Patent Application
20060196603
The present invention relates generally to semiconductor manufacturing and, more particularly, to top gas baffle and distributor for delivering gases in semiconductor processing chambers.
Chemical vapor deposition (CVD) is a gas reaction process used in the semiconductor industry to form thin layers or films of desired materials on a substrate. Some high density plasma (HDP) enhanced CVD processes use a reactive chemical gas along with physical ion generation through the use of an RF generated plasma to enhance the film deposition by attraction of the positively charged plasma ions onto a negatively biased substrate surface at angles near the vertical to the surface, or at preferred angles to the surface by directional biasing of the substrate surface. One goal in the fabrication of integrated circuits (ICs) is to form very thin, yet uniform films onto substrates, at a high throughput. Many factors, such as the type and geometry of the power source and geometry, the gas distribution system and related exhaust, substrate heating and cooling, chamber construction, design, and symmetry, composition and temperature control of chamber surfaces, and material build up in the chamber, must be taken into consideration when evaluating a process system as well as a process which is performed by the system.
Uneven gas distribution is one problem encountered in semiconductor fabrication, which affects deposition uniformity. In one known chamber configuration, a gas plenum is provided around the perimeter of a processing region and a plurality of nozzles extend radially inwardly to provide gases to the substrate surface. A challenge in such a design is to evenly distribute gases across the substrate surface so that more gas is not provided towards the edge of the substrate than towards the center of the substrate. A top gas nozzle, positioned directly above the substrate support member, can be used to improve deposition uniformity.
Despite the improvements obtainable by using of a top gas nozzle further improvements and/or alternative techniques are desirable for increasing uniformity of gas distribution on the surface of a substrate.
The present invention provides techniques including a method of introducing a gas into a chamber and an apparatus for processing semiconductors. More particularly, embodiments of the present invention are directed to increasing uniformity of a process gas onto a substrate in a semiconductor processing chamber.
In one embodiment of the present invention, a gas distributor includes a body having an upper surface adapted to outwardly direct gas away from the body and a lower surface opposite the upper surface. The lower surface has central portion and a recessed peripheral portion separated from the central portion by a step surface. The body further including a gas inlet, a plurality of gas outlets disposed in the step surface and a gas passage connecting the inlet to the plurality of gas outlets.
In yet another embodiment of the present invention, a substrate processing chamber includes an enclosure having a ceiling and a sidewall and a substrate support capable of supporting a substrate. A gas distributor is positioned centrally above the substrate support. The gas distributor comprising a body including a baffle having an upper surface adapted to outwardly direct gas away from the body and towards the enclosure sidewall, and a lower surface opposite the upper surface and spaced apart from the substrate support. The lower surface has a central portion and a recessed peripheral portion separated from the central portion by a step surface. The body further includes a gas inlet, a plurality of gas outlets disposed in the step surface, and a gas passage connecting the inlet to the plurality of gas outlets.
The present invention provides techniques including a method of introducing a gas into a chamber and an apparatus for processing semiconductors. More particularly, embodiments of the present invention are directed to increasing uniformity of a process gas onto a substrate in a semiconductor processing chamber.
Gas distributor 200 has a gas deflecting surface 202 and a gas distributor face 204. Gas deflecting surface 202 provides a pathway for cleaning gases during a chamber clean process. Cleaning gases are directed to the chamber walls instead of a substrate support member (not shown) located directly below the gas distributor. The gas distributor 200 is connected to a chamber wall at a proximal portion 206. During a CVD process, a deposition gas is supplied to the gas distributor 200 at the proximal end 208. This deposition gas flows through gas distributor 200, exiting at apertures 210, and onto a substrate position on the substrate support member.
As illustrated in
In specific embodiments, gas distributor 200 can have 4, 6, 8, or more apertures 210. These apertures 210 are evenly distributed along the circumference of step 212 or, alternatively, weighted to a particular portion thereof. The placement and number of apertures 210 can be tuned for a specific application to achieve uniform distribution of deposition gas unto the substrate. Likewise, the diameter of apertures 210 can also be tuned. The diameter can be in the range of about 0.005 inches to about 0.250 inches. In a specific embodiment, the diameter of apertures 210 are 0.060 inches.
The upper portion of chamber 813 includes a dome 814, which is made of a ceramic dielectric material, such as aluminum oxide or aluminum nitride, sapphire, SiC or quartz. A heater plate 823 and a cold plate 824 surmount, and are thermally coupled to, dome 814. Heater plate 823 and cold plate 824 allow control of the dome temperature to within about ±10° C. over a range of about 100° C. to 200° C. Dome 814 defines an upper boundary of a plasma processing region 816. Plasma processing region 816 is bounded on the bottom by the upper surface of a substrate 817 and a substrate support member 818.
The lower portion of chamber 813 includes a body member 822, which joins the chamber to the vacuum system. A base portion 821 of substrate support member 818 is mounted on, and forms a continuous inner surface with, body member 822. Substrates are transferred into and out of chamber 813 by a robot blade (not shown) through an insertion/removal opening (not shown) in the side of chamber 813. Lift pins (not shown) are raised and then lowered under the control of a motor (also not shown) to move the substrate from the robot blade at an upper loading position 857 to a lower processing position 856 in which the substrate is placed on a substrate receiving portion 819 of substrate support member 818. Substrate receiving portion 819 includes an electrostatic chuck 820 that secures the substrate to substrate support member 818 during substrate processing. In a preferred embodiment, substrate support member 818 is made from an aluminum oxide or aluminum ceramic material.
Vacuum system 870 includes throttle body 825, which houses twin-blade throttle valve 826 and is attached to gate valve 827 and turbo-molecular pump 828. It should be noted that throttle body 825 offers minimum obstruction to gas flow, and allows symmetric pumping. Gate valve 827 can isolate pump 828 from throttle body 825, and can also control chamber pressure by restricting the exhaust flow capacity when throttle valve 826 is fully open. The arrangement-of the throttle valve, gate valve, and turbo-molecular pump allow accurate and stable control of chamber pressures from between about 1 millitorr to about 2 torr.
A gas delivery system 833 provides gases from several sources, 834A-834E chamber for processing the substrate via gas delivery lines 838 (only some of which are shown). As would be understood by a person of skill in the art, the actual sources used for sources 834A-834E and the actual connection of delivery lines 838 to chamber 813 varies depending on the deposition and cleaning processes executed within chamber 813. Gases are introduced into chamber 813 through a gas ring 837 and/or a gas distributor 811.
In one embodiment, first and second gas sources, 834A and 834B, and first and second gas flow controllers, 835A′ and 835B′, provide gas to ring plenum in gas ring 837 via gas delivery lines 838 (only some of which are shown). Gas ring 837 has a plurality of source gas nozzles 839 (only one of which is shown for purposes of illustration) that provide a uniform flow of gas over the substrate. Nozzle length and nozzle angle may be changed to allow tailoring of the uniformity profile and gas utilization efficiency for a particular process within an individual chamber. In a preferred embodiment, gas ring 837 has 12 source gas nozzles made from an aluminum oxide ceramic.
Gas ring 837 also has a plurality of oxidizer gas nozzles 840 (only one of which is shown), which in a preferred embodiment are co-planar with and shorter than source gas nozzles 839, and in one embodiment receive gas from body plenum. In some embodiments it is desirable not to mix source gases and oxidizer gases before injecting the gases into chamber 813. In other embodiments, oxidizer gas and source gas may be mixed prior to injecting the gases into chamber 813 by providing apertures (not shown) between body plenum and gas ring plenum. In one embodiment, third, fourth, and fifth gas sources, 834C, 834D, and 834D′, and third and fourth gas flow controllers, 835C and 835D′, provide gas to body plenum via gas delivery lines 838. Additional valves, such as 843B (other valves not shown), may shut off gas from the flow controllers to the chamber.
In embodiments where flammable, toxic, or corrosive gases are used, it may be desirable to eliminate gas remaining in the gas delivery lines after a deposition. This may be accomplished using a 3-way valve, such as valve 843B, to isolate chamber 813 from delivery line 838A and to vent delivery line 838A to vacuum foreline 844, for example. As shown in
Referring again to
System controller 860 controls the operation of system 810. In a preferred embodiment, controller 860 includes a memory 862, such as a hard disk drive, a floppy disk drive (not shown), and a card rack (not shown) coupled to a processor 861. The card rack may contain a single-board computer (SBC) (not shown), analog and digital input/output boards (not shown), interface boards (not shown), and stepper motor controller boards (not shown). The system controller conforms to the Versa Modular European (“VME”) standard, which defines board, card cage, and connector dimensions and types. The VME standard also defines the bus structure as having a 16-bit data bus and 24-bit address bus. System controller 860 operates under the control of a computer program stored on the hard disk drive or through other computer programs, such as programs stored on a removable disk. The computer program dictates, for example, the timing, mixture of gases, RF power levels and other parameters of a particular process. The interface between a user and the system controller is via a monitor, such as a cathode ray tube (“CRT”), and a light pen.
The above-described arrangements of apparatus and methods are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.
