Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2000-09-05
2004-05-18
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S299000, C700S304000
Reexamination Certificate
active
06738683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of silicon wafer fabrication equipment useful in the manufacture of semiconductor devices. Particularly, the present invention relates to an epitaxial growing apparatus and method for growing an epitaxial thin film layer of a semiconductor substance on a substrate mounted on a support member which is heated by high frequency energy or infrared radiation ray in a gas-tight reaction chamber. More particularly, the present invention relates to an epitaxial growing apparatus and method for controlling the operation of an epitaxial reactor. Yet more particularly, the present invention relates to an epitaxial growing apparatus and method for controlling the operation of an epitaxial reactor that includes a method and apparatus to provide a controlled high etch procedure for cleaning the epitaxial reaction chamber.
2. Description of the Prior Art
Epitaxy is the oriented crystalline growth between two crystalline solid surfaces. More typically, epitaxy refers to the growth of a crystalline layer upon a crystalline substrate. One common technique for epitaxial growth is chemical vapor deposition (CVD). In the microelectronics industry, for example, crystalline silicon is epitaxially grown upon silicon wafer substrates in a heated reactor. The reactors are called epitaxial reactors.
A conventional epitaxial reactor is a barrel reactor having a CVD chamber in which a barrel-like holder or susceptor is mounted so as to rotate about its vertical axis. Semiconductor wafers are placed in recessed pockets defined by the susceptor. The susceptor holds the wafers in a manner that permits the wafers to have maximum surface area exposure to the chemical vapor while utilizing the force of gravity to retain the wafers within the pockets. A barrel reactor also has gas inlets near the top of the CVD chamber and an exhaust port near the bottom of the CVD chamber such that gas entering the chamber generally flows downwardly over the wafers prior to exiting the chamber by way of the exhaust port. An array of heat lamps is arrayed around the CVD chamber. The radiant energy produced heats the susceptor to the required processing temperature for depositing the desired material. A cooling airflow path extends from a blower through a tapered input duct to a large plenum chamber that coaxially surrounds and extends over the top of the CVD chamber. From this plenum chamber cooling air flows coaxially downward over the surface of the quartz bell jar which forms the CVD chamber and radially inward through the banks of radiant heater lamps surrounding the bell jar.
U.S. Pat. No. 5,288,364 (1994, Burt et al.) discloses an epitaxial reactor that includes a bell jar in which the epitaxial depositions are performed. During an epitaxial deposition cycle, an infrared detector monitors the temperature of the bell jar. After the temperature reaches a predetermined value, initiation of further epitaxial deposition cycles is inhibited.
U.S. Pat. No. 5,279,986 (1994, Maloney et al.) discloses a method of processing a semiconductor substrate for depositing an epitaxial layer by chemical vapor deposition in an epitaxial reactor that includes a cooling air flow path extending from a blower through a tapered input duct to a large plenum chamber. The plenum chamber extends over the top of the deposition apparatus. From the plenum chamber cooling air flows coaxially downward over the surface of the quartz bell jar which forms the reaction chamber and radially inward through the banks of radiant heater lamps coaxially surrounding the bell jar.
U.S. Pat. No. 5,160,454 (1992, Maloney et al.) discloses an epitaxial layer by chemical vapor deposition in an epitaxial reactor that includes a cooling air flow path extending from a blower through a tapered input duct to a large plenum chamber. The plenum chamber extends over the top of the deposition apparatus. From the plenum chamber cooling air flows coaxially downward over the surface of the quartz bell jar which forms the reaction chamber and radially inward through the banks of radiant heater lamps coaxially surrounding the bell jar.
U.S. Pat. No. 5,152,842 (1992, Urata et al.) discloses a reactor for epitaxial growth where a susceptor on which semiconductor wafers are placed is heated by a heater. The susceptor is rotated around a vertically provided gas feed pipe in a bell jar. The gas introduced into the bell jar through the gas feed pipe is decomposed to deposit a crystalline semiconductor material on the wafers. The wafers are positioned in pockets of the susceptor and the pockets are arranged on the uniform temperature region of the susceptor.
U.S. Pat. No. 4,858,557 (1989, Pozzetti et al.) discloses a reactor for chemical vapor deposition of epitaxial layers on crystalline substrates using a medium frequency heating system. The power for the heating is produced by a multi-turn coil, inducing electrical currents in a susceptor of electrically conductive material housed in a transparent bell jar. The internal sides of the turns of the coil are optically finished to reflect back heat to the susceptor irradiated by the coil during operation. Heating is controlled by subtracting or adding reactive currents from or to different turns of the coil and through properly shaping the walls of the susceptor in order to control temperature gradients within.
During normal operation of the epitaxial reactor, the deposited silicon coats certain internal parts of the reactor used to hold the silicon wafers. When this deposit reaches a certain thickness, it must be removed before it can begin to ablate off and cause contamination in the form of solid phase silicon particles. These particles will cause defects in the silicon film deposited on subsequent silicon wafers processed through the reactor.
In all chemical vapor deposition epitaxial reactors, silicon is allowed to accumulate on the susceptor in order to assist in forming a uniform epitaxial layer thickness on each of the wafers. Unfortunately, some of the silicon accumulates onto the inside surface of the bell jar developing a haze. Silicon is periodically removed from the susceptor by a procedure commonly referred to as a high rate etch. In order to remove this deposited silicon from the susceptor, the reactor is heated to a high temperature in the presence of a reactant gas. Typically the temperature is in the range of about 1,100 degrees Celsius to about 1,300 degrees Celsius, and the reactant gas is a high percent molar volume of hydrogen chloride gas. Once the reaction chamber reaches the required high temperature, the reactant gas is introduced into the chamber. The gas etches the deposited silicon from the susceptor and is removed from the chamber through an exhaust port. All other surfaces of the reaction chamber do not reach a sufficient temperature for this reaction to occur. Consequently, after repeatedly performing deposition cycles followed by a high etch operation, the bell jar must eventually be removed and cleaned with a wet etch.
A disadvantage of doing a wet etch is the number of hours the reactor is unavailable for producing wafers. Also, each time the reactor is opened for wet etch cleaning, the useable life of the reactor's lamps and seals is reduced. This increases the reactor's operating costs and increases the wafer's manufacturing costs.
Therefore what is needed is an epitaxial cleaning apparatus and method that extends the number of deposition-etch sequences. What is further needed is an epitaxial cleaning apparatus and method that extends the number of deposition-etch sequences by controlling the cooling air that passes over the bell jar. What is still further needed is an epitaxial cleaning apparatus and method that extends the number of deposition-etch sequences by reducing the air flow of the cooling air that passes over the bell jar thereby allowing the temperature of the jar to increase during a high etch procedure causing the haze to be substantially removed. What is also further neede
CXE Equipment Services, LLC
Deleault, Esq. Robert R.
Mesmer & Deleault, PLLC
Picard Leo
Rapp Chad
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