in sequence, and then blow dry with N2;

[0050] (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 AZ4620 photoresist was evenly applied on the pretreated chip. The forward rotation speed was 600 rpm for 10 seconds to evenly distribute the photoresist 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 evenly applied was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist.

[0051] (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;

[0052] (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 immersion in acetone to obtain a Pt electrode layer;

[0053] (6) Dry transfer of a single-layer graphene onto the Pt electrode layer to produce a temperature-sensitive unit, and patterning the temperature-sensitive unit to expose the electrode for wire bonding;

[0054] (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit in 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;

[0055] (8) Magnetron sputtering a 12 nm thick W electrode intermediate layer on the Pt electrode layer;

[0056] (9) 12nm Pt electrode layer on W electrode layer;

[0057] (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.

[0058] Example 3:

[0059] A thermal protection structure for a sensor chip metal electrode comprises: a sensor chip substrate, an electrode buffer layer, and a Pt-W continuous multilayer metal electrode layer; the electrode buffer layer is disposed on the sensor chip substrate, and the Pt-W continuous multilayer metal electrode layer is disposed on the electrode buffer layer. The preparation method comprises the following steps:

[0060] (1) Using 330µm thick double-polished Si wafer as substrate material;

[0061] (2) Deposit a 330nm thick SiO2 insulating layer, clean the chip substrate material, and use acetone, anhydrous ethanol, and water ultrasonic treatment for 3 minutes in sequence, and then blow dry with N2;

[0062] (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 500 rpm for 5 seconds to evenly distribute the photoresist 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 evenly applied was placed on a hot plate at 95°C and baked for 5 minutes to fix the photoresist.

[0063] (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;

[0064] (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 immersion in acetone to obtain a Pt electrode layer;

[0065] (6) Dry transfer of a single-layer graphene onto the Pt electrode layer to produce a temperature-sensitive unit, and patterning the temperature-sensitive unit to expose the electrode for wire bonding;

[0066] (7) A 400 nm thick Si3N4 film is deposited on the temperature-sensitive unit in 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;

[0067] (8) Magnetron sputtering of a 15 nm thick W electrode intermediate layer on the Pt electrode layer;

[0068] (9) 15nm Pt electrode layer on W electrode layer;

[0069] (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.

[0070] Comparative Example:

[0071] 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 disposed on the sensor chip substrate, and the Pt metal electrode layer is disposed on the electrode buffer layer. The preparation method comprises the following steps:

[0072] (1) Using 350µm thick double-polished Si wafer as substrate material;

[0073] (2) Deposit a 300nm thick SiO2 insulating layer, clean the chip substrate material, and ultrasonicate it with acetone, anhydrous ethanol, and water for 5 minutes in sequence, and then blow dry it with N2;

[0074] (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 r / s for 6 seconds to evenly distribute the photoresist on the substrate. The backward rotation speed was 4000 r / s for 30 seconds to adjust the thickness of the photoresist. The chip with the photoresist evenly applied was placed on a hot plate and baked at 95°C for 5 minutes to fix the photoresist.

[0075] (4) Patterning the electrode part, etching out the buried bottom electrode cavity, and then magnetron sputtering 5nm thick Cr metal as the electrode buffer layer;

[0076] (5) A 200 nm thick Pt metal is magnetron sputtered on the surface of the product obtained in step (4) as an electrode layer.

[0077] Experimental example:

[0078] (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 stabilized, a multimeter was used to record the resistance data. One group of data was recorded every 100°C. The statistical results are shown as follows: Figure 8 As shown. Figure 8 As can be seen, the single Pt electrode sensor in the comparative example experiences a resistance surge at around 800°C, while the continuous multilayer Pt-W electrode sensor in Example 1 effectively suppresses this surge in electrode resistance, maintaining good stability up to 1200°C. This demonstrates that the Pt-W continuous multilayer electrode structure of the present invention can prevent sudden increases in electrode resistance at high temperatures, thereby ensuring a stable electrical signal output by the sensor and improving its reliability in complex environments.

[0079] (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. The electrode surface was observed under an electron microscope. The results are shown in Figure 2. Figure 9 As shown, Figure 9 A is the Pt-W continuous multilayer structure electrode diagram of Example 1, Figure 9 Figure B shows a single Pt metal electrode in the comparative example. Figure 9 shows that after 2 hours of high-temperature treatment at 1200°C, the electron microscope image of the single Pt metal electrode reveals surface agglomeration and increased surface roughness. However, the Pt-W continuous multilayer electrode exhibits no significant change. This demonstrates that the Pt-W continuous multilayer electrode structure of the present invention significantly improves Pt crystal quality, effectively preventing the secondary crystallization phenomenon, known as "agglomeration," that can occur in Pt electrodes at temperatures above 800°C.

[0080] 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 principles of the present invention should be included in the scope of protection 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; The number of layers of the Pt-W electrode layer is 15-21, and the thickness of each layer is 20-30 nm; The method for preparing the thermal protection structure comprises the following steps: (1) Deposit an insulating layer on the sensor chip substrate, then pattern the electrode portion on its surface, etch out the buried bottom electrode cavity, and then magnetron sputter metal to produce the 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 thin film on the surface of the temperature-sensitive unit to obtain a high-temperature protective layer for the temperature-sensitive unit, and then etching the surface of the Pt electrode layer to open a window; (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.

2. The heat protection structure according to claim 1, characterized in that: The sensor chip substrate is Si wafer, Al2O3, SiC, SiN or 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 insulating layer in step (1) is SiO2 with a thickness of 300-350µm.

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

6. The heat protection structure according to claim 1, 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.

7. The heat protection structure according to claim 1, characterized in that: The thickness of the Si3N4 film in step (4) is 350-400 nm.

8. The heat protection structure according to claim 1, characterized in that: The thickness of the W electrode layer in step (5) is 10-15 nm.

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