Semiconductor devices are made on substrates, such as silicon wafers or glass plates. These devices are made by a sequence of fabrication steps. Substrates must be transported between processing stations for at least some of the fabrication steps.
Substrates are stored in cassettes for transfer between processing stations, metrology stations, and other locations. Although cassettes may be carried manually between processing stations, the transfer of cassettes is typically automated by an automatic guided vehicle (AGV). When the fabrication steps are complete, the substrate is loaded back into the cassette.
To ensure that the processing equipment does not sit idle, a nearly continuous supply of unprocessed substrates should be available at the processing station. Unfortunately, many processing stations can hold only a single cassette at the loading platform. Therefore, once all of the substrates in the cassette have been processed, the cassette must be quickly replaced, either manually or by an AGV with a new cassette containing unprocessed substrates. Running such a just-in-time cassette inventory system requires either significant operator oversight or a large number of AGVs, both of which are costly.
 Figure 1. |
This invention provides a method and apparatus for storing multiple cassettes at a processing station, ensuring that a nearly continuous supply of unprocessed substrates is available for processing. Multiple cassettes can be stored at a processing station in a front-end support frame, and a cassette can be moved to one of a plurality of vertically disposed docking stations where substrates are extracted and transferred to the processing equipment.
Figure 1 is a top view of a processing station of the present invention in which one or more substrates (A) are processed. The processing station has a front-end staging area (B), which is separated from a loading and storage area (C) by a cleanroom wall (D). The cleanroom wall separates a cleanroom (E), where the loading and storage area is located, from a gray area (F), where a processing system (G) is housed. (The loading and storage area is where cassettes of substrates are delivered and loaded/unloaded into/from the processing station.)
The processing system may include one or more load-lock chambers (H), a central transfer chamber (I), and a plurality of processing chambers (J). Inside processing chambers, the substrate may be subjected to a variety of fabrication steps, such as thin film deposition, oxidation, nitration, etching, thermal processing, or lithographic processing. (The processing system could have just a single processing chamber, or it could be a device, such as a chemical/mechanical polisher, that does not include any processing chambers. In addition, the processing system could include metrology devices instead of or in addition to processing devices.)
To transfer substrates through the cleanroom wall (D), cassettes (K) may be positioned at one or both docking stations (L). Each docking station includes a docking platform (M) to support a cassette, an opening (N) formed through the cleanroom wall, a movable door (O) that seals the opening when a substrate is not to be transferred through the opening or when a cassette is not positioned on the docking platform.
Patent number: 6,955,517
Date: October 18, 2005
Inventors: Jaim Nulman (Palo Alto, CA) and Nissim Sidi (Tel Aviv, Israel)
Wafer cleaning method and resulting wafer
To fabricate an integrated circuit on a semiconductor substrate such as a semiconductor wafer, multiple layers of conductive or insulative materials are patterned and formed upon one another. In order to preserve circuit continuity, it is critical that each layer is aligned to the previous layer with great precision and accuracy. The alignment of the layers is accomplished using a wafer stepper, which transfers a desired pattern from a reticle, or mask, onto a layer formed on the semiconductor wafer.
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The registration marks are typically formed on unused portions of the semiconductor wafer, such as along a peripheral edge of the semiconductor wafer or near scribe lines that separate locations of semiconductor dice, by etching small, narrow trenches on the semiconductor wafer.
During processing of the wafer, the registration marks oftentimes become filled with debris. Various processes produce the debris, such as by abrasive processes, including chemical/mechanical planarization (CMP). To prevent this accumulation, a coating of photoresist is applied to the registration mark before the metallic surface layer is planarized. However, this increases the time as well as the number of steps required to fabricate semiconductor dice.
This invention relates to a method of cleaning a semiconductor wafer and, more particularly, to a method of cleaning registration marks on the semiconductor wafer, as well as to a wafer subsequent to such cleaning. This is done by removing residual contaminants from an alignment mark on a semiconductor wafer after CMP. The semiconductor wafer is scrubbed and dipped in a hydrogen fluoride solution to remove a layer damaged by the CMP. The semiconductor wafer is then cleaned using a solution of ammonium hydroxide, hydrogen peroxide, and deionized water that is agitated by ultrasonic or megasonic energy.
The wafer may include at least one registration mark (A) on its surface. The registration mark may be a registration box (B) or an SLM (C) that includes trenches (D) having a width of up to approximately 3 .mu.m.
Patent number: 7,023,099
Date: April 4, 2006
Inventors: Michael T. Andreas (Boise, ID) and Paul A. Morgan (Kuna, ID)