Search International and National Patent Collections
Some content of this application is unavailable at the moment.
If this situation persists, please contact us atFeedback&Contact
1. (WO2007008999) LOCALIZED SURFACE ANNEALING OF COMPONENTS FOR SUBSTRATE PROCESSING CHAMBERS
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

LOCALIZED SURFACE ANNEALING OF COMPONENTS
FOR SUBSTRATE PROCESSING CHAMBERS

BACKGROUND

Embodiments of the present invention relate to components for substrate processing chambers.

A substrate processing chamber is used to process a substrate such as for example, a semiconductor wafer or display, in an energized process gas. The processing chamber typically comprises an enclosure wall that encloses a process zone into which a gas is introduced and energized. The chamber may be used to deposit material on the substrate by chemical or physical vapor deposition, etch material from a substrate, implant material on a substrate, or convert substrate layers such as by oxidizing layers or forming nitrides. The chamber typically includes a number of internal chamber components such as for example, a substrate support, gas distributor, gas energizer, and different types of liners and shields. For example, the liners and shields can be cylindrical members surrounding the substrate to serve as focus rings to direct and contain plasma about the substrate, deposition rings that prevent deposition on underlying components or portions of the substrate, substrate shields, and chamber wall liners.

Ceramic materials are often used to form the internal chamber
components, especially those components that are exposed to the energized gas or plasma, and consequently, are subject to high temperatures and erosion. Ceramic materials such as alumina and silica are crystalline whereas silica glasses have no long range order. Ceramics typically exhibit good resistance to erosion by the energized gases, and consequently, do not have to be replaced as often as metal alloys. Ceramic components also reduce the generation of particles in the chamber that result from the erosion of components. Ceramic components can also withstand high temperatures without thermal degradation. Quartz components are particularly useful for plasmas that would corrode other materials, such as plasmas containing fluorine species.

However, ceramic materials are subject to brittle failure modes and often crack or chip in use in the chamber or during handling in the replacement or cleaning of the component. Amorphous and microcrystalline materials are particularly susceptible to brittle failure through crack propagation. In amorphous materials, such as glass, surface microcracks propagate on an atomic level because glass has short-range order without any long-range order. Microcrystalline materials, such as quartz, have grains with surface that can have intragranular microcracks that are through single grains, intergranular microcracks that extend around grains and along grain boundaries, as well as transgranular microcracks that cut across adjacent grains. Of these, the intergranular microcracks that extend around the microcrystalline grains of the quartz are generally the most culpable for crack propagation and often lead to chipping and cracking of the component.

Thus, it is desirable to have a ceramic component made from
microcrystalline or amorphous ceramics that exhibits reduced chipping and cracking. It is further desirable to fabricate such ceramic components with lower failure rates during use. It is also desirable for the ceramic components to be able to withstand the energized gas environment in the chamber without excessive erosion or thermal degradation.

SUMMARY

A substrate processing chamber component has a structural body with localized surface regions having annealed microcracks. The annealed microcracks reduce crack propagation and increase fracture resistance. The structural body of the component is formed, and a laser beam is directed onto localized surface regions of the component for a sufficient time to anneal the surface microcracks. This will result in strengthening of the material and increased life of the component. Suitable lasers include CO2 and argon lasers. The structural body can be made of crystalline ceramic, glass, or glass-ceramic materials, for example, the body can be a ring made from quartz.

DRAWINGS
These features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings, which illustrate examples of the invention. However, it is to be understood that each of the features can be used in the invention in general, not merely in the context of the particular drawings, and the invention includes any combination of these features, where:

FIG. 1 A is a cross-sectional schematic view of a chamber component made from glass showing microcracks in the surface of the glass;

FIG. 1 B is a cross-sectional schematic view of the chamber component of FIG. 1 A after localized laser treatment to anneal the surface microcracks;

FIG. 1C is a cross-sectional schematic view of a chamber component made from quartz showing microcracks along the grains and grain boundary regions of the quartz;

FIG. 1 D is a cross-sectional schematic view of the chamber component of FIG. 2A after localized laser treatment to anneal the surface microcracks;

FIG. 2 is a perspective view of a quartz ring having a laser annealed surface;

FIGS. 3A and 3B are optical microscopy images of a quartz surface with surface microcracks before and after laser treatment, respectively;

FIG. 4 is a schematic view of a laser annealing apparatus suitable for localized surface annealing of the chamber component;

FIG. 5 is a sectional schematic view of a substrate processing chamber that uses the ring of FIG. 2; and

FIG. 6 is a schematic partial sectional side view of support assembly that uses the ring of FIG. 2 in the chamber of FIG. 5.

DESCRIPTION

A substrate processing chamber component 20 comprises a structural body 24 with localized surface regions 26 having microcracks 28, as shown in FIGS. 1A to 1 D. The chamber component 20 can be made from a ceramic, glass or glass ceramic material, such as for example, quartz, silica glass, aluminum oxide, titanium oxide, silicon nitride, zirconium oxide, and other such materials. The surface microcracks 28 are caused by fine dust or other abrasive materials that strike and abrade the component surface 26 during or after fabrication of the component. FIG. 1 A shows a component 20 made from glass, which is amorphous and has short range atomic order but no long range atomic order. For example, silica glass has short range order within individual silica tetrahedrons with fixed silicon and oxygen bond angles, but the silica tetrahedral may be interconnected with random bond angles. In glass, the microcracks are very fine and terminate with atomic bonds. Microcrystalline ceramic materials, as shown in FIG. 1C, are polycrystalline with fine grains 29 having micron sized dimensions. In microcrystalline materials, the microcracks 28 typically extend around the fine grains 29 and or along grain boundaries 31 , but they can also cut across single or adjacent grains 29. The surface microcracks 28 on the components 20 serve as stress concentrators that cause applied forces to concentrate on the tips of the microcracks 20. Because the dimensions of the microcracks 28 are very small, on the level of atomic bonds between atoms of the component material in glass materials, and on the level of micron sized grains in microcrystalline materials, the applied stress is magnified tremendously at the crack tip. This results in rapid catastrophic failure modes in which a portion of the component 20 can easily crack or chip away with even a small applied force or impact.

In one exemplary embodiment, the component 20 comprises a structural body 24 that is shaped as a ring 25, as schematically illustrated in FIG 2. The ring 25 comprises the surface 26 having the microcracks 28. The ring 25 is annular with an internal sidewall 28 and an internal sidewall 30. The internal sidewall 28 faces an internal axis 34 about which the structural body has rotational symmetry. The ring 25 is shaped to protect or conform to a section of a processing chamber, chamber component, or substrate within the chamber. For example, the component 20 can be a liner or shield that is a cylindrical member which is sized to fit around a substrate being processed in a chamber. The shield 20 can be a rig of quartz that surrounds the substrate. The component 20 can also be a deposition ring, shadow ring or cover ring. Yet other chamber components comprise chamber wall liners.

The surface microcracks 28 on the structural body 24 of the component 20 are annealed to heal and close off the microcracks as shown in FIGS 1 B and 1 D, to reduce crack propagation and increase the fracture resistance of the component 20. In one embodiment, a laser beam is directed onto the localized surface regions 26 of the component 20 at a sufficiently high intensity and for a sufficient time to cause the region 26 about the microcracks 28 to soften and heal the microcracks 28. The laser beam is used to selectively heat the localized surface regions of the component 20. The localized surface regions 26 are those that are prone to fracture during use, or which have excessive microcracks during fabrication, for example, regions which are more readily subject to abrasion and grinding from applied external forces during the handling of manufacture of the component. Thus, the localized surface regions may be on the flat top surface of the ring 25. The localized surface regions 26 can also include those regions of the component 20 which are more susceptible to applied stresses during handling and use. For example, the edges 36 of the quartz rings 25 used in the chamber 20 are often chipped or cracked when the ring 25 is removed for cleaning or replacing after use for a predetermined number of process cycles. The edges 36, which may also include corners, are often easily cracked or chipped in use. Thus, increasing the fracture strength of the regions 26 of the quartz ring can significantly increase its process lifetime.

The energy of the laser beam and beam characteristics, such as focal length, beam shape and beam diameter, may be controlled to selectively heat a shallow portion of the localized surface region of the component 20 above the microcrack healing temperature needed for annealing the surface microcracks 28. In one embodiment, a laser beam is used to heat a thin surface layer having a depth of less than 500 microns, and more typically less the 100 microns, of the localized surface regions 26 of a component 20. The focused laser beam selectively heats the localized surface regions 26 of the component 20 to a temperature above the crack healing temperature without excessively raising the bulk temperature of the component, which may result in distortion or thermal fracture of the component 20. After heating the thin surface layer of the component 20, rapid quenching of the hot surface occurs simply by conduction of heat out of the surface into the ambient environment. Since only a very shallow portion of the localized surface region 26 is heated by the laser beam, the quench rate by natural conduction or convection is relatively fast.

While a laser beam heat treatment is described as an exemplary annealing process, other annealing processes can also be used. For example, alternative annealing processes include plasma jet heating, electrical arc heating, flame heating. Thus, the scope of the present invention should not be limited to the exemplary versions described herein, and the invention includes other localized surface annealing processes and apparatus as would be apparent to those of ordinary skill in the art.

The microcrack formation process is essentially partially or entirely reversed by the annealing step. The localized heat energy supplied to the
microcracked surface by the laser causes softening and fluxing of the localized heated region causing the microcracks 28 to close and seal themselves off, as schematically shown in FIGS. 1 B and 1 D. It is believed that in amorphous or glassy materials, as shown in FIGS 1A and 1 B, the microcrack healing process is enhanced because atomic forces acting across the tips of the microcracks 28 tend to pull crack surfaces back into contact across the entire microcrack plane. In microcrystalline materials, as shown in FIGS 1C and 1 D, the grain boundary regions 31 often contain small amounts of impurities that act as fluxing agents causing more rapid fluxing and resultant healing of the microcrack surfaces.

The effects of the laser annealing treatment are shown in FIGS. 3A and 3B, which are optical microscopy images of a quartz surface comprising surface microcracks before and after laser treatment, respectively. FIG. 3A shows the quartz surface with a large number of microcracks corresponding to the dark lines between the lighter grain surface regions. In FIG. 3B, which is a photo of the laser treated sample, it is seen that most of the surface microcracks have disappeared to provide a smooth and continuous surface. Note also that an indentation mark was artificially made at the center of the quartz specimen. However, the size of the indentation mark was on the order of the surface roughness of the quartz material, consequently, it is not visible in the original, un-treated quartz material shown in FIG. 3A. However, the partially healed indentation mark is visible as a faint dark spot in the photo of the laser treated sample of FIG. 3B, because the surface of the laser treated specimen is smooth and absent surface microcracks and roughness.

Annealing of surface microcracks of the chamber components was also found to substantially increase hardness and fracture stress of the annealed material, which would significantly improve its resistance to chipping and cracking. In the hardness test, an increasing load was applied normal to the plane of the specimen surface using a micro-indenter having a known geometrical shape. The load is then reduced until the surface of the specimen partially or completely relaxes, and a depth of indentation is then measured. The load is then progressively increased and the indentation and measurement process repeated until hardness is compromised and the specimen cracks. The Vickers hardness is computed using the formula H = Pmax/ Ac, where Pmax is the maximum load sustained before cracking and Ac is the projected area of contact of the indenter. The hardness was measured using a Nano Hardness Tester. The load applied was on the order of a nano Newton and the displacement was accurately determined using a differential capacitor sensor. Both an original untreated quartz specimen and a laser annealed quartz specimen were measured. The mean Vickers hardness index for the untreated specimen was about 771.68, and the Vickers hardness index for the laser annealed quartz specimen had a mean of 951.68. Thus, the laser annealed quartz specimen had a Vickers hardness which was at least about 10%, and more preferably at least about 25% harder than the untreated specimen.

Another measurement demonstrating increased crack and chip resistance is a fracture stress measurement. Ceramic materials are often tested in a flexural or bending test instead of tensile test because of their brittle nature. The stress at which the ceramic material fails by fracture is called the fracture stress or fracture strength of the material. The fracture stress of untreated and laser annealed quartz specimens were compared from a 4-point bending test performed on the Universal Testing
Machine according to ASTM C1161-90. The load at fracture and a cross-sectional area of the specimen was used to compute the stress fracture from the formula σ = Load/ wxt, where wxt is cross sectional area over which the load is applied. The mean fracture stress of the untreated quartz specimens was 86.23 MPa and the mean fracture stress of the laser annealing quartz specimen was 132.27 MPa. Thus, the mean fracture stress of the laser annealed quartz specimen was at least about 25%, and more preferably, at least about 50% higher than that of the untreated specimen.

Thus, annealing of the microcracks 28 in localized surface regions 26 of a component 20 can significantly increase the surface smoothness, hardness, and fracture strength of the component 20. Absence or reduction of microcracks 28 in the surface of the component 20, especially in regions which are susceptible to applied stresses or are simply more fragile, such as projections, corners and edges of the component, substantially increases the crack and chip resistance of the component 20. Advantageously, surface annealing allows healing and increased strength of selected surface regions 26 without subjecting the entire component 20 to elevated
temperatures that may cause structural deformation or other thermal degradation.
However, the entire component may also be annealed by suitable heat treatment.

Annealing of the microcracks 28 in localized surface regions 26 of the component 20 can be performed using a laser annealing apparatus 50, an exemplary embodiment of which is shown in FIG. 4. The laser annealing apparatus 50 comprises a laser beam enclosure 52 that encloses a laser beam source 54 powered by a power supply 55. Suitable laser beam sources 54 that can be used for microcrack annealing include, for example, Ar (argon), CO2 and KrF lasers. An argon laser transmits in the visible wavelength at about 5145 angstroms. A CO2 laser is an infra-red energy source having a wavelength of 10.6 μm, and can provide beams having a power of the order of 10 kilowatts. The CO2 laser is 100X more efficient than the argon laser and is of greater intensity, allowing much faster scan speeds and larger spot sizes than the argon laser. A CO2laser is described in U.S. Pat. No. 3,702,973 issued on November 14, 1972, which is incorporated herein in its entirety. Yet another type of laser is a KrF excimer laser having a wavelength of about 248 nm, an Eg of 5.0 eV, an efficiency of about 3%, and an output energy of 350 mJ. The laser beam is typically a circular beam having a beam diameter of typically less than about 10 mm, and more typically from about 0.5 mm to about 4 mm. Thus, suitable laser beams can have wavelengths of from about 190 nm to about 10,600 nm. The laser is typically operated at a power level of from about 5 Watts to about 10,000 Watts.

The laser 50 produces a laser beam 56 that is focused at a primary focal point 58 and is re-imaged by a refocusing mirror 62 which provides a larger focal length, to a secondary focal point 64. Between the refocusing mirror 62 and the secondary focal point 64 is the dithering mirror 68 which is connected to a dithering drive motor 72 which vibrates the dithering mirror 68 at a preselected frequency. The dithering drive motor 72 vibrates the dithering mirror 68 about an axis 76 substantially in the plane of the mirror 68 and transverse to the incident laser beam 56 focused by mirror. The dithered beam emanating from the dithering mirror 68 spacially oscillates an arc line which is transverse to the plane of the drawing in FIG. 1.

Typically, the laser beam 56 has an intensity distribution across the beam diameter, also called the intensity profile or intensity shape of the beam, which depends on the type of laser 50. A common beam profile shape is a Gaussian shape, and more typically a U-shaped intensity profile. Focusing of the laser beam changes the cross-sectional size of the beam but not its beam intensity distribution which remains
Gaussian or U-shaped. One method of correcting for the Gaussian or U-shaped cross-section of the laser beam is to spacially oscillate the laser beam 56, also known as dithering. The spacial oscillation of the laser beam 56 may be sinusoidal, sawtooth or square waves. Spacial oscillation or dithering of the laser beam 56 produces an average and more uniform intensity of radiation across the region scanned by the dithering beam. In one embodiment, the laser beam 56 has an approximate Gaussian distribution at its focal point and the spacial oscillation or dithering is sinusoidal. The dithering is produced by the dithering mirror 76 which oscillates back and forth on the axis 76 that is parallel to the plane of the mirror 76 and transverse to the plane of the dither. Typically, the dithered beam covers an area that at least twice as large as the undithered beam. For sinusoidal dithering, the average intensity at each point across the dithering beam projected on the localized surface region is approximately flat in the center region and with peaks at the opposite ends. The resulting intensity profile of the dithering beam is shaped like a square wave and provides a good intensity profile for scanning across the localized surface region in contiguous, overlapping sweeps.

however, other beam shapes, such as sine wave shapes, can also be used with appropriately compensating laser scanning methods.

The dithered beam then passes through a beam width controlling aperture 80 having a controllable or predefined fixed aperature 82 at the second focal point 84. The aperture 80 is located between the dithering mirror 76 and a second focusing system 90 which may be a scanning mirror or lens. The axis 76 of mirror 68 may be transverse or parallel to the plane of the drawing in FIG. 1. The beam is then projected onto a scanning mirror 92 driven by a scanning system 94. The scanning system 94 oscillates the mirror 92 on its axis 96 to sweep and scan the beam 56 back and forth over a selected localized region 100 on the chamber component being treated. The scanned beam passes through a window 102 in the enclosure 100. The sweep rate of scanning mirror 92 is typically slower than the dither frequency of the dithering mirror 68. For example, a focused CO2 laser having a beam diameter of about 500 μm may be scanned at from about 1 mm/sec to about 100 mm/sec.

The scanning system communicates with an X-Y movable stage 110 which is driven by a stage motor 114. The stage 110 can also be adapted to slide in the Z or vertical direction to change the beam width incident on the component. The scanning system 94 synchronizes the sweep rate of the scanning mirror 92 with the movement of the stage 110, and consequently, the movement of the chamber component resting on the stage 110, to uniformly scan the dithered and apertured beam across the component. The scanning parameters are selected to uniformly heat the localized surface region across which the beam is being scanned, by adjusting the scanning speed and pattern to compensate for the shape of the laser beam. For example, the intensity distribution of the beam 56 can contain rings around a central maximum and even a depression in the middle of the beam due to near field annular characteristics of the beam. Furthermore, it is also desirable to overlap the beam scans to compensate for any variation in the cross-sectional intensity of a laser beam - if the laser beam sweeps across the surface in raster-type scans without overlapping of beam scans, the depth of heat treatment may vary across the beam scan depending on the shape of the beam.

The laser beam annealing apparatus 50 further comprises a controller 118 which controls operation of the system and is connected to the power supply 55, which powers the laser 54, the dithering drive motor 72, and the scanning system 94. In addition, the controller 118 accepts input from a user input device 122 and displays input parameters, and scanning system information on a display 122. The controller 118 can be a conventional computer having a central processing unit (CPU) connected to suitable memory devices, including random access memory and storage memory on disk drives, and interface cards and buses. The laser beam annealing apparatus 50 is capable of laser annealing localized surface regions across the component surface with good uniformity over the entire surface region.

A component 20 that is annealed to reduce or heal microcracks can be used in a substrate processing apparatus 200, as schematically illustrated in FIG. 5, which is used to fabricate substrates 215, such as semiconductor wafers and displays. The apparatus 200 can be a MxP, MxP Super E, or eMax type etching chamber, which are from Applied Materials Inc., Santa Clara, California, and are generally described in commonly assigned U.S. Patent Nos. 4,842,683 and 5,215,619 to Cheng et al; and U.S. Patent No. 4,668,338 to Maydan et al, all of which are incorporated herein by reference in their entireties. An exemplary apparatus 200 may be used in a multi-chamber integrated system for processing semiconductor substrates as described in U.S. Patent No. 4,951 ,601 to Maydan et al, which is also incorporated herein by reference in its entirety.

Generally, the apparatus 200 comprises a process chamber 225 and ancillary control, electrical, plumbing and support components. A support assembly 230 comprising a support 238 is provided to receive the substrate 215 in a process zone 235. The support 238 may be an electrostatic chuck 240 comprising a dielectric 45 at least partially covering an electrode 250, and having gas outlets 260 through which a heat transfer gas, such as helium, may be passed from a heat transfer gas source 265 via gas conduits 270, to control the temperature of the substrate 215. Alternatively, the support 38 may be a vacuum or mechanical chuck or any other support as is known in the art. The electrode 250 is electrically charged by an electrode voltage supply 275 to electrostatically hold the substrate 215. A base 280 below the electrostatic chuck 240 may optionally contain a heat exchanger, such as channels through which a heat transfer fluid may be circulated.

Process gas is introduced into the chamber 225 through a gas supply 285 that includes a gas source 290 and one or more gas nozzles 295 terminating in the chamber 225. The gas nozzles 295 may be located around the periphery of the substrate 215 (as shown) or in a showerhead mounted on the ceiling of the chamber (not shown). A gas flow controller 300 is used to control the flow rate of the process gas. Spent process gas and byproducts are exhausted from the chamber 225 through an exhaust system 305. The exhaust system 305 typically comprises an exhaust conduit leading to a plurality of pumps, such as roughing or high vacuum pumps, that evacuate the gas in the chamber 225. A throttle valve 310 is provided in the exhaust conduit to control the pressure of the gas in the chamber 225.

An energized gas, such as for example a gaseous plasma, is generated from the process gas by a gas energizer 275 that couples electromagnetic energy, such as RF or microwave energy, to the process gas in the process zone 235 of the chamber 225. For example, the gas energizer 275 may comprise a first process electrode 315 such as an electrically grounded sidewall or ceiling of the chamber and a second electrode which may be the electrode 250 in dielectric 245. The first and second electrodes 315, 250 are electrically biased relative to one another by an RF voltage provided by an electrode voltage supply 270. The frequency of the RF voltage applied to the electrodes 315, 250 is typically from about 50 KHz to about 60 MHz. In other versions, the gas energizer 275 may also or alternatively include an inductor antenna (not shown) comprising one or more coils to inductively couple RF energy to the chamber 225. The capacitively generated plasma may be enhanced by electron cyclotron resonance in a magnetically enhanced reactor in which a magnetic field generator 320, such as a permanent magnet or electromagnetic coils, provides a magnetic field in the chamber 225 that has a rotating magnetic field having an axis that rotates parallel to the plane of the substrate 215.

The chamber 225 may also comprise one or more process monitoring systems (not shown) to monitor the processes being performed on the substrate 215.

A typical process monitoring system comprises an interferometric system that measures an intensity of light reflected from a layer being proces.sed on the substrate 215, or a plasma emission analysis system that measures a change in light emission intensity of a gas species in the chamber 225. The process monitoring system is useful to detect an endpoint of a process being performed on the substrate 215.

The laser annealed component 20 such as the ring 25 is fitted around the substrate support 238 of the support assembly 230 in the chamber 225. The ring 25 may protect the support assembly 230, for example, the dielectric 245 of the
electrostatic chuck 240 from erosion by preventing contact of the dielectric 245 with the energized process gas in the chamber 225. Alternatively, the ring 25 may have other uses in the support assembly 230.

Referring to FIG. 6, additional structures, such as the collar 210 which surrounds the ring 25 can also be laser annealed to reduce surface microcracks. The collar 210 can be made from a ceramic material such as aluminum oxide or silicon oxide. The collar 210 may serve as a shield, which together with the ring forma replaceable process kit for the chamber. Other annular structures such as chamber wall liners can also be laser annealed, and can also be part of the process kit for the chamber 225.

Although exemplary embodiments of the present invention are shown and described, those of ordinary skill in the art may devise other embodiments which incorporate the present invention, and which are also within the scope of the present invention. For example, the annealed chamber component 20 can be from chamber components such as the ceiling or walls of the chamber 225. In addition, alternative methods of surface annealing can also be used. Furthermore, relative or positional terms shown with respect to the exemplary embodiments are interchangeable.
Therefore, the appended claims should not be limited to the descriptions of the preferred versions, materials, or spatial arrangements described herein to illustrate the invention.