Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2001-01-22
2003-06-03
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298060, C204S298070, C204S298120, C204S298190, C204S298200
Reexamination Certificate
active
06572744
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a system and method for depositing a thin film of material onto a surface of an object, such as a semiconductor or thin film head substrate, and in particular to a dual collimation system and method for depositing thin material films onto a semiconductor or a thin film head substrate.
Plasma sputtering is a physical vapor deposition (PVD) technique for thin film deposition. The process of sputtering a thin film onto an object is well known. The sputtering process may be used to deposit a thin film of material onto a plurality of different surfaces which may include a magnetic media substrate, magneto-optical media substrate, a semiconductor substrate, a thin-film head substrate, a flat-panel display substrate and the like. In the sputtering process, it is desired to place a thin film of atoms of a particular type, such as a cobalt, onto the substrate. A typical sputtering apparatus may include a piece of target material, a vacuum or low-pressure sputtering chamber, and a substrate located on a substrate holder beneath the target material. To cause some of the atoms or compound species from the piece of target material to deposit themselves on the substrate surface, an electrical DC, pulsed DC, AC or RF power supply is connected between the target material (typically via a bonded backing plate) and the chamber, and a low-pressure (e.g., 0.5 mTorr to 30 mTorr) inert gas (e.g., Ar) and/or a reactive gas (e.g., N
2
, O
2
or the like) medium is established within the chamber. When a high enough voltage is applied to the target material, a plasma is formed with the atoms being released by the target material via ion bombardment by the plasma ions. The gas in the chamber may have a low pressure so that a majority of the atoms from the target material travel from the target material onto the substrate surface without colliding with any gas molecules (i.e., negligible or minimal scattering of the sputter species). In many thin-film deposition applications, to obtain the best quality thin films, it is desirable for the atoms to strike the surface of the substrate at a 90° angle (i.e., normal incidence) which provides a collimated stream of atoms.
In order to improve the quality of the thin film produced by the sputtering apparatus, the target may be located a greater distance from the substrate, which is known as a long-throw or natural sputtering apparatus. In the long-throw or natural sputtering apparatus, the atoms from the target material travel a longer distance so that the atoms that are not going to strike approximately perpendicular to the surface of the substrate, and within a space cone with relatively narrow angular distribution around the central normal axis, may strike the sides of the sputtering chamber. Thus, a larger percentage of the atoms or sputter species from the target material strike the surface of the substrate close to a perpendicular angle within a narrow angular distribution from the normal axis. The long-throw sputtering apparatus has several limitations. First, because the atoms or sputter species are traveling a greater distance to the surface of the substrate, they may strike more gas molecules due to scattering collisions and form poorer quality films unless the pressure of the gas in the sputtering chamber is reduced. If the gas pressure is reduced too much, however, there will not be sufficient gas pressure in the chamber to sustain a stable plasma. Typically, the long-throw sputtering processes require gas pressures preferably below 1 mTorr, thus limiting the process window for this technique. Moreover, the long-throw sputtering systems require more stringent vacuum pumping due to larger process chamber volumes and surface area.
Another technique to improve the quality of the thin films (i.e., improving the total number of atoms or sputter species which strike the surface of the substrate at a perpendicular angle or near perpendicular angles) is to place a perforated plate or a physical collimator in the chamber between the substrate and the target surface. This apparatus is called a physical collimation sputtering apparatus. The perforated plate has a predetermined aspect ratio (i.e., the ratio of the height of the hexagonal or circular holes in the plate to the diameter of the holes in the plate) so that most atoms which pass through the plate will strike the surface at approximately a right angle or within a narrow-angle cone around the perpendicular axis. Thus, the perforated plate acts as a spatial filter for the atoms or sputter species and prevents the atoms or sputter species emitted from the target material at more than some predetermined angle (outside a predetermined cone) from striking the surface of the substrate. The atoms or sputter species which strike the plate, but do not pass through the physical collimator holes, are deposited on the plate or within the holes. Therefore, as the plate is bombarded by more and more atoms, the holes of the plate will gradually become coated and eventually plugged up and the plate must be replaced after processing a certain number of substrates. Therefore, the total lifetime of the plate in the chamber is limited and the plate must be replaced often which is time consuming and reduces the overall equipment uptime. With either approach, the maximum collimation that can be achieved is limited.
Therefore, it is desirable to provide a sputtering apparatus which provides a more collimated stream of atoms or sputtering species which avoids these and other problems of known devices, and it is to this end that the present invention is directed.
SUMMARY OF THE INVENTION
In accordance with the invention, a dual collimated sputtering apparatus and method are provided which improves step coverage and bottom coverage in large aspect ratio contacts and vias in a semiconductor integrated circuit chip, improves bottom coverage and step coverage for barriers, liners in vias, or trenches in a semiconductor device, and reduces encroachment in a lift-off patterning structure for an abutted junction (the latter used in magnetic thin-film heads). The dual collimator in accordance with the invention may have a long-throw collimator combined with one or more physical collimators. The long-throw collimator provides some initial collimation and the subsequent one or more physical collimators provide additional filtering of the sputtered flux which enhances the overall degree of collimation. In addition, since the long-throw collimator already ensures that some non-collimated atoms or sputtered species strike the walls (or shield walls) of the deposition chamber, the perforated plates of the physical collimator block a smaller fraction of the incoming flux (i.e., atoms) so that the overall lifetime of the perforated physical collimator is increased. The dual collimator apparatus may also be operated at low pressures (e.g., such as less than 2 mTorr) so that the probability of atom scattering due to a collision with background gas atoms (within the long-throw collimator) is minimized so that more collimated atoms or sputtered species strike the surface of the substrate.
In addition, the bottom coverage for a 3:1 aspect ratio (AR) semiconductor via hole improves from about 30% using conventional physical collimation to as much as 50% using the dual collimation apparatus in accordance with the invention while the sidewall coverage of the via hole is not significantly affected (resulting in continuous coverage of topological features). As compared to a sputtering process with no collimation, dual collimation in accordance with the invention also reduces encroachment for lift-off structures by a factor of three. The sidewall angle of a metal layer deposited on a lift-off structure with respect to the horizontal plane increases from 100 for no collimation and 160 for long-throw collimation to 320 for dual collimation in accordance with the invention (the exact sidewall angle can be increased or decreased by changing the dual-collimation parameters).
In addition, the full
Heimanson Dorian
Kools Jacques
Moslehi Mehrdad
Paranjpe Ajit
Schwartz Peter
Gray Cary Ware & Freidenrich
McDonald Rodney G.
Veeco Instruments Inc.
LandOfFree
Dual collimated deposition apparatus and method of use does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dual collimated deposition apparatus and method of use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dual collimated deposition apparatus and method of use will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3138900