Infrared emitter with glass cover

Abstract

Embodiments disclose infrared emitters with glass covers. An infrared emitter with a glass cover for emitting infrared radiation, comprising a package enclosing a cavity and a heating structure configured for emitting infrared radiation, wherein a first portion is transparent to infrared radiation and a second portion comprises a glass material, the heating structure arrangement being in the cavity between the first portion and the second portion of the package.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to an emitter, e.g. an infrared source in combination with a glass cover. BACKGROUND

[0002] Sensing of environmental parameters such as noise, sound, temperature and gases is becoming more and more important within the mobile, home automation and automotive industry. Due to pollution and malfunction of certain devices, harmful gas concentrations can occur. Well-being is strongly influenced by air quality. Gas detection by cheap, always available and connected sensors is a topic of the near future.

[0003] For integrated circuits like MEMS, size and height can be aspects to consider - especially whether the chip should be implemented in a mobile device like a smartphone. In addition, for MEMS solutions, cost can be considered.

[0004] Therefore, it is desirable to provide an IR emitter, wherein the size, height of the emitter filter package is reduced, is robust, reliable and at the same time producible at low cost. SUMMARY

[0005] According to one embodiment, the emitter can comprise a package enclosing a cavity, wherein a first portion of the package, i.e. a silicon substrate, can be transparent to infrared radiation and a second portion of the package, i.e. a non-transparent substrate or a non-transparent substrate, can comprise a glass material. The emitter can further comprise a heating structure, i.e. an IR emitter configured for emitting infrared radiation, wherein the heating structure can be arranged in the cavity between the first portion of the package and the second portion of the package.

[0006] According to a further embodiment, a method for manufacturing an emitter can comprise providing a heating structure; providing a first portion of a package transparent to infrared radiation; and providing a second portion of the package comprising a glass material; such that the heating structure is arranged in a cavity enclosed by the package between the first portion of the package and the second portion of the package; such that the heating structure is configured for emitting infrared radiation.

[0007] Further embodiments are described in the dependent claims. BRIEF DESCRIPTION OF DRAWINGS

[0008] In the following, embodiments of the present disclosure are described in more detail with reference to the accompanying drawings, in which:

[0009] Figure 1 A schematic cross-sectional view of a two-part package enclosing a cavity according to one embodiment is shown;

[0010] Figure 2A schematic cross-sectional view showing a first portion of a package with a typical IR emitter structure with a filter layer is shown;

[0011] Figure 3 A schematic cross-sectional view showing a first portion of a package with a typical IR emitter structure with a filter layer and a glass layer is shown;

[0012] Figure 4 A laser-induced glass damage is shown;

[0013] Figure 5 A schematic cross-sectional view of a thin glass layer is shown;

[0014] Figure 6 A schematic cross-sectional view of a glass layer with metallization is shown;

[0015] Figure 7 A schematic cross-sectional view of a glass layer with a through glass via (TGV) and wet etching of the mask is shown;

[0016] Figure 8 A schematic cross-sectional view of a glass layer with a through glass via (TGV) and metallization is shown;

[0017] Figure 9 A schematic cross-sectional view of a glass layer with an open mask layer is shown;

[0018] Figure 10 A schematic cross-sectional view of a glass layer with a recess is shown;

[0019] Figure 11 A schematic cross-sectional view of a hermetically sealed die bond package is shown; and

[0020] Figure 12 A base wavelength diagram is shown. DETAILED DESCRIPTION

[0021] In the following description, a package is a housing for an electronic system or device (e.g., a semiconductor device, a printed circuit board (PCB), an integrated circuit (IC), and a thick film device) for enclosing or protecting against mechanical damage, cooling, radio frequency, noise, emissions, and electrostatic discharge. Product safety standards can influence or dictate certain features of consumer products, for example, case temperature or grounding of exposed metal components. Low volume manufactured prototypes or industrial equipment can use standardized, market-available enclosures, such as a card cage or a pre-fabricated box. Mass market consumer devices can have highly specialized packaging to increase appeal to consumers.

[0022] Many electronic products require the manufacture of large quantities of low cost components such as housings and covers by techniques such as injection molding, die casting and investment casting. The design of these products depends on the production method and requires careful consideration of dimensions and tolerances as well as tool design. Certain components can be manufactured by specialized processes such as plaster-sand mold casting of metal housings, wafer level processing or inter-wafer bonding processing, which are explained in more detail in this disclosure.

[0023] In the design of electronic products, it is essential to perform analyses to estimate things such as the maximum temperature of components, structural resonant frequencies, and dynamic stresses and deflections under worst case environments. Such knowledge is important to prevent immediate or premature electronic product failure.

[0024] Before the embodiments are discussed in further detail using the accompanying drawings, it should be noted that in the drawings and specification same elements and elements having same functions and / or same technical or physical effects are generally designated with the same reference numerals or identified with the same names so that the description shown for these elements and their functions can be mutually interchangeable or can be applied to each other in different embodiments. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that the embodiments can be practiced without these specific details. In other instances, well-known methods have not been described in detail in order to avoid unnecessarily obscuring the present embodiments. Also, unless otherwise specifically noted, features of different embodiments described below can be combined with each other, unless specifically noted otherwise. The specific embodiments discussed merely illustrate specific ways of making and using the present concepts, and do not limit the scope of the embodiments.

[0025] The IR emitter and filter can be placed as separate devices and separately in a common package. For example, the filter can be placed directly on the emitter, but they can also be placed on-chip. This solution can take up a lot of space, e.g. on a chip, a PCB (printed circuit board) or a wafer. For some applications, such a solution can be too large in height and size and thus, e.g. not useful in mobile devices. Therefore, some embodiments relate to an IR emitter and an IR filter which can be implemented in a single package, e.g. together with additional other chips on a PCB or a wafer.

[0026] It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements can be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other terms of description of the relationships between elements will be construed in a like fashion (e.g., “between,” relative to “directly between,” “adjacent,” relative to “directly adjacent,” and “on,” relative to “directly on,” etc.).

[0027] Embodiments described herein can relate to an emitter. Such an emitter can be configured for emitting electromagnetic radiation, which can comprise a specific wavelength range. Such electromagnetic radiation can be used in conjunction with further structures in which a sensor forms an embodiment of the present disclosure. As a non-limiting example only, such an emitter can be used in sensor applications, such as a photoacoustic gas sensor, which uses electromagnetic radiation to excite gas molecules in order to allow determining the presence and / or concentration of one or more types of gas based on the generated excitation. Such a sensor can for example operate by using electromagnetic radiation comprising at least a part of the infrared (IR) spectrum. In order to limit the emitted spectrum, the emitter can be adapted in view of generating electromagnetic radiation in a desired wavelength spectrum and / or can comprise or can be combined with a filter structure which allows excluding or attenuating undesired wavelength ranges.

[0028] Although embodiments are described in connection with an IR emitter, the present disclosure is not limited thereto. That is, embodiments can also relate to different wavelength ranges.

[0029] Figure 1 A schematic cross-sectional view of an emitter 10 according to one embodiment is shown. According to one embodiment, the emitter 10 can be a microelectromechanical system (MEMS). The emitter 10 can comprise a package 12 enclosing a cavity 14. The package 12 can comprise a first portion 16 of the package 12 which is transparent for at least a part of the radiation, which can be understood as infrared radiation 13. The infrared radiation 13 can comprise a wavelength range between 0.7 pm and 30 pm, for example. The emitted wavelength radiation 13 can comprise at least a part of this wavelength range, not excluding that additional wavelengths below 0.7 pm or above 30 pm are emitted thereby. In connection with the present embodiment, the emitted radiation 13 can be considered as radiation having a desired wavelength range from a possibly larger wavelength range which is being generated.

[0030] Transparent can be understood as allowing a passage of at least 50%, at least 70% or at least 90% (e.g. 95%) of the material for at least the desired wavelength range. For example, a semiconductor material can be transparent for the infrared radiation 13. Further, the package 12 can comprise a second portion 18 of the package 12, the second portion 18 comprising a glass material.

[0031] That is, the first portion 16 of the package 12 can comprise a semiconductor material, for example, comprising a silicon material, a gallium arsenide material, and / or a different semiconductor base material. The semiconductor material can be a doped or an undoped semiconductor material. Alternatively or in addition, the first portion 16 can comprise a metallic material comprising one or more metallic materials, which material, the obtained combination or alloy, respectively, is transparent for the infrared radiation 13 of the desired portion. The first portion 16 of the package 12 can comprise a filter structure 25, which is transparent for the infrared radiation 13. Alternatively, the filter structure 25 can be arranged at a different position or the emitter 10 can be implemented without the filter structure 25.

[0032] The second portion 18 of the package 12 can comprise a glass material. In the present specification, the glass material can be referred to as a glass base 32. The glass base 32 can be obtained in a thin structure while providing a high robustness. In addition, the topology of the glass structure can be generated with a high precision, thereby allowing to obtain a high quality emitter. The glass base 32 can be at least partially non-transparent or even opaque or used as a damping structure for at least a portion of the infrared radiation 13, for which the first portion 16 is transparent. This can allow to implement a directional structure, i.e. to provide a hole structure within the emitter 10 by the material selected for the second portion 18 of the package 12, while avoiding additional elements and while utilizing the other advantages provided. The glass base 32 can comprise a material such as N-BK7 as shown. The wavelength range of N-BK7 represents most of the materials for visible wavelengths such as B270, N-SF11 or Figure 12

[0033] The heating structure 15 can be configured for emitting the infrared radiation 13 comprising an infrared wavelength range between 0.7 pm and 30 pm. The heating structure 15 is arranged in the cavity 14 between the first portion 16 of the package 12 and the second portion 18 of the package 12. That is, the package 12 can house the heating structure 15.

[0034] ​One aspect of the present disclosure relates to a gas sensor, which is or comprises, among others, a photoacoustic sensor comprising an IR emitter 10 in a cavity 14. The photoacoustic sensor can be configured to detect a gas in an environment according to the photoacoustic principle. Thus, the emitter 10 can be configured to emit IR radiation 13 in a predetermined wavelength spectrum into the measurement cavity. The specific wavelength of the emitted IR radiation 13 can be selected based on the gas to be detected, i.e. the so-called target gas. The emitter 10 can be configured to emit the IR radiation 13 intermittently. During operation, the ambient gas within the measurement cavity, including the target gas, can absorb the emitted radiation 13 and, thus, the gas can intermittently heat up and cool down in reaction to the intermittently emitted IR radiation 13. This intermittent absorption of the gas within the measurement cavity and the associated heating and cooling can result in an alternating increase and decrease of the pressure within the measurement cavity. These pressure variations can be detected by an acoustic transducer, e.g. a MEMS microphone or a MEMS structure, which realizes a hingeable vibration and is connected to a membrane of the excited gas.

[0035] The amount of absorption of the emitted IR radiation 13 by the gas and the associated pressure variations within the measurement cavity can depend on the kind of gas within the measurement cavity and can vary with the respective target gas. Each target gas can comprise a characteristic absorption spectrum, i.e. each target gas can cause a characteristic pressure variation in response to the intermittently emitted IR radiation 13. Said characteristic absorption spectrum can also be referred to as a gas-specific fingerprint. Thus, the acoustic transducer can record a signal, which can be specific to the respective target gas, such that the signal generated by the acoustic transducer can thereby form the basis for detecting and identifying the respective target gas, e.g. by using a correspondingly adapted circuitry.

[0036] For example, a central processing unit (CPU), an integrated circuit (IC), an application-specific integrated circuit (ASIC), a microcontroller or a field-programmable gate array (FPGA) can be connected to the acoustic transducer and possibly to the emitter 10 to allow for a good synchronization.

[0037] Figure 2 A schematic cross-sectional view showing an implementation of the first portion 16 of the package 12 according to one embodiment is shown. The first portion 16 can realize or can comprise a plurality of layers. The first portion 16 can comprise a heating structure 15, a semiconductor substrate 22, a spacer layer 24 between the semiconductor substrate 22 and the heating structure 15, a filter structure 25 and a metallization structure 28. The semiconductor substrate 22 can comprise one or more semiconductor materials, e.g. silicon, gallium arsenide, gallium nitride and / or silicon carbide.

[0038] The substrate 22 can comprise a first main side and an opposite second main side. The first main side and / or the second main side can be parallel to an x / y plane based on an x-direction and a perpendicular y-direction, wherein a z-direction can be perpendicular to both the x-direction and the y-direction. The z-direction can be referred to as a depth direction, wherein depth should not be understood to limit the examples described herein to a particular direction in space.

[0039] The spacer layer 24 can comprise, for example, an electrically insulating material such as SiO2 and / or SiN. The spacer layer 24 can comprise at least one layer for maintaining a distance, e.g. a spacing or gap, arranged between the semiconductor substrate 22 and the heating structure 15. The space between the layers can be selected in a wide range based on other geometrical shapes of the device or application, for example. As a non-limiting example, the spacer layer 24 can cover a distance between 100 nm and 10 pm.

[0040] The first portion 16 of the package 12 can be part of the emitter 10. For example, the first portion 16 and the second portion 18 can form a stack, e.g. in an arrangement on top of each other, one on top of the other or stacked on top of each other. The cavity 14 can be housed or sealed between the first portion 16 and the second portion 18. That is, the first portion 16 of the package 12 can form an assembly of the emitter 10, but can be implemented separately or individually. To form the emitter 10, the filter structure 25 can comprise, for example, an infrared filter, an infrared filter stack or a filter chip and can be configured to selectively transmit at least a portion of the IR radiation 13, e.g. in a predetermined wavelength range.

[0041] According to one embodiment, the filter structure 25 can comprise a monolithically integrated filter layer. For example, the filter structure 25 can comprise one or more layers collectively providing filter properties in order to transmit at least a portion of a predetermined wavelength range, e.g. an infrared wavelength range or different portions of an infrared wavelength range. For example, the predetermined wavelength range can comprise wavelengths between 0.7 pm and 30 pm, between 0.9 pm and 20 pm or between 1 pm and 10 pm. The wavelength range can be adapted according to the target gas from the sensor behind the measurement cavity package of the photoacoustic sensor. For example, the measurement cavity can relate to a photoacoustic sensor containing a target gas, whereas the cavity 14 relates to an emitter in which the package 12 encloses the cavity 14.

[0042] According to an embodiment, the filter structure 25 can comprise a stack of one or more layers configured for filtering the IR radiation 13, e.g. in a predetermined wavelength range. Thereby, the at least one layer can provide for filtering the infrared radiation 13 to pass through the predetermined wavelength range. Optionally, the stack of layers can comprise a change of at least one property between the layers. The change can be implemented regularly or irregularly, and can, wherein, some embodiments provide for layers comprising a periodic change of at least one property. Exemplary properties can be a height, depth or width of the layers, while having the same or a varying layer material.

[0043] For example, the filter structure 25 can comprise at least two layers of the same or different material. According to an embodiment, the filter structure 25 can be arranged on a surface of the semiconductor substrate 22.

[0044] According to an embodiment, the filter structure 25 can be configured as at least partially reflecting an infrared wavelength range which can be impractical for gas sensing, such as a Bragg reflector. By reflecting a portion of wavelengths which can not be wanted while transmitting other wavelength ranges, a filtering with respect to a transmission direction through the filter structure 25 can be achieved.

[0045] According to an embodiment, the heating structure 15 can comprise an element generating heat, thereby providing an infrared radiation source. Such an element can be operated by electrical power, wherein an electrical loss can provide for the generation of heat. Although any possible infrared radiation source can be used, arranging a membrane structure can allow for efficiently and over a large area obtaining radiation. The membrane structure can comprise one or more vents 27 similar to an acoustic membrane or diaphragm. The membrane structure can be arranged at and / or on a surface of the heating structure 15 having the vents 27 forming a path from the first side 34 of the first portion 16 of the package 12 to the filter structure 25. The heating structure 15 configured for emitting the infrared radiation 13 can excite a motion of the membrane structure based on an asymmetric energy absorption of the infrared radiation in the first portion 16 and the second portion 18. An example of such a membrane structure can be a circular structure (e.g. a circle or circular membrane) or a diaphragm structure. Such a membrane structure can form, for example, similar to a membrane structure used in a MEMS microphone or a MEMS speaker.

[0046] The heating structure 15 can comprise a metallization structure 28 (e.g. copper, gold, silver, platinum, etc. configured as part of a metal-semiconductor junction) that is electrically conductive and configured for generating IR radiation 13 in response to an electrical current. According to one embodiment, the metallization structure 28 can comprise a pad or pads directly coupled on the heating structure 15 providing an electrical connection for the heating structure 15 in order to emit the infrared radiation 13. Further, the shape can comprise a ring shape, a square shape or a circular shape. Additionally, the metallization structure 28 coupling the heating structure 15 of the first portion 16 of the package 12 with the metallization structure 28 of the second portion 18 is arranged on a surface of the heating structure 15 facing the first side 34 of the first portion 16 of the package 12 in order to keep the vent hole 27 uncovered.

[0047] The heating structure 15 can be arranged on a surface of the first portion 16. The surface of the first portion 16 can be referred to as the first side 34 of the first portion 16. The side of the first portion 16 opposite to the first side 34 can be referred to as the second side 35 of the first portion 16. Accordingly, the semiconductor substrate 22 can be arranged on the second side 35 of the first portion 16. The heating structure 15 can be spaced apart from the semiconductor substrate by the spacer layer 24.

[0048] Figure 3 A schematic cross-sectional view of the first portion 16 of the package 12 and the second portion 18 of the package 12 comprising the glass substrate 32 is shown as Figure 2 The first portion 16 of the package 12 can be transparent for a first amount of a predetermined wavelength range. The second portion 18 can also be transparent for a second amount of the predetermined wavelength, which is lower compared to the first amount. Alternatively, the second portion 18 can be opaque for the predetermined wavelength range.

[0049] In order to form the second portion 18 from the glass substrate, an embodiment comprises forming at least one recess 53 in the glass substrate 32. The at least one recess 53 can be understood as a cavity or opening extending through a portion or the entire thickness of the glass material. Different recesses 53 can be formed equal or different with respect to depth or lateral extension. In order to generate the at least one recess 53, an embodiment comprises performing a subtractive and / or additive process such as material etching, material cutting, material jetting, material extrusion and / or polymerization. As an example, a possible process is described in Figure 4 In a later emitter 10, the heating structure 15 can be arranged between the filter structure 25 and the second portion 18. This allows the IR radiation 13 to pass through the filtered semiconductor substrate 22 while possibly being attenuated by the second portion 18. The surface of the glass substrate 32 facing the first side 34 of the first portion 16 can be referred to as the first side 36. Accordingly, the side opposite to the first side 36 of the second portion 18 can be referred to as the second side 37 of the second portion 18.

[0050] Figure 4 A schematic side view of a glass substrate 32 from which the second portion 18 of the emitter 10 according to the present embodiment can be obtained is shown. At least one laser beam 48 can be used to damage the glass substrate 32 in a recess region in which a subsequent recess 53 is intended to be obtained. The recess 53 can form a depression in the glass substrate 32 in order to partially reduce its thickness to a non-zero value. Optionally, the thickness can be reduced to a zero value in the recess 53, thereby providing a through-hole opening in the glass substrate 32. For example, a focus of the at least one laser beam 48 can be variably set to a point of the glass substrate 32 to change a structure of the glass substrate 32 at this point in response to an absorption energy provided by the at least one laser beam 48. The changed structure of the glass can for example be characterized by a damaged glass substrate 43 and / or a deeper damaged glass substrate 44 and / or a thinned 52 glass substrate. Differences between the damaged glass substrate 43 and the deeper damaged glass substrate 44 can occur in different widths and / or depths of the at least one recess region when compared to each other.

[0051] The changed structure can allow to easily and precisely etch the damaged glass substrate region 43, thereby obtaining the recess 53. Such a process can allow to easily and precisely define a depth along z and / or a lateral extension along x and / or y of the recess 53. In particular, the embodiments allow to obtain a high aspect ratio, i.e. a large value of the depth along z compared to the lateral extension along x and / or y.

[0052] For example, in a set of recesses 53 all having an aspect ratio of 1 :5, one recess 53 can be 1 mm wide and 5 mm deep, another recess 53 can be 1 pm wide and 5 pm deep, and a third recess 53 can be 2 pm wide and 10 pm deep. Thus, the aspect ratio relates to the relation of the width to the depth, not the actual size of the recess. Such a process also allows to obtain a high aspect ratio, although the process is not limited to such an aspect ratio. For example, the aspect ratio based on the depth of the recess 53 can be at least 1 :5, 1 :7, 1 : 10 or even larger compared to the shortest lateral extension along x or z according to the width (shortest lateral extension) / depth (vertical extension). Using a damaged glass can result in high aspect ratio structures being parallel to each other.

[0053] The at least one laser beam 48 can allow for creating structures or damage areas with a lateral extension along x / y of less than 5 pm. The laser is configured for adjusting the intensity of the laser beam 48 such that the glass substrate 32 is damaged to a predetermined width and depth, resulting in a so-called damaged glass substrate area 43. For example, the damaged glass substrate area 43 can be susceptible to a removal process, such as a wet etching, a dry etching, a wafer cleaning, and a polymer removal. In order to obtain such a high aspect ratio in the glass substrate 32 of at least in the range of 1 : 10, a laser-induced deep etching (LIDE) can be performed. For example, the high aspect ratio can be in the range between 1 : 10 and at most 1 : 50, e.g., a standardized width of 1 and a comparative depth of 10 times the width. In the step of generating the recess 53, the glass substrate 32 can be locally modified by laser pulses according to a desired layout, e.g., the damaged glass substrate area 43, e.g., on the first side 34 of the glass substrate 32. A single laser pulse can be sufficient to modify the glass substrate 32 through the entire thickness of the glass substrate 32.

[0054] Masked isotropic wet etching of glass is difficult to produce micro features with an aspect ratio greater than 1. Standard laser drilling of glass is typically associated with low throughput and hidden micro cracks and heat-induced stresses, which can lead to yield loss and / or catastrophic failure of the final device. Through glass vias 55 manufactured by laser-induced deep etching (LIDE) have no micro cracks, debris, heat stress compared to conventional drilled micro vias. The sidewalls of LIDE generated micro vias are smooth, crack-free, debris-free and stress-free, enabling reliable metallization. The taper angle can be in the range between 0.1° and 30°.

[0055] The damaged glass substrate area 43 can later, e.g., after wet etching or deep etching, result in a recess 53 at the first side 36 of the second portion 18. According to one embodiment, the damaged glass substrate area 43 can comprise a first amount of a predetermined height, width, and depth ratio and a second amount of various different height, width, and depth ratios, e.g., a deeper damaged glass substrate area 44 resulting in various damaged glass substrate areas 43 in the glass substrate 32. According to one embodiment, the variation of the second amount of height, width, and depth ratios can be, for example, a deeper damaged glass substrate area 44 than the damaged glass substrate area 43. Furthermore, the deeper damaged glass substrate area 44 can be Figure 7 The resulting through glass via 55 (TGV) is shown to provide a foundation.

[0056] According to one embodiment, the glass substrate 32 can include various damaged glass substrate regions 43 and / or various deeper damaged glass substrate regions 44 arranged as parallel structures to face the first side 36 of the second portion 18. According to one embodiment, the damaged glass substrate regions 43 can include the deeper damaged glass substrate regions 44, but not vice versa.

[0057] Figure 5 A schematic cross-sectional view of the glass substrate 32 having at least one recess region 42 and damaged glass substrate regions 43 after performing a thinning process is shown. After performing a material removal process (e.g., thinning) on the structure of the glass substrate 32, Figure 4 A structure of the glass substrate 32 can be obtained after performing a material removal process (e.g., thinning) on the structure of the glass substrate 32. Figure 5 The thinning process can include a laser cutting process, a knife cutting process, machining, performing a chemical reaction of the material, resulting in a reduction of the thickness of the glass substrate 32. The glass substrate 32 with a reduced thickness can be referred to as a thin (thinned) glass substrate 52. Alternatively or additionally, the semiconductor substrate 22 and / or the filter structure 25 and / or the spacer layer 24 can be subjected to a material removal process to obtain a desired thickness.

[0058] That is, after performing a thinning process on the second side 37, the deeper damaged glass substrate regions 44 can result in the glass substrate 32 having a damage through its entire thickness, and later, a through-glass via 55. In other words, the deeper damaged glass substrate regions 44 from Figure 4 The deeper damaged glass substrate regions 44 from the glass substrate 32 having a damage through its entire thickness from the first side 36 of the second portion 18 to the second side 37 of the second portion 18. Although the glass substrate 32 is described as remaining unchanged on the first side 36, optionally, a processing step of changing the glass substrate 32 on the first side 36, e.g., arranging or removing material, can be performed.

[0059] Figure 6 A schematic cross-sectional view of the thin glass substrate 52 having added metallization structures 28, such as the metallization structures 28 already shown in Figure 2 The metallization structures 28 can include a connecting material or layer, which can provide an electrical link resulting in a later connection from the second side 37 of the second portion 18 to the first side 36 of the second portion 18. The metallization structures 28 can be arranged directly on, at, or in the later obtained through-glass via 55, e.g., a cap, a hat, or a covering providing electrical conductivity. The thin glass substrate 52 can remain unchanged on the first side 36 of the second portion 18.

[0060] Figure 7 A schematic cross-sectional view of the thin glass substrate 52 with the mask layer 58 and the through-glass via 55 on the first side 36 of the second portion 18 after processing the wet etchant is shown. In other words, the structure of the thin glass substrate 52 can be obtained from Figure 6 receiving Figure 7 the wet etchant. The mask layer 58 can be applied on the first side 36 of the second portion 18 of the thin glass substrate 52 covering the damaged glass substrate region 43, but not covering the later obtained through-glass via 55. After processing the wet etchant, the damaged glass substrate region 43 can be removed, resulting in the through-glass via 55 with a high aspect ratio.

[0061] According to one embodiment, the mask layer 58 at the first side 36 of the second portion 18 can comprise a mask of, for example, silicon nitride, which is a highly thermally stable material, for coupling the later added metallization structure 28 on the surface of the mask layer 58 facing the first side 36 of the second portion 18. The mask layer 58 material on the first side 36 of the second portion 18 can be resistant to the wet etching. Due to this resistance, the wet etching provides the through-glass via 55 on the first side 36 of the second portion 18 of the thin glass substrate 52. The through-glass via 55 can comprise a conductive structure inside the through-glass via providing an electrical connection from the first side 36 to the second side 37 of the second portion 18.

[0062] Figure 8 A schematic cross-sectional view of the thin glass substrate 52 and the through-glass via 55 is shown, wherein the through-glass via 55 provides an electrical connection from the first side 36 to the second side 37 of the second portion 18. The through-glass via 55 can comprise a conductive structure connecting the first side 36 to the second side 37 with a conductive material (e.g., silver, copper, gold, aluminum, nickel, iron, platinum, or gallium).

[0063] In other words, the conductive structure can form an electrical connection from the first side 36 to the second side 37 of the second portion 18 of the thin glass substrate 52 through the through-glass via 55.

[0064] According to one embodiment, the conductive structure can comprise the same material when compared to the connection material and / or the metallization structure 28 material. Additionally, Figure 8 A metallization structure 28 is shown arranged on the mask layer 58 facing the first side 36 of the second portion 18, such as has been described in Figure 2 , Figure 6 and Figure 7The metallization structure 28 is shown in FIG. 2. The mask layer 58 disposed between the thin glass substrate 52 and the metallization structure 28 can directly couple the thin glass substrate 52 and the metallization structure 28. The metallization structure 28 (one metallization structure 28 on the first side 36 of the second portion 18 and one metallization structure 28 on the second side 37 of the second portion 18) can provide electrical conductivity through the second portion 18 of the thin glass substrate 52.

[0065] Figure 9 A schematic cross-sectional view of the thin glass substrate 52 is shown, where the mask layer 58 can have an open area on the first side 36 of the second portion 18 that exposes the damaged glass substrate region 43 for a later wet etch process. The open area on the first side 36 of the second portion 18 that exposes the damaged glass substrate region 43 can expose at least a portion of the glass substrate 32. In a later process, a wet etch process can be applied to the thin glass substrate 52, resulting in the recess 53.

[0066] Figure 10 A schematic view of the second portion 18 is shown, including the thin glass substrate 52, the recess 53 that encloses the cavity 14, the metallization structure 28, the through glass via 55 as an electrical through connection from the first side 36 to the second side 37 of the second portion 18, and the mask layer 58 with the metallization structure 28 on the first side 36 of the second portion 18. In other words, the structure of the thin glass substrate 52 in FIG. 2 can be obtained by a wet etch process on the thin glass substrate 52 in FIG. 1. Figure 9 Figure 10 The structure of the thin glass substrate 52 in FIG. 2 can be obtained by a wet etch process on the thin glass substrate 52 in FIG. 1. In summary, the glass substrate is thinned, has metallization on the first side 36 and the second side 37 of the second portion 18, has a mask on the first side 36, has a through glass via 55 and a recess 53 that metallizes to connect the first side 36 and the second side 37 of the glass substrate.

[0067] Figure 11 ​A schematic cross-sectional view of the package 12 is shown, wherein the first portion 16 of the package 12 and the second portion 18 of the package 12 form the package 12 that can hermetically seal the cavity 14. The first portion 16 and the second portion 18 can be bonded to each other, for example, during a wafer bonding process. For example, a metal-to-metal bond between the first portion 16 and the second portion 18 can be a result of a wafer bonding process. The wafer bonded package can include a direct overlap stack of metallization 28 that bonds the first portion 16 and the second portion 18 of the package 12. During the wafer bonding process, the metallization 28 of the first portion 16 and the metallization 28 of the second portion 18 can form a tight mechanical and optional electrical connection and thus form part of the hermetic seal. Accordingly, the cavity 14 can be hermetically sealed to maintain a closed environment and prevent dust, oxygen, humidity, moisture, or any external contaminants from intruding to enter the sealed environment, thereby ensuring corrosion-free functionality over time.

[0068] Additionally, with the hermetic seal, the power consumption of the emitter 10 can be less. The hermetically sealed enclosure can allow for long-term stability of the generated radiation. The hermetic seal can reduce the heat generated in the heating structure 15, can increase the allowed current of the heating structure 15 compared to a conventional enclosure, while maintaining low power consumption, and stabilize the output of the emitter 10. The conventional enclosure can have a high resistance compared to the hermetically sealed enclosure. This high resistance can cause insignificant problems due to the little heat generated by the current flowing through the resistance. For example, the current must be increased to maintain functionality over time, resulting in an increase in power consumption. More specifically, the increased current not only increases the power consumption but also increases the temperature in the heating structure 15 to a non-negligible extent. This temperature increase in turn can increase the resistance.

[0069] According to one embodiment, the second portion 18 of the package 12 can include a glass substrate 32 having a recess 53 on a first side 36 of the second portion 18. According to one embodiment, the pressure inside the cavity 14 is lower, e.g., reduced, than the pressure outside or outward of the cavity 14. According to one embodiment, the emitter 10 and filter functions are monolithically integrated on the same wafer. The glass lid with the recess and through glass via 55 is achieved by a damage-free process with high aspect ratio structures. Illumination to infrared emitter 10 bonding can be performed at reduced gas pressure or, for example, hermetically within a vacuum by wafer level metal-to-metal bonding. With this layout, it is shown how the entire emitter 10 and filter system can be minimized in size and power consumption, for example, a vacuum sealed ceiling. Both size, such as height, and power consumption are key factors for integration into mobile devices. The integration of the IR emitter and IR filter can be monolithic.

[0070] According to one embodiment, different system concepts for a photoacoustic gas sensor are discussed (e.g. evaluated). The infrared emitter 10 chip is implemented as a MEMS chip with a thin heater film, a cavity 14 in the silicon substrate and optionally at least one vent hole 27. The filter chip is implemented as a Bragg reflector with different poly / oxide layers on a silicon substrate. The integration of the chip-on-chip stacking on chip level can be planned by distance holders or stands there. With this implementation, the height of the system emitter 10 and filter system is rather high and too high for mobile device solutions and also a rather low power consumption is shown. Thus, the present disclosure can be implemented with lower MEMS system costs, lower height and size and lower power consumption. The embodiments allow a solution how to produce a complete IR emitter 10 filter package 12 with cost reduction compared to now, with new available glass processing. Furthermore, due to first research findings, a power consumption reduction is shown due to the utilization of a vacuum hermetic sealing or reduced gas pressure.

[0071] Although some aspects have been described in the context of devices, it is clear that these aspects also represent a description of corresponding methods, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding device.

[0072] The above-described embodiments are merely illustrative of the principles of this application. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending patent claims and not by the specific details presented by way of description and explanation of embodiments of this application.

[0073] Reference signs

[0074] 10 emitter

[0075] 12 package

[0076] 13 radiation

[0077] 14 cavity

[0078] 15 heating structure

[0079] 16 first part

[0080] 18 second part

[0081] 22 semiconductor substrate

[0082] 24 spacer layer

[0083] 25 filter structure

[0084] 27 vent

[0085] 28 metallization structure

[0086] 32 glass substrate

[0087] 34 first side of first portion 16

[0088] 35 second side of first portion 16

[0089] 36 first side of second portion 18

[0090] 37 second side of second portion 18

[0091] 42 glass substrate region

[0092] 43 damaged glass substrate region

[0093] 44 deeper damaged glass substrate region

[0094] 48 at least one laser beam

[0095] 52 thin glass substrate

[0096] 53 recess

[0097] 55 through-glass via (TGV)

[0098] 58 mask layer

Claims

1. An emitter (10), comprising: a package (12) enclosing a cavity (14); wherein a first portion (16) of the package (12) is transparent for infrared radiation (13); and a second portion (18) of the package (12) comprises a glass material; a heating structure (15) configured for emitting the infrared radiation (13); wherein the heating structure (15) is arranged in the cavity (14) between the first portion (16) of the package (12) and the second portion (18) of the package (12); wherein the second portion (18) of the package (12) forms a glass cover having a recess (53) of the emitter and comprises a glass via (55); wherein the recess (53) encloses the cavity (14); wherein the glass via (55) comprises a metallization structure of the first portion (16) and a metallization structure of the second portion (18) forming an electrical connection; wherein the glass via (55) electrically connects the heating structure (15).

2. The emitter (10) according to claim 1, wherein the first portion (16) of the package (12) comprises a semiconductor substrate (22).

3. The emitter (10) according to claim 1 or 2, comprising a filter structure (25) configured to selectively transmit thermal radiation (13) of a predetermined wavelength range, the heating structure (15) being arranged between the filter structure (25) and the second portion (18).

4. The emitter (10) according to claim 3, wherein the first portion (16) of the package (12) is transparent for a first amount of the predetermined wavelength range; wherein the second portion (18) is transparent for a second amount of the predetermined wavelength, the second amount being lower compared to the first amount.

5. The emitter (10) according to claim 3 or 4, wherein the filter structure (25) is arranged on a surface of the semiconductor substrate (22).

6. The emitter (10) according to one of the preceding claims, wherein the filter structure (25) comprises a stack having a plurality of layers, the plurality of layers comprising a periodic variation of at least one layer property.

7. The emitter (10) according to one of the preceding claims, wherein the emitter (10) is a MEMS.

8. The emitter (10) according to one of the preceding claims, wherein the heating structure (15) comprises a membrane structure.

9. The emitter (10) according to one of the preceding claims, wherein the cavity (14) is hermetically sealed.

10. The emitter (10) according to one of the preceding claims, wherein a pressure inside the cavity (14) is lower than a pressure outside the cavity (14).

11. The emitter (10) according to one of the preceding claims, wherein the second portion (18) of the package (12) comprises a recess (53) on a first side (36) of the second portion (18).

12. The emitter (10) according to one of the preceding claims, wherein the second portion (18) of the package (12) comprises a through-glass via (55).

13. The transmitter (10) according to one of the preceding claims, comprising: a mask layer (58) at the first side (36) of the second portion (18) of the package (12) and comprising a connection layer arranged at the mask layer (58), the connection layer forming a mechanical connection with the first portion (16) of the package (12).

14. The emitter (10) according to one of the preceding claims, wherein the through- glass via (55) comprises the same material when compared to the connection layer.

15. A method for manufacturing an emitter (10), the method comprising: providing a heating structure (15); providing a first portion (16) of a package (12), the first portion (16) of the package (12) being transparent for infrared radiation (13); and providing a second portion (18) of the package (12), the second portion (18) of the package (12) comprising a glass material; arranging the heating structure (15) in a cavity (14) enclosed by the package (12) between the first portion (16) of the package (12) and the second portion (18) of the package (12); configuring the heating structure (15) for emitting the infrared radiation (13); forming the second portion (18) of the package (12) as a glass cover having a recess (53) of the emitter and comprising a glass via (55), such that the recess (53) encloses the cavity (14); and arranging a metalization structure of the first portion (16) and a metalization structure of the second portion (18) forming an electrical connection in the glass via (55); electrically connecting the heating structure (15) by the glass via (55).

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