CMP gadget is employed primarily for polishing the entrance experience or perhaps gadget edge of an semiconductor wafer throughout the fabrication associated with semiconductor systems around the wafer. A wafer is definitely planarized as well as smoothed one or more times throughout the fabrication process in order to the best surface associated with the wafer for being while flat since possible. A wafer is definitely refined when you are placed on some sort of service provider and pressed confront decrease onto a polishing pad protected having a slurry of colloidal silica or even alumina with de-ionized water.
A polishing pad is usually created with a couple of levels overlying your platen with the a smaller amount long lasting core for the reason that external core in the pad. The tiers can be made of polyurethane and will contain a filler to get avoiding the actual dimensional solidity belonging to the layers. A polishing cushion is often several instances your diameter of your wafer as well as wafer can be saved off direct attention to the actual station to counteract polishing a non-planar surface against the particular wafer. The wafer is rotated to forestall polishing a taper into the wafer. Although the axis regarding rotation with the wafer in addition to this axis of rotation of the cushion may not be collinear, the axes need to be parallel.
The platens employed for the polishing sleep pad and to get a polishing head will be meticulously machined to provide optically flat, parallel surfaces. The sturdy levels over a polishing pad usually are assumed to supply a homogeneous pressure on a wafer. It will be believed that assumption was in mistake then one aspect from the invention contact the matter connected with distortion around the polishing pad.
Polishing scalps should meet somewhat disagreeing specifications for easily use in CMP apparatus. The wafer should be strongly used although not harmed or even contaminated. Polishing scalps of the prior art work typically utilize a wax-like materials to install the wafer temporarily to the carrier. The wax should be entirely easily-removed as well as cannot change your silicon to help that that is actually attached. The polishing head can not be so inflexible that this wafer is definitely chipped or ruined if your wafer engages your polishing pad as well as the head.
Gill, Jr. et al. U.S. Pat. No. 4,141,180 discloses a polishing head attached to a vertical shaft with a basketball plus socket combined to permit restricted action of the brain to support versions inside thick of the wafer. The wafer provider is usually covered that has a felt-like substance and the wafer will be used resistant to the nap exterior by just a vacuum cleaner combined towards back again with the wafer through a plurality of holes around the actual carrier. The polishing travel consists of your plastic material band encircling that wafer to locate the particular wafer radially by using respect that will the particular directory shaft.
Shendon et al. U.S. Pat. No. 5,205,082 discloses a polishing head as well as a new flexible diaphragm emotionally involved with a wafer service and also to a retaining ring. Air strain upon just one facet belonging to the diaphragm can be above ambient force as well as air pressure about the wafer area on the diaphragm reaches background pressure. The pressure using a wafer is usually non-uniform thanks to aids from deflection regarding the diaphragm itself. Vertical action from the tote can be constrained by the flange engaging a good resetting bolt, which must always be loosened in order to lessen your carrier. A Cwasher is usually detailed for facilitating this adjustment.
The holding onto engagement ring encircling a wafer in a very polishing mind belonging to the previous art work features an inside diameter slightly large versus diameter from the wafer and also there is always a bit of a gap between the wafer as well as the ring. Whether the ring presses versus the tough polishing station and also not, there is certainly unavoidably an annular location around the periphery belonging to the wafer the place that the polishing isn't uniform, known inside art when ;edge exclusion. Edge exclusion from the preceding art work is commonly 5-10 mm. wide plus lessens the area of that wafer from which fine perish is usually obtained.
It can be regarded while in the art work of which uniformity in wafer polishing can be a operate with pressure, velocity, as well as focus of chemicals. Edge exclusion can be caused, around part, through non-uniform stress with a wafer. The past art efforts in order to resolve the condition simply by contacting your polishing station considering the retaining ring, e.g. as unveiled within the Shendon et al. patent, nevertheless the challenge remains.
Another part with the dilemma connected with uniformity will be the distribution from the slurry. As some sort of wafer is polished, substance by-products locally switch the particular composition, pH, particle size, as well as uniformity belonging to the slurry. In the earlier art, this particular challenge was addressed by thoroughly incorporating that slurry and also by controlling the rate with stream towards polishing pad; specifically, by simply furnishing a satisfactory stream to counteract large, local alterations around composition, particle size, or perhaps pH. Even so, edge exclusion stays a problem.
The foregoing objects tend to be attained by this kind of new technology where your polishing scalp includes a service provider denture owning concentric, integral, cylindrical walls, a great annular piston appropriate while in the outer belonging to the cylindrical surfaces including a second piston appropriate in the inner cylindrical wall membrane plus engaging your annular piston. Each piston defines some sort of chamber using the provider denture plus this chambers tend to be isolated coming from the other person by just a seal. Pneumatic fittings source surroundings or vacuum cleaner to every single chamber. The subsequent piston comprises a cylindrical area wall structure plus an integral base plate. The underside dish is thicker from the center than at along side it wall and also the underside of the plate can be dealt with with a wafer working layer. A retaining engagement ring can be emotionally involved with your lower advantage of the annular piston. In accordance using one more aspect of the invention, the actual retaining band has a peripheral groove for removing a good outwardly stretching flange through the primary body in the ring. In compliance with a more part with the invention, the actual underside belonging to the keeping wedding ring comprises of more than one spiral grooves regarding distributing slurry concerning a wafer during polishing.
Read more useful about Pneumatic system
No comments:
Post a Comment