EP3899085A1

EP3899085A1 - Vapor deposition apparatus and method for coating a substrate in a vacuum chamber

Info

Publication number: EP3899085A1
Application number: EP18826382.6A
Authority: EP
Inventors: Andreas Lopp; Stefan Bangert; David Ishikawa; Bahubali S. UPADHYE; Sumedh Acharya; Visweswaren Sivaramakrishnan
Original assignee: Applied Materials Inc
Current assignee: Elevated Materials Germany GmbH
Priority date: 2018-12-21
Filing date: 2018-12-21
Publication date: 2021-10-27
Also published as: CN113227436A; KR20210103546A; JP2023075126A; JP2022513996A; JP7572475B2; JP7309882B2; KR102819779B1; WO2020126041A1; KR102680671B1; KR20240104223A

Abstract

A vapor deposition apparatus is described. The vapor deposition apparatus includes a vacuum chamber having chamber walls; a temperature controlled shield configured to shield the chamber walls; a heat shield facing a substrate to be coated, the heat shield having one or more openings; and an evaporator at least partially within the vacuum chamber, the evaporator comprising: one or more nozzles extending through the one or more openings.

Description

VAPOR DEPOSITION APPARATUS AND METHOD FOR COATING A SUBSTRATE IN A VACUUM CHAMBER

TECHNICAL FIELD [0001] Embodiments of the present disclosure relate to substrate coating by thermal evaporation in a vacuum chamber. Embodiments of the present disclosure further relate to condensates formed on surfaces of a vacuum deposition apparatus. Specifically, embodiments relate to a vapor deposition apparatus, and a method for coating a substrate in a vacuum chamber.

BACKGROUND

[0002] Various techniques for deposition on a substrate, for example, chemical vapor deposition (CVD) and physical vapor deposition (PVD) are known. For deposition at high deposition rates, thermal evaporation may be used as a PVD process. For thermal evaporation, a source material is heated up to produce a vapor that may be deposited, for example, on a substrate. Increasing the temperature of the heated source material increases the vapor concentration and can facilitate high deposition rates. The temperature for achieving high deposition rates depends on the source material physical properties, e.g. vapor pressure as a function of temperature, and substrate physical limits, e.g. melting point.

[0003] For example, the source material to be deposited on the substrate can be heated in a crucible to produce vapor at an elevated vapor pressure. The vapor can be transported from the crucible to a coating volume in a heated manifold. The source material vapor can be distributed from the heated manifold onto a substrate in a coating volume, for example, a vacuum chamber.

[0004] Surfaces of the components, e.g. the vacuum chamber walls of vacuum chamber, may be exposed to the evaporated source material and may be coated. Frequent maintenance to remove condensates is not practical for high volume manufacturing, e.g. web coating on thin foils.

[0005] Further, source material on deposition apparatus components, which are not intended to be coated, may become contaminated and/or unsalvageable. Accordingly, costs for operating a vacuum deposition apparatus may be further increased due to inefficient source material utilization.

[0006] Accordingly, it is advantageous to have a vapor deposition apparatus, a method of evaporating material, and a method for coating a substrate in a vacuum chamber, for which maintenance cycles can be reduced and/or the minimum interval between preventative maintenance time cycles can be reduced. Further, source material utilization is advantageously improved. Thus, for example, production costs may be reduced.

SUMMARY [0007] In light of the above, a vapor deposition apparatus and a method for coating a substrate in a vacuum chamber according to the independent claims are provided. Further aspects, advantages and features of the present disclosure are apparent from the description and the accompanying drawings.

[0008] According to one embodiment, a vapor deposition apparatus is provided. The vapor deposition apparatus includes a vacuum chamber having chamber walls; a temperature controlled shield configured to shield the chamber walls; a heat shield facing a substrate to be coated, the heat shield having one or more openings; and an evaporator at least partially within the vacuum chamber, the evaporator comprising: one or more nozzles extending through the one or more openings.

[0009] According to one embodiment, a method for coating a substrate in a vacuum chamber is provided. The method includes evaporating material in the vacuum chamber; shielding at least a portion of an evaporator with a heat shield, the heat shield having openings forming passages; and shielding chamber walls of the vacuum chamber with a temperature controlled shield, wherein a temperature of the evaporator is higher than a temperature of the temperature controlled shield.

[0010] According to one embodiment, a method for coating a substrate in a vacuum chamber is provided. The method includes evaporating material in the vacuum chamber; shielding chamber walls of the vacuum chamber with a temperature controlled shield, wherein a temperature of the evaporator is higher than a temperature of the temperature controlled shield; and shielding at least a portion of an evaporator with a heat shield being passively heated and wherein the temperature of the evaporator is higher than the temperature of the heat shield.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. 1A shows a schematic view of a vapor deposition apparatus having one or more temperature controlled shields or heat shields according to embodiments of the present disclosure;

FIG. IB shows a schematic view of a further vapor deposition apparatus having one or more temperature controlled shields or heated shields or heat shields according to embodiments of the present disclosure; FIG. 2 shows a perspective view of a frame-like heated shield and a heat shield according to embodiments of the present disclosure; FIG. 3 shows a schematic view of a further vapor deposition apparatus having one or more temperature controlled shields or heated shield or heat shields according to embodiments of the present disclosure;

FIG. 4 shows a schematic view of a further vapor deposition apparatus being a roll-to-roll deposition apparatus according to embodiments of the present disclosure; and

FIG. 5 shows a flowchart for illustrating a method of coating a substrate in a vacuum chamber according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0012] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0013] Within the following description of the drawing, the same reference numbers refer to the same or similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one applies to a corresponding part or aspect in another embodiment as well.

[0014] According to embodiments of the present disclosure, apparatuses and methods for coating by evaporation in the vacuum chamber are provided. For depositing a substrate with source material by evaporation, the source material may be heated above the evaporation or sublimation temperature of the source material. Embodiments of the present disclosure result in reduced condensation on surfaces, for example surfaces other than the substrate that may have lower temperatures. Such surfaces may for example be a chamber wall.

[0015] Embodiments of the present disclosure provide a temperature controlled coating chamber environment, for example, to prevent coating (e.g. stray coating) on shields, masks, and chamber walls. Accordingly, advantageously improved substrate coating quality and yield in addition to longer operation times between preventative maintenance cycles can be provided.

[0016] According to one embodiment, a method for coating a substrate in a vacuum chamber is provided. The method includes evaporating source material in the vacuum chamber. At least a portion of an evaporator is shielded with a heat shield, the heat shield having openings forming passages. Chamber walls of the vacuum chamber are shielded with a temperature controlled shield, wherein the temperature of the evaporator is higher than a temperature of the shield.

[0017] According to another embodiment, a vapor deposition apparatus is provided. The vapor deposition apparatus includes a vacuum chamber having chamber walls. An evaporator is provided within the vacuum chamber. A heat shield arranged to face a substrate to be coated and having openings forming passages is provided. The evaporator comprises nozzles extending through the passages of the heat shield. The apparatus further includes a temperature controlled shield between an interior of the vacuum chamber and the chamber walls.

[0018] Fig. 1A shows a vacuum deposition apparatus 100. The vacuum deposition apparatus 100 includes a vacuum chamber 105. The vacuum chamber 105 includes one or more chamber walls 150. According to some embodiments, an evaporator 135 can be provided in the vacuum chamber 105 or can at least partially be provided in the vacuum chamber 105. FIG 1A shows a distributor 133 of an evaporator. The distributor may distribute vapor provided in the distributor, for example, through an inlet opening 101. The distributor may have one or more openings 182. Vapor of the source material to be deposited can exit the distributor 133 through the openings. The source material is deposited on a substrate 110. According to some embodiments, which can be combined with other embodiments described herein, one or more nozzles 136 can be provided at the one or more openings 182, respectively.

[0019] In FIG. 1A, the distributor 133 is provided at a lower portion of the vacuum chamber 105 and the substrate 110 is provided at an upper portion. The source material to be deposited is guided from the lower portion to the upper portion. One or more side walls 150 extend from the distributor 133, i.e. from the lower portion of the vacuum chamber 105, to a substrate position, i.e. an upper portion of the vacuum chamber 105. According to some embodiments, which can be combined with other embodiments described herein, one or more chamber walls of the vacuum chamber can be provided between the evaporator and the substrate position. The sidewalls 150 can be protected from coating by a temperature controlled shield or frame 140. The temperature controlled shield may be heated. Accordingly, material or source material being deposited on the heated shield can be re-evaporated.

[0020] According to some embodiments, the temperature controlled shield or heated shield may cover one or more chamber walls. Particularly, the heated shield may cover the plurality of chamber walls. According to some embodiments, which can be combined with other embodiments described herein, the heated shield can be a frame or a temperature controlled frame. For example, the heated shield may surround a deposition zone, through which evaporated material is guided towards the substrate. Furthermore, the heated shield can form a continuous surface. According to embodiments, the heated shield may be thermally conductive to facilitate a homogenous or even heating of the heated shield.

[0021] According to embodiments which can be combined with other embodiments described herein, the vapor deposition apparatus comprises a controller connected to a heater section heating the temperature shield or heated shield. The controller controls the heated shield temperature to be lower than the temperature of the evaporator. The heater section can be configured to heat up the heated shield, in particular to generate heat wherein the generated heat is transferred to the heated shield. The heater section can be, for example, arranged at the heated shield. Being arranged at the heated shield can be also understood as being in direct and/or physical contact with the heated shield. The heater section can, for example, include a heating coil, a heating tube, heating struts, heating lamps or the like.

[0022] The heater section can be arranged on the outer surface of the heated shield, wherein the outer surface of the heated shield faces the chamber walls and the inner surface of the heated shield faces the interior of the vacuum chamber. The heater section can also be integrated within the heated shield, in particular be arranged within the heated shield.

[0023] FIG. IB shows a schematic view of a further vapor deposition apparatus having one or more frames or heated shields according to embodiments of the present disclosure. A material 170, i.e. a source material, to be deposited is evaporated within the crucible 160 by heating the material 170. The material 170 can include, for example, metal, in particular lithium, metal alloys, and other vaporizable materials or the like which have a gaseous phase under given conditions. According to yet further embodiments, additionally or alternatively, the material may include magnesium (Mg), ytterbium (YB) and lithium fluoride (LiF). The evaporated material generated in the crucible 160 can enter a distributor 133 along the direction represented by the arrow 137c. The distributor 133 can, for example, include a channel or a tube which provides a transport system to distribute the evaporated material along the width and/or the length of the deposition apparatus. The distributor can have the design of a“shower head reactor”.

[0024] As exemplary shown, the evaporated source material can be guided within the distributor 133 towards the respective chamber walls 150 along the directions 137a and 137b. The direction 137a and 137b can be essentially parallel to a flat substrate 110, in particular parallel to the surface 110a of a flat substrate 110. In the event of a coating drum of a roll-to-roll coater, the direction 137a and 137b may be parallel to an axis of the coating drum or may be parallel to a tangent of the coating drum at the shortest distance of the source and the drum. The evaporated material is ejected from the evaporator 135 by means of nozzles 136 to the interior 145 of the vacuum chamber 105. The nozzles 136 are arranged within the openings 182 of the heat shield 180. The evaporated material 185 ejected by the nozzles 136 is deposited on the surface 110a of the substrate 110 to form a coating for the substrate 110.

[0025] The heat shield 180 reduces the radiant heat coming from the evaporator, for example, the distributor 133, towards the substrate. According to embodiments of the present disclosure, the heat shield 180 includes openings 182. According to some embodiments, which can be combined with other embodiments described herein, the nozzles 136 of the distributor 133 can extend through the openings of the heat shield 180.

[0026] According to some embodiments, which can be combined with other embodiments described herein, the opening of the heat shield may be larger than a corresponding dimension of the nozzle. According to some embodiments, which can be combined with other embodiments described herein, the opening size of the nozzle can be large enough as compared to the nozzle dimension to further allow for thermal expansion. Additionally or alternatively, a nozzle of the distributor or the evaporator may not be in mechanical contact with the heat shield, particularly not in direct mechanical contact. Thus, temperature transfer from the evaporator to the heat shield by conductance can be reduced or avoided, for example, the heat shield may be supported with thermal insulators.

[0027] According to some embodiments, which can be combined with other embodiments described herein, the nozzles protrude from the heat shield. In particular the nozzles can protrude through the openings and protrude from the surface of the heat shield. With reference to the exemplary embodiment of FIG. IB, the ratio between the nozzle lengths defined by the upper ends 136a of the nozzles 136 and the side wall 134 of the distributor 133, and a distance defined by the heat shield 180 and the side wall 134 can be at least 1.1, in particular at least 1.3, or more particularly at least 1.5. Additionally or alternatively, the nozzle length is advantageously short, e.g. with a ratio of 3 or below to provide good heat conductance to the nozzle tip.

[0028] According to embodiments which can be combined with other embodiments described herein, the ratio between the area of the side wall of the distributor and the area of a surface of the interior of the vacuum chamber covered by the nozzles is at least 10:1, in particular at least 20:1 or more particularly over 50:1. By having a ratio between the side wall of the distributor and the nozzle area as described herein, the pressure within the distributor can be much higher than the pressure within the interior of the vacuum chamber. In particular, the pressure within the distributor can be at least 10 times higher than the pressure within the interior of the vacuum chamber, in particular at least 50 times higher, or more particularly more than 100 times higher.

[0029] According to embodiments which can be combined with other embodiments describe herein, the evaporated material can include or can consist of lithium, Yb, or LiF. According to embodiments which can be combined with other embodiments described herein, the temperature of the evaporator and/or of the nozzles can be at least 600 °C, or particularly between 600 C° and 1000 C°, or more particularly between 600 °C and 800 °C. According to embodiments which can be combined with other embodiments described herein, the temperature of the heated shield can be between 450 °C and 550 °C, particularly around 500 °C with a deviation of +/ 10 °C.

[0030] According to embodiments which can be combined with other embodiments described herein, the temperature of the heated shield is lower than the temperature of the evaporator by at least 100 °C, in particular is lower up to 300 °C, more particularly is lower by at least 100 °C and up to 300 °C.

[0031] According to embodiments, which can be combined with other embodiments described herein, the heat shield comprises two or more heat shield layers. The heat shield layers can be arranged spaced apart from each other. By arranging the heat shield layers spaced apart from each other, the heat shielding effect can be increased. Furthermore, the heatshield layers can also be made of different materials having different heat conduction coefficients.

[0032] The temperature of the lower heat shield layer facing the side wall of the distributor can be higher than the upper heat shield layer facing the substrate. The heat shield layers can be, for example, arranged, in particular attached on the side wall of the distributor by fixing pins. The pins can include heat isolating materials like isolating alloys or ceramics. According to some embodiments, which can be combined with other embodiments described herein, the heat shield includes 1 to 10 heat shield layers. According to embodiments, one heat shield layer can for example be a metal sheet or a steel sheet. According to embodiments, the thickness of a heat shield layer can be between 0.1mm and 1mm, more particularly between 0.2 mm and 0.5 mm.

[0033] According to embodiments, which can be combined with other embodiments described herein, the heat shield is arranged between the side wall and the substrate. The heat shield can be closer to the evaporator than to the substrate.

[0034] According to embodiments, which can be combined with other embodiments described herein, the heat shield is passively heated by the side wall of the evaporator, for example by radiation. The heat shield can, for example, be heated by the radiant heat from the side wall of the evaporator, in particular, of the distributor. The term“passively” can be understood that the heat shield is heated by other components of the vacuum deposition apparatuses exclusively. The heat shield can be, for example, configured to absorb, to reflect and/or to shield the heat, in particular the radiant heat of the side wall of the evaporator. By lowering the heat directed towards the substrate by the heat shield as described herein, the substrate can be arranged closer to the evaporator which enables a smaller and more compact design of the vacuum chamber. [0035] Furthermore, by heating the heat shield, the material which is deposited on the surface of the heat shield, for example, by stray coating can also be re-evaporated. The stray coated material on the heat shield can be advantageously removed by re-evaporation as described herein. Furthermore, by re-evaporating material from the heat shield, the coating on the substrate can also be made more uniform.

[0036] FIG. 2 shows a perspective view of a frame-like shielding and a heat shield 180 according to embodiments of the present disclosure. The heated shield forms a frame 140 which is rectangular and/or square shaped. The frame 140 is arranged on top of the heat shield 180. The heat shield 180 can form a flat or even upper surface 183. The frame 140 encloses the outer perimeter of the heat shield 180. The frame 140 is exposed with the inner side 142 of the frame 140 to the interior of the vacuum chamber. The distance between the upper edge 143 of the frame 140 with respect to the upper surface 183 of the heat shield 180 can be greater than the distance between the upper edge of the frame 140 and the substrate (not shown). According to some embodiments, which can be combined with other embodiments described herein, The shape of the frame and/or the heat shield is configured to provide a plurality of openings or nozzles. For example, at least four rows of openings or nozzles can be provided. Additionally or alternatively, an array or pattern of openings and/or nozzles may be provided, wherein four or more openings and/or nozzles are arranged in two different directions, e.g. orthogonal directions.

[0037] According to embodiments which can be combined with other embodiments herein, the heated shield covers a major portion of the chamber walls facing to the interior of the vacuum chamber between the evaporator and the substrate. Therein the term“a major portion” can be understood such that the heated shield covers at least 50%, in particular at least 75%, or more particularly over 90% of the area of the total chamber wall area between the evaporator and the substrate.

[0038] The controller is configured to actively control the temperature of the heated shield. Actively controlling can include controlling the electrical power supplied to the heater sections and/or can include controlling the flow rate of a heating liquid supplied to the heater sections. The controller can be further configured to measure the temperature within the evaporator, the crucible, the heat shield and/or the heated shield. Furthermore, the controller can also be configured to measure the pressure within the evaporator and the interior of the vacuum chamber. Moreover, the controller can be configured to control the evaporation rate within the crucible and/or the evaporator and/or the deposition rate of the evaporated material on the substrate. The respective parameters can be, for example, the temperature, the rate, and pressure. The respective parameters can be, for example, measured by sensors arranged at the respective components of the vacuum chambers.

[0039] FIG. 3 shows a schematic view of a further vapor deposition apparatus having one or more frames or shields according to embodiments of the present disclosure. The apparatus have in contrast to the vapor deposition apparatus shown in FIG. 1A a vertical processing direction. The vacuum chamber 105 is connected to a vacuum pump 210. The vertically oriented distributor 133 is covered by the heat shield 180 facing the surface 100a of the substrate 110. The material is heated in a crucible 160 and flows through the distributor and enters the interior 145 of the vacuum chamber 105 through the nozzles 136. The material can be re-evaporated by the heat shield 140 as well as by the heat shield 180 according to embodiments as described herein.

[0040] FIG. 4 shows a schematic view of a further vapor deposition apparatus 400 being a roll-to-roll deposition apparatus according to embodiments of the present disclosure. The substrate to be deposited can be a web 410 or a foil which is guided by two drums 450 through the vacuum chamber 105. The web 410 can be moved along the interior 145 of the vacuum chamber facing the side wall 134 and the nozzles 136 of the distributor 133. The substrate in this exemplary vapor deposition apparatus 400 can be a web 410. The components of the vapor deposition apparatuses and processes are similar to the components and the processes described in other embodiments herein. [0041] FIG. 5 shows a flowchart for illustrating a method of coating a substrate in a vacuum chamber according to embodiments described herein. As illustrated by box 501, material is evaporated, for example by an evaporator including a crucible as described herein. As illustrated by box 502, at least a portion of an evaporator is shielded with a heat shield according to embodiments as described herein. As illustrated in box 503, the chamber walls of the vacuum chamber are shielded with a temperature controlled heated shield, wherein a temperature of the evaporator is higher than a temperature of the heated shield according to embodiments as described herein.

[0042] According to embodiments which can be combined with other embodiments described herein, the temperature of the temperature controlled shield is actively controlled. According to embodiments which can be combined with other embodiments described herein, the temperature of the temperature controlled or heated shield is set lower than the temperature of the evaporator.

[0043] The nozzles extending through the passages of the substrate of the heat shield provide outlets for the evaporated material, wherein the evaporated material can be transferred from the evaporator to the interior of the vacuum chamber. The nozzles can enable a difference in pressure, in particular in vapor pressure, between the interior of the chamber and the evaporator. In particular, the nozzles can enable the gas pressure within the interior of the vacuum chamber to be lower than the vapor pressure within the evaporator.

[0044] Embodiments of the present disclosure have several advantageous effects. The temperature controlled shield can improve the deposition process within the interior of the vacuum chamber. The temperature of the temperature controlled shield can be high enough to reduce the condensation of the evaporated material on the chamber walls. Furthermore, the temperature of the temperature controlled or heated shield can also be low enough to keep the heat load for the substrate low. [0045] Furthermore, stray coated material on the heated shield can be re evaporated to be deposited on the substrate. Moreover, by re-evaporating material from the heat shield, the coating on the substrate can also be made more uniform. By reducing the stray coating on the chamber walls by the heated shield, the vacuum deposition chamber can be operated with higher throughputs of evaporated material which further enhance the production rate of coated substrates.

[0046] The heat shield according to embodiments described herein can lower the heat load from the evaporator directed towards the substrate as described herein, and the substrate can be arranged closer to the evaporator which enables a smaller and more compact design of the vacuum chamber. Further, the evaporator can be operated with higher temperatures without damaging the substrate by radiant heat. Furthermore, the material loss due to the stray coating on other components than the substrate inside the vacuum chamber, for example on masks, shields and chamber walls or the like, can be reduced by the re-evaporation on the heat shield and the heated shield. Less stray coating can lead to higher machine uptime between maintenance cycles and can result in a higher material utilization.

[0047] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

Claims

1. A vapor deposition apparatus, comprising:

a vacuum chamber having chamber walls;

a temperature controlled shield configured to shield the chamber walls; a heat shield facing a substrate to be coated, the heat shield having one or more openings; and

an evaporator at least partially within the vacuum chamber, the evaporator comprising:

one or more nozzles extending through the one or more openings.

2. The vapor deposition apparatus according to claim 1, wherein the openings of the heat shield form passages and the nozzles extend through the passages.

3. The vapor deposition apparatus according to any of claims 1 to 2, wherein a temperature of the evaporator is higher than the temperature of the heat shield.

4. The vapor deposition apparatus according to any of claims 1 to 3, further comprising:

a controller connected to a heater section heating the temperature controlled shield, the controller controls the temperature of the temperature controlled shield to be lower than the temperature of the evaporator.

5. The vapor deposition apparatus according to any of claims 1 to 4, wherein the heat shield comprises two or more heat shield layers.

6. The vapor deposition apparatus according to any of claims 1 to 5, the evaporator having a side wall facing the substrate, wherein the nozzles are provided at the side wall.

7. The vapor deposition apparatus according to claim 6, wherein the heat shield is arranged between the side wall and the substrate.

8. The vapor deposition apparatus according to any of claims 6 to 7, wherein the heat shield is passively heated by the side wall of the evaporator.

9. A method for coating a substrate in a vacuum chamber, comprising: evaporating material in the vacuum chamber; shielding at least a portion of an evaporator with a heat shield, the heat shield having openings forming passages; and shielding chamber walls of the vacuum chamber with a temperature controlled shield, wherein a temperature of the evaporator is higher than a temperature of the temperature controlled shield.

10. The method according to claim 9, further comprising:

actively controlling a temperature of the temperature controlled shield.

11. The method according to claim 10, wherein the temperature of the temperature controlled shield is set lower than the temperature of the evaporator.

12. The method according to any of claim 9 to 11, wherein the heat shield is passively heated by radiation.

13. The method according to any of claims 9 to 12, further comprising: setting a pressure inside the evaporator, the pressure inside the evaporator being higher than a pressure inside the vacuum chamber.

14. The method according to any of claims 9 to 13, wherein the material is re-evaporated by the temperature controlled frame.

15. A method for coating a substrate in a vacuum chamber, comprising: evaporating material in the vacuum chamber; shielding chamber walls of the vacuum chamber with a temperature controlled shield, wherein a temperature of the evaporator is higher than a temperature of the temperature controlled shield; and shielding at least a portion of an evaporator with a heat shield being passively heated and wherein the temperature of the evaporator is higher than the temperature of the heat shield.