Method for enhancing the measuring accuracy when determining the coordinates of structures on a substrate

#This claims the benefit of German patent application DE 10 2006 023 150.3 filed May 16, 2006 and of German patent application DE 10 2007 018 115.0 filed Apr. 16, 2007, and hereby incorporated by reference herein.

#The present invention relates to a method for enhancing the measuring accuracy in determining the coordinates of structures on a substrate. To determine the coordinates of structures, at least one laser interferometer system is provided for determining the position shift of the substrate in at least one spatial direction (X coordinate direction and/or Y coordinate direction). The laser interferometer system together with the substrate is accommodated in a climate chamber.

#A measuring device as used for measuring structures on wafers and masks used for their manufacture has been disclosed in the paper entitled “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The paper was held at the Semicon Education Program Convention in Geneva on Mar. 31, 1998. The description given there is the basis for the Leica LMS IPRO coordinate measuring device of the present applicant. For details and the operation and for the construction of the measuring device, the above mentioned publication, and the commercially available LMS IPRO3 and LMS IPRO2 models are explicitly referred to.

#Exemplary embodiments of the invention and their advantages will be described in the following with respect to the accompanying drawings in more detail.

#FIG. 1 schematically shows a coordinate measuring device, in which the position measuring method according to the present invention can be advantageously used;

#FIG. 2A shows the repeatability of the X coordinate direction in a measuring system according to FIG. 1, wherein the coordinate positions of a 15×15 grid are indicated for nine measuring passes, wherein for better detection of the repeatability, the average value of all nine measuring passes is subtracted from all positions at each grid position;

#A coordinate measuring device of the type shown in FIG. 1 has already been explained in detail in the introductory portion of the description.

#The repeatability or reproducibility of such a coordinate measuring device is usually determined by measuring a measurement grid of 15 by 15 points (measuring area 6 inches, 152×152 mm). The value of the threefold standard deviation (3σ) is typically determined after 20 measurements for the coordinates obtained in the X and Y coordinate directions. The maximum value of this threefold standard deviation represents the repeatability and therefore the machine performance. The measurement is carried out on standard substrates in the factory, wherein a plurality of identical and regularly arranged structures are measured by means of the standard substrate.

#If the measurements are made locally on a defined mask position, i.e. in this case the X/Y measuring stage is not traversed, this is an indication for short-term reproducibility. This measurement gives an indication on the repeatability within a short period of time (so-called needle test).