DE202017107959U1 - Wafer carrier with a 33-pocket configuration - Google Patents

Abstract

A wafer carrier adapted to be used with a chemical vapor deposition apparatus, the wafer carrier comprising: a body having a top surface and a bottom surface opposed to each other; a plurality of pockets defined in the top surface of the wafer carrier; the improvement comprising the plurality of pockets consisting of a total of thirty-three pockets, each of the pockets being disposed along one of an inner circle, a middle circle, or an outer circle, the central circle being asymmetric with respect to the middle circle and the outer circle is arranged.

Description

Technical area

The invention relates generally to semiconductor fabrication technology, and more particularly to chemical vapor deposition (CVD) processing and associated apparatus for holding semiconductor wafers during processing.

background

In the fabrication of light emitting diodes (LEDs) and other high performance devices such as laser diodes, optical detectors, and field effect transistors, typically a chemical vapor deposition (CVD) process is used to grow a thin film stack structure using materials such as gallium nitride over a sapphire or silicon substrate. A CVD tool includes a processing chamber that is a sealed environment that allows infused gases to react on the substrate (typically in the form of wafers) to grow through the thin film layers. Examples of current product lines such manufacturing equipments are the Turbo Disc ^® - and EPIK ^® -families of systems for metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition, MOCVD) that are manufactured by Veeco Instruments Inc. of Plainview, New York.

A number of process parameters are controlled, e.g. Temperature, pressure and gas flow rate to achieve desired crystal growth. Different layers are formed by growth using different materials and process parameters. For example, devices formed from compound semiconductors such as III-V semiconductors are typically formed by growing successive layers of the compound semiconductor using MOCVD. In this process, the wafers are exposed to a combination of gases, typically including an organometallic compound as a Group III metal source and including a group V element source, which flow over the surface of the wafer while the wafer is held at an elevated temperature becomes. In general, the organometallic compound and the source of group V are combined with a carrier gas which does not appreciably participate in the reaction, e.g. Nitrogen. An example of a III-V semiconductor is gallium nitride obtained by a reaction of an organogallium compound and ammonia on a substrate having a suitable crystal lattice spacing, e.g. As a sapphire wafer can be formed. The wafer is normally held at a temperature of the order of 1,000 to 1,100 ° C during deposition of the gallium nitride and related compounds.

In an MOCVD process, where formation is by growth of crystals by a chemical reaction on the surface of the substrate, the process parameters must be particularly carefully controlled to ensure that the chemical reaction proceeds under the required conditions. Even small deviations in the process conditions can affect the component quality and the production yield. For example, when a gallium and indium nitride layer is deposited, variations in the wafer surface temperature cause variations in the composition and band gap of the deposited layer. Since indium has a relatively high vapor pressure, the deposited layer will have a lower content of indium and a larger band gap in the regions of the wafer where the surface temperature is higher. If the deposited layer is an active, light-emitting layer of an LED structure, the emission wavelength of the LEDs formed from the wafer also varies to an impermissible extent.

In an MOCVD process chamber, semiconductor wafers on which thin film layers are to be grown are placed on fast rotating carousels, called wafer carriers, to provide uniform deposition of the semiconductor material's surfaces with respect to the atmosphere in the reactor chamber. The speed is on the order of 1,000 rpm. The wafer carriers are typically machined from a high thermal conductivity material such as graphite and often coated with a protective layer of a material such as silicon carbide. Each wafer carrier has in its top a series of circular pits into which individual wafers are placed. Typically, the wafers are maintained in spaced relation to the underside surface of each of the pockets to facilitate gas flow around the edges of the wafer. Some examples of pertinent technologies are disclosed in US Patent Application Publication No. 2012/0040097, in which U.S. Patent No. 8,092,599 , by doing U.S. Patent No. 8,021,487 in US Patent Application Publication No. 2007/0186853, in which U.S. Patent No. 6,902,623 , by doing U.S. Patent No. 6,506,252 and in that U.S. Patent No. 6,492,625 described, the disclosures of which are incorporated herein by reference.

The wafer carrier is held on a spindle in the reaction chamber, so that the top surface of the wafer carrier with the exposed Surface of the wafer is turned upwards to a gas distribution device. As the spindle rotates, the gas is directed down onto the top surface of the wafer carrier and flows over the top surface toward the periphery of the wafer carrier. The gas used is discharged from the reaction chamber through openings arranged below the wafer carrier. The wafer carrier is maintained at the desired elevated temperature by thermal elements, typically electrical resistive heating elements, disposed below the underside surface of the wafer carrier. These heat elements are maintained at a temperature above the desired temperature of the wafer surfaces, whereas the gas distribution device is typically maintained at a temperature well below the desired reaction temperature to prevent premature reaction of the gases. Therefore, the heat is transferred from the heating elements to the underside surface of the wafer carrier and flows up through the wafer carrier to the individual wafers.

The gas flow across the wafers varies depending on the radial position of each wafer, with the outermost positioned wafers being exposed to higher flow rates due to their faster velocity during rotation. Even on each individual wafer, there may be temperature non-uniformities, i. H. cold spots and hot spots. One of the variables that affects the formation of temperature nonuniformities is the shape of the pockets in the wafer carrier. As a rule, pocket shapes form a circular shape in the surface of the wafer carrier. As the wafer carrier rotates, the wafers are exposed to significant centripetal force at their outermost edge (i.e., the outermost edge of the axis of rotation), thereby causing the wafer to press against the inner wall of the respective pocket in the wafer carrier. Under this condition, there is close contact between these outer edges of the wafer and the pocket edge. The increased heat conduction to these outermost portions of the wafer results in greater temperature nonuniformity, further aggravating the problems described above. Efforts have been made to minimize temperature nonuniformity by increasing the gap between the edge of the wafer and the inner wall of the pocket, including the design of a wafer that is flat on a portion of the edge (i.e., a "flat" wafer). This flat portion of the wafer creates a gap and reduces the contact points with the inner wall of the pocket, thereby mitigating temperature nonuniformities. Other factors that affect the heating uniformity in the wafers held by the wafer carrier include the heat transfer and emissivity properties of the wafer carrier combined with the location of the wafer pockets.

Taking into account the requirements of temperature uniformity, another desirable property of wafer carriers is to increase the throughput of the CVD process. The role of the wafer carrier in increasing process throughput is to hold a larger amount of individual wafers. The provision of a wafer carrier structure assembly with more wafers affects the thermal model. For example, the portions of the wafer carrier near the edges tend to be at a lower temperature than other portions due to heat radiation loss from the wafer carrier edges.

Accordingly, a practical solution for wafer carriers is needed that takes into account temperature uniformity as well as mechanical stresses in high density structural assemblies.

Summary

A wafer carrier includes a new array of pockets. The arrangements described herein facilitate heat transfer as well as high packing density of pockets for growth of circular wafers.

Brief description of the drawings

The invention may be more fully understood in consideration of the following detailed description of several embodiments of the invention taken in conjunction with the accompanying drawings. Show it:

1 a schematic view of a MOCVD process chamber according to an embodiment.

2 a perspective view of a wafer carrier with a 33-pocket configuration according to an embodiment.

3 a top plan view of a wafer carrier with a 33-pocket configuration according to an embodiment.

4 a side view of a wafer carrier with a 33-pocket configuration according to an embodiment.

5 a bottom plan view of a wafer carrier with a 33-pocket configuration according to an embodiment.

6 FIG. 12 is a detailed view of a portion of a wafer carrier having a 33-pocket configuration showing a single pocket from a perspective view, according to one embodiment. FIG.

Detailed description

1 illustrates an apparatus for chemical vapor deposition according to an embodiment of the invention. A reaction chamber 10 defines a process environment space. The gas distribution device 12 is disposed at one end of the chamber. The end with the gas distribution device 12 is here referred to as the "topside" of the reaction chamber 10 designated. This end of the chamber is typically, but not necessarily, located in the normal gravitational frame of reference at the top of the chamber. Thus, the downward direction used herein refers to the direction away from the gas distribution device 12 whereas the upward direction is the direction in the chamber to the gas distribution device 12 regardless of whether these directions are aligned with the gravitational upward and downward directions. Similarly, the "top surface" and the "bottom surface" of elements will be referred to herein with reference to the reference frame of the reaction chamber 10 and the gas distribution device 12 written.

The gas distribution device 12 is with sources 14 . 16 and 18 for supplying process gases to be used in the wafer processing process, e.g. A carrier gas and reactant gases such as an organometallic compound and a source of a Group V metal. The gas distribution apparatus 12 is arranged to receive the different gases and to direct a flow of process gases substantially in the downward direction. The gas distribution device 12 is desirably also with a coolant system 20 arranged to be a liquid through the gas distribution device 12 to circulate to maintain the temperature of the gas distribution device at a desired temperature during operation. A similar coolant arrangement (not shown) may be used to cool the walls of the reaction chamber 10 be provided. The reaction chamber 10 is also with an exhaust system 22 arranged to be exhausted gases from the interior of the chamber 10 through orifices (not shown) at or near the bottom of the chamber to provide a continuous flow of gas in the downward direction from the gas distribution device 12 to enable.

A spindle 24 is arranged in the chamber, so that the central axis 26 the spindle 24 extending in the upward and downward directions. The spindle 24 is through a conventional rotary feedthrough device 28 , which contains bearings and seals (not shown), mounted on the chamber, so that the spindle 24 around the central axis 26 can rotate while a seal between the spindle 24 and the wall of the reaction chamber 10 preserved. The spindle has at the top end thereof, ie, at the end of the spindle, the gas distribution device 12 closest is a connection element 30 on. As further explained below, the connecting element 30 an example of a wafer carrier retention mechanism adapted to releasably engage a wafer carrier. In the particular embodiment shown, the connecting element 30 a substantially frusto-conical member that tapers toward the top end of the spindle and terminates on a flat top surface. A frusto-conical element is an element with the shape of a truncated cone. The spindle 24 is with a rotary drive mechanism 32 connected, z. B. an electric motor drive, which is arranged to the spindle 24 around the central axis 26 to turn.

The connection element 30 can also be any number of other configurations. For example, a spindle could 24 in which one end is shaped as a quadrangle or a rounded quadrangle, a series of posts, an oval or other rounded shape with an aspect ratio other than 1: 1, a triangle, into a mating connecting element 30 be inserted. There may be numerous other wedge, groove or locking arrangements between the spindle 24 and the connection element 30 be used, which receive a rotatable engagement between these components and prevent unwanted slippage. In embodiments wedge, groove or locking arrangements can be used which, despite the expected amounts of thermal expansion or contraction of one of the two components, the desired degree of rotatable engagement between the connection element 30 and the spindle 24 receive.

The heating element 34 is mounted in the chamber and surrounds the spindle 24 under the connection element 30 , The reaction chamber 10 is also with an entrance opening 36 that became an atrium 38 leads, and a door 40 provided for closing and opening the inlet opening. The door 40 is in 1 shown only schematically and is considered movable between the closed position shown with solid lines, in which the door is the interior of the reaction chamber 10 from the antechamber 38 isolated, and one at 40 ' shown with dashed lines open position. The door 40 is with a suitable control and actuating mechanism for moving the same between the equipped open position and closed positions. In practice, the door may comprise a closing element which is movable in the upward and downward direction, such as in the U.S. Patent No. 7,276,124 , the disclosure of which is incorporated herein by reference. In the 1 The illustrated apparatus may further include a loading mechanism (not shown) capable of, in the operating condition, a wafer carrier from the antechamber 38 to move into the chamber and the wafer carrier with the spindle 24 As well as being able to, a wafer carrier from the spindle 24 down and into the antechamber 38 to move.

The device also includes a plurality of wafer carriers. In the in 1 shown operating state is a first wafer carrier 42 in an operating condition in the reaction chamber 10 whereas a second wafer carrier 44 in the antechamber 38 is arranged. Each wafer carrier comprises a body 46 , which is essentially the shape of a circular disc with a central axis (see 2 ) having. The body 46 is formed symmetrically about an axis. In the operating state is the axis of the wafer carrier body with the central axis 26 the spindle 24 congruent. The body 46 can be formed as a single piece or as a composite of several pieces. For example, as disclosed in US Patent Application Publication No. 20090155028, the disclosure of which is incorporated herein by reference, the wafer carrier body may include a hub defining a small area of the body surrounding the central axis and a larger portion containing the remainder defined the disc-shaped body. The body 46 is desirably formed from materials which do not contaminate the process and which can withstand the temperatures encountered in the process. For example, the major portion of the disk may be formed largely or wholly from materials such as graphite, silicon carbide, or other refractory materials. The body 46 essentially has a planar top surface 48 and a bottom surface 52 which extend substantially parallel to each other and substantially perpendicular to the central axis of the disc. The body 46 also includes one or a plurality of wafer retention features adapted to hold a plurality of wafers.

In operation is a wafer 54 , z. A wafer-like wafer formed of sapphire, silicon carbide, or other crystalline substrate, in each pocket 56 each wafer carrier arranged. Typically, the wafer has 54 a thickness which is small compared to the dimensions of the main surfaces thereof. For example, a circular wafer having a diameter of about 2 inches (50 mm) or a circular wafer having a diameter of about 4 inches (100 mm) may have a thickness of about 770 μm or less. As in 1 is illustrated is the wafer 54 arranged with an upwardly facing top surface, so that the top surface is exposed at the top of the wafer carrier.

In a typical MOCVD process, the wafer carrier becomes 42 with loaded wafers from the antechamber 38 in the reaction chamber 10 loaded and in the in 1 placed operating position shown. In this state, the top surfaces of the wafers are up to the gas distribution device 12 turned. A heating element 34 is actuated and a rotary drive mechanism 32 is operated to the spindle 24 and thus the wafer carrier 42 around the axis 26 to turn. Typically, the spindle 24 rotated at a rotational speed of about 50 to 1,500 revolutions per minute. The process gas supply units 14 . 16 and 18 are operated to release gases through the gas distribution device 12 to deliver. The gases run down to the wafer carrier 42 down, over the top surface 48 of the wafer carrier 42 and the wafers 54 and down around the periphery of the wafer carrier to the outlet and the exhaust system 22 , Thus, the top surface of the wafer carrier and the top surfaces of the wafer 54 exposed to a process gas comprising a mixture of the different gases supplied by the different process gas supply units. Most typically, the process gas settles on the top surface predominantly from that through the carrier gas supply unit 16 delivered carrier gas together. In a typical chemical vapor deposition process, the carrier gas may be nitrogen, and thus the process gas at the top surface of the wafer carrier is composed predominantly of nitrogen with a proportion of the reactive gas components.

The heat elements 34 transmit the heat to the underside surface substantially by radiant heat transfer 52 of the wafer carrier 42 , The on the bottom surface 52 of the wafer carrier 42 applied heat flows through the body 46 of the wafer carrier up to the top surface 48 of the wafer carrier. Heat going up through the body also passes through gaps up to the bottom surface of each wafer and through the wafer up to the top surface of the wafer 54 , The heat is from the top surface 48 of the wafer carrier 42 and radiated from the top surfaces of the wafer to the colder elements of the process chamber, e.g. B. to the walls of the process chamber and to the gas distribution device 12 , The heat is also from the top surface 48 of the wafer carrier 42 and the top surfaces of the Transfer wafer to the process gas passing over these surfaces.

In the illustrated embodiment, the system includes a number of features designed to provide uniformity of heating of the surfaces of each wafer 54 to judge. In this embodiment, a temperature profile detection system receives 58 Temperature information representing a temperature and temperature monitoring position information from a temperature monitor 60 may include. In addition, the temperature profile detection system receives 58 Wafer carrier position information, in one embodiment of the rotary drive mechanism 32 can come. This information is used by the temperature profile acquisition system 58 a temperature profile of the pockets 56 on the wafer carrier 42 , The temperature profile provides a heat distribution on the surface of each of the pockets 56 or the wafer contained therein 54 represents.

2 is a perspective view of a wafer carrier 142 according to an embodiment. 3 is a top plan view of the same wafer carrier 142 , The wafer carrier 142 has a body 146 with a top surface 148 as well as thirty-three pockets defined therein 162 on. At the in 2 and 3 embodiment shown are the pockets 162 arranged in three circles. The outermost circle is arranged concentrically to the middle circle. The central circle of five pockets is arranged asymmetrically to the outer and the middle circle. The asymmetric arrangement facilitates tighter packing of all thirty-three pockets 162 , In the radially innermost circle are four pockets 162 azimuthal evenly spaced. Likewise, ten pockets are in the radially middle circle 162 azimuthal evenly spaced. In the radially outermost circle are seventeen pockets 162 azimuthal evenly spaced. Each of the bags 162 is one in the body 146 formed aperture, which extends substantially perpendicular to the plane along which the top surface 148 is arranged.

In the 2 and 3 The arrangement of pockets shown is advantageous in that it provides a desired degree of heat uniformity while providing a relatively high density of pockets 162 on the top surface 148 is maintained. In embodiments, the top surface may be 148 have a diameter of about 675 mm and a diameter of about 695 mm, 705 mm, 716 mm and about 720 mm. The bags 162 are then dimensioned so that they fit into this area. For example, the bags 162 in embodiments have a diameter of about 50 mm or a diameter of about 100 mm.

3 also represents the representative circles around which the pockets 162 are arranged. At the in 3 In the embodiments shown, there are three circles: R1, R2 and R3, each having a different radius, concentric with each other and with the circular profile of the top surface 148 are arranged.

4 is a side view of the wafer carrier 142 out 2 and 3 which is shown in a side view. In the in 4 As shown, the relative size difference between the top surface 148 and the bottom surface 152 be seen. In particular, the top surface extends farther to the top and bottom of the page, as in FIG 4 is shown, or further radially in the in 2 and 3 shown views. Each of the previously in 2 and 3 pictured bags 162 extends from the top surface 148 to the bottom surface 152 out. The underside surface 152 provides a solid base on the wafer in the wafer carrier 142 can be formed through growth.

5 is a bottom plan view on the previously with respect to 2 - 4 described wafer carrier 142 , As in 5 is shown, the wafer carrier comprises 142 a locking feature 164 in the middle of the bottom surface 152 , The locking feature 164 is adapted to engage another component, e.g. B. the connection element 30 the previously in 1 shown spindle 24 , In different embodiments, the locking feature 164 For example, have a groove, a clamping or a wedge connection element. One skilled in the art will recognize that a variety of mechanisms are capable of this, the wafer carrier 142 to impart an angular momentum from the neighboring component.

The bottom surface 152 can be made of any material and is designed in embodiments to facilitate heat transfer. As previously described, in embodiments, it is desirable to collect heat from a nearby thermal element (eg, those in FIG 1 shown heat elements 34 ) to the bottom surface 152 transferred to. So can the bottom surface 152 consist of a relatively low-reflection material or may be coated with such a substance.

The wafer carrier 142 In embodiments, it may be made of any material suitable for epitaxial growth growth, e.g. As graphite or a graphite-coated material. For others Embodiments may be the material from which the wafer carrier 142 be selected to match a desired crystal lattice arrangement or size. Also, depending on the wafers to be formed by growth, different sizes of the pockets 162 be used.

6 is a partial perspective view of one of the bags 162 shows. The bags 162 each include a side wall 166 which has a substantially cylindrical shape. The bottom of the cylinder, passing through the side wall 166 is formed, is a substrate 168 , In embodiments, the side wall 166 have a depth of about 430 microns.

The embodiments are intended to be illustrative and not restrictive. Further embodiments are included in the claims. In addition, one skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention as defined by the claims, although aspects of the present invention have been described with reference to particular embodiments.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US8092599 [0005]
• US 8021487 [0005]
• US 6902623 [0005]
• US 6506252 [0005]
• US 6492625 [0005]
• US 7276124 [0022]

Claims (15)

A wafer carrier adapted to be used with a chemical vapor deposition apparatus, the wafer carrier having: a body in which a top surface and a bottom surface are opposed to each other; a plurality of pockets defined in the top surface of the wafer carrier; the improvement comprising the plurality of pockets consisting of a total of thirty-three pockets, each of the pockets being disposed along one of an inner circle, a middle circle, or an outer circle, the central circle being asymmetric with respect to the middle circle and the outer circle is arranged. The wafer carrier of claim 1, wherein: five of the plurality of pockets are arranged around a first of the three circles; eleven of the plurality of pockets are arranged around a second of the three circles; and seventeen of the plurality of pockets are arranged around a third of the three circles. The wafer carrier according to one of the preceding claims, wherein the first circle is surrounded by the second circle and wherein the second circle is surrounded by the third circle. The wafer carrier of claim 1, wherein the top surface has a diameter of about 675 mm. The wafer carrier of claim 1, wherein the top surface has a diameter of about 695 mm. The wafer carrier of claim 1, wherein the top surface has a diameter of about 705 mm. The wafer carrier of claim 1, wherein the top surface has a diameter of about 716 mm. The wafer carrier of claim 1, wherein the top surface has a diameter of about 720 mm. The wafer carrier according to claims 1 to 8, wherein the plurality of pockets each have a pocket diameter of about 100 mm. The wafer carrier according to claims 1 to 8, wherein the plurality of pockets each have a radial wall with a depth of about 760 μm. The wafer carrier of claim 1, further comprising a locking feature disposed on the underside surface. The wafer carrier of claim 11, wherein the interlocking feature is located in the geometric center of the underside surface. The wafer carrier according to claim 12, wherein the interlocking feature is selected from the group consisting of a groove, tension or wedge connection element. The wafer carrier according to claim 1, wherein the top surface and the bottom surface each have a diameter and the diameter of the top surface is larger than the diameter of the bottom surface. The wafer carrier of claim 1, wherein the wafer carrier is adapted for use in a metal oxide vapor deposition chemical system.

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