Patent Application
20100327413
The present invention relates to etching an etch layer through a mask during the production of a semiconductor device. More specifically, the present invention relates to etching high aspect ratio features through a hardmask during the production of semiconductor devices.
During semiconductor wafer processing, features of the semiconductor device are defined by a patterned mask.
To provide increased density, feature size is reduced. This may be achieved by reducing the critical dimension (CD) of the features, which requires improved resolution.
In forming high aspect ratio features in an etch layer, a hardmask layer may be formed over the etch layer with a mask over the hardmask layer. In addition, Multi-Layer Resist has been widely used in the fabrication process of the high performance ULSI devices. Multi-Layer Resist typically includes a patterning resist layer, a spin-on-glass (SOG) interlayer, and a bottom resist layer. The patterning resist layer may be a photoresist. The bottom resist layer may be a sputtered carbon film, or spun-on carbon film.
To achieve the foregoing and in accordance with the purpose of the present invention, a method for etching an etch layer over a substrate and disposed below a hardmask layer disposed below a mask is provided. The substrate is placed in a plasma processing chamber. The hardmask layer is opened by flowing a hardmask opening gas with a COS or CS2 component into the plasma chamber, forming a plasma from the hardmask opening gas, and stopping the flow of the hardmask opening gas. Features are etched into the etch layer through the hardmask. The hardmask is removed.
In another manifestation of the invention, a method for etching an etch layer over a substrate and disposed below a hardmask layer disposed below a mask wherein the hardmask comprises one of a carbon based material or a silicon doped carbon based component is provided. The substrate is placed in a plasma processing chamber. The hardmask layer is opened by flowing a hardmask opening gas comprising an opening component of at least one of O2, CO2, N2, or H2 with an additive of COS or CS2 into the plasma chamber, forming a plasma from the hardmask opening gas, and stopping the flow of the hardmask opening gas. Features are etched into the etch layer through the hardmask. The hardmask is removed.
In another manifestation of the invention, a method for opening a carbon-based hardmask layer formed on an etch layer over a substrate is provided.
The hardmask layer is disposed below a patterned mask. The substrate is placed in a plasma processing chamber. The hardmask layer is opened by flowing a hardmask opening gas including a COS component into the plasma chamber, forming a plasma from the hardmask opening gas, and stopping the flow of the hardmask opening gas. The hardmask layer may be made of amorphous carbon, or made of spun-on carbon, and the hardmask opening gas may further include O2.
In another manifestation of the invention, a method for opening a spun-on carbon layer in a multi-layer resist mask formed on an etch layer over a substrate is provided. The multi-layer resist mask includes the spun-on carbon layer, an oxide-based material layer disposed over the spun-on carbon layer, and a patterned mask disposed on the oxide-based material layer. The substrate is placed in a plasma processing chamber. The oxide-based material layer is patterned using the patterned mask. The spun-on carbon layer is opened using the patterned oxide-based material layer, by flowing a hardmask opening gas including a COS component into the plasma processing chamber, forming a plasma from the hardmask opening gas, and stopping the flow of the hardmask opening gas. The hardmask opening gas may further include O2. Features may be etched into the etch layer through the opened spun-on carbon layer, and then, the patterned spun-on carbon layer may be removed in the chamber.
In another manifestation of the invention, an apparatus for etching high aspect ratio features in an etch layer above a substrate and below a carbon containing hardmask below a mask is provided. A plasma processing chamber is provided comprising a chamber wall forming a plasma processing chamber enclosure, a substrate support for supporting a substrate within the plasma processing chamber enclosure, a pressure regulator for regulating the pressure in the plasma processing, chamber enclosure, at least one electrode for providing power to the plasma processing chamber enclosure for sustaining a plasma, at least one RF power source electrically connected to the at least one electrode, a gas inlet for providing gas into the plasma processing chamber enclosure, and a gas outlet for exhausting gas from the plasma processing chamber enclosure. A gas source is in fluid connection with the gas inlet and comprises an opening component source, an etch gas source, and an additive source. A controller controllably connected to the gas source, the RF bias source, and at least one RF power source and comprises at least one processor and computer readable media. The computer readable media comprises computer readable code for opening the hardmask layer, comprising computer readable code for flowing a hardmask opening gas comprising an opening component of at least one of O2, CO2, N2, or H2 from the opening component source with an additive of COS or CS2 from the additive source into the plasma chamber, computer readable code for forming a plasma from the hardmask opening gas, and computer readable code for stopping the flow of the hardmask opening gas, computer readable code for etching features into the etch layer through the hardmask, comprising computer readable code for providing an etch gas from the etch gas source, computer readable code for forming a plasma from the etch gas, and computer readable code for stopping the etch gas, and computer readable code for removing the hardmask.
In another manifestation of the invention, an apparatus for etching an etch layer over a substrate using a multi-layer resist mask formed thereon is provided. The multi-layer resist mask includes a spun-on carbon layer formed on the etch layer, an oxide-based material layer disposed on the spun-on carbon layer, and a patterned mask disposed on the oxide-based material layer. The apparatus comprises a plasma processing chamber. The plasma processing chamber includes a chamber wall forming a plasma processing chamber enclosure, a substrate support for supporting a substrate within the plasma processing chamber enclosure, a pressure regulator for regulating the pressure in the plasma processing chamber enclosure, at least one electrode for providing power to the plasma processing chamber enclosure for sustaining a plasma, at least one RF power source electrically connected to at least one electrode, a gas inlet for providing gas into the plasma processing chamber enclosure, and a gas outlet for exhausting gas from the plasma processing chamber enclosure. The apparatus further comprises a gas source in fluid connection with the gas inlet, including a patterning gas source, an opening gas source and an etch gas source, and a controller controllably connected to the gas source, the RF bias source, and at least one RF power source. The controller includes at least one processor and computer readable media. The computer readable media includes computer readable code for patterning the oxide-based material layer using the patterned mask, computer readable code for opening the spun-on carbon layer using the patterned oxide-based material layer which comprises computer readable code for flowing a hardmask opening gas including a COS component into the plasma processing chamber, computer readable code for forming a plasma from the hardmask opening gas, and computer readable code for stopping the flow of the hardmask etching gas. The computer readable media further comprises computer readable code for etching features into the etch layer through the opened spun-on carbon layer which includes computer readable code for providing an etch gas from the etch gas source, computer readable code for forming a plasma from the etch gas, and computer readable code for stopping the etch gas. The computer readable media also comprises computer readable code for removing the patterned spun-on carbon layer.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.
The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
The present invention will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.
To facilitate understanding,
A gas source 224 is connected to the etch reactor 200 and supplies the etch gas into a plasma region 240 of the etch reactor 200 during the etch processes. In this example, the gas source 224 comprises an opening gas source 264, an etch gas source 266, and a COS or CS2 source 268, which provide the gases used for the hardmask opening gas.
A bias RF source 248, a first excitation RF source 252, and a second excitation RF source 256 are electrically connected to the etch reactor 200 through a controller 235 to provide power to the electrodes 204, 206, 208, and 210. The bias RF source 248 generates bias RF power and supplies the bias RF power to the etch reactor 200. Preferably, the bias RF power has a frequency between 1 kilo Hertz (kHz) and 10 mega Hertz (MHz). More preferably, the bias RF power has a frequency between 1 MHz and 5 MHz. Even more preferably, the bias RF power has a frequency of about 2 MHz.
The first excitation RF source 252 generates source RF power and supplies the source RF power to the etch reactor 200. Preferably, this source RF power has a frequency that is greater than the bias RF power. More preferably, this source RF power has a frequency that is between 10 MHz and 40 MHz. Most preferably, this source RF power has a frequency of 27 MHz.
The second excitation RF source 256 generates another source RF power and supplies the source RF power to the etch reactor 200, in addition to the RF power generated by the first excitation RF source 252. Preferably, this source RF power has a frequency that is greater than the bias RF source and the first RF excitation source. More preferably, the second excitation RF source has a frequency that is greater than or equal to 40 MHz. Most preferably, this source RF power has a frequency of 60 MHz.
The different RF signals may be supplied to various combinations of the top and bottom electrodes. Preferably, the lowest frequency of the RF should be applied through the bottom electrode on which the material being etched is placed, which in this example is the bottom central electrode 208.
The controller 235 is connected to the gas source 224, the bias RF source 248, the first excitation RF source 252, and the second excitation RF source 256. The controller 235 controls the flow of the etch gas into the etch reactor 200, as well as the generation of the RF power from the three RF sources 248, 252, 256, the electrodes 204, 206, 208, and 210, and the exhaust pump 220.
In this example, confinement rings 202 are provided to provide confinement of the plasma and gas, which pass between the confinement rings and are exhausted by the exhaust pump.
CPU 322 is also coupled to a variety of input/output devices, such as display 304, keyboard 310, mouse 312, and speakers 330. In general, an input/output device may be any of: video displays, track balls, mice, keyboards, microphones, touch-sensitive displays, transducer card readers, magnetic or paper tape readers, tablets, styluses, voice or handwriting recognizers, biometrics readers, or other computers. CPU 322 optionally may be coupled to another computer or telecommunications network using network interface 340. With such a network interface, it is contemplated that the CPU might receive information from the network, or might output information to the network in the course of performing the above-described method steps. Furthermore, method embodiments of the present invention may execute solely upon CPU 322 or may execute over a network such as the Internet in conjunction with a remote CPU that shares a portion of the processing.
In addition, embodiments of the present invention further relate to computer storage products with a computer-readable medium that have computer code thereon for performing various computer-implemented-operations. The media and computer code may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well known and available to those having skill in the computer software arts. Examples of computer-readable media include, but are not limited to: magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and holographic devices; magneto-optical media such as floptical disks; and hardware devices that are specially configured to store and execute program code, such as application-specific integrated circuits (ASICs), programmable logic devices (PLDs) and ROM and RAM devices. Examples of computer code include machine code, such as produced by a compiler, and files containing higher level of code that are executed by a computer using an interpreter. Computer readable media may also be computer code transmitted by a computer data signal embodied in a carrier wave and representing a sequence of instructions that are executable by a processor.
To facilitate understanding of the invention,
The substrate 404, etch layer 408, hardmask layer 412, and mask 416 are placed in the etch reactor 200 (step 104). The mask 416 is etched through the photoresist mask to pattern the mask 416, as shown in
The hardmask layer is opened using a COS or CS2 additive (step 108).
An example recipe for a hardmask opening provides a chamber pressure of 20 mTorr. The electrostatic chuck temperature is maintained at −10° C. An upper electrode temperature is maintained at 140° C. Alternatively, the electrostatic chuck temperature is maintained at 30° C., and the upper electrode temperature is maintained at 110° C. An opening gas of 200 sccm O2 and 10 sccm COS is provided. 600 watts at 60 MHz is provided for 52 seconds. For this example recipe, the etch rate of removing the hardmask is around 6000 A/min.
Features are etched into the etch layer through the opened hardmask layer (step 112). The recipe used depends on the type of material that has to be etched. For TEOS, BPSG, low k− dielectric, FSG, SiN, etc., different process recipes are required.
In other embodiments of the invention, the etch layer may be undoped or doped silicon dioxide based material (e.g. TEOS, BPSG, FSG etc), organo-silicate glass (OSG), porous OSG, silicon nitride based material, silicon oxynitride based material, silicon carbide based material, low k− dielectric or any metal gate material.
In this example, the etched features are passivated (step 116). In this example, a chamber pressure of 20 mTorr. The electrostatic chuck temperature is maintained at −10° C. An upper electrode temperature is maintained at 140° C. A passivating gas of 200 sccm O2 and 10 sccm COS is provided. 600 watts at 60 MHz is provided. Without being bound by theory, it is believed that the passivation provides a barrier that protects the etch layer during stripping or removing the hardmask layer. Most likely the S bonds to carbon from the amorphous carbon forming structures containing C—S or C—S—S—C bonding. It is believed that this type of compound has a good etch resistance.
The hardmask is removed (step 120). A normal organic layer stripping process, such as providing an O2 stripping gas may be used. The passivation layer may be used to protect low-k dielectric and/or organic dielectric layers during the stripping. In the alternative, an additive of COS or CS2 may be added to the stripping gas to further provide a protective layer during the stripping process. A wet-clean process may be used after the removal of the hardmask to remove any remaining passivation layer, without damaging the etch layer.
In one example, the opening gas is fluorine free. Whether fluorine is used depends on the material of the hardmask. A fluorine free opening gas is able to open a hardmask layer containing no silicon. In another example, where the hardmask layer has a silicon component, the opening gas has a fluorine component. The fluorine composition has to be properly adjusted in order to have enough selectivity to the mask 416 layer.
In addition to COS or CS2 the stripping gas preferably comprises at least one of O2, CO2, N2, or H2. More preferably the stripping gas comprises a bombarding component such as Ar. More preferably, the stripping gas comprises O2 or N2. Most preferably, the stripping gas comprises O2.
Other examples do not provide a passivation step or provide a passivation without a COS and CS2 additive.
In one example, the hardmask can be amorphous carbon or it can contain Si incorporated into the amorphous carbon structure. Most preferably, the hardmask layer is amorphous carbon. Such a hardmask may be spun on or chemical vapor deposited (CVD) or may be deposited by other methods. In other examples, the hardmask layer has a carbon component, such as a carbon based hardmask, such as amorphous carbon, or a silicon based hardmask with a carbon component. The invention can be used in order to etch any aspect ratio feature in such a layer.
Preferably, the mask layer is of silicon oxide or SiON. Preferably, the mask layer and the etch layer have similar etch properties. Preferably, the hardmask layer may be selectively etched with respect to the mask layer and the etch layer may be selectively etched with respect to the hardmask layer.
Preferably, the invention provides a high aspect ratio etch of greater than 20:1. More preferably the invention provides a high aspect ratio etch of greater than 25:1.
In accordance with one embodiment of the present invention, a multi-layer resist (MLR) mask is used in etching of an etch layer formed over a substrate.
For example, the patterned mask 610 may be a patterned photoresist (PR) mask having a thickness of about 120 nm. The PR mask 610 may be patterned with the immersion 193 nm photolithography having a CD about 70 nm. The oxide-based material layer 608 may be made of a SiO2-based material, such as a spin-on glass (SOG) layer with a thickness of about 45 nm. The spun-on carbon layer 606 may be used as a hardmask in etching of the underlying etching layer 604, and may also be referred to as spun-on hardmask (SOH). The spun-on carbon layer 606 may have a thickness of about 350 nm. Compared with amorphous carbon in the previous embodiment, which typically requires a sputter film deposition process, the spun-on carbon layer is formed by spin coating using a conventional resist coater and thus less expensive. Spun-on carbon is more polymer-like and thus softer than amorphous carbon. Compared with other organic films, on the other hand, the spun-on carbon has higher concentration of carbon and lower concentration of oxygen. The spun-on carbon layer may be formed using an organic planarization material, such as NFC, available from JSR Micro, Inc., Sunnyvale, Calif., and other material such as—SOC (Spin-On Carbon), SOH (Spin-On Hardmask) available from Shipley Co. Inc., Marlborough, Mass., TOK, Japan, JSR Micro, Inc., and the like. The etch layer 604 may be a TEOS (tetra-ethyl-ortho-silicate, tetra-ethoxy-silane) or PE-TEOS layer having a thickness of about 400 nm. The substrate 602 may be made of SiN, or other silicon-based material. It should be noted that the present invention is not limited to specific materials of the etch layer or the substrate.
As shown in
Referring back to
Referring back to
While this invention has been described in terms of several preferred embodiments, there are alterations, permutations. modifications, and various substitute equivalents, which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and various substitute equivalents as fall within the true spirit and scope of the present invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2008/062411 | 5/2/2008 | WO | 00 | 4/1/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 61066147 | May 2007 | US | |
| 61044012 | Apr 2008 | US |
