ORGANIC LINE WIDTH ROUGHNESS WITH H2 PLASMA TREATMENT
An apparatus for reducing very low frequency line width roughness (LWR) is provided. A plasma processing chamber is provided, comprising a chamber wall, a substrate support, a pressure regulator, at least one antenna, a gas inlet, and a gas outlet. A gas source comprises an etchant gas source and a H2 treatment gas source. A controller comprises at least one processor and computer readable media, comprising computer readable code for treating a patterned organic mask, comprising computer readable code for flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas, computer readable code for forming a plasma, and computer readable code for stopping the flow of the treatment gas, and computer readable code for etching the etch layer through the treated patterned organic mask.
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This application is a divisional of and claims benefit to co-pending U.S. patent application Ser. No. 12/175,153 filed on Jul. 17, 2008, entitled “Organic Line Width Roughness with H2 Plasma Treatment,” by Adams et al., which is hereby incorporated by reference for all purposes.
BACKGROUND OF THE INVENTIONThe present invention relates to the formation of semiconductor devices.
During semiconductor wafer processing, features of the semiconductor device are defined in the wafer using well-known patterning and etching processes. In these processes, a photoresist (PR) material is deposited on the wafer and then is exposed to light filtered by a reticle. The reticle is generally a glass plate that is patterned with exemplary feature geometries that block light from propagating through the reticle.
After passing through the reticle, the light contacts the surface of the photoresist material. The light changes the chemical composition of the photoresist material such that a developer can remove a portion of the photoresist material. In the case of positive photoresist materials, the exposed regions are removed, and in the case of negative photoresist materials, the unexposed regions are removed. Thereafter, the wafer is etched to remove the underlying material from the areas that are no longer protected by the photoresist material, and thereby define the desired features in the wafer.
SUMMARY OF THE INVENTIONTo achieve the foregoing and in accordance with the purpose of the present invention, a method for reducing very low frequency line width roughness (LWR) in forming etched features in an etch layer disposed below a patterned organic mask is provided. The patterned organic mask is treated to reduce very low frequency line width roughness of the patterned organic mask, comprising flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas, forming a plasma from the treatment gas, and stopping the flow of the treatment gas. The etch layer is etched through the treated patterned organic mask with the reduced very low LWR.
In another manifestation of the invention a method for reducing very low frequency line width roughness (LWR) in forming etched features in a conductive layer disposed below a hard mask layer disposed below an etch layer disposed below a patterned photoresist mask forming a stack on a wafer is provided. The wafer is placed in a process chamber. The patterned photoresist mask is treated to reduce very low frequency line width roughness of the patterned photoresist mask, comprising flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas into the process chamber, forming a plasma from the treatment gas, and stopping the flow of the treatment gas. The etch layer is etched through the treated patterned photoresist mask. The hard mask layer is etched through the etched layer. The conductive layer is etched through the hard mask layer. The wafer is removed from the process chamber, so that the treating the patterned organic mask, etching the etch layer, etching the hard mask layer, and etching the conductive layer are all done in situ in the same process chamber.
In another manifestation of the invention an apparatus for reducing very low frequency line width roughness (LWR) in forming etched features in an etch layer, disposed below a patterned organic mask with mask features is provided. A plasma processing chamber is provided, comprising a chamber wall forming a plasma processing chamber enclosure, a substrate support for supporting a wafer within the plasma processing chamber enclosure, a pressure regulator for regulating the pressure in the plasma processing chamber enclosure, at least one antenna for providing inductively coupled power to the plasma processing chamber enclosure for sustaining a plasma, 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 etchant gas source and a H2 treatment gas source. A controller is controllably connected to the gas source and the at least one antenna and comprises at least one processor and computer readable media. The computer readable media comprises computer readable code for treating the patterned organic mask to reduce very low frequency line width roughness of the patterned organic mask, comprising computer readable code for flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas, computer readable code for forming a plasma from the treatment gas, and computer readable code for stopping the flow of the treatment gas, and computer readable code for etching the etch layer through the treated patterned organic mask with the reduced very low LWR.
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,
In an example of an implementation of the invention, a wafer is provided with an etch layer and a photoresist mask.
In this example, the patterned photoresist mask 216 has a very low frequency line edge roughness. A very low frequency line width roughness repetition length of greater than 500 nm. More preferably, the very low line edge roughness repetition length is greater than 550 nm. Line width roughness is the 3σ value of line width in a given inspection area, which may be calculated according to:
The wafer 204 is placed in an inductively coupled plasma processing chamber (step 102).
The TCP power controller 350 sets a set point for TCP power supply 351 configured to supply a radio frequency signal at 13.56 MHz, tuned by a TCP match network 352, to a TCP coil 353 located near the plasma chamber 304. An RF transparent window 354 is provided to separate TCP coil 353 from plasma chamber 304 while allowing energy to pass from TCP coil 353 to plasma chamber 304.
The bias power controller 355 sets a set point for bias power supply 356 configured to supply an RF signal, tuned by bias match network 357, to a chuck electrode 308 located within the plasma chamber 304 creating a direct current (DC) bias above electrode 308 which is adapted to receive a substrate 306, such as a semi-conductor wafer work piece, being processed.
A gas supply mechanism or gas source 310 includes a source or sources of gas or gases 316 attached via a gas manifold 317 to supply the proper chemistry required for the process to the interior of the plasma chamber 304. A gas exhaust mechanism 318 includes a pressure control valve 319 and exhaust pump 320 and removes particles from within the plasma chamber 304 and maintains a particular pressure within plasma chamber 304.
A temperature controller 380 controls the temperature of a cooling recirculation system provided within the chuck electrode 308 by controlling a cooling power supply 384. The plasma processing system also includes electronic control circuitry 370. The plasma processing system may also have an end point detector.
CPU 422 is also coupled to a variety of input/output devices, such as display 404, keyboard 410, mouse 412, and speakers 430. 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 422 optionally may be coupled to another computer or telecommunications network using network interface 440. 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 422 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 tangible 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 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.
The patterned PR mask 220 is treated to reduce very low frequency line width roughness (step 104). This is accomplished by first flowing a treatment gas comprising H2 into the process chamber, where the treatment gas has a flow rate and the H2 has a flow rate that is at least 50% of the flow rate of the treatment gas. Preferably, the treatment gas consists essentially of H2 and Ar. More preferably, the treatment gas consists essentially of H2. The treatment is formed into a plasma using a low bias (step 112). Preferably, the bias voltage for the low bias is between 0 to 100 volts. More preferably, the bias voltage for the low bias is between 0 to 50 volts. Most preferably, the bias voltage for low bias is 0 volts. The flow of the treatment step is stopped (step 116), to end the PR mask treatment.
A specific example of a treatment recipe provides an H2 treatment gas of 100 sccm H2 and 100 sccm Ar at a pressure of 10 mT. Ranges of the treatment gas in this example recipe may provide 50-500 sccm H2 and 0-500 sccm Ar, at pressures between 2-40 mT. The power provided to form a plasma from the treatment gas is 200-1500 W at 13.56 MHz. More specifically, the power is 1000 W. The bias voltage is 0 volts. An electrostatic chuck temperature of 60° C. is provided. The treatment process is maintained for 5-60 seconds.
The organic ARC layer 216 is then etched (step 120), using a conventional organic ARC open process based on the specific material of the etch layer.
Without being bound by theory, it was thought that very low frequency line edge roughness with a repetition rate greater than 500 nm, preferably 550 nm, in a patterned photoresist mask could not be reduced. It was unexpectedly found that an H2 plasma treatment with low bias voltage would reduce very low frequency line width roughness.
Other EmbodimentsIn other embodiments the H2 treatment to reduce very low frequency LWR may be performed on other patterned organic masks. For example, an organic ARC layer that has been opened using a conventional process may have very low frequency LWR. The H2 treatment may then be applied to the opened organic ARC layer to reduce the very low frequency LWR. In such an example, instead of the organic ARC layer being the etch layer, the hard mask layer is the etch layer that is etched subsequent to the H2 treatment.
In other embodiment a high bias power may be used during the H2 treatment. In other embodiments the etch layer or other layers under the etch layer may be dielectric layers. Such embodiments may have an ARC layer or may not have an ARC layer or may have one or more additional layers. Such embodiments may or may not have a conductive layer and/or a hard mask layer. If the etch layer is a dielectric layer, an embodiment may use a capacitively coupled process chamber instead of an inductively coupled process chamber. In other embodiments, the treatment may be done in a different chamber than the etching.
While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, 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.
Claims
1. An apparatus for reducing very low frequency line width roughness (LWR) in forming etched features in an etch layer, disposed below a patterned organic mask with mask features, comprising:
- a plasma processing chamber, comprising: a chamber wall forming a plasma processing chamber enclosure; a substrate support for supporting a wafer within the plasma processing chamber enclosure; a pressure regulator for regulating the pressure in the plasma processing chamber enclosure; at least one antenna for providing inductively coupled power to the plasma processing chamber enclosure for sustaining a plasma; 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 in fluid connection with the gas inlet, comprising; an etchant gas source; and a H2 treatment gas source;
- a controller controllably connected to the gas source and the at least one antenna, comprising: at least one processor; and computer readable media, comprising: computer readable code for treating the patterned organic mask to reduce very low frequency line width roughness of the patterned organic mask, comprising: computer readable code for flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas; computer readable code for forming a plasma from the treatment gas; and computer readable code for stopping the flow of the treatment gas; and computer readable code for etching the etch layer through the treated patterned organic mask with the reduced very low LWR.
2. The apparatus, as recited in claim 1, wherein the computer readable code for forming a plasma comprises computer readable code for providing a low bias.
3. The apparatus, as recited in claim 2, wherein the treatment gas is halogen free.
4. The apparatus, as recited in claim 2, wherein the treatment gas consists essentially of Ar and H2.
5. The apparatus, as recited in claim 2, wherein the treatment gas consists essentially of H2.
6. The apparatus, as recited in claim 5, wherein the computer readable code for forming a plasma comprises computer readable code for using no more than 1500 watts of RF power.
7. The apparatus, as recited in claim 2, wherein the low bias is between 0 to 100 volts.
8. The apparatus, as recited in claim 2, wherein the low bias is between 0 to 50 volts.
9. The apparatus, as recited in claim 2, wherein the low bias is 0 volts.
10. The apparatus, as recited in claim 1, wherein the very low frequency LWR has a roughness repetition length of greater than 500 nm.
11. The apparatus, as recited in claim 10, wherein the very low frequency LWR of the patterned organic mask after treatment is less than the very low frequency LWR before treatment.
12. The apparatus, as recited in claim 11, further comprising:
- computer readable code for placing a wafer with the etch layer and patterned organic mask in a process chamber before the treating the patterned organic mask; and
- computer readable code for removing the wafer from the process chamber after etching the etch layer.
13. The apparatus, as recited in claim 12, wherein the plasma processing chamber is an inductively coupled TCP process chamber.
14. The apparatus, as recited in claim 13, wherein the organic mask is a photoresist mask.
15. The apparatus, as recited in claim 1, wherein the treatment gas is halogen free.
16. The apparatus, as recited in claim 1, wherein the treatment gas consists essentially of Ar and H2.
17. The apparatus for reducing very low frequency line width roughness (LWR) with a roughness repetition length of greater than 500 nm in forming etched features in an etch layer disposed below a patterned organic mask, wherein a hard mask layer is below the etch layer and a conductive layer is below the hard mask layer, comprising:
- a plasma processing chamber, comprising: a chamber wall forming a plasma processing chamber enclosure; a substrate support for supporting a wafer within the plasma processing chamber enclosure; a pressure regulator for regulating the pressure in the plasma processing chamber enclosure; at least one antenna for providing inductively coupled power to the plasma processing chamber enclosure for sustaining a plasma; 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 in fluid connection with the gas inlet, comprising; an etchant gas source; and a H2 treatment gas source;
- a controller controllably connected to the gas source and the at least one antenna, comprising: at least one processor; and computer readable media, comprising: computer readable code for treating the patterned organic mask to reduce very low frequency line width roughness with a roughness repetition length of greater than 500 nm of the patterned organic mask, comprising: computer readable code for flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas; computer readable code for forming a plasma from the treatment gas; computer readable code for stopping the flow of the treatment gas; and computer readable code for etching the etch layer through the treated patterned organic mask with the reduced very low LWR; computer readable code for etching the hard mask layer, and computer readable code for etching the conductive layer, before removing the wafer from the process chamber, so that the treating the patterned organic mask, etching the etch layer, etching the hard mask layer, and etching the conductive layer are all done in situ in the same process chamber.
18. An apparatus for reducing very low frequency line width roughness (LWR) in forming etched features in a conductive layer disposed below a hard mask layer disposed below an ARC layer disposed below a patterned photoresist mask forming a stack on a wafer, comprising:
- a plasma processing chamber, comprising: a chamber wall forming a plasma processing chamber enclosure; a substrate support for supporting a wafer within the plasma processing chamber enclosure; a pressure regulator for regulating the pressure in the plasma processing chamber enclosure; at least one antenna for providing inductively coupled power to the plasma processing chamber enclosure for sustaining a plasma; 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 in fluid connection with the gas inlet, comprising; an etchant gas source; and a H2 treatment gas source;
- a controller controllably connected to the gas source and the at least one antenna, comprising: at least one processor; and computer readable media, comprising: computer readable code for placing the wafer in a process chamber; computer readable code for treating the patterned photoresist mask to reduce very low frequency line width roughness of the patterned photoresist mask, comprising: computer readable code for flowing a treatment gas comprising H2, wherein the treatment gas has a flow rate and H2 has a flow rate that is at least 50% of the flow rate of the treatment gas into the process chamber; computer readable code for forming a plasma from the treatment gas; and computer readable code for stopping the flow of the treatment gas; computer readable code for etching the ARC layer through the treated patterned photoresist mask; computer readable code for etching the hard mask layer through the ARC layer; computer readable code for etching the conductive layer through the hard mask layer; and computer readable code for removing the wafer from the process chamber, so that the treating the patterned organic mask, etching the ARC layer, etching the hard mask layer, and etching the conductive layer are all done in situ in the same process chamber.
Type: Application
Filed: Sep 26, 2012
Publication Date: Apr 11, 2013
Applicant: LAM RESEARCH CORPORATION (Fremont, CA)
Inventor: Lam Research Corporation (Fremont, CA)
Application Number: 13/627,901
International Classification: H01L 21/3065 (20060101);