Abstract: A method and apparatus for controlling the diameter of a monocrystalline ingot as it is being pulled from a melt by changing the temperature of the melt. The ingot is pulled from the melt at a target rate that substantially follows a predetermined velocity profile. A temperature model represents variations in the melt temperature in response to variations in power supplied to a heater for heating the melt. In generating a temperature set point representing a target melt temperature, an error between a target diameter and a measured diameter of the ingot is determined and proportional-integral-derivative (PID) control is performed on the error signal. The PID control generates the temperature set point as a function of the error signal. In turn, the temperature model determines a power set point for the power supplied to the heater as a function of the temperature set point generated by the PID control and the power supplied to the heater is adjusted according to the power set point.

Abstract: The present invention is directed to a process for preparing single crystal silicon, in ingot or wafer form, wherein crucible rotation is utilized to control the average axial temperature gradient in the crystal, G0, as a function of radius (i.e., G0(r)), particularly at or near the central axis. Additionally, crucible rotation modulation is utilized to obtain an axially uniform oxygen content therein.

Abstract: A crystal puller for growing monocrystalline ingots includes a side heater adjacent a crucible for heating the crucible and a melt heat exchanger sized and shaped for surrounding the ingot and disposed adjacent a surface of the melt. The heat exchanger includes a heat source having an area for radiating heat to the melt for controlling heat transfer at the upper surface of the melt. The melt heat exchanger is adapted to reduce heat loss at the exposed upper surface portion. Methods for growing single crystal silicon crystals having desired defect characteristics are disclosed.

Abstract: A process for controlling the amount of insoluble gas trapped by a silicon melt is disclosed. Polycrystalline silicon is charged to a crucible in a crystal pulling apparatus and the apparatus sealed and evacuated. After evacuation, the crystal pulling apparatus is backfilled at least once with a gas having a high solubility in silicon, such as nitrogen. The highly soluble gas fills in cavities between the polycrystalline silicon pieces and between the pieces and the crucible such that when the silicon is melted and bubbles form in the molten silicon the bubbles will solubilize into the melt instead of becoming entrapped in the growing crystal.

Abstract: A process for etching silicon wafers using a caustic etchant in the form of an aqueous solution comprising water and a source of hydroxide ions and generally characterized by a lower concentration of water and/or higher concentration of source of hydroxide ions. In accordance with another embodiment, the caustic etchant includes a salt additive. The process produces silicon wafers with improved surface characteristics such as flatness and nanotopography.

Abstract: A process for manufacturing silicon wafers that reduces the size of silicon wafer surface and/or sub-surface defects without the forming excessive haze. The process entails cleaning the front surface of the silicon wafer at a temperature of at least about 1100° C. by exposing the front surface to a cleaning ambient comprising H2, HF gas, or HCl gas to remove silicon oxide from the front surface and exposing the cleaned front surface of the silicon wafer at a temperature of at least about 1100° C. to a vacuum or an annealing ambient consisting essentially of a mono-atomic noble gas selected from the group consisting of He, Ne, Ar, Kr, and Xe to facilitate the migration of silicon atoms to the exposed agglomerated defects without substantially etching silicon from the front surface of the heated silicon wafer.

Abstract: A thermal annealing process for producing a low defect density single crystal silicon wafer. The process includes thermally annealing a wafer having a first axially symmetric region which extends radially inwardly from the circumferential edge, contains silicon self-interstitials as the predominant intrinsic point defect and is substantially free of agglomerated interstitial defects and a second axially symmetric region which has vacancies as the predominant intrinsic point defect. The wafer is subjected to a thermal anneal at a temperature in excess of about 1000° C. in an atmosphere of hydrogen, argon or a mixture thereof to dissolve agglomerated vacancy defects present in the second axially symmetric region within a layer extending from the front side toward the central plane.

Abstract: The present invention relates to single crystal silicon, in ingot or wafer form, which contains an axially symmetric region which is free of agglomerated intrinsic point defects, and a process for the preparation thereof.

Abstract: A control method for use with a crystal puller for growing a monocrystalline semiconductor crystal from a melt according to the Czochralski process. The method includes defining an initial interval of time for observing growth of the crystal being pulled from the melt and determining diameter variations occurring during the interval. Based on the variations in the crystal diameter, the method defines a function r(t). By performing a best fit routine on the function r(t), the method deduces current values of crystal radius rf, meniscus height hf and growth rate Vgf at the end of the observation interval. The method also includes determining pull rate and heater power parameters as a function of the growth rate to control the crystal puller to minimize variations in both crystal diameter and growth rate during subsequent growth of the crystal.

Abstract: The present invention relates to single crystal silicon, in ingot or wafer form, which contains an axially symmetric region which is free of agglomerated intrinsic point defects, and a process for the preparation thereof. The process comprises controlling growth conditions, such as growth velocity, v, instantaneous axial temperature gradient, G0, and the cooling rate, within a range of temperatures at which silicon self-interstitials are mobile, in order to prevent the formation of these agglomerated defects. In ingot form, the axially symmetric region has a width, as measured from the circumferential edge of the ingot radially toward the central axis, which is at least about 30% the length of the radius of the ingot. The axially symmetric region additionally has a length, as measured along the central axis, which is at least about 20% the length of the constant diameter portion of the ingot.

Abstract: A wafer polishing apparatus for polishing a semiconductor wafer. The polisher comprises a base, a turntable, a polishing pad and a head drive mechanism for driven rotation of a polishing head. The polishing head comprises a sealing ring adapted to hold at least one wafer for engaging a front surface of the wafer with a work surface of the polishing pad. The sealing ring allows for application of uniform air pressure over the rear surface of the wafer. The sealing ring is constructed so that the wafer itself defines a portion of a pressure cavity receiving pressurized air.

Abstract: A process for heat-treating a single crystal silicon wafer to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step. The wafer has a bulk layer between front and back surface layers. The wafer is subjected to a heat-treatment in an atmosphere to form crystal lattice vacancies. A surface of the wafer is oxidized by heating in the presence of an oxygen-containing atmosphere to effect the vacancy concentration profile. The wafer is cooled at a rate which allows some, but not all, the crystal lattice vacancies to diffuse to the surfaces such that the concentration of vacancies in the bulk layer is greater than in the surface layers. The vacancy concentration profile shape is determined in part by the heat-treatment atmosphere, in part by the surface oxidation, and in part by the cooling rate.

Abstract: A heat shield assembly is disclosed for use in a crystal puller for growing a monocrystalline ingot from molten semiconductor source material. The heat shield assembly has a central opening sized and shaped for surrounding the ingot as the ingot is pulled from the molten source material. In one aspect, the heat shield assembly includes a multi-sectioned outer shield and a multi-sectioned inner shield. The sections of at least one of the inner and outer shields may be releasably connected to one another so that, in the event a section is damaged, the sections may be separated to allow replacement with an undamaged section. In another aspect the heat shield assembly includes an upper section and a lower section extending generally downward from the upper section toward the molten material. The lower section has a height equal to at least about 33% of a height of the heat shield assembly.

Abstract: A method of manufacturing a semiconductor wafer includes providing an ingot of semiconductor material, slicing the wafer from the ingot, and processing the wafer to increase parallelism of the front surface and the back surface. A final polishing operation on at least the front surface is performed by positioning the wafer between a first pad and a second pad and obtaining motion of the front and back surfaces of the wafer relative to the first and second pads to maintain parallelism of the front and back surfaces and to produce a finish on at least the front surface of the wafer so that the front surface is prepared for integrated circuit fabrication. In another aspect, the wafer is rinsed by a rinsing fluid to increase hydrodynamic lubrication. Other methods are directed to conditioning the polishing pad and to handling wafers after polishing. An apparatus for polishing wafers is also included.

Abstract: The present invention relates to a process for the treatment of a Czochralski single crystal silicon wafer having at least a portion of which is vacancy dominated to dissolve existing oxygen clusters and precipitates, while preventing their formation upon a subsequent oxygen precipitation heat treatment. The process comprises (i) heat-treating the wafer in a rapid thermal annealer at a temperature of at least 1150° C. in an atmosphere having an oxygen concentration of at least 1000 ppma, or alternatively (ii) heat-treating the wafer in a rapid thermal annealer at a temperature of at least about 1150° C. and then controlling the rate of cooling from the maximum temperature achieved during the heat-treatment through a temperature range in which vacancies are relatively mobile in order to reduce the number density of vacancies in the single crystal silicon to a value such that oxygen precipitates will not form if the wafer is subsequently subjected to an oxygen precipitation heat-treatment.

Abstract: A method for polishing front and back surfaces of a semiconductor wafer includes the step of providing a polishing apparatus having a wafer carrier generally disposed between a first polishing pad and a second polishing pad. The first pad has a hardness significantly greater than a hardness of the second pad. The wafer is placed in the wafer carrier so that the front surface faces the first pad and so that the back surface faces the second pad. A polishing slurry is applied to at least one of the pads and the carrier, first pad and second pad are rotated. The front surface is brought into contact with the first pad and the back surface is brought into contact with the second pad for polishing the front and back surfaces of the wafer whereby less wafer material is removed from the back surface engaged by the second pad and the back surface has less gloss than the front surface after polishing so that the front surface and back surface are visually distinguishable.

Abstract: The present invention is directed to a process for producing a silicon wafer which, during the heat treatment cycles of essentially any arbitrary electronic device manufacturing process, may form an ideal, non-uniform depth distribution of oxygen precipitates and may additionally contain an axially symmetric region which is substantially free of agglomerated intrinsic point defects. The process including growing a single crystal silicon ingot from molten silicon, and as part of the growth process, controlling (i) a growth velocity, v, (ii) an average axial temperature gradient, G0, during the growth of a constant diameter portion of the crystal over a temperature range from solidification to a temperature of no less than about 1325° C., and (iii) a cooling rate of the crystal from a solidification temperature to about 1,050° C., in order to cause the formation of an axially symmetrical segment which is substantially free of agglomerated intrinsic point defects.

Abstract: The present invention relates to a process for growing a single crystal silicon ingot which contains an axially symmetric region which is substantially free of agglomerated intrinsic point defects. The process comprises (i) forming a region within the constant diameter portion in which vacancies are the predominant intrinsic point defect; (ii) heating the lateral surface of the ingot to cause a thermally induced inward flux of silicon self interstitial atoms into the region from the heated surface which reduces the concentration of vacancies in the region; and (iii) maintaining the temperature of the region in excess of the temperature, TA, at which agglomeration of vacancy point defects into agglomerated defects occurs during the period of time between the formation of the region and the reduction of the concentration of vacancies in the region.

Abstract: A process for heat-treating a single crystal silicon wafer to dissolve agglomerated vacancy defects and to influence the precipitation behavior of oxygen in the wafer in a subsequent thermal processing step. The process includes subjecting the wafer to a heat treatment to dissolve agglomerated vacancy defects, rapid thermally annealing the heat-treated wafer to cause the formation of crystal lattice vacancies throughout the wafer and controlling the cooling rate of the annealed wafer to allow some, but not all, of the crystal lattice vacancies to diffuse to the front surface to produce a wafer having a nonuniform vacancy concentration with the concentration of vacancies in the bulk of the wafer being greater than the concentration in the surface layer.

Abstract: A process for producing silicon which is substantially free of agglomerated intrinsic point defects in an ingot having a vacancy dominated region. An ingot is grown generally in accordance with the Czochralski method. While intrinsic point defects diffuse from or are annihilated within the ingot, at least a portion of the ingot is maintained above a temperature TA at which intrinsic point defects agglomerate. The achievement of defect free silicon is thus substantially decoupled from process parameters, such as pull rate, and system parameters, such as axial temperature gradient in the ingot.