Methods of removing material from a semiconductor substrate

The invention encompasses a method of removing at least some of a material from a semiconductor substrate. A feed gas is fed through an ozone generator to generate ozone. The feed gas comprises at least 99.999% O2 (by volume). The ozone, or a fragment of the ozone, is contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate. The invention also encompasses another method of removing at least some of a material from a semiconductor substrate. A mixture of ozone and organic solvent vapors is formed in a reaction chamber. At least some of the ozone and solvent vapors are contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate.

TECHNICAL FIELD

The invention pertains to methods of forming and utilizing ozone to remove at least some of a material from a semiconductor substrate. In particular applications, the invention pertains to methods of utilizing organic material vapors in combination with ozone to remove materials from semiconductor substrates.

BACKGROUND OF THE INVENTION

It is common to utilize ozone for removing materials from over semiconductor substrates during semiconductor device fabrication. For instance, ozone can be utilized for removing photoresist and other organic materials. The ozone is typically generated proximate to, or within, a reaction chamber. The semiconductor substrate is provided within the reaction chamber, and the ozone is contacted with the material which is to be removed.

Ozone can be utilized for removing organic materials, such as, for example, photoresist, in that the ozone can oxidize the organic material and thereby convert the organic material to a form which is more readily removed from over a semiconductor substrate than was the organic material prior to oxidation.

A method of forming ozone is to feed a diatomic oxygen (O2) containing feed gas into an ozone generator. The feed gas is generally about 99.9% O2(by volume), with the remaining 0.1% of the feed gas comprising mostly nitrogen (N2). Occasionally, additional nitrogen may be spiked into the feed gas to raise a concentration of nitrogen up to about 5%. A reason for utilizing the relatively low purity oxygen as a feed gas for generating ozone is that it can be cheaper than higher purity oxygen. Another reason is that there can be a reduced risk of flame or explosion in utilizing a lower purity oxygen, relative to that which would exist in utilizing a higher purity oxygen.

The invention encompasses new methods of forming and utilizing ozone in removing materials from over semiconductor substrates.

SUMMARY OF THE INVENTION

The invention encompasses a method of removing at least some of a material from a semiconductor substrate. A feed gas is fed through an ozone generator to generate ozone. The feed gas comprises at least 99.999% O2(by volume). The ozone, or a fragment of the ozone, is contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate.

In another aspect, the invention encompasses another method of removing at least some of a material from a semiconductor substrate. A mixture of ozone and organic solvent vapors is formed in a reaction chamber. At least some of the ozone and solvent vapors are contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methodology encompassed by the present invention is described with reference toFIGS. 1–3. Referring initially toFIG. 1, an apparatus10is diagrammatically illustrated. Apparatus10comprises a reaction chamber12having a semiconductor wafer support14therein. A semiconductor wafer16is shown on support14.

An ozone generator18is shown mounted relative to chamber12such that ozone20formed within generator18is expelled into chamber12. An exemplary ozone generator is an ASTEX™ 8200, which is manufactured by Applied Science and Technology, of 3500 Cabot Rd, Woburn, Mass. It is to be understood that ozone generator18can be mounted outside of chamber12, and ozone flowed from generator18into chamber12. It is also to be understood that ozone generator18could be mounted such that it is fully enclosed within chamber12. Further, it is to be understood that ozone generator18can be mounted above wafer16, as shown, or can be mounted in other orientations relative to wafer16.

A feed gas source22is provided externally of chamber12, and a feed gas24is flowed from source22to ozone generator18. Feed gas24comprises O2, and in contrast to the prior art preferably comprises at least 99.999% O2(by volume). Feed gas24is flowed into ozone generator18to form ozone20. An advantage of utilizing a feed gas with a higher purity of oxygen than the prior art is that such reduces a concentration of nitrogen within the feed gas. In accordance with one aspect of the invention, it is recognized that nitrogen can be converted to various nitrous oxides (NOx) upon being passed with oxygen through an ozone generator. The nitrous oxides can be corrosive and otherwise damaging to integrated circuitry exposed to the nitrous oxides. Further, the nitrous oxides can form various acids (such as, for example, HNO3) which can be corrosive to various integrated circuitry materials, such as, for example, aluminum oxide (Al2O3). Accordingly, one aspect of the invention encompasses utilization of a higher purity oxygen in an ozone-generating feed gas than that which is utilized in the prior art. A related aspect of the invention is that such utilizes an ozone-generating feed gas having less nitrogen than prior art feed gases. Preferably, the ozone-generating feed gas24comprises less than or equal to 0.001% N2(by volume).

Semiconductor substrate16comprises an upper layer17. Semiconductor substrate16can comprise, for example, monocrystalline silicon lightly-doped with a background p-type dopant. To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. Upper layer17can comprise, for example, aluminum oxide (Al2O3), platinum, or other materials associated with fabrication of integrated circuitry.

A layer19is over upper layer17of semiconductor substrate16, and comprises a material which is to be removed. Layer19can comprise, for example, photoresist, such as, for example, a so-called I-line photoresist (typically a novolac resin), or a deep ultraviolet resist. Alternatively, layer19can comprise other organic materials.

Ozone20is utilized to remove at least some of layer19from over semiconductor substrate16. In other words, the ozone is utilized to remove a material defined by layer19from over the upper layer17of semiconductor substrate16.

In one aspect, ozone20flows to material19to react with the material and form a product which can be removed from over semiconductor substrate16. For instance, ozone20can oxidize an organic material19to form a relatively volatile material which can be swept from over layer17by flow of gases through reaction chamber12.

In another aspect, ozone20can be broken into reactive fragments which contact material19and react with the material to form a product which can be removed from over layer17. In the shown embodiment, an ultraviolet light source30is provided proximate reaction chamber12and adjacent a window32which extends through a wall of reaction chamber12. Ultraviolet light generated by source30passes through window32into chamber12. The ultraviolet light can then impact ozone20within chamber12to cause the ozone to break into reactive fragments. Such reactive fragments can comprise, for example, atomic oxygen. The fragments formed from the ozone can also comprise O2. In embodiments in which ozone20is exposed to ultraviolet light prior to contact of the ozone or fragments thereof with material19, such exposure preferably occurs proximate layer19. In such context, the term “proximate” means that the exposure occurs within one foot of layer19. Such can alleviate losses of the reactive species formed by the exposure prior to interaction of the reactive species with layer19. In particular aspects of the invention, the ultraviolet light can be shined onto a surface of layer19while the surface is exposed to ozone.

The apparatus10ofFIG. 1further comprises a reservoir50comprising a volatile material52. Reservoir50is on a reservoir holder54which can comprise a heater. In operation, material52is volatilized from reservoir50to form vapor within reaction chamber12which can enhance removal of material19by ozone20. Volatile material52can comprise, for example, water, and accordingly the vapor formed within the reaction chamber12will be water vapor. Alternatively, volatile material52could comprise an organic solvent such as, for example, one or more of cyclohexanone, acetone, or propylene glycol methylether acetate (PGMEA). In particular embodiments, the solvent can consist essentially of, or consist of, acetone. In other embodiments, the solvent can consist essentially of, or consist of, cyclohexanone. In yet other embodiments, the solvent can consist essentially of, or consist of, a mixture of cyclohexanone and PGMEA. A particular solvent can comprise a mixture of 60% cyclohexanone and 40% PGMEA. An alternative solvent is propylene glycol. Although the solvents described above would be liquid materials, it is to be understood that reservoir50could also comprise a volatile solid material.

If the material52is volatile at a temperature within reactor12, vapors will be formed from material52without additional heating of the material. Alternatively, if material52is not volatile at the temperature of reaction chamber12, or if it desired to enhance volatilization of material52, the material can be heated by, for example, a heater within support54.

If material52comprises a volatile organic material, then the vapors formed from material52will be volatile organic solvent vapors. It is to be understood that within the context of this document the term “solvent vapor” refers to a vapor formed from a volatile organic material, and not to any volatile organic materials formed by degradation of layer19within chamber12. If volatile solvent vapors are utilized in conjunction with the very pure oxygen described above, it is preferred that flames and sparks be kept out of the reaction chamber to alleviate a risk of fire or explosion.

Although reservoir50is shown provided within chamber12, it is to be understood that the invention encompasses other embodiments wherein reservoir50is provided outside of chamber12, and wherein solvent vapors are flowed into chamber12from the external reservoir. Also, the invention encompasses embodiments wherein vapors are provided in a gas source external of chamber12(such as, for example, a tank of gas), and piped into chamber12.

Organic solvent vapors are found to assist in removal of organic materials19(such as, for example, photoresist) from over semiconductor substrates. A possible mechanism is that the vapors may “wet” or otherwise improve susceptibility of an organic material19to ozone or reactive fragments formed from ozone. Such mechanism is provided to assist in understanding the present invention, and is not to limit the claims except to the extent that the mechanism is expressly recited within a claim.

FIGS. 2 and 3illustrate enlarged views of the semiconductor substrate16at processing steps of a method of the present invention.FIG. 2illustrates semiconductor substrate16having material19thereover. Specifically, material19is over a layer17. As discussed above, layer19can comprise an organic material such as, for example, photoresist. Layer17can comprise an inorganic material such as, for example, aluminum oxide or platinum.

Referring toFIG. 3, semiconductor substrate16is illustrated after material19has been removed from over layer17. Such removal can be accomplished by the processing described above with reference toFIG. 1, wherein ozone (or a reactive fragment generated from ozone) is contacted with material19to remove material19. It is noted that some of layer17can be exposed to the ozone, or ozone fragments, during removal of material19. In accordance with an embodiment of the present invention, the ozone preferably will be formed from an oxygen feed material that comprised less than 0.001% nitrogen. Accordingly, any concentration of nitrous oxides or reactive products formed from nitrous oxides will be lower in methods of the present invention than in prior art processes. Accordingly, if layer17comprises aluminum oxide, platinum, or other materials which can be etched or otherwise corroded by nitrous oxide or products thereof, methods of the present invention can alleviate such corrosion relative to prior art methods.