阅读说明：本技术 一种原子磁光阱芯片及加工方法 (Atomic magneto-optical trap chip and processing method ) 是由 李德钊 史胜南 王子轩 王肖隆 王煜猛 祁云峰 林强 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种原子磁光阱芯片及加工方法。本发明包括硅晶片和三维磁场线圈,硅晶片顶面中心向下开设的球缺形凹槽,形成反射腔。三维磁场线圈包括嵌在硅晶片顶面的上磁场线圈组和嵌在硅晶片底面的下磁场线圈组；上磁场线圈组包括四个均布在反射腔周围的椭圆形金属环,椭圆形金属环相对反射腔的远端具有开口,形成四个对称布置的开放式椭圆形金属线圈；下磁场线圈组包括两个与反射腔同心的金属圆环,其中内环的投影在四个椭圆形金属环的最小围合空间范围内,内、外金属圆环在同一角度具有开口,形成两个同心布置的开放式圆形金属线圈。本发明在结构上具有光学反射效率高,集成度好,加工简单及使用方便稳定性好的特点。(The invention discloses an atomic magneto-optical trap chip and a processing method thereof. The invention comprises a silicon wafer and a three-dimensional magnetic field coil, wherein a spherical segment-shaped groove is formed downwards in the center of the top surface of the silicon wafer to form a reflecting cavity. The three-dimensional magnetic field coil comprises an upper magnetic field coil group embedded on the top surface of the silicon wafer and a lower magnetic field coil group embedded on the bottom surface of the silicon wafer; the upper magnetic field coil group comprises four elliptical metal rings uniformly distributed around the reflecting cavity, and the elliptical metal rings are provided with openings at far ends relative to the reflecting cavity to form four symmetrically-arranged open elliptical metal coils; the lower magnetic field coil group comprises two metal circular rings concentric with the reflection cavity, wherein the projection of the inner ring is in the minimum enclosed space range of the four elliptical metal rings, and the inner metal circular ring and the outer metal circular ring are provided with openings at the same angle to form two open circular metal coils concentrically arranged. The invention has the characteristics of high optical reflection efficiency, good integration level, simple processing, convenient use and good stability.)

1. An atomic magneto-optical trap chip comprising a silicon wafer, the silicon wafer being a square sheet of polycrystalline or single crystal silicon material, characterized in that:

a reflection cavity and a three-dimensional magnetic field coil are arranged on the silicon wafer;

the reflecting cavity is a segment-shaped groove which is formed in the center of the top surface of the silicon wafer downwards;

the three-dimensional magnetic field coil comprises an upper magnetic field coil group embedded on the top surface of the silicon wafer and a lower magnetic field coil group embedded on the bottom surface of the silicon wafer;

the upper magnetic field coil group comprises four elliptical metal rings uniformly distributed around the reflecting cavity, and the far ends of the elliptical metal rings, which are opposite to the reflecting cavity, are provided with openings to form four open elliptical metal coils which are symmetrically arranged;

the lower magnetic field coil group comprises two metal circular rings concentric with the reflection cavity, wherein the projection of the inner ring is in the minimum enclosing space range of the four elliptical metal rings, and the inner metal circular ring and the outer metal circular ring are provided with openings at the same angle to form two open circular metal coils concentrically arranged.

2. The method for processing the atomic magneto-optical trap chip of claim 1, comprising the steps of:

selecting a conventional silicon crystal material which can be processed by a micro-nano processing technology as a sample crystal, and cleaning; the silicon crystal material is polysilicon or monocrystalline silicon;

respectively depositing corrosion-resistant protective layers with the thickness of 200 nm-350 nm on the two surfaces of the sample crystal by using a chemical deposition method;

step (3) according to the design, a circular ring is engraved in the center of the corrosion-resistant protective layer on one surface by a photoetching method;

removing the corrosion-resistant protective layer in the circular ring by using an ion beam etching method to expose the sample crystal and form a circular etching groove;

step (5), immersing the sample crystal with the etching groove into an HNA solution, wherein the HNA solution corrodes the sample crystal in a same manner to form a segment-shaped cambered groove;

taking out a sample crystal with a cambered surface groove, putting the sample crystal into an ICP etching machine, wherein the spherical crown surface of the cambered surface groove is SF₆Polishing by using a plasma etching method in the atmosphere;

step (7), immersing the sample crystal into selective corrosive liquid of a material of the corrosion-resistant protective layer, and removing the corrosion-resistant protective layers on the two sides;

step (8) etching four elliptical annular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed upper magnetic field coil group on the surface of the structural original with the cambered surface groove, and reserving photoresist; then preparing metal lines on the elliptical annular groove by using a metal sputtering method, and stripping photoresist to obtain an upper magnetic field coil group for generating a magnetic trap;

step (9) etching two concentric circular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed lower magnetic field coil group on the other surface of the structural original, and reserving photoresist; and then preparing metal lines on the circular grooves by using a metal sputtering method, and stripping photoresist to obtain a lower magnetic field coil group for generating the magnetic traps.

3. The method of fabricating the atomic magneto-optical trap chip of claim 1, wherein: the corrosion-resistant protective layer is made of silicon nitride or silicon dioxide.

4. The method of fabricating the atomic magneto-optical trap chip of claim 1, wherein: the selective corrosive liquid of the corrosion-resistant protective layer material only resists the corrosion of the corrosion-resistant protective layer material.

Technical Field

The invention belongs to the technical field of quantum, and particularly relates to an atomic magneto-optical trap chip with high integration level and a processing method thereof.

Background

Atomic magneto-optical traps have been widely used in different scenarios such as quantum information processing, atomic interferometers, chip-scale atomic clocks, atomic gravimeters, and chip-scale atomic magnetometers. According to the traditional atomic magneto-optical trap, the construction of a light path and a magnetic field of a magneto-optical trap system is realized by using macroscopic optics and magnetic field components, and the system is complex in structure and heavy in device. The atomic magneto-optical trap chip is a micro device which utilizes a micro-nano processing technology to realize atom trapping and cooling. The device can generate an adjustable magnetic field, an electric field or an optical field and the like under the microscale to realize the relative control on the degree of freedom of neutral atoms, vitreous-Einstein condensation, cold atom clouds or charged particles.

At present, the common atomic magneto-optical trap chip also has some problems to be solved urgently, for example, the depth of a generated magnetic field potential well is limited in the common plane mirror atomic magneto-optical trap chip, and the generated potential well is closer to the surface of the chip generally, so that the atomic trapping is difficult to realize in vacuum. In practical use, atoms need to be cooled and imprisoned by a macroscopic magneto-optical trap, and then are transferred and loaded into a micro-magnetic trap of an atom magneto-optical trap chip, so that the structure is difficult to realize;

with the development of the atomic magneto-optical trap chip technology, various atomic magneto-optical trap chip structures such as pyramid type and grating type have been proposed. Although the pyramid type atomic chip magneto-optical trap can simplify the system structure, the chip has high requirements on the processing of the structure, and the structure of the pyramid tip part is changed, so that the reflection characteristic is difficult to determine. The grating type atomic chip magneto-optical trap simplifies the optical path and system, but due to the difficulty in designing and processing the diffraction structure, the diffraction light result of ideal polarization is not easy to obtain.

Disclosure of Invention

The invention aims to further optimize and improve the structure and the performance of an atomic magneto-optical trap chip and provides the atomic magneto-optical trap chip which has the characteristics of simple structure, simple optical path, convenience in processing and stable performance.

The invention includes silicon wafers that are square sheets of polycrystalline or single crystal silicon material.

A reflection cavity and a three-dimensional magnetic field coil are arranged on the silicon wafer;

the reflecting cavity is a segment-shaped groove which is formed in the center of the top surface of the silicon wafer downwards;

the three-dimensional magnetic field coil comprises an upper magnetic field coil group embedded on the top surface of the silicon wafer and a lower magnetic field coil group embedded on the bottom surface of the silicon wafer.

The upper magnetic field coil group comprises four elliptical metal rings uniformly distributed around the reflecting cavity, and the elliptical metal rings are provided with openings relative to the far end of the reflecting cavity to form four symmetrically-arranged open elliptical metal coils.

The lower magnetic field coil group comprises two metal circular rings concentric with the reflection cavity, wherein the projection of the inner ring is in the minimum enclosing space range of the four elliptical metal rings, and the inner metal circular ring and the outer metal circular ring are provided with openings at the same angle to form two open circular metal coils concentrically arranged.

The invention also aims to provide a processing method of the atomic magneto-optical trap chip.

The method comprises the following specific steps:

selecting a conventional silicon crystal material which can be processed by a micro-nano processing technology as a sample crystal, and cleaning; the silicon crystal material is polysilicon or monocrystalline silicon;

respectively depositing corrosion-resistant protective layers with the thickness of 200 nm-350 nm on the two surfaces of the sample crystal by using a chemical deposition method;

step (3) according to the design, a circular ring is engraved in the center of the corrosion-resistant protective layer on one surface by a photoetching method;

removing the corrosion-resistant protective layer in the circular ring by using an ion beam etching method to expose the sample crystal and form a circular etching groove;

step (5), immersing the sample crystal with the etching groove into an HNA solution, wherein the HNA solution corrodes the sample crystal in a same manner to form a segment-shaped cambered groove;

taking out a sample crystal with a cambered surface groove, putting the sample crystal into an ICP etching machine, wherein the spherical crown surface of the cambered surface groove is SF₆Polishing by using a plasma etching method in the atmosphere;

step (7), immersing the sample crystal into selective corrosive liquid of a material of the corrosion-resistant protective layer, and removing the corrosion-resistant protective layers on the two sides;

step (8) etching four elliptical annular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed upper magnetic field coil group on the surface of the structural original with the cambered surface groove, and reserving photoresist; then preparing metal lines on the elliptical annular groove by using a metal sputtering method, and stripping photoresist to obtain an upper magnetic field coil group for generating a magnetic trap;

step (9) etching two concentric circular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed lower magnetic field coil group on the other surface of the structural original, and reserving photoresist; and then preparing metal lines on the circular grooves by using a metal sputtering method, and stripping photoresist to obtain a lower magnetic field coil group for generating the magnetic traps.

The optical reflection cavity structure adopts the spherical crown structure with uniform reflection characteristics, has the characteristic of high optical reflection efficiency, and has the metal lead structure capable of generating the high magnetic field gradient three-dimensional magnetic trap at the periphery of the reflection cavity and the bottom of the magneto-optical trap chip, so that the optical reflection cavity structure can be used for atom confinement cooling in vacuum. The invention utilizes the direct integration method of the chip magnetic field wire in the chip structure, so that the structure has the characteristic of good integration level of the magnetic field coil; the whole device can adopt a mature micro-nano chip processing and manufacturing process, has the advantage of simple processing, and the prepared device has the characteristic of stable working performance.

Drawings

FIG. 1 is a schematic diagram of a top surface structure of a chip according to the present invention;

FIG. 2 is a schematic diagram of a bottom structure of a chip according to the present invention;

FIG. 3 is a sectional view taken along line A-A of FIG. 1;

FIG. 4 is a schematic diagram of a chip manufacturing process according to the present invention.

Detailed Description

The present invention is described in detail below with reference to the attached drawings, and it should be noted that the described embodiments are only for understanding the present invention and do not have any limiting effect.

As shown in fig. 1, 2 and 3, an atomic magneto-optical trap chip includes a silicon wafer (1), and a reflective cavity (2) and a three-dimensional magnetic field coil disposed on the silicon wafer.

The silicon wafer (1) is a square sheet of polycrystalline silicon or monocrystalline silicon material. The center of the top surface of the silicon wafer (1) is provided with a segment-shaped groove downwards to form a reflecting cavity (2).

The three-dimensional magnetic field coil comprises an upper magnetic field coil group embedded on the top surface of the silicon wafer and a lower magnetic field coil group embedded on the bottom surface of the silicon wafer. The upper magnetic field coil group is composed of four elliptical metal rings (3) uniformly distributed around the reflection cavity (2), and the far ends of the elliptical metal rings (3) relative to the reflection cavity (2) are provided with openings to form four symmetrically-arranged open elliptical metal coils. The lower magnetic field coil group is composed of two metal circular rings (4) concentric with the reflecting cavity (2), wherein the projection of the inner ring is in the range of the minimum enclosed space of the four elliptical metal rings (3) (the range of the dotted line in figure 1). The inner and outer metal rings have openings at the same angle to form two concentrically arranged open circular metal coils.

The atomic magneto-optical trap chip processing method is shown in fig. 4:

s1, selecting a square silicon crystal material with the thickness of 2mm and the side length of 3cm as a sample crystal (1); the silicon crystal material is polysilicon or monocrystalline silicon;

s2, depositing silicon nitride with the thickness of 250nm on the surfaces of two surfaces of the sample crystal by using a chemical deposition (PECVD) method to serve as a subsequent anti-corrosion protective layer (5);

s3, according to design, a circular ring (6) is engraved in the center of the anti-corrosion protective layer (5) on one surface through a photoetching method;

s4, removing the anti-corrosion protective layer in the circular ring by using an ion beam etching method to expose the sample crystal (1) and form a circular etching groove (7);

s5, immersing the sample crystal with the etching groove into an HNA solution (8), wherein the HNA solution corrodes the sample crystal in a same manner to form a segment-shaped cambered surface groove; the HNA solution is a mixed solution of hydrofluoric acid, nitric acid and acetic acid according to the proportion of 2:5: 2;

s6, taking out the sample crystal with the cambered surface groove, putting the sample crystal into an ICP etching machine, wherein the spherical crown surface (9) of the cambered surface groove is positioned on SF₆Polishing by using a plasma etching method in the atmosphere to reduce the roughness of the spherical crown surface;

s7, immersing the sample crystal into selective corrosive liquid of silicon nitride, and removing the two anti-corrosion protective layers to obtain a structural element with a reflecting cavity (2); the selective corrosive liquid only corrodes the silicon nitride material, and can not corrode other materials;

s8, etching four elliptical annular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed upper magnetic field coil group on the surface of the structural original with the cambered surface groove, and reserving photoresist; then preparing metal lines on the elliptical annular groove by using a metal sputtering method, and stripping photoresist to obtain an upper magnetic field coil group for generating a magnetic trap;

s9, etching two concentric circular grooves with notches on the upper surface of the structural original by utilizing a photoetching method according to the shape of the designed lower magnetic field coil group on the other surface of the structural original, and reserving photoresist; and then preparing metal lines on the circular grooves by using a metal sputtering method, and stripping photoresist to obtain a lower magnetic field coil group for generating the magnetic traps.

The use method of the atomic magneto-optical trap chip comprises the following steps:

combining the prepared magneto-optical trap chip with a known packaging method, and respectively taking one end of an opening of each oval metal coil in an upper magnetic field coil group of the prepared atomic magneto-optical trap chip as a positive electrode to be connected with current, wherein the current directions of the four oval metal coils are the same and are clockwise or counterclockwise; one end of an opening of each circular metal coil in the lower magnetic field coil group is used as a positive electrode to be connected with current, and the current directions of the two circular metal coils are the same and are in a counterclockwise direction or a clockwise direction; the current directions of the upper and lower magnetic field coil groups are opposite. And finally forming a magnetic potential well with a certain depth of the potential well, and forming the magneto-optical well for trapping atoms by matching the circularly polarized laser with the magnetic potential well, wherein the circularly polarized laser is opposite to the reflecting cavity.