Back to results
US 6,646,751 B2Granted
Apparatus and method for measuring trench depth
AssigneeNEC Electronics Corporation
InventorMichifumi Kishimura
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeNEC Electronics Corporation
InventorMichifumi Kishimura
Estimating the term…
A method for measuring the depth of a subject trench includes the steps of forming on a substrate a plurality of measurement trenches having different widths aj (ai<aj+1, i=1, 2, . . . , n) and a depth equal to the depth d0 of the subject trench, irradiating the measurement trenches with a parallel ray at an incidence angle of θ with respect to the substrate surface while detecting the reflected ray from the substrate, separating the measurement trenches into a first group providing dark images and a second group providing bright images, and calculating a range for the depth d0 by using a largest width ak of the measurement trenches in the first group and a smallest width ak+1 of the measurement trenches in the second group based on the following relationship: (ak/2)tan θ<d0≦(ak+1/2)tan θ.
A method for measuring a depth of a subject trench comprising the steps of forming, on a substrate, a plurality of measurement trenches having different widths ai (ai<ai+1, i=1, 2,. . . , n) and a depth equal to the depth d0 of the subject trench, irradiating the measurement trenches with a parallel ray at an incidence angle of θ with respect to the surface of the substrate while detecting the reflect ray from the substrate, separating the measurement trenches into a first group providing dark images and a second group providing bright images, and calculating a range for the depth d0 by using a largest width ak of the measurement trenches in the first group and a smallest width ak+1 of the measurement trenches in the second group based on the following relationship:
A method for measuring a depth of a subject trench comprising the steps of preparing a plurality (M) of reference image patterns each formed from a plurality (N) of reference trenches having different widths of aj (aj<aj+1, j=1, 2, . . . N) and a common depth selected from M different depths of dh (dh<dh+1, h=1, 2, . . . M) by using a parallel ray irradiated at an incidence of θ with respect to the surface of a reference substrate having the reference trenches, forming, on a measurement substrate, a plurality of measurement trenches having different width ai (ai<ai+1, i=1, 2, . . . n) and a depth equal to the depth d0 of the subject trench, irradiating a parallel ray at an incidence angle of θ with respect to the surface of the measurement substrate while detecting the reflected ray from the measurement substrate, detect a boundary width between the widths of a first group of the measurement trenches providing dark images and the widths of a second group of the measurement trenches providing bright images, and selecting, for the depth d0, the depth of the plurality of reference trenches which provide one of the reference image patterns having a boundary width corresponding to the boundary width detected from the measurement trenches.
An apparatus for measuring a depth of a subject trench comprising a light source for irradiating light to a substrate having a plurality of measurement trenches at an incidence angle of θ with respect to a substrate surface, said measurement trenches having a plurality of widths and a depth equal to the depth of the subject trench, a CCD camera for detecting the images of the measurement trenches in the reflected light from the substrate to output an image signal, and a processing unit for calculating the depth d0 of the subject trench based on the image signal from the CCD camera, by separating the measurement trenches into a first group providing dark images and a second group providing bright images, and calculating a range for the depth d0 by using a largest width ak of the measurement trenches in the first group and a smallest width ak+1 of the measurement trenches in the second group based on the following relationship:
An apparatus for measuring a depth of a subject trench comprising a storage device for storing a plurality of reference image patterns each formed from a plurality (M) of reference trenches having different widths of aj (aj<aj+1, j=1, 2, . . . N) and a common depth selected from M different depths of dh (dh<dh+1, h=1, 2, . . . M), a light source for irradiating light to a substrate having a plurality of measurement trenches at an incidence angle of θ with respect to the substrate surface, the measurement trenches having a plurality of widths and a depth equal to the depth of the subject trench, a CCD camera for detecting the images of the measurement trenches in the reflected light from the substrate to output an image signal, and a processing unit for calculating the depth d0 of the subject trench based on the image signal from the CCD camera by detecting a boundary width between the widths of a first group of measurement trenches providing dark images and the widths of a second group of measurement trenches providing bright images, and selecting, for the depth d0, the depth of the plurality of reference trenches which provide one of the reference image patterns having a boundary width corresponding to the boundary width detected from the measurement trenches.
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
From the US filing history. Foreign family members aren’t listed.
Measuring arrangements characterised by the use of optical techniques: for measuring depth
Characterised by the properties tested or measured, e.g. structural or electrical properties: structural properties, e.g. testing or measuring…
Measuring length, thickness or similar linear dimensions
Generic processes or apparatus for the manufacture or treatment of devices covered
Term ended 26 Apr 2022 (estimated)
(a) Field of the Invention
The present invention relates to an apparatus for measuring a trench depth and, more particularly, to an apparatus for measuring the depth of a trench, groove or hole (collectively referred to as “trench” in this text) formed on a semiconductor wafer etc. The present invention also relates to a method for measuring the depth of such a trench.
(b) Description of the Related Art
FIG. 1 is a schematic side view of a conventional apparatus for measuring the depth of a trench.
FIGS. 2A2B and 2C are schematic diagrams each showing the principle of the present invention by illustrating sectional views of a plurality of trenches having different widths and depths and corresponding optical images obtained therefrom.
FIG. 3 is an enlarged schematic diagram showing a sectional view of a plurality of trenches and corresponding optical images obtained therefrom by a method according to an embodiment of the present invention.
Before describing preferred embodiments of the present invention, the principle of the present invention is described.
Referring to FIGS. 2A, 2B and 2C there are shown different cases of dark images and bright images being obtained from trenches based on the reflected light depending on the depths and widths of the trenches. These figures in fact show an example of reference trenches and reference obtained therefrom.
In each of FIGS. 2A, 2B and 2C, a plurality of trenches 40 having specified widths a1, a2 and a3 (a1<a2<a3) and a depth d1, d2 or d3, (d1<d2<d3) are formed and arranged in the ascending order of the widths for each of the depths on a single substrate 31. A parallel ray 32 is incident onto the substrate 31 including the trenches 40 at an incidence angle of θ (acute angel) with respect to the substrate surface. The reflected ray 33 from the substrate 31 is observed and the observed images 41 and 42 are shown below the respective trenches 40. If the light reflected from the bottom of a trench is blocked by the wall of the same trench due to a larger depth or smaller width, the resultant image is dark. On the other hand, if the light reflected from the bottom is detected by the optical sensor without blockage by the wall due to a smaller depth or larger width, the resultant image is bright.