DD286041A5 - METHOD FOR SPACING DEFINITION IN MEASURING SMALL DIMENSIONS - Google Patents

Abstract

The invention relates to a method for defining the distance when measuring small structures and thus serves in particular for the quantitative evaluation of the structuring of microelectronic components. The method makes it possible to assign relevant points of the signal curve to specific geometrical surface details, even if the signal curve is varied in the major order of the relevant points, and allows the distance definition by selecting the relevant points of the signal curve corresponding to defined geometric surface details. This is achieved by identifying the corresponding relevant points of the signal curve by defining a dominant position within the signal curve. Fig. 1 {Meszverfahren; Distance definition; Oberflaechendetails; geometric shapes; relevant jobs; Extreme values; Signal curve; Signalintensitaet; spatial coordinate; interfaces}

Description

The invention is advantageously configured in that the relevant points of the signal curve for the Abstanddefinit on by awarding the distance and a tolerance range left or right of the dominant point of the signal curve and the search for a lying in this tolerance range extreme value or a suitably defined curve piece, be determined.

AusfOhrungsbelsplef The invention is based on an embodiment shown below with light-optical measuring method in more detail

be explained.

The figure shows the surface of a wafer with surface structures and the associated signal curve. To Abs'andsdefinitlon in the evaluation of these structures, the signal curve is recorded and stored in a computer for the

saved further evaluation. In connection with the measured value detection, a preprocessing of the measuring signals by accumulation, smoothing by filtering or other methods can be carried out.

As a starting point for further evaluation, a part or even several parts of the signal curve, which is a dominant point

or form dominant points within the signal curve. This dominant position within the signal curve is an image of details of the surface of the test object to be examined and is always recognizable under changed measuring conditions. However, the dominant position of the signal curve and the surface detail of the object to be measured must not be relevant to the actual distance definition. This dominant position can also be localized by the appearance of a larger dimentional section of global extreme value. The dominant point serves as a reference mark in the selection of relevant for the measurement tasks bodies with the help then a distance definition of the relevant bodies to be assigned surface details of the DUT can be done.

The selection of the relevant points for the measurement task can be done either by counting the extreme values or other suitable Curves, left and right of the dominant point of the signal curve up to the relevant point, as well as by specifying a Distance and tolerance range left or right of the dominant point of the signal curve, done. The evaluation program selects the signal curve as the extreme values, in the vicinity of

predetermined width in the X-coordinate, both right and left a predetermined number of intensity values of successive elementary sections of the signal curve is located by a predetermined amount below (the

Maximum) or above (the minimum) of the intensity at the point under consideration, or in other known manner

can be selected. The size of the elementary sections of the signal curve is determined by the quantization of the

Measured value recording with respect to the X-coordinate specified. The distance definition determined from relevant points according to the methods described can be transferred in a known manner via Multiplication and addition of correction terms are matched to the real conditions on the DUT. The trenches a, b and d shown in the drawing FIG. 1 have smaller dimensions with respect to the trench c

their trench width. The coarser trench c in the example gives the dominant position (global minimum), while the rest

Trenches produce the weaker secondary extras (minima). The right half of the displayed area of the Wafers have lower reflectivity than the left. The measuring task is to determine the distance between the trenches a and d. The relevant places are the Minima A and D. The dominant point of the signal curve is the minimum C. According to the invention, the relevant points A

and D selected by the rule:

1. Let A be the second minimum to the left of C, let D be the first minimum to the right of C or

2. Let A be the minimum (X 1 +/- delta 1) to the left of C, let D be the minimum around the distance (X 2 +/- delta 2) to the right of C.

Claims (2)

1. A method for distance definition when measuring small dimensions by displaying and evaluating a corresponding with the surface structure of the measurement object, corresponding to the surface detail of the measurement object relevant points having signal curve, characterized in that the relevant points of the signal curve for the distance definition by counting the extreme values or other suitable defined curve pieces, left or right of a dominant position of the signal curve, starting from this dominant point, are determined. 2. The method according to claim 1, characterized in that the relevant points of the signal curve for the distance definition by specifying the distance and a tolerance range left or right of the dominant point of the signal curve and the search for a lying in this tolerance range extreme value, or suitable for one defined curve piece can be determined. For this 1 page drawing Field of application of the invention The invention relates to a method for defining the distance when measuring small dimensions on a mechanical, light-optical or electron-optical basis for the measurement of dimensions in the μην and sub-pm range, in particular for the quantitative evaluation of the structuring of microelectronic components. Characteristic of the known state of the art For measuring small dimensions, for example on a wafer surface, the surface of the wafer provided with structures is imaged into an intermediate image plane and this image is scanned with a gap and optical receivers located behind it. In this way, the dependence of the signal intensity on the location coordinate is determined. The resulting signal curve is stored in a computer and further evaluated by programs. For this purpose, relevant points of the signal curve, such as extreme values, interfaces with threshold lines, interfaces of regression lines, points of the signal curve to be determined among individual curve pieces and those to be determined by the operator, are assigned interesting surface details, such as geometric edges or discontinuities of material properties, for the measurement become. In this way, the distance between surface details of interest for a plurality of DUTs having the same surface finish can be routinely checked and measured when the signal curves of the DUT images are at least similar. For this it is necessary for the same measurement program, that the selection of the relevant points for the measurement of the signal curve refers to the limitation of the selected for measurement image detail or the intersections of the signal curve with the threshold line. Particularly in the case of an automatic measurement sequence on a plurality of similar DUTs one behind the other, in which the surface structure has signal curve-changing O smiles, the signal curves of similar DUTs are subject to variations. Thus, the same parts of the signal curve corresponding to the particular surface details of the measurement object are not identified as belonging to these surface details. The resulting erroneous measurements occur vqr all things then when between the selected for measurement defined surface details of the object to be measured and in the signal curve corresponding training relevant points more places, for example in the form of extreme values, in about the same order of magnitude as those with measuring surface details corresponding to relevant sites. ZIoI the invention The aim of the invention is to provide a method for distance definition when V _ ^a n smaller dimensions of an assignability of relevant locations of the waveform to certain geometrical surface details, even with variation of the Signaikurve in the order of the relevant points caused du is: ch unpredictable Changes to the surface finish of the DUT, guaranteed. Explanation of the essence of the invention The invention is based on the object of specifying a method for defining the distance when measuring small dimensions, which makes it possible to select the relevant points of the signal curve corresponding to certain geometric surface details. This object is achieved by the method for distance definition when measuring small dimensions by displaying and evaluating a corresponding with the surface structure of the DUT, according to the surface detail of the object relevant points relevant points signal curve according to the invention, that the relevant points of the signal curve for the distance definition by counting the extreme values or other suitably defined curve pieces, left or right of a dominant position of the Signalalku / ve, starting from this dominant point, are determined.