DE102020212151A1 - Method for manufacturing a vapor cell, in particular for an NMR gyroscope, and a vapor cell, in particular for an NMR gyroscope - Google Patents

Abstract

In order to provide a method for producing a vapor cell, in particular for an NMR gyroscope, which is inexpensive, suitable for mass production and scalable, a method (100) for producing a vapor cell (10), in particular for an NMR gyroscope, is proposed, comprising the Steps: - providing a first wafer (11), - arranging a second wafer (13) on the first wafer (11), the second wafer (13) having openings (17), the openings (17) of the second wafer ( 13) are covered on an underside (18) by the first wafer (11) and form cavities (19), - arranging a spacer (27) on the second wafer (13), - arranging a third, flexible wafer (23). the spacer (21), so that the third wafer (23) is arranged at a distance above the second wafer (13), forming a gap (25), the cavities (19) being fluidically connected to one another via the gap (25). ,- Filling the cavities (19) with a gas (33), - pressing the third wafer (23) against the second wafer (13) so that the gap (25) is closed at least in the area of the cavities (19), - connecting the third wafer (23) to the second wafers (13).

Description

State of the art

The present invention relates to a method for manufacturing a vapor cell, particularly for an NMR gyroscope. Furthermore, the present invention relates to a vapor cell, in particular for an NMR gyroscope.

Technological background

NMR (Nuclear Magnetic Resonance) gyroscopes offer particular advantages over MEMS (Micro Electro Mechanical Systems) gyroscopes. For example, NMR gyroscopes have up to 50 times better bias-drift stability. However, as part of the further development of NMR gyroscopes, major challenges have to be overcome. The production of the isotopically pure gases required, for example ¹²⁹ Xe and ¹³¹ Xe, is associated with very high costs. Further challenges arise in miniaturizing the magnetic shielding and limiting the power consumption of NMR gyroscopes.

The vapor cell, which contains the atoms, is the heart of an NMR gyroscope and presents a particular packaging challenge. The vapor cell must not react with the atoms inside the vapor cell and must allow access for light to and from the atoms. It must also withstand high temperatures, must not be magnetic and must also be permanently hermetically sealed. A large-scale implementation of NMR gyroscopes, for example in automotive engineering, depends heavily on the final costs of the vapor cell.

Disclosure of Invention

The present invention is based on the object of providing a method for producing a vapor cell, in particular for an NMR gyroscope, which is inexpensive, suitable for large-scale production and scalable.

• - Bereitstellen eines ersten Wafers,
• - Anordnen eines zweiten Wafers auf dem ersten Wafer, wobei der zweite Wafer Durchbrüche aufweist, wobei die Durchbrüche des zweiten Wafers an einer Unterseite von dem ersten Wafer abgedeckt werden und Kavitäten bilden,
• - Anordnen eines Abstandhalters auf dem zweiten Wafer,
• - Anordnen eines dritten, flexiblen Wafers auf dem Abstandshalter, sodass der dritte Wafer unter Ausbildung eines Spalts in einem Abstand oberhalb des zweiten Wafers angeordnet ist, wobei die Kavitäten über den Spalt fluidisch miteinander in Verbindung stehen,
• - Befüllen der Kavitäten mit einem Gas,
• - Anpressen des dritten Wafers an den zweiten Wafer, sodass der Spalt zumindest im Bereich der Kavitäten geschlossen wird,
• - Verbinden des dritten Wafers mit dem zweiten Wafer.

In order to achieve the object on which the invention is based, a method for producing a vapor cell, in particular for an NMR gyroscope, is proposed, the method having the steps

• - providing a first wafer,
• - arranging a second wafer on the first wafer, the second wafer having openings, the openings of the second wafer being covered on a lower side by the first wafer and forming cavities,
• - placing a spacer on the second wafer,
• - arranging a third, flexible wafer on the spacer, so that the third wafer is arranged at a distance above the second wafer, forming a gap, the cavities being fluidically connected to one another via the gap,
• - filling the cavities with a gas,
• - pressing the third wafer onto the second wafer so that the gap is closed at least in the area of the cavities,
• - Bonding the third wafer to the second wafer.

Within the scope of the present invention, a wafer is referred to as a disk that is, for example, circular or square and, in particular, thin. The wafers can consist of suitable glasses, silicon or other suitable materials.

When arranging the second wafer on the first wafer, the first wafer bears against an underside of the second wafer from below, so that the openings, in particular continuous ones, in the second wafer are covered and in particular closed by the first wafer underneath. The openings covered from below form the cavities for receiving a gas, in particular isotopically pure ¹²⁹ Xe and ¹³¹ Xe.

The openings in the second wafer are preferably in the form of continuous openings and can also be referred to as holes or bores or recesses. The second wafer particularly preferably has a multiplicity of such openings, so that a multiplicity of cavities are formed by arranging the second wafer on the first wafer.

The third flexible wafer is preferably thinner than the first and/or the second wafer and is arranged on the spacer in such a way that the underside of the third wafer is at a distance from the top side of the second wafer, forming a gap. The cavities are in fluid communication with one another via the gap, so that a gas can flow through the gap from one cavity into the other.

A particular advantage of the invention is that the gas, in particular isotopically pure ¹²⁹ Xe or ¹³¹ Xe, which is associated with high production costs, can be introduced very precisely and with low filling losses into all cavities simultaneously and thus efficiently. This filling method contributes greatly to scalability of the steam cells with minimal manufacturing costs.

To close the individual cavities, the third wafer is pressed or pressed against the second wafer, the flexibility of the third wafer being used. The underside of the third wafer comes to rest on the top side of the second wafer, at least in the area of the cavities, as a result of which the gap is closed at least in the area of the cavities. The third wafer is then connected to the second wafer, so that the individual cavities are fluidically isolated from one another and sealed in a gas-tight manner.

The individual cavities can then be separated from one another. Each of the gas-filled and sealed cavities then forms a vapor cell, in particular for an NMR gyroscope.

A particular advantage of the invention is the utilization of the flexibility of the third wafer when sealing the cavities. The third wafer can first be arranged on the spacer and above the second wafer in such a way that all the cavities can be filled with a gas in one step via the gap. In order to close the cavities, the third wafer can be pressed or pushed against the second wafer at least in the area of the cavities, so that all cavities are closed at the same time. The spacer does not need to be removed for this. The manufacturing cost can thus be reduced. In addition, the process is scalable for large series.

The vapor cell is particularly suitable for use in a Nuclear Magnetic Resonance Gyroscope (NMR gyroscope).

The first wafer and/or the second wafer and/or the third wafer can be structured wafers.

The gas is preferred, especially isotopically pure, ¹²⁹ Xe and ¹³¹ Xe.

Advantageously, it can be provided that the first wafer is a translucent wafer, preferably a glass wafer, and/or that the first wafer has at least two holes for the passage of a gas.

A translucent first wafer allows access of light from and to the atoms of the gas located in the cavities.

Another advantage is that the second wafer is an Si wafer and/or that the second wafer has at least two holes for conducting a gas, the holes in the second wafer preferably being aligned with the holes in the first wafer, so that at least one inlet channel for a gas and at least one outlet channel for the gas is formed.

The holes in the first wafer and/or the second wafer run in particular continuously from an upper side to an underside of the first wafer and/or the second wafer.

The second wafer is preferably an Si wafer and therefore hardly reacts chemically or not at all with the atoms of the gas fed into the cavities. A silicon wafer can also withstand high temperatures.

If the holes in the second wafer are aligned with the holes in the first wafer, the aligned holes form at least one inlet channel and one outlet channel. Thus, a gas can be introduced from the underside of the first wafer through one of the holes in the first wafer and through a hole in the second wafer aligned with the hole in the first wafer, ie through the inlet channel, into the gap between the second wafer and the third wafer will.

The introduced gas can then spread through the gap into all cavities. Gas previously located in the gap can be conducted out through the outlet channel formed from a hole in the first wafer and a hole in the second wafer arranged in alignment with the hole in the first wafer. In particular, the gap can be evacuated.

The at least one inlet channel and the at least one outlet channel preferably end in the gap between the second wafer and the third wafer. The gap is also preferably delimited on the peripheral side by the spacer.

With a further advantage it is provided that the third wafer is a translucent wafer, preferably a glass wafer.

Since the first wafer and the third wafer are arranged below and above the second wafer, access of light to and from the atoms arranged in the cavities can be allowed through the first light-transmissive wafer and the third light-transmissive wafer.

Provision is advantageously made for the second wafer to be connected to the first wafer by an anodic bonding method.

With a further advantage, it can be provided that the spacer is ring-shaped and/or that the spacer is arranged at the edge on the second wafer and/or that the spacer consists of a plastic, in particular a polymer. Alternatively or additionally, the spacer can be produced on the second wafer by selectively grinding the second wafer. A spacer at the edge remains.

By arranging the spacer on the edge, and more preferably circumferentially, on the second wafer, the third wafer can be arranged at a small distance from the top side of the second wafer by arranging the third wafer on the spacer, so that between the second wafer and the third Wafer forms a gap. At the edge, the gap is delimited by the spacer. All of the cavities can be filled at the same time by introducing a gas through the inlet channel into the gap.

With a further advantage, provision can be made for rubidium, more preferably in powder form, to be filled into the cavities, preferably before the arrangement of the third wafer on the spacer.

With a further advantage, it can be provided that the third wafer is connected to the spacer, so that the gap is closed in a gas-tight manner at the edge.

Provision is preferably made for the first wafer to be arranged on a clamping device, the clamping device having at least one supply channel for a gas and at least one return channel for a gas, the supply channel fluidically connected to the inlet channel, which more preferably consists of the aligned holes of the first Wafer and the second wafer is formed, is connected, and wherein the return line channel is fluidly connected to the outlet channel, which is more preferably formed by further aligned holes of the first wafer and the second wafer is formed.

The clamping device can also be referred to as a "bonding chuck".

The supply channel and the return channel are formed in particular inside the clamping device.

A gas can be conducted through the supply channel to the inlet channel formed by the aligned holes of the first wafer and the second wafer and further into the gap between the second wafer and the third wafer. Accordingly, a gas from the gap between the second wafer and the third wafer can be guided and discharged into the return passage in the chuck through the exhaust passage formed of the other aligned holes of the first wafer and the second wafer.

With a further advantage, it is provided that the clamping device has a fastening means, in particular channels for a vacuum system.

With the fastening means, a secure positioning and alignment of the supply channel and the return channel of the clamping device can be ensured with respect to the inlet channel and the outlet channel in the first wafer and the second wafer.

If the fastening means includes channels for a vacuum system, these are open in particular in the direction of the underside of the first wafer arranged on the clamping device, so that the first wafer can be fixed to the clamping device by generating a vacuum.

It is preferably provided that the method includes the step of filling the cavities with a gas, preferably with a Xe isotope, more preferably with ¹²⁹ Xe and ¹³¹ Xe, through the at least one supply channel of the clamping device and the aligned holes of the first wafer and the second wafer formed at least one inlet channel.

The step of placing the first wafer on the chuck may be the first step of the method. Furthermore, the step of arranging the first wafer on the second wafer can take place at any time before the cavities are filled with a gas.

The third wafer is preferably pressed onto the second wafer by means of a chuck.

Provision is also preferably made for the third wafer to be connected to the second wafer by an anodic bonding method.

By pressing the third wafer against the second wafer, the third wafer rests on the upper side of the second wafer and closes all of the cavities formed in the second wafer. By subsequently connecting the third wafer to the second wafer, for example using an anodic bonding method, the cavities are sealed off in a hermetically gas-tight manner.

In a further method step, the clamping device is preferably removed.

The step of cutting the interconnected wafers, in particular the first wafer, the second wafer and the third wafer, by means of a wafer dicing method is preferably provided.

Thus, the block formed from the first wafer, the second wafer and the third wafer is trimmed so that the cavities filled with gas are separated or separated from one another.

Each of the individual, separated cavities can form a vapor cell, in particular for an NMR gyroscope.

A further solution to the problem on which the invention is based consists in providing a vapor cell, in particular for an NMR gyroscope, which can be produced or produced using a method described above.

Yet another solution to the problem underlying the invention consists in providing an NMR gyroscope with a vapor cell as described above.

• 1 einen ersten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 2 einen zweiten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 3 einen dritten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 4 einen vierten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 5 einen fünften Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 6 einen sechsten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 7 einen siebten Schritt eines Verfahrens zur Herstellung einer Dampfzelle,
• 8 einen achten Schritt eines Verfahrens zur Herstellung einer Dampfzelle, und
• 9 einen neunten Schritt eines Verfahrens zur Herstellung einer Dampfzelle.

The invention is explained in more detail below with reference to the accompanying figures. Show it

• 1 a first step of a method for manufacturing a vapor cell,
• 2 a second step of a method for manufacturing a vapor cell,
• 3 a third step of a method for manufacturing a vapor cell,
• 4 a fourth step of a method for manufacturing a vapor cell,
• 5 a fifth step of a method for manufacturing a vapor cell,
• 6 a sixth step of a method for manufacturing a vapor cell,
• 7 a seventh step of a method for manufacturing a vapor cell,
• 8th an eighth step of a method of manufacturing a vapor cell, and
• 9 a ninth step of a method of manufacturing a vapor cell.

In the 1 until 9 the steps of a method 100 for manufacturing a vapor cell 10 ( 9 ), in particular for an NMR gyroscope.

In a first step of the process 1 a first wafer 11, which is designed as a structured glass wafer 11a, is provided. The structured glass wafer 11a has two holes 12 at the edge.

In a second process step 2 a second wafer 13, which is in the form of a Si wafer 13a, is arranged on the first wafer 11. The Si wafer 13a also has at least two holes 14 on the edge, which are aligned with the holes 12 in the first wafer 11 .

Due to the alignment, the holes 12, 14 form at least one inlet channel 15 for a gas and at least one outlet channel 16 for a gas.

The second wafer 13 also has openings 17 which, when the second wafer 13 is arranged on the first wafer 11 , are closed by the underside 18 of the first wafer 11 and form cavities 19 . The second wafer 13 is attached to the first wafer 11 by means of an anodic bonding method.

In a further third step after 3 is in the formed in the previous step cavities 19 a quantity, particularly preferably powdery rubidium 20, filled.

In a fourth step after 4 an annular spacer 21 is arranged at the edge on the upper side 22 of the second wafer 13 . The spacer 21 is formed in particular from a polymer. Alternatively, the spacer can already be produced during the production of the second wafer 13 by selective grinding.

On the spacer 21 is in a fifth step after 5 a flexible, in particular thin, third wafer 23 is arranged, which is also designed as a glass wafer 23a. The third wafer 23 is arranged and fastened on the spacer 21 in such a way that a gap 25 is formed between the upper side 22 of the second wafer 13 and the lower side 24 of the third wafer 23 . The individual cavities 19 are in fluid communication with one another via the gap 25 . The gap 25 is delimited by the second wafer 13 , the third wafer 23 and the spacer 21 , the inlet channel 15 and the outlet channel 16 opening into the gap 25 .

In a sixth step after 6 the block 26 comprising the first wafer 11, the second wafer 13, the spacer 21 and the third wafer 23 is presented on a chuck direction 27 arranged. The clamping device 27 has a feed channel 28 for a gas and a return channel 29 for a gas. In this case, the feed channel 28 is arranged in such a way that it is fluidically connected to the inlet channel 15 .

The return line duct 29 is in fluid communication with the outlet duct 16. The clamping device 27 also includes a fastening means 30, which has ducts 31 for a vacuum system, not shown in detail. The channels 31 are open to the underside 32 of the first wafer 11 arranged on the clamping device 27 . By generating a vacuum in the channels 31, the first wafer 11 together with the second wafer 13, the spacer 21 and the third wafer 23 can be fixed on the clamping device 27.

In a seventh step after 7 the gap 25 and the cavities 19 are first evacuated via the outlet channel 16 and the return line channel 29 . A gas 33 , for example isotopically pure ¹²⁹ Xe and ¹³¹ Xe, is then conducted through the feed channel 28 and the inlet channel 15 into the gap 25 , so that the cavities 19 are filled with the gas 33 .

In an eighth process step 8th the flexible third wafer 23 is pressed against the upper side 22 of the second wafer 13 by means of a chuck 34, so that the gap 25 in the region of the cavities 19 is closed. The cavities 19 are no longer fluidly connected to one another. In this case, the flexibility of the third wafer 23 is used in particular.

Subsequently, in a ninth method step 9 the jig 27 removed. Furthermore, the individual cavities 19 are separated from one another using a wafer dicing method. The separate cavities 19 each form individual vapor cells 10, in particular for an NMR gyroscope.

Claims (10)

Method (100) for producing a vapor cell (10), in particular for an NMR gyroscope, comprising the steps: - providing a first wafer (11), - Arranging a second wafer (13) on the first wafer (11), the second wafer (13) having openings (17), the openings (17) of the second wafer (13) on an underside (18) of the first Wafer (11) are covered and form cavities (19), - arranging a spacer (27) on the second wafer (13), - Arranging a third, flexible wafer (23) on the spacer (21) so that the third wafer (23) is arranged at a distance above the second wafer (13) to form a gap (25), the cavities (19) are in fluid communication with one another via the gap (25), - filling the cavities (19) with a gas (33), - pressing the third wafer (23) onto the second wafer (13), so that the gap (25) is closed at least in the area of the cavities (19), - Connecting the third wafer (23) to the second wafer (13). Method (100) according to claim 1 , wherein the first wafer (11) is a translucent wafer, preferably a glass wafer (IIa), and/or wherein the first wafer (11) has at least two holes (12) for the passage of a gas (33), and/ or wherein the second wafer (13) is a Si wafer (13a), and/or wherein the second wafer (13) has at least two holes (14) for the passage of a gas (33), the holes (14) of the second wafer (13) aligned with the holes (12) of the first wafer (11), so that at least one inlet channel (15) for a gas (33) and at least one outlet channel (16) for a gas (33) are formed . Method (100) according to claim 1 or 2 , wherein the third wafer (23) is a translucent wafer, preferably a glass wafer (23a), and/or wherein the second wafer (13) is connected to the first wafer (11) by an anodic bonding method. The method (100) according to any one of the preceding claims, wherein the spacer (21) is ring-shaped, and/or wherein the spacer (21) is arranged at the edge on the second wafer (13), and/or wherein the spacer (21) consists of consists of a plastic, in particular a polymer, and/or wherein the spacer (21) is produced by selective grinding of the second wafer (13). Method (100) according to one of the preceding claims, wherein the third wafer (23) is connected to the spacer (21) so that the gap (25) is closed in a gas-tight manner at the edge. Method (100) according to any one of claims 2 until 5 , further comprising the step - arranging the first wafer (11) on a clamping device (27), wherein the clamping device (27) has at least one supply channel (28) for a gas (33) and at least one return channel (29) for a gas (33 ) has, wherein the supply line channel (28) is fluidically connected to the inlet channel (15), and wherein the return line channel (29) is fluidly connected to the outlet channel (16), it being preferably provided that the clamping device (27) has fastening means (30), in particular channels (31) for a vacuum system. Method (100) according to claim 6 , further comprising the step of - filling the cavities (19) with a gas (33), preferably with a Xe isotope, through the at least one supply channel (28) of the clamping device (27) and through the aligned holes (12, 14 ) of the first wafer (11) and the second wafer (13) formed at least one inlet channel (15). Method (100) according to one of the preceding claims, wherein the pressing of the third wafer (23) onto the second wafer (13) takes place by means of a chuck (34), and/or wherein the third wafer (23) is connected to the second wafer (13 ) is connected by an anodic bonding process. Method (100) according to one of the preceding claims, comprising cutting the interconnected wafers (11, 13, 23), in particular the first wafer (11), the second wafer (13) and the third wafer (23), by means of a wafer -Dicing procedure. Vapor cell (10), in particular for an NMR gyroscope, which can be produced or produced using a method (100) according to one of Claims 1 until 9 .

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