This invention relates to the control of plasma etch process uniformity in an ionized physical vapor deposition (iPVD) processing of semiconductor wafers, and, in general, to metallization plasma processing in semiconductor technology. This invention more particularly relates to processes that combine iPVD and etch processing.
Ionized PVD has been utilized in semiconductor processing for metallization and interconnects and shows promise for extending processing to submicron technology. In the metallization of high aspect ratio (HAR) via holes and trenches on semiconductor wafers, barrier layers and seed layers must provide good sidewall and bottom coverage across the wafer. Ionized PVD is used for barrier and seed layer metallization in advanced IC wafers. Ionized PVD provides good sidewall and bottom coverage in via and trench structures. However, the ionized deposition requirements become more critical as the geometries shrink and as the via dimensions are further reduced below 0.15 micrometers. In such applications, it is highly desirable to have an ionized PVD process where bottom coverage and sidewall coverage are well balanced and overhang is minimized.
The Metallization process may use an ionized physical vapor deposition (iPVD) apparatus having the features described in U.S. Pat. Nos. 6,080,287, 6,132,564, 6,197,165, 6,287,435 and 6,719,886 which patents are hereby expressly incorporated by reference herein. The processing apparatus described in these patents are particularly well suited for sequential or simultaneous deposition and etching. The sequential deposition and etching process can be applied to a substrate in the same process chamber without breaking vacuum or moving the wafer from chamber to chamber. Sequential deposition and etching processes are described in U.S. Pat. No. 6,755,945, hereby expressly incorporated by reference herein. The configuration of the apparatus allows rapid change from ionized PVD deposition mode to etching mode or from etching mode to ionized PVD deposition mode. The configuration of the apparatus also allows for simultaneous optimization of ionized PVD process control parameters during deposition mode and etching process control parameters during etching mode. The consequence of these advantages is a high throughput of wafers with superior via metallization and subsequent electroplated fill operation.
Notwithstanding the advantages of ionized PVD, there are still some constraints to using iPVD at the maximum of its performance. For example, existing hardware does not allow for simultaneous optimizing of the uniformity in both deposition and etching over a wide process window, specifically a wide pressure range. An annular target provides excellent flat field deposition uniformity, but geometrically is limited to the use of large area inductively coupled plasmas (ICP) to generate large size low-pressure plasma for uniform etch processes. An axially situated ICP source is optimal to ionize metal vapor sputtered from the target and fill features in the center of the wafer, but such a source generates an axially peaked high-density plasma profile that does not provide uniform etch in a sequential deposition-etch process or no net deposition process (NND).
The etch portion of a combined deposition-etch process occurs at increased bias at the wafer so deposited metal, typically TaN/Ta for adhesion and barrier properties or Cu for a seed layer, is removed from the flat field areas, namely the horizontal surfaces like the top and bottom planes of a feature, but remains deposited at the sidewalls of the features. The process requires fully identical non-uniformity distributions of the etch and deposition processes, or highly uniform processes.
An objective of the present invention is to generate and adjust plasma so as to contribute to the uniform plasma processing in simultaneous and sequential processes that combine deposition and etching. One particular objective of the invention is to provide uniform plasma processing for high aspect ratio feature coverage by ionized PVD, particularly for large diameter wafers, for example, 300 millimeter (mm) wafers.
The present invention provides for the production of a plasma by a large electrode, a ring-shape antenna in the preferred embodiment, and for the adjusting of the plasma density profile by use of an axially positioned device having hollow-body geometry. The device is provided in the vacuum space of the plasma source into which the energy is coupled. The device geometry, including its dimensions and shape, and its placement in the chamber may be optimized for the particular chamber geometry and process pressure range.
These and other objects and advantages of the present invention will be more readily apparent from the following detailed description of illustrated embodiments of the invention.
FIGS. 7A-B are elevational views, respectively, of conical and spherical plasma adjusting devices according to other embodiments of the present invention.
Embodiments of the present invention are described in the context of the apparatus 10 of
A typical iPVD system 10, as illustrated in
While plasma processing systems are designed with maximum care and computer simulation, in many cases only a real process performed with a real plasma will reveal the impact of some hardware components of a processing chamber and their interaction with the plasma. Typically, this impact concerns the uniformity of the processing at the wafer. For example, non-uniformity in processing can be generated when changing processing conditions, for example, by interaction of a static magnetic field from a metal source, from inductively coupled plasma (ICP) antenna geometry, and from the simultaneous combination of different plasma processes within the chamber.
Existing iPVD systems, such as those described in U.S. Pat. Nos. 6,080,287, 6,287,435 and 6,719,886, for example, have an on-axis ICP source which produces a strongly peaked plasma density. Such a plasma can provide excellent ionization of the metal sputtered from a target and the subsequent transport of the sputtered metal to a wafer.
Such an iPVD system 10 exhibits a plasma density profile 21 that is peaked at the center, as illustrated in
In accordance with certain principles of the present invention, to solve etch rate uniformity problems with minimal impact on the deposition process, an iPVD system 50 is provided in which the center ICP source 12 of
More specifically, in the embodiment illustrated in
One example of the device 40 is shown in
A typical geometrical shape for the device 40 is that of a hollow body in cylindrical form or of frusto-conical geometry having a bottom radius larger than the upper radius, as for example the device 30a illustrated in
In applicant's U.S. patent application Ser. No. 10/854,607, filed May 26, 2004, hereby expressly incorporated by reference herein, a buffer device is disclosed which provides a complementary effect on the radial distribution of metal atoms and ions inside a processing chamber. With the present invention, devices are provided having shapes for buffering performance by improving plasma uniformity and radial plasma density control.
Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.