CN102426119A

CN102426119A - Preparation method of structure section sample of small-sized wafer sample for observation

Info

Publication number: CN102426119A
Application number: CN2011102450095A
Authority: CN
Inventors: 张涛
Original assignee: SHANGHAI FAILURE ANALYSIS LABORATORY Co Ltd
Current assignee: SHANGHAI FAILURE ANALYSIS LABORATORY Co Ltd
Priority date: 2011-08-25
Filing date: 2011-08-25
Publication date: 2012-04-25

Abstract

The invention provides a preparation method of a structure section sample of a small-sized wafer sample for observation. The preparation method comprises the following steps: A. preparing a small-sized wafer sample which needs to be analyzed into a section sample which is approximate to a target area which needs to be observed by adopting a manual splitting method and a manual grinding and propelling method; B. carrying out fixed-point polishing along the prepared section sample which is approximate to the target area by adopting a focused ion beam (FIB) analyzer until the central position of the structural target area which needs to be observed is polished; and C. taking out the polished section sample from the FIB analyzer, observing the sample in a scanning electron microscope (SEM) to find out the target area which needs to be analyzed, taking an SEM photo of the section of the target area, and measuring the height in the Y direction so as to finally complete analysis of the section of the wafer sample with the small-sized structure. By adopting the preparation method, the height in the Y direction of the section of the wafer sample with the small-sized structure can be accurately measured by adopting the FIB analyzer and the SEM without a fixed-point cutting machine.

Description

The sample preparation methods that a kind of small size wafer sample structural section is observed

Technical field

The present invention relates to a kind of failure analysis method of wafer, particularly relate to the preparation method that a kind of needs carry out the wafer sample of failure analysis.

Background technology

In the physical structure analysis of wafer scale failure analysis (Wafer Level FA), cross-section analysis (Cross Section) is a kind of commonly used and effective Physical Analysis Methods.The failure analysis instrument that uses mainly contains the cross section machining tool, like fixed point cutting machine (SEAL), FIB analyser (FIB) etc.; Cross-section equipment is like optical microscope (OM), scanning electron microscope (SEM) etc.

For the wafer sample of some large scales (the analytical structure size is greater than 10um) even some repetitive structures, the difficulty of cross-sectional sample preparation is little, can make by hand the method for sliver directly carry out the cross-sectional sample preparation.And, surpassed the limit of manual sliver precision for the sample (the analytical structure size is less than 10um) of some small scale structures, even skilled again analyst also can't carry out manual cross section sliver.So must be by means of certain cross section machining tool, like fixed point cutting machine, FIB analyser.And FIB analyser wherein is high because of its microcell machining precision, and can in ion beam cross section processing, can use subsidiary electron beam to carry out cross-section, is widely used by industry.

But the FIB analyser equally also has the defective of cross-section analysis aspect: promptly owing to exist 52 ° angle between electron beam and the ion beam; As shown in Figure 1; In fact the secondary electron image of said electron-beam excitation is not fully perpendicular to the cross section; But have the certain included angle angle, and make its height dimension on the Y direction of cross section be actually and be compressed, there is the problem of so-called " cross section Y direction height loss ".

Certainly the manufacturer of FIB analyser has also found this problem; So correspondingly carried out the function improvement; Problem to " cross section Y direction height loss " has been added " Y direction altimetric compensation debugging functions "; After promptly importing the angle angle in electron beam and cross section, carry out simultaneously trigonometric function automatically and convert, with the altimetric compensation of Y direction corresponding height (than suitably increasing certain altitude before the compensation) when vertical fully.But; There is the people to do experiment to this way; Comparison is used the Y direction height of FIB analyser cutting section sample and is carried out the Y direction height behind the pure cross section sem observation behind the manual sliver with spline structure; Find that in fact still there is certain error in the Y direction altimetric compensation debugging functions that the FIB analyser draws, as shown in Figures 2 and 3, obtain the measuring error such as the table one of FIB analyser.

Table one analysis of measurement errors table

Sequence number	Scanning electron microscope	The FIB analyser	Error
				1	250.5	250	0.002％
2	191	190	0.50％
				3	1005	960	4.48％

Can be learnt that by table one directions X is almost error free, promptly angle does not have influence to the directions X data, and the error of Y direction, even used " correction of Y direction altimetric compensation " still to have error up to 4.48%.

Certainly use the fixed point cutting machine to carry out specimen preparation; Can after preparing cross-sectional sample, directly in scanning electron microscope, carry out the observation of vertical cross-section; So can solve the problem of " cross section Y direction height loss ", but, not possess such board for some Design House or third party laboratory; So can't obtain the accurate altitude information of undersized wafer sample cross section Y direction, influence the subsequent analysis work of wafer sample.Therefore, how under the situation of the cutting machine of not fixing a point, using the FIB analyser to carry out the cross-section analysis of small size wafer sample becomes this technical field problem demanding prompt solution.

Summary of the invention

For solving in the prior art, under the situation of the cutting machine of not fixing a point, use the FIB analyser can't obtain the problem of the Y direction height value in small size wafer sample cross section, the present invention provides following technical scheme:

The sample preparation methods that a kind of small size wafer sample structural section is observed may further comprise the steps:

A, the small size wafer sample that will analyze are prepared a cross-sectional sample near the target area that needs to observe through the method that manual sliver and hand lapping advance;

B, use FIB analyser fix a point to polish along having prepared near the cross-sectional sample of target area, until being polished to the center that needs the observation structure target area;

C, will polish good cross-sectional sample and from the FIB analyser, take out; Put into scanning electron microscope and observe, find the target area that needs analysis, take the electron scanning micrograph in cross section, target area; Measure Y direction height, accomplish the analytical work of small size wafer sample structural section.

As a kind of preferred version of the present invention, the distance near the target area that needs to observe in the said steps A is 8～12um.

The present invention has following advantage: be suitable for the sample preparation methods that small size wafer sample structural section is observed through this kind; Be actually manual rough appearance; Add the fining-off of FIB analyser; And the measurement of taking pictures of last scanning electron microscope vertical cross-section; The problem of " cross section Y direction height loss " that the problem of ion beam and electron beam angle causes fundamentally solved in the scanning electron microscope owing to can use FIB analyser and scanning electron microscope to carry out the accurate measurement of small size wafer sample structural section Y direction height under the condition of the cutting machine of not fixing a point.

Description of drawings

Fig. 1 FIB analyser intermediate ion bundle and electron beam graph of a relation;

Fig. 2 scanning electron microscopy measurement sample parameters photo;

Fig. 3 FIB analyser measuring samples parameter photo;

The electron scanning micrograph that Fig. 4 the inventive method obtains.

Embodiment

Do to set forth in detail in the face of this process implementing example down, thereby protection scope of the present invention is made more explicit defining so that advantage of the present invention and characteristic can be easier to it will be appreciated by those skilled in the art that.

Present embodiment is analyzed to the cross section to the stepped construction of Via, α-Si, Metal in certain " MTM " structure in certain wafer sample PCM district, obtains taking pictures of scanning electron microscope as shown in Figure 4, records the accurate height value of Y direction.

Concrete testing procedure is following:

A, the method that this small size wafer sample is advanced through manual sliver and hand lapping; Prepare a cross-sectional sample near the target area that needs to observe; Distance is controlled to be 10um; With convenient follow-up FIB analyser processing, reduce the process time and the processing cost of FIB analyser;

C, will polish good cross-sectional sample and from the FIB analyser, take out; Putting into scanning electron microscope observes; Find the target area that needs analysis, take the electron scanning micrograph in cross section, target area, measure Y direction height; Obtaining Y direction height is 1.54um, accomplishes the analytical work of small size wafer sample structural section.

The above; Be merely one of embodiment of the present invention; But protection scope of the present invention is not limited thereto; Any those of ordinary skill in the art are in the technical scope that the present invention disclosed, and variation or the replacement that can expect without creative work all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain that claims were limited.

Claims

1. the sample preparation methods observed of a small size wafer sample structural section, it is characterized in that: this method may further comprise the steps:

2. the sample preparation methods that a kind of small size wafer sample structural section according to claim 1 is observed is characterized in that: the distance of the target area of observing near needs in the said steps A is 8～12um.