In the drawings, wherein the same reference number indicates the same element throughout the separate views:
Various embodiments of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these embodiments. One skilled in the art will understand, however, that the invention may be practiced without many of these details.
It has now been discovered that when a heated processing or cleaning fluid is applied to a semiconductor wafer or other workpiece for removing contaminants from features in the workpiece, the most substantial cleaning typically takes place in the first few seconds after the fluid contacts the features in or on the wafer. The heated processing fluid tends to quickly lose heat to the cooler workpiece. Consequently, after the first few seconds of contact, the fluid cools considerably, before a thermal recovery takes place, and processing reactions correspondingly slow down and become less effective.
It is desirable therefore to maintain the processing fluid at a high temperature to increase the efficiency of the cleaning process. To this end, a wafer or other workpiece may be pre-heated to a desired temperature before applying the processing fluid to the workpiece. Thus, when the processing fluid reacts with the features in the heated workpiece, it can remain at a high temperature for a longer time. As a result, the processing fluid reacts more efficiently with the contaminants to be removed from the wafer features. This allows for faster cleaning cycles and reduces (or eliminates) the number of times a rinsing process must be introduced between cleaning steps.
It is typically difficult to efficiently remove the reacted processing fluid and replace it with fresh fluid at or near the bottom of a deep via or contact hole. Thus, it is especially desirable to increase the efficiency of the first few seconds of the cleaning process to reduce or eliminate the need for multiple cleaning steps and rinsing steps.
The wafer 12 is supported on or secured to a workpiece holder 14, such as a rotor or chuck, a stationary stage, or other rotatable or fixed support. Depending on the processes to be performed, the processing chamber 10 may include nozzles 16 or other openings for delivering liquid or gas to the wafer 12, heating elements 18 for heating the wafer 12, transducers for delivering sonic energy to the wafer 12, UV or IR lamps or other process elements.
Referring to
In a first embodiment, the wafer 12 is loaded into the processing chamber 10 and secured to the workpiece holder 14 via a robot or by hand. The robot, if used, may have a heated end effector. Heat is then applied to one or both sides of the wafer 12 via one or more heating elements 18. The heating elements 18 may be located anywhere within the processing chamber 10, including on or in the workpiece holder 14. The heating elements 18 may include infrared (“IR”) lamps, a hot plate, or other heater in or on the workpiece holder 14. Heated liquid, such as deionized water, may be sprayed, jetted or otherwise applied in bulk onto the wafer 12 to heat one or both of the upper and lower wafer surfaces.
The wafer 12 may be heated to a temperature at or near the temperature of the processing fluid that will be used to clean the wafer 12. The wafer 12 and the processing fluid may be heated to any temperature(s) suitable for a given processing application. Many processing fluids or chemicals work well at temperatures in the range of 35 to 99° C. (or higher), or 50 to 70° C., or greater than 50° C. Thus, the wafer 12 may be heated to approximately the same or a higher temperature than the processing fluid used for a given processing application.
Once the wafer 12 reaches the desired temperature, the processing fluid is sprayed or otherwise applied onto the wafer 12 from the nozzles 16 (or other openings) in the processing chamber 10. The processing fluid is preferably a liquid, but may be a vapor or a gas. Any suitable processing fluid, cleaning fluid, or chemical mixture, particularly those that are most reactive at elevated temperatures, may be used to clean the vias 30, trenches, or other features on the wafer 12.
With the wafer 12 pre-heated, the chemical reactions between the processing fluid and the polymer layer 32 or contaminants in the vias 30 occur at a high temperature. Accordingly, as the processing fluid moves into the lower regions of the vias 30, it remains at a higher temperature and reacts efficiently with contaminants in the lower regions. As a result, contaminants are removed from the lower regions of the vias 30 as effectively, or substantially as effectively, as from the upper regions of the vias 30.
After application of the processing fluid, the wafer 12 may be rinsed with deionized water or another suitable cleansing fluid to flush any loose contaminants out of the vias 30 or other features in the wafer surface. If contaminants are still present after the wafer 12 is rinsed, additional processing fluid may be sprayed or otherwise delivered to the wafer 12 to effectively remove any remaining contaminants. Processing and rinsing steps may be alternated until a desired level of cleanliness is achieved. As the wafer 12 is heated before application of the processing fluid, the efficiency of the chemical reactions is improved, and only one processing step may be required.
In an alternative embodiment, one or both sides of the wafer 12 may be heated before the wafer 12 is loaded into the processing chamber 12. The wafer 12 may be heated in an oven, on a hot plate, or in or on another suitable heating device. The wafer 12 is preferably heated to a temperature higher than the processing fluid, to compensate for the cooling of the wafer during transport of the wafer 12 from the heating device into the processing chamber 10. The wafer 12 may, for example, be heated to a temperature that is 5 to 10° C. higher than the processing fluid. After the pre-heated wafer 12 is loaded into the processing chamber 10, the heated processing fluid is sprayed or otherwise delivered onto the wafer 12 to clean the vias 30, trenches, or other features on or in the wafer 12. After application of the processing fluid, the wafer 12 may be rinsed with deionized water or another suitable cleaning fluid to flush any loose contaminants out of the vias 30 or other features in the wafer surface.
Heat may continuously be applied to the wafer 12 throughout some or all of the cleaning process, to keep the wafer 12 at a desired elevated temperature. Heat may, for example, be provided to the wafer 12 via heating elements on the workpiece holder 14 while the processing fluid is delivered to the wafer 12. Alternatively, heating elements 18 on the walls, base, or top of the processing chamber 10 may continuously provide heat to the wafer 12 during delivery of the processing fluid to the wafer 12.
If, after the wafer 12 is rinsed, the application of additional processing fluid is required to remove any remaining contaminants, the wafer 12 may optionally be re-heated to a temperature substantially equal to or greater than the processing fluid to be applied. In this embodiment, the workpiece holder 14 or the interior of the processing chamber 12 may include heating elements for heating the wafer 12 while it is secured to the workpiece holder 14. Thus, after the rinsing step is completed, the wafer 12 may be re-heated before application of additional processing fluid in order to promote increased reaction kinetics. The methods described here may be performed in combination with ozone processes, as described in U.S. Patent Publication No. 2002/0157686, incorporated herein by reference.
The processes described above may also be used in batch wafer processing in which multiple wafers are simultaneously cleaned or processed. A batch of wafers secured in a wafer tray or other workpiece holder may be pre-heated in the processing chamber or in a separate external heating device. Once the heated batch of wafers is at the desired temperature and secured within the processing chamber, heated processing fluid may be sprayed or otherwise delivered onto the batch of wafers to clean the vias 30, trenches, or other features on or in the wafers. In single or batch processing, a heated wafer holding storage location or buffer may be used to reduce process times. Features described as in the workpiece may also be on the workpiece, and vice versa.
The words used here are intended to be interpreted in their broadest reasonable manner, even though they are used with a detailed description of certain specific embodiments of the invention. Any words intended to be interpreted in any restricted way, however, will be specifically defined in this detailed description section.
Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of items in the list.
While several embodiments have been shown and described, various changes and substitutions may of course be made, without departing from the spirit and scope of the invention. Many of the method steps described herein, for example, may be performed in a different order than that which is explicitly described. Moreover, many of the embodiments described herein may be used separately or in combination with one or more additional embodiments. The invention, therefore, should not be limited, except by any claims and their equivalents.