DE102022126327A1 - ELECTRON BEAM SUBSTRATE HEATING FOR COATING, EVAPORATION OR MOLECULAR BEAM EPITAXY - Google Patents

Abstract

A device comprises a substrate receiving device (5) for receiving a substrate (4) to be coated, an electron beam source (1) arranged on a first side of the substrate receiving device (5) for emitting an electron beam bundle in the direction of the substrate receiving device (5), one or more evaporation sources (8) which are arranged on a second side of the substrate receiving device (5) opposite the first side.

Description

TECHNICAL AREA

The present disclosure relates to a heating device for heating a substrate to be coated, a device and a method for coating, vapor deposition or molecular beam epitaxy, and a use of an electron beam source in a device for coating, vapor deposition or molecular beam epitaxy.

BACKGROUND

The heating elements for heating substrates (e.g. wafers) in vapor deposition systems, coating systems or molecular beam epitaxy (MBE) systems are often made with conventional heaters made of tungsten, niobium, molybdenum, tantalum or other metal wires, or of SiC or graphite. At very high temperatures, these metal wire heaters often react with corrosive gases such as oxygen or nitrogen in the corresponding process environment. In the oxygen environment in the coating chamber in particular, the achievable substrate temperature is limited to 900°C. At higher temperatures, reactions or instability of the heater materials occur.

Another method uses light or thermal radiation from external sources such as lasers to heat the substrate. The radiation is guided into the vacuum chamber through windows or glass fibers, for example, and directed onto the substrate using suitable optics. The optics mentioned are usually stationary, i.e. the beam distribution can only be changed with considerable effort. Another disadvantage is that substrates such as sapphire, strontium titanate and related substrate materials have to be metallized on the back to increase optical absorption so that they can be heated by radiant heating. However, typical metal layers often also have high reflectivity, so that the heat input to the substrate is often inefficient.

For these and other reasons, there is a need for the present disclosure.

SUMMARY

A first aspect of the present disclosure relates to a heating device for heating a substrate to be coated, comprising a substrate receiving device for receiving a substrate to be coated on a first front surface, and an electron beam source for emitting an electron beam towards a second rear surface of the substrate.

According to an embodiment of the heating device according to the first aspect, the substrate receiving device is designed as a substrate receiving plate. This can, for example, have an opening in a central region in which a substrate can be attached in a suitable manner.

According to an embodiment of the heating device according to the first aspect, the substrate receiving device is rotatable about a central axis. The central axis can be, for example, a cylindrical axis of symmetry that runs through the electron beam source and through a center of the substrate or the opening. The rotatability of the substrate receiving device can contribute to the energy transfer to the substrate as a result of absorption by the electron beam being spatially homogeneous and thus the heat in the substrate being generated in a spatially homogeneous manner. The rotatability also serves above all to homogenize the front-side coating process.

According to an embodiment of the heating device according to the first aspect, the electron beam source is configured such that the electron beam has a variable opening angle and/or can be deflected in a lateral direction. This can also serve, if necessary in combination with the rotatable substrate support plate, to achieve a homogeneous temperature distribution on the substrate. However, as an alternative, this feature can also be used to generate defined, local temperature distributions or inhomogeneities on the substrate.

According to an embodiment of the heating device according to the first aspect, it further comprises an additional heating of the substrate. This additional heating can be provided, for example, by a heating wire or a radiant heater and can in particular ensure that a temperature drop in the edge region of the substrate as a result of too little energy input from the electron beam is compensated or at least reduced.

According to one embodiment of the heating device according to the first aspect, it has a temperature sensor such as a pyrometer or a thermal imaging camera for measuring the surface temperature of the substrate. This can optionally be used for process control by means of a feedback control.

According to an embodiment of the heating device according to the first aspect, it is manufactured as a module which is independently handleable and can be attached to a device for molecular beam epitaxy.

According to an embodiment of the heating device according to the first aspect - deviating from the above-mentioned embodiment - the elements and parts of the heating device are integral components of a device for molecular beam epitaxy according to the second aspect described below.

A second aspect of the present disclosure relates to an apparatus comprising a substrate receiving device for receiving a substrate to be coated, an electron beam source arranged on a first side of the substrate receiving device for emitting an electron beam in the direction of the substrate receiving device, and one or more evaporation sources which are arranged on a second side of the substrate receiving device opposite the first side.

According to an embodiment of the device according to the second aspect, it further comprises a first chamber in which the substrate receiving device is arranged, and a second chamber in which the electron beam source is arranged and which is connected to the first chamber. In a further embodiment thereof, the device further comprises a first vacuum pump which is connected to the first chamber, a second vacuum pump which is connected to the second chamber, and a vacuum valve between the first chamber and the second chamber.

According to an embodiment of the device according to the second aspect, it further comprises a shield around a region of the electron beam. According to a further embodiment thereof, this shield comprises a water cooling system. According to yet another embodiment thereof, the shield is attached to an inner wall of the first chamber to which the substrate receiving device can be attached.

According to an embodiment of the device according to the second aspect, it is configured for coating, vapor deposition or molecular beam epitaxy.

A third aspect of the present disclosure relates to a method in which a substrate to be coated is arranged between an electron beam source and one or more evaporation sources, and an electron beam is directed onto the back surface of the substrate in order to heat the substrate.

According to an embodiment of the method according to the third aspect, an opening angle of the electron beam is specifically adjusted and/or the electron beam is deflected in a lateral direction.

According to an embodiment of the method according to the third aspect, the substrate is rotated about a central axis.

According to an embodiment of the method according to the third aspect, it is configured for coating, vapor deposition or molecular beam epitaxy.

A fourth aspect of the present disclosure relates to a use of an electron beam source in an apparatus for coating, vapor deposition or molecular beam epitaxy, in which use an electron beam is emitted from the electron beam source and directed onto the back surface of the substrate for heating a substrate to be coated.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the embodiments. Other embodiments and many of the intended advantages of the embodiments will be readily appreciated as they become better understood by reference to the following detailed description.

• 1 zeigt einen Längsschnitt durch eine Ausführungsform einer Vorrichtung für Molekularstrahlepitaxie mit einer Elektronenstrahlquelle für die Beheizung des zu beschichtenden Substrats.

The elements in the drawing are not necessarily to scale.

• 1 shows a longitudinal section through an embodiment of a device for molecular beam epitaxy with an electron beam source for heating the substrate to be coated.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part of this document, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. In this context, directional terms such as "above", "bottom", "front", "back", etc., is used with reference to the orientation of the figure(s) being described. Since the components of the embodiments can be positioned in a number of different orientations, the directional terminology used is for the purpose of illustration and is not limiting. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

It is understood that the features of the various exemplary embodiments described herein may be combined with one another unless expressly stated otherwise.

The terms "connected", "attached", "coupled" and/or "electrically connected/coupled" used in this description do not mean that the elements or layers must be in direct contact with each other; intermediate elements or layers may be provided between the "connected", "attached", "coupled" and/or "electrically connected/coupled" elements. However, according to the disclosure, the above terms may also have the specific meaning that the elements or layers are in direct contact with each other, i.e. that no intermediate elements or layers are provided between the "connected", "attached", "coupled" and/or "electrically connected/coupled" elements.

Furthermore, the word "over" used in reference to a part, element, or layer of material that is formed or disposed "over" a surface may be used herein to mean that the part, element, or layer of material is disposed "indirectly upon" the implied surface (e.g., placed, formed, deposited, etc.), with one or more additional parts, elements, or layers disposed between the implied surface and the part, element, or layer of material. However, the word "over" used in reference to a part, element, or layer of material that is formed or disposed "over" a surface may optionally also have the specific meaning that the part, element, or layer of material is disposed "directly," i.e., in direct contact with the implied surface (e.g., placed, formed, deposited, etc.).

DETAILED DESCRIPTION

1 shows a longitudinal section through an embodiment of a device for molecular beam epitaxy with an electron beam source for heating the substrate to be coated.

The 1 The device shown for molecular beam epitaxy has a first chamber 100 (coating chamber), in the interior 2 of which a substrate receiving plate 5 is arranged for receiving a substrate 4 to be coated and in which a high vacuum can be generated by means of the connected pump 10. In an upper horizontal wall there is an opening to which a second chamber 200 is flanged, which contains an electron beam source 1. The second chamber 200 can be separated from the first chamber 100 in terms of vacuum technology by an (ultra-high) vacuum valve 7.

The substrate receiving plate 5 is attached to an annular shield 6, which in turn is attached with its upper end to an upper horizontal inner wall of the first chamber 100. The substrate receiving plate has a central opening to which a substrate 4 can be attached. The substrate 4 can be shaped as a substrate plate and can be, for example, a wafer made of Si, other semiconductor materials such as GaAs, GaN, AlN, etc., or also of materials such as sapphire (Al2O3, strontium titanate (SrTi03), magnesium oxide and other high-melting oxides. The substrate 4 can be metallized on the back. The front surface of the substrate 4 faces evaporation sources 8, which are arranged within the first chamber 100 below the substrate receiving surface, and the rear surface of the substrate 4 faces the upper opening of the first chamber 100 and thus the second chamber 200 and the electron beam source 1. Several evaporation sources 8 can be arranged radially so that the substrate 4 can be coated with different materials from below.

The substrate receiving plate 5 is attached to a lower horizontal end of the annular shield 6. The shield 6 is preferably made of a metal. Since the irradiation of the substrate 4 by the electron beam also leads to a strong heating of the substrate receiving plate 5, it may prove desirable or even necessary to form the shield 6 as a hollow space and to provide it with a water cooling system that is connected to an external circuit.

The shield 6 has at its lower end a horizontal inner annular collar which has an inner opening for the passage of the electron beam to the substrate. An additional heater 11 in the form of one or more heating wires can be attached between a lower surface of this collar and the substrate receiving plate 5. This heater 11 can be used as an additional heater to the electron beam heater, but can also be used, for example, to preheat the substrate, particularly at low temperatures. However, it can also be used in cases where high substrate temperatures are not required and the electron beam heater can therefore be dispensed with.

The substrate receiving plate 5 can in particular be mounted so as to be rotatable about a central axis, as indicated by the oval with an arrow below the substrate receiving plate 5. The central axis can, for example, be a cylindrical axis of symmetry which runs through the electron beam source 1 and through a center point of the substrate 4 or the opening in the substrate receiving plate 5. The rotatability of the substrate receiving plate 5 can contribute to the energy transfer as a result of the absorption by the electron beam taking place in a spatially homogeneous manner to the substrate 4 and thus the heat in the substrate 4 is also generated in a spatially homogeneous manner. The rotatability also serves above all to homogenize the front-side coating process.

The electron beam source 1 is configured such that the electron beam has a variable opening angle and/or can be deflected in a lateral direction. This can also be used, if necessary in combination with the rotatable substrate support plate 5, to achieve a homogeneous temperature distribution on the substrate 4. However, this feature can also be used to generate defined, local temperature distributions or inhomogeneities on the substrate 4.

In a method according to the third aspect, a substrate to be coated is arranged between an electron beam source and one or more evaporation sources and an electron beam is directed onto the rear surface of the substrate in order to heat the substrate.

For the implementation of the procedure, the 1 The device shown can be used. However, the process can also be used in other vapor deposition or coating systems.

The method can be carried out by specifically adjusting an opening angle of the electron beam and/or deflecting the electron beam in a lateral direction so that the electron beam is scanned over the substrate. At the same time or independently, the substrate can be rotated about a central axis.

The substrate is irradiated from the back with a more or less focused electron beam and thus heated up. The type of energy source (particle radiation) makes the energy transfer to the substrate very efficient. In order to achieve a homogeneous temperature distribution on the substrate, the electron beam can either be expanded in a defined manner or scanned on the substrate using rapid beam deflection. Very high temperatures can be reached on the substrate in a vacuum but also in a reactive environment, e.g. oxygen and/or ozone. A prior metallization of the back of the substrate is helpful, but not absolutely necessary.

• - Sehr effizienter Energieübertrag auf das Substrat
• - Sehr hohe Substrattemperaturen sind erreichbar
• - Die Temperaturverteilung auf dem Substrat kann durch die flexibel veränderbare Strahlablenkung und Strahlmodulation gezielt lokal beeinflusst werden. Sehr homogene Temperaturverteilungen, aber auch definierte, lokale Temperaturverteilungen auf dem Substrat, sind erreichbar.
• - Die Temperaturverteilung kann mittels Pyrometer oder mit einer Wärmebildkamera gemessen und dann über eine Feedbackregelung gezielt an die Prozessanforderungen angepasst werden.
• - Mit einer differentiellen Pumpstufe kann die Vorrichtung auch bei relativ hohem Prozessdruck betrieben werden. Dies kann sich insbesondere bei Oxid- oder Nitrid-MBE als wichtig erweisen.
• - Speziell bei niedrigen Temperaturen kann mit einem Drahtheizer, d.h. per zusätzlicher Strahlungsheizung, das Substrat vorgeheizt oder alternativ geheizt werden.

The advantages of the method carried out with the aid of the device shown are in particular:

• - Very efficient energy transfer to the substrate
• - Very high substrate temperatures can be achieved
• - The temperature distribution on the substrate can be influenced locally using the flexibly adjustable beam deflection and beam modulation. Very homogeneous temperature distributions, but also defined, local temperature distributions on the substrate, can be achieved.
• - The temperature distribution can be measured using a pyrometer or a thermal imaging camera and then adapted to the process requirements using feedback control.
• - With a differential pumping stage, the device can also be operated at relatively high process pressure. This can be particularly important for oxide or nitride MBE.
• - Especially at low temperatures, the substrate can be preheated or alternatively heated using a wire heater, i.e. by additional radiant heating.

Although specific embodiments have been shown and described herein, those skilled in the art will recognize that the specific embodiments shown and described may be replaced by a variety of alternative and/or equivalent other implementations without affecting the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments described herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims (17)

Heating device for heating a substrate to be coated, comprising - a substrate receiving device (5) for receiving a substrate (4) which is to be coated on a first front surface; and - an electron beam source (1) for emitting an electron beam bundle in the direction of a second rear surface of the substrate. Heating device according to Claim 1 , in which - the substrate receiving device (5) is designed as a substrate receiving plate (5). Heating device according to Claim 1 or 2 , in which - the substrate receiving device (5) is rotatable about a central axis. Heating device according to one of the preceding claims, in which the electron beam source (1) is configured such that the electron beam has a variable opening angle and/or is deflectable in a lateral direction. Heating device according to one of the preceding claims, further comprising - an additional heater (11) of the substrate. Heating device according to Claim 5 , in which the additional heating (11) is provided by a heating wire or a radiant heater. Device comprising - a substrate receiving device (5) for receiving a substrate (4) to be coated; - an electron beam source (1) arranged on a first side of the substrate receiving device (5) for emitting an electron beam bundle in the direction of the substrate receiving device (5); and - one or more evaporation sources (8) which are arranged on a second side of the substrate receiving device (5) opposite the first side. Device according to one of the preceding claims, further comprising - a first chamber (100) in which the substrate receiving device is arranged, and - and a second chamber (200) in which the electron beam source (1) is arranged and which is connected to the first chamber (100). Device according to Claim 8 , further comprising - a first vacuum pump (10) connected to the first chamber (100); - a second vacuum pump (9) connected to the second chamber (200); and - a vacuum valve (7) between the first chamber (100) and the second chamber (200). Apparatus according to any preceding claim, further comprising a shield (6) around a region of the electron beam. Device according to Claim 10 , wherein the shield (6) comprises water cooling. Device according to one of the Claims 7 until 11 , wherein the shield (6) is attached to an inner wall of the first chamber (100) and to which the substrate receiving device (5) can be fastened. Device according to one of the Claims 7 until 12 which is configured for coating, evaporation or molecular beam epitaxy. Method in which a substrate to be coated is arranged between an electron beam source and one or more evaporation sources, and an electron beam bundle is directed onto the rear surface of the substrate in order to heat the substrate. Procedure according to Claim 14 , in which an opening angle of the electron beam is specifically adjusted and/or the electron beam is deflected in a lateral direction. Procedure according to Claim 14 or 15 , in which the substrate is rotated around a central axis. Use of an electron beam source in a device for coating, vapor deposition or molecular beam epitaxy, in which an electron beam bundle is emitted by the electron beam source and directed onto the rear surface of the substrate for the purpose of heating a substrate to be coated.

Images