MEMS atomic gas chamber integrated with heat shielding layer and preparation method of MEMS atomic gas chamber
By employing a layered structure and a MEMS atomic gas chamber filled with insulating material in the atomic clock, the problem of insufficient heat insulation in the atomic clock has been solved, achieving temperature uniformity and equipment stability, extending service life and reducing maintenance costs.
Patent Information
- Application Number
- CN202511311742.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-15
- Publication Date
- 2025-11-11
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing methods for controlling the temperature of atomic clocks have limited insulation effects, which affect the state of rubidium vapor and frequency stability.
The structure employs a top-to-bottom stacked first glass substrate, silicon substrate, and second glass substrate. Through-holes and concentric annular holes/grooves are provided on the silicon substrate. The holes/grooves are filled with heat-insulating material. The two ends of the through-holes are sealed by the glass substrate to form a sealed cavity. The cavity is filled with alkali metal vapor. The MEMS atomic gas chamber with an integrated heat shielding layer is fabricated by combining anodic bonding technology.
It improves the heat insulation effect, maintains temperature uniformity, reduces the impact of temperature fluctuations on equipment performance, extends equipment life and reduces maintenance costs.
Smart Images
Figure CN120928670A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microelectromechanical systems (MEMS) and precision timing technology, specifically relating to a MEMS atomic gas cell with an integrated thermal shielding layer and its preparation method. Background Technology
[0002] Atomic clocks are crucial instruments for precise time measurement, widely used in GPS, communication networks, and scientific research. Advances in MEMS technology have enabled the significant miniaturization of atomic clock devices while maintaining or improving their performance. However, the accuracy of atomic clocks is highly dependent on the precision of temperature control, as temperature fluctuations directly affect the state of rubidium vapor and the frequency stability of the atomic clock.
[0003] Currently, various methods are used for temperature control in atomic clocks. Traditional methods include using metal or ceramic-based heaters, which directly heat critical components of the atomic clock via resistance heating elements. These systems typically rely on thick outer casings or additional insulation layers to maintain stable internal temperatures. For example, some designs integrate heating elements on silicon-based platforms, utilizing silicon's excellent thermal conductivity for rapid heat transfer; however, this method offers limited and low insulation performance. Therefore, improving insulation performance has become a pressing technical problem to be solved in this field. Summary of the Invention
[0004] The purpose of this invention is to provide a MEMS atomic gas cell with an integrated heat shielding layer and its fabrication method. The MEMS atomic gas cell provided by this invention has high integration and good heat insulation effect.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0006] This invention provides a MEMS atomic gas cell with an integrated heat shield layer, comprising a first glass substrate, a silicon substrate, and a second glass substrate stacked from top to bottom;
[0007] The silicon substrate is provided with through holes penetrating the upper and lower surfaces and annular holes / annular grooves concentric with the through holes;
[0008] The annular hole / annular groove is filled with heat-insulating material;
[0009] The two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity;
[0010] The sealed cavity is filled with alkali metal vapor.
[0011] Preferably, the cross-section of the through hole is circular, square, or polygonal, the diameter of the circular hole is 2 to 20 mm, and the side length of the square and polygonal holes is independently 2 to 20 mm; the thickness of the silicon substrate is 0.6 mm to 1 cm.
[0012] Preferably, the width of the annular hole and the annular groove are independently 10 μm to 5 mm.
[0013] Preferably, the depth of the annular groove is 500 μm to 3 mm.
[0014] Preferably, the thermal insulation material is an aerogel, which is at least one of silica aerogel, carbon-based aerogel, polymer aerogel, and ceramic aerogel.
[0015] Preferably, the aerogel has a pore size of 2–300 nm, a porosity of 75–99.9%, and a specific surface area of 500–1500 m². 2 / g, density is 0.003~0.5g / cm³ 3 .
[0016] This invention also provides a method for fabricating a MEMS atomic gas cell with an integrated heat shielding layer as described in the above technical solution, comprising the following steps:
[0017] The silicon substrate and the second glass substrate are anoly bonded for the first time to obtain the first intermediate.
[0018] Through-holes and annular holes / annular grooves are fabricated on the silicon substrate of the first intermediate to obtain the second intermediate;
[0019] The annular hole / groove of the second intermediate is filled with heat-insulating material, and then alkali metal vapor is injected into the through hole. Then, a second anodic bonding is performed with the first glass substrate to obtain the MEMS atomic gas chamber with integrated heat shielding layer.
[0020] Preferably, the temperature for the first anodic bonding and the second anodic bonding are 300–400°C, the DC voltage is 500–1000V, the pressure is 0.5–2kN, and the time is 5–30min.
[0021] Preferably, a photolithographic opening is first made on the silicon substrate of the first intermediate, and then a through hole and annular hole / annular groove are prepared at the opening using a DRIE deep etching process.
[0022] Preferably, the process parameters of the DRIE deep etching process include: the etching gas is SF6 with a flow rate of 100-150 sccm; the passivation gas is C4F8 with a flow rate of 80-100 sccm; and the auxiliary gas is O2 with a flow rate of 5-10 sccm.
[0023] This invention provides a MEMS atomic gas chamber with an integrated heat shield layer, comprising a first glass substrate, a silicon substrate, and a second glass substrate stacked from top to bottom. The silicon substrate has through-holes penetrating its upper and lower surfaces and annular holes / grooves concentric with the through-holes. Thermal insulation material is disposed within the annular holes / grooves. The two ends of the through-holes are sealed by the first and second glass substrates, forming a sealed cavity. The sealed cavity is filled with alkali metal vapor. The sealing of the two ends of the through-holes by the first and second glass substrates forms a sealed cavity, which is a metal gas chamber used for time and frequency control of an atomic clock. Annular holes / grooves concentric with the through-holes are also provided on the silicon substrate, and thermal insulation material is disposed within the annular holes / grooves, forming an effective heat insulation layer, thereby improving the heat insulation effect. Results from embodiments show that the aerogel-filled holes or deep grooves can effectively block heat transfer to the center of the through-holes; when externally heated to 100°C, the temperature of the central region can be maintained below 30°C, with a temperature difference exceeding 70°C. Attached Figure Description
[0024] Figure 1 A side view of the MEMS atomic gas chamber with an integrated thermal shielding layer provided by the present invention.
[0025] Figure 2 A top view of the MEMS atomic gas chamber with an integrated thermal shielding layer provided by the present invention;
[0026] Figure 3 A process flow diagram for fabricating a MEMS atomic gas cell with an integrated thermal shielding layer in Example 1;
[0027] Figure 4 A side view of the MEMS atomic gas chamber with an integrated thermal shielding layer provided by the present invention.
[0028] Figure 5 This is a process flow diagram of the MEMS atomic gas cell with integrated heat shielding layer prepared in Example 2;
[0029] Figure 6 The temperature distribution at the via interface in a silicon substrate is shown in the MEMS atomic gas cell of the integrated thermal shielding layer prepared in Example 1 under heating conditions of 20–100 °C.
[0030] Figure 7 The temperature distribution at the via interface in a silicon substrate is shown in the MEMS atomic gas cell of the integrated thermal shielding layer prepared in Example 2 under heating conditions of 20–100 °C. Detailed Implementation
[0031] This invention provides a MEMS atomic gas cell with an integrated heat shield layer, comprising a first glass substrate, a silicon substrate, and a second glass substrate stacked from top to bottom;
[0032] The silicon substrate is provided with through holes penetrating the upper and lower surfaces and annular holes / annular grooves concentric with the through holes;
[0033] The annular hole / annular groove is filled with heat-insulating material;
[0034] The two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity;
[0035] The sealed cavity is filled with alkali metal vapor.
[0036] The present invention does not have any special limitation on the source of materials for each component in the MEMS atomic gas chamber of the integrated heat shield layer; commercially available products known to those skilled in the art can be used.
[0037] like Figure 1 As shown, in this invention, the MEMS atomic gas cell with integrated thermal shielding layer provided by this invention includes a first glass substrate.
[0038] like Figure 2 As shown, the cross-section of the first glass substrate is circular. The present invention does not impose a specific limitation on the diameter of the circle; it can be adjusted according to actual needs.
[0039] In this invention, the thickness of the first glass substrate is preferably 500 μm to 2 mm. As one embodiment, the thickness of the first glass substrate can be 1 mm or 1.5 mm. This invention does not impose any special limitations on the material of the first glass substrate; any glass substrate well-known to those skilled in the art can be used.
[0040] In one embodiment, the first glass substrate can be made of Pyrex 7740 or Borofloat 33. In this invention, the coefficient of thermal expansion of the first glass substrate is 3.3 × 10⁻⁶. -6 / K, which is compatible with silicon.
[0041] like Figure 1 As shown, in this invention, the MEMS atomic gas chamber with integrated thermal shielding layer provided by this invention includes a silicon substrate disposed on the lower surface of the first glass substrate.
[0042] like Figures 1-3 As shown, in this invention, the silicon substrate is provided with through holes penetrating the upper and lower surfaces and annular holes / grooves concentric with the through holes; heat-insulating material is disposed in the annular holes / grooves.
[0043] In this invention, the cross-section of the through-hole is preferably circular, square, or polygonal; the diameter of the circular hole is preferably 2–20 mm; the side length of the square and polygonal holes is independently preferably 2–20 mm; and the thickness of the silicon substrate is preferably 0.6 mm–1 cm. As one embodiment, the diameter of the circular hole can be 5 mm, 6 mm, 10 mm, or 15 mm; the side length of the square and polygonal holes can independently be 5 mm, 10 mm, or 15 mm; and the thickness of the silicon substrate can be 1 mm, 5 mm, 6 mm, 7 mm, 8 mm, or 9 mm.
[0044] like Figure 2 As shown, the silicon substrate has a circular cross-section. The present invention does not impose a specific limitation on the diameter of the circle, as long as it matches the diameter of the first glass substrate.
[0045] The present invention does not have any special limitation on the material of the silicon substrate, and any silicon substrate well known to those skilled in the art can be used.
[0046] In one embodiment, the silicon substrate can be p-type or n-type (100) material; the resistivity of the silicon substrate can be 0.01 to 10 Ω·cm; and the surface roughness of the silicon substrate can be <10 nm.
[0047] In this invention, the width of the annular hole and the annular groove are preferably 10 μm to 5 mm; the depth of the annular groove is preferably 500 μm to 3 mm. As one embodiment, the width of the annular hole and the annular groove can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 1 mm, 2 mm, 3 mm, or 4 mm; the depth of the annular groove can be 600 μm, 700 μm, 800 μm, 900 μm, 1 mm, or 2 mm.
[0048] In this invention, the shape of the annular hole is preferably a circular annular hole or a square annular hole; the inner diameter of the circular annular hole is preferably 2-15 mm; the inner side length of the square annular hole is preferably 4-15 mm. As one embodiment, the inner diameter of the circular annular hole can be 3 mm, 4 mm, 5 mm, 5.8 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or 14 mm; the inner side length of the square annular hole can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or 14 mm.
[0049] In this invention, the shape of the annular groove is preferably a circular annular groove or a square annular groove; the inner diameter of the circular annular groove is preferably 2-15 mm; the inner side length of the square annular groove is preferably 4-15 mm. As one embodiment, the inner diameter of the circular annular groove can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or 14 mm; the inner side length of the square annular groove can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or 14 mm.
[0050] In this invention, the thermal insulation material is preferably an aerogel, and the aerogel is preferably at least one of silica aerogel, carbon-based aerogel, polymer aerogel, and ceramic aerogel; the carbon-based aerogel is preferably graphene aerogel and / or carbon nanotube aerogel; the polymer aerogel is preferably polyimide aerogel and / or cellulose aerogel; and the ceramic aerogel is preferably Al2O3 aerogel and / or ZrO2 aerogel. In this invention, the aerogel has extremely low thermal conductivity, and filling it into annular holes / grooves can form an effective thermal insulation layer; the use of aerogel not only improves the thermal insulation effect but also reduces the weight of the entire device, maintaining the portability of the equipment.
[0051] In this invention, the pore size of the aerogel is preferably 2–300 nm; the porosity of the aerogel is preferably 75–99.9%; and the specific surface area of the aerogel is preferably 500–1500 m². 2 / g; the density of the aerogel is preferably 0.003-0.5 g / cm³. 3 The present invention limits the pore size, porosity, specific surface area, and density of the aerogel within the above-mentioned ranges, thereby further improving its thermal insulation effect.
[0052] In one embodiment, the pore size of the aerogel can be 50 nm, 100 nm, 150 nm, 200 nm, or 250 nm; the porosity of the aerogel can be 80%, 85%, 90%, or 95%; and the specific surface area of the aerogel can be 800 m². 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g or 1400m 2 / g; the density of the aerogel can be 0.005 g / cm³. 3 0.1g / cm 3 0.2g / cm 3 0.3g / cm 3or 0.4g / cm 3 .
[0053] like Figure 1 As shown, in this invention, the MEMS atomic gas cell of the integrated thermal shielding layer provided by this invention includes a second glass substrate disposed on the lower surface of the silicon substrate.
[0054] In this invention, the second glass substrate has the same material, thickness and size as the first glass substrate, which will not be described in detail here.
[0055] like Figure 1 As shown, the two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity; the sealed cavity is filled with alkali metal vapor.
[0056] The present invention does not specifically limit the type of alkali metal vapor, and any alkali metal vapor well known to those skilled in the art can be used.
[0057] In one embodiment, the alkali metal vapor can be cesium or rubidium.
[0058] The atomic gas chamber provided by this invention aims to effectively insulate and preserve heat while maintaining the device's lightweight and structural integrity. By integrating the insulation layer into the device's interior, it offers advantages such as high integration, small size, and low cost. It is compatible with micro / nano manufacturing technologies, enabling mass production. Using aerogel as the insulating material, it is lightweight, has excellent thermal insulation properties, effectively isolates and preserves heat, and reduces heat loss. This optimized thermal management not only maintains temperature uniformity within the system but also helps prevent the impact of external temperature fluctuations on device performance.
[0059] The atomic gas chamber provided by this invention simplifies the design of the temperature control system for atomic clocks, reducing the need for complex insulation structures. Using aerogel as the insulation material achieves better insulation with less material, thereby reducing material costs and manufacturing complexity. It considers various operating environments, ensuring the atomic clock maintains high performance under different temperatures and environmental conditions. The use of aerogel enhances the system's adaptability to environmental changes, especially its stability under extreme temperature conditions. The efficient thermal management structure (insulation structure) reduces the risk of long-term damage and performance degradation caused by temperature fluctuations. This not only extends the equipment's service life but also reduces maintenance costs.
[0060] This invention also provides a method for fabricating a MEMS atomic gas cell with an integrated heat shielding layer as described in the above technical solution, comprising the following steps:
[0061] The silicon substrate and the second glass substrate are anoly bonded for the first time to obtain the first intermediate.
[0062] Through-holes and annular holes / annular grooves are fabricated on the silicon substrate of the first intermediate to obtain the second intermediate;
[0063] The annular hole / groove of the second intermediate is filled with heat-insulating material, and then alkali metal vapor is injected into the through hole. Then, a second anodic bonding is performed with the first glass substrate to obtain the MEMS atomic gas chamber with integrated heat shielding layer.
[0064] The present invention performs a first anodic bonding between a silicon substrate and a second glass substrate to obtain a first intermediate.
[0065] In this invention, the silicon substrate is preferably subjected to RCA cleaning and oxygen plasma cleaning sequentially before use. This method of sequentially using RCA cleaning and oxygen plasma cleaning on the silicon substrate removes organic residues and activated surfaces.
[0066] In this invention, the RCA cleaning and oxygen plasma cleaning are preferably performed in a nitrogen atmosphere; the nitrogen pressure is preferably 10. -3 ~10 -5 mbar. As one implementation, the nitrogen pressure can be 10 mbar. -4 mbar.
[0067] In this invention, the temperature of the first anodic bonding is preferably 300-400°C; the DC voltage of the first anodic bonding is preferably 500-1000V; the pressure of the first anodic bonding is preferably 0.5-2kN; and the time of the first anodic bonding is preferably 5-30min.
[0068] In one embodiment, the temperature of the first anodic bonding can be 350°C; the DC voltage of the first anodic bonding can be 600V, 700V, 800V or 900V; the pressure of the first anodic bonding can be 1kN or 1.5kN; and the time of the first anodic bonding can be 10min, 15min, 20min or 25min.
[0069] After obtaining the first intermediate, the present invention prepares through holes and annular holes / annular grooves on the silicon substrate of the first intermediate to obtain the second intermediate.
[0070] In this invention, photolithographic openings are preferably first made on the silicon substrate of the first intermediate, and then through holes and annular holes / annular grooves are prepared at the openings using a DRIE deep etching process.
[0071] In this invention, the preferred photolithography process parameters include: the mask material is photoresist or a hard mask; the hard mask includes SiO2 or SiN. xThe photoresist thickness is 10–200 μm; the hard mask thickness is 1–5 μm; the exposure wavelength is 365 nm (i-line); high-resolution mask alignment is used; and the exposure dose is 300–400 mJ / cm². 2 The developing time is 60 seconds to 6 minutes; the post-drying temperature is 110°C; and the post-drying time is 2 minutes.
[0072] In one embodiment, the thickness of the photoresist can be 100 μm; the thickness of the hard mask can be 2 μm, 3 μm, or 4 μm; and the exposure dose can be 320 mJ / cm². 2 340mJ / cm 2 Or 360mJ / cm 2 The development time can be 70s or 80s.
[0073] The present invention does not have any special limitations on the material of the photoresist; any photoresist known to those skilled in the art can be used.
[0074] In one implementation, when the mask material is SU-8 photoresist, the exposure dose can be 350–400 mJ / cm. 2 .
[0075] The present invention does not have any particular limitation on the type of developer; any developer well known to those skilled in the art can be used.
[0076] As one embodiment, the developer can be PGMEA (propylene glycol methyl ether acetate).
[0077] In this invention, the preferred process parameters for the DRIE deep etching process include: SF6 as the etching gas, with a flow rate of 100–150 sccm; C4F8 as the passivation gas, with a flow rate of 80–100 sccm; O2 as the auxiliary gas, with a flow rate of 5–10 sccm; ICP power of 2000–2500 W; RF bias power of 20–50 W; chamber pressure of 10–15 mTorr; etching time of 3–8 s and passivation time of 3–5 s per etching cycle; substrate temperature of -10℃ to +20℃; and etching rate of 2–4 μm / min. In this invention, the etching gas is the primary etching gas, the passivation gas is used for sidewall protection, and the auxiliary gas improves anisotropy. Limiting the ICP power within the above range allows for the acquisition of high-density plasma; limiting the RF bias power within the above range allows for the control of ion bombardment energy.
[0078] In one embodiment, the flow rate of the etching gas can be 120 sccm, 130 sccm, or 140 sccm; the flow rate of the passivation gas can be 90 sccm; the flow rate of the auxiliary gas can be 6 sccm, 7 sccm, 8 sccm, or 9 sccm; the ICP power can be 2100W, 2200W, 2300W, or 2400W; the RF bias power can be 30W or 40W; the chamber pressure can be 11 mTorr, 12 mTorr, 13 mTorr, or 14 mTorr; the etching time in each etching cycle can be 3s, 4s, 5s, 6s, or 7s; the passivation time can be 4s; the substrate temperature can be -5℃, 0℃, 5℃, 10℃, or 15℃; and the etching rate can be 3 μm / min.
[0079] The present invention does not have a specific limit on the number of etching cycles, as long as the required size is obtained through etching.
[0080] The preparation method provided by this invention is simple.
[0081] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0082] A side view of the MEMS atomic gas chamber with integrated heat shielding layer provided by this invention is shown in the figure below. Figure 1 and 4 As shown, a top view schematic diagram of the MEMS atomic gas chamber with integrated heat shielding layer provided by the present invention is shown below. Figure 2 As shown.
[0083] Example 1
[0084] like Figure 1 and 2 As shown, the MEMS atomic gas cell with integrated heat shielding layer is composed of a first glass substrate, a silicon substrate and a second glass substrate stacked from top to bottom;
[0085] The silicon substrate is provided with through holes penetrating the upper and lower surfaces and an annular hole concentric with the through holes;
[0086] The annular hole is filled with heat-insulating material.
[0087] The two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity;
[0088] The sealed cavity is filled with alkali metal vapor;
[0089] The first glass substrate is a circular piece with a diameter of 10 cm;
[0090] The thickness of the first glass substrate is 1 mm;
[0091] The first glass substrate is made of Pyrex 7740.
[0092] The through-hole has a circular cross-section; the diameter of the circle is 4 mm; the thickness of the silicon substrate is 0.6 mm;
[0093] The silicon substrate is a circular wafer with a diameter of 10 cm;
[0094] The silicon substrate is made of p-type silicon with a resistivity of 0.01 Ω·cm.
[0095] The width of the annular hole is 0.1 mm; the shape of the annular hole is circular, and the inner diameter of the annular hole is 5.8 mm;
[0096] The thermal insulation material is an aerogel, and the aerogel is a silica aerogel;
[0097] The aerogel has a pore size of 2–300 nm; a porosity of 80%; and a specific surface area of 1000 m². 2 / g; the density of the aerogel is 0.1 g / cm³. 3 ;
[0098] The second glass substrate is a disc with a diameter of 10 cm;
[0099] The thickness of the second glass substrate is 1 mm;
[0100] The material of the second glass substrate is Pyrex 7740;
[0101] The type of alkali metal vapor is rubidium;
[0102] The method for fabricating the MEMS atomic gas cell with the integrated heat shielding layer is as follows:
[0103] The silicon substrate was subjected to RCA cleaning and oxygen plasma cleaning sequentially in a nitrogen atmosphere at a pressure of 10. - 3 mbar, and then the silicon substrate and the second glass substrate are anoly bonded for the first time to obtain the first intermediate; wherein, the temperature of the first anoly bonding is 350°C, the DC voltage is 1000V, the pressure is 1kN, and the time is 20min.
[0104] A photolithographic opening is first made on the silicon substrate of the first intermediate, and then a through hole and annular hole are prepared at the opening using a DRIE deep etching process to obtain the second intermediate.
[0105] The photolithography process parameters are as follows: the mask material is SU-8 photoresist; the photoresist thickness is 100 μm; and the exposure dose is 400 mJ / cm. 2 The developer was PGMEA (propylene glycol methyl ether acetate); the development time was 6 minutes; the post-baking temperature was 110°C; and the post-baking time was 2 minutes.
[0106] The process parameters for the DRIE deep etching process are as follows: etching gas is SF6, flow rate is 100 sccm; passivation gas is C4F8, flow rate is 80 sccm; auxiliary gas is O2, flow rate is 5 sccm; ICP power is 2000W; RF bias power is 20W; chamber pressure is 15 mTorr; etching time is 5s and passivation time is 3s in each etching cycle; substrate temperature is -10℃; etching rate is 4μm / min.
[0107] The annular hole of the second intermediate is filled with heat-insulating material, and then alkali metal vapor is injected into the through hole. Then, a second anodic bonding is performed with the first glass substrate to obtain the MEMS atomic gas chamber with integrated heat shielding layer. The temperature of the second anodic bonding is 350°C, the DC voltage is 1000V, the pressure is 2kN, and the time is 30min.
[0108] Example 1: The process flow diagram for fabricating the MEMS atomic gas cell with integrated heat shielding layer is shown below. Figure 3 As shown.
[0109] Example 2
[0110] The structure of the MEMS atomic gas cell with integrated heat shielding layer is as follows: Figure 2 and 4 As shown,
[0111] The MEMS atomic gas cell with integrated heat shielding layer is composed of a first glass substrate, a silicon substrate and a second glass substrate stacked from top to bottom;
[0112] The silicon substrate is provided with through holes penetrating the upper and lower surfaces and an annular groove concentric with the through holes;
[0113] The annular groove is filled with heat-insulating material;
[0114] The two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity;
[0115] The sealed cavity is filled with alkali metal vapor;
[0116] The first glass substrate is a circular piece with a diameter of 10 cm;
[0117] The thickness of the first glass substrate is 1 mm;
[0118] The first glass substrate is made of Pyrex 7740.
[0119] The through-hole has a circular cross-section; the diameter of the circle is 3mm; the thickness of the silicon substrate is 0.6mm;
[0120] The silicon substrate is a circular wafer with a diameter of 10 cm;
[0121] The silicon substrate is made of p-type silicon with a resistivity of 0.01 Ω·cm.
[0122] The annular groove has a width of 1 mm and a depth of 500 μm; the annular groove is circular in shape and has an inner diameter of 4 mm.
[0123] The thermal insulation material is an aerogel, and the aerogel is a silica aerogel;
[0124] The aerogel has a pore size of 2–300 nm; a porosity of 80%; and a specific surface area of 1000 m². 2 / g; the density of the aerogel is 0.1 g / cm³. 3 ;
[0125] The second glass substrate is a disc with a diameter of 10 cm;
[0126] The thickness of the second glass substrate is 1 mm;
[0127] The material of the second glass substrate is Pyrex 7740;
[0128] The type of alkali metal vapor is rubidium;
[0129] The method for fabricating the MEMS atomic gas cell with the integrated heat shielding layer is as follows:
[0130] The silicon substrate was subjected to RCA cleaning and oxygen plasma cleaning sequentially in a nitrogen atmosphere at a pressure of 10. - 3 mbar, and then the silicon substrate and the second glass substrate are anoly bonded for the first time to obtain the first intermediate; wherein, the temperature of the first anoly bonding is 350°C, the DC voltage is 1000V, the pressure is 1kN, and the time is 20min.
[0131] First, a photolithographic opening is made on the silicon substrate of the first intermediate, and then a through hole and annular groove are made at the opening using the DRIE deep etching process to obtain the second intermediate.
[0132] The photolithography process parameters are as follows: the mask material is SU-8 photoresist; the photoresist thickness is 100 μm; and the exposure dose is 400 mJ / cm. 2 The developer was PGMEA (propylene glycol methyl ether acetate); the development time was 6 minutes; the post-baking temperature was 110°C; and the post-baking time was 2 minutes.
[0133] The process parameters for the DRIE deep etching process are as follows: etching gas is SF6, flow rate is 100 sccm; passivation gas is C4F8, flow rate is 80 sccm; auxiliary gas is O2, flow rate is 5 sccm; ICP power is 2000W; RF bias power is 20W; chamber pressure is 15 mTorr; etching time is 3s and passivation time is 3s in each etching cycle; substrate temperature is -10℃; etching rate is 4μm / min.
[0134] The annular groove of the second intermediate is filled with heat-insulating material, and then alkali metal vapor is injected into the through hole. Then, a second anodic bonding is performed with the first glass substrate to obtain the MEMS atomic gas chamber with integrated heat shielding layer. The temperature of the second anodic bonding is 350°C, the DC voltage is 1000V, the pressure is 2kN, and the time is 30min.
[0135] Example 2: The process flow diagram for fabricating the MEMS atomic gas cell with integrated heat shielding layer is shown below. Figure 5 As shown.
[0136] Example 3
[0137] Based on Example 2, the width of the annular groove was changed to 100 μm, the depth was changed to 550 μm, the thickness of the photoresist was 100 μm, the etching time was 4 s and the passivation time was 4 s in each etching cycle, and other conditions remained unchanged.
[0138] The MEMS atomic gas cells of the integrated thermal shielding layers prepared in Examples 1-3 were externally heated at 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 100°C, respectively. The temperature distribution at the via interface in the silicon substrate is shown below. Figures 6-7 As shown, where, Figure 6 The temperature distribution at the via interface in a silicon substrate is shown in the MEMS atomic gas cell of the integrated thermal shielding layer prepared in Example 1 under heating conditions of 20–100 °C. Figure 7 The temperature distribution of the MEMS atomic gas cell with integrated thermal shielding layer prepared in Example 2 at the interface of the via in the silicon substrate under heating conditions of 20-100℃ (in the figure, the curves from bottom to top correspond to 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ and 100℃ respectively).
[0139] from Figures 6-7 It can be seen that the aerogel-filled pores or deep grooves can effectively block heat transfer to the center of the through hole; when heated to 100°C externally, the temperature of the central area can be kept below 30°C, with a temperature difference of more than 70°C, which can be used for microelectronics and MEMS applications that require local temperature control.
[0140] Example 3 also achieved similar technical effects to Examples 1 and 2, where the aerogel-filled deep groove effectively blocked heat transfer to the center of the through hole.
[0141] As can be seen from the embodiments, the MEMS atomic gas cell of the integrated heat shield layer provided by the present invention has high integration and good heat insulation effect.
[0142] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A MEMS atomic gas cell with an integrated thermal shielding layer, comprising a first glass substrate, a silicon substrate, and a second glass substrate stacked from top to bottom; The silicon substrate is provided with through holes penetrating the upper and lower surfaces and annular holes / annular grooves concentric with the through holes; The annular hole / annular groove is filled with heat-insulating material; The two ends of the through hole are sealed by the first glass substrate and the second glass substrate to form a sealed cavity; The sealed cavity is filled with alkali metal vapor.
2. The MEMS atomic gas chamber with integrated thermal shielding layer according to claim 1, characterized in that, The cross-section of the through hole is circular, square, or polygonal, with the diameter of the circular hole being 2–20 mm, and the side length of the square and polygonal holes being 2–20 mm independently; the thickness of the silicon substrate is 0.6 mm–1 cm.
3. The MEMS atomic gas chamber with integrated thermal shielding layer according to claim 1, characterized in that, The widths of the annular hole and the annular groove are independently 10 μm to 5 mm.
4. The MEMS atomic gas chamber with integrated thermal shielding layer according to claim 1, characterized in that, The depth of the annular groove is 500 μm to 3 mm.
5. The MEMS atomic gas chamber with integrated thermal shielding layer according to claim 1, characterized in that, The thermal insulation material is an aerogel, which is at least one of silica aerogel, carbon-based aerogel, polymer aerogel, and ceramic aerogel.
6. The MEMS atomic gas chamber with integrated thermal shielding layer according to claim 5, characterized in that, The aerogel has a pore size of 2–300 nm, a porosity of 75–99.9%, and a specific surface area of 500–1500 m². 2 / g, density is 0.003~0.5g / cm³ 3 .
7. A method for fabricating a MEMS atomic gas cell with an integrated thermal shielding layer as described in any one of claims 1 to 6, comprising the following steps: The silicon substrate and the second glass substrate are anoly bonded for the first time to obtain the first intermediate. Through-holes and annular holes / annular grooves are fabricated on the silicon substrate of the first intermediate to obtain the second intermediate; The annular hole / groove of the second intermediate is filled with heat-insulating material, and then alkali metal vapor is injected into the through hole. Then, a second anodic bonding is performed with the first glass substrate to obtain the MEMS atomic gas chamber with integrated heat shielding layer.
8. The preparation method according to claim 7, characterized in that, The temperature for the first and second anodic bonding is 300–400℃, the DC voltage is 500–1000V, the pressure is 0.5–2kN, and the time is 5–30min.
9. The preparation method according to claim 7, characterized in that, On the silicon substrate of the first intermediate, a photolithographic opening is first made, and then a through hole and annular hole / annular groove are prepared at the opening using a DRIE deep etching process.
10. The preparation method according to claim 9, characterized in that, The process parameters of the DRIE deep etching process include: the etching gas is SF6 with a flow rate of 100-150 sccm; the passivation gas is C4F8 with a flow rate of 80-100 sccm; and the auxiliary gas is O2 with a flow rate of 5-10 sccm.