Pulsed plasma (DC / RF) deposition of high quality C films for patterning

Abstract

Embodiments of the present disclosure relate to methods for depositing an amorphous carbon layer onto a substrate using a plasma enhanced chemical vapor deposition (PECVD) process, including depositing over a previously formed layer on the substrate, specifically, the methods described herein utilize a combination of RF AC power and pulsed DC power to generate a plasma that deposits an amorphous carbon layer with a high ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon. The methods also provide lower processing pressures, lower processing temperatures, and higher processing powers, each of which, alone or in combination, can further increase the relative fraction of sp3 carbon in the deposited amorphous carbon layer. Due to the higher sp3 carbon fraction, the methods described herein provide an amorphous carbon layer with improved density, stiffness, etch selectivity, and film stress compared to amorphous carbon layers deposited by conventional methods.

Description

Background Art

[0001] field

[0002] Embodiments of the present disclosure relate to methods for depositing an amorphous carbon layer onto a substrate, including depositing over a previously formed layer on the substrate, using a plasma enhanced chemical vapor deposition (PECVD) process.

[0003] Description of related fields

[0004] Carbon hardmasks formed of amorphous carbon are used as etching molds in semiconductor device manufacturing to form high aspect ratio openings (e.g., having an aspect ratio of 2:1 or greater) in a substrate surface or in a material surface layer thereof. Typically, processing problems associated with forming high aspect ratio openings (including clogging, hole shape distortion, pattern deformation, top critical dimension blow up, line bending, and profile warping) are a result of undesirable material properties of conventionally deposited carbon hardmasks. For example, carbon hardmasks having one or both of lower material density and lower material stiffness (i.e., Young's modulus) are known to cause increased deformation of high aspect ratio openings compared to hardmask materials having higher density or higher stiffness (i.e., Young's modulus).

[0005] Similarly, compared to a hard mask exhibiting a higher etch selectivity, a reduced etch selectivity between the hard mask material and the substrate material can cause increased slit pattern deformation and line bending. Similar problems can be caused by higher film stress (compression or tension). In addition, as the critical dimension (CD) decreases and the size of the high aspect ratio opening increases, the thickness of the conventionally deposited carbon hard mask used to form the high aspect ratio opening also increases. Unfortunately, a hard mask with lower transparency due to one or both of the low optical K and the increased thickness can cause misalignment in subsequent lithography processes. In addition, processes with lower etch selectivity between the hard mask material and the underlying substrate material typically rely on relatively thick hard masks, which increases processing time and cost.

[0006] Therefore, there is a need in the art for improved hardmasks and methods of forming improved hardmasks. Summary of the invention

[0007] In one embodiment, a method of processing a substrate is provided. The method includes positioning a substrate on a substrate support disposed in a process volume of a process chamber. The method also includes flowing a process gas including a hydrocarbon gas and a dilution gas into the process volume. The method also includes maintaining the process volume at a pressure of less than about 100 mTorr. The method also includes forming a plasma of the process gas by applying a first power to a first electrode of the process chamber and applying a second power to a second electrode of the process chamber, wherein the second power is a pulsed DC power. The method also includes maintaining the substrate support at a temperature of less than about 350° C. The method also includes exposing a surface of the substrate to the plasma. The method also includes depositing an amorphous carbon layer on the surface of the substrate.

[0008] In another embodiment, a method of processing a substrate is provided. The method includes positioning a substrate on a substrate support disposed in a process volume of a process chamber. The method also includes flowing a process gas including a hydrocarbon gas and a diluent gas into the process volume. The method also includes maintaining the process volume at a pressure of less than about 20 mTorr. The method also includes forming a plasma of the process gas by applying RF AC power to a first electrode of the process chamber, wherein the RF AC power is between about 500 W and 5 kW, having a frequency between about 350 kHz and about 100 MHz, and applying pulsed DC power to a second electrode of the process chamber, wherein the pulsed DC power is between about 200 W and about 15 kW, pulsed at a frequency of about 1 kHz. The method also includes maintaining the substrate support at a temperature of less than about 100° C. The method also includes exposing a surface of the substrate to the plasma. The method also includes depositing an amorphous carbon layer on the surface of the substrate.

[0009] In another embodiment, a carbon hardmask is provided. The carbon hardmask includes an amorphous carbon layer disposed on a surface of a substrate. The amorphous carbon layer has a carbon content greater than about 1.8 g / cm 3 density, a Young's modulus greater than about 150 GPa, and a film stress less than about 500 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to be able to understand in detail the manner in which the above-mentioned features of the present disclosure are used, the present disclosure briefly summarized above may be described in more detail with reference to embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate typical embodiments of the present disclosure and are therefore not to be considered limiting of the scope, as the present disclosure may admit to other equally effective embodiments.

[0011] Figure 1 A schematic cross-sectional view of an exemplary processing chamber for practicing the methods described herein is shown according to one embodiment.

[0012] Figure 2 A flow chart of a method of depositing an amorphous carbon layer according to one embodiment is shown.

[0013] Figure 3 According to one embodiment, Figure 2 The amorphous carbon layer deposited by the method described in the present invention forms a carbon hard mask. DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure relate to methods for depositing an amorphous carbon layer onto a substrate, including depositing over a previously formed layer on the substrate, using a plasma enhanced chemical vapor deposition (PECVD) process. In particular, the methods described herein utilize a combination of RF AC power and pulsed DC power to generate a plasma that deposits an amorphous carbon layer at a high ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon. The methods also provide lower processing pressures, lower processing temperatures, and higher processing powers, each of which, individually or in combination, can further increase the relative fraction of sp3 carbon in the deposited amorphous carbon layer. Due to the higher sp3 carbon fraction, the methods described herein provide an amorphous carbon layer with improved density, stiffness, etch selectivity, and film stress compared to an amorphous carbon layer deposited by conventional methods.

[0015] Figure 1 is a schematic cross-sectional view of an exemplary processing chamber 100 for practicing the methods described herein according to one embodiment. Other exemplary processing chambers that can be used to practice the methods described herein include the RADION 100 available from Applied Materials, Inc. of Santa Clara, California. TM , and SYM3 TM processing equipment and suitable deposition chambers from other manufacturers.

[0016] The processing chamber 100 includes a lid assembly 101, a sidewall 102, and a chamber base 104. The lid assembly 101 includes a chamber lid 106, a showerhead 107 coupled to and in electrical communication with the chamber lid 106, and an electrically insulating ring 108 disposed between the chamber lid 106 and the sidewall 102. The showerhead 107, the sidewall 102, and the chamber base 104 together define a processing volume 105. In one embodiment, the chamber lid 106 and the showerhead 107 are formed of an electrically conductive material, such as aluminum. A gas inlet 109 is disposed through the chamber lid 106 and is fluidly coupled to a gas source 110. The showerhead 107 has a plurality of openings 111 disposed therethrough, the showerhead 107 being used to evenly distribute a processing gas from the gas source 110 into the processing volume 105. In other embodiments, the processing chamber 100 does not include a showerhead 107 , and the processing gas is delivered to the processing volume 105 via one or more gas inlets disposed through the chamber lid 106 or the sidewall 102 .

[0017] The processing volume 105 is fluidly coupled to a vacuum source 112, which may be one or more dedicated vacuum pumps, which maintains the processing volume 105 at subatmospheric pressure and evacuates process and other gases therefrom during processing, through a vacuum outlet 114. A substrate support 115 disposed in the processing volume 105 is disposed on a movable support shaft 116 extending through the chamber base 104. Herein, the processing chamber 100 is configured to facilitate transfer of a substrate 117 to and from the substrate support 115 through an opening 118 in one of the one or more sidewalls 102, which is sealed with a door or valve (not shown) during substrate processing.

[0018] The substrate 117 is maintained at a desired processing temperature using one or both of a heater 119 and one or more cooling channels 120. The heater 119 may be a resistive heater, and the one or more cooling channels are disposed in the substrate support 115. The one or more cooling channels 120 are fluidly coupled to a coolant source (not shown), such as a refrigerant source or a modified water source having a relatively high electrical resistance. The heater 119 is in electrical communication with a power source (not shown) configured to power the heater 119 and raise the temperature of the substrate support 115.

[0019] In some embodiments, one or more electrodes 124 are embedded in the dielectric material of the substrate support 115. One or more electrodes are electrically coupled to a power source 121. A power source 122 is electrically coupled to the showerhead 107. For embodiments that do not include a showerhead, the power source 122 is electrically coupled to the lid assembly 106. Each of the power sources 121 and 122 can be a continuous wave (CW) RF power source, a pulsed RF power source, a DC power source, and / or a pulsed DC power source. In one embodiment, the power source 121 is a CW RF power source and the power source 122 is a pulsed DC power source. In another embodiment, the power source 121 is a pulsed DC power source and the power source 122 is a pulsed RF power source. Although only two power sources 121 and 122 are shown, it is contemplated that more power sources may be coupled to electrodes in the substrate support 115 or the lid assembly 101, as desired. For example, a pulsed DC power source may be coupled to electrodes in both the substrate support 115 and the lid assembly 101, and an RF power source is coupled to electrodes in the lid assembly 101.

[0020] In one embodiment, the capacitively coupled plasma 123 is generated by forming and maintaining the plasma 123 in the processing volume 105 by providing RF power from the power source 122 to one or more electrodes in the lid assembly 101. The plasma 123 is then modified by providing DC power from the power source 121 to one or more electrodes disposed in the substrate support 115. In another embodiment, the plasma 123 is formed and maintained by RF power from the power source 121 and modified by DC power from the power source 122.

[0021] Figure 2 2 is a flow chart of a method 200 for depositing an amorphous carbon layer on a surface of a substrate according to one embodiment. At operation 201, the method 200 includes positioning a substrate on a substrate support. The substrate support is disposed in a processing chamber (such as a Figure 1 In operation 202, the method 200 includes flowing a process gas into the process volume. The process gas includes a carbon source gas, such as a hydrocarbon gas, for example, CH 4 , C 2 H 2 , C 3 H 8 , C 4 H 10 , C 2 H 4 , C 3 H 6 , C 4 H 8 , C 5 H 10or a combination thereof, and the process gas further comprises a diluent gas, for example, an inert gas such as Ar, He, Ne, Kr, Xe, or a combination thereof. In some embodiments, the diluent gas comprises an inert gas such as a noble gas, N 2 , H 2 or a combination thereof.

[0022] In some embodiments, the ratio of the flow rate of the hydrocarbon gas to the flow rate of the diluent gas is between about 1:10 and about 10:1, such as between about 1:5 and about 5:1. 2 H 2 The ratio of the flow rate of H to the flow rate of He is between about 1:3 and about 3:1. In some embodiments, the diluent gas includes H 2 , and H 2 The ratio of the flow rate of the gas to the flow rate of the hydrocarbon gas is between about 0.5:1 and about 1:10, such as between about 1:1 and about 1:5.

[0023] At operation 203, the method 200 includes maintaining the processing volume at a processing pressure between about 0.1 mTorr and about 100 mTorr, such as between about 0.1 mTorr and about 50 mTorr, or between about 0.1 mTorr and about 30 mTorr, or between about 0.1 mTorr and about 20 mTorr, or between about 0.1 mTorr and about 15 mTorr, or between about 0.1 mTorr and about 10 mTorr, or less than about 100 mTorr, or less than about 50 mTorr, or less than about 20 mTorr, or less than about 15 mTorr, or less than about 10 mTorr.

[0024] At operation 204, method 200 includes forming and maintaining a plasma of a process gas by applying a first power to a first electrode of a process chamber and applying a second power to a second electrode of the process chamber, wherein the second power is a pulsed DC power. In one embodiment, the first electrode is disposed in a substrate support. In another embodiment, the first electrode is disposed opposite the substrate support, such as in a showerhead or chamber lid of the process chamber. In one embodiment, the first power is an RF AC power between about 500 W and about 5 kW, such as about 2500 W. The first power has a frequency between about 350 kHz and about 100 MHz, such as 2 MHz or 13.56 MHz.

[0025] In one embodiment, the second electrode is disposed in the substrate support. In another embodiment, the second electrode is disposed opposite to the substrate support. In one embodiment, the second electrode is a showerhead. In one embodiment, the second power is between about 200 W and about 15 kW. In another embodiment, the second power is pulsed at a frequency of about 1 kHz. In another embodiment, the second power has a duty cycle of about 50%.

[0026] It is believed that providing pulsed DC power from the substrate support as described above results in greater uniformity of ion energy within the plasma, which in turn results in a higher sp3 carbon concentration in the deposited amorphous carbon layer. Figure 3 As described, an amorphous carbon layer having a higher sp3 concentration exhibits desirable properties, such as higher density, higher Young's modulus, and lower film stress, compared to conventionally deposited amorphous carbon layers. It is further believed that providing pulsed DC power to, for example, a second electrode (such as a showerhead) opposite to the substrate support as described above causes increased secondary electron emission from the second electrode, which can further reduce the film stress of the deposited amorphous carbon layer.

[0027] At operation 205, method 200 includes maintaining a temperature at which the substrate support, and thus a substrate disposed thereon, is between about -50°C and about 350°C, such as between about -50°C and about 150°C, between about -50°C and about 100°C, between about -50°C and about 50°C, between about -25°C and about 25°C, or less than about 350°C, such as less than about 200°C, less than about 150°C, less than 100°C, or less than about 50°C.

[0028] At operation 206, the method 200 includes exposing the surface of the substrate to a plasma. At operation 207, the method 200 includes depositing an amorphous carbon layer on the surface of the substrate.

[0029] although Figure 2 One example of a flow chart is shown, but it should be noted that variations of method 200 are contemplated. For example, it is contemplated that operation 205 may occur before operations 202, 203, or 204. Additionally, it is contemplated that one or more of operations 202-207 may occur simultaneously.

[0030] Figure 3 According to one embodiment, Figure 2303 deposited by the method described in . The carbon hard mask 303, shown as a patterned carbon hard mask, includes an amorphous carbon layer 302 having a plurality of openings 304 formed therein, disposed on a surface to be patterned of a substrate 301. The substrate 301 or one or more material layers thereof is formed of one or a combination of crystalline silicon, silicon oxide, silicon oxynitride, silicon nitride, strained silicon, silicon germanium, tungsten, titanium nitride, doped or undoped polysilicon, carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire, and low-k dielectric materials.

[0031] The amorphous carbon layer 302 has a To date Between (such as between To date Between or about To date The thickness is greater than about 1.8 g / cm 3 and a Young's modulus greater than about 150 GPa. In one embodiment, the amorphous carbon layer 302 has a tensile or compressive film stress of less than about 500 MPa. In some embodiments, each of the openings 304 has an aspect ratio (i.e., a ratio of height 306 to width 305) greater than about 2:1, such as greater than about 3:1, greater than about 4:1, greater than about 5:1, greater than about 6:1, greater than about 7:1, greater than about 8:1, greater than about 9:1, or greater than about 10:1.

[0032] The methods described herein and the amorphous carbon layers deposited according to such methods exhibit desirable properties for carbon hard mold applications. The deposited amorphous carbon layers exhibit a high ratio of sp3 (diamond-like) carbon to sp2 (graphite-like) carbon. The methods also provide lower processing pressures, lower processing temperatures, and higher processing powers, each of which, individually or in combination, can further increase the relative fraction of sp3 carbon in the deposited amorphous carbon layer. Due to the higher sp3 carbon fraction, the methods described herein provide an amorphous carbon layer with improved density, stiffness, etch selectivity, and film stress compared to amorphous carbon layers deposited by conventional methods.

[0033] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the same is determined by the claims that follow.

Claims

1. A method for processing a substrate, include: positioning the substrate on a substrate support disposed in a process volume of a process chamber; flowing a process gas comprising a hydrocarbon gas and a diluent gas into the process volume; maintaining the process volume at a pressure of less than 100 mTorr; forming a plasma of the process gas by applying a first power to a first electrode of the process chamber and applying a second power to a second electrode of the process chamber, wherein the first power is RF AC power and the second power is a first pulsed DC power; maintaining the substrate support at a temperature of less than 200° C.; exposing a surface of the substrate to the plasma; as well as An amorphous carbon layer is deposited on the surface of the substrate.

2. The method of claim 1, wherein the amorphous carbon layer has a carbon content greater than 1.8 g / cm 3 and has a Young's modulus greater than 150 GPa. The method of claim 1 , wherein the amorphous carbon layer has a film stress less than 500 MPa.

4. The method of claim 1, wherein the hydrocarbon gas comprises CH 4 , C 2 H 2 , C 3 H 8 , C 4 H 10 , C 2 H 4 , C 3 H 6 , C 4 H 8 , C 5 H 10 Or one of the combinations thereof, and wherein the flow rate ratio of the hydrocarbon gas to the dilution gas is between 1:10 and 10:

1.

5. The method of claim 4, wherein the temperature is less than 100°C and the pressure is less than 20 mTorr.

6. The method of claim 5, wherein the diluent gas comprises H 2 , and where H 2 The flow rate ratio to the hydrocarbon gas is between 0.5:1 and 1:

10.

7. The method of claim 1, wherein the first power is between 500 W and 5 kW with a frequency between 350 kHz and 100 MHz, and wherein the second power is between 200 W and 15 kW and is pulsed at a frequency of 1 kHz.

8. The method of claim 1, wherein the first electrode is disposed in the substrate support, and the second electrode is disposed opposite the substrate support, and wherein the second electrode is a showerhead.

9. The method of claim 1, wherein the second electrode is disposed in the substrate support, and the first electrode is disposed opposite the substrate support.

10. The method according to claim 9, in: The lid assembly of the process chamber includes a third electrode; and The method further comprises: A third power is applied to the third electrode, wherein the third power is a second pulsed DC power.

11. A method for processing a substrate, include: positioning the substrate on a substrate support disposed in a process volume of a process chamber; flowing a process gas comprising a hydrocarbon gas and a diluent gas into the process volume; maintaining the process volume at a pressure of less than 20 mTorr; forming a plasma of the process gas by applying RF AC power to a first electrode of the process chamber and applying a first pulsed DC power to a second electrode of the process chamber, wherein the RF AC power is between 500 W and 5 kW with a frequency between 350 kHz and 100 MHz, and wherein the first pulsed DC power is between 200 W and 15 kW; maintaining the substrate support at a temperature of less than 100° C.; exposing a surface of the substrate to the plasma; as well as An amorphous carbon layer is deposited on the surface of the substrate.

12. The method of claim 11, wherein the hydrocarbon gas comprises CH 4 , C 2 H 2 , C 3 H 8 , C 4 H 10 , C 2 H 4 , C 3 H 6 , C 4 H 8 , C 5 H 10 or a combination thereof.

13. The method of claim 12, wherein the diluent gas comprises H 2 , and where H 2 The flow rate ratio to the hydrocarbon gas is between 0.5:1 and 1:

10.

14. The method of claim 11, wherein the second electrode is disposed in the substrate support, and the first electrode is disposed opposite the substrate support.

15. The method according to claim 14, in: The lid assembly of the process chamber includes a third electrode; and The method further comprises: A third power is applied to the third electrode, wherein the third power is a second pulsed DC power.

16. A method for manufacturing a carbon hardmask on a surface of a substrate, the carbon hardmask comprising an amorphous carbon layer, the method include: positioning the substrate on a substrate support disposed in a process volume of a process chamber; flowing a process gas comprising a hydrocarbon gas and a diluent gas into the process volume; maintaining the process volume at a pressure of less than 100 mTorr; forming a plasma of the process gas by applying a first power to a first electrode of the process chamber and a second power to a second electrode of the process chamber, wherein the first power is RF AC power and the second power is pulsed DC power; maintaining the substrate support at a temperature of less than 200° C.; exposing a surface of the substrate to the plasma; as well as depositing the amorphous carbon layer on the surface of the substrate, The amorphous carbon layer has a carbon content greater than 1.8 g / cm 3 density, Young's modulus greater than 150 GPa and membrane stress less than 500 MPa. 17 . The method of claim 16 , wherein the amorphous carbon layer has a plurality of openings formed therethrough, and wherein each of the plurality of openings has an aspect ratio greater than 2:1.

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