1. Field of the Invention
The present invention relates to a measuring apparatus, a drawing apparatus including the same, and an article manufacturing method using the drawing apparatus.
2. Description of the Related Art
In recent years, as micronization of the element, increasingly complex circuit patterns, or a higher capacity of pattern data advance, the drawing accuracy of drawing apparatuses for use in the manufacturing of devices such as semiconductor integrated circuits need to be improved. As a method for realizing such requirements, a drawing apparatus that draws a pattern on a substrate by controlling the deflection scanning and blanking of a charged particle beam such as an electron beam or the like is known. Furthermore, as another method, a drawing apparatus that draws a pattern on a substrate by controlling the diffraction of a light beam as appropriate using an acoustic optical element is also known. In such a conventional drawing apparatus, the circuit pattern formed on one chip is typically divided into a plurality of regions and drawing is performed for each divided region. However, if there is positional error (drift or the like) of a beam, problems may occur at a boundary between the divided regions. When drawing is performed by superimposing the drawing pattern onto a pattern already formed on a substrate, deterioration of overlay accuracy may occur. Thus, in such a drawing apparatus, it is not preferable that a beam is misaligned with respect to a predetermined position. Accordingly, in order to counter beam positional error, a detection device for measuring the position of the beam on a stage is provided in the conventional drawing apparatus so as to measure beam positional error in advance for correction.
Here, micronization of circuit patterns has been advancing with a line width of 25 nm or less. In association with this, the size of the beam diameter also needs to be reduced. Thus, for example, a beam of Gaussian distribution having a half-width equivalent to a width of a requested line may be employed. In contrast, the position of the beam must be measured with the accuracy of 10% or less of a line width. More specifically, if a line width is in the range of from 25 to 50 nm, the position of the beam must be measured with the accuracy of 2 to 5 nm or less. Accordingly, Japanese Patent Laid-Open No. 10-106931 discloses the fact that a plurality of electron beams is incident in the longitudinal direction of the edge of a detection device so as to obtain a signal having a sufficient SN ratio from a sensor. Additionally, since an error in the position of the edge of the detection device becomes a measurement error in the position of a charged beam, Japanese Patent Laid-Open No. 10-64799 discloses the fact that the result of measurement of the position of the beam is corrected by measuring the position error.
However, in order to ensure position measurement with the accuracy of a few nm level, the roughness of the edge of the detection device need to be taken into consideration in addition to the deformation of the detection device due to heat and force, and electrical drift. For example, when the shape, position, or intensity of the beam is measured using a knife-edge method, the influence of the roughness of the edge cannot be ignored if the half-width of the beam decreases to the level of 11 to 22 nm. In other words, in the devices disclosed in Japanese Patent Laid-Open No. 10-106931 and Japanese Patent Laid-Open No. 10-64799, the roughness of the edge is sufficiently small with respect to the shape or size of the beam to be measured, and thus, the influence of the roughness thereof can be ignored. In contrast, in a recent drawing apparatus that draws a pattern with a line width of 50 nm or less, 2 nm roughness (unevenness) of the edge causes a measurement error of 2 nm at maximum in the position of a beam, and thus, the influence of the roughness thereof cannot be ignored. For example, when the change over time in the position of the beam is measured for correction, a measurement error may consequently affect on drawing accuracy and overlay accuracy.