Hybrid shaft assembly for thermal control in a heated semiconductor pedestal - Patent Application 20070123633

Abstract

A hybrid shaft assembly for use in a controlled atmosphere chamber, such as a heated pedestal for semiconductor manufacturing, includes a substrate, a hub having an upper portion and a lower portion, and a shaft secured to the substrate by an upper bonding layer and to the lower portion of the hub by a lower bonding layer, the shaft being constructed of a material having a lower thermal conductivity than a material of the hub and a material of the substrate.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Patent Application No. 63 / 341,163, filed May 12, 2022. The disclosures of the above applications are incorporated herein by reference. [Technical field]

[0002] The present disclosure relates to pedestals for use in semiconductor manufacturing equipment, and more particularly to pedestal structures for achieving thermal uniformity in a wafer contact zone. [Background technology]

[0003] The statements in this section provide background information related to the present disclosure and may not constitute prior art.

[0004] In the processing of semiconductor wafers, a pedestal is placed within a processing chamber to support the semiconductor wafer for etching. The pedestal is often made from a ceramic material. The pedestal typically includes a heater plate and a shaft secured to a lower portion of the heater plate. The shaft is typically hollow. The shaft is configured to receive various electrical connections for providing power to the heater plate and for monitoring various system parameters during the etching process.

[0005] Because semiconductor wafers must be manufactured within very tight tolerances, the thermal uniformity of the pedestal, and more specifically, the thermal uniformity of the top surface of the heater plate adjacent to the semiconductor wafer, must be tightly controlled. Thus, various approaches have been adopted to reduce the effects of heat sink / loss during the manufacturing of semiconductor wafers. For example, multiple zone heaters have been used throughout the thickness of the heater plate, and different materials have been used in the construction of the pedestal to provide a more uniform temperature during the etching process. Additional or secondary heaters have been provided in the shaft or on the bottom surface of the heater plate. However, volume and cost constraints limit the possibility of providing additional heaters to reduce heat loss.

[0006] These challenges, as well as other heat loss challenges within semiconductor processing equipment, associated with providing thermal uniformity along the top surface of a heated pedestal, are addressed by the present disclosure. Summary of the Invention

[0007] This section provides a general overview of the disclosure and is not an exhaustive disclosure of its complete scope or all of its features.

[0008] The present disclosure provides a hybrid shaft assembly for use in a controlled atmosphere chamber, the hybrid shaft assembly including a substrate, a hub having an upper portion and a lower portion, the upper portion being secured to the substrate by an upper bonding layer, and a shaft secured to the lower portion of the hub by a lower bonding layer, the shaft being constructed of a material having a lower thermal conductivity than a material of the hub and a material of the substrate.

[0009] The hybrid shaft assembly variations may be implemented individually or in any combination. At least one of the upper and lower bonding layers is comprised of material sputtered onto a surface of the upper portion of the hub and the lower portion of the hub, respectively. The sputtered material forms a layer approximately 2 μm thick. At least one of the upper hub portion and the lower hub portion includes a plurality of mesas. The upper portion of the hub is spaced a nominal distance from the lower surface of the substrate. A number of preform pieces are disposed between the upper portion of the hub and a lower surface of the substrate. The preform pieces are beads. The preform piece comprises a zirconia material. The lower portion of the hub is spaced a nominal distance from the upper surface of the shaft. A number of preform pieces are disposed between the lower portion of the hub and an upper surface of the shaft. The preform piece comprises a zirconia material. The upper portion of the hub includes a radical flange. The hub is integral with the substrate. At least one of the upper and lower bonding layers is formed from an aluminum foil preform. The surface area of ​​the aluminum foil preform is less than the total surface area of ​​the top surface of the upper portion of the hub. The surface area of ​​the aluminum foil preform is less than the total surface area of ​​the lower surface of the hub. The surface area of ​​the aluminum foil preform is approximately 50% less. The aluminum foil preform is approximately 0.08 inches thick. The substrate is made of an AlN material, the hub is made of an AlN material, and the shaft is made of an AlN material. 2 O 3 Materials. A secondary shaft element is secured to a lower portion of the shaft, the secondary shaft element comprising a material having a lower thermal conductivity than a material of the shaft. The shaft is made of a material that has a decreasing thermal conductivity from the upper portion to the lower portion of the shaft. The thermal conductivity of the material of the shaft decreases continuously from the upper portion to the lower portion of the shaft. The thermal conductivity of the shaft material is an order of magnitude lower than the thermal conductivity of the hub material and the substrate material. The upper and lower bonding layers form a hermetically sealed interface. The leakage rate of the hermetically sealed interface is about 1×10 -6 atm cc / sec He. The length of the shaft is approximately five times the length of the hub. At least one electrically functional element is embedded within the substrate. The at least one electrically functional element is selected from the group consisting of a heater, an RF antenna, and a clamp electrode. The upper portion is a flanged upper portion, each of the flanged upper portion and the lower portion defining a plurality of mesas and including a sputtered layer of aluminum, and the upper bonding layer and the lower bonding layer including an aluminum braze material having an aluminum content of 99.99%.

[0010] Further areas of applicability will become apparent from the description herein. It should be understood that the description and specific examples herein are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0011] In order that the present disclosure may be more fully understood, various forms thereof will now be described, by way of example, with reference to the accompanying drawings in which:

[0012] [Figure 1] FIG. 1 is a top perspective view of a hybrid shaft assembly constructed in accordance with the teachings of the present disclosure for use in a controlled atmosphere chamber, such as a heated pedestal for semiconductor manufacturing.

[0013] [Diagram 2] FIG. 2 is a bottom perspective view of the hybrid shaft assembly of FIG.

[0014] [Diagram 3] FIG. 3 is a top exploded perspective view of the hybrid shaft assembly of FIG.

[0015] [Figure 4] FIG. 4 is a bottom exploded perspective view of one hybrid shaft assembly.

[0016] [Diagram 5] FIG. 5 is a side view of the hybrid shaft assembly of FIG.

[0017] [Figure 6] 6 is a side cross-sectional view of the hybrid shaft assembly of FIG. 1.

[0018] [Figure 7] FIG. 7 is a top perspective view of an upper portion of a shaft of a hybrid shaft assembly constructed in accordance with the teachings of the present disclosure.

[0019] [Figure 8] FIG. 8 is a top view of a hub and upper aluminum preform constructed in accordance with the teachings of the present disclosure.

[0020] [Figure 9] FIG. 9 is a bottom perspective view of a hub and lower aluminum preform constructed in accordance with the teachings of the present disclosure.

[0021] [Figure 10] FIG. 10 is a top perspective view of a hub having sputtering material and constructed in accordance with the teachings of the present disclosure.

[0022] [Figure 11] FIG. 11 is a bottom perspective view of a hub having sputtering material and constructed in accordance with the teachings of the present disclosure.

[0023] [Figure 12] FIG. 12 is a side view of another form of a hybrid shaft assembly constructed in accordance with the teachings of the present disclosure.

[0024] [Figure 13] FIG. 13 is a manufacturing flow diagram of a method for bonding a substrate, a hub, and a shaft in accordance with the teachings of the present disclosure.

[0025] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following description is merely illustrative and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference characters indicate like or corresponding parts and features.

[0027] 1-4 illustrate a hybrid shaft assembly for use in a controlled atmosphere chamber. The hybrid shaft assembly is generally indicated at 20. In this embodiment, the hybrid shaft assembly 20 is in the form of a pedestal (e.g., a heated pedestal) for use in semiconductor manufacturing. However, application to semiconductor manufacturing should not be construed as limiting the scope of the present disclosure.

[0028] The hybrid shaft assembly 20 generally includes a substrate 30, a hub 40, and a shaft 50. One form of substrate 30 is a ceramic material, such as, by way of example, AlN (aluminum nitride), and includes one or more electrical functional elements used in semiconductor manufacturing processes. Such electrical functional elements (not shown for clarity) in substrate 30 may include, for example, a heater (having one or more zones), an RF antenna (one or more electrically independent / separate sections), and / or a clamp electrode. Such electrical functional elements are described in detail in commonly owned U.S. Pat. No. 10,287,215, the contents of which are hereby incorporated by reference in their entirety.

[0029] Advantageously, the shaft 50 comprises a material that has a lower thermal conductivity than the material of the hub 40 and the material of the substrate 30. For example, in one embodiment, the substrate 30 is an AlN material (approximately 150-250 W / (m·°K)), the hub 40 is also an AlN material, and the shaft 50 is an AlN material. 2 O 3 (approximately 30 W / (m·°K)) material. Thus, in this configuration, the thermal conductivity of the shaft 50 material is an order of magnitude lower than the thermal conductivity of the hub 40 material and the substrate 30 material. As a result, the hybrid shaft assembly 20 has low heat loss through the shaft 50, thus improving temperature uniformity in the wafer contact zone (not shown) during processing operations in a controlled atmosphere chamber.

[0030] The hub 40 has an upper portion 42 that is bonded to the substrate 30 by an upper bonding layer (discussed in more detail below) and a lower portion 44 that is bonded to the shaft 50 by a lower bonding layer (discussed in more detail below). The upper portion 42 of the hub 40, as shown, defines a radical flange 45. The radical flange 45 generally provides an increased area for the upper bonding layer to bond to and secure the substrate 30. However, in one form, the hub 40 is integral with the substrate 30 and, in one form of the present disclosure, is formed as a single piece (not shown), thereby eliminating the need for an upper bonding layer.

[0031] As also shown in Figures 5-7, the shaft 50 includes a substrate 52. In this embodiment, the substrate 52 is integrally formed with the shaft 50 as one piece. The shaft 50 is generally hollow and includes a bore 54 therethrough. The bore 54 accommodates various electrical components and connections, which are not shown or described for clarity. The shaft 50 further defines an upper portion 56 configured to be coupled to the hub 40, which will be described in more detail below. Moreover, the length of the shaft 50 in one embodiment of the present disclosure is approximately five times the length of the hub 40.

[0032] 7-11 and 3, the upper and lower bonding layers are illustrated and described in more detail. In one embodiment, at least one of the upper and lower bonding layers is formed from a foil preform, which in this embodiment is aluminum. Moreover, the aluminum in one embodiment has a relatively high purity (at least about 99.99% pure Al). In the illustrated variation, an upper aluminum preform 60' is disposed between the substrate 30 and the hub 40. A lower aluminum preform 60'' is disposed between the hub 40 and the shaft. The aluminum foil preforms 60' / 60'' are formed to generally follow the surface profiles of the upper and lower surfaces of the hub 40, respectively. Moreover, the aluminum foil preforms 60' / 60'' also include various openings for accommodating the aforementioned electrical components / connections, in addition to the alignment features. In one embodiment, the surface area of ​​the upper aluminum foil preform 60' is less than the total surface area of ​​the top surface of the upper portion 42 of the hub 40. In yet another embodiment, the surface area of ​​the lower aluminum preform 60'' is less than the total surface area of ​​the bottom surface of the lower portion 44 of the hub 40. By way of example, the surface area of ​​the aluminum foil preform 60' / 60'' is approximately 50% less in one embodiment of the present disclosure. These reduced surface areas reduce the CTE (coefficient of thermal expansion) mismatch between the material of the hub 40 and the adjacent shaft 50 and substrate 30, reducing thermal stresses. Additionally, in the illustrated embodiment, the upper and lower aluminum foil preforms 60' / 60'' are approximately 0.008 inches thick. However, materials other than aluminum and materials of different thicknesses may be employed within the scope of the present disclosure.

[0033] The upper and lower bonding layers shown and described herein form hermetically sealed interfaces between the substrate 30 and the hub 40, and between the hub 40 and the shaft 50. Typically, the seals are hermetically sealed to meet the application requirements within the processing chamber. The hermeticity, or leak rate, in one form is about 1×10 -6atm cc / sec (standard cubic centimeters per second) He. In another form, the leak rate is about 1×10 -7 atm cc / sec He. In yet another embodiment, the leak rate is less than about 1×10 -9 atm cc / sec He.

[0034] 10 and 11, in addition to the aluminum foil preform 60' / 60'' described above, at least one of the upper and lower bonding layers further includes a material 64 sputtered onto the surfaces of the upper portion 42 of the hub 40 and the lower portion 44 of the hub 40, respectively. The sputtered material 64 in one form is a relatively high purity (at least about 99.99% pure Al) aluminum material, approximately a 2 μm thick layer. The sputtered material 64 is provided to promote wetting of the aluminum preform 60' / 60'' to the substrate 30 and shaft 50, respectively.

[0035] As further shown, the surfaces of the upper and lower portions 42, 44 of the hub 40 include a plurality of mesas 46. The mesas 46 are provided to control bondline thickness or to provide consistent spacing between the hub 40 and the shaft 50 and between the hub 40 and the substrate 30. In this embodiment, a total of three mesas 46 are equally spaced around the circumference of the upper and lower surfaces of the hub 40. However, it should be understood that fewer or more than three mesas 46 may be used in various spacing configurations while remaining within the scope of this disclosure. In one embodiment, the mesas 46 have a height of about 0.0055 inches to 0.0075 inches and a diameter of about 0.100 inches. The mesas 46 may take other shapes besides circular / cylindrical while remaining within the scope of this disclosure. In one embodiment, the mesas 46 are formed by selectively removing material from the hub 40.

[0036] As shown in FIG. 7, the upper portion 56 of the shaft 50 includes a raised region 58 shaped to match the shape of the lower aluminum preform 60″. The raised region also serves to reduce the bond surface area to reduce the effects of CTE (coefficient of thermal expansion) mismatch as discussed above.

[0037] For the upper bonding layer as shown and described herein, the upper portion 42 of the hub 40 is spaced a nominal distance from the lower surface of the substrate 30. Similarly, for the lower bonding layer, the lower portion of the hub 40 is spaced a nominal distance from the upper surface of the shaft 50. In one form, rather than forming a mesa, a number of preform pieces (not shown) are disposed between the upper portion of the hub 40 and the lower surface of the substrate 30 and / or between the lower portion of the hub 40 and the upper surface of the shaft 50. In one form, the preform pieces are beaded. However, other shapes are possible within the scope of this disclosure. Additionally, the preform pieces may be any of a variety of materials, such as aluminum or zirconia.

[0038] 12, another form of the hybrid shaft assembly 20 includes a secondary shaft element 51 secured to a lower portion 59 of the shaft 50. The secondary shaft element 51 may be bonded to the shaft 50 and to the substrate 52 using any of the methods specifically described herein. The secondary shaft element 51 is made of a material that has a lower thermal conductivity than the material of the shaft 50. This provides an additional means for reducing heat loss through the shaft 50. For example, the secondary shaft element 51 may be a zirconia material.

[0039] In yet another embodiment, the shaft 50 may be constructed of a variable composition material, which reduces the thermal conductivity from the upper portion 56 of the shaft 50 to the lower portion 59 of the shaft 50. In one form, the thermal conductivity decreases continuously from the upper portion 56 of the shaft 50 to the lower portion 59 of the shaft 50. In another form, the thermal conductivity decreases zone by zone from the upper portion 56 of the shaft 50 to the lower portion 59 of the shaft 50. In yet another embodiment, the reduced thermal conductivity can be achieved by varying the geometry of the shaft 50, such as having a larger diameter or circumference at the upper portion 56 and a smaller diameter or circumference at the lower portion 59. The change in geometry can be continuous or can be a discontinuous zone. The change in geometry can also be combined with a varying composition material while remaining within the scope of the present disclosure.

[0040] The hybrid shaft assembly can be joined in a variety of ways, including, but not limited to, brazing, solid-state / diffusion bonding, or transient liquid phase bonding, while remaining within the scope of the present disclosure. As used herein, it is understood that brazing is a method in which the temperature of the material of the joining layer exceeds its liquidus temperature. "Solid-state" bonding means that the temperature of the material of the joining layer is kept below its liquidus temperature during the application of heat and pressure during the joining process. Solid-state bonding is sometimes also referred to as diffusion bonding. However, the teachings of the present disclosure do not necessarily require that the material of each joining layer diffuse into the substrate, hub, or shaft material. Additionally, it is understood that "liquid phase" as used herein should be interpreted to include transient liquid phase bonding.

[0041] 13, and also FIGS. 3, 10, and 11, one method of forming the hybrid shaft assembly 20 is shown in more detail. First, material 64 is sputtered onto the surface of the upper portion 42 of the hub 40 and onto the surface of the lower portion 44 of the hub 40. Next, an aluminum preform 60' / 60'' is placed onto the sputtered surface of the hub. The substrate 30, hub 40, and shaft 50 are then assembled together and placed into a vacuum furnace, with the substrate 30 on the bottom and the substrate 52 of the shaft 50 on the top. In one embodiment, a weight of about 2 pounds is placed on the substrate 52 of the shaft 50 to stabilize the assembly. The hybrid shaft assembly 20 is processed in the vacuum furnace for a predetermined time, temperature, and pressure. In one embodiment, the temperature is about 850° C., the dwell time is about 20 minutes, and the pressure is about 1×10 -6 psi, although it should be understood that the time, temperature, and pressure will vary as a function of the materials and geometry of the hybrid shaft assembly 20. As such, these treatment values ​​are merely exemplary and are not limiting of the present disclosure.

[0042] Unless otherwise expressly stated herein, all numerical values ​​expressing mechanical / thermal properties, composition percentages, dimensions and / or tolerances, or other properties, in describing the scope of this disclosure, are understood to be modified by the words "about" or "approximately." This variation may be desirable for a variety of reasons, including industrial practices, material, manufacturing, and assembly tolerances, and testing capabilities.

[0043] As used herein, the phrase "at least one of A, B, and C" should be interpreted as meaning the logical (A OR B OR C) using a non-exclusive logical OR, and not as meaning "at least one of A, at least one of B, and at least one of C."

[0044] The description of the present disclosure is merely exemplary, and therefore variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. For example, in some applications, the thermal conductivity may be controlled in an opposite manner, such as being higher in the lower portion of the shaft. Furthermore, the thermal conductivity can be changed in any geometric dimension and in any positive or negative direction using the teachings herein. Such variations are not considered to depart from the spirit and scope of the present disclosure.

Claims

1. 1. A hybrid shaft assembly for use in a controlled atmosphere chamber, said hybrid shaft assembly comprising: A substrate; a hub having an upper portion and a lower portion, the upper portion being secured to the substrate by an upper bonding layer; a shaft secured to the lower portion of the hub by a lower bonding layer; Equipped with A hybrid shaft assembly, wherein the shaft is constructed from a material that has a lower thermal conductivity than a material of the hub and a material of the substrate.

2. 2. The hybrid shaft assembly of claim 1, wherein at least one of the upper bonding layer and the lower bonding layer is comprised of material sputtered onto a surface of the upper portion of the hub and the lower portion of the hub, respectively.

3. The hybrid shaft assembly of claim 2 , wherein the sputtered material forms a layer approximately 2 μm thick.

4. The hybrid shaft assembly of claim 1 , wherein at least one of the upper and lower portions of the hub is comprised of a plurality of mesas.

5. The hybrid shaft assembly of claim 1 , wherein the upper portion of the hub is spaced a nominal distance from a lower surface of the substrate.

6. The hybrid shaft assembly of claim 5 , further comprising a plurality of preform pieces disposed between the upper portion of the hub and the lower surface of the base plate.

7. The hybrid shaft assembly of claim 6 , wherein the preform piece comprises a zirconia material.

8. The hybrid shaft assembly of claim 1 , wherein the lower portion of the hub is spaced a nominal distance from an upper surface of the shaft.

9. The hybrid shaft assembly of claim 8 , further comprising a plurality of preform pieces disposed between the lower portion of the hub and the upper surface of the shaft.

10. The hybrid shaft assembly of claim 9 , wherein the preform piece comprises a zirconia material.

11. The hybrid shaft assembly of claim 1 , wherein the upper portion of the hub includes a radical flange.

12. The hybrid shaft assembly of claim 1 , wherein the hub is integral with the substrate.

13. The hybrid shaft assembly of claim 1 , wherein at least one of the upper bonding layer and the lower bonding layer is formed from an aluminum foil preform.

14. The hybrid shaft assembly of claim 13 , wherein a surface area of ​​the aluminum foil preform is less than a total surface area of ​​a top surface of the upper portion of the hub.

15. The hybrid shaft assembly of claim 13 , wherein a surface area of ​​the aluminum foil preform is less than a total surface area of ​​a lower surface of the lower portion of the hub.

16. 16. The hybrid shaft assembly of claim 14 or 15, wherein the surface area of ​​the aluminum foil preform is reduced by about 50%.

17. The hybrid shaft assembly of claim 13 , wherein the aluminum foil preform is approximately 0.008 inches thick.

18. The substrate is an AlN material, the hub is an AlN material, and the shaft is an Al ２ O ３ The hybrid shaft assembly of claim 1 , wherein the material is

19. a secondary shaft element secured to a lower portion of the shaft; The hybrid shaft assembly of claim 1 , wherein the secondary shaft element comprises a material having a lower thermal conductivity than a material of the shaft.

20. The hybrid shaft assembly of claim 1 , wherein the shaft is made of a material having a decreasing thermal conductivity from an upper portion to a lower portion of the shaft.

21. 21. The hybrid shaft assembly of claim 20, wherein the thermal conductivity of a material of the shaft decreases continuously from the upper portion to the lower portion of the shaft.

22. 2. The hybrid shaft assembly of claim 1, wherein the thermal conductivity of the shaft material is an order of magnitude lower than the thermal conductivity of the hub material and the substrate material.

23. The hybrid shaft assembly of claim 1 , wherein the upper and lower bonding layers form a hermetically sealed interface.

24. The leakage rate of the hermetically sealed interface is about 1×10 －６ 24. The hybrid shaft assembly of claim 23, wherein the hybrid shaft assembly has a flexural strength of less than atm cc / sec He.

25. The hybrid shaft assembly of claim 1 , wherein the length of the shaft is approximately five times the length of the hub.

26. The hybrid shaft assembly of claim 1 further comprising at least one electrical functional element embedded within the substrate.

27. 27. The hybrid shaft assembly of claim 26, wherein the at least one electrical functional element is selected from the group consisting of a heater, an RF antenna, and a clamp electrode.

28. the upper portion is a flanged upper portion; each of the flanged upper portion and the lower portion defines a plurality of mesas and includes a sputtered layer of aluminum; the upper bonding layer and the lower bonding layer each contain an aluminum brazing material having an aluminum content of 99.99%, The hybrid shaft assembly of claim 1 , wherein the aluminum braze material is formed from an aluminum foil preform.

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