CN107894357B

CN107894357B - Automatic sample thinning method

Info

Publication number: CN107894357B
Application number: CN201711093467.5A
Authority: CN
Inventors: 周健刚; 曹秋凤; 龙吟; 王恺; 陈宏璘
Original assignee: Shanghai Huali Microelectronics Corp
Current assignee: Shanghai Huali Microelectronics Corp
Priority date: 2017-11-08
Filing date: 2017-11-08
Publication date: 2021-03-05
Anticipated expiration: 2037-11-08
Also published as: CN107894357A

Abstract

The invention relates to the technical field of semiconductors, in particular to an automatic sample thinning method; the method comprises the following steps: step S1, providing an initial sample with a defect; step S2, forming two grooves which take two parallel extension lines of two side edges of the defect as initial lines and extend towards two sides of the groove width on the surface of the initial sample avoiding the defect; step S3, filling two trenches with a metal different from the initial sample; step S4, thinning both sides of the sample filled with metal by adopting a focused ion beam process, and monitoring returned particle components in the thinning process in real time in the thinning process; step S5, stopping thinning operation when the ratio of the different metal components in the monitored particle components is lower than a preset value; the position that can accurate control focus ion cutting has improved the section precision, and degree of automation is high simultaneously, and is efficient, and the cost of labor is low, and the system appearance success rate is high.

Description

Automatic sample thinning method

Technical Field

The invention relates to the technical field of semiconductors, in particular to an automatic sample thinning method.

Background

As the integration level of integrated circuits is improved, the size of transistors in a chip is smaller and smaller, the minimum size of a CD is also continuously reduced, the sensitivity of devices to micro defects is gradually improved, and a failure analysis method is faced with an important challenge.

The use of focused ion beam defect detector slicing is a conventional means for failure analysis, and it is a great problem in the art how to ensure that a core region can be cut when a defect with a small size is encountered during sample preparation. In the prior art, the slicing position needs to be observed while slicing manually, the slicing position is very inaccurate, the automation degree is low, the labor cost is very high, and the efficiency is low. And the defect is not easy to be cut to the central position, and the sample preparation failure probability is higher.

Disclosure of Invention

Aiming at the problems, the invention provides an automatic sample thinning method which is applied to preparing a failure analysis sample; wherein, include:

step S1, providing an initial sample with a defect;

step S2, forming two grooves which take two parallel extension lines of two side edges of the defect as initial lines and extend towards two sides of the groove width on the surface of the initial sample avoiding the defect;

step S3, filling two trenches with a metal different from the initial sample;

step S4, thinning both sides of the sample filled with the metal by adopting a focused ion beam process, and monitoring returned particle components in the thinning process in real time in the thinning process;

and step S5, stopping thinning operation when the ratio of the different metal components in the particle components is lower than a preset value.

The sample thinning method, wherein the defect comprises a defect core and edge material surrounding the defect core;

in step S2, two parallel extended lines of the two side edges of the defect core of the defect are used as start lines.

In the sample thinning method, in step S4, the focused ion beam process is used to thin both sides of the sample filled with the metal, and the returned particle components in the thinning process are monitored in real time;

in the step S5, when it is detected that the ratio of the dissimilar metal components in the particle components on either side is lower than the preset value, the thinning operation on the corresponding side is stopped.

In the sample thinning method, the different metal is tungsten metal.

In the sample thinning method, the preset value is 0.

The sample thinning method is characterized in that the groove is a vertical groove.

In the sample thinning method, in step S5, the different metal components in the particle components are monitored by the primitive analyzer.

Has the advantages that: the automatic sample thinning method provided by the invention can accurately control the position of focused ion cutting, improves the slicing precision, and has the advantages of high automation degree, high efficiency, low labor cost and high sample preparation success rate.

Drawings

FIG. 1 is a flow chart of the steps of an automated sample thinning method in accordance with an embodiment of the present invention;

FIG. 2 is a schematic top view of a sample formed by an automated sample thinning method according to one embodiment of the invention;

fig. 3 is a perspective view of a system for automated sample thinning in accordance with an embodiment of the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

In a preferred embodiment, as shown in FIGS. 1 and 2, an automated sample thinning method is provided for preparing a failure analysis sample; wherein, can include:

step S1, providing an initial sample 1 with a defect 10;

step S2, forming two grooves which take two parallel extension lines of two side edges of the defect 10 as initial lines and extend towards two sides of the groove width on the surface of the initial sample 1 avoiding the defect 10;

step S3, filling a metal MT different from the initial sample in the two trenches;

step S4, thinning both sides of the sample filled with the metal MT by adopting a focused ion beam process, and monitoring returned particle components in the thinning process in real time in the thinning process;

in step S5, when the ratio of the different metal MT components in the monitored particle components is lower than a predetermined value, the thinning operation is stopped.

In the technical scheme, because the defects are the key for preparing the failure analysis sample, whether the defects can be clearly observed depends on whether the defects can be completely reserved when the failure analysis sample is prepared, and other structures and regions except the defects on the sample can be regarded as ineffective, so that the processing technologies such as groove etching, filling and the like can be carried out; the groove prepared by the invention is filled with metal MT which is different from the initial sample 1, so that the thinning position can be judged by tracking the returned particle components in the sample thinning process, and the automation of preparing the failure analysis sample is realized; the boundary of the trench towards the center line of the defect 10 is collinear with the side edge of the defect in the present invention to ensure that the side of the defect is just exposed when the metal MT in the trench is consumed, in which case the starting position of the cutting should be at the position where there is a heterogeneous metal MT; however, this is only one case, and it is also possible to prepare grooves of regular or irregular shape so that the content of heterogeneous metal MT in the returned particle composition is gradually changed; and the thinned sample formed after thinning is stopped can be used as a failure analysis sample.

In a preferred embodiment, the defect includes a defect nucleus 11 and a marginal substance 12 surrounding the defect nucleus 11;

in step S2, two parallel extended lines of the two side edges of the defect core 11 of the defect 10 are used as the start lines.

In the above technical solution, a general defect 10 includes a defect nucleus 11 and an edge substance 12, and the key of failure analysis is the defect nucleus 11, so the edge substance 12 needs to be removed.

In a preferred embodiment, in step S4, both sides of the sample filled with the metal MT are thinned by using a focused ion beam process, and the returned particle components during the thinning process are monitored in real time;

in step S5, when it is detected that the ratio of the different metal MT components in the particle components on either side is lower than a predetermined value, the thinning operation on the corresponding side is stopped.

In the above technical solution, the thinning of the two sides of the sample may be performed simultaneously or sequentially, but the monitoring of the particle components should be performed to distinguish the sides, so as to ensure that the two sides of the sample can be cut to the edge of the defect 10.

In a preferred embodiment, the dissimilar metal MT is tungsten metal and can be readily monitored by mass spectrometry.

In a preferred embodiment, the predetermined value is 0, but this is only a preferred case and other values are possible.

In a preferred embodiment, the trench is a vertical trench to ensure that the heterogeneous metal MT decays rapidly when consumed.

In a preferred embodiment, in step S5, a pristine analyzer is used to monitor the composition of the dissimilar metals in the composition of the particles.

In the above technical solution, the sample thinning method in the present invention may be implemented by using a system as shown in fig. 3, where the system may include:

a focused ion beam slicing unit 20 for thinning both sides of the sample having the trench filled with the metal MT;

a mass spectrometry unit 30 for monitoring the particle components generated when the focused ion beam slicing unit 20 thins the sample, generating and outputting component data reflecting the proportion of the components of the metal MT;

and the control unit 40 is respectively connected with the mass spectrum analysis unit 30 and the focused ion beam slicing unit 20 and is used for receiving and controlling the operation of the focused ion beam slicing unit 20 according to the composition data.

While the specification concludes with claims defining exemplary embodiments of particular structures for practicing the invention, it is believed that other modifications will be made in the spirit of the invention. While the above invention sets forth presently preferred embodiments, these are not intended as limitations.

Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. An automated sample thinning method is applied to preparing a failure analysis sample; it is characterized by comprising:

step S1, providing an initial sample with a defect;

step S3, filling two trenches with a metal different from the initial sample;

step S5, stopping thinning operation when the ratio of the different metal components in the monitored particle components is lower than a preset value;

in step S5, the components of the metals different from each other in the particle components are monitored by a mass spectrometer.

2. The method of claim 1, wherein the defect comprises a defect nucleus and a marginal substance surrounding the defect nucleus;

3. The sample thinning method according to claim 1, wherein in step S4, the focused ion beam process is used to thin both sides of the sample filled with the metal, and the returned particle components during the thinning process are monitored in real time;

4. The method of thinning a sample according to claim 1, wherein the dissimilar metal is tungsten metal.

5. The sample thinning method according to claim 1, wherein the trench is a vertical-type trench.