Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
2000-03-10
2002-09-24
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S022000
Reexamination Certificate
active
06455214
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to techniques related to scanning type exposure apparatus and the like; and, in particular, to a scanning type exposure method, apparatus, device manufacturing method, and the like used when manufacturing semiconductor devices, liquid crystal display devices, and the like by lithography process.
2. Related Background Art
Conventionally used in the lithography process for manufacturing semiconductor devices, liquid crystal display devices, and the like are projection exposure apparatus which project and expose, by way of a projection optical system, a pattern formed in a mask or reticle (hereinafter referred to as reticle) onto a substrate such as wafer or glass plate (hereinafter referred to as photosensitive substrate or wafer) coated with photoresist or the like. Of apparatus of this kind, in the main stream have conventionally been stationary type (also known as step-and-repeat system) exposure apparatus which move a wafer stage carrying a wafer as a photosensitive substrate mounted thereon stepwise by a predetermined amount in two-dimensional directions of X and Y, and then transfer a reticle pattern to a shot area on the photosensitive substrate by way of a projection optical system. As the circuit pattern is becoming finer as the semiconductor devices have a higher degree of integration, however, much higher resolution and exposure accuracy have been demanded as performances of the exposure apparatus. Known as an exposure apparatus responding to such a demand are scanning type exposure apparatus of so-called step-and-scan system which sequentially transfer a reticle pattern onto a water by way of a projection optical system by moving a reticle stage holding a reticle and a water stage in a predetermined scanning direction relative to the projection optical system.
SUMMARY OF THE INVENTION
Having studied the above-mentioned scanning type exposure apparatus, the inventor has found the following problems. Namely, in the conventional scanning type exposure apparatus, when exposing a reticle pattern onto a certain shot area on a wafer, it is necessary that information (focus information) about the position of the wafer surface along the optical axis direction of the projection optical system (the position indicating the focus state of the exposure area) at the exposure position (within the shot area to be exposed) be measured with a focus sensor immediately before the exposure, and then scanning exposure be carried out while a sample table (z stage) which is minutely movable in the optical axis direction with a wafer held thereby is being positioned such that the shot area surface on the water falls within the depth of focus of the projection optical system.
In such a scanning type exposure apparatus, the focus information of the wafer immediately before starting exposure can easily be detected without any problem in the shot areas other than those located in marginal portions of the wafer. In the case of exposure of a shot area in a marginal portion of the wafer, however, when the wafer surface is displaced along the optical axis direction beyond the trackability of the z stage, a reticle pattern is disadvantageously exposed onto this shot area in a defocused state.
When carrying out exposure while relatively scanning the exposure area conjugate with the illumination area on the reticle from a marginal portion including an edge of the wafer surface to the inside (such an expression being used here for the convenience of explanation though the wafer actually moves while the exposure area is fixed), there has conventionally been employed a method in which exposure is performed while the exposure area is always relatively scanned from the inside of the wafer surface to the marginal portion or a method in which focus sensors to be used are selectively added depending on the position or form of the effective area for exposure shot. In the case where exposure in carried out while relatively scanning from the inside of the wafer surface to the marginal portion, by contrast, though exposure in a defocused state is seen, such a state has been left as it is without no counter measures provided.
In view of such circumstances, it is an object of the present invention to provide aim exposure method, an exposure apparatus, and the like comprising a configuration which can further effectively prevent color inconsistencies from occurring due to defocusing upon exposure.
In order to achieve the above-mentioned object, the exposure method according to the present invention is a scanning type exposure method, as shown in
FIG. 5
, in which, while a reticle and a substrate are moved relative to each other in a predetermined scanning direction with respect to a projection optical system, a pattern formed in the reticle is sequentially transferred onto the substrate by way of the projection optical system, the method comprising a focus detection stop for detecting positions of a surface of the substrate in an optical axis direction of the projection optical system at a plurality of detection points on the substrate with a multipoint focus sensor; a substrate driving stop of driving the substrate in the optical axis direction of the projection optical system or obliquely with respect to a plane orthogonal to the optical axis; a control step of controlling the driving of the substrate in the substrate driving step; and a judging stop (ST
3
) for judging, when a sensor in a usable state in the multipoint focus sensor and a predetermined shot area on the substrate have a predetermined relationship with each other, whether the sensor in the usable state is sensible or not; the control step performing, according to a result of the judgment, at least one of a first adjustment operation for adjusting the position of the substrate along the optical axis direction (thickness direction of the substrate) or a second adjustment operation for adjusting the inclination of the substrate.
In this specification, the sensor in a usable state refers to a sensor specified by a user, a sensor used in the immediately preceding scanning exposure step, or the like, which is a sensor, of a sensor group prepared (arranged) beforehand, whose switch is turned on so as to be set to a detection state.
Since the method according to the present invention comprises a judging step for judging whether sensors in the usable state are located within the effective area of the substrate or not, i.e., whether sensible or not, it can be judged whether or not these sensors can be used for controlling the position of the substrate and the like. Further, since the method according to the present invention has an exposure control step, the position of the surface of the substrate and the like can be controlled according to at least one of the first adjustment operation for adjusting the position of the substrate in the optical axis direction (focal position) and the second adjustment operation for adjusting the inclination of the substrate.
Here, it is preferred that the case where the predetermined relationship exists in the judging step be the case where the sensor in the usable state is located at an exposure end position of the predetermined shot area.
As a consequence, when exposure is carried out while the exposure area is relatively scanned from the inside of the wafer surface to a marginal portion including an edge, even upon the exposure of a shot area in the marginal portion, a focusing control operation or a focusing/leveling control operation combining focusing control and leveling control together is appropriately carried out.
In the present invention, the sensor in the usable state may be a follow-up sensor selected in the preceding processing. In this case, the judging step can immediately be carried out without newly selecting a sensor.
As for the adjustment operation determined by the arrangement of sensors, the inclination of the substrate is adjusted with respect to the predetermined scanning direction in the case where the detection point
Furukawa Osamu
Imai Yuji
Wakamoto Shinji
Yamazaki Masayoshi
Nikon Corporation
Young Christopher G.
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