Metal working – Barrier layer or semiconductor device making
Reexamination Certificate
1999-08-27
2002-11-26
Graybill, David E. (Department: 2814)
Metal working
Barrier layer or semiconductor device making
Reexamination Certificate
active
06485531
ABSTRACT:
The invention relates to a process chamber in which various processing steps in the manufacture of semiconductors can be carried out in accordance with the preamble of the independent patent claim.
Several processing steps in the manufacture of semiconductors, in particular in the manufacture of integrated semiconductor circuits, take place in such a manner that the wafer (a disc on which a large number of such integrated semiconductor circuits are arranged) is rotated in a process chamber. In addition to this it is often necessary to carry out the individual steps under clean room conditions. In the individual processing steps, in particular media such as liquids (e.g. etching liquids, cleaning fluids, photosensitive resists, developers, etc.), vapours (e.g. metallic vapours or liquid vapours etc.), gases (etching gases, oxygen for oxidation, flushing gases, protective gases, etc.), suspensions (e.g. for the production of passivating layers and other thick film layers), molten polysilicon, electromagnetic waves, ion beams and yet others are applied to or act on the wafer respectively. Several selected processing steps will be briefly mentioned in the following in an exemplary manner which take place in a process chamber in which the wafer is rotated.
For example a photosensitive resist can be applied from a liquid nozzle (or else from a spray can) to the rotating wafer, such as is described for example in U.S. Pat. No. 5,395,803. Alternatively, it is also possible to apply the photosensitive resist to the wafer at rest and then to rotate the latter, as is for example described in U.S. Pat. No. 4,822,639.
As a result of the increased surface tension at the edge of the wafer, slight super-elevations often occur here, which must be removed. This takes place in that a solvent is applied to the rotating wafer in the peripheral region, as is e.g. described in U.S. Pat. No. 4,510,176. This processing step can for example also be combined with the application of the photosensitive resist, which is described for example in U.S. Pat. No. 5,773,083.
In another processing step for example suspensions are applied and passivating layers thereby produced on the wafer. In this, in a manner similar to the photosensitive resist coating, for example liquids with smallest glass or silicon dioxide particles are applied, which then produce the passivating layer. Processing steps of this kind are for example described in U.S. Pat. No. 5,376,176 or in U.S. Pat. No. 5,328,871. In layers produced in this manner a processing step is likewise required in which edge super-elevations are removed (as e.g. described in U.S. Pat. No. 4,732,785).
It is furthermore also possible to produce thin film layers on rotating wafers, e.g. of silicon dioxide, of metals or of carbon (DLC=Diamond-Like Carbon). For this purpose the wafers are coated by means of known procedures such as for example the CVD (Chemical Vapour Deposition) process or the PVD (Physical Vapour Deposition) process. In these processes the homogeneity of the coating of the wafer can be advantageously influenced through the rotation of the wafer, in particular when the wafer rotates very rapidly, e.g. with speeds of rotation up to 16,000 rpm. Methods of this kind are described for example in U.S. Pat. No. 5,630,881.
Furthermore, methods of this kind are also suitable, for example through the application of molten silicon to a rotating plate, to manufacture polycrystalline silicon wafers, in a manner similar to that already described in the production of the “thick” layers. This is e.g. described for example in U.S. Pat. No. 4,561,486.
Furthermore, it is also possible to apply liquid or gaseous solvents to a rotating wafer for the removal of coatings, e.g. for the removal of photosensitive resists. This is described e.g. in U.S. Pat. No. 4,749,440 or in U.S. Pat. No. 4,510,176.
Moreover, it is also possible to exploit the rotating wafer for various etching processes. This is advantageous in so far as a homogeneous etching speed is therein achieved over the entire wafer, which can be of importance in particular in order to avoid an under-etching. If for example etching liquid is applied to the rotating wafer from a nozzle, then a homogeneous etching film develops, which is uniformly renewed in a manner which is controlled by the liquid supply. This is described for example in U.S. Pat. Nos. 4,903,717 or 4,350,562. Alternatively, it is also possible to allow the wafer to rotate on a liquid film, as is described in U.S. Pat. No. 4,350,562.
In other etching processes, etching vapours or etching gases are used for the etching of the wafer, as is described for example in U.S. Pat. No. 5,370,741, in U.S. Pat. No. 5,174,853 or in U.S. Pat. No. 5,248,380. The wafer which is exposed to these vapours or gases is likewise rotated during the etching process. In this etching process it is also possible to etch both sides of a wafer at the same time (U.S. Pat. No. 4,857,142). In the so-called “plasma etching” process a gas which is ionised with the help of an electrical field (“plasma”) is used for the etching. This is for example described in U.S. Pat. No. 4,230,515. In all the described etching processes it is advantageous when the wafer is rotated.
Furthermore, it is also possible to carry out ion implantations on rotating wafers. In this the wafer, which rotates with a speed of rotation of about 500-1500 rpm, is bombarded with ion beams. For this a plurality of wafers are normally arranged on a rotary plate, as is described in U.S. Pat. No. 4,745,287.
Further processing steps with rotating wafers relate to the washing of the wafer (“spin rinsing”) similarly as in “spin etching”, in which the wafer is charged with a cleansing liquid, e.g. with water of highest purity. The drying of the wafer is also possible in this manner: Liquid residues are hurled outwards by centrifugal forces (“centrifugal wafer dryer”), see e.g. U.S. Pat. No. 4,300,581.
Although only a selected number of processes or process steps respectively have been described above, there are numerous further process steps or processing steps respectively of this kind which are carried out in a process chamber with rotating wafers. In this, various media—among them radiation is also to be understood—such as liquids, suspensions with solids, gases and vapours, electromagnetic fields, ion beams etc. are applied to the wafer as a rule with the help of applicators such as nozzles and nozzle systems (heads with a large number of nozzles), tube systems, radiation sources, electrodes, heating elements and heat radiators.
In this the wafer is at least individually rotated, or else a plurality of wafers are rotated in common with the help of a corresponding rotatable holder apparatus. This holder apparatus is designated in the following as a rotary head for the sake of simplicity. The rotary head, which holds and rotates the wafer, is often driven via a rotating shaft most often from below, sometimes also from above. In this the rotating shaft is introduced into the inner space of the process chamber via a seal from below or from above. The drive motor is located as a rule outside the inner space of the process chamber in order to keep the inner space of the process chamber free from contaminations (clean room conditions) and to protect the motor against corrosion.
The applicators (nozzles, nozzle systems, tube lines, electrodes, radiation sources, etc.) are necessarily located above or below the rotary head. Only in exceptional cases (application of gases) is it possible to treat the wafer from both sides. In every case, however, the driving of the rotary head from below or from above represents a restriction in regard to the arrangement of the applicators.
This manner of driving and journalling the rotary head also represents an additional restriction for the supplying of the wafer or wafers respectively. The wafer (the wafers) can—when the rotary head is driven from below—not be supplied from below. The supplying from above is mostly also not possible due to the arrangement of the applicators, so that
Graybill David E.
Hynes William Michael
Levitronix LLC
Townsend and Townsend / and Crew LLP
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