Optics: measuring and testing – Inspection of flaws or impurities – Surface condition
Reexamination Certificate
2001-09-12
2003-11-11
Adams, Russell (Department: 2851)
Optics: measuring and testing
Inspection of flaws or impurities
Surface condition
C356S237200, C356S237100
Reexamination Certificate
active
06646735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method employed to conduct a surface inspection on a test piece such as a wafer during the process of manufacturing IC chips, liquid crystal display panels and the like.
2. Description of Related Art
Many different circuit patterns are stacked over a plurality of layers at a surface of a substrate such as a wafer to manufacture an IC chip or a liquid crystal display element panel. These circuit patterns are formed by stacking them one layer at a time on the wafer through a photolithography process or the like.
When manufacturing an IC chip, for instance, a resist is applied in a thin layer onto an oxide film formed at a surface of a wafer (substrate) and then a circuit pattern at a reticle is exposed onto the resist layer by an exposure apparatus. Next, the resist having been exposed is removed through development processing, thereby forming a pattern constituted of a resist layer achieving an identical form (or a similar reduced form) to the circuit pattern at the reticle. Subsequently, after removing the exposed oxide film through etching, the remaining resist layer is removed to form a circuit pattern constituted of the oxide film layer at the surface of the wafer. An element such as a diode is formed through doping processing or the like implemented on the circuit pattern constituted of the oxide film layer. While there is a degree of variance with regard to the manufacturing method depending upon the type of IC being manufactured, the process of forming a specific circuit pattern layer as described above is normally performed repeatedly to stack a plurality of circuit patterns over many layers on the wafer.
When circuit patterns are stacked over numerous layers on the wafer in this manner, a surface inspection is conducted to verify that no defect, abnormality or the like has occurred in the circuit pattern formed in each layer. This inspection may be implemented when, for instance, a circuit pattern constituted of the resist layer has been formed. If a surface defect, an abnormality or the like such as a deformation of the circuit pattern, inconsistency in the film thickness of the resist layer or a scar is detected during the inspection, reclaim processing is implemented for this circuit pattern layer. Namely, the resist is stripped and then a new resist layer is applied and exposed.
If a defect, an abnormality or the like occurs at any of the circuit patterns when manufacturing an IC chip or the like by stacking the circuit patterns over multiple layers on the wafer, the acceptability of the IC chip as a product is compromised. For this reason, it is crucial to conduct an inspection to detect such defects, abnormalities and the like, i.e., to conduct a wafer surface inspection.
If any defect is detected during the resist development processing stage, reclaim processing can be implemented to eliminate the defect by removing the resist and reapplying the resist layer. However, an area where a defect, an abnormality or the like is detected when a circuit pattern has been formed at an oxide layer or the like through etching cannot be reclaimed. This means that a pattern can be reclaimed by removing the resist pattern layer only as long as surface defects are detected through a surface inspection conducted at the resist development processing stage. Namely, the surface inspection conducted at the resist pattern formation stage is of especially important.
The surface inspections proposed in the related art include an inspection in which various types of inspection illuminating light are irradiated on the test piece (wafer) surface from different angles and the light reflected at the test piece is directly observed visually by the inspector as the test piece is rotated or tilted.
Such an inspection method is generally referred to as a macro inspection. When a macro inspection is implemented through visual observation by the inspector, there is a risk of inconsistency manifesting in the inspection results due to varying judgment criteria, skills and the like among individual inspectors. In addition, the onus placed on the inspector is significant. Accordingly, the possibility of automating macro inspections has been examined and various automatic macro inspection apparatuses have been proposed. For instance, there is an apparatus that performs an automatic surface inspection by irradiating inspection illuminating light onto a surface of a test piece, receiving the diffracted light from a repetitive pattern formed at the surface of the test piece with an image-capturing device to take in a diffracted image and performing image-processing on the diffracted image.
However, in the surface inspection apparatus in the related art, the optimal settings cannot be automatically selected for the apparatus conditions (the illuminating light incident angle, the tilt angle of the test piece substrate, the wavelength of the illuminating light, the position at which the light exiting the test piece and entering the image-capturing device is received and the like) when capturing a diffracted image based upon the diffracted light from the circuit pattern (repetitive pattern) on the surface of the test piece. The optimal settings in this context refer to conditions under which the direction along which the diffracted light originating from the repetitive pattern advances substantially matches the direction along which the optical axis of the light-receiving optical system that receives the diffracted light extends and, in other words, they are conditions under which a diffracted image that is good enough to enable a surface inspection is obtained.
In the surface inspection apparatus in the related art, the diffracted image of the test piece is displayed on the monitor and the inspector selects the optimal settings for the apparatus conditions by checking the diffracted image on the monitor. However, this method poses a problem in that it is not always easy for the inspector to accurately judge the optimal apparatus conditions and the inspector must have significant skills and experience.
In addition, since circuit patterns are formed over numerous layers, as explained earlier, and diffracted light originates from the individual pattern layers, there is a problem in that when a defect is detected based upon a diffracted image, it cannot be ascertained as to the specific layer from which the diffracted image has originated. For instance, a defect occurring during the process of pattern formation at a given layer may be overlooked and may be detected later during a surface inspection conducted after forming a pattern at an upper layer. In such a case, if it is erroneously judged that the defect is present at the uppermost layer, the uppermost resist pattern layer will be removed to reclaim the pattern. However, since the defect is present at the lower layer in reality, the reclaim processing described above will not solve the problem.
Thus, there is a problem with regard to the surface inspection apparatus in the related art in that it cannot be clarified as to whether or not a detected defect is present at the uppermost layer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a surface inspection apparatus and a surface inspection method that make it possible to judge as to whether or not a defect or the like detected in a surface inspection conducted on a test piece having patterns formed over numerous layers is present at the pattern at the uppermost layer.
A surface inspection apparatus according to the present invention is employed to inspect a surface of a test piece having a surface formed by stacking a plurality of pattern layers. This surface inspection apparatus comprises an illuminating optical system that irradiates illuminating light onto the surface of the test piece, an image-capturing device that captures an object image based upon diffracted light from the test piece, a condition control device that sets or changes an apparatus condition at which the o
Fukazawa Kazuhiko
Oomori Takeo
Yamamoto Mari
Adams Russell
Dalakis Michael
Nikon Corporation
Oliff & Berridg,e PLC
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