Wafer boat for supporting semiconductor wafers within a furnace

Abstract

A wafer boat for supporting a plurality of semiconductor wafers within a furnace is disclosed. The wafer boat includes a set of fingers, each finger having a contact protrusion that contacts and supports a semiconductor wafer.

Description

[0001] Cross-citation of related applications

[0002] This application claims the rights of U.S. Provisional Patent Application No. 63 / 044,698, filed June 26, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a semiconductor wafer boat for supporting semiconductor wafers, and more specifically, to a semiconductor wafer boat for heat-treating semiconductor wafers in a furnace. Background Technology

[0004] Semiconductor wafers are typically heat-treated (i.e., annealed) at high temperatures to achieve certain desired properties. For example, annealing can be used to create a defect-free silicon layer on the wafer. The high-temperature annealing process is typically carried out in a vertical furnace, which exposes the wafer to temperatures above 1100°C (e.g., between about 1200°C and about 1300°C).

[0005] Multiple semiconductor wafers can be supported within the vertical furnace via wafer boats or "racks." The wafer boat includes one or more supports upon which the semiconductor wafers rest. During exposure to high temperatures (especially above 1100°C), the wafers temporarily become more ductile, i.e., their yield strength decreases. The contact areas supporting the wafers on the wafer experience slippage due to localized gravity and thermal stress. Slippage can introduce contaminants into the wafer. Furthermore, excessive slippage can lead to plastic deformation of the wafer, resulting in manufacturing problems, such as lithography overlay failures causing yield losses in device manufacturing.

[0006] Supports are designed to hold semiconductor wafers while minimizing localized gravity and thermal stress to prevent slippage and plastic deformation during heat treatment. Typically, wafer boats used in vertical furnaces comprise three or more rods. These rods have laterally extending fingers that are generally located on a common horizontal plane. This configuration is conventional and generally suitable for heating wafers with smaller diameters, such as 200 mm or less. Compared to smaller diameter wafers, larger diameter wafers (e.g., greater than 200 mm) experience greater localized weight and thermal stress. Such larger diameter wafers are conventionally loaded onto support rings that provide a larger surface area for support. These support rings increase the time required to load and unload semiconductor wafers onto the wafer boat.

[0007] A wafer boat is required that includes a support structure (which reduces local gravity and thermal stress to limit slippage of semiconductor wafers due to the high temperatures they experience during the annealing process) and a wafer boat with relatively high throughput for loading and unloading wafers.

[0008] This section aims to introduce the reader to various aspects of this technology, which may relate to the various aspects of this disclosure described and / or claimed below. This discussion is intended to help provide the reader with background information to facilitate a better understanding of the various aspects of this disclosure. Therefore, it should be understood that these statements should be read in this light and are not to be considered prior art. Summary of the Invention

[0009] One aspect of this disclosure relates to a wafer boat for supporting multiple semiconductor wafers within a furnace. The wafer boat includes a vertical rod and an assembly of fingers extending radially inward from the vertical rod. Each finger of the assembly includes an elongated segment extending from the vertical rod. Contact protrusions are disposed on the elongated segment toward the distal end of the finger to contact and support the semiconductor wafer. At least a portion of the contact protrusion protrudes relative to the elongated segment.

[0010] Various modifications exist relative to the features mentioned in the foregoing aspects of this disclosure. Further features may also be incorporated into the foregoing aspects of this disclosure. These modifications and additional features may exist individually or in any combination. For example, the various features discussed below with respect to any illustrated embodiment of this disclosure may be incorporated individually or in any combination into any of the foregoing aspects of this disclosure. Attached Figure Description

[0011] Figure 1 This is a perspective view of a wafer boat;

[0012] Figure 2 This is a top view showing the wafer boat with contact protrusions;

[0013] Figure 3 yes Figure 2 Detailed view of the contact protrusion shown in the image;

[0014] Figure 4 This is a detailed view of another embodiment of the contact protrusion; and

[0015] Figure 5 It is a probability diagram of the sliding lengths of the first and second lengths of the contact protrusion.

[0016] Throughout the accompanying drawings, corresponding component symbols indicate the corresponding parts. Detailed Implementation

[0017] An example wafer boat for supporting multiple semiconductor wafers within a vertical furnace. Figure 1The wafer boat 10 is typically referred to as "10". The wafer boat 10 supports multiple semiconductor wafers during high-temperature thermal processing (also referred to herein as "annealing"). The wafer boat 10 includes at least one vertical rod 12 (and typically three or more rods) coupled to a top 14 and a base 16 of the wafer boat 10. The wafer boat 10 includes a longitudinal central axis Y extending from the top 14 to the base 16. 10 Vertical rod 12 is arranged perpendicular to the longitudinal central axis Y. 10 Distance D1 ( Figure 1 ).

[0018] The illustrated wafer boat 10 includes three vertical rods 12, and more specifically, a central rod 18 and two front rods 20. Each of the vertical rods 12 is arranged around a longitudinal central axis Y. 10 On the first circle C1 centered at and having a radius R1 ( Figure 2 The two front rods 20 are arranged around the longitudinal central axis Y. 10 Separated by a first angle α1. The center rod 18 is spaced equidistantly from the two front rods 20 by a circular distance, such that the center rod 18 revolves around the longitudinal central axis Y. 10 The two front rods 20 are spaced apart by a second angle α2 relative to each of the two front rods 20. The two front rods 20 are spaced apart by a first angle α1, such that the inlet 24 ( Figure 1 The inlet 24 is defined between the two front rods 20. The first angle α1 can be any suitable angle such that the inlet 24 is sized to allow the semiconductor wafer to pass through the inlet 24 and be arranged within the internal space 26 of the wafer boat 10. For example, the first angle α1 can be 180° or greater, and the second angle α2 can be 90° or less.

[0019] The wafer boat 10 includes fingers 30 extending radially inward from vertical rods 12 to support a semiconductor wafer (i.e., the boat does not include a support ring for supporting the wafer). The two front vertical rods 20 each include a first set 36 and a second set 38 of fingers 30. The central vertical rod 18 includes a third set 40 of fingers 30. The first set 36 of fingers 30 extends along a first finger axis A. 36 The second set 38 of the extended finger 30 is along the axis A of the second finger. 38 The third set of fingers 40 extends along the third finger axis A. 40 Extension. Each finger-like axis A 36 A 38 A 40The finger 30 extends from its proximal end 32 to its distal end 34. The proximal end 32 of the finger 30 is close to the vertical rod 12, and the distal end 34 of the finger 30 is disposed within the internal space 26 of the wafer boat 10. The finger 30 may be integrally formed with the vertical rod 12, for example, by cutting in an elongated one-piece structure to form the finger 30. Alternatively, the finger 30 may be formed separately and coupled to the vertical rod 12.

[0020] Finger axis A of the first set 36 and the second set 38 of the finger 30 36 A 38 Each of them extends from the chord X of the first circle C1. 36 X 38 Above. String X 36 X 38 Not aligned with the longitudinal central axis Y of the wafer boat 10 10 Intersecting (i.e., the first set 36 and the second set 38 of the finger-like structures are not centered, so that they point towards the longitudinal central axis Y). 10 ). The third set of finger-shaped objects 30, the finger axis A of 40 40 Extending from the first circle C1 and the longitudinal central axis Y 10 Intersecting chords X 40 Above.

[0021] A group 42 of fingers 30 extending from each of the vertical rods 12 lies in the same generally horizontal plane so that the group 42 of fingers 30 can support a semiconductor wafer. The distal ends 34 of the fingers 30 in the group 42 lie on a second circle C2. The second circle C2 has a radius R2 and is centered on a longitudinal central axis Y. 10 Centered on the edge, radius R2 extends from the distal end 34 of the finger 30 to the longitudinal central axis Y of the wafer boat 10. 10 In the illustrated embodiment, each of the distal ends 34 of the fingers 30 in the group 42 is arranged at an equal circumferential distance from each of the other distal ends 34 of the other fingers 30 in the group 42. For example, in the illustrated embodiment comprising the first, second, and third sets 36, 38, and 40 of fingers 30, each of the distal ends 34 of the first, second, and third sets 36, 38, and 40 of fingers 30 is separated by an angle β, defined on the longitudinal central axis Y. 10 On the second circle C2 centered at the center. In the illustrated embodiment, angle β is 120°.

[0022] refer to Figure 3Each of the fingers 30 includes an elongated segment 50 extending from the vertical rod 12 and a contact protrusion 52 disposed on the elongated segment 50 toward the distal end 34 of the finger 30. The contact protrusion 52 contacts and supports the semiconductor wafer. The contact protrusion 52 protrudes relative to the elongated segment 50. The contact protrusion 52 has a first end 54, a second end 56, and a longitudinal contact protrusion axis A extending through the first end 54 and the second end 56 of the contact protrusion 52. 52 The contact protrusion 52 can be used to support wafers of any diameter, including wafers with a diameter of 200 mm, 300 mm and / or a diameter greater than 300 mm.

[0023] The described contact protrusion 52 is circular (e.g., along axis A). 36 (The height increases from each side to the apex). The circular contact protrusion 52 includes a surface that is generally cylindrical in shape. Each contact protrusion 52 includes a contact protrusion axis A along its longitudinal direction. 52 The extended length L1 and the width W1 perpendicular to the length L1. The wafer is typically along the longitudinal contact protrusion axis A. 52 It rests on the circular contact protrusion 52.

[0024] In some embodiments, the contact protrusion 52 has a width W1 of 3 mm to 20 mm, a length L1 of 10 mm to 50 mm, and a longitudinal central axis Y from the contact protrusion 52 to the wafer boat. 10 The distance can be from 75mm to 125mm. In some embodiments, the contact protrusion 52 has a width W1 of 8mm, a length L1 of 30mm, and extends from the contact protrusion 52 to the longitudinal central axis Y of the wafer boat 10. 10 The distance is 100mm.

[0025] In some embodiments (e.g.) Figure 4 In the embodiment shown, the contact protrusion 52 is flat. Similar to... Figures 1 to 3 The components Figure 4 The components shown in the middle are through Figures 1 to 3 The corresponding component symbol is designated by adding "100" (e.g., part 52 becomes 152). The flat contact protrusion 152 includes a contact surface having a shape extending along the longitudinal contact protrusion axis A. 152 The surface area is defined by the extended length L1 and the width W1 perpendicular to the length L2. The surface generally contacts the semiconductor wafer resting on the flat contact protrusion 152.

[0026] In some embodiments, the contact protrusion 152 has a width W1 of 3 mm to 20 mm and a length L1 of 10 mm to 50 mm, and the longitudinal central axis Y from the contact protrusion 152 to the wafer boat 10 is... 10The distance can be from 75mm to 125mm. Alternatively or additionally, the contact protrusion 152 has a width W1 of 8mm, a length L1 of 25mm, and extends from the contact protrusion 152 to the longitudinal central axis Y of the wafer boat. 110 The distance is 100mm. The wafer rests on the flat contact protrusion 152, so that the wafer is in contact with the entire surface area.

[0027] Alternatively, the protrusion 52 may typically be dome-shaped, with the semiconductor wafer resting on a relatively small dot-shaped area.

[0028] Compared to conventional wafer boats, the wafer boat disclosed herein has several advantages. The contact protrusions reduce the contact area between the wafer boat and the wafer, thus reducing slippage. The equally circumferentially spaced contact protrusions promote a uniform distribution of wafer weight across each of the contact protrusions. As those skilled in the art know, peak stresses in the wafer are sensitive to processing inaccuracies of the contact protrusions, which can lead to uneven loading. In embodiments where the contact protrusions are circular, the size and shape of the circular contact protrusions minimize the impact of potential processing inaccuracies, thereby limiting uneven loading of the wafer weight.

[0029] Example

[0030] The process of this disclosure is further illustrated by the following examples. These examples should not be considered limiting.

[0031] Example 1: Probability graph of sliding length

[0032] One silicon wafer assembly is annealed using a wafer boat (containing circular contact protrusions with a length of 10 mm), and another assembly is annealed in a wafer boat (containing circular contact protrusions with a length of 20 mm). At a 95% confidence interval, for 10 mm and 20 mm (… Figure 5 The wafer boat determines the probabilistic sliding length for each of the cylindrical contact protrusions in the contact protrusion length. For example... Figure 5 As shown, a 20mm long contact protrusion results in a reduced sliding length compared to a 10mm contact protrusion.

[0033] As used herein, the terms “about,” “generally,” “substantially,” and “approximately” when used with a range of size, concentration, temperature, or other physical or chemical properties or characteristics mean to cover variations that may exist in the upper and / or lower limits of the range of properties or characteristics, including variations, for example, that result from rounding, measurement, or other statistical variations.

[0034] When describing elements of this disclosure or embodiments thereof, the articles “a,” “an,” and “the” are intended to mean that one or more elements are present. The terms “comprising,” “including,” “containing,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to the listed elements. Terms indicating a particular orientation (e.g., “top,” “bottom,” “side,” etc.) are used for ease of description and do not require any particular orientation of the described items.

[0035] Since various changes can be made to the above-described construction and methods without departing from the scope of this disclosure, all content contained in the foregoing description and shown in the accompanying drawings is intended to be illustrative rather than restrictive.

Claims

1. A wafer boat for supporting multiple semiconductor wafers in a furnace, comprising: First vertical bar; A first set of fingers extends radially inward from the first vertical rod along a first finger axis, the first finger axis extending above a first chord of a circle centered on the longitudinal central axis of the wafer boat, the first chord not intersecting the longitudinal central axis of the wafer boat, each finger of the first set of fingers comprising: An elongated section extending from the first vertical bar; and A contact protrusion, the distal end of which is disposed on the elongated segment toward the finger to contact and support the semiconductor wafer, at least a portion of the contact protrusion protruding relative to the elongated segment; Second vertical bar; A second set of fingers extends radially inward from the second vertical rod along a second finger axis, the second finger axis extending above a second chord of the circle, the second chord not intersecting the longitudinal central axis of the wafer boat, each finger of the second set of fingers comprising: An elongated section extending from the second vertical bar; and A contact protrusion, the distal end of which is disposed on the elongated segment toward the finger to contact and support the semiconductor wafer, at least a portion of the contact protrusion protruding relative to the elongated segment; The third vertical bar; A third set of fingers extends radially inward from the third vertical rod along a third finger axis, the third finger axis extending above a third chord of the circle, the third chord intersecting the longitudinal central axis of the wafer boat, each finger of the third finger set comprising: An elongated section extending from the third vertical bar; and A contact protrusion, the distal end of which faces the finger, is positioned on the elongated segment to contact and support the semiconductor wafer, at least a portion of which protrudes relative to the elongated segment. The contact protrusions of the first, second, and third sets of fingers are spaced 120° apart around the wafer boat. Each contact protrusion is circular, and its height increases from the side of the contact protrusion to the apex extending along the axis of the finger. Each contact protrusion has a longitudinal contact protrusion axis, a length extending along the longitudinal contact protrusion axis, and a width perpendicular to the length. The width of each contact protrusion is 3 mm to 20 mm, the length of each contact protrusion is 10 mm to 50 mm, and the distance from the contact protrusion to the longitudinal central axis of the wafer boat is 75 mm to 125 mm, for placing the semiconductor wafer along the longitudinal contact protrusion axis on the circular contact protrusions.

2. The wafer boat according to claim 1, wherein the contact protrusion has a width of 8 mm, a length of 30 mm, and the distance from the contact protrusion to the longitudinal central axis of the wafer boat is 100 mm.

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