The present invention relates to the formation of semiconductor devices. More particularly, the invention relates to the etching of features into a dielectric layer.
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.
One problem in such processes is that line edge roughness of the mask features may be transferred to the etch features.
To achieve the foregoing and in accordance with the purpose of the present invention, a method of forming features in an etch layer disposed below a mask with features is provided. The mask is conditioned. The conditioning, comprises providing a conditioning gas consisting essentially of at least one noble gas, forming a plasma from the conditioning gas, and exposing the mask to the plasma from the conditioning gas. The features of the mask are shrunk. Features are etched into the etch layer through the shrunk features of the mask.
In another manifestation of the invention, an apparatus for forming features in an etch layer is provided, where the etch layer is supported by a substrate and wherein the etch layer is covered by an etch mask with mask features with a first CD. A plasma processing chamber is provided. The plasma processing chamber comprises 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, 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 a noble gas source, a deposition gas source, a profile shaping phase gas source, and an etching gas source. A controller is controllably connected to the gas source and the at least one electrode and comprises at least one processor, and computer readable media. The computer readable media comprises computer readable code for conditioning the etch mask, comprising computer readable code for providing a flow of only noble gas from the noble gas source, computer readable code for energizing the at least one electrode to create a plasma from the noble gas, and computer readable code for stopping the flow of the noble gas to the plasma processing chamber enclosure, computer readable code for shrinking features of the etch mask, comprising computer readable code for depositing a deposition layer on the mask and computer readable code for shaping a profile of the deposited layer, and computer readable code for etching features into the etch layer through the mask.
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:
FIGS. 2A-D are schematic cross-sectional views of a stack processed according to an embodiment of the invention.
FIGS. 3A-C are top views of the stack shown in FIGS. 2A-D.
FIGS. 5A-B illustrate a computer system, which is suitable for implementing a controller used in embodiments of the present invention.
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.
Some causes of line edge roughening are lack of mobility of the photoresist or mask, stress mismatch between the photoresist, mask, and etch by products (polymers), and photoresist or mask chemical modifications.
To facilitate understanding,
The mask is conditioned using a plasma from a noble gas (step 108). The substrate 204 is placed in a processing chamber.
CPU 1322 is also coupled to a variety of input/output devices, such as display 1304, keyboard 1310, mouse 1312, and speakers 1330. 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 1322 optionally may be coupled to another computer or telecommunications network using network interface 1340. 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 1322 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 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.
Preferably, the conditioning process does not significantly etch the mask or the etch layer.
A shrink mask features procedure is performed (step 112).
Features are then etched into the etch layer 208 through the formed sidewall layer 220 forming the shrunk mask features (step 116).
The photoresist and sidewall layer may then be stripped (step 120). This may be done as a single step or two separate steps with a separate deposited layer removal step and photoresist strip step. Ashing may be used for the stripping process.
In one example, a patterned mask is placed over a substrate 204, with an etch layer 208, and an ARC layer 210 (step 104). In this example, the substrate is a silicon wafer. The etch layer 208 is organosilicate glass. The patterned mask 212 is a photoresist mask. In other embodiments, the patterned mask may be other polymer type masks, such as amorphous carbon. The substrate is placed in a process chamber, such as described above.
The mask is conditioned (step 108). In this example, a conditioning gas consisting essentially of Ar is provided (step 604). A plasma is formed from the Ar gas (step 608). The pressure is set at 240 mTorr. A power of 200 Watts is provided. The mask 212 is exposed to the plasma (step 612) for typically 30 seconds. The conditioning process is then stopped.
After the conditioning is complete, a shrink process is provided to shrink the mask features (step 112).
In this example, the deposit conformal layer phase (step 704) comprises providing a deposition gas and generating a plasma from the deposition gas to form a deposition layer. In this example, the deposition gas comprises a polymer forming recipe. An example of such a polymer forming recipe is a hydrocarbon gas, such as CH4 and C2H4, and a fluorocarbon gas, such as CH3F, CH2F2, CHF3, C4F6, and C4F8. Another example of a polymer forming recipe would be a fluorocarbon chemistry and a hydrogen containing gas, such as a recipe of CF4 and H2. In a preferred embodiment, CF4 and H2 have a molar ratio (CF4:H2) in the range of 1:2 to 2:1. In this example, power is supplied at 400 Watts at 2 MHz and 800 Watts at 27 MHz.
In this example, the shape profile phase (step 708) comprises providing a profile shaping phase gas and generating a profile shaping phase plasma from the profile shaping phase gas to shape the profile of the deposition layer. The profile shaping phase gas is different from the deposition gas. The deposition phase (step 704) and the profile shaping phase (step 708) occur at different times sequentially in a cyclical process. In this example, the profile shaping gas comprises a fluorocarbon chemistry, such as CF4, CHF3, and CH2F2. Other additives such as O2, N2, and H2 may be added. In this example, power is supplied at 0 Watts at 2 MHz and 800 Watts at 27 MHz.
In other embodiments, a shrink cycle may further include additional deposition and/or profile shaping steps.
After the shrink is complete, the etch layer is etched (step 116). A typical process for etching a dielectric material or a conductor material (Si, Al, W, WSI, etc) can be used.
To strip the photoresist and the mask shrink (step 120) an oxygen ashing may be used.
Providing the inert gas plasma conditioning before the shrink has been unexpectedly found to beneficially reduce line edge roughness of the resulting feature.
In a preferred embodiment of the invention, the mask conditioning, the mask feature shrink, and etching of the etch layer may be done in situ in the same etch chamber, as shown.
While in this example the mask is a photoresist mask, in other embodiments, the mask may be of other polymer-type masks such as amorphous carbon, amorphous Si, SiO2 or SiN, SiC, TiN, etc.
While this invention has been described in terms of several preferred embodiments, there are alterations, modifications, 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, modifications, permutations, and various substitute equivalents as fall within the true spirit and scope of the present invention.