Electric heating – Metal heating – By arc
Reexamination Certificate
2002-12-24
2004-06-08
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06747243
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to surface cleaning, and more particularly, to a method and apparatus for spot cleaning contaminates from a surface of a substrate, such as, a semiconductor wafer used to make electronic components.
2. Description of Related Art
The fabrication of electronic components is very exacting and complex, often requiring a number of processing steps with extreme precision to form the desired circuit pattern on the component substrate. Any contamination on the substrate surface may cause short circuits, open circuits and other defects in the component that can cause the component to fail and/or adversely affect the performance thereof. For example, a single particulate contaminate as small as 100 angstroms in diameter can result in a fatal defect in a modern microcircuit electronic component. Thus, any contamination on the surface of an electronic component has a direct bearing on its process yields, rendering the component less efficient or even inoperable for its intended purpose. Accordingly, cleaning surfaces of the semiconductor substrate is a critical step in manufacturing semiconductor components, such as, integrated circuits, memory chips, thin film heads, flat panel displays, and CD-ROMs.
There are currently numerous methods used to clean substrate surfaces in the electronic industry including both chemical and mechanical cleaning techniques. For example, wet chemical cleaning, dilute or vapor hydrofluoric acid cleaning, megasonic and ultrasonic cleaning, ultraviolet and ozone cleaning, brush cleaning, supercritical fluid cleaning and laser-assisted liquid cleaning are all used to clean particles from a substrate surface. However, as modern semiconductor devices continually decrease in size, each of these cleaning processes is undesirable as each have serious drawbacks requiring the use of cleaning tools and agents that may introduce as many new contaminants to a treated substrate surface as they remove, as will be discussed further below. Furthermore, each of the above cleaning processes also require that the entire surface area of the substrate be treated or cleaned to remove any contaminants thereon, thereby cleaning undesired or uncontaminated areas and even possibly damaging the substrate surface itself.
For example, wet chemical cleaning consists of introducing the entire substrate into a series of baths in aqueous hydrochloric acid (HCl), hydrogen peroxide, and water. Successive lots of wafers introduced into these baths are then exposed to particles from earlier lots thereby potentially depositing thereon and contaminating the surfaces of these subsequent lots of wafers. The dilute hydrofluoric acid cleaning also causes micro-etching of the substrate surface, as well as leads to residual fluorine molecules which can breakdown an oxide in gate stacks and adversely affect other electrical parameters of a chip. Vapor hydrofluoric acid cleaning has been introduced into cluster tool systems, however, these cleaning systems typically lead to residual fluoride, chlorine, and hydride ions on the substrate surfaces, which in turn, lead to degradation of parametric performance or cause problems in downstream processing techniques.
Megasonic and ultrasonic cleaning remove organic films, ionic impurities and contaminate particles from the substrate surface by hydrostatic forces created in combination with the chemical solution. However, both megasonic and ultrasonic cleaning techniques operate on the principal of immersing a substrate in a chemical solution and applying megasonic or ultrasonic devices to impart high energy sonic waves to the components thereby undesirably treating the entire surface area of such components.
The ultraviolet/ozone cleaning processes may cause downstream adhesion processing problems as well as attract unwanted contaminants from any downstream cleaning process. Further, the ultraviolet/ozone cleaning processes have proven not to be effective in the removal of certain contaminants such as, for example, salt, dust, fingerprints, and polymers degraded by ozone. Brush cleaning is also undesirable for cleaning smaller, modern semiconductor devices as it is typically performed with a chemical solution to remove particles as small as 1.0 &mgr;m from the substrate surface whereby the brush, brush material and chemical solutions may damage the substrate surface. Supercritical fluid technology is also undesirable as it consists of using an aerosol gas stream of frozen gas particles directed at the contaminants at a high velocity to “sandblast” the substrate surface for removal of the contaminants there-from. Concerns with the use of this technique include thermal shock to the wafer, sub-surface ion migration, surface structural damage, and electrical parametric damage.
Laser-assisted liquid cleaning is also used to clean substrate surfaces. This cleaning technique entails cleaning a substrate surface with a liquid, such as water or water and alcohol, super-heated using a laser as the heat source. In so doing, the solution penetrates into the interstice between the particle and the substrate surface whereby it is rapidly heated by a pulse from the laser to propel the particle from the substrate. A problem realized by laser-assisted liquid cleaning includes penetrating the solution under metal lines on a patterned substrate whereby the metal lines are lifted off the substrate to not only damage the circuitry itself but also generate particles thereon the surface. Laser-assisted liquid cleaning techniques may also cause ablation effects on a patterned surface. Also, wherein the laser-assisted liquid cleaning technique further includes propelling a stream of gas from a gas source across the surface of the substrate to remove the contaminants, it has been found that damage to the entire surface area of the substrate may result.
Other known methods for cleaning substrate surfaces avoid the use of outside wet solutions such as, for example, surface melting, annealing and ablation. However, these techniques also have their own drawbacks, as discussed further below, as well as treat or clean the entire surface area of the substrate.
Surface melt processes require that the treatment surface be melted to release contaminants which are then removed by ultra high vacuum pressure. This method has the disadvantage that the entire surface being treated must be briefly melted which may be undesirable, as for example when a semiconductor surface is cleaned between deposition of circuit layers and it is desired that the integrity of the previously deposited layers not be disturbed. A further disadvantage with this process is that ultra high vacuum equipment is both expensive and time consuming to operate.
Annealing methods suffer similar drawbacks whereby the crystal structure of the material of the surface being treated is rearranged across the entire surface area and contaminants are removed by ultra high vacuum. With ablation, contaminants on a surface are heated to the point of vaporization, however, it is difficult to vaporize the contaminant without also damaging the underlying treatment surface. Further, surface cleaning by melting, annealing and ablation may be conducted using a laser energy source, however, the use of a laser energy source to remove contaminants from a surface by melting, annealing, or ablation does not overcome the inherent disadvantages of these processes, i.e., the rearrangement and melting of the entire treatment surface.
Still other known cleaning techniques include those that employ momentum transfer as a means to impinge and dislodge the contaminant particles from the substrate surface. For example, pressurized gas or fluid jet spray cleaning removes the contaminants by spraying the substrate surface at predetermined angles, while cryogenic aerosol cleaning, discussed above, uses pressurized frozen particles to “sandblast” the contaminant surfaces. Momentum transfer cleaning techniques are problematic for future generations of smaller semiconductor technology
DeLio & Peterson LLC
Dunn Tom
Johnson Jonathan
Novellus Systems Inc.
Reynolds Kelly M.
LandOfFree
Spot cleaning of particles after inspection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spot cleaning of particles after inspection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spot cleaning of particles after inspection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3360877