Boat system, retainer ring and use thereof

Abstract

A wafer boat system includes a carrier and a plurality of retainer rings configured to support wafers in the carrier. Each retainer ring has an annular body and a ring protrusion protruding from the annular body for contact with a wafer. At the ring protrusions, the local surface area of the ring body is smaller than the circumferential mean or median of the local surface area of the ring body, in particular to at least partially compensate for the surface area of the corresponding ring protrusions, thereby promoting the uniformity of vapor deposition on wafers supported on the retainer ring in the carrier. The reduced local surface area is preferably achieved by a relatively large inner diameter of the annular body at the ring protrusion. The carrier may provide a reference structure for automated wafer positioning.

Description

Technical Field

[0001] The present invention relates to a wafer boat system, and a retainer ring for such a wafer boat system, and to uses of the retainer ring and / or the wafer boat system. Background Art

[0002] Known wafer boats are therefore used for batch processing of semiconductor wafers, for example for vapor deposition on wafers. The wafer boat is usually a predominantly cylindrical structure in which a plurality of axially spaced circular wafers can be accommodated. The cylindrical axis of the wafer boat can be oriented vertically so that the wafers extend predominantly horizontally.

[0003] US 6,287,112 B1 explains the general problem of possible non-uniformity on the wafer surface when the process gas is supplied radially. In particular, so-called edge effects may occur, for example resulting in increased material deposition at the edge of the wafer compared to the center of the wafer. US 6,287,112 B1 also discusses the possible use of rings to increase uniformity. In some variants, the wafer may be supported on such a ring, so that the ring may be considered a retainer ring.

[0004] Although past developments have helped to improve deposition uniformity across the wafer surface, further improvements are needed. At the same time, it is desirable that wafer processing be efficient. Summary of the invention

[0005] In order to improve deposition uniformity on a wafer surface while maintaining or improving wafer processing efficiency, one aspect of the present invention provides a wafer boat system.

[0006] The wafer boat system includes a bracket, which includes a first end member located at a first axial end of the bracket, a second end member located at a second axial end of the bracket, and at least three axial rods spaced apart from each other, each axial rod connecting the first end member with the second end member, and each axial rod including a series of rod protrusions extending radially inward, the rod protrusions defining axially spaced retainer ring positions.

[0007] The wafer boat system includes a plurality of retainer rings, each retainer ring engageable with the rod protrusion to position the retainer ring in the carrier at one of the retainer ring positions, wherein when so engaged, at least when the axial rods are oriented vertically, the retainer rings are configured to support the wafer in the carrier,

[0008] Each retainer ring has an annular body and an annular protrusion projecting from the annular body, the annular protrusion being arranged to contact and space the wafer from the annular body when the wafer is supported by the retainer ring in the carrier.

[0009] Such ring protrusions are generally advantageous, particularly because they eliminate the need for the wafer to be in direct contact with the carrier, which would otherwise result in non-uniformity. At the same time, by spacing the wafer from the ring body, the ring protrusion allows the end effector of a wafer positioning robot to reach under the supported wafer without interference from the ring body.

[0010] However, it has been found that such annular protrusions themselves may also cause some inhomogeneities, wherein in particular the deposition on the wafer may be locally reduced in the region adjacent to such annular protrusions. The present invention is based on this recognition and also on the recognition that such inhomogeneities associated with the annular protrusions may be advantageously reduced by designing the annular body so as to at least partially compensate for the undesired deposition effects of the annular protrusions themselves, as described in detail below.

[0011] Preferably, the annular body has a local surface area that varies along its circumferential direction, wherein at the annular protrusions the local surface area of ​​the annular body is smaller than the circumferential average or median value of the local surface area of ​​the annular body, in particular in order to at least partially compensate for the surface area of ​​the corresponding annular protrusion. Thus, the uniformity of the vapor deposition on the wafer supported on the retainer ring in the carrier can be promoted.

[0012] It has been found that such at least partial compensation can advantageously lead to a more consistent, i.e., more evenly distributed, vapor deposition on the wafer, particularly near the annular protrusion. At the same time, the known advantages of the annular protrusion itself can be maintained or improved. In particular, since the annular protrusion separates the supported wafer from the annular body, the end effector can still move between the annular body and the wafer.

[0013] It has also been found that compensation can be achieved particularly effectively by locally increasing the inner diameter. Without wishing to be bound by theory, it is believed that this effect may be related to the fact that the inner diameter of the annular body is generally closer to the edge of the wafer, in particular closer than the outer diameter of the annular body.

[0014] In view of this, preferably, the annular body has an inner diameter that changes along its circumferential direction, wherein, at the annular protrusion, the inner diameter is larger than a circumferential average value or a median value of the inner diameter of the annular body.

[0015] A large inner diameter at the ring protrusion may result in a reduced local surface area, in particular in a manner that provides relatively effective compensation for the local deposition effect of the ring protrusion. At the ring protrusion, a relatively large inner diameter may therefore contribute to a relatively small local surface area as described above.

[0016] However, in some embodiments, some or all of the compensation, in particular the reduction of the local surface area of ​​the annular body, may be achieved other than by a locally increased inner diameter of the annular body, for example by a locally reduced outer diameter of the annular body and / or by one or more openings in the annular body between the inner diameter and the outer diameter.

[0017] The local surface area can be defined based on a circumferential window of 30 degrees or less, preferably 20 degrees or less, more preferably 10 degrees or less, such as about 5 degrees, about 2 degrees or about 1 degree. In this way, the value of the local surface area can be determined for substantially any circumferential position, including the circumferential position of the ring protrusion. It should be understood that determining such a value generally includes measuring and then summing up the surface areas of all surfaces of the annular main body portion within the circumferential window. By determining the value of the local surface area at regular circumferential intervals in this way, the average or median value of the local surface area can be calculated for the entire annular main body. As long as there is no gap between the windows, the windows of adjacent intervals may overlap or may not overlap each other.

[0018] It should be understood that the inner diameter of the annular body can be determined for any circumferential position. However, it should also be understood that any local expansion of the inner diameter will generally extend along a limited circumferential range or window. Therefore, a window-based approach similar to that described above can also be applied with respect to the inner diameter. Within such a window, the inner diameter is still variable, for example increasing toward the circumferential position of the annular protrusion, as described elsewhere herein.

[0019] On the other hand, a retainer ring is provided, which is apparently configured to be used as one of the retainer rings of the wafer boat system as described herein, wherein the retainer ring has an annular body and a ring protrusion protruding from the annular body, and the ring protrusion is arranged to contact the wafer and space the wafer from the annular body when the wafer is supported by the retainer ring.

[0020] Such a retainer ring may provide advantages corresponding to those described herein for a wafer boat system.The retainer ring may, for example, be used as a replacement for known retainer rings to form a wafer boat system in combination with known carriers.

[0021] The retainer ring and / or wafer boat system can advantageously be used to process wafers, wherein during processing, the wafers are in contact with the ring protrusions of the retainer ring supporting the respective wafers, preferably wherein the wafers are not in direct contact with the carrier. Processing can include vapor deposition. In specific applications, siloxane-based compounds are used in the vapor deposition.

[0022] The features of the dependent claims provide advantageous elaborations of the above-mentioned aspects and options, which will be further explained in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following, the invention will be further explained with reference to the examples of embodiments and drawings. The drawings are schematic and show only examples. The description of the embodiments here can also be understood independently of the drawings. In the drawings, corresponding elements have corresponding reference numerals. For the clarity of the drawings, an element may be indicated by a reference numeral only in one or some of the drawings and / or only for one or some of the multiple instances of an element in the drawings. In the drawings:

[0024] Figure 1 A perspective view of a retainer ring is shown;

[0025] Figure 2 A perspective view of the bracket is shown;

[0026] Figure 3 Shown with a wafer Figure 1 A top view of a retainer ring;

[0027] Figure 4 Shown with a wafer Figure 1 A side view of a retainer ring;

[0028] Figure 5 Shows Figure 3 Details of A;

[0029] Figure 6 Shows Figure 3 Details of B;

[0030] Figure 7a shows a perspective view of a retainer ring according to an embodiment of the present invention;

[0031] Figure 7b Shows Figure 1 A bottom view of a retainer ring;

[0032] Figure 8 Shows Figure 1 A portion of a retainer ring of and a cross-sectional side view of another similar retainer ring with Figure 2 a portion of a bracket;

[0033] Fig. 9 Shows Figure 2 A side view of the bracket;

[0034] Fig.10 Shows Fig. 9 Details of C;

[0035] Fig.11 Shows Fig. 9 Details of D;

[0036] Fig.12 A perspective view showing a possible variation of the retainer ring with the various parts of the bracket;

[0037] Fig.13 Shows Fig.12 A perspective view of the ring protrusion and associated portion of the retainer ring with a portion of the wafer;

[0038] Fig.14 Shown with Fig.12 a side view of the retainer ring of each portion of the carrier with the wafer; and

[0039] Fig.15 Shown is the representation with Figures 1 to 11 A graph of simulation results related to the crystal boat system. DETAILED DESCRIPTION

[0040] Figures 1 to 11 A portion of an example of the wafer boat system 1 is shown. Figures 12 to 14 A portion of another example of a wafer boat system 1 is shown. In the two examples, some geometric features of the ring protrusion 13 and the adjacent portion of the ring body 12 are different, as further explained elsewhere herein, while in other respects, the two examples are similar. A skilled person having the benefit of this disclosure will appreciate that further variations are possible.

[0041] The wafer boat system 1 includes a bracket 2, which includes a first end member 3 at a first axial end 4 of the bracket 2, a second end member 5 at a second axial end 6 of the bracket 2, and at least three axial rods 7 spaced apart from each other, each axial rod 7 connecting the first end member 3 with the second end member 5, and each axial rod 7 includes a series of rod protrusions 8 extending radially inward, and the rod protrusions 8 define axially spaced retainer ring positions 9.

[0042] The wafer boat system 1 includes a plurality of retainer rings 10, each of which is engageable with the rod protrusion 8 to position the retainer ring 10 in the carrier 2 at one of the retainer ring positions 9. When so engaged, the retainer rings 10 are configured to support wafers 11 in the carrier 2, at least when the axial rods 7 are oriented vertically.

[0043] Each retainer ring 10 has an annular body 12 and an annular protrusion 13 protruding from the annular body 12. When the wafer 11 is supported by the retainer ring 10 in the carrier 2, the annular protrusion 13 is arranged to contact the wafer 11 and to space the wafer 11, in particular axially, from the annular body 12. For example, the final axial distance between the annular body 12 and the wafer 11 may be about 4.5 mm.

[0044] As an example, Figures 3 to 4 and Figures 13 to 14 FIG. 1 shows how a wafer 11 can be supported by a retainer ring 10 , wherein the outline of the wafer 11 is indicated by a dot-dash line. Fig.14 In FIG. 1 , it can be seen how the retainer ring 10 can be supported simultaneously by the rod projections 8 of the axial rod 7 of the carrier 2 . Fig.14 The arrangement in can be repeated along the axial direction of the carrier 2, resulting in the carrier 2 comprising an axial series of retainer rings 10, each retainer ring 10 having a wafer 11 thereon, the wafer 11 being axially spaced from the annular body 12 of the retainer ring 10.

[0045] In an embodiment, the annular body 12 is an annular disc-shaped body 12 , ie the annular body 12 is substantially shaped as an annular disc.

[0046] Thus, the annular body 12 may be relatively flat and thin in the axial direction, such as being plate-like, while also helping to reduce edge effects during the handling of the wafers 11. The relatively thin annular body 12 advantageously enables a relatively large number of wafers 11 to be supported in the carrier 2 while being spaced apart from the annular body 12. The annular body 12 may be made sufficiently strong and rigid to provide a solid intermediate support structure between the rod protrusion 8 and the wafer 11. For example, the axial thickness of the annular body 12 may be about 1.75 mm.

[0047] Preferably, the annular body 12 has a local surface area that varies along its circumferential direction CD, wherein at the annular protrusions 13 the local surface area of ​​the annular body 12 is smaller than the circumferential average or median value of the local surface area of ​​the annular body 12, in particular in order to at least partially compensate for the surface area of ​​the respective annular protrusion 13. Thereby, the uniformity of the vapor deposition on the wafer 11 supported on the retainer ring 10 in the carrier 2 can be promoted.

[0048] Preferably, the annular body 12 has an inner diameter IR which varies along its circumferential direction CD, wherein at the annular protuberance 13 the inner diameter IR is larger than a circumferential average or median value of the inner diameter IR of the annular body 12 , in particular resulting in a reduced local surface area.

[0049] For example, in Figure 3 As can be seen in the diagram, the inner diameter IR has the same value along most of the circumference of the ring 10, but not all of it. Specifically, the inner diameter IR is locally increased here at the circumferential position CP13 of the ring protrusion 13. In addition, as described elsewhere herein, the inner diameter IR is locally reduced at the two portions 23. It should be understood that the ring protrusions 13 themselves are not considered to be part of the annular body 12, even though they may be formed integrally therewith. In view of this, when the inner diameter IR of the annular body 12 is measured at the ring protrusions 13, the ring protrusions 13 themselves are ignored.

[0050] At the annular protrusion 13, a relatively large inner diameter IR may contribute to a relatively small local surface area.

[0051] In an embodiment, the local surface area is defined based on a circumferential window CW of 30 degrees or less, preferably 20 degrees or less, and more preferably 10 degrees or less. At the same time, the circumferential window CW may be at least 1 degree, such as 2 degrees or 5 degrees. As an illustration of the concept of the circumferential window only, in Figure 3 1 has indicated such a window CW at an arbitrary circumferential position. It should be understood that such circumferential windows CW can be applied at regular intervals along the circumferential direction CD.

[0052] In an embodiment, at the annular protrusion 13 , the inner diameter IR of the annular body 12 is at least 1% larger than a circumferential average or median value of the inner diameter IR of the annular body 12 .

[0053] In this way, a particularly effective at least partial compensation can be achieved with respect to the annular projection. Figure 3 In the example shown, the inner diameter IR of the annular body 12 is increased by about 7% compared to the prevailing values ​​of the inner diameter IR, which in this case correspond to the circumferential mean or median value of the inner diameter IR of the annular body 12 .

[0054] In an embodiment, along a circumferential portion 14 of the annular body 12 adjacent to the annular protrusion 13 , the inner diameter IR of the annular body 12 increases toward a circumferential position CP13 of the annular protrusion 13 .

[0055] In this way, advantageously, the increase in the inner diameter IR can be relatively localized at the annular protrusion 13 without excessively reducing the local strength of the annular body 12 .

[0056] As an example, in Figure 6 As can be seen in FIG. 1 , here in the portion 14 adjacent to the annular protrusion 13, the inner diameter IR increases steadily towards the annular protrusion 13. Although a substantially linear or triangular increase is shown here, different types of increases are also possible. For example, in FIG. Figures 12 to 14 In the example of , the increase is substantially parabolic, the vertex of the parabola being arranged at the annular protrusion 13 .

[0057] In an embodiment, the increase in the inner diameter IR forms a distinct recess or notch at a circumferential portion 14 adjacent to the annular protrusion 13. The recess or notch may be distinguished in particular by having an edge, for example at a circumferential boundary of the portion 14, where the rate of change of the inner diameter along the circumferential direction CD may be discontinuous. Thus, the increase in the inner diameter IR may also be relatively well positioned at the corresponding annular protrusion 13. However, in some alternative embodiments, the increase in the inner diameter IR may form a smooth transition between the portion 14 and another portion further away from the annular protrusion 13.

[0058] In an embodiment, the annular protrusion 13 extends radially inwardly from the annular body 12 beyond a local inner diameter IR of the annular body 12 .

[0059] This configuration enables the retainer ring 10 to support the wafer 11 at a position radially inward from the inner diameter IR of the annular body 12. Advantageously, the wafer 11 can thus be supported slightly inward from its outer edge without the annular body 12 substantially overlapping the wafer 11. Furthermore, some tolerance in the lateral positioning of the wafer 11 can thereby be provided, if desired.

[0060] In an embodiment, the annular protrusion 13 is connected to the annular body 12 at and / or near the inner diameter IR of the annular body 12 .

[0061] Thus, the surface area of ​​the annular protrusion 13 can be kept relatively small, especially when the annular body 12 extends radially outward beyond the edge of the wafer 11, helping to reduce edge effects and forming a strong support structure.

[0062] In an embodiment, distal end 15 of annular protrusion 13 is radially inwardly and / or axially spaced from annular body 12, and is arranged to contact wafer 11 when wafer 11 is supported by retainer ring 10. Preferably, distal end 15 is radially inwardly and axially spaced from annular body 12.

[0063] By axially spacing the distal end 15 from the annular body 12, it is possible to facilitate the wafer 11 to be axially spaced from the annular body 12 when supported, and for the end effector to reach between the wafer 11 and the annular body 12 for automatic positioning of the wafer 11. The advantage of the distal end 15 being radially spaced from the annular body 12 corresponds to the advantage of the annular protrusion 13 extending radially inwardly beyond the local inner diameter IR of the annular body 12 described above.

[0064] In an embodiment, the proximal portion 16 of the annular protrusion 13 protrudes axially from the annular body 12, wherein the distal portion 17 of the annular protrusion 13 extends radially inwardly from the proximal portion 16 of the annular protrusion 13 at a distance from the annular body 12. An example of such a configuration can be Figures 12 to 14 Seen in.

[0065] In an embodiment, the proximal portion 16 of the annular protrusion 13 protrudes radially inward from the annular body 12, wherein the distal portion 17 of the annular protrusion 13 extends axially from the proximal portion 16 of the annular protrusion 13 at a distance from the annular body 12. An example of such a configuration can be Figure 1 , 3 , 4, 6, and 7a and 7b.

[0066] It has been found that the retainer ring 10 can be produced more economically in some cases with the latter geometric configuration of the ring protrusion 13, although the former variant is also technically and economically feasible. Further variations are possible, for example in which the ring protrusion 13 or at least a portion thereof extends at an oblique angle, in particular as an alternative to the relatively straight proximal and distal portions shown.

[0067] In an embodiment, when the retainer ring 10 engages with the rod protrusions 8 of the axial rods 7 of the carrier 2, the respective ring protrusions 13 are circumferentially spaced from the axial rods 7. This may be particularly applicable when the retainer ring 10 is fully accommodated in the carrier 2, so that each axial rod 7 engages with the retainer ring 10, in particular at a respective circumferential position CW7, which may be predetermined, for example, by the outer diameter or a variation of the outer diameter of the annular body 12, as explained elsewhere herein.

[0068] Therefore, it is advantageously possible to prevent the accumulation of local processing effects of the axial rod 7 and the annular protrusion 13. See, for example Fig.12 , where it can be seen that all three axial rods 7 are circumferentially spaced from all three ring protrusions 13. At the same time, it should be understood that the axial rods 7 and the ring protrusions 13 are preferably distributed substantially along the circumferential direction CD, and the axial rods 7 are arranged to allow the retainer ring 10 and the wafer 11 to be moved into and out of the carrier 2 in the lateral direction.

[0069] In an embodiment, the annular body 12 has an outer radius OR that varies along its circumferential direction CD, wherein the variation of the outer radius OR determines a respective rod position CP7 of the axial rod 7 along the circumferential direction CD of the annular body 12 .

[0070] In this way, a secure and reliable engagement between the annular body 12 and the axial rod 7 can be provided, in particular a reliable circumferential positioning of the annular protrusion 13 relative to the axial rod 7. The rod position CP7 is already Figure 1 and 3 It is shown in Fig.12 1 shows a portion of the axial rod 7 at a corresponding position of a variation of the retainer ring 10. At the rod position CP7, a corresponding recess 22 may be provided in the bottom surface of the annular body 12, for example Figure 7a and 7b as well as Figure 8 As shown, to further promote a secure and reliable engagement between the annular body 12 and the axial rod 7 (especially the rod protrusion 8 thereof).

[0071] In an embodiment, the variation in the outer diameter OR additionally provides a passage 18 for at least some of the axial rods 7 when the annular body 12 is moved into the carriage 2 to allow the axial rods 7 to assume a determined position.

[0072] Thus, the axial rods 7 can be relatively well distributed in the circumferential direction CD for a stable support of the retainer ring 10 , while the retainer ring 10 can still be moved into and out of the carrier 2 , in particular between the axial rods 7 providing the passages 18 therefor.

[0073] In an embodiment, the annular body 12 has an inner diameter IR varying along its circumferential direction CD, wherein at the passages 18 for at least some of the axial rods 7 the inner diameter IR is smaller than a circumferential average or median value of the inner diameter IR of the annular body 12 .

[0074] In this way, possible deposition effects of the channel 18 can be at least partially compensated. It has been found that such a reduction in the inner diameter IR can be relatively small, e.g. Figure 5When the axial rod 7 is in its end position CP7, the reduction in the inner diameter preferably does not overlap the axial rod 7 circumferentially to prevent the effects of the axial rod 7 and the reduced inner diameter from accumulating. At the same time, the reduction in the inner diameter IR preferably extends along the circumferential portion 23 corresponding to the corresponding channel 18, as shown. Figure 5 It will be appreciated that, at least in this respect, the passage 18 extends up to but not including the space occupied by the axial rod 7 when it is in its end position CP7.

[0075] refer to Figure 7a In an embodiment, the annular body 12 has an inner diameter IR that varies along its circumferential direction CD, wherein, at a circumferential position CP18 that at least partially overlaps with the end position CP7 of at least some axial rods 7, the inner diameter IR is larger than the circumferential average or median value of the inner diameter IR of the annular body 12.

[0076] In this way, possible depositing effects of the axial rod 7 can be at least partially compensated.The increase in the inner diameter IR preferably overlaps circumferentially with the axial rod 7 when positioned in its end position CP7.

[0077] In the examples, particular reference is made to Figures 9 to 11 , adjacent to at least one of the first end member 3 and the second end member 5, the respective first and / or second end portions 19, 20 of the axial rod 7 are sized to extend radially inwardly into the carrier 2 beyond the rod protrusion 8, thereby providing a reference structure 21 for the robot to automatically position the wafer 11 in the carrier 2 via the end effector. In an embodiment, the reference structure 21 defines a lateral component of a target wafer position in the carrier 2. In an embodiment, the reference structure 21 is sized to receive the wafer 11 therein without any retainer ring.

[0078] Such a reference structure 21 can advantageously enable a wafer positioning robot including an end effector to learn the correct lateral position of the wafer in the carrier 2, in particular by iteratively fully engaging a wafer or dummy wafer with the reference structure 21, while sensing or otherwise determining the full engagement and recording the corresponding position of the end effector. When the wafer is subsequently positioned in the carrier 2, the learned lateral wafer position can be applied to accurately position the wafer 11 on the retainer ring 10 in a substantially feed-forward manner, at least without the need to sense the lateral position of the wafer in the carrier 2 for each wafer in turn. In this sense, the reference structure 21 can be regarded as a calibration structure, and / or the associated procedure as described above can be regarded as a calibration procedure for such a wafer positioning robot.

[0079] The retainer ring 10 and / or the wafer boat system 1 described herein may be used for processing wafers 11, wherein during processing the wafers 11 are in contact with the ring protrusions 13 of the retainer ring 10 supporting the respective wafers 11, preferably wherein the wafers 11 are not in direct contact with the carrier 2. In an embodiment, the processing comprises vapor deposition, in particular using a siloxane-based compound such as Si3H8.

[0080] Fig.15 It shows that the Figures 1 to 11 The curve diagram of the simulation results of the computer model of the wafer boat system 1 shown in FIG. Figure 1 and Figures 3 to 8 The retainer ring 10 is shown. Fig.15 In the graph of FIG. 1 , the horizontal axis represents the circumferential position CP in degrees, wherein a value of zero here corresponds to Figure 3 The top of the position seen is CP7, and the value is Figure 3 The position CP7 of the rod 7 and the position CP13 of the ring protrusion 13 are in the Fig.15 The vertical dashed line represents the growth rate GR in terms of 100 pm (i.e. 1 angstrom) per minute. Fig.15 The data points shown in represent the growth rate at a specific circumferential position.

[0081] Based on simulated vapor deposition using Si3H8 as the siloxane-based compound, at a radial position 2 mm inward from the outer edge of the top side of the supported wafer, Fig.15 The growth rate data shown in are simulated. The resulting growth rate values ​​are between 19.76 and 20.09, i.e., in the range of 0.33, while the circumferential average of the growth rate GR is 20.0. Based on this, the remaining non-uniformity at the edge of the wafer can be said to be as low as (0.33 / 20.0=)1.65%. In contrast, for known wafer boat systems, values ​​of up to 7.5% for the same non-uniformity metric were found in corresponding simulations, indicating that the design according to the present invention can provide a significant improvement in uniformity. In particular, in Fig.15 As can be seen in FIG. 1 , the range of growth rate values ​​around the circumferential position CP13 of the ring protrusion is very small, since the effect of the ring protrusion 13 is at least partially compensated by the locally reduced surface area and / or inner diameter IR of the annular body 12 .

[0082] Although the present invention has been explained here using the examples of embodiments and drawings, these do not limit the scope of the present invention as determined by the claims. The skilled person who has benefited from this disclosure will understand that within the scope, many variations, combinations and extensions are possible. For example, the number of axial rods of the bracket and / or the number of ring protrusions of the retainer ring may be greater than three. All these variations are included within the scope of the present invention as defined by the claims.

[0083] Reference numerals list

[0084] 1Jingzhou System

[0085] 2 Bracket

[0086] 3First end member

[0087] 4 First axial end of the bracket

[0088] 5 Second end member

[0089] 6 Second axial end of the bracket

[0090] 7 Axial rod

[0091] 8-bar protrusion

[0092] 9 Retainer Ring Position

[0093] 10Retainer ring

[0094] 11 chips

[0095] 12 Ring body

[0096] 13 ring protrusion

[0097] 14 Circumferential portion adjacent to the ring protrusion

[0098] 15 Distal end of the protrusion

[0099] 16 Proximal part of the protrusion

[0100] 17 Distal part of the protrusion

[0101] 18 Channel for axial rod

[0102] 19 Axial rod first end portion

[0103] 20 Second end portion of the axial rod

[0104] 21 Reference Structure

[0105] 22 Recess in annular body for rod protrusion

[0106] 23 Circumferential portion with reduced inner diameter

[0107] CD Circumferential direction

[0108] CP circumferential position

[0109] CP7 rod position along the circumference

[0110] Circumferential position of CP13 ring protrusions

[0111] CW Circular Window

[0112] GR growth rate

[0113] Inner diameter of IR ring body

[0114] The outer diameter of the OR ring body

Claims

1. A wafer boat system, comprising: a carrier comprising a first end member at a first axial end of the carrier, a second end member at a second axial end of the carrier, and at least three mutually spaced axial rods, each axial rod connecting the first end member to the second end member, and each axial rod comprising a series of radially inwardly extending rod projections defining axially spaced retainer ring locations; and a plurality of retainer rings, each retainer ring engageable with the rod protrusion to position the retainer ring in the carrier at one of the retainer ring positions, wherein when so engaged, at least when the axial rods are oriented vertically, the retainer rings are configured to support the wafer in the carrier, wherein each retainer ring has an annular body and an annular protrusion protruding from the annular body, the annular protrusion being arranged to contact and space the wafer from the annular body when the wafer is supported by the retainer ring in the carrier, Therein, the annular body has a local surface area that varies along its circumferential direction, wherein at the annular protrusions the local surface area of ​​the annular body is smaller than the circumferential average or median value of the local surface area of ​​the annular body, in particular in order to at least partially compensate for the surface area of ​​the corresponding annular protrusion, thereby promoting uniformity of vapor deposition on a wafer supported on a retainer ring in a carrier.

2. The wafer boat system according to claim 1, wherein: The local surface area is defined based on a circumferential window of 30 degrees or less, preferably 20 degrees or less, more preferably 10 degrees or less.

3. The wafer boat system according to claim 1 or 2, wherein: The annular body has an inner diameter which varies along its circumference, wherein at the annular protrusion the inner diameter is larger than a circumferential average or median value of the inner diameter of the annular body, in particular wherein at the annular protrusion a relatively large inner diameter contributes to a relatively small local surface area.

4. A wafer boat system, comprising: a carrier comprising a first end member at a first axial end of the carrier, a second end member at a second axial end of the carrier, and at least three mutually spaced axial rods, each axial rod connecting the first end member to the second end member, and each axial rod comprising a series of radially inwardly extending rod projections defining axially spaced retainer ring locations; and a plurality of retainer rings, each retainer ring engageable with the rod protrusion to position the retainer ring in the carrier at one of the retainer ring positions, wherein when so engaged, at least when the axial rods are oriented vertically, the retainer rings are configured to support the wafer in the carrier, wherein each retainer ring has an annular body and an annular protrusion protruding from the annular body, the annular protrusion being arranged to contact and space the wafer from the annular body when the wafer is supported by the retainer ring in the carrier, Therein, the annular body has an inner diameter which varies in its circumferential direction, wherein at the annular projection the inner diameter is larger than the circumferential mean or median value of the inner diameter of the annular body, in particular resulting in a reduced local surface area.

5. The wafer boat system according to claim 3 or 4, wherein: At the annular protrusion, the inner diameter of the annular body is at least 1% larger than a circumferential average or median value of the inner diameter of the annular body.

6. The wafer boat system according to any one of claims 3 to 5, wherein: Along a circumferential portion of the annular body adjacent to the annular protrusion, an inner diameter of the annular body increases toward a circumferential position of the annular protrusion.

7. The wafer boat system according to any one of claims 3 to 6, wherein: The annular protrusion extends radially inwardly from the annular body beyond a partial inner diameter of the annular body.

8. The wafer boat system according to any one of the preceding claims, wherein: The distal end of the annular projection is spaced radially inwardly and axially from the annular body, the distal end being arranged to contact a wafer when the wafer is supported by the retainer ring.

9. The wafer boat system according to claim 8, wherein: The proximal portion of the ring protrusion protrudes axially from the ring body, wherein the distal portion of the ring protrusion extends radially inwardly from the proximal portion of the ring protrusion at a distance from the ring body.

10. The wafer boat system according to claim 8, wherein: The proximal portion of the ring projection protrudes radially inwardly from the ring body, wherein the distal portion of the ring projection extends axially from the proximal portion of the ring projection at a distance from the ring body.

11. The wafer boat system according to any one of the preceding claims, wherein: When the retainer ring engages the rod protrusions of the axial rod of the carrier, the corresponding ring protrusions are circumferentially spaced from the axial rod.

12. The wafer boat system according to any one of the preceding claims, wherein: The annular body has an outer radius that varies along its circumferential direction, wherein the variation of the outer radius determines the corresponding rod position of the axial rod along the circumferential direction of the annular body.

13. The wafer boat system according to claim 12, wherein: The annular body has an inner diameter which varies in its circumferential direction, wherein at the passages for at least some of the axial rods the inner diameter is smaller than a circumferential average or median value of the inner diameter of the annular body.

14. The wafer boat system according to claim 12, wherein: The annular body has an inner diameter which varies in its circumferential direction, wherein at circumferential positions at least partially overlapping end positions for at least some of the axial rods the inner diameter is larger than a circumferential mean or median value of the inner diameter of the annular body.

15. A wafer boat system, comprising: a carrier comprising a first end member at a first axial end of the carrier, a second end member at a second axial end of the carrier, and at least three mutually spaced axial rods, each axial rod connecting the first end member to the second end member, and each axial rod comprising a series of radially inwardly extending rod projections defining axially spaced retainer ring locations; and a plurality of retainer rings, each retainer ring engageable with the rod protrusion to position the retainer ring in the carrier at one of the retainer ring positions, wherein when so engaged, at least when the axial rods are oriented vertically, the retainer rings are configured to support the wafer in the carrier, wherein each retainer ring has an annular body and an annular protrusion protruding from the annular body, the annular protrusion being arranged to contact and space the wafer from the annular body when the wafer is supported by the retainer ring in the carrier, Wherein, adjacent to at least one of the first end member and the second end member, the corresponding first and / or second end portion of the axial rod is sized to extend radially inwardly into the bracket beyond the rod protrusion, thereby providing a reference structure for the robot to automatically position the wafer in the bracket via the end effector.

16. The wafer boat system according to claim 15, wherein: The reference structure defines a lateral component of a target wafer position in the carrier.

17. The wafer boat system according to claim 16, wherein: The reference structure is sized to accommodate a wafer therein without any retainer ring.

18. A retainer ring, which is apparently configured to be used as one of the retainer rings of a wafer boat system according to any one of the preceding claims, wherein the retainer ring has an annular body and an annular protrusion protruding from the annular body, and the annular protrusion is arranged to contact the wafer and space the wafer from the annular body when the wafer is supported by the retainer ring.

19. Use of a retainer ring according to claim 18 and / or a wafer boat system according to any one of claims 1 to 17 for processing wafers, wherein: During processing, the wafers come into contact with the ring protrusions of the retainer ring which support the respective wafers, preferably wherein the wafers are not in direct contact with the carrier.

20. The use according to claim 19, wherein The treatment involves vapor deposition, in particular using siloxane-based compounds.

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