TWI893753B - Tool for preparation of tem sample - Google Patents

Abstract

A tool for preparation of TEM (transmission electron microscope) sample includes a mask body, which is disposed on a surface of an object under test, wherein the object under test has a target. The mask body has two windows, and a target definition area is formed between the two windows for blocking the target in the object under test, wherein an alignment mark is formed in the target definition area. The tool is easy to make and can quickly perform a large hole milling process to finish the preparation of TEM sample.

Description

Tools for TEM sample preparation

The present invention relates to a transmission electron microscopy (TEM) detection technology, and in particular to a tool for preparing TEM samples.

TEM inspection is one of the most commonly used techniques for testing semiconductor devices. Before TEM inspection, the object under test must be processed and prepared into a sample suitable for the TEM instrument. Currently, most TEM samples are prepared using a focused ion beam (FIB) to remove surrounding structures, exposing the target and thinning it to hundreds of nanometers for TEM analysis.

However, as the size of the objects being tested increases, for example, through-silicon vias (TSVs), commonly used in current semiconductor packaging technology, typically have depths of hundreds of microns. This results in increased time and cost for TEM sample preparation.

The present invention provides a tool for preparing TEM samples, which can be used to prepare a wide range of TEM samples while saving preparation time and cost.

The present invention provides a tool for preparing TEM samples, including a mask body for placement on the surface of an object to be tested, wherein the object contains a target. The mask body has two windows and a target definition region formed between the two windows for shielding the target in the object. Alignment marks are formed in the target definition region.

In one embodiment of the present invention, the hardness of the mask body is greater than that of silicon.

In one embodiment of the present invention, the thickness of the mask body is greater than 2 mm.

In one embodiment of the present invention, the width of the target definition area is less than 10 μm.

In one embodiment of the present invention, the alignment mark is located in the center of the target definition area for alignment of the broad ion beam (BIB) system.

In one embodiment of the present invention, the ratio between the width of each window and the width of the target definition area is between 100 and 200.

In one embodiment of the present invention, the ratio between the width and length of each window is between 1 and 2.

To make the above features of the present invention more clearly understood, the following examples are given and described in detail with reference to the accompanying drawings.

100: Mask body

102a, 102b: Window

104: Target Definition Area

106: Alignment Mark

300: Object under test

302: Target

304: Divergent ion beam

306: Big Hole

BIB: Divergent Ion Beam

l : length

t: thickness

w1, w2: width

FIG1 is a top view of a tool for preparing TEM samples according to one embodiment of the present invention.

Figure 2 is a perspective view of the tool used to prepare TEM samples in Figure 1.

Figures 3A to 3C are top-down views of the process for preparing TEM samples using the tool in Figure 1.

Figures 4A to 4C are cross-sectional views of the process for preparing TEM samples using the tool in Figure 1.

The present invention can be understood by referring to the following detailed description in conjunction with the accompanying drawings. Furthermore, the dimensions of the various regions in the drawings are for illustration only and are not intended to limit the scope of the present invention.

FIG1 is a top view of a tool for preparing TEM samples according to one embodiment of the present invention.

Referring to FIG. 1 , a tool for preparing a TEM sample includes a mask body 100 having two windows 102 a and 102 b. A target-defining region 104 is defined between the two windows 102 a and 102 b. During TEM sample preparation, the mask body 100 can be placed on the surface of an object to be tested (not shown), and the target-defining region 104 can shield a target (not shown) within the object. The so-called "target" is the object being analyzed by TEM. For example, when performing TEM analysis on semiconductor devices, the target is a chip or a stacked semiconductor package structure, such as a Chip-on-Wafer (CoW) or Wafer-on-Wafer (WoW), and the components therein, such as through-silicon vias (TSVs), are the target. An alignment mark 106 is also formed within the target definition area 104. For example, alignment mark 106 is positioned in the center of target definition area 104 to facilitate alignment by a divergent ion beam (BIB) system used in subsequent processing. Alignment mark 106 can be in the shape of a cross or other shapes. Because the BIB system can perform cutting quickly, it is suitable for preparing large-scale TEM samples, such as targets with depths exceeding 10μm. The following section describes the TEM sample preparation process in detail.

Continuing with FIG. 1 , the width w1 of the target definition area 104 of the mask body 100 can be set to less than 10 μm, for example, 1 μm, but the present invention is not limited thereto. The width w1 of the target definition area 104 can be wider or narrower depending on the size or depth of the target object. In one embodiment, the two windows 102a and 102b have the same area, but the present invention is not limited thereto. In other embodiments, window 102a can be slightly larger or smaller than window 102b. In addition, to facilitate TEM analysis, the ratio between the width w2 of each window 102a or 102b and the width w1 of the target definition area 104 is between 100 and 200, but the present invention is not limited thereto. The ratio between width w2 and width w1 can be even greater, that is, the width w2 of each window 102a or 102b is significantly greater than the width w1 of the target definition area 104. Furthermore, the ratio between the width w2 and the length l of each window 102a or 102b can be, for example, between 1 and 2, but the present invention is not limited thereto. Because the windows 102a or 102b are large, they can be opened in the original, solid mask body 100 via metal laser processing, eliminating the need for additional laser and etching processes to complete the mask fabrication.

Figure 2 is a perspective view of the tool for preparing TEM samples shown in Figure 1. In Figure 2, the mask body 100 can be made of a relatively hard material, essentially any material harder than silicon, such as titanium (Ti), but the present invention is not limited to this. In one embodiment, the thickness t of the mask body 100 is greater than 2 mm. However, the present invention is not limited to this. The thickness t of the mask body 100 depends on the hardness of the material. If a relatively hard material is used, the thickness t can be thinner. Conversely, if a material less hard than titanium is used, the thickness t may be greater than 2 mm, and so on.

The following describes how to use the tools in the above embodiment.

Figures 3A to 3C are top views of the process for preparing a TEM sample using the tool of Figure 1. Figures 4A to 4C are cross-sectional views of the process for preparing a TEM sample using the tool of Figure 1. In Figures 3 and 4, the same reference numerals as in the previous embodiment are used to represent the same parts and components. The details regarding the same parts and components can also be referred to in the previous embodiment, so they will not be repeated here.

Referring to Figures 3A and 4A , a mask body 100 is placed on the surface of an object under test 300, with a target-defining area 104 shielding a target 302 within the object under test 300. The object under test 300 is a semiconductor package structure, such as a CoW or WoW, consisting of a chip or wafer stack. The target 302 is a specific component or circuit, such as a TSV, formed therein. While the target 302 in Figure 3A is circular, it should be noted that this is merely an illustration of the target's location and that the target 302 could also be located within the object under test 300, rather than on the surface of the object as shown in Figure 4A.

Next, referring to both Figures 3B and 4B , a divergent ion beam (BIB) system is used to align the alignment mark 106 of the target definition area 104, allowing the BIB to align with the target 302 and perform the large hole removal process. The BIB's removal rate is approximately 1,000 times higher than that of conventional Ga ⁺ (gallium ion) focused ion beams (FIBs). Because the areas between the windows 102a and 102b and the mask body 100 create regions with different etch selectivities, only the areas exposed by the openings 102a and 102b are removed during the subsequent etching process.

Next, referring to Figures 3C and 4C , the large hole removal process forms a large hole 306 within the object under test 300. The depth of the large hole 306 can be determined by controlling the duration of the large hole removal process. Because the mask body 100 protects the target object 302 directly below it from etching, large-scale TEM sample preparation can be completed quickly.

Although the present invention has been disclosed above through embodiments, they are not intended to limit the present invention. Anyone with ordinary skill in the art may make minor modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

100: Mask body

102a, 102b: Window

104: Target Definition Area

106: Alignment Mark

l : length

w1, w2: width

Claims (6)

A tool for preparing TEM samples comprises: A mask body for placement on the surface of an object to be tested, wherein the object contains a target. The mask body has two windows, with a target definition region formed between the two windows to shield the target within the object. Alignment marks are formed in the target definition region for alignment with a broad ion beam (BIB) system. The ratio between the width of each window and the width of the target definition region is between 100 and 200. A tool for preparing TEM samples as described in claim 1, wherein the mask body has a hardness greater than silicon. A tool for preparing TEM samples as described in claim 1, wherein the thickness of the mask body is greater than 2 mm. The tool for preparing TEM samples as claimed in claim 1, wherein the width of the target definition area is less than 10 μm. A tool for preparing TEM samples as claimed in claim 1, wherein the alignment mark is located in the center of the target definition area. A tool for preparing TEM samples as described in claim 1, wherein the ratio between the width and length of each window is between 1 and 2.