DE202013104896U1 - heating arrangement - Google Patents

Abstract

Apparatus for growing epitaxial layers on a wafer having a chamber, a wafer carrier mounted in the chamber for mounting at least one wafer thereon and a heating element mounted in the chamber for heating the wafer to a predetermined temperature for growing the epitaxial layer thereon the heating element comprises a plurality of heating wires, wherein the heating wires lie in the same plane and are arranged spatially parallel to and circumferentially aligned with the wafer carrier.

Description

TECHNICAL AREA

The present invention relates to wafer processing devices and heating assemblies for use in such processing devices. Specifically, the present disclosure relates to heating elements and the mechanical support of heating filaments of the heating element in a wafer processing apparatus, wherein the heating element is mounted in the processing apparatus for heating wafers mounted on a wafer carrier.

GENERAL PRIOR ART

Many semiconductor devices are fabricated by epitaxy of a semiconductor material on a substrate by a method known as chemical vapor deposition (CVD). The substrate is usually a crystalline material in the form of a disk, commonly referred to as a "wafer". In this process, the wafers are contacted with one or more chemical precursors while maintaining the wafer at an elevated temperature. The precursor gases react and / or decompose at the surface of the substrate to produce the desired deposit. Common precursors used in the CVD process include metals, metal hydrides, halides and halohydrides, and organometallic compounds. Usually, the precursor is mixed with a carrier gas, e.g. Nitrogen, which is not appreciably involved in the reaction. The carrier gas and unwanted by-products are removed from the gas stream through the reaction chamber.

For example, devices fabricated from compound semiconductors such as III-V semiconductors are commonly prepared by growing successive layers of the compound semiconductor using metalorganic chemical vapor deposition or "MOCVD." Examples of III-V semiconductors include light emitting diodes (LEDs) and other high power devices such as laser diodes, optical detectors, and field effect transistors. Such components can be prepared by the reaction of an organo-gallium compound and ammonia on a substrate having a suitable crystal lattice spacing, such as. As a sapphire or silicon wafer. Usually, the wafer is maintained at a temperature of the order of 500-1200 ° C during the deposition of gallium nitride and related compounds. During the process, it is common for the heating element to be heated up to 1000-2200 ° C for the wafer to reach its process temperature. A number of other process parameters, such. Pressure and gas flow, are also controlled to achieve the desired crystal growth. After all of the semiconductor layers have been fabricated, and usually after attaching proper electrical contacts, the wafer is split into discrete components.

In general, a MOCVD reactor consists of a reaction chamber equipped for transporting and placing the substrate in the chamber, a substrate holder, and a temperature controlled heating system.

To support the uniformity of epitaxy, the semiconductor wafers on which layers of thin layers are to be grown are laid on rapidly rotating carusels called wafer carriers. The rotation frequency is on the order of 500 to 1500 rpm. This rapid rotation provides for more uniform contact of the wafer surfaces with the atmosphere within the process chamber for deposition of the semiconductor materials. The wafer carriers are typically made of 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 set of circular recesses or pockets into which individual wafers are placed.

The wafer carrier is mounted in the process chamber on a spindle so that the top of the wafer carrier, which has the exposed surfaces of the wafer, is swept up to a gas distribution device. As the spindle rotates, gas is directed down onto the top of the wafer carrier and flows over the top toward the edge of the wafer carrier. The used gas exits the reaction chamber through openings located below the wafer carrier.

The wafer carrier is maintained at the desired elevated temperature by heating elements, typically located below the bottom of the wafer carrier, electrical resistance heating elements. These heating elements are maintained at a temperature above the desired temperature of the wafer surfaces, with the gas distribution device usually maintained at a temperature well below the desired reaction temperature to avoid premature reaction of the precursor. Therefore, heat is transferred from the heating elements to the bottom of the wafer carrier and flows up through the wafer carrier to the individual wafers. Heat transmitted upward through the substrate is also radiated from the top of the wafer carrier. The degree of radiant heat transfer from the wafer carrier is a function of the emissivity of the various surfaces of the carrier and the surrounding components (eg, the protective layer, the wafers, and the deposited thin layers).

Heaters are generally made of tungsten, molybdenum, niobium, tantalum, rhenium and alloys thereof to withstand such high temperatures (1000-2200 ° C). A problem of known heating elements is the thermally induced deformation of the heating element. This problem is exacerbated by the enlargement of the heating element for installation in ever larger MOCVD. In addition, to ensure that the heating elements are properly positioned, various types of mechanical support structures are known. In general, clamps are used which support the heating element to hold it in a predefined position even during the expansion of the heating element. During the heating process, the heating element tries to expand its dimensions, and therefore a thermally induced stress is generated inside the material of the heating element.

An MOCVD system having a larger diameter heater assembly with heating elements that can expand due to temperature increases while reducing the stress on the heating element and maintaining uniform heating would be welcomed.

SUMMARY

One aspect of the present disclosure provides a heating element for planar heating of a MOCVD reactor that is lightweight and relatively inexpensive to manufacture and limits the induced stress introduced in larger heating elements while maintaining uniform heating.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by considering the following detailed description of various embodiments of the invention in conjunction with the accompanying drawings, in which:

1 3 is a perspective view of a wafer carrier and a motor assembly according to an embodiment of the invention,

2 a perspective view of a in the device of 1 used wafer carrier according to an embodiment of the invention,

3 is a plan view of a heat shield mounted on a heater assembly according to an embodiment of the invention,

4a is a plan view of an inner heating wire of a heating arrangement according to an embodiment of the invention,

4b 3 is a side view of an inner heating wire of a heating arrangement according to an embodiment of the invention,

5a is a plan view of a central heating wire of a heating arrangement according to an embodiment of the invention,

5b 3 is a side view of a middle heating wire of a heating arrangement according to an embodiment of the invention,

6a is a plan view of an outer heating wire of a heating arrangement according to an embodiment of the invention,

6b 3 is a side view of an outer heating wire of a heating arrangement according to an embodiment of the invention,

7 3 is a perspective view of a heating arrangement according to an embodiment of the invention,

8th an exploded view of 7 similar representation according to an embodiment of the invention,

9a - 9e represent different views of a shaft heater and / or a Schaftheizdrahts according to embodiments of the invention,

10a - 10d Illustrate clamps and clamp locations according to embodiments of the invention,

11a - 11d Illustrate hooks and cradles according to embodiments of the invention.

12 Figure 3 is a perspective view of the bottom of the heating assembly showing in detail the electrode gaskets and connector plates mounted on the heater base according to an embodiment of the invention.

While the invention is susceptible of various modifications and alternative forms, details of which are shown by way of example in the drawings and described in detail. It is to be understood, however, that it is not intended to limit the invention to the particular embodiments described. On the contrary, it is intended that all modifications, equivalents and alternatives fall within the spirit and scope of the invention as defined by the claims.

DETAILED DESCRIPTION

In 1 is a wafer carrier assembly 10 and a motor assembly 12 depicted as part of a chemical vapor deposition apparatus. 2 shows the wafer carrier assembly 10 including heating element 14 in detail. The wafer carrier 16 is on a spindle 18 assembled. The wafer carrier 16 has a structure having a body generally in the form of a circular disk having a central axis extending perpendicular to the top and bottom. The body of the wafer carrier 16 has a first major surface referred to herein as the top 20 and a second major surface referred to herein as the underside 22 referred to as. The top 20 of the wafer carrier 16 is facing a gas distribution element, while the bottom 22 down the heating element 14 to and from the gas distribution element is turned away. The outer circumference of the heating element 14 is essentially on the outer circumference of the wafer carrier 16 aligned. The body of the wafer carrier 16 For example, it may have a diameter of about 695 mm with a thickness of about 15.9 mm between the top 20 and the bottom 22 to have. The heating element 14 is dimensioned to the circumferential dimensions of the wafer carrier 16 essentially to match.

The heating element 14 is substantially parallel to and at a distance from the bottom 22 of the wafer carrier 16 arranged. The mounting of the heating element 14 in relation to the wafer carrier 16 allows unrestricted thermal expansion of the radiant heating elements. The heating element 14 is substantially plate-like or has substantially flat dimensions, ie "planar", which means substantially planar, so that the heating element 14 does not extend more than 10% from a plane without displacement. The heating element 14 is further arranged so that the heating element 14 on or from a variety of shield carriers or terminals 24 is mounted and supported. The clamps 24 are at their lower end 26 with screws or any type of mechanical fastening device or via a pin-hole type arrangement on a heat shield 28 attached.

3 illustrates the heating element 14 as disclosed herein. The heating element 14 ensures circulated and convention heat for the reactor chamber. In one embodiment, the heating element 14 a diameter of about 675 mm ± 5%. The assembled heating element 14 may be generally planar and circular. The heating element 14 includes a variety of heating wires in the plane. A circular planar heating element 14 is advantageous for the intended uses, ie in a MOCVD, because the wafer carrier 16 is a rotating circular plate and the heating cover is optimized when the heating element 14 has a shape that matches that of the wafer carrier 16 matches. The heating element 14 can be divided along an axis x, so that the heating element 14 from a first half 36 and a second half 38 is composed. Every half 36 . 38 consists of a middle heating wire 32 and an outer heating wire 34 , The first half 36 and the second half 38 share an inner heating wire 30 , wherein the inner heating wire 30 symmetrical between the two halves 36 . 38 is arranged. Each of the heating wires 30 . 32 . 34 has curved structures, so every heating wire 30 . 32 . 34 a part of the circular geometry of the heating element 14 includes.

The heating wires 30 . 32 . 34 are each planar and have a length that is longer than their width. The heating wires 30 . 32 . 34 are curved and are essentially in one plane. The structure of each heating wire 30 . 32 . 34 is designed so that the heating wires 30 . 32 . 34 the structure of their adjacent heating wire 30 . 32 . 34 follow, but with their neighboring heating wire 30 . 32 . 34 do not come in contact. The heating wires 30 . 32 . 34 are essentially nested at the level to one of the different heating wires 30 . 32 . 34 To provide formed complex structure. The shape of the heating wires 30 . 32 . 34 requires that side or edge of each heating wire 30 . 32 . 34 not with the side or edge of another heating wire 30 . 32 . 34 comes into contact and that the space between the heating wires 30 . 32 . 34 each is substantially uniform, except at points where the curvature of each heating wire 30 . 32 . 34 less than 90 degrees.

The inner heating wire 30 , the middle heating wire 32 and the outer heating wire 34 are each with at least two connector ends 40 . 42 . 44 . 46 . 48 . 50 provided for the mechanical support and power supply of the heating element 14 are configured and located respectively at one of the two ends of the heating wire 30 . 32 . 34 are located. The connector ends 40 . 42 . 44 . 46 . 48 . 50 are so with the extensions ( 12a ) of the connector plate 74 connected to that of the inner heating wire 30 , the middle heating wire 32 and the outer heating wire 34 indirectly coupled with the electrode wiring to the power supply. Apart from the restrictive connection to the connector ends 40 . 42 . 44 . 46 . 48 . 50 with the extensions of the connector plates 74 are the heating wires 30 . 32 . 34 free from any rigid attachment to an immovable surface that could prevent its thermal expansion.

The heating wires 30 . 32 . 34 must be made of materials capable of withstanding high operating temperatures, with temperatures usually between 1000 ° C and 2000 ° C. In One embodiment may be the outer heating wire 34 made of rhenium or an alloy thereof, while the middle heating wire 32 and the inner heating wire 30 may consist of tungsten or an alloy thereof. In another embodiment, the outer heating wire 34 , the middle heating wire 32 and the inner heating wire 30 made of tungsten or an alloy thereof. In a further embodiment, the outer heating wire 34 , the middle heating wire 32 and the inner heating wire 30 of superalloy materials, refractories, graphite, molybdenum, niobium, tantalum, tungsten, rhenium or combinations or alloys thereof. The superalloy materials may be selected from the group consisting of nickel and iron based superalloy compositions.

In embodiments, the heating wires 30 . 32 . 34 at least partially covered with a porous sintered coating. In other embodiments, the heating wires 30 . 32 . 34 be covered on its top and bottom at least partially with a porous sintered coating. In other embodiments, the heating wires 30 . 32 . 34 at its top and bottom except the connector ends 40 . 42 . 44 . 46 . 48 . 50 , covered with a porous sintered coating. In a further embodiment, the heating wires 30 . 32 . 34 completely covered with a porous sintered coating. It is understood that the production of heating wires 30 . 32 . 34 with substantially flat dimensions in ways known to those skilled in the art. For example, the heating wires 30 . 32 . 34 be cut in one embodiment of a plate or a plate-like element.

The inner heating wire 30 as in the 4a and 4b shown in detail, consists of a single piece of material which is curved along a tortuous path within a single flat plane and the outer periphery has a substantially circular configuration. The inner heating wire 30 is configured to be symmetric about axis x. The inner heating wire 30 has a first connector end 40 and a second connector end 42 which are provided for connection to electrodes. The connector ends 40 . 42 are separated by a distance A, and in one embodiment the distance A may be 0.6 inches, but is not limited thereto. Due to the shape and configuration of the inner heating wire 30 the thermal expansion is not limited and the separation of the edges of the heating wire 30 is maintained.

The middle heating wire 32 as in the 5a and 5b shown in detail, consists of a single piece of material that is curved into a substantially semi-circular spiral-like configuration in a single flat plane. For each heating element 14 are two middle heating wires 32 provided so that when assembled, each one of the central heating wires 32 on one of the two sides of the axis x, thereby forming a substantially circular configuration having two separate spiral-like regions. The middle heating wire 32 has a first connector end 44 and a second connector end 46 which are provided for connection to electrodes. The connector ends 44 . 46 are separated by a distance B, wherein the distance B in one embodiment may be 0.5 inches to 0.6 inches, but is not limited thereto. Due to the shape and configuration of the middle heating wire 32 the thermal expansion is not limited and the separation of the edges of the middle heating wire 32 is maintained. The diameter of the semicircle along axis x is formed so that the heating wire material has a semicircular receptacle centered on the axis y 47 forms, with the diameter of the recording 47 about one third of the total diameter of the middle heating wire 32 along axis x. The recording 47 is dimensioned so that the inner heating wire 30 in the recording 47 sits, leaving the outer edge 31 of the inner heating wire 30 next to the outer edge 48 the recording 47 of the middle heating wire 32 but not in contact with him. Due to the shape and configuration of the middle heating wire 32 the thermal expansion is not limited and the separation of the edges of the middle heating wire 32 is maintained.

The outer heating wire 34 , as in 6a and 6b shown in detail, consists of a single piece of material that is curved into a substantially semicircular configuration in a single flat plane. For each heating element 14 are two outer heating wires 34 provided so that when assembled, each one of the outer heating wires 34 on either side of the axis x, thereby forming a substantially circular configuration. The outer heating wire 34 has a first connector end 48 and a second connector end 50 which are provided for connection to electrodes. The connector ends 48 . 50 are separated by a distance C, wherein the distance C in one embodiment may be 24 inches to 26 inches, but is not limited thereto. Due to the shape and configuration of the outer heating wire 34 the thermal expansion is not limited. The diameter of the semicircle along axis x is formed so that the heating wire material has a semicircular receptacle centered on the axis y 52 forms, with the diameter of the recording 52 slightly smaller than the overall diameter of the outer heater wire 34 along the axis x. The recording 52 is dimensioned so that the middle heating wire 32 in the admission 52 sits, leaving the outer edge 45 of the middle heating wire 32 next to the outer edge 54 the recording 52 of the outer heating wire 34 but not in contact with him. Due to the shape and configuration of the outer heating wire 34 the thermal expansion is not limited and the separation of the edges of the outer heating wire 34 from the edge 45 of the middle heating wire 32 is maintained.

The configuration and fixing of the heating wires 30 . 32 . 34 the heater next to the wafer carrier 16 , as described herein, allows for the unrestricted thermal expansion of the heating element 14 to and potential bending or warping of heating wires 30 . 32 . 34 due to a larger thermal expansion can be avoided. The high thermal stress of these heating wires 30 . 32 . 34 therefore does not give rise to thermal expansion problems that would have been expected under these conditions.

In 7 becomes a heating element 14 shown that over terminals 24 on at least one heat shield 28 is mounted. The heat shields 28 are on a heating base plate 29 arranged. The heat shields 28 are under the heating element 14 mounted to stop the heat generated therein, so that the heat in an upward direction toward the wafer carrier 16 is provided to the wafers on the wafer carrier 16 to heat. In one embodiment, the heating element 14 include a four-zone heating system. In other embodiments, the heating element 14 contain less or more than a four-zone heating system. Due to the configuration and the zoned heating, the wafers can be maintained at a uniform temperature to keep the temperature of the wafers uniform, which usually needs to be controlled to about ± 1 ° C. The clamps 24 provide mechanical support for the heating element 14 ready and are between the heating element 14 and the top heat shield 28 arranged. The clamps 24 can have different configurations, e.g. B. as in the 10a - 10d and may be mounted or mounted in a variety of ways. The assembly can be done via fasteners or they can be in openings in the heat shield 28 to be assembled. It will be apparent to those skilled in the art that the terminals shown 24 are not all-inclusive and that other types of clamps 24 can be provided, for. B. leaf spring, spring, pin, etc. In one embodiment, the terminals 24 made of ceramic. In a further embodiment, the clamps may be made of non-conductive materials.

the clamp 24 allows the displacement of the heating element 14 during the thermal expansion of the heating element 14 , When the heating element 14 is heated, which may be in the size range of 1000 ° C-2200 ° C, wants a thermally induced deformation of the heating element 14 occur. the clamp 24 limits the movement of the heating wire 30 . 32 . 34 only in the vertical direction, so that the thermally induced deformation leads to a movement of the heating element 14 in a radial direction of the curved heating element 14 leads.

In embodiments, hooks can 70 , in the 11a - 11d shown, be provided. The hooks 70 are provided to the heating wires 30 . 32 . 34 to stabilize the heater while giving it to the heating wires 30 . 32 . 34 the heater still allow itself during a thermally induced deformation of the heating wire 30 . 32 . 34 to move the heater.

In 8th is an exploded view of a heating arrangement 10 displayed. Furthermore, in one embodiment, a heater shaft 60 and a shaft heating wire 62 as in the 9a - 9e shown in detail, which provided the passage of the spindle 18 allow. In one embodiment, the shaft heating wire 62 consist of rhenium. In a further embodiment, the shaft heating wire may consist of tungsten. The shaft heating wire 62 is via connector plates 64 with the heater shaft 60 firmly connected. The heating shaft 60 is over legs 68 , the openings for receiving the fasteners 69 have, with the shaft heating heat shield 66 connected.

For the skilled person it is obvious that four separate power supplies each to the inner heating wire 30 , the two middle heating wires 32 , the two outer heating wires 34 and the shaft heating wire 62 can be created. In this embodiment, such a four-zone heating system is provided. In other embodiments, individual power supplies may be applied to all heater wires 30 . 32 . 34 . 62 be created to provide a one-zone heating system. In other embodiments, different combinations of the heating wires 30 . 32 . 34 . 62 be connected to separate power supplies to provide two, three, five or six zone heating systems. Each zone is controlled independently of the others, which compensates for heat flow from the wafer carrier 14 to the colder reactor walls, so that the necessary uniform wafer temperature is maintained.

12a - 12d are isometric views of the bottom of the heater assembly 10 holding a variety of at the base plate 29 the heater mounted electrode seals 72 show in detail. The electrode seals 72 provide access for the electrode wiring (not shown) for connection to connection plates 74 ready, with the connection plates with the connector ends 40 . 42 . 44 . 46 . 48 . 50 are connected. While a specific configuration is depicted, it will be apparent to those skilled in the art that various configurations may be provided to achieve the desired functionality.

Another object is to provide a MOCVD reactor having a chamber, a wafer carrier 16 on which one or more wafers are mounted, and the heater assembly 10 including the heating element 14 as described herein.

It is intended that the embodiments be illustrative and not restrictive. In the claims fall even more embodiments. While aspects of the present invention have been described with reference to specific embodiments, those 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.

One of ordinary skill in the art will recognize that the invention may have fewer features than illustrated in a particular embodiment described above. It is not intended that the embodiments described herein be a comprehensive presentation of the manner in which the various features of the invention may be combined. Accordingly, the embodiments are not usually exclusive feature combinations, but rather, the invention may include a combination of various individual features selected from various individual embodiments, as those of ordinary skill in the art will understand.

Claims (15)

Apparatus for growing epitaxial layers on a wafer having a chamber, a wafer carrier mounted in the chamber for mounting at least one wafer thereon and a heating element mounted in the chamber for heating the wafer to a predetermined temperature for growing the epitaxial layer thereon the heating element comprises a plurality of heating wires, wherein the heating wires lie in the same plane and are arranged spatially parallel to and circumferentially aligned with the wafer carrier. The device of claim 1, wherein the heating element is circular. Device according to one of the preceding claims, wherein the heating element has a longitudinal axis. The device of claim 1, wherein the plurality of heating wires comprises an inner heating wire, a first middle heating wire, a second middle heating wire, a first outer heating wire, and a second outer heating wire, wherein the plurality of heating wires cooperate to contact each other without contact the plurality of heating wires lie in the same plane. The device of claim 4, wherein the inner heating wire is symmetrical about the longitudinal axis, the first central heating wire is disposed on one side of the longitudinal axis and the second central heating wire is disposed on the other side of the longitudinal axis and aligned with the first central heating wire and the first outer Heating wire is disposed on one side of the longitudinal axis and the second outer heating wire disposed on the other side of the longitudinal axis and aligned with the first outer heating wire. The device of any one of the preceding claims, wherein the plurality of heating wires have a curved structure such that each of the plurality of heating wires comprises a portion of the circular heating element. Apparatus according to any one of the preceding claims, wherein the heating element is circularly sized to be substantially as large as the peripheral dimension of the wafer carrier or smaller. Apparatus according to any one of the preceding claims, wherein the heating element is circumferentially dimensioned to a diameter of 675 mm ± 5%. The device of any one of the preceding claims, wherein each of the plurality of heating wires has two connector ends, the connector ends being for rigid connection to electrodes for powering the plurality of heating wires. Device according to one of the preceding claims, wherein the heating element can withstand heating to temperatures of at least 2000 ° C. A device according to any one of the preceding claims, wherein each of said plurality of heating wires is made of tungsten or an alloy thereof. A device according to any one of claims 4 to 10, wherein the outer heating wire is made of rhenium or an alloy thereof and each of the inner heating wires and middle heating wires made of tungsten or an alloy thereof. Apparatus according to any one of the preceding claims, wherein each of said plurality of heating wires is wholly or partially covered by a porous sintered coating. Apparatus according to any one of the preceding claims, wherein the heating element is mechanically supported by clamps, the clamps being mounted to a heat shield so that the clamps are disposed between the heating element and the heat shield, the clamps permitting radial thermal displacement of the heating element. Device according to one of the preceding claims, wherein the heating element is configured to provide two to six heating zones and preferably four heating zones.

Images