US 20050225308 A1
An apparatus includes semiconductor processing equipment. A particle detecting integrated circuit is positioned in a vacuum environment, the particle detecting integrated circuit containing a device having a pair of conductive lines exposed to the vacuum environment. The pair of conductive lines is spaced at a critical pitch corresponding to diameters of particles of interest. A computer system is linked to the particle detecting integrated circuit to detect a change in an electrical property of the conductive lines when a particle becomes lodged between or on the lines.
1. An apparatus comprising:
a vacuum chamber containing a particle detecting integrated circuit, the particle detecting integrated circuit including a device having a pair of exposed conductive lines spaced at a critical pitch corresponding to particles of interest.
2. The apparatus of
3. The apparatus of
4. The apparatus of
5. The apparatus of
6. The apparatus of
7. The apparatus of
8. The apparatus of
9. An apparatus comprising:
a mask stage in a vacuum chamber of semiconductor processing equipment;
a particle detecting integrated circuit embedded in the mask stage, the particle detecting integrated circuit containing a device having a pair of conductive lines exposed to a local vacuum environment, the pair of lines spaced at a critical pitch corresponding to particles of interest.
10. The apparatus of
11. The apparatus of
12. The apparatus of
13. The apparatus of
14. The apparatus of claim 1Q wherein the computer system is semiconductor component circuitry.
15. The apparatus of claim 1Q wherein the computer system is off-chip circuitry.
16. The apparatus of
17. The apparatus of
18. The apparatus of
19. A method comprising:
exposing a particle detecting integrated circuit to residual gases and particles within a vacuum environment, the particle detecting integrated circuit containing a device having a pair of conductive lines spaced at a critical pitch corresponding to particles of interest;
applying a voltage to the pair of conductive lines; and
detecting a change in an electrical property of the conductive lines resulting from a particle landing on or between the pair of conductive lines.
20. The method of
21. The method of
22. The method of
23. The method of
24. A chip fabrication method comprising:
a photolithography process including a real-time particle detection process, the real-time particle detection process comprising:
exposing a particle detecting integrated circuit embedded in a stage to residual gases and particles within a vacuum environment, the particle detecting integrated circuit containing a device having a pair of conductive lines spaced at a critical pitch corresponding to particles of interest;
applying a voltage to the pair of conductive lines;
detecting a change in an electrical property of the conductive lines resulting from a particle landing on or between the pair of conductive lines;
an etching process;
a stripping process;
a diffusion process;
an ion implantation process;
a deposition process; and
a chemical mechanical planarization process.
25. The method of
26. The method of
27. The method of
28. The method of
applying a voltage to the conductive lines of the plurality of devices; and
detecting changes in electrical properties of the pairs of conductive lines resulting from particles landing on or between the pairs of conductive lines.
29. The method of
This invention relates to real-time monitoring of particles in a semiconductor vacuum environment.
A microprocessor is an integrated circuit (IC) built on a tiny piece of silicon. A microprocessor contains millions of transistors interconnected through fine wires made of aluminum or copper.
Microprocessor fabrication is a complex process involving many steps. Microprocessors are typically built by layering materials on top of thin rounds of silicon, called wafers, through various processes using chemicals, gases and light. In chip making, very thin layers of material, in carefully designed patterns, are put on the blank silicon wafers. The patterns are computerized designs that are miniaturized so that up to several hundred microprocessors can be put on a single wafer.
Because the patterns are so small, it is nearly impossible to deposit material exactly where it needs to be on the wafer. Instead, a layer of material is deposited or grown across an entire wafer surface. Then, the material that is not needed is removed and only the desired pattern remains.
The microprocessor fabrication process begins with “growing” an insulting layer of silicon dioxide on top of a polished wafer in a high temperature furnace. Photolithography, a process in which circuit patterns are printed on the wafer surface, is next. A temporary layer of a light sensitive material called a “photoresist” is applied to the wafer. Ultraviolet light shines through clear spaces of a stencil called a “photomask” or “mask” to expose selected areas of the photoresist. Masks are generated during a design phase and are used to define a circuit pattern on each layer of a chip. Exposure to light chemically changes the uncovered portions of the photoresist. The machine used to do this is typically called a “scanner” because it scans one die or a few die at a time, then steps to the next die or set of die until it has exposed the entire wafer.
An active area of the mask is exposed to a vacuum environment of a scanner and is at high risk of accumulating particles. If a particle lands in a critical part of the active area then it will lead to a printed defect on the wafer. This defect causes decreased yields, or increased wafer cost in rework if the defect is fortuitously caught prior to further wafer processing by wafer defect metrology.
Like reference symbols in the various drawings indicate like elements.
The systems and techniques described here relate to real-time monitoring of particles in vacuum environments of semiconductor processing equipment. For ease of discussion, a photolithography process of a semiconductor fabrication is used as an example for describing the real-time monitoring of particles in vacuum chambers of semiconductor processing equipment. However, the systems and techniques described herein are not limited to photolithography; rather, they can be used in any semiconductor vacuum process environment in which a real-time monitoring of particles is needed, such as while depositing a film on a semiconductor wafer or implanting a dopant on a semiconductor wafer.
A semiconductor manufacturing process hinges on a use of a photographic process to generate fine featured patterns of an integrated circuit (IC). Each layer of a chip is defined by a specific mask. A mask is somewhat like a photographic negative, which is made by patterning a film of chromium on a pure quartz glass plate. The finished plates are referred to as reticles. Reticles are manufactured by sophisticated and expensive pattern generation equipment, which is driven from a chip design database. The patterns are formed on the chromium plated quartz by removing the chromium with either laser or electron-beam driven tools.
The illuminator enclosure 14 includes laser optics that, for example, generate EUV light from a plasma generated when a laser illuminates a jet of xenon gas. The light is collected and focused on a mask 22 residing on a mask stage 24 in the mask-stage chamber 16 by a series of condenser mirrors 26 a, 26 b, 26 c, 26 d. A mask image is projected onto the wafer 12 by a reduction camera 28 a, 28 b, 28 c, 28 d, while the mask 22 and wafer 12 are simultaneously scanned. The entire operation takes place in high-vacuum environmental chambers and is controlled by a computer system 29.
Impurities 32, such as metallic and/or non-metallic particles, can be present in the mask-stage chamber 16. If one of the particles 32 lands on a critical part of an active area of the mask 22 it will lead to a printed defect on the wafer 12. This defect causes decreased yields, or increased wafer cost in rework if the defect is detected at an early stage. The present invention provides a real-time detection of the presence of particles in the vicinity of the mask 22 that would warrant stoppage of the lithography system 10. In an extreme-ultraviolet (EUV) lithography environment, particle sizes that are estimated to be of concern are on the order of 50 nanometers (nm).
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A number of these devices 31 can be located in the semiconductor device 30 providing determination of particle density counts. Devices 31 sensitive to various particle sizes, e.g., by varying the pitch of the pairs of lines, can also be incorporated into the active semiconductor component 30 to monitor a range of particle sizes through a region or regions of interest.
In a particular embodiment, each active semiconductor component 30 is protected by a remote-controlled removable cover (not shown) until the component 30 is ready to be exposed to a vacuum environment. The cover is remotely triggered by the computer system 29 or other triggering mechanism (not shown) to open when desired, exposing the device 31 to the vacuum environment.
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Process 100 applies (104) a voltage to the pair of conductive lines and detects (106) a change in an electrical property of the conductive lines resulting from a particle landing on or between the pair of conductive lines. A metallic particle having a diameter the size of the pitch between the lines, or larger, generates a short in a current flow between the lines. A non-metallic particle having a diameter the size of the pitch between the lines, or larger, generates a change in capacitance between the lines. The short and/or change in capacitance is detected by the computer system. Once detected, corrective action can be initiated.
Other embodiments are within the scope of the following claims.