Vapor monitoring sensor assembly in processing chamber

Abstract

One or more embodiments described herein generally relate to methods and systems for monitoring film thickness using a sensor assembly. In embodiments described herein, a processing chamber has a chamber body, a substrate support disposed in the chamber body, a cover disposed over the chamber body, and a sensor assembly coupled to the chamber body at a lower portion of the sensor assembly. The sensor assembly is coupled to the cover at an upper portion of the sensor assembly. The sensor assembly includes one or more apertures disposed through one or more sides of the sensor assembly, and one or more sensors disposed in the sensor assembly through the one or more apertures.

Description

Technical Field

[0001] Embodiments of the present disclosure are generally directed to methods and systems for monitoring film thickness using a sensor assembly for multi-material deposition control. Background Art

[0002] Organic vapor deposition is becoming increasingly relevant in the construction of semiconductor devices and other optical devices. The vapor deposition process typically involves heating a material maintained at a desired pressure to a desired temperature, causing the heated material to evaporate, and then allowing it to be transferred to a substrate, where the evaporated material condenses onto the surface of the substrate. Organic vapor deposition is often used to form CMOS image sensors. However, organic vapor deposition can also be used to form organic light emitting diodes (OLEDs), organic photodetectors, solar cells, and other similar devices. These devices are used to manufacture television screens, computer monitors, mobile phones, and other handheld devices for displaying information. The range of colors, brightness, and viewing angles that can be achieved by OLED displays is greater than that of conventional LED displays, because OLED pixels emit light directly and do not require a backlight, and therefore the energy consumption of the formed device is low. In addition, OLEDs can be manufactured on flexible substrates, which also brings other device applications.

[0003] Although these devices are useful, many challenges are encountered in their manufacture. In order to manufacture the film stack of the device with high efficiency, the co-deposition of materials is often desired. When materials are co-deposited on a substrate, the placement of the materials on the substrate surface is important for ensuring that the resulting film layer on the substrate can form a functional device. In the case of not controlling the placement of the material, the resulting deposited material in the formed layer can form an undesirable domain size and morphology that hinders the charge separation and extraction in the organic electronic device. In some device configurations, it is desired that the material is deposited on the substrate so that a variety of materials are mixed in a single formed layer or a variety of materials form a superlattice structure. However, conventional vapor deposition processes cannot reliably form this type of layer or composite layer containing a variety of materials without using a sensor to monitor vapor deposition. The chamber with a sensor usually has an extended downtime to manage the maintenance of the sensor.

[0004] Thus, there is a need for methods and apparatus for managing film deposition rate and thickness when forming films on substrates having multiple materials. Utility Model Content

[0005] In some embodiments, a processing chamber is provided, comprising: a chamber body, a substrate support disposed in the chamber body, a cover disposed above the chamber body, and a sensor assembly, the sensor assembly coupled to the sensor assembly of the chamber body at a lower portion of the sensor assembly. The sensor assembly is coupled to the cover at an upper portion of the sensor assembly. The sensor assembly further comprises one or more holes disposed through one or more sides of the sensor assembly. One or more sensors are disposed in the sensor assembly through the one or more holes.

[0006] In some embodiments, a method for processing a substrate is provided, including exposing a first substrate to a first set of vapors in a processing chamber while monitoring at least one property of the first set of vapors using a first sensor disposed in a sensor assembly. The sensor assembly is disposed between a lid and a chamber body and surrounds a showerhead. The method includes removing the first substrate from the processing chamber and replacing the first sensor with a second sensor without opening the lid of the processing chamber. Exposing a second substrate to a second set of vapors in the processing chamber while monitoring at least one property of the second set of vapors using a second sensor disposed in the sensor assembly.

[0007] In some embodiments, a sensor assembly is provided, comprising an adapter having a first major surface and a second major surface opposite the first major surface. A shield is disposed within the adapter. The shield comprises a shelf and an inner surface extending from a top of the shelf to the first major surface, the shelf and the inner surface forming a recess. A side extends from the first major surface of the adapter to the second major surface. The side comprises one or more holes disposed therethrough, each hole being aligned with a hole disposed through the inner surface of the shield and configured to receive a sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to be able to understand in detail the manner in which the above-mentioned features of the present disclosure are used, a more specific description of the present disclosure briefly summarized above may be obtained by reference to the embodiments, some of which are shown in the accompanying drawings. However, it will be noted that the drawings only illustrate exemplary embodiments and are not to be considered as limiting the scope of the present disclosure, and the present disclosure may allow for other equally effective embodiments.

[0009] Figure 1 is a schematic diagram of a processing system according to some embodiments.

[0010] Figure 2 Depicted is a side view of a processing chamber having a sensor assembly according to some embodiments.

[0011] Figure 3 Depicted is an isometric view of a processing chamber according to some embodiments.

[0012] Figure 4Depicted is an isometric view of a sensor assembly according to some embodiments.

[0013] Figure 5 Depicted is a side view of a sensor assembly according to some embodiments.

[0014] Figure 6 Depicted is a cross-sectional side view of a shroud of a sensor assembly according to some embodiments.

[0015] Figure 7 Depicted is a cross-sectional side view of a groove portion of a shield of a sensor assembly according to some embodiments.

[0016] Figure 8 A flow chart is depicted for replacing one or more sensors of a sensor assembly according to some embodiments.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0018] In the following description, several specific details are set forth to provide a more thorough understanding of the embodiments of the present disclosure. However, it will be apparent to those skilled in the art that one or more embodiments of the present disclosure may be practiced without one or more of these specific details. In other cases, well-known features are not described to avoid confusing one or more embodiments of the present disclosure.

[0019] Embodiments of the present disclosure generally relate to apparatus and methods for forming a substrate in one or more deposition processes. In embodiments described herein, a processing system includes the same or different evaporable materials each contained in a separate ampoule. Each evaporable material flows via a gas line to a separate portion of a showerhead contained in a processing chamber. One or more sensors are positioned below the showerhead, such as a sensor below each portion of the showerhead. Each material is directed from the showerhead through the sensor to a substrate resting on the surface of a rotating substrate support. Controlling the processing parameters of the processing system while the material flows from the ampoule to the substrate can result in a plurality of materials being mixed within a single formed layer or a plurality of materials forming a superlattice structure. By controlling the processing parameters, the relative composition of the formed layer including a plurality of deposited materials can also be achieved. The sensors disclosed herein provide accurate monitoring of film deposition rate and film thickness by measuring the concentration of certain components being deposited (such as small organic molecules).

[0020] Controlling the film deposition rate and the rotation speed of the substrate support results in a deposition process capable of forming a film having a desired composition on the substrate surface. Thus, the resulting film has a desired domain size and morphology, thereby resolving the problem of the resulting film having an undesirable domain size and morphology that hinders charge separation and extraction in organic electronic devices.

[0021] Figure 1 1 is a schematic diagram of a processing system 100 according to at least one embodiment described herein. The processing system 100 includes a processing chamber 102. The processing chamber 102 is defined by sidewalls 104, a bottom 106, and a chamber lid 108, thereby forming a processing volume 110. The processing chamber 102 is configured to process a substrate, such as a substrate 114, within the processing volume 110 of the processing chamber 102. The substrate 114 is supported by a substrate support 112 disposed in the processing chamber 102. A mask 113 having an opening is positioned above the substrate 114. The mask 113 is positioned so that a material flows onto a separate area of ​​the substrate 114 to form an appropriate device. In some embodiments, the processing chamber 102 can be configured as a chemical vapor deposition (CVD) chamber, an atomic layer deposition (ALD) chamber, or a physical vapor deposition (PVD) chamber that performs deposition of a processing material (such as organic vapor deposition) according to the present disclosure. However, other chambers may be used and modified using the teachings provided herein.

[0022] In some embodiments, by individually controlling the mass flow rate of each of the materials (each of which requires a different evaporation temperature), a material layer (not shown), or a derivative thereof, may be formed, condensed, or otherwise deposited on the substrate 114 by a deposition process. Therefore, the embodiments herein cannot be evaporated via a conventional showerhead. In some embodiments, some material combinations used may be a CuPc:C60 mixture; CBP:Ir(ppy) 3 mixture; distributed Bragg reflector (DBR) superlattice structure (e.g., paired MgF 2 / SiOx), and / or other similar combinations. The showerhead 116 may have one or more sections, such as a first section 122, a second section 130, a third section 166, and a fourth section 168. Figure 1Four sections are shown in FIG. 1 , and other showerheads including any number of sections may be provided. Using multiple sections, the showerhead 116 is configured to deposit a variety of process materials to form a desired film on the substrate 114, which is described in more detail below. In some embodiments, other chambers without a showerhead 116 are also contemplated.

[0023] The chamber lid 108 is positioned above the showerhead 116. Figure 1 As shown, the processing system 100 includes a first ampoule 118, a second ampoule 126, a third ampoule 174, and a fourth ampoule 176. A first material 162 is contained within a processing volume of the first ampoule 118, a second material 164 is contained within a processing volume of the second ampoule 126, a third material 178 is contained within a processing volume of the third ampoule 174, and a fourth material 180 is contained within a processing volume of the fourth ampoule 176. The first ampoule 118 delivers the first material 162 to the first section 122 of the showerhead 116 via the first transfer line 120, the second ampoule 126 delivers the second material 164 to the second section 130 of the showerhead 116 via the second transfer line 128, the third ampoule 174 delivers the third material 178 to the third section 166 of the showerhead via the third transfer line 171, and the fourth ampoule 176 delivers the fourth material 180 to the fourth section 168 of the showerhead 116 via the fourth transfer line 173. Figure 1 Four ampoules are illustrated in FIG, but other embodiments may include any number of ampoules, each containing its own process material and each delivering the process material to a separate section of the showerhead (e.g., the showerhead may include as many separate sections as there are different materials provided). Additionally, in other embodiments, two opposite sections of the showerhead 116 may be connected to the same ampoule to deposit the same material.

[0024] In these embodiments, the temperature in the processing system 100 is controlled by heating elements contained in different parts of the system, such as along one or more delivery lines 120 , 128 , 171 , 173 , and / or one or more ampoules 118 , 126 , 174 , 176 .

[0025] To achieve temperature control of the substrate 114, the substrate support 112 includes a plurality of coolant channels 155. The coolant channels 155 are used to flow a coolant, such as water, ethylene glycol, or other suitable coolant, therein. Typically, the temperature of the substrate is maintained low enough so as not to affect the film composition. The temperature of the substrate can be maintained at about 0 degrees Celsius to about 70 degrees Celsius.

[0026] Controlling the temperature in different parts of the processing system 100 can be used to control the mass flow rate in different parts of the processing system 100. When the temperature increases, it causes the flow rate of the evaporated material in the open system to increase due to the decrease in the density of the evaporated material. When the temperature decreases, it causes the flow rate to decrease due to the increase in the density of the evaporated material. In the embodiments described herein, the mass flow rate can be controlled without the use of a carrier gas. However, in other embodiments, a carrier gas can be optionally provided. In some embodiments, the pressure in the system is maintained at about 10E. -04 Torr (about 0.1333 Pascal) to about 10E -10 (about 1.333E -7 Pascal).

[0027] In these embodiments, the substrate support 112 is configured as follows Figure 1 13. In addition, the substrate support 112 is configured to move vertically as indicated by arrow 135. The substrate support 112 is controlled to rotate at a speed such that it achieves a desired deposited film result on the surface of the substrate 114.

[0028] As discussed above, some parameters that affect the size of the regions formed within the resulting film are the mass flow rate out of the showerhead 116, the pressure within the processing volume 110, and the rotation rate of the substrate support 112. Some factors that determine the mass flow rate of material out of the showerhead 116 are: the temperature in each of the first section 122, the second section 130, the third section 166, and the fourth section 168 of the showerhead 116; the flow rate of material delivered to each of the first section 122, the second section 130, the third section 166, and the fourth section 168 of the showerhead 116; the flow regime (e.g., molecular flow) within the material delivery components; the temperature of each of the first ampoule 118, the second ampoule 126, the third ampoule 174, and the fourth ampoule 176; the temperature gradient from each of the ampoules 118, 126, 174, 176 to the showerhead 116; and the pressure of the processing chamber 102. Controlling these factors will determine the deposition rate of the material, resulting in a film having a desired composition formed on the surface of substrate 114 .

[0029] In some embodiments, each of the above factors can be controlled by a controller 136. The controller 136 communicates with the hardware contained within the entire processing system 100, including the hardware contained within the processing chamber 102. The controller 136 may include a central processing unit (CPU) 136A, a memory 136B, and support circuits (or I / O) 136C. The CPU 136A may be one of any form of computer processor used in industrial settings to control various processes and hardware (e.g., motors, valves, power delivery components and other related hardware) and monitor processes (e.g., process time and substrate positioning or location). The memory 136B is connected to the CPU 136A and may be one or more of readily available memories, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage device (local or remote). Software instructions, algorithms, and data may be encoded and stored in the memory 136B for instructing the CPU 136A. Support circuits 136C are also connected to CPU 136A for supporting the processor in a conventional manner. Support circuits 136C may include conventional caches, power supplies, clock circuits, input / output circuitry, subsystems, and the like. A program (or computer instructions) readable by the controller determines which tasks may be performed within processing system 100.

[0030] Figure 2 A side view of a processing chamber 102 is depicted according to some embodiments. The processing chamber 102 includes a chamber body 201 formed by a sidewall 104 and a bottom 106, a substrate support 112 disposed in a processing volume 110 of the chamber body 201. A sensor assembly 200 is coupled to the chamber body 201 at a lower portion 203 of the sensor assembly 200. The sensor assembly 200 is coupled to the lid 108 at an upper portion 205 of the sensor assembly 200. The sensor assembly 200 includes one or more holes disposed through one or more sides of the sensor assembly. One or more sensors are disposed in the sensor assembly 200 through the one or more holes and secured by a flange 207. Figure 2 One sensor is shown mounted with a sensor connector 202. In some embodiments, the sensor connector 202 includes a cooling tube, such as a water tube for cooling the sensor during operation.

[0031] Figure 3 yes Figure 11 is an isometric cross-sectional view of a portion of a processing chamber 102 of FIG. The chamber lid 108 is illustrated as being located above the showerhead 116. The showerhead 116 extends to be at least partially surrounded by the sensor assembly 200. In some embodiments, the showerhead 116 is disposed completely surrounded by the sensor assembly 200, such as being located within a recess of the sensor assembly 200. The showerhead segments 166 and 168 are depicted with corresponding sensors disposed below each segment. In some embodiments, the sensor assembly 200 includes a removable adapter 301 configured to be stacked above the chamber body 201 and below the lid 108. The sensor assembly 200 further includes a shield 137 mounted within the adapter around the substrate 114. O-rings 303 and 305 can be disposed between the adapter 301 and the shield 137 and at the interface between the adapter 301 and the lid 108. The processing chamber can be operated with or without the sensor assembly 200. In some embodiments, when the adapter is installed, the substrate support is slightly lifted to maintain an operating distance from the showerhead. In some embodiments, the distance between the sensor of the sensor assembly 200 and the showerhead is about 1 cm to about 5 cm, or greater than 5 cm. The distance between the showerhead and the sensor is adjusted by adjusting the thickness of the removable adapter sensor assembly 200. Alternatively, the distance between the showerhead and the sensor is adjusted by stacking spacers above the adapter. In some embodiments, the gap between the inner periphery of the recess and the outer periphery of the showerhead is about 1 cm to about 7 cm.

[0032] The substrate 114 is supported on a carrier 300, or directly on a substrate support. The carrier 300 will be supported on a substrate support 112 (not shown). A shadow mask at least partially covers the substrate 114. The shadow mask includes a plurality of fine openings that provide a pattern for depositing a film on the substrate 114. In some embodiments, a shadow mask is not used.

[0033] exist Figure 3 1, the shield 137 and the substrate 114 are in a processing position. A processing cavity 310 is formed between the showerhead 116, the substrate 114, and the wall 135 of the shield 137. The processing cavity 310 confines the deposition material therein and minimizes deposition on chamber components outside the processing cavity 310. The chamber lid 108 includes inlets 325 each surrounded by a heating element 330 that provides evaporated material to the showerhead 116. Although the evaporated material is depicted as being supplied from outside the processing chamber, other arrangements are also contemplated, such as providing the evaporated material from a source within the processing chamber.

[0034] refer to Figures 4 to 7 Sensor assembly 200 is described. Figure 4is an isometric view of the sensor assembly 200. The shield 137 is removably disposed within the adapter 301 such that a rim 412 of the shield 137 is fitted within an annular recess of the adapter 301. The sensor assembly 200 includes a first major surface 205 and a second major surface 203 opposite the first major surface 205. The shelf 402 is defined by a lower surface of the shield 137 extending radially inward from the inner sidewall surface 315. The sensor assembly 200 includes one or more sides (e.g., sides 407, 408, 409, 411). Although four sides are depicted in the figure, other shapes are also contemplated, such as a circular perimeter, or 5 to 8 sides. The shield 137 includes a groove 404 disposed at certain portions of the shelf 402 and configured to receive the sensor 314. In some embodiments, the flange 207 is compression-fitted so that the sensor can be positioned at various locations along the groove, such as for evaluating the showerhead profile at various deposition locations along one or more radial paths of the showerhead.

[0035] Figure 5 4 is a side view of the sensor assembly as viewed from side 408. Each side (including side 408) extends from first major surface 205 to second major surface 203. At least one side (such as side 408) includes one or more holes 502 disposed therethrough. One or more holes 502 receive sensors 314 secured using fasteners (such as flange 207). Holes 502 are aligned with grooves 404 capable of receiving sensors 314. The sensors include a crystalline active area having a diameter of about 1 to about 2 cm. Each sensor is disposed near the edge of the showerhead and is located near the midpoint of the perimeter of each showerhead portion. The placement of each sensor reduces blocking material from reaching the substrate. Other placements, such as closer to the middle of the showerhead, are also contemplated.

[0036] Figure 6 4 is a cross-sectional view of the shield 137 of the sensor assembly 200 taken at a location without the groove 404. The shelf 402 includes an annular groove 602 concentrically and radially inwardly from the inner surface 315 of the sensor assembly 200. The shelf 402 includes an annular raised portion 604. The annular raised portion 604 is disposed radially inwardly relative to the annular groove 602. The innermost portion 606 tapers from the raised portion 604 to the second major surface 203. As can be seen in FIG. Figure 6 As can be seen in FIG. 1 , the portions of the shelf that do not include the grooves have different heights relative to the second major surface 203, such as at the recess 602, the raised portion 604, and the innermost portion 606. In contrast, Figure 7 As can be seen in FIG. 7 , in the portion 704 having the grooves 404 , the height of the shelf 402 is uniform along each of the one or more grooves 404 .

[0037] Figure 74 is a cross-sectional view of the shield 137 of the sensor assembly 200 at a location having a groove 404 and depicting the holes 502 aligned with the grooves 404. In some embodiments, each groove 404 is substantially aligned with one or more holes (e.g., 502). Each of the one or more grooves 404 is configured to receive a sensor, such as a quartz crystal monitor (QCM) sensor 314. Other sensors are also contemplated.

[0038] Figure 8 A flow chart for replacing one or more sensors of a sensor assembly according to some embodiments is depicted. Method 800 includes, at operation 802, exposing a first substrate to a first set of vapors in a processing chamber while monitoring at least one property of the first set of vapors. The at least one property is a concentration of the vapors distributed over the sensor, such as an organic material concentration. The concentration is indicative of a film deposited over the first substrate, such as a thickness of the first substrate. The first set of vapors may include a mixture of vapors, or separate vapors distributed to different portions of the first substrate. The first set of vapors is distributed through a showerhead disposed over the first substrate.

[0039] At operation 804, the first substrate is removed from the processing chamber. In some embodiments, several substrates are processed after removing the first substrate, such as by repeating operations 802 and 804 in a cycle.

[0040] After removing the first substrate and / or the subsequently processed substrate, at operation 806, the first sensor is replaced with the second sensor without opening the lid of the chamber body. The first sensor is removed by removing the flange from the side of the sensor assembly. Before removing the flange, the processing chamber is vented to increase the pressure of the processing chamber. In some embodiments, the component from the first sensor is removed and replaced with another component, such as a crystal. The first sensor with the replaced component is thus configured as a second sensor. In other embodiments, the first sensor is removed and replaced with a second sensor having different sensing capabilities or components (such as different crystals). In some embodiments, the sensor is positioned through the hole of the sensor assembly into a recess of the sensor assembly. The sensor is positioned without removing the lid of the processing chamber. The flange is attached above the hole to fix the sensor in the recess of the sensor assembly. It has been found that the ability to remove and replace the sensor or sensor component without removing the lid enables simple maintenance of the sensor (such as a QCM sensor). The crystal of the QCM sensor is replaced by removing the flange from the side of the sensor assembly, removing the sensor through the hole of the sensor assembly, replacing the sensor (or a component of the sensor (e.g., the crystal)), and securing the sensor or replacement sensor intact back into the sensor assembly without opening the lid of the process chamber. Thus, chamber downtime is greatly reduced. After replacing the flange, the process chamber is evacuated to operating pressure to process a second substrate.

[0041] Compared to systems in which sensors are placed along gas lines or disposed in other parts of the chamber, positioning the sensor directly below the showerhead enables accurate sensing of material concentration. In addition, placing the sensor directly below the showerhead enables a compact chamber design. Operation 808 includes exposing a second substrate to a second set of vapors in the processing chamber while monitoring at least one property of the second set of vapors, such as organic material concentration, using a second sensor. In some embodiments, the second set of vapors uses the same vapor as the first set of vapors. The sensor is an array of sensors disposed within the substrate assembly. Each sensor faces the showerhead and each sensor is disposed relative to each other on a common plane. The common plane is substantially parallel to the bottom surface of the showerhead.

[0042] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is to be determined by the claims that follow.

Claims

1. A processing chamber, characterized in that: Include: Chamber body; a substrate support disposed in the chamber body; a cover, disposed above the chamber body; as well as a sensor assembly coupled to the chamber body at a lower portion of the sensor assembly, the sensor assembly coupled to the cover at an upper portion of the sensor assembly, the sensor assembly further comprising: one or more holes disposed through one or more sides of the sensor assembly, and One or more sensors are disposed in the sensor assembly through the one or more holes.

2. The processing chamber of claim 1, wherein the one or more sensors are quartz crystal monitor (QCM) sensors.

3. The processing chamber of claim 1 , wherein the sensor assembly comprises: adapter; and A protective cover is disposed in the recess of the adapter.

4. The processing chamber of claim 1, further comprising: A showerhead is coupled to the cover, wherein the showerhead is at least partially disposed within the upper portion of the sensor assembly.

5. The processing chamber of claim 4, wherein the showerhead is disposed entirely within a recess defined in the upper portion. 6 . The processing chamber of claim 5 , wherein a gap between an inner perimeter of the recess and an outer perimeter of the showerhead is about 1 cm to about 7 cm.

7. The processing chamber of claim 1, further comprising one or more flanges removably coupled to the one or more holes and configured to secure the one or more sensors within the sensor assembly.

8. The processing chamber of claim 1, wherein the sensor assembly further comprises a shelf comprising a groove aligned with the one or more holes and configured to receive each of the one or more sensors.

9. The processing chamber of claim 1, wherein each of the one or more sensors faces a showerhead of the lid.

10. The processing chamber of claim 1, wherein a first sensor is positioned on a first side of the one or more sides, and a second sensor is positioned on a second side of the one or more sides opposite the first side.

11. A sensor assembly, characterized in that: Include: an adapter comprising a first major surface and a second major surface opposite the first major surface; as well as a shield disposed in the adapter, the shield comprising a shelf and an inner surface extending from a top of the shelf to the first major surface, the shelf and the inner surface forming a recess; as well as A side extends from the first major surface to the second major surface of the adapter, the side including one or more holes disposed therethrough, each hole being aligned with a hole disposed through the inner surface of the shield and configured to receive a sensor.

12. The sensor assembly of claim 11, wherein the shelf further comprises one or more grooves disposed within the top of the shelf and aligned with the one or more holes of the adapter, wherein each of the one or more grooves is configured to receive a quartz crystal monitor (QCM) sensor.

13. The sensor assembly of claim 12, wherein the shelf further comprises an annular groove concentrically and radially inwardly from the inner surface of the shroud.

14. The sensor assembly of claim 13, wherein the shelf further comprises an annular raised portion, wherein the annular raised portion is disposed radially inwardly relative to the annular groove.

15. The sensor assembly of claim 14, wherein an innermost portion of the shelf tapers inwardly from the annular raised portion to the second major surface, wherein the shelf is configured to support an array of sensors.

16. The sensor assembly of claim 14, wherein a thickness of the shelf is uniform along each of the one or more grooves.

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