Apparatus and method for modifying an object

This application claims priority to and is a continuation application of U.S. patent application Ser. No. 11/415,203, filed May 2, 2006, which is a continuation of U.S. patent application Ser. No. 11/047,877, filed Feb. 2, 2005, now U.S. Pat. No. 7,323,699, issued Jan. 29, 2008, the disclosure of which is hereby incorporated by reference in its entirety.

The present invention relates generally to the alteration of material with a relative high degree of volumetric and positional accuracy. More specifically, the present invention relates to the removal and addition of material from substrates and items used in the semiconductor industry such as in the modification of semiconductor wafers and photomasks, which are used in photolithography process, the creation of semiconductors and micro and nano structures. The invention can make substrate alterations with dimensions in the nanometer and larger range and relative to surfaces and surface features with nanometer positional accuracy (X, Y and Z).

In modifying and fabricating wafers, semiconductor die, photomasks and flat panel display/microdisplay devices for the semiconductor industry and other industries as well as correcting defects in masks used for processing of semiconductors, it is sometimes necessary to create small holes and other shapes that are relatively deep compared to their diameter or surface area. It is also sometimes necessary to create small holes and shapes relative to other device features with a high positional accuracy. With regard to holes, high aspect ratio holes are difficult to create. Note that, the ratio of the depth to width is referred to as the aspect ratio.

Attempts to overcome the difficulty associated with high aspect ratio structures have been relatively unsuccessful. Generally, these solutions either bore material out of the sample using particle beams such as ion beams, electron beams or laser beams. For example, U.S. Pat. No. 6,403,388 to Birdsley et al. discloses a method of using ion beams for this purpose. Such beam devices are also used to deposit material on the sample surfaces by introducing gasses into the beam. However, there are distinct disadvantages with these solutions.

U.S. Pat. No. 6,827,979, U.S. Pat. No. 6,635,311 as well as U.S. patent application Ser. No. 10/449,685, U.S. patent application Ser. No. 10/442,188, U.S. patent application Ser. No. 10/465,794, U.S. patent application Ser. No. 10/301,843, U.S. patent application Ser. No. 10/261,663 to Mirkin et al. teach methods of using scanning probe microscopes to add material to objects in small dimensions. These teachings show chemical techniques as the mechanisms for the additive process. These teaching do not include the activation of the additive materials by the use of electromagnetic, particle beam or gaseous materials. The use and apparatus of activation means described by the applicants herein results in substantially more versatility in applicant\'s invention.

U.S. Pat. Nos. 6,737,646 and 6,674,074 to Schwartz disclose adding material to an object by coating a tip and applying that coating to an object with an atomic force microscope. The invention further teaches a chamber for containing gasses. However, the invention has a distinct disadvantage in that at no point is the coating or material activated with an energy device. By including an energy device, the time to add the material to an object is significantly reduced.

When using ion beams to attempt material removal, the ions may imbed themselves in the sample or device to varying depths. As a result, the device becomes unusable because the device properties may be changed by the presence of the imbedded ions. The introduction of gasses into an ion beam also poses additional challenges in containment in and the selection of suitable gasses in the ion beam chamber.

With electron beams, controlling the position of the beam becomes difficult if the sample begins to develop charge. This phenomenon occurs when the electron beam strikes a non-conductive or poorly conductive substrate surface. As a result, the accuracy of this method becomes a serious concern for the end user. The use of such beams can cause uncontrolled damage, which could render the target device unusable. The introduction of gasses into an electron beam also poses challenges in the containment in and the selection of suitable gasses in the electron beam chamber.

With laser light, the size of the hole may be limited by the size of the achievable focus spot. In cases where material modifications smaller than the nominal focus spot are achieved, the depth of removal, and therefore the aspect ratio, is limited Laser light then only becomes a partial solution with limited applications due to the limitations of the focused light beam wavelength.

Additionally, in semiconductor processing and evaluation, physical access to subsurface features may also be needed. A small diameter hole or small area for holes that are not round, is desirable to prevent destruction or damage to features in the device that are adjacent to the hole. None of the prior art solutions are able to achieve this task with a relative degree of accuracy and precision.

Accordingly, a technique that is able to modify a sample such as a semiconductor with high positional accuracy and volumetric control is needed. There is also a need to be able to modify the semiconductor or target device to add material as required by the end user. There is also a need to be able to remove varying levels of materials without greatly affecting adjacent areas. The combination of high aspect ratio features with high positional accuracy, limits the affect to adjacent areas.

The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments permits an object such as semiconductor device to be modified such that material is removed or added. The present invention accomplishes this task by placing a reactant on the device to be modified and subjecting the reactant to a form of energy such that the reactant is able to modify the surface as desired. The reactant is uniquely selected for the desired task based upon the composition of the device. The energy form the mentioned source in the various embodiments of the present invention may be light energy, acoustic energy, or energy in the form of heat. Alternately the energy may be particle beam energy such as electrons, ions or other atomic particles. The reactant may be activated by introducing a gas into the area around the reactant.

The reactant chosen depends on whether the need is to remove material from the sample or whether material is to be added to the sample. The accurate placement of the reactant is typically accomplished with a scanning probe microscope. Scanning probe microscopes are a class of microscopes that use a probe assembly comprising a very fine tip on a probe. The probe assembly is guided in the X, Y, and Z directions using a very accurate positioning mechanism. These microscopes typically make use of some particular interaction between the probe and the surface of a sample. For example, a scanning tunneling microscope places a small bias voltage between the probe tip and the sample. This microscope then detects the currents that flow to or from the tip to the sample. Another type of scanning probe microscope is a scanning force microscope. This microscope utilizes a very sharp tip on the probe assembly. The tip is mounted on a cantilever. Deflections of the cantilever caused by the attractive or repulsive interatomic forces acting on the tip are monitored. Other types of scanning probe microscopes use capacitive or magnetic detection mechanisms. The invention described here typically shows a scanning force microscope, but other types of scanning probe microscopes can function equally well in many of the embodiments described.

In accordance with one embodiment of the present invention, a method for modifying an object includes positioning a reactant on the sample or an object and directing energy towards the reactant, wherein the energy is configured to activate the reactant such that it modifies the sample or object. The reactant is chosen or selected based upon the composition of the sample. The sample can be modified either by removing material or adding material.

In accordance with another embodiment of the present invention, an apparatus for modifying an object includes a reactant that is positioned on the object and an energy device configured to direct its output at the reactant in order to modify the object. This embodiment can further include an assembly that is configured to position the reactant on the object.

In accordance with yet another embodiment of the present invention, a product produced by the process of modifying a sample includes positioning a reactant on the sample and directing and energy source towards the reactant, wherein the energy along with the reactant is configured to modify the sample. The sample is modified by removing material or adding material.

In yet another embodiment of the invention, the reactant, when in fluid state, may be delivered to the surface of a sample by directing or forcing the fluid reactant through a channel formed in the cantilever and tip assembly. U.S. Pat. Nos. 6,337,479 and 6,353,219 to Kley, which are hereby incorporated by reference, describes a fluid delivery system using a channel in the cantilever and tip of a scanning force microscope.