Patent Application
20140319488
1. Field of Art
The present disclosure relates to depositing a layer of material on a structure for encapsulation or blanket deposition using radical assisted atomic layer deposition (RA-ALD) to protect the structure against environment.
2. Description of the Related Art
An atomic layer deposition (ALD) is a thin film deposition technique for depositing one or more layers of material on a substrate. ALD uses two types of chemical, one is a source precursor and the other is a reactant precursor. Generally, ALD includes four stages: (i) injection of a source precursor, (ii) removal of a physical adsorption layer of the source precursor, (iii) injection of a reactant precursor, and (iv) removal of a physical adsorption layer of the reactant precursor.
ALD can be a slow process that can take an extended amount of time or many repetitions before a layer of desired thickness can be obtained. Hence, to expedite the process, a vapor deposition reactor with a unit module (so-called a linear injector), as described in U.S. Patent Application Publication No. 2009/0165715 or other similar devices may be used to expedite ALD process. The unit module includes an injection unit and an exhaust unit for a source material (a source module), and an injection unit and an exhaust unit for a reactant (a reactant module).
It is advantageous to encapsulate display devices such as organic light-emitting diode (OLED) devices by a blanket deposition layer to prevent moisture or oxygen from causing damage during their use. Such blanket deposition layer may be formed using various materials including polymeric films, oxides (e.g., SiO2 and Al2O3) and nitrides (e.g., SiNx). More than one layer of materials may be formed on the display devices to increase the effectiveness of the encapsulation. A commonly used measure of encapsulation is water vapor transmission rate (WVTR). WVTR is the steady state rate at which water vapor permeates through a film at specified conditions of temperature and relative humidity. A lower WVTR of a blanket deposition layer indicates that the blanket deposition layer is more effective in preventing penetration of moisture.
In other applications, a blanket layer of low temperature oxide material may be deposited over a patterned structure of photoresist layer by an atomic layer deposition (ALD) technique to modify the pitch between the patterns. Generally, photoresist materials are not tolerant to ozone or radicals generated from ozone at high temperature. Therefore, ozone or radicals generated from ozone was not frequently used in the process of forming spacers.
Embodiments related to deposing a barrier layer over a structure on a substrate by a barrier layer before depositing a blanket deposition layer using radicals generated from ozone. To deposit the barrier layer over the structure, source precursor is injected onto the structure and the substrate. First radicals are generated from first gas containing nitrogen compound. The generated first radicals are then injected onto the structure and the substrate to form the barrier layer by an atomic layer deposition (ALD) process. Second radicals are generated from second gas containing more ozone than the first gas. The second radicals are injected onto the structure and the substrate to form a blanket deposition layer over the barrier layer by an ALD process.
In some embodiments, the processes of depositing the barrier layer are repeated for a predetermined number of times. Further, the processes of depositing the blanket deposition layer are also repeated for a predetermined number of times.
In some embodiments, the source precursor is also injected onto the structure and the substrate after injecting the first radicals and before injecting the second radicals.
In some embodiments, the structure comprises organic light-emitting diode (OLED).
In some embodiments, the nitrogen compound comprises nitrous oxide.
In some embodiments, the nitrogen compound comprises at least one of N2O and NH3.
In some embodiments, the source precursor includes at least one of trimethylaluminum (TMA), tris[dimethylamino]Silane (3DMAS), hexamethyldisilazane (HMDS), Di[isopropylamino]silane (DiPAS), and Tetrakis[dimethylamino]titanium (TDMAT).
In some embodiments, the barrier layer comprises at least one of Al2O3, AlN, and SiO2.
In some embodiments, the barrier layer has a thickness of 1 to 100 Å.
In some embodiments, the blanket deposition layer includes at least one of Al2O3SiO2, ZrO2, TiO2, and HfO2.
In some embodiments, the barrier layer has a thickness of 1 to 100 Å.
In some embodiments, the blanket deposition layer has a thickness of 100 to 1000 Å.
In some embodiments, the blanket deposition layer has a thickness of 100 to 500 Å.
In some embodiments, the first and second radicals are generated by remote-plasma generation.
In some embodiments, the structure comprises a photoresist array or elongated photoresist mandrels.
In some embodiments, a conformal blanket deposition layer is form on the photoresist mandrels to perform pitch doubling. The conformal blanket deposition layer comprises SiO2 deposited at low temperature below 100° C.
Embodiments also relate to an organic light-emitting diode (OLED) device including a blanket deposition layer and a barrier layer to prevent damage to the device during a process of forming the blanket deposition layer. The OLED device includes a substrate, a first electrode formed on the substrate, a second electrode and an organic material sandwiched between the first electrode and the second electrode. The barrier layer is formed on the second electrode and the substrate by exposure to a first source precursor and first radicals generated from first gas containing nitrogen compound. The blanket deposition layer is formed on the barrier layer by exposure to a second source precursor and second radicals generated from second gas containing more ozone than the first gas.
In some embodiments, the first and second source precursors are the same type of gas.
Embodiments are described herein with reference to the accompanying drawings. Principles disclosed herein may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the features of the embodiments.
In the drawings, like reference numerals in the drawings denote like elements. The shape, size and regions, and the like, of the drawing may be exaggerated for clarity.
Embodiments relate to forming a barrier layer on a structure before performing radical-assisted atomic layer deposition (RA-ALD) using ozone to form oxygen radicals that function as a reactant precursor for depositing a blanket deposition layer over the structure. Before exposing the substrate to ozone or oxygen radicals generated from ozone or oxygen radicals with hydroxyl radicals (generated from ozone mixed with hydrogen-containing gas such as hydrogen or ammonia), the barrier layer is formed on the substrate by exposing the structure formed on a substrate to radicals of nitrogen compound gas to prevent ozone, its radicals or oxygen radicals in combination with hydroxyl radicals from penetrating and damaging the device during the process of depositing the blanket deposition layer. In this way, the highly reactive ozone molecules, oxygen radicals or oxygen radicals with hydroxyl radicals can be used to form the blanket deposition layer while preventing damages to the device formed on the substrate.
The structure described herein refers to configuration of material formed on a substrate. The structure may be a flat layer of material or patterned layer of material formed on the substrate.
The process chamber enclosed by the walls may be maintained in a vacuum state to prevent contaminants from affecting the deposition process. The process chamber 110 contains a susceptor 128 which receives a substrate 120. The susceptor 128 is placed on a support plate 124 for a sliding movement. The support plate 124 may include a temperature controller (e.g., a heater or a cooler) to control the temperature of the substrate 120. The linear deposition device 100 may also include lift pins (not shown) that facilitate loading of the substrate 120 onto the susceptor 128 or dismounting of the substrate 120 from the susceptor 128.
In one embodiment, the susceptor 128 is secured to brackets 210 that move across an extended bar 138 with screws formed thereon. The brackets 210 have corresponding screws formed in their holes receiving the extended bar 138. The extended bar 138 is secured to a spindle of a motor 114, and hence, the extended bar 138 rotates as the spindle of the motor 114 rotates. The rotation of the extended bar 138 causes the brackets 210 (and therefore the susceptor 128) to make a linear movement on the support plate 124. By controlling the speed and rotation direction of the motor 114, the speed and the direction of the linear movement of the susceptor 128 can be controlled. The use of a motor 114 and the extended bar 138 is merely an example of a mechanism for moving the susceptor 128. Various other ways of moving the susceptor 128 (e.g., use of gears and pinion at the bottom, top or side of the susceptor 128). Moreover, instead of moving the susceptor 128, the susceptor 128 may remain stationary and the reactors 136 may be moved.
One or more of the reactors 320A, 320B, 334A, 334B, 364A, 364A, 368B, 368B are connected to gas pipes (not shown) to provide source precursor, reactor precursor, purge gas and/or other materials. The materials provided by the gas pipes may be (i) injected onto the substrate 314 directly by the reactors 320A, 320B, 334A, 334B, 364A, 364B, 368A, 368B, (ii) after mixing in a chamber inside the reactors 320A, 320B, 334A, 334B, 364A, 364B, 368A, 368B, or (iii) after conversion into radicals by plasma generated within the reactors 320A, 320B, 334A, 334B, 364A, 364B, 368A, 368B. After the materials are injected onto the substrate 314, the redundant materials may be exhausted through outlets 330, 338. The interior of the rotating deposition device 300 may also be maintained in a vacuum state.
By applying a voltage difference between the inner electrode 518 and the outer electrode 512, plasma is generated in the plasma chamber 514. As a result of the plasma, radicals of the gas or the mixture of gases are generated within the plasma chamber 514. The generated radicals are injected into the reaction chamber 414 via the injector slit 522. The region of the substrate 120 below the reaction chamber 530 comes into contact with the radicals, depositing a layer of material on the substrate 420 by an RA-ALD process. Because the radicals are generated in the plasma chamber 514 that is located away from the substrate 420, the process performed by the radical reactor 136B is referred to as a remote-plasma generation.
The distance between the plasma chamber 514 and the substrate 420 is configured so that a sufficient amount of radicals reach the substrate 420 in an active state. Radicals have a predetermined lifetime. Hence, as the radicals travel via the injector slit 522 and the reaction chamber 530 to the substrate 420, some of the radicals revert back to an inactive gaseous state. With the increase in the travel distance, the amount of radicals reverting to the inactive gaseous state increases. Hence, it is advantageous to set the distance between the plasma chamber 514 and the substrate 420 to be less than a certain length. For example, the distance between the plasma chamber 514 and the substrate 420 is set to 10 to 100 mm.
When using radicals of nitrogen, and nitrogen containing gas mixtures (e.g., N2O and NH3 mixture), the lifespan of the radicals such as N* or H* radicals is relatively short (often shorter than 1 msec), and most of the radicals revert back to an inactive state if the distance H is 80 mm or more. Hence, the distance H is set to be less than 80 mm when using radicals of nitrogen containing gas mixtures.
The layers 620 may become damaged if exposed to ozone, ozone radicals or moisture that penetrates through the cathode 624. Damage to the layers 620 may cause the OLED device 600 to become inoperable. Hence, a blanket deposition layer may be formed over the cathode 624 and/or the layers 620 to prevent penetration of oxygen or moisture after the OLED device 600 is fabricated. Although various chemical or radicals may be used to form a blanket deposition layer, the use of ozone, its radicals or its radicals in combination with hydroxyl radicals as a reactant precursor in an RA-ALD process generally results in a blanket deposition layer with superior characteristics. Materials of blanket deposition layer that may be formed by RA-ALD process using ozone or radicals generated from ozone include, for example, oxides such as SiO2, Al2O3, ZrO2, TiO2, and HfO2.
The high quality of oxide films generated by using ozone or its radicals is partly due to high reactivity of ozone. The high reactivity of ozone contributes to an increased amount of radicals to be generated in the radical reactors compared to oxygen. Moreover, the oxide layer formed by using O* radicals from ozone plasma tend to have lower stress with higher growth rate than those of an oxide layer formed by using O* radicals from oxygen plasma. Hence, the use of ozone to generate O* radicals is advantageous in forming a thinner and denser blanket deposition layer, especially adapted for use in flexible OLEDs.
However, the use of ozone as a source of O* radicals also accompany the risk of damaging devices formed on the substrate by ozone molecules (not activated into O* radicals) that may penetrate into the devices or decompose structures in the devices. Compounds used in forming OLED devices or photoresists are especially vulnerable to damage by ozone. Hence, ozone and its radicals have generally not been used in the process of fabricating OLED devices or oxide layers on the photoresist layer.
Embodiments enable the use of ozone, its radicals or its radicals in combination with hydroxyl radicals by forming a barrier layer on structures of devices before exposing the substrate or the structures of the devices to ozone, its radicals or hydroxyl radicals. The barrier layer may be made of the same or similar material as the blanket deposition layer, but the process for forming the barrier layer preferably uses less of ozone, its radicals or hydroxyl radicals, or uses no ozone, its radicals or hydroxyl radicals at all. Advantageously, the thickness of the barrier layer may be set to be thicker than the diffusion distance of ozone or hydroxyl radical at a given temperature for performing the deposition process so that the ozone or hydroxyl radical can be prevented from coming into contact with the layers 620.
In one embodiment, the barrier layer 720 is formed by exposing the OLED device to a source precursor and then using less-reactive radials generated from plasma other than ozone as a reactant precursor. For example, TMA may be used as a source precursor that is injected by the injector 136A for adsorption on the OLED device, and then N2O gas may be used to generate radicals by the radical reactor 136B to provide a reactant precursor. The radicals are generated by applying a voltage difference in the radical reactor 136B. The radicals replace or react with the source precursor (e.g., TMA) and form a layer of Al2O3 on the OLED device by RA-ALD process.
After forming the barrier layer 720, the substrate 630 is exposed to a source precursor and then a reactant precursor to form a blanket deposition layer 730. The source precursor used in this process may be the same material used for forming the barrier layer 720 or it may be a different material. In one embodiment, the thickness of barrier layer 720 is at least 1 Å to prevent diffusion of ozone into the device but not more than 100 Å so that the OLED may retain flexibility. In order to deposit the barrier layer 720 of sufficient thickness, the process of injecting the source precursor and injecting the radicals may be repeated for a number of times.
In one embodiment, TMA is used as the source precursor for forming the blanket deposition layer 730. The reactant precursor used in the process of forming the blanket deposition layer 730 is different from the reactant precursor used in the process of forming the barrier layer 720. That is, the reactant precursor used in the process of forming the blanket deposition layer 730 includes ozone or radicals generated from ozone. The radicals can be generated, for example, by using the radical reactor 136B. It is to be noted that the barrier layer 720 previously formed on the cathode 624 prevents the ozone from damaging the layers 620 during the process of depositing the blanket deposition layer 730. Two different radical reactors may be used: one for forming the barrier layer 720 and the other for forming the blanket deposition layer 730.
The blanket barrier layer 738 may be deposited to have a height between 0.1 nm and 10 nm thick, more preferably between 1 nm and about 5 nm thick on the photoresist mandrels 722. The blanket barrier layer 738 may be deposited at a temperature below 100° C., preferably in a temperature range of room temperature to 50° C., because photoresist materials are not tolerant to high temperatures.
The blanket barrier SiO2 layer 738 may be formed by first exposing the mandrels 722 to a source precursor and then to radicals functioning as a reactant precursor. The source precursor may be, for example, 3DMAS (Tris(DiMethylAmino)Silane: SiH[N(CH3)2]3, hexamethyldisilazane (HMDS) or DiPAS ((Di-isopropylamino)silane: SiH3(N(C3H7)2)). The radicals may be generated by N2O or N2O mixed with NH3 remote plasma.
After forming the blanket barrier SiO2 layer, the conformal blanket SiO2 spacer layer 734 is formed. The conformal blanket SiO2 spacer layer 734 preferably has a thickness between 10 nm to 50 nm, and more preferably between 15 nm and 30 nm. The conformal blanket SiO2 spacer layer 734 may be formed over the barrier layer 738 by exposing the source precursor and then to O* radicals generated from ozone plasma or O* radicals with hydroxyl radicals generated from ozone plasma mixed with hydrogen. While ozone, hydrogen, O* radicals, hydroxyl radicals or combinations thereof are being injected, the mandrels 722 are protected from ozone or O* radicals by the blanket barrier SiO2 layer.
After forming the conformal blanket SiO2 spacer layer, anisotropical etching is performed on the blanket barrier SiO2 layers from exposed horizontal surfaces in the device to retain the blanket barrier SiO2 layers on vertical sidewalls of the photoresist mandrels 722 to form so-called oxide spacers composed of the sidewalls 744 and 748 as shown in
The rotating deposition apparatus 800 may include injector 812 for injecting a source precursor (e.g., TMA or 3DMAS), a first radical reactor 814, and a second radical reactor 816. The first radical reactor 814 may generate radicals using gas other than ozone (e.g., N2O) while the second radical reactor 816 may generate radicals using ozone or ozone in combination mixed with hydrogen. When forming the barrier layer 720, the second radical reactor 816 may be inactivated while the first radical reactor 814 injects radicals onto the substrate. When forming the blanket deposition layer 730, the first radical reactor 814 may be inactivated while the second radical reactor 816 injects radicals onto the substrate. The growth rate of a deposition layer using the RA-ALD process is higher when ozone plasma is used compared to using N2O plasma. Further, the growth rate of the deposition layer using RA-ALD process is higher when radicals are generated from the mixture of ozone and hydrogen gases compared to using ozone alone.
The arrangements of the rotating deposition apparatuses 800, 900 are merely illustrative. Various other gases may be used as source precursor and different numbers of injectors and radical reactors may be used to deposit a barrier layer and a blanket deposition layer.
First, source precursor (e.g., TMA) is injected 1010 onto the substrate 630 and the layers 620. The radical reactor 136B is provided with first gas composed mostly of nitrogen compound (e.g., N2O) and a smaller amount of ozone to generate 1014 radicals. For example, the gas may include at most 10% of ozone and at least 90% of N2O. Alternatively, the first gas may include only nitrogen compound and no ozone. The generated radicals are injected 1018 onto the substrate as reactant precursor to form a barrier layer 720 on the substrate and the structure. It is then determined 1020 if the thickness of the barrier layer 720 is sufficient. If not, then the process returns to injecting 1010 the source precursor and repeats the subsequent steps. The RA-ALD process of injecting TMA by the injector 136A and injecting radicals of the gas composition by the radical reactor 136B may be repeated to form a barrier layer 720 of thickness 1 Å to 100 Å on the substrate 630. The RA-ALD process for depositing the barrier layer 720 does not cause damages to the layers 620 due to low content or absence of ozone. If it is determined that the thickness of the barrier layer 720 is sufficient, then the process proceeds to the process of forming a blanket deposition layer.
Then source precursor may be injected 1022 onto the substrate 630 and the layers 620 to deposit a blanket deposition layer 730. In some embodiments, the source precursor is not separately injected onto the substrate. Rather, the source precursor previously injected 1010 onto the substrate is used for depositing the blanket deposition layer 730.
Then, the radical reactor 136B is provided with second gas including more ozone compared to first gas to generate 1026 radicals. The radicals generated from the second gas is injected 1028 onto the substrate, causing the blanket deposition layer 730 to be formed on the substrate 630 by RA-ALD process. It is then determined 1030 if the blanket deposition layer 730 is of a sufficient thickness. If not, the process returns to injecting 1022 the source precursor and repeats the subsequent processes. If the thickness of the blanket deposition layer is sufficient, the process terminates.
After sufficient thickness of barrier layer 720 is formed, the portion of ozone in the gas composition is increased to deposit the blanket deposition layer 730. For example, composition gas including 10% of N2O and 90% of ozone, or 10% to 50% of hydrogen and 50% to 90% of ozone for reactive O* radicals and hydroxyl radical generations may be used to deposit the blanket deposition layer 730 during this stage. Instead of using mixed gas of N2O and ozone to generate radicals, mixed gas including 10% to 50% of hydrogen and ozone can be used to generate O* radicals and hydroxyl radicals for depositing the blanket deposition layer 730. The thickness of the blanket deposition layer 730 may be 100 to 1000 Å.
In one embodiment, a layer of AlN is formed as the barrier layer 720 followed by formation of a layer of Al2O3 as the blanket deposition layer 730. To form the barrier layer 720 and the blanket deposition layer 730, the injector 136A injects TMA as source precursor onto the OLED device. Then NH3 is provided to the radical reactor 136B to generate N* radicals. N* radicals react with or replace TMA molecules adsorbed on the OLED device to form AlN layer.
The RA-ALD process of depositing AlN may be repeated to deposit an AlN layer of 1 to 100 Å thickness. After depositing the AlN layer as the barrier layer 720, Al2O3 is deposited as the blanket deposition layer 730 on the AlN layer by injecting TMA as the source precursor and radicals of ozone or radicals of ozone and hydroxyl as the radical precursor. The thickness of the deposited Al2O3 layer may be 100 to 1000 Å.
In one embodiment, a layer of SiO2 is deposited as the barrier layer 720 followed by formation of a layer of Al2O3 as the blanket deposition layer 730. To form the barrier layer 720, Tris[dimethylamino]Silane (3DMAS) vapor is injected by the injector 136A on the substrate 630 and the cathode 624 as a source precursor. Hexamethyldisilazane (HMDS) or DiPAS may be used as a source precursor instead of 3DMAS.
Then N2O is provided to the radical reactor 136B to generate O* radicals. O* radicals functions as a reactant precursor that reacts with or replaces 3DMAS molecules adsorbed on the OLED device to form a SiO2 layer. The RA-ALD process may be repeated to deposit a SiO2 layer of 1 to 100 Å thickness.
After depositing the SiO2 layer as the barrier layer 720, Al2O3 is deposited as the blanket deposition layer 730 on the SiO2 layer by injecting TMA as the source precursor and O* radicals as the radical precursor. The thickness of the deposited Al2O3 layer may be 100 to 1000 Å. Alternatively, the blanket deposition layer 730 may include SiO2 formed by using O* radicals derived from ozone as the reactant precursor.
In one embodiment, a layer of Al2O3 is deposited as the barrier layer 720 followed by formation of a layer of TiO2 as an optical function layer to control the transmittance of the incident light at a given wavelength. To form the barrier layer 720, TMA vapor is injected as a source precursor. After depositing the Al2O3 layer as the barrier layer 720, TiO2 is deposited as the optical function layer having a refractive index larger than 2.0 at the visible wavelength on the Al2O3 layer by injecting Tetrakis[dimethylamino]-titanium (TDMAT) as the source precursor and the O* radicals and reactive species from ozone plasma as the reactant precursor. The thickness of the Al2O3 barrier layer 720 may be 1 to 100 Å, and the TiO2 optical function layer 730 may be 100 to 1000 Å.
In one embodiment, the composition of gas for generating radicals as the reactant precursor is gradually changed. For example, the composition of gas injected into radical reactor 136B may change gradually from N2O to O3. In other embodiments, the composition of gas may change abruptly from one type of gas (e.g., N2O) for depositing a barrier layer to another type of gas (e.g., O3) for depositing a blanket deposition layer.
Although above examples are described primarily with reference to ozone and its radicals, the same principle can also be applied to hydroxyl radicals that are also very reactive and can damage structures during the process of RA-ALD process.
By providing a barrier layer on an a structure or device sensitive to environment before exposing the structure or the device to ozone and radicals generated from ozone, damage to the structure or the device by penetration of ozone into the structure or the device can be prevented during the process of depositing a blanket layer using the ozone or O* radicals generated from the ozone. Therefore, the integrity of the structure or the device is maintained during a fabrication process while providing the blanket layer of a superior quality to protect the structure or the device from moisture or oxygen after the structure or the device is fabricated.
Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.
This application claims priority under 35 U.S.C. §119(e) to co-pending U.S. Provisional Patent Application No. 61/815,980 filed on Apr. 25, 2013, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61815980 | Apr 2013 | US |
