阅读说明：本技术 弹性模式扫描光学显微术及检验系统 (Elastic mode scanning optical microscopy and inspection system ) 是由 萨姆尔·班纳 吴冬 梅迪·瓦泽-艾拉瓦尼 瓦赫布·比沙拉 于 2018-05-09 设计创作，主要内容包括：一种用于弹性检验样品的方法包括以下步骤：使用射束源形成输入射束；使用输入掩模来阻挡所述输入射束的一部分；及从所述输入射束的一部分形成定形射束。在物镜的第一部分处接收所述定形射束及将所述定形射束聚焦到样品上。在所述物镜的第二部分处收集反射射束。在所述物镜的所述第一部分及所述第二部分处及在所述物镜的第三部分处收集散射光。在暗视野检测器模块处接收所述散射光,且将所述散射光的一部分引导到暗视野检测器。所述暗视野检测器模块包括具有一或多个输出孔的输出掩模,所述一或多个输出孔允许所述散射光穿过所述物镜的所述第三部分的至少一部分穿过而作为所述散射光被引导到所述暗视野检测器的所述部分。(A method for elastically inspecting a sample comprising the steps of: forming an input beam using a beam source; blocking a portion of the input beam using an input mask; and forming a shaped beam from a portion of the input beam. The shaped beam is received at a first portion of an objective lens and focused onto a sample. Collecting a reflected beam at a second portion of the objective lens. Collecting scattered light at the first and second portions of the objective lens and at a third portion of the objective lens. The scattered light is received at a dark field detector module and a portion of the scattered light is directed to a dark field detector. The dark field detector module includes an output mask having one or more output apertures that allow the scattered light to pass through at least a portion of the third portion of the objective lens to be directed to the portion of the dark field detector as the scattered light.)

1. A system for bright field and dark field inspection of a sample, the system comprising:

a source configured to provide an input beam;

an input mask having an input aperture, the input mask configured to block a portion of the input beam and the input aperture arranged to allow a portion of the input beam to pass through as a shaped beam;

an objective lens arranged to:

receiving the shaped beam and focusing the shaped beam onto a sample at a first oblique angle, the shaped beam passing through a first portion of the objective lens;

collecting a reflected beam that is a portion of the shaped beam reflected at a second oblique angle from the sample, the reflected beam passing through a second portion of the objective lens; and

collecting scattered light, the scattered light being a portion of the shaped beam scattered by the sample, the scattered light passing through the first and second portions of the objective lens and a third portion of the objective lens, wherein the first, second and third portions of the objective lens comprise different portions of the objective lens;

a bright field detector module configured to receive the reflected beam from the objective lens and direct the reflected beam to a bright field detector; and

a dark field detector module configured to receive the scattered light from the objective lens and direct a portion of the scattered light to a dark field detector, the dark field detector module comprising an output mask having one or more output apertures, the output mask configured to block the scattered light from passing through the first and second portions of the objective lens, and the one or more output apertures arranged to allow the scattered light to pass through at least a portion of the third portion of the objective lens to be directed to the portion of the dark field detector as the scattered light.

2. The system of claim 1, wherein the first oblique angle is an oblique angle of incidence.

3. The system of claim 1, wherein the first, second, and third portions of the objective lens are non-overlapping.

4. The system of claim 1, wherein the first, second, and third portions of the objective lens correspond to an entire numerical aperture of the objective lens, or wherein the first, second, and third portions of the objective lens correspond to less than an entire numerical aperture of the objective lens.

5. The system of claim 1, wherein the third portion of the objective lens comprises a portion of the objective lens that is outside of a plane of incidence of the shaped beam.

6. The system of claim 1, further comprising:

a beam expander for expanding the input beam;

a collimator for collimating the input beam;

a polarizer for polarizing the shaped beam; and

one or more beam splitters for separating at least a portion of the scattered light from the reflected beam.

7. A system for elastically inspecting a sample, the system comprising:

a source configured to provide an input beam;

an input mask having an input aperture, the input mask configured to block a portion of the input beam and the input aperture arranged to allow the portion of the input beam to pass through as a shaped beam;

an objective lens arranged to:

receiving the shaped beam and focusing the shaped beam onto a sample, the shaped beam passing through a first portion of the objective lens;

collecting a reflected beam, the reflected beam being a portion of the shaped beam reflected from the sample, the reflected beam passing through a second portion of the objective lens; and

collecting scattered light, the scattered light being a portion of the shaped beam scattered by the sample, the scattered light passing through the first and second portions of the objective lens and through a third portion of the objective lens, wherein the first and second portions of the objective lens are different from the third portion of the objective lens;

a bright field detector module configured to receive the reflected beam from the objective lens and direct the reflected beam to a bright field detector; and

a dark field detector module configured to receive the scattered light from the objective lens and direct a portion of the scattered light to a dark field detector, the dark field detector module comprising an output mask having one or more output apertures, the output mask configured to block the scattered light from passing through the first and second portions of the objective lens, and the one or more output apertures arranged to allow the scattered light to pass through at least a portion of the third portion of the objective lens to be directed to the portion of the dark field detector as the scattered light.

8. The system of claim 7, wherein the first and second portions of the objective lens comprise substantially identical portions of the objective lens, or wherein the first and second portions of the objective lens comprise different portions of the objective lens.

9. The system of claim 7, wherein the shaped beam is focused onto the sample at normal incidence, and wherein the output mask blocks the scattered light passing through a center of the objective lens.

10. The system of claim 7, further comprising:

a beam expander for expanding the input beam;

a collimator for collimating the input beam;

a polarizer for polarizing the shaped beam; and

one or more beam splitters for separating at least a portion of the scattered light from the reflected beam.

11. A method for elastically inspecting a sample, the method comprising the steps of:

forming an input beam using a beam source;

blocking a portion of the input beam using an input mask;

forming a shaped beam from a portion of the input beam that passes through an aperture in the input mask;

receiving the shaped beam at an objective lens and focusing the shaped beam onto a sample, the shaped beam passing through a first portion of the objective lens;

collecting a reflected beam at the objective lens, the reflected beam being a portion of the shaped beam reflected from the sample, the reflected beam passing through a second portion of the objective lens;

receiving the reflected beam at a bright field detector module and directing the reflected beam to a bright field detector;

collecting scattered light at the objective lens, the scattered light being a portion of the shaped beam scattered by the sample, the scattered light passing through the first and second portions of the objective lens and through a third portion of the objective lens, wherein the first and second portions of the objective lens are different from the third portion of the objective lens; and

receiving the scattered light at a dark field detector module, and directing a portion of the scattered light to a dark field detector, the dark field detector module comprising an output mask having one or more output apertures, the output mask blocking the scattered light passing through the first and second portions of the objective lens, and the one or more output apertures allowing the scattered light to pass through at least a portion of the third portion of the objective lens to be directed to the portion of the dark field detector as the scattered light.

12. The method of claim 11, wherein the first and second portions of the objective lens comprise substantially identical portions of the objective lens, or wherein the first and second portions of the objective lens comprise different portions of the objective lens.

13. The method of claim 11, wherein the shaped beam is focused onto the sample at normal incidence or oblique incidence.

14. The method of claim 11, wherein the output mask blocks the scattered light that passes through a center of the objective lens.

15. The method of claim 11, further comprising the steps of:

after receiving the reflected beam at the bright-field detector module and the scattered light at the dark-field detector module:

blocking a second portion of the input beam using a second input mask;

forming a second shaped beam from a portion of the input beam that passes through a second aperture in the second input mask;

receiving the second shaped beam at the objective lens and focusing the second shaped beam onto the sample, the second shaped beam passing through a fourth portion of the objective lens, the fourth portion being different from the first portion of the objective lens;

collecting a second reflected beam at the objective lens, the second reflected beam being a portion of the second shaped beam reflected from the sample, the second reflected beam passing through a fifth portion of the objective lens, the fifth portion being different from the second portion of the objective lens;

collecting second scattered light at the objective lens, the second scattered light being a portion of the second shaped beam scattered from the sample, the second scattered light passing through the fourth and fifth portions of the objective lens and through a sixth portion of the objective lens, wherein the fourth and fifth portions of the objective lens are different from the sixth portion of the objective lens;

receiving the second reflected beam at the bright field detector module and directing the second reflected beam to the bright field detector;

receiving the second scattered light at the dark field detector module and directing a portion of the second scattered light to the dark field detector, the dark field detector module comprising a second output mask having one or more second output apertures, the second output mask blocking the second scattered light that passes through the fourth portion and the fifth portion of the objective lens, and the one or more second output apertures allowing the second scattered light to pass through at least a portion of the sixth portion of the objective lens as the second scattered light to be directed to the portion of the dark field detector.

Technical Field

Embodiments described herein relate generally to systems and methods for optical microscopy and inspection.

Background

The basic goal of microscopy and inspection is to produce contrast from an object under examination on a point-by-point basis. Without comparison, nothing can be distinguished. In this context, the notion of point-by-point refers to the viewing limit determined by the resolution of the system.

The need to provide sufficient contrast to discern details has led to the development of many useful testing techniques. Examples include dark field microscopy, phase contrast imaging, interferometric phase contrast microscopy, and Schlieren photography.

Within each of these technologies, there are many variations, each designed for a specific purpose or situation. Different technologies or variations may provide different information. Thus, a variety of techniques or variations are commonly used to inspect objects. This is particularly true when the sample under examination exhibits characteristics in one region that favor one imaging modality and in another region that favor a different imaging modality.

The use of scattered light is particularly useful in certain applications for various forms of imaging techniques. The scattered light gives rise to a signal which is essentially a dark field (dark-field). If the sample is homogeneous in composition and morphology, there is no mechanism for scattering the illumination light. Defects or variations, on the other hand, can scatter illumination light and provide dark field signals.

Dark field imaging can be used to detect small changes in an otherwise uniform ambient environment. As one example, dark field imaging may be used to inspect semiconductor device structures for minute defects, which may take the form of: particles on the surface, imperfections in an otherwise perfect (or nearly perfect) array, microscopic bumps (or mouse-bits) in a linear structure, or other defects. It is often difficult to resolve these defects in bright field mode because the signals from surrounding structures are often so strong that they overwhelm the finer signals from small defects. Using dark field imaging in this case allows for the elimination of most of the bright background so that scattered light from the defect can be detected.

There are two main types of dark field microscopy, distinguished by their illumination techniques, one using forward illumination incidence and the other using oblique illumination incidence. In the former, light scattered toward an area surrounding the illumination aperture is collected. This mode is commonly referred to as gray-field imaging due to the proximity of scattered light to the illuminating light.

Oblique incidence techniques may be single or double dark field. If scattered light is collected at the plane of incidence, it is referred to as a single dark field. If the scattered light is collected outside the plane of incidence to the side, i.e., if the collection space is different from the illumination space in both the polar and azimuthal directions (i.e., collected from above and below the sample plane and along different angular directions about a direction perpendicular to the sample), then it is referred to as a double dark field.

Conventional oblique incidence dark field imaging systems use separate components for illumination and collection. For example, illumination is typically performed by the focusing action of a lens held at an angle relative to the sample, while collection is typically performed by a separate lens. Such systems require separate illumination and collection components arranged in fixed positions. These components occupy a certain amount of the available Numerical Aperture (NA) space above the sample. As such, the NA allocated to illumination is limited. This limits resolution because the interrogation spot size (interrogation spot size in the linear dimension) is inversely proportional to NA. Also, the use of components that are fixed in place constrains the collection space to a specific area. Accordingly, there is a need for improved systems and methods with increased flexibility.

Disclosure of Invention

In view of the foregoing, systems and methods for optical microscopy and inspection are provided for elastic inspection samples. In one embodiment, for example, an inspection system includes an input mask that allows a shaped beam to pass through a portion of an objective lens where the shaped beam is focused on a sample. The beam reflected from the sample passes through a portion of the objective lens and is directed to a bright field detector. A portion of the scattered light that passes through the other portion of the objective lens is directed to a dark field detector. Thus, the objective lens in this embodiment may be used to focus the input beam onto the sample and collect reflected and scattered light from the sample.

According to one embodiment, a method for elastically inspecting a sample includes the steps of: forming an input beam using a beam source; blocking a portion of the input beam using an input mask; and forming a shaped beam from a portion of the input beam. The shaped beam is the portion of the input beam that passes through an aperture in the input mask. The shaped beam is received at an objective lens and focused onto a sample. The shaped beam passes through a first portion of the objective lens. Collecting the reflected beam at the objective lens. The reflected beam is a portion of the shaped beam reflected from the sample. The reflected beam passes through a second portion of the objective lens. The reflected beam is received at a bright field detector module and directed to a bright field detector. Scattered light is collected at the objective lens. The scattered light is a portion of the shaped beam scattered by the sample. The scattered light passes through the first and second portions of the objective lens and through a third portion of the objective lens. The first and second portions of the objective lens are different from the third portion of the objective lens. The scattered light is received at a dark field detector module and a portion of the scattered light is directed to a dark field detector. The dark field detector module includes an output mask having one or more output apertures. The output mask blocks the scattered light that passes through the first and second portions of the objective lens. The one or more output apertures allow the scattered light to pass through at least a portion of the third portion of the objective lens to be directed to the portion of the dark field detector as the scattered light.

Drawings

A full understanding of the various embodiments described herein (both as to structure and method of operation) as well as the features and advantages thereof may be realized by reference to the following detailed description and the accompanying drawings, in which:

FIG. 1 is a simplified cross-sectional view of a spring-mode scanning optical microscopy and inspection system according to one embodiment;

FIGS. 2a-2e are simplified plan views of an objective lens aperture according to certain embodiments, each illustrating how different regions of the objective lens aperture are used to direct light toward and collect light from a sample;

FIG. 3 is a simplified cross-sectional view of a spring-mode scanning optical microscopy and inspection system according to another embodiment;

FIG. 4 is a simplified plan view of an objective lens aperture showing how different objective lens aperture regions may be used to direct light to and collect light from a sample, according to one embodiment; and

FIG. 5 is a flow chart summarizing a method for elastically inspecting a sample, according to one embodiment.

It will be appreciated that for ease and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

Embodiments are also directed to apparatuses for carrying out the disclosed methods and including apparatus components for performing each of the method features. The method features may be performed by hardware components, a computer programmed by appropriate software, by any combination of the two, or in any other way. Also, embodiments are directed to methods of operating the devices and include method features for implementing each function of the device.

Further aspects, advantages and features are apparent from the claims, the description and the drawings.