Method and sputter deposition apparatus for depositing layers of thin film transistors on a substrate - Patent Application 20070122997

Abstract

A method (480, 580) of depositing layers of a thin film transistor on a substrate using a sputter deposition source including at least one first electrode pair and at least one second electrode pair, comprising: moving the substrate to a first vacuum chamber (482, 582); depositing a first one of the layers on the substrate by supplying a bipolar pulsed DC voltage to at least one first electrode pair, wherein a first material of the first layer comprises a first metal oxide (484, 584); moving the substrate from the first vacuum chamber to a second vacuum chamber without breaking vacuum (486, 586); and depositing a second one of the layers on the first layer by supplying a bipolar pulsed DC voltage to at least one second electrode pair, wherein a second material of the second layer comprises a second metal oxide, the second material being different from the first material (488, 588).

Description

[Technical Field]

[0001] The present disclosure relates to the fabrication of semiconductor devices, particularly thin film transistors. The present disclosure relates to methods for depositing layers of thin film transistors on substrates. The present disclosure further relates to sputter deposition apparatus. [Background technology]

[0002] Forming thin layers on substrates is a problem particularly relevant in the field of thin film transistors (TFTs). In the manufacture of thin film transistors, one method of forming layers on a substrate is sputtering. During sputtering, atoms are ejected from the material of the sputter target by bombardment with energetic particles of a plasma (e.g., excited ions of an inert or reactive gas). The ejected atoms can be deposited on the substrate, thus forming a layer of sputtered material on the substrate.

[0003] Known methods for depositing layers onto substrates for the manufacture of thin film transistors utilize static deposition processes in which the substrate is placed in front of sputter electrodes of a deposition source, which may include at least one sputter electrode, such as a sputter cathode carrying a sputter target, or an array of sputter electrodes powered by direct current (DC) for DC sputtering.

[0004] Fabrication of a thin film transistor can involve the deposition of various layers, including, for example, a gate insulating layer, a channel layer to form a channel between the source and drain electrodes, or a source-drain layer to form the source and drain electrodes.

[0005] For example, it remains difficult to provide thin film transistors with uniform and stable performance for display applications. For example, the performance of thin film transistors may become unstable during application of voltage to the thin film transistor and / or under stress, such as high temperature. In particular, the performance of thin film transistors with high carrier mobility may become unstable. For example, it may be difficult to apply thin film transistors with high carrier mobility to high-resolution mobile panels.

[0006] Therefore, there remains a need to provide improved methods for depositing layers of thin film transistors on substrates, as well as sputter deposition apparatus. More specifically, it would be desirable to provide thin film transistors with high carrier mobility and high stability, especially under stress. Summary of the Invention

[0007] In light of the above, there is provided a method for depositing a layer of a thin film transistor on a substrate, and a sputter deposition apparatus according to the independent claims. Further aspects, advantages and features of the present disclosure will be apparent from the dependent claims, the description and the accompanying drawings.

[0008] One aspect of the present disclosure relates to a method for depositing layers of a thin film transistor on a substrate using a sputter deposition source including at least one first electrode pair and at least one second electrode pair, the method including: transferring the substrate to a first vacuum chamber; depositing a first one of the layers on the substrate by supplying a bipolar pulsed DC voltage to at least one first electrode pair, where a first material of the first layer comprises a first metal oxide; transferring the substrate from the first vacuum chamber to a second vacuum chamber without breaking vacuum; and depositing a second one of the layers on the first layer by supplying a bipolar pulsed DC voltage to at least one second electrode pair, where a second material of the second layer comprises a second metal oxide, where the second material is different from the first material.

[0009] A further aspect relates to a sputter-deposition apparatus, particularly a sputter-deposition apparatus for depositing a layer of a thin film transistor on a substrate. The sputter-deposition apparatus includes a first vacuum chamber and a second vacuum chamber arranged to allow a substrate to be transferred between the first and second vacuum chambers without breaking vacuum. The sputter-deposition apparatus includes a sputter-deposition source including at least one first electrode pair and at least one second electrode pair, where the at least one first electrode pair is disposed in the first vacuum chamber and the at least one second electrode pair is disposed in the second vacuum chamber. The sputter-deposition source further includes a power supply arrangement configured to supply a bipolar pulsed DC voltage to the at least one first electrode pair and the at least one second electrode pair. The at least one first electrode pair includes a first target having a first target material, the first target material including a first metal oxide. At least one second electrode pair includes a second target having a second target material, the second target material including a second metal oxide, and the second target material is different from the first target material.

[0010] The embodiments are also directed to apparatus for performing the disclosed methods, including apparatus parts for performing each described method aspect. These method aspects may be performed by hardware components, by a computer programmed by appropriate software, by any combination of the two, or in any other manner. Furthermore, embodiments according to the present disclosure are also directed to methods of operating the described apparatus. Methods of operating the described apparatus include method aspects for performing all of the functions of the apparatus.

[0011] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the disclosure briefly outlined above can be had by reference to embodiments. The accompanying drawings relate to embodiments of the present disclosure and are described below. Exemplary embodiments are shown in the drawings and are described in detail in the following description. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a sputter deposition source according to some embodiments described herein. [Figure 2] 1 is a graph of a bipolar pulsed DC voltage and respective current that may be applied to a pair of electrodes in a sputter deposition source according to some embodiments described herein. [Figure 3] 1 is a schematic diagram of an exemplary thin film transistor including layers deposited by methods or sputter deposition sources according to embodiments described herein. [Figure 4] 1 is a flow diagram illustrating a method according to an embodiment described herein. [Figure 5] 1 is a flow diagram illustrating a method according to a further embodiment described herein. DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference will now be made in detail to various embodiments, examples of which are illustrated in the figures. Each example is provided by way of explanation and not meant to be limiting. For example, features illustrated or described as part of one embodiment can be used on or in combination with other embodiments to yield still further embodiments. This disclosure is intended to include such modifications and variations.

[0014] Within the following description of the drawings, the same reference numbers refer to the same or similar components. Generally, only the differences with respect to the individual embodiments are described. Unless otherwise specified, the description of a part or aspect in one embodiment applies equally to the corresponding part or aspect in another embodiment.

[0015] The process of coating a substrate with the materials described herein generally refers to thin film applications. The terms "coating" and "deposition" are used synonymously. According to some embodiments, coating or deposition is performed by sputtering.

[0016] A sputter-deposition apparatus according to embodiments described herein includes a first vacuum chamber and a second vacuum chamber. The first vacuum chamber and the second vacuum chamber are arranged so that a substrate can be transferred between the first vacuum chamber and the second vacuum chamber without breaking vacuum. In particular, the sputter-deposition apparatus is configured so that a substrate can be moved from the first vacuum chamber to the second vacuum chamber without exposing the substrate to a non-vacuum environment, particularly an environment with atmospheric pressure. The first vacuum chamber can be at least partially separated from the second vacuum chamber by a chamber wall of the first vacuum chamber or the second vacuum chamber. The chamber wall can have a slit opening. The slit opening can be configured so that a substrate, particularly a substrate and a substrate carrier holding the substrate, can be moved from the first vacuum chamber through the slit opening to the second vacuum chamber. In some embodiments, the slit opening can be closable or sealable using a chamber valve.

[0017] According to an embodiment, a sputter deposition apparatus includes a sputter deposition source. The sputter deposition source includes an electrode pair, particularly at least one first electrode pair and at least one second electrode pair. Each electrode of the electrode pair can be configured to provide a target material to be deposited on a substrate. For example, each electrode can include a target, such as a cylindrical target, made of the target material to be deposited on the substrate. Furthermore, each electrode can be configured to be rotatable around its own rotation axis together with the target material. The electrodes of a pair of electrodes can be adjacent electrodes. For example, each electrode pair can include a first electrode and a second electrode spaced apart by a distance of 50 cm or less, particularly 30 cm or less.

[0018] Generally, sputtering can be performed as diode sputtering or magnetron sputtering. Magnetron sputtering is particularly advantageous in that it can increase the deposition rate. The magnet assembly can be positioned within a rotatable electrode. By placing the magnet assembly within a rotatable electrode, i.e., within a cylindrical target, free electrons on the target surface are forced to move within the magnetic field generated by the magnet assembly and cannot escape. The magnet assembly can be rotatable within the electrode. Magnetron sputtering can increase the deposition rate.

[0019] FIG. 1 illustrates an exemplary embodiment of a sputter-deposition apparatus 100. The sputter-deposition apparatus 100 includes a first vacuum chamber 130 and a second vacuum chamber 140. A substrate 110 can be moved from the first vacuum chamber 130 to the second vacuum chamber 140 without breaking vacuum. In particular, the substrate 110 can be held by a substrate carrier. The substrate carrier holding the substrate 110 can move in a downstream direction 112 along a substrate transport track. As shown in FIG. 1 , the substrate 110 can be moved in the downstream direction 112 from the first vacuum chamber 130 to the second vacuum chamber 140 through a slit opening 114 in a chamber wall 116. The sputter-deposition apparatus 100 can be configured to continuously move the substrate 110 during deposition in the first vacuum chamber 130 and during deposition in the second vacuum chamber 140.

[0020] According to some embodiments, the sputter-deposition apparatus is configured to dynamically coat the substrate, particularly in the first vacuum chamber and / or the second vacuum chamber. For example, the sputter-deposition apparatus can be configured to continuously move the substrate along a substrate transport track during layer deposition. In further embodiments, the sputter-deposition apparatus can be configured to statically move the substrate. The substrate can be placed in a coating region, particularly in the first vacuum chamber or the second vacuum chamber, before deposition. After entering the coating region, the sputter-deposition apparatus can be configured to deposit a layer on the substrate. The substrate remains in the coating region during deposition. The sputter-deposition apparatus can be configured to remove the substrate from the coating region after deposition. In particular, the vacuum chamber, e.g., the first vacuum chamber or the second vacuum chamber, can be sealable or closable from the environment or an adjacent vacuum chamber during deposition, e.g., using a chamber valve.

[0021] According to an embodiment, the sputter-deposition source of the sputter-deposition apparatus includes at least one first electrode pair disposed in a first vacuum chamber and at least one second electrode pair disposed in a second vacuum chamber. The at least one first electrode pair and / or the at least one second electrode pair may include at least two or at least three electrode pairs, e.g., exactly two or exactly three electrode pairs. The sputter-deposition source includes a power supply arrangement configured to supply a bipolar pulsed DC voltage to the at least one first electrode pair and the at least one second electrode pair. In the embodiment shown in FIG. 1 , the sputter-deposition apparatus 100 includes a sputter-deposition source including two first electrode pairs 132 disposed in a first vacuum chamber 130 and two second electrode pairs 142 disposed in a second vacuum chamber 140. The first electrode pair 132 and the second electrode pair 142 are supplied with a bipolar pulsed DC voltage by a power supply arrangement 120. The power supply arrangement 120 may include a DC power supply 124 and a pulse unit 122 .

[0022] FIG. 2 is a graph showing a bipolar pulsed DC voltage as a function of time (t) that may be applied to a pair of electrodes in a sputter deposition source according to some embodiments described herein. A first graph 250 shows a first voltage U1 applied to a first electrode of the pair of electrodes, and a second graph 252 shows a second voltage U2 applied to a second electrode of the pair of electrodes. The second voltage U2 may be, for example, an inverted version of the first voltage U1. In an exemplary embodiment, a bipolar square wave or rectangular wave voltage is applied to the pair of electrodes. In practice, the positive and negative portions of the first and second voltages may simply be approximately constant. Corresponding voltages may be applied synchronously to each pair of at least one first electrode pair and at least one second electrode pair.

[0023] Furthermore, the current (I) flowing between the electrodes of a pair of electrodes during operation is shown as a function of time (t) in the first graph 250 of Figure 2. The current may follow the shape of the applied voltage waveform. In particular, the frequency of the current may correspond to the frequency of the applied voltage.

[0024] According to an embodiment, at least one first electrode pair includes a first target having a first target material, the first target material including a first metal oxide. At least one second electrode pair includes a second target having a second target material, the second target material including a second metal oxide. In particular, the second target material is different from the first target material. In an embodiment, at least one of the first target material and the second target material may be a semiconductor.

[0025] In embodiments, a sputter-deposition apparatus can be configured to deposit layers of a thin film transistor on a substrate. In particular, the sputter-deposition apparatus can be configured to deposit layers according to the method embodiments described herein. In particular, the first target material can be configured to deposit a first layer of the layers, where the first material of the first layer comprises a material of the first target material, particularly a first metal oxide of the first target material. The second target material can be configured to deposit a second layer of the layers, where the second material of the second layer comprises a material of the second target material, particularly a second metal oxide of the second target material. In particular, the first target material and the second target material can be configured for depositing a channel layer of a thin film transistor. In some embodiments, the first target material and the second target material can correspond at least essentially to the first material of the first layer and the second material of the second layer, respectively, where the first material and the second material are configured according to the embodiments described herein.

[0026] In some embodiments, the first target and the second target are rotatable targets. As shown in FIG. 1 , the first electrode pair 132 includes a first target 134, and the second electrode pair includes a second target 144. Each of the first target 134 and the second target 144 is a rotatable target. In particular, each of the first target 134 and the second target 144 is rotatable about a respective axis of rotation A.

[0027] According to an embodiment, the sputter-deposition apparatus may include a substrate transport track along which a substrate can be transported. In particular, the substrate can be moved along the substrate transport track to the first vacuum chamber and / or from the first vacuum chamber to the second vacuum chamber. The substrate can be carried along the substrate transport track by a substrate carrier during transport and / or substrate processing, in particular during layer deposition.

[0028] In some embodiments, the sputter-deposition apparatus may include at least one additional vacuum chamber in which at least one additional electrode pair of the sputter-deposition source is disposed. The sputter-deposition apparatus, particularly the substrate transport track of the sputter-deposition apparatus, may be configured to move the substrate from the second vacuum chamber to the at least one additional vacuum chamber without breaking vacuum. The at least one additional electrode pair may include at least one additional target, wherein the at least one additional target includes an additional target material. The additional target material may be different from the second target material, particularly different from the first target material and different from the second target material. In embodiments, the additional target material may have a different carrier mobility and / or a different carrier concentration than the second target material.

[0029] According to an embodiment that can be combined with other embodiments, a method for depositing a layer of a thin film transistor on a substrate is provided. A sputter deposition source including at least one first electrode pair and at least one second electrode pair is used to deposit the layer of the thin film transistor. In particular, a sputter deposition source of a sputter deposition apparatus according to an embodiment described herein can be used to deposit the layer of the thin film transistor.

[0030] FIG. 3 shows an exemplary diagram of a thin film transistor 360. Fabrication of the thin film transistor 360 may include methods of depositing layers of the thin film transistor 360 according to embodiments described herein. The thin film transistor 360 includes a supporting substrate 362. A gate electrode 364 is formed on the supporting substrate 362. A gate insulating layer 366 is deposited on the gate electrode 364. The gate insulating layer 366 includes an insulating material. For example, the gate insulating layer 366 may be made of silicon nitride (SiN x ), silicon oxide (SiO x ), SiO x N (1-x) , materials with high dielectric constant, especially Al x O y , ZrOx , HfO x , or GeO x , or any combination thereof.

[0031] A channel of the thin film transistor 360 may be formed on the gate insulating layer 366. The channel may include a semiconductor material. The channel may be conductive in the on-state of the thin film transistor and non-conductive in the off-state of the thin film transistor. In particular, the channel may be formed by depositing a first layer 368, particularly forming a front channel of the thin film transistor 360, and by depositing a second layer 370, particularly forming a back channel of the thin film transistor 360. The first layer 368 may be formed of a first material, and the second layer 370 may be formed of a second material, where the second material is different from the first material. Each of the first material and the second material may be a semiconductor material. For example, the first layer 368 may include indium gallium zinc oxide (IGZO) in a partially oxidized state, and the second layer 370 may include IGZO in a fully oxidized state. According to another example, the first layer 368 can be formed of a composition of IGZO and a transparent conductive oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide (AZO), and the second layer 370 includes, for example, IGZO without the transparent conductive oxide.

[0032] The thin film transistor 360 further includes a source / drain layer 374. The source / drain layer 374 may include a conductive material. The source / drain layer 374 may include or consist of a metal. For example, the source / drain layer 374 may include Mo, Ti, Ta, Cr, (Ta, Cr), Cu, Ag, Al, alloys thereof, or any combination thereof. The source / drain layer 374 may be structured, for example, by photolithography, to form source and drain electrodes of the thin film transistor 360. The thin film transistor 360 may be further processed by back channel etching. In particular, the back channel, e.g., the second layer 370, may be partially etched. The thin film transistor 360 further includes a passivation layer 376 deposited on the source / drain layer 374.

[0033] 3 shows a particular type of thin film transistor for illustrative purposes, particularly a thin film transistor with an inverted staggered geometry. In some embodiments, the methods and apparatus disclosed herein can be configured to deposit layers of a thin film transistor with an inverted staggered geometry, particularly for fabrication of thin film transistors that include back channel etching. Embodiments of the methods and apparatus described herein can additionally or alternatively be used to deposit layers of thin film transistors other than a inverted staggered geometry.

[0034] 4 shows a flow diagram illustrating a method 480 of depositing a layer of a thin film transistor according to embodiments described herein. At 482, the method 480 includes moving a substrate to a first vacuum chamber. In embodiments, the substrate can be moved to the first vacuum chamber from a load lock chamber or from a previous processing chamber.

[0035] At 484, the method 480 includes depositing a first one of the layers on the substrate by applying a bipolar pulsed DC voltage to at least one first electrode pair, where a first material of the first layer includes a first metal oxide. In some embodiments, the first layer forms a channel of a thin film transistor, particularly a front channel of the thin film transistor. In embodiments, the first layer is deposited on a gate insulating layer of the thin film transistor. The gate insulating layer can include or consist of an insulating material.

[0036] At 486, the substrate is moved from the first vacuum chamber to a second vacuum chamber without breaking vacuum. Moving the substrate from the first vacuum chamber to the second vacuum chamber without breaking vacuum prevents atmospheric gases, particularly atmospheric oxygen, from interacting with the first layer, which may change the material properties of the first layer and / or affect the operation of the thin film transistors.

[0037] At 488, the method 480 includes depositing a second layer of the layer on the first layer by applying a bipolar pulsed DC voltage to at least one second electrode pair. The second material of the second layer includes a second metal oxide, and the second material is different from the first material of the first layer. In some embodiments, the second layer forms a back channel of the thin film transistor. In particular, the channel can be a double channel layer structure. In further embodiments, the second layer can form an intermediate channel layer of the thin film transistor. Forming the channel of the thin film transistor by depositing two or more layers of different materials, particularly by depositing the first and second layers according to embodiments, can increase the stability of the thin film transistor under stress.

[0038] According to some embodiments, one of the first material and the second material comprises a different metal than the other of the first material and the second material. In particular, one of the first metal oxide and the second metal oxide can comprise a different metal than the other of the first metal oxide and the second metal oxide. In embodiments, particularly embodiments of sputter deposition apparatuses, one of the first target material and the second target material comprises a different metal than the other of the first target material and the second target material.

[0039] In some embodiments, which can be combined with other embodiments, the first material or first metal oxide of the first target material includes elements in a first stoichiometry, and the second material or second metal oxide of the second target material includes elements in a second stoichiometry. The second stoichiometry can be different from the first stoichiometry. In particular, the elements can include at least two selected from the group consisting of indium, gallium, and zinc.

[0040] In embodiments, the first metal oxide comprises an element in a first oxidation state, and the second metal oxide comprises an element in a second oxidation state, the second oxidation state being different from the first oxidation state. For example, the first metal oxide and the second metal oxide may comprise at least one element selected from the group consisting of indium, gallium, zinc, tin, and aluminum, particularly the group consisting of indium, gallium, and zinc. The first oxidation state of at least one element in the first metal oxide may be different from the second oxidation state of at least one element in the second metal oxide.

[0041] According to embodiments, the first material or the first target material has a different carrier mobility relative to the second material or the second target material. In particular, the first metal oxide may have a different carrier mobility relative to the second metal oxide. As used herein, the term "carrier mobility" refers to the mobility of charge carriers in a material, such as a semiconductor material. In particular, carrier mobility refers to the mobility of holes and / or electrons. For example, one of the first material and the second material may have a high carrier mobility. The other of the first material and the second material may have a low or medium carrier mobility. A high carrier mobility is defined as a carrier mobility of 30 cm or more. 2 / Vs higher, especially 50cm 2 / Vs. Low carrier mobilities are below 10 cm 2 / Vs lower, especially 7cm 2 / Vs or 5cm 2 / Vs. The moderate carrier mobility can be a mobility in the range between high and low carrier mobility. In further embodiments, one of the first material and the second material can have high or moderate carrier mobility. The other of the first material and the second material can have low carrier mobility.

[0042] In exemplary embodiments of the sputter deposition apparatus, one of the first target material and the second target material can have high carrier mobility. The other of the first target material and the second target material can have low or medium carrier mobility. In further embodiments, one of the first target material and the second target material can have high or medium carrier mobility. The other of the first target material and the second target material can have low carrier mobility.

[0043] In some embodiments, the first material has a different carrier concentration than the second material. In particular, the first metal oxide may have a different carrier concentration than the second metal oxide. In embodiments, the first target material may have a different carrier concentration than the second target material. As used herein, the term "carrier concentration" refers to the concentration of charge carriers in a material, such as a semiconductor material. In particular, carrier concentration refers to the concentration of holes and / or the concentration of electrons.

[0044] In some embodiments, the first material can have a higher carrier mobility and / or a higher carrier concentration than the second material. In embodiments of a sputter deposition apparatus, the first target material can have a higher carrier mobility and / or a higher carrier concentration than the second target material.

[0045] In further embodiments, the first material can have a lower carrier mobility and / or a lower carrier concentration than the second material. In further embodiments of the sputter deposition apparatus, the first target material can have a lower carrier mobility and / or a lower carrier concentration than the second target material.

[0046] According to embodiments, at least one of the first metal oxide and the second metal oxide is indium gallium zinc oxide (IGZO), indium zinc tin oxide (IZTO), indium gallium zinc tin oxide (IGZTO), indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide (AZO). In some embodiments, the first metal oxide can be one of IGZO, IZTO, IGZTO, ITO, IZO, or AZO, and the second metal oxide can be a different one selected from the group consisting of IGZO, IZTO, IGZTO, ITO, IZO, or AZO. For example, one of the first metal oxide and the second metal oxide can be a transparent conductive oxide, in particular ITO, IZO, or AZO, and the other of the first metal oxide and the second metal oxide can be IGZO.

[0047] In some embodiments, the first metal oxide and the second metal oxide can comprise different compositions of one of IGZO, IZTO, IGZTO, ITO, IZO, or AZO. For example, one of the first metal oxide and the second metal oxide can comprise IGZO with a composition of 1:1:1 (indium:gallium:zinc), and the other of the first metal oxide and the second metal oxide can comprise IGZO with a different composition, such as 1:a:b (indium:gallium:zinc), where at least one of a and b is different from 1, e.g., greater than 1 or less than 1.

[0048] In exemplary embodiments, the first metal oxide can include indium, gallium, and zinc in a first oxidation state. The second metal oxide can include indium, gallium, and zinc in a second oxidation state, where the second oxidation state is higher or lower than the first oxidation state. In some embodiments, one of the first oxidation state and the second oxidation state can be fully oxidized. The combination of a first layer of a first material and a second layer of a second material, where the first and second materials have different carrier mobilities and / or different carrier concentrations, can advantageously expand the process window for thin film transistors with higher stability under stress and / or higher mobility.

[0049] In some embodiments, at least one of the first material and the second material, particularly one of the first material and the second material, particularly includes an additional metal oxide in addition to the first metal oxide and / or the second metal oxide. In embodiments, the additional metal oxide included in the first material can be different from the first metal oxide. The additional metal oxide included in the second material can be different from the second metal oxide. In some embodiments, the additional metal oxide can be included in one of the first material and the second material. In further embodiments, the first material and the second material can include the additional metal oxide. The first material and the second material can have different contents, e.g., mass fractions, of the additional metal oxide.

[0050] According to an embodiment, the further metal oxide may include aluminum oxide, particularly Al2O3, and / or tin oxide, particularly SnO2. Additionally or alternatively, the further metal oxide may include at least one transparent conductive oxide, particularly indium tin oxide (ITO), indium zinc oxide (IZO), and / or aluminum zinc oxide (AZO). In particular, the first metal oxide and / or the second metal oxide may be IGZO, IZTO, IGZTO, ITO, IZO, or AZO. By including a further metal oxide, such as a transparent conductive oxide, in the first material or the second material, at least one of the carrier concentration and carrier mobility of the respective material can be increased. In particular, the mobility of thin film transistors can be improved. According to an embodiment of the sputter-deposition apparatus, at least one of the first target material and the second target material, particularly one of the first target material and the second target material, includes a further metal oxide.

[0051] According to some embodiments, the first layer and the second layer can be deposited as a layer stack, particularly as a bilayer. In further embodiments, the first layer, the second layer, and the third layer can be deposited as a layer stack, particularly as a triple layer. In embodiments, the layer stack can form a layered channel of a thin film transistor.

[0052] According to embodiments, a process gas may be provided during deposition, and the process gas may include an inert gas such as argon, and / or a reactive gas such as oxygen, nitrogen, hydrogen, and ammonia, ozone, an activated gas, or the like.

[0053] According to some embodiments, the substrate moves continuously during deposition of the first layer and during deposition of the second layer ("dynamic coating"). Dynamic coating of the substrate, particularly dynamic deposition of the first and second layers, can provide uniform layer thicknesses, particularly without target imprint and / or process drift along the target lifetime. In further embodiments, the first and second layers can be deposited by static coating. The substrate can be placed in a coating region before deposition, and then a layer is deposited on the substrate. During deposition, the substrate remains in the coating region, and after deposition, the substrate is removed from the coating region. In particular, the vacuum chamber, e.g., the first vacuum chamber or the second vacuum chamber, can be sealed or closed from the environment or an adjacent vacuum chamber during deposition, for example, using a chamber valve.

[0054] According to an embodiment that can be combined with other embodiments described herein, the method may include moving the substrate to at least one additional vacuum chamber for depositing at least one additional layer, e.g., a third layer, on the substrate. The substrate may be moved without breaking vacuum. The at least one additional layer may be deposited using at least one additional electrode pair. In particular, a bipolar pulsed DC voltage may be supplied to the at least one additional electrode pair. The first layer, the second layer, and the at least one additional layer may form a layered channel, e.g., a multilayer channel, of a thin film transistor. The first layer may particularly form a front channel of the channel. In some embodiments, the at least one additional layer may include an additional channel layer. The additional channel layer may include an additional material. In particular, the additional material may have at least one of a different carrier mobility and a different carrier concentration from the second material.

[0055] For example, FIG. 5 shows an exemplary flow diagram of method 580 according to embodiments described herein. In particular, steps 582-588 of method 580 may correspond to steps 482-488 of method 480 in FIG. 4. At 590, method 580 includes moving the substrate from the second vacuum chamber to a third vacuum chamber without breaking vacuum. At 592, a third layer of layers is deposited on the second layer using at least one third electrode pair. A bipolar pulsed DC voltage may be supplied to the third electrode pair. The third material of the third layer may include a third metal oxide, and the third material may be different from the second material. The third material may have at least one of a different carrier mobility and a different carrier concentration relative to the second material. In embodiments, the third metal oxide may be IGZO, IZTO, IGZTO, ITO, IZO, or AZO. The third material may further comprise an additional metal oxide, such as tin oxide, aluminum oxide, and / or at least one transparent conductive oxide, such as ITO, IZO, and / or AZO.

[0056] According to the present disclosure, the term "substrate" as used herein encompasses both rigid substrates, such as glass substrates, wafers, slices of transparent crystals such as sapphire, or glass plates, and flexible substrates, such as webs or foils. According to some implementations, the embodiments described herein can be utilized for display PVD, i.e., sputter deposition onto large-area substrates for the display market. The deposition apparatus can be configured to deposit layers on at least one of semiconductor, metal, and glass substrates. In particular, the deposition apparatus can be configured to fabricate at least one of semiconductor devices and display devices.

[0057] According to some embodiments, the large area substrate or each substrate carrier (a substrate carrier can carry one substrate or multiple substrates) has a surface area of ​​at least 1 m 2 The size can be about 0.67m 2 (0.73m x 0.92m-GEN4.5) to approximately 8m 2, more specifically about 2 m 2 Approximately 9m from 2 , or up to 12m 2 The substrate or carrier provided in the structures, apparatus such as cathode assemblies, and methods according to the embodiments described herein can be a large area substrate as described herein. For example, the large area substrate or substrate carrier can be about 0.67 m 2 GEN4.5, which corresponds to a board (0.73m x 0.92m), approximately 1.4m 2 GEN5, which corresponds to a board (1.1m x 1.3m), approximately 4.29m 2 GEN7.5, which corresponds to a board (1.95m x 2.2m), approximately 5.7m 2 GEN8.5, which corresponds to a substrate (2.2m x 2.5m), or even approximately 8.7m 2 The generation 10 corresponds to a substrate (2.94 m x 3.37 m). Larger generations such as GEN11 and GEN12, and corresponding substrates, can be implemented as well.

[0058] According to some embodiments, which can be combined with other embodiments described herein, a substrate can be conveyed in a substantially vertical direction along the substrate transport track and / or during processing, particularly deposition. As used herein, "substantially vertical," particularly when referring to the orientation of a substrate, is understood to allow for a deviation from a vertical direction or orientation of ±20° or less, e.g., ±10° or less. This deviation can be provided, for example, because a substrate support that deviates somewhat from the vertical direction may result in a more stable substrate position. Nevertheless, for example, the orientation of a substrate during transport along the substrate transport track and / or during substrate processing is considered to be substantially vertical and different from a horizontal substrate orientation.

[0059] A bipolar pulsed DC voltage, as referred to herein, is a voltage having alternating polarity ("bipolar") applied to the electrodes of a pair of electrodes, such that a first electrode of the pair alternately functions as a cathode and an anode, and a second electrode of the pair alternately functions as an anode and a cathode.

[0060] Bipolar pulsed DC sputtering differs from conventional AC sputtering, such as MF sputtering or RF sputtering, in that the voltage waveform is not sinusoidal. Rather, the voltage waveform may be essentially constant in time (direct current, "DC"). For example, the waveform of a bipolar pulsed DC voltage may be a rectangular wave or a square wave. In particular, the positive portion of the waveform may be essentially constant in time and / or the negative portion of the waveform may be essentially constant in time, which may be particularly different from a sinusoidal voltage.

[0061] In some embodiments, each electrode of an electrode pair can alternately function as an anode and a cathode, and in particular, a separate electrode that continuously functions as an anode need not be provided.

[0062] In some embodiments, the frequency of the bipolar pulsed DC voltage may be at least 1 kHz, in particular at least 10 kHz or at least 30 kHz, and / or up to 100 kHz, in particular up to 80 kHz or up to 50 kHz.

[0063] In particular, sputtering with a bipolar pulsed DC voltage can enable improved arcing suppression, reduce process stability issues, and / or provide greater layer uniformity control, especially when compared to conventional DC sputtering. Furthermore, the square wave voltage in DC bipolar sputtering can enable reduced deposition rate losses, especially when compared to conventional AC sinusoidal sputtering methods.

[0064] In some embodiments, which may be combined with other embodiments described herein, the power supply arrangement may be configured to supply a positive voltage, in particular a positive DC voltage, and a negative voltage, in particular a negative DC voltage, to each electrode of an electrode pair, in particular to each electrode of at least one first electrode pair and at least one second electrode pair, and an electrode of an electrode pair may alternately function as a cathode and an anode, in particular with respect to the other electrode of the same pair of electrodes.

[0065] In some embodiments, each of the at least one first electrode pair and the at least one second electrode pair can be connected to a DC power supply of the power supply arrangement via a pulse unit. The number of pulse units and / or the number of DC power supplies can correspond to the number of electrode pairs. The pulse unit can be configured to convert a DC voltage provided by the DC power supply into a bipolar pulsed DC voltage.

[0066] At least one of the DC power sources, in particular each DC power source, may be configured to provide a power of at least 1 kW, in particular at least 10 kW, and / or up to 200 kW, in particular up to 100 kW. Alternatively or additionally, at least one of the power sources, in particular each DC power source, may be configured to provide a voltage of between 100 V and 1000 V. For example, at the output terminals of the pulse unit, the voltage amplitude may vary periodically between a first value of +500 V and a second value of −500 V.

[0067] The term "vacuum" as used in this disclosure may be understood as a space that is substantially free of matter, e.g., a space from which most or all of the air or gas has been removed, except for processing gases used in a deposition process, such as a sputter deposition process. By way of example, the term "vacuum" may be understood to mean a technical vacuum, e.g., a vacuum pressure of less than 10 mbar. One or more vacuum pumps, such as turbopumps and / or cryopumps, may be connected to the vacuum chambers, in particular the first vacuum chamber and / or the second vacuum chamber, to provide a vacuum within the vacuum chambers for substrate processing, such as layer deposition.

[0068] The embodiments described herein may provide the advantage of increasing at least one of the stability and mobility of thin film transistors. In particular, the process window for depositing layers for high-stability and high-mobility thin film transistors may be widened. More specifically, the stability of thin film transistors under bias stress and / or thermal stress may be increased. Furthermore, the transistor threshold voltage of thin film transistors may be controllable around 0 V. Embodiments may provide the deposition of thin film transistor layers with uniform and stable performance. In particular, deposition may be performed without target imprint, process drift, and / or arcing.

[0069] While the foregoing description is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the scope thereof, which scope is determined by the claims that follow.

Claims

1. 1. A method (480, 580) of depositing a layer of a thin film transistor on a substrate using a sputter deposition source including at least one first electrode pair and at least one second electrode pair, comprising: moving the substrate to a first vacuum chamber (482, 582); depositing a first one of the layers on the substrate by supplying a bipolar pulsed DC voltage to the at least one first electrode pair, wherein a first material of the first layer comprises a first metal oxide, and the first layer forms a front channel of the thin film transistor (484, 584); moving the substrate from the first vacuum chamber to a second vacuum chamber without breaking vacuum (486, 586); and depositing a second one of the layers on the first layer by applying a bipolar pulsed DC voltage to the at least one second electrode pair, wherein a second material of the second layer comprises a second metal oxide, the second material being different from the first material, and the second layer forms a back channel of the thin film transistor (488, 588). Including, Moving the substrate from the first vacuum chamber to the second vacuum chamber (486, 586) includes continuously moving the substrate from the first vacuum chamber to the second vacuum chamber through a slit opening in a chamber wall separating the first vacuum chamber and the second vacuum chamber from each other during deposition of the first layer and the second layer. method.

2. The method of claim 1 , wherein one of the first metal oxide and the second metal oxide comprises a different metal relative to the other of the first metal oxide and the second metal oxide.

3. 10. The method of claim 1, wherein the first metal oxide comprises elements in a first stoichiometry and the second metal oxide comprises the elements in a second stoichiometry, the second stoichiometry being different from the first stoichiometry.

4. The method of claim 3 , wherein the elements include at least two selected from the group consisting of indium, gallium, and zinc.

5. The method of claim 1 , wherein the first material has a different carrier mobility than the second material.

6. The method of claim 1 , wherein the first material has a different carrier concentration relative to the second material.

7. 2. The method of claim 1, wherein one of the first material and the second material further comprises an additional metal oxide, or the first material and the second material comprise different contents of an additional metal oxide, and the additional metal oxide comprises at least one of tin oxide, aluminum oxide, and a transparent conductive oxide.

8. 2. The method of claim 1, wherein one of the first material and the second material further comprises an additional metal oxide, or the first material and the second material comprise different contents of additional metal oxides, the additional metal oxides comprising tin oxide, aluminum oxide, and at least one of ITO, IZO, or AZO.

9. The method of claim 1 , wherein at least one of the first metal oxide and the second metal oxide is IGZO, IZTO, IGZTO, IZO, ITO, or AZO.

10. The method of claim 1 , wherein the first layer is deposited on a gate insulating layer.

11. The method comprises: moving the substrate from the second vacuum chamber to a third vacuum chamber without breaking vacuum (590); and depositing (592) a third one of the layers on the second layer; The method of claim 1 further comprising:

12. The method comprises: moving the substrate from the second vacuum chamber to a third vacuum chamber without breaking vacuum (590); and depositing (592) a third one of the layers onto the second layer using at least one third electrode pair; The method of claim 1 further comprising:

13. A sputter deposition apparatus (100) comprising: a first vacuum chamber (130) and a second vacuum chamber (140) arranged such that a substrate can be transferred between the first vacuum chamber (130) and the second vacuum chamber (140) through a slit opening provided in a chamber wall separating the first vacuum chamber (130) and the second vacuum chamber (140) from each other without breaking vacuum; and 1. A sputter deposition source comprising: at least one first electrode pair (132) and at least one second electrode pair (142), wherein the at least one first electrode pair (132) is disposed within the first vacuum chamber (130) and the at least one second electrode pair (142) is disposed within the second vacuum chamber (140); and a power supply arrangement (120) configured to supply a bipolar pulsed DC voltage to the at least one first electrode pair (132) and the at least one second electrode pair (142); a sputter deposition source comprising: Including, the at least one first electrode pair (132) includes a first target (134) having a first target material, the first target material including a first metal oxide, the first target material configured to deposit a first layer of a thin film transistor to form a front channel of the thin film transistor; and the at least one second electrode pair (142) includes a second target (144) having a second target material, the second target material including a second metal oxide and different from the first target material, the second target material configured to deposit a second layer of the thin film transistor to form a back channel of the thin film transistor; a sputter deposition apparatus (100) configured to continuously move the substrate from the first vacuum chamber to the second vacuum chamber through the slit opening in the chamber wall during deposition of the first layer and the second layer.

14. The sputter deposition apparatus (100) of claim 13, wherein the first target (134) and the second target (144) are rotating targets.

15. The sputter deposition apparatus (100) of claim 13, wherein the sputter deposition apparatus (100) is configured to perform the method of claim 1.

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