TW202230561A - Degas chamber lift hoop - Google Patents

Abstract

A lift hoop is provided which includes a frame having a central opening, and a plurality of wafer support structures disposed on the frame. Each of the plurality of wafer support structures includes a base which is attached to the frame, and fingers which are mounted with threaded fasteners to the base and which extends from the base in the direction of the central opening. Each of the plurality of fingers is equipped with a protrusion (bump) upon which a wafer sits, and a stop. The stop is spaced apart from the protrusion. The stop has a non-planar surface which faces the central opening, and contains a point that forms the shortest distance between the stop and the protrusion. At least one of said protrusion and said stop have a surface roughness of less than 20 Ra.

Description

Degassing chamber lift hoop

The present application relates generally to robotic lift assemblies, and more particularly, to lift hoop assemblies equipped with a plurality of fingers to lift and transfer wafers.

Degassing chambers are known in the art to which this invention pertains and are a common tool in semiconductor fabrication equipment. Degassing chambers are used to perform vacuum degassing, a process in which a vacuum (usually combined with thermal cycling) is used to remove gases that have been trapped in semiconductor wafers during fabrication.

An example of a prior art degassing chamber is disclosed in US Pat. No. 6,182,376 (Shin et al.), which is shown in FIGS. 1-3 herein. The degassing chamber 11 shown therein includes a vacuum chamber 13 containing a heated substrate support 15 . An air inlet 17 is provided which fluidly connects the vacuum chamber 13 to a source 19 of drying gas. A gas outlet 21 is provided, which fluidly connects the vacuum chamber 13 to the gas pump 23 .

Wafer 25 is shown mounted on heated substrate support 15 . A plurality of pins 27 are positioned under the wafer 25 to facilitate gas flow along the backside of the wafer 25 and reduce contact between the wafer 25 and the substrate support 15, thereby reducing particle generation caused by such contact . The positioning of the plurality of pins 27 is best understood with reference to FIG. 2 .

To easily place and remove wafers from the heated substrate support 15, conventional wafer lift hoops 29 are employed. The operation of such a lifting hoop is known in the art to which the present invention pertains. The wafer lift ferrule 29 is equipped with three fingers 29a-c extending below the wafer. This configuration is intended to minimize particle generation while limiting wafer contact to the area above the three fingers 29a-c. More specifically, the fingers 29a-c extend upwardly from the wafer lift hoop 29 and have a wafer carrier portion 30 that preferably extends inward a horizontal distance of between 0.030-0.050 inches .

In addition to extending below wafer 25, fingers 29a-c also include sides 31a-c (see FIG. 2), respectively, that extend along the edge of wafer 25. The configuration of the sides is intended to reduce the generation of particles that may occur in contact therewith. In particular, the sides are sloped to avoid contact with the edge of the wafer 25 when the wafer 25 is placed on or removed from the wafer handler (not shown). Similarly, to reduce contact between wafer holder portion 30 and the backside of wafer 25, fingers 29a-c have sloped lower portions 33 that are angled from wafer holder portion 30 at an angle greater than or equal to 10° Lean away. Thus, if the wafer 25 would slide off the wafer holder portion 30, the wafer 25 would be supported by the sloping lower portion 33, thereby preventing the wafer from falling off the apparatus. Thus, even after the wafer lift hoop 29 is lowered (and the horizontal portions of the fingers 29a-c are received in appropriately positioned recesses in the surface of the substrate support 15), the side portions of the fingers 29a-c 30a-c can still pick up the wafer. This arrangement is intended to prevent the wafer from being off-center or off the substrate support 15 .

In one aspect, there is provided a lift hoop comprising: (a) a frame having a central opening; (b) a plurality of wafer support structures disposed on the frame, wherein the Each of the plurality of wafer support structures includes a pedestal attached to the frame, and a finger attached to the pedestal and extending from the central opening in the direction of the central opening. the base extends; (c) a protrusion disposed on each of the fingers; and (d) a stop disposed on each of the fingers and spaced from the protrusion , the stopper has a non-planar surface which faces the central opening and which includes a point that forms the shortest distance between the stopper and the protrusion; wherein the protrusion and the stopper At least one of them has a surface roughness of less than 20 Ra.

In another aspect, a method for making a lift hoop is provided. The method includes: (a) providing a frame having a central opening; (b) thermally annealing the frame while applying pressure to the frame; (c) releasably attaching a plurality of wafer support structures attached to the frame, wherein each of the plurality of wafer support structures includes: (a) a base removably attached to the frame; (b) a finger, it is attached to the base and extends from the base in the direction of the central opening, (c) a protrusion provided on the finger, and (d) a stop, It is disposed on the finger and is spaced from the protrusion; wherein at least one of the protrusion and the stop has a surface roughness of less than 20 Ra.

In another aspect, a method for aligning an end effector blade with a degassing chamber is provided. The method includes: (a) providing an end effector blade having a locking hole disposed therein; (b) providing a degassing chamber having a lift collar and a heater bracket, wherein, The heater bracket has a flat surface with a centrally located hole therein, and wherein the lift hoop includes a frame with a central opening, and a plurality of wafer support structures disposed in the on the frame, wherein each of the plurality of wafer support structures includes a base attached to the frame, and a finger attached to the base, and extending from the base in the direction of the central opening, and wherein each of the plurality of wafer support structures further includes a protrusion disposed on the fingers; (c) providing a securement A device having a central hub having a plurality of arms extending therefrom, wherein the hub has a central bore therein, and wherein each of the plurality of arms is at an end portion thereof having a peripheral hole; (d) placing the fixture on the lift hoop such that each of the peripheral holes engages a protrusion of one of the fingers and so that the center in the fixture holes aligned coaxially with the centrally located hole in the heater bracket; and (e) manipulating the position of the end effector until a pin inserted through the central hole of the hub passes through the end A locking hole in the actuator blade and into a centrally located hole in the heater bracket; wherein the protrusion has a surface roughness of less than 20 Ra, preferably less than 15 R, and most preferably less than 10 Ra.

While the device depicted in Figures 1-3 may have some desirable attributes, it also has a number of weaknesses. Many of these weaknesses are due to the lifting hoops used in them.

For example, the wafer gripping area formed by the three lift fingers of the lift collar is very tight. In many 300mm wafer implementations, the wafer gripping area is only about 0.63mm larger than the wafer itself. It has been found that this already limited wafer gripping area will shrink further due to thermally induced warpage in the lift collar.

Furthermore, although the device depicted in Figures 1-3 is designed to minimize particle generation, in practice it has been found that the device may still contain a number of features that significantly facilitate particle generation. For example, the inward facing walls of the fingers on the device are provided with flat surfaces that make significant contact with the edge of the wafer. Similarly, the fingers are equipped with protrusions on which the wafer is placed. However, both surfaces typically have relatively rough machined surfaces, which exacerbate particle generation.

Finally, the standard operating procedure (SOP) for aligning the lifting cuff depends on the technician's vision. This was found to result in frequent wafer misalignment and frequent contact between the wafer and the finger walls of the lift collar, which in turn resulted in more particle generation.

It has now been discovered that the apparatus and methods disclosed herein can overcome some or all of the aforementioned weaknesses. These devices and methods can be understood with reference to the embodiments depicted in the figures herein.

FIG. 4 depicts a specific non-limiting embodiment of a lift cuff in accordance with the teachings herein. As seen therein, the illustrated lift hoop 101 includes a frame 103 having a (preferably circular) central opening 105 therein. A plurality of wafer support structures 107 are arranged on the frame around the periphery of the central opening.

Wafer support structure 107 is shown in more detail in Figures 12-16. As seen therein, each wafer support structure 107 has a base 121 with fingers 123 protruding from the base 121 toward the central opening 105 (see FIG. 4 ). Base 121 is preferably releasably attached to frame 103 (see FIG. 4 ) by one or more screws or other suitable fasteners. Each finger 123 is provided on its distal end with a (preferably hemispherical) protrusion 125 which supports the wafer. Each finger 123 is also equipped with a stop 127 spaced from the protrusion 125 .

The stops 127 of the wafer support structure 107 have (preferably non-planar) contact surfaces 131 . In the particular embodiment shown, the contact surface 131 is beveled or faceted, although in other embodiments it may be rounded. Preferably, however, the contact surface 131 includes a point or location that forms the shortest distance d (see FIG. 15 ) between the stopper and the protrusion, and serves as a wafer contact surface (note that This point or location will typically lie in a plane tangent to protrusion 125 and intersecting contact surface 131 of stop 127). Without wishing to be bound by theory, it is believed that using this type of contact surface 131 reduces particle generation by providing a smaller contact area with the wafer in contact with the stopper 127 .

FIGS. 17-21 illustrate another embodiment of a wafer support structure 207 that may replace the wafer support structure 107 of FIGS. 12-16 in certain applications. Like the wafer support structure 107 of Figures 12-16, the wafer support structure 207 of Figures 17-21 includes a base 221 having fingers 223 extending therefrom. Each finger 223 is provided thereon with a protrusion 225 that supports the wafer. However, unlike the hemispherical protrusions in the wafer support structure 107 of Figures 12-16, in the wafer support structure 207 of Figures 17-21 the protrusions 225 take the form of ridges. Each finger 223 is also equipped with a stop 227 spaced from the protrusion 225 . The stop 227 of the wafer support structure 207 has a (preferably non-planar) contact surface 231 . In the particular embodiment shown, the contact surface 231 is beveled or faceted, although in other embodiments it may be rounded.

6 and 9 provide a comparison between the wafer support structure 107 of FIGS. 12-16 (see FIGS. 6A and 9A ) and the prior art wafer support structure 57 (see FIGS. 9A and 9B ). The wafer support structure 57 of FIG. 9B is similar to the wafer support structure shown in FIG. 2, but it is slightly different. As shown in FIG. 9, in the lift hoop 101 of FIG. 4, the spacing between the contact surfaces 131 of the protrusion 125 and the stop 127 (see FIG. 9A) is greater than the spacing between the protrusion 65 and the stop 67 in the prior art. In the particular embodiment illustrated, the difference is approximately 2.25 mm.

As shown in Figure 5, this difference in spacing has a significant impact on the wafer gripping area of the lift ferrule. Thus, while the lift hoop 51 of FIG. 9B has a wafer gripping area 104 of about 300.63 in diameter (which is very close to a wafer diameter of 300 mm +/- 0.2 mm), the lift hoop 101 of FIG. 9A has a diameter of about 304.10 mm Wafer gripping area 102, thereby creating more than 6 times the radial play of the lift hoop. It has been found that the increase in the wafer gripping area provided by the lift hoop 101 of FIG. 9A greatly reduces the contact between the stop 127 and the wafer, thereby reducing particle generation, while also allowing for smooth wafer handover and wafer handling. Hassle-free wafer handling. .

Referring again to FIG. 9 , while the stop 67 of the wafer support structure 57 of FIG. 9B has a flat contact surface 71 , conversely, the stop 127 of the wafer support structure 107 of FIG. 9A has a non-planar contact surface 131 . The non-planar surface may be rounded, beveled or faceted, but preferably contains the point that forms the shortest distance between the stop and the protrusion. Without wishing to be bound by theory, it is believed that the use of non-planar surfaces reduces particle generation by providing a smaller contact area with the wafer in contact with the stopper 127 .

The non-planar contact surfaces 131 of the stops 127 and the surfaces of the protrusions 125 on the wafer support structure 107 of FIG. 9A are preferably smooth. Preferably, the surfaces have a surface roughness measured by ASME B46.1 in the range of about 20 Ra to about 40 Ra, more preferably in the range of about 25 Ra to about 35 Ra, most preferably is about 32 Ra. This is in contrast to the corresponding surface of the support structure 57 of Figure 9B, which is significantly rougher. Without wishing to be bound by theory, it is believed that this difference in surface roughness further minimizes particle reduction in the devices and methods described herein.

Figures 7-8 illustrate other advantages of preferred embodiments of a lift hoop of the type described herein, and methods of making the same. Since the lift hoop is designed to be used in the degassing chamber, significant thermal gradients are encountered during normal use. However, it has been found that the effects of these thermal gradients are not properly considered in the manufacture of the lift collar. Thus, as shown in Figure 7, it is often observed that the prior art lift hoop undergoes significant deformation throughout the thermal cycle (dotted line indicates the original position of the lift hoop). As seen in Figure 7, this often results in wrinkling of the lifting hoop, a phenomenon known in the art to which this invention pertains as "potato chipping". This thermally induced deformation can significantly reduce the wafer gripping area, can adversely affect the accuracy of wafer placement during wafer handling and handover operations, and thus can contribute to wafer contact and particle generation.

It has now been found that this thermally induced deformation can be significantly reduced or eliminated by thermally annealing the lift collar under pressure. This can be accomplished, for example, by placing the lift hoop (with wafer support structures removed) between pneumatic clamps and then exposing the clamped lift hoop to one or more suitable thermal cycles. This thermal cycle is preferably similar to or greater than that encountered during a typical degassing process (eg, 200-450°C) to lift the hoop. Notably, this process is facilitated by the ability to remove wafer support structures. In contrast, in OEM equipment, the wafer support structure is welded to the lift collar. Therefore, even if the OEM equipment is subjected to thermal annealing, the presence of permanently attached wafer support structures can interfere with the process. Furthermore, if the wafer support structure is soldered after thermal annealing, some or all of the benefits of thermal annealing may be lost, eg, due to recrystallization of constituent metal alloys during the soldering operation.

As shown in Figure 8, this thermal annealing process was found to significantly reduce the thermal deformation of the entire lift hoop. Accordingly, the graphs depicted therein provide a measure of thermal deflection of an OEM lift cuff and a lift cuff subjected to the thermal annealing process described herein. As seen therein, significant improvements were observed at every point of the lift hoop, and an overall 76% reduction in heat-induced deflection was observed.

Another problem encountered with prior art lift hoop devices relates to alignment. During use, wafer handover takes place within the degassing chamber using an end effector. To ensure proper wafer handover and uniform wafer handling, it is important for the end effector blade to place the wafer in the center of the degassing chamber. This requires alignment of the geometric centers of the wafer blades, heaters, and lift ferrules. Currently, this is usually accomplished by using pins to align the end effector blades with the heater. In particular, the pin extends through a first hole located in the geometric center of the end effector blade into a second hole located in the geometric center of the heater. However, aligning the lift hoop with the end effector blades and heater relies on the operator's naked eye and thus cannot ensure repeatability. The situation is further complicated by the fact that the lift hoop is a complex 3D device equipped with a wafer support structure.

It has now been found that the above-mentioned problems can be overcome with the special fixture shown in Figure 11 . As shown, fixture 401 includes a plurality of arms 403 extending radially from central portion 405 . Each arm 403 has an end which is provided with a hole 406 . The central part 405 is equipped with a central hole 407 .

In use, when it is desired to align the end effector blades 411 with the degassing chamber heater bracket 413 and the lift hoop 415, place the fixture 401 on top of the lift hoop 415 such that the holes 401 on the arms 403 of the fixture Align with the protrusions on the wafer support fixture (see Figure 9A). Then, pins 421 (of the type used in OEM equipment to align end effector blades 411 with degassing chamber heater brackets 413 ) are passed through center holes 407 , through holes provided in end effector blades 411 . The hole 423 is inserted into and into a hole (not shown) provided in the degassing chamber heater bracket 413 . Using the fixture in this manner can simultaneously align the heater, end effector and lift collar with each other in one operation.

Another problem encountered with prior art lifting hoop arrangements relates to surface smoothness. In particular, the surface roughness (typically greater than 20 Ra) of the protrusions and blocks (see Figure 9) utilized in the protrusions 65 and blocks 67 in the prior art lift hoop 51 was found to produce significant particle debris. This debris creates substantial problems for semiconductor processing facilities and equipment. It has been found that by polishing these features such that one or both of the protrusions 65 and the stops 67 have a surface roughness of less than 20 Ra, more preferably less than 15 Ra, and most preferably less than 10 Ra, the resulting amount of particle debris.

The devices disclosed herein, and components or parts thereof, may have certain decorative, non-functional features suitable for protection by design. It will be understood by those of ordinary skill in the art to which this invention pertains that although these devices are shown in solid line drawings, various features in the drawings may not be claimed without departing from the scope of the invention (ie, may be described in design patents presented in a dashed line diagram in the application), or claimed without departing from the scope of this specification. Similarly, various combinations of these features may or may not be claimed in a design patent application without departing from the scope of this specification.

The foregoing description of the present invention is illustrative, not restrictive. Therefore, it will be understood that various additions, substitutions and modifications may be made to the above-described embodiments without departing from the scope of the present invention. Accordingly, the scope of the present invention should be construed with reference to the appended claims. It should also be understood that the various features set forth in the claims may be presented in various combinations and subcombinations in future claims without departing from the scope of the invention. In particular, this disclosure expressly contemplates any such combinations or subcombinations not known to the prior art, as if such combinations or subcombinations were expressly written.

11: Degassing chamber 13: Vacuum Chamber 15: Substrate support 17: Air intake 19: Drying gas source 21: Air outlet 23: Air pump 25: Wafer 27a: Pin 27b: pin 27c: Pin 29: Wafer Lift Hoop 29a: Fingers 29b: Fingers 29c: Fingers 31a: side 31b: side 31c: Lateral 33c: lower part 51: Lifting hoop 57: Wafer Support Structure 65: Protrusion 67: Stop 101: Lifting hoop 102: Wafer Pickup Area 103: Frames 104: Wafer Pickup Area 105: Central opening 107: Wafer Support Structure 121: Pedestal 123: Fingers 125: Protrusion 127: Stop 131: Contact Surface 207: Wafer Support Structure 221: Pedestal 223: Fingers 225: Protrusion 227: Stop 231: Contact Surface 401: Fixtures 403: Arm 405: Central Section 406: Hole 407: Center hole 411: End effector blade 413: Degassing chamber heater bracket 415: Lifting hoop 421: Pin 423: Hole d: shortest distance

[FIG. 1] is a side view of a prior art degassing apparatus. [ FIG. 2 ] is a partial side view that provides a closer view of the wafer lift ferrule of the degassing apparatus of FIG. 1 . [ Fig. 3 ] is a plan view of a substrate support of the degassing apparatus of Fig. 1 . [FIG. 4] is a perspective view of a specific non-limiting embodiment of a degassing chamber lift collar in accordance with the teachings herein. [FIG. 5] is a diagram of the wafer grabbing area of a degassing chamber lift ferrule according to the teachings herein, compared to prior art degassing chamber lift ferrules. [FIG. 6A] is a perspective view of a wafer grabbing arm showing a wafer mounted thereon in accordance with the teachings herein. [ FIG. 6B ] is a perspective view of a prior art wafer grabbing arm showing a wafer mounted thereon. [FIG. 7] is a diagram of thermally induced warpage in a prior art degassing lift hoop. [ FIG. 8 ] is a graph comparing the vertical deflection caused by heat in various components of the degassing chamber lift hoop of the prior art and the degassing chamber lift hoop according to the present application. [FIG. 9A] is a perspective view of a lift hoop finger wall design in accordance with the teachings herein. [FIG. 9B] is a perspective view of a prior art lift hoop finger wall design. [FIG. 10] is a perspective view of a fixture for aligning the heater, end effector and lift hoop with respect to each other. [ FIG. 11 ] is a perspective view showing the use of the fixture of FIG. 10 in the process of aligning the heater, the end effector and the lifting hoop with respect to each other. [ FIGS. 12-16 ] are perspective views of a first specific, non-limiting embodiment of a wafer support structure for a degassing chamber lift ferrule in accordance with the teachings herein. [ FIGS. 17-21 ] are perspective views of a second specific non-limiting embodiment of a wafer support structure for a degassing chamber lift ferrule in accordance with the teachings herein. [FIG. 22] is a top view of the degassing chamber lift hoop of FIG. 4 with the wafer support structure removed. [ FIG. 23 ] is a bottom view of the degassing chamber lift hoop of FIG. 22 . [Figs. 24-25] are perspective views of the degassing chamber lift hoop of Fig. 22. [Figs.

101: Lifting hoop

103: Frames

105: Central opening

107: Wafer Support Structure

Claims (20)

A lifting hoop comprising: a frame having a central opening; a plurality of wafer support structures disposed on the frame, wherein each of the plurality of wafer support structures includes a base attached to the frame, and a finger, it is attached to the base and extends from the base in the direction of the central opening; a protrusion disposed on the finger; and a stop positioned on the finger and spaced from the protrusion, the stop having a non-planar surface facing the central opening and including a point that forms the the shortest distance between the stopper and the protrusion; wherein at least one of the protrusion and the stopper has a surface roughness of less than 20 Ra. The lifting hoop of claim 1, wherein each of the protrusion and the stop has a surface roughness of less than 15Ra. The lifting cuff of claim 1, wherein each of the protrusion and the stop has a surface roughness of less than 10 Ra. The lifting cuff of claim 1 wherein the fingers extend over the central opening. The lifting hoop of claim 1, wherein the central opening is circular. The lifting hoop of claim 5, wherein the central opening has a circumference, and wherein the protrusions and stops are disposed within a straight cylinder containing the circumference. The lift hoop of claim 1, wherein each of the plurality of wafer support structures is removably attached to the frame. The lift hoop of claim 1, wherein the hoop is provided with an edge having a flat surface, and wherein each of the plurality of wafer support structures is removably attached to the the flat surface. The lifting hoop of claim 1, wherein the stops are sloped. The lifting hoop of claim 1, wherein the non-planar surface of the stopper is a multi-faceted surface comprising a first facet arranged at the second facet between the facet and the third facet. The lifting cuff of claim 1, wherein the non-planar surface of the stop is circular. The lifting cuff of claim 1, wherein each of the fingers has a proximal portion attached to the base and a distal end attached to the proximal portion spaced, and wherein the protrusions are disposed on the distal portion. The lifting cuff of claim 13, wherein the protrusions are hemispherical protrusions. The lifting cuff of claim 12, wherein the protrusion is a ridge having an axis parallel to a longitudinal axis of the fingers. The lifting cuff of claim 1, wherein the stop has a multi-faceted surface. In combination with the lifting hoop of claim 1, a semiconductor processing chamber is provided with a heating element and a bracket, wherein the lifting hoop is releasably attached to the heating element. The combination of claim 16, wherein the lifting collar is releasably attached to the heating element by a plurality of threaded fasteners. The lift hoop of claim 1 wherein the fingers are mounted on the base via threaded fasteners. The lift hoop of claim 1, wherein the lift hoop provides a wafer gripping area having a diameter greater than 301 mm. The lifting hoop of claim 1, which is combined with a semiconductor wafer, wherein the lifting hoop provides a wafer grabbing area, the diameter of the wafer grabbing area is at least 10 times larger than the diameter of the wafer 1 mm.

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