CN112912988A

CN112912988A - Focused ion beam system for large area substrates

Info

Publication number: CN112912988A
Application number: CN201980069961.9A
Authority: CN
Inventors: 伯纳德·G·穆勒
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2018-10-23
Filing date: 2019-10-07
Publication date: 2021-06-04
Also published as: KR20210074382A; TWI734216B; KR102618372B1; TW202030478A; WO2020083632A1

Abstract

A method and apparatus for cutting an electronic device is disclosed. In one embodiment, an apparatus for cutting electronic devices on a substrate is described, the apparatus comprising a stage for supporting a substrate having electronic devices thereon; a focused ion beam column fixed in a position above the platform, the focused ion beam column adapted to emit a beam path at an acute angle relative to a plane of a major surface of the substrate; and a microscope positioned adjacent to the focused ion beam column, wherein the stage is constrained to move in an X-Y plane during cutting by the electronics.

Description

Focused ion beam system for large area substrates

Background

FIELD

Embodiments of the present disclosure generally relate to a focused ion beam (focused ion beam) system for analyzing electronics on large area substrates. And more particularly, to a method and apparatus for analyzing Thin Film Transistors (TFTs) on a large area substrate on which a plurality of TFTs are formed.

Description of the Related Art

Electronic devices, such as thin film transistors, Photovoltaic (PV) devices, or solar cells, and other electronic devices, have been fabricated on large area substrates (e.g., thin, flexible media) for many years. The substrate may be made of glass, polymer, or other material suitable for forming an electronic device. There is a continuing effort to manufacture electronic devices on substrates having a surface area much greater than one square meter (e.g., two square meters or more) to produce larger size end products and/or to reduce the manufacturing cost per device (e.g., pixel, TFT, photovoltaic or solar cell, etc.).

It is often necessary to analyze discrete devices, such as thin film TFTs, that have been determined to be defective. For example, switching the transistor of an individual pixel may be defective, which results in this pixel being always on, or always off.

Focused Ion Beam (FIB) systems have been used as analytical techniques in the semiconductor industry, material science, and increasingly in the biological field. In the semiconductor industry, FIB systems use ion beams to perform site-specific analysis of a portion (e.g., "sample") of a die (die) on a wafer (wafer). The wafer (with the sample on the wafer) is attached to a movable stage. The platform is typically used to tilt and/or rotate the platform such that a major surface of the platform is at an angle of about 45 degrees with respect to a horizontal plane, such as the plane of a manufacturing facility floor (floor). Ions from the FIB system typically cut a two-dimensional rectangular shape in the sample, with the region of interest angled relative to the major surface of the wafer. The region of interest is then analyzed using a Scanning Electron Microscope (SEM).

However, large area substrates used for TFT fabrication are highly flexible at room temperature. This presents processing challenges that make conventional FIB systems and methods unusable.

There is a need for a method and apparatus that can use FIB technology for large area substrates.

SUMMARY

A method and apparatus for cutting an electronic device is disclosed. In one embodiment, an apparatus for cutting electronic devices on a substrate is described, the apparatus comprising a stage for supporting a substrate having electronic devices thereon; a focused ion beam column fixed in a position above the stage, the focused ion beam column adapted to emit a beam path at an acute angle relative to a plane of a major surface of the substrate, and a microscope positioned adjacent to the focused ion beam column, wherein the stage is constrained to move in an X-Y plane during cutting by the electronics.

In another embodiment, an apparatus for cutting an electronic device on a substrate is disclosed. The apparatus includes a stage for supporting a substrate having an electronic device thereon; a focused ion beam column fixed in position above the platform, the focused ion beam column adapted to emit a beam path and cut a three-dimensional notch in the electronic device; and a microscope positioned adjacent to the focused ion beam column, wherein the stage is constrained to move in an X-Y plane during cutting by the electronics.

In another embodiment, a method for cutting an electronic device on a substrate is disclosed. The method includes positioning a substrate on a stage; emitting a beam path from a focused ion beam column fixed at an angle of about 45 degrees relative to a major surface of a substrate; and moving the platform in a single transverse plane to create a three-dimensional recess in the electronic device.

Brief description of the drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of the scope of the disclosure, for other equivalent embodiments may be permissible.

Figure 1A is a schematic cross-sectional view of one embodiment of a focused ion beam system.

Fig. 1B is another schematic cross-sectional view of the focused ion beam system of fig. 1A.

Fig. 2A-2B depict an electronic device cut by conventional methods.

Fig. 3A-3C are various views of an electronic device cut by the methods and apparatus as disclosed herein.

Fig. 4 is a schematic cross-sectional view of a metering system.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

Detailed description of the invention

The present disclosure relates generally to a Focused Ion Beam (FIB) system for analyzing electronics on large area substrates. A large area substrate as used herein comprises a major surface having a surface area greater than one square meter, for example two square meters or more. FIB systems as described herein are illustratively disclosed for analyzing Thin Film Transistors (TFTs) on large area substrates. However, the FIB systems and methods as described herein can be used to analyze other electronic devices on large area substrates.

Fig. 1A is a schematic cross-sectional view of one embodiment of a Focused Ion Beam (FIB) system 100. Fig. 1B is another schematic cross-sectional view of the FIB system 100 of fig. 1A. The FIB system 100 shown in fig. 1A is performing a cutting process 105A in which a large area substrate 110 is cut (the large area substrate 110 has a transistor 115 on the large area substrate 110). The FIB system 100 shown in fig. 1B is performing an analysis mode 105B in which the cut transistor 115 is analyzed.

The large area substrate 110 is positioned on a stage 120. The platen 120 has a major surface 125, the major surface 125 supporting the large area substrate 110 in an orientation in which the plane of the major surface 125 is parallel to the Y-direction.

The stage 120 is movable at least in the lateral direction (in the X-direction and/or the Y-direction). The platen 120 supports the large area substrate 110 such that a major surface 130 of the large area substrate 110 is parallel to a major surface 125 of the platen 120. Thus, the plane 135 of the major surface 130 of the large area substrate 110 is parallel to the Y-direction.

The FIB system 100 also includes a Focused Ion Beam (FIB) column 140 that emits an ion beam. The FIB column 140 is supported such that a beam path 145 of the FIB column 140 is oriented at an angle a relative to the plane 135 of the major surface 130 of the large area substrate 110. The angle α of the beam path 145 relative to the plane 135 of the major surface 130 of the large area substrate 110 is acute, for example, about 40 degrees to about 50 degrees. In one example, the angle α is about 45 degrees relative to the plane 135 of the major surface 130 of the large area substrate 110.

The beam path 145 of the FIB column 140 is configured to cut a three-dimensional space 150 in the transistor 115 and/or the large area substrate 110. The three-dimensional space 150 is formed by moving the stage 120 laterally (in the X and Y directions) relative to the FIB column 140, the stage 120 having a large area substrate 110. The three-dimensional space 150 is cut in one plane (the X-Y plane).

FIB system 100 also includes a microscope 155. As shown in fig. 1B, a microscope 155 is used to analyze the three-dimensional space 150 of the transistor 115. The microscope 155 may be a scanning electron microscope having an observation path 160. The viewing path 160 is oriented at an angle normal to the plane 135 of the major surface 130 of the large area substrate 110.

After performing the dicing process 105A as shown and described in fig. 1A, the stage 120 is moved in the Y-direction so that the three-dimensional space 150 of the transistor 115 is located under the microscope 155, as shown in fig. 1B. In the analysis process 105B, the stage 120 can be moved laterally such that the viewing path 160 of the microscope 155 scans the three-dimensional space 150. In the three-dimensional space 150, a cross-section of the transistor 115 is visible to the microscope 155. For example, the source and drain regions, and the active layer(s), as well as the cross-section of the large area substrate 110 are visible to the microscope 155. During the cutting process 105A, the movement of the stage 120 may be limited to movement in the X-Y plane.

Fig. 2A-2B depict an electronic device 200 cut by conventional methods. Conventional methods tilt and/or rotate an underlying substrate (not shown) having electronics 200 thereon relative to a horizontal plane on a platform (not shown). The electronics 200 are also rotated and/or tilted relative to a fixed FIB column (not shown). The FIB column cuts the electronics 200 to create a two-dimensional notch 205. During this cut, the beam path (not shown) of the FIB column is at an angle of up to about 90 degrees relative to the major surface of the electronics 200.

The two-dimensional notch 205 is more clearly seen in the cross-sectional view of fig. 2B. The two-dimensional notch 205 includes a wall 210 on each side of an angled surface 215. The angled surface 215 is a flat surface that is typically viewed by a microscope (not shown). The surface roughness (average surface roughness, Ra) of the wall 210 has a high surface roughness because the wall 210 is not parallel to the FIB scanning direction, but the wall 210 is defined by the positions of the scanning start and end. The angled surface 215 roughness Ra may be about 5 nanometers to about 10 nanometers or more. The walls 210 are at a 90 degree angle relative to the major surface of the electronic device 200, and due to the steep viewing angle, the walls 210 are observable through the microscope with reduced resolution or image quality. Thus, the angled surface 215 is the only plane that can be observed with full microscope resolution and low surface roughness.

Fig. 3A-3C are various views of an electronic device 200 cut by methods and apparatus as disclosed herein. An apparatus for cutting an electronic device 200 is shown in fig. 1A.

According to embodiments described herein, the method of cutting the electronic device 200 produces a three-dimensional notch 300. The three-dimensional recess 300 is the same as the three-dimensional space 150 shown in fig. 1A and 1B. The three-dimensional recess 300 includes a plurality of angled surfaces, such as a first angled surface 305 and a second angled surface 310. The first angled surface 305 and the second angled surface 310 are planar surfaces viewed by a microscope (not shown). The first angled surface 305 and the second angled surface 310 may be adjacent to each other. Additionally, the three-dimensional recess 300 includes a single wall 315.

Each of the first angled surface 305 and the second angled surface 310 includes an angle 320. The angle 320 of both the first angled surface 305 and the second angled surface 310 may be the same. Angle 320 may be about 45 degrees. The single wall 315 may be at an angle of approximately 90 degrees relative to the major surface of the electronic device 200 and may not be observable through a microscope. The roughness (Ra) of the first angled surface 305 and the second angled surface 310 may be about 2 nanometers to about 0.1 nanometers or less.

Fig. 4 is a schematic cross-sectional view of a metering system 400. Metrology system 400 includes a vacuum chamber 405, vacuum chamber 405 having platform 120 described in fig. 1A and 1B within vacuum chamber 405. The platen 120 supports the large area substrate 110, and the large area substrate 110 has electronic devices (not shown) on the large area substrate 110. The vacuum chamber 405 is fluidly coupled with a vacuum pump 410, the vacuum pump 410 maintaining a negative pressure in the vacuum chamber 405.

The FIB column 140 and microscope 155 are at least partially positioned in a vacuum chamber 405 above the platform 120. Metrology system 400 also includes an auxiliary electron detector 415. The auxiliary electron detector 415 is used for imaging during cutting of the electronics using the FIB column 140.

The methods and apparatus described herein can cut an electronic device without tilting and/or rotating the electronic device and the underlying substrate. The methods and apparatus described herein also produce multiple surfaces that can be viewed by a microscope. The three-dimensional recess 300 as disclosed herein allows the source and drain regions, and the active layer, and a portion of the underlying substrate to be viewed in three dimensions in cross-section.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. An apparatus for cutting electronic devices on a substrate, the apparatus comprising:

a stage for supporting the substrate with the electronic device thereon;

a focused ion beam column fixed in position above the platform, the focused ion beam column adapted to emit a beam path at an acute angle relative to a plane of a major surface of the substrate; and

a microscope positioned adjacent to the focused ion beam column, wherein the stage is movable in an X-Y plane during cutting by the electronics.

2. The apparatus of claim 1, wherein the beam path cuts a three-dimensional notch in the electronic device.

3. The apparatus of claim 2, wherein the three-dimensional recess comprises a plurality of angled surfaces viewable through the microscope.

4. The apparatus of claim 3, wherein each of the plurality of angled surfaces is about 45 degrees relative to the plane of the major surface of the substrate.

5. The apparatus of any of claims 2 to 4, wherein the three-dimensional recess comprises a single wall that is not observable through the microscope.

6. The apparatus of claim 5, wherein the single wall is at an angle of approximately 90 degrees relative to the plane of the major surface of the substrate.

7. The apparatus of any of claims 1 to 6, wherein the microscope has a viewing path oriented at about 90 degrees relative to the plane of the major surface of the substrate.

8. An apparatus for cutting electronic devices on a substrate, the apparatus comprising:

a stage for supporting the substrate with the electronic device thereon;

a focused ion beam column fixed in position above the platform, the focused ion beam column adapted to emit a beam path and cut a three-dimensional notch in the electronic device; and

a microscope positioned adjacent to the focused ion beam column, wherein the stage is constrained to move in an X-Y plane during cutting of the electronics.

9. The apparatus of claim 8, wherein the microscope has a viewing path oriented at about 90 degrees relative to the plane of a major surface of the substrate.

10. The apparatus of any of claims 8 to 9, wherein the beam path is fixed at an acute angle relative to a plane of a major surface of the substrate.

11. The apparatus of any of claims 8 to 10, wherein the three-dimensional recess comprises a plurality of angled surfaces observable through the microscope.

12. The apparatus of claim 11, wherein each of the plurality of angled surfaces is about 45 degrees relative to the plane of the major surface of the substrate.

13. The apparatus of any of claims 8 to 12, wherein the three-dimensional recess comprises a single wall that is not observable through the microscope.

14. The apparatus of claim 13, wherein the single wall is at an angle of approximately 90 degrees relative to the plane of the major surface of the substrate.

15. The apparatus of any of claims 8 to 14, wherein the electronic device is a transistor.

16. A method for cutting an electronic device on a substrate, the method comprising:

positioning the substrate on a stage;

emitting a beam path from a focused ion beam column fixed at an angle of about 45 degrees relative to a major surface of the substrate; and

moving the platform in a single lateral plane to create a three-dimensional recess in the electronic device.

17. The method of claim 16, further comprising:

moving the platform adjacent to the microscope in the single transverse plane.

18. The method of claim 17, further comprising using the microscope to observe a plurality of angled surfaces in the three-dimensional recess.

19. The method of claim 18, wherein each of the plurality of angled surfaces is at an angle of approximately 45 degrees relative to the plane of the major surface of the substrate.

20. The method of any of claims 17 to 19, wherein the microscope has an observation path at an angle of about 90 degrees relative to the plane of the major surface of the substrate.