KR100195838B1 - Scribing method for true cross section containing defect and apparatus therefor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer cutting method for forming a real cross section of a wafer defect portion, and an apparatus thereof, wherein the scratches and cracks are formed after a scratch having a precision of microns in a desired position from a high magnification secondary electron image using an ion focusing device. The promotion of crack propagation speed by the creation, propagation mechanism, and cooling means three aspects of high accuracy, high quality cross section, and short working time to solve various shortcomings of conventional analytical cross-section by combining cutting using fracture mechanics. By satisfying the requirements, the scope of use of expensive equipment is expanded, and the specimen manufacturing method that quickly and accurately analyzes various defects or desired analysis positions that may occur in manufacturing can be provided to develop new semiconductor manufacturing technology and improve yield through process development work. To improve product reliability through wafer-level reliability assessment can do.

Description

Paper cutting method and apparatus for forming real cross section of wafer defect

1A to 1C are diagrams illustrating a seal cross section forming step of a wafer defect portion according to a first embodiment of the present invention.

2 shows a second embodiment of the present invention.

3 shows a third embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1,21,31: Rough cracks 2,22,32: Fine cracks

3: expected cutting plane 4: defect

5 pad 6 wafer

7: tip 8: connecting member

9: improvement means 10: lower substrate

11 chamber 13 specimen

14 pressurization 15 support

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a true cross section of a wafer defect portion. Particularly, a minor crack in which a crack is formed around a wafer defect portion using a focused ion beam (hereinafter referred to as an FIB). As a starting point, it is possible to obtain good real section with high precision passing through the defect area, to increase the efficiency of analysis work including defect analysis, and to improve the accuracy of the result, which helps to perform the process development work and wafer level reliability evaluation quickly and effectively. The present invention relates to a method for forming a real cross section of a wafer defect portion in which semiconductor manufacturing improves yield and product reliability.

In order to develop new semiconductor manufacturing technology through process development work, improve yield, and improve product reliability through wafer level reliability evaluation, the most important thing is to quickly and accurately analyze various defects or desired analysis positions that may occur during the manufacturing process. It is important.

The most reliable analysis is to find the cross section of the wafer at the target location of the defect and analyze it through an analytical device such as an electron microscope. To do this, it has to meet three requirements: high precision, good quality section and short working time. However, there is no suitable cross-sectional manufacturing process that satisfies the above requirements.

Looking at the conventional cross-sectional manufacturing method and its features are as follows.

First of all, the polishing method is a method of finding a desired analysis position by cutting a specimen into an appropriate size, molding an epoxy resin, etc., and polishing it mechanically using an abrasive according to the type. Although it is relatively high, the process takes a lot of time, and trial and error is difficult to work, there is a problem that the cross-sectional state is affected by the permeation due to mechanical friction, accumulation of destructive pollutants due to stress, etc., it is difficult to obtain a real cross section.

Secondly, there is an ion beam milling method using FIB, which is a method of cutting an analysis position region through a high energy ion beam using a cutting function among various functions of the FIB. However, this method has high accuracy but high energy ion beam, which can cause local melting and damage of structure, so it is difficult to obtain real section, long working time and angle of cutting section make it difficult to analyze and observe. have.

Third, there is a fracture cutting method. The fracture cutting method uses a ceramic tip such as diamond to scratch the edge near the defective location, thereby cutting the cross section using a hand or a suitable tool. When the accuracy is low and the probability of failure is high and the amount of defects to be analyzed is small, there is a fatal defect that cannot be analyzed due to failure. In addition, there are many problems such as difficulty in managing the ceramic tips.

Therefore, in order to solve the above problems, the present invention finds the position of the desired cross-section using the image found through the secondary electron detector of the FIB, and forms a precise crack through the cutting function of the FIB around the found position. Then, by using the formed crack as the starting point of crack propagation, the fracture surface is obtained to obtain a high-precision good cross section in a short time, and to provide a method for forming the cross section of the wafer defect portion that enables accurate defect analysis and observation. .

A feature of the present invention for achieving the above object is to select a position of a wafer defect portion at a necessary magnification by using a secondary electron image of the ion focusing device and a stage controller in the wafer cutting method for forming the actual cross section of the wafer defect portion. Forming a rough crack to be the starting point of crack generation under a first cutting condition by using a predetermined scanning method of the ion connecting device around the wafer defect portion; Forming a microcracks that will be the starting point of crack propagation under a second cutting condition using a predetermined scanning method of the device, cutting a predetermined size specimen containing the defects and cracks from the wafer, and The external load is applied to the formed portion to form a seal cross section passing through the defect portion.

The external load is applied to a portion where the crack is formed to form a seal cross section passing through the defect portion.

Another feature of the present invention for achieving the above object is a wafer cutting device in the wafer cutting device by cutting along an expected cutting surface with a crack as the starting point by applying a certain load to the top of the specimen including the wafer defect and cracks, the lower support and the lower A chamber for mounting the wafer specimen in the state of being cut into the upper portion of the support, a pressing portion for cutting the specimen by gradually applying pressure from an upper portion of the specimen mounted on the harbor surface of the chamber, and a supporting portion for supporting the pressing portion from the side surface. It consists of.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

1A to 1C are diagrams illustrating a method for forming a seal cross section of the defect portion 4 located between the wafer pads 5 according to the first embodiment of the present invention.

In the method for forming a real cross section of the wafer defect portion 4 according to the first embodiment of the present invention, first, a defect or a cross section is desired at a desired magnification using the first and second electron images of the FIB and the stage controller. Select it and place it in the center of the monitor.

Next, as shown in FIG. 1A, the rough crack 1 to be the starting point of crack formation is formed under the first cutting conditions below. The scanning mode of the equipment uses the spot mode.

The primary cutting conditions are as follows.

Accelerating voltage: 30kV

-Ion beam current: 3-5nA

-Aperture: No. 0

Next, the microcracks 2 of FIG. 1a to be the starting point of the crack propagation are formed under the following secondary cutting conditions. At this time, the microcracks 2 may be adjusted in a micron range or less by using a reduce mode of a scanning mode at a high magnification and determine a desired cross section.

The secondary cutting conditions are as follows.

Accelerating voltage: 30kV

Ion beam current: 500-800pA

-Aperture: No.1 or No.2

Upon completion of the operation, remove the specimen from the FIB and scratch the specimen around the cracks (1, 2) to be used for rough cutting using a diamond tip as shown in FIG. Cut by hand. At this time, the direction of the microcracks 2 may be a plane of short length as shown in FIG.

FIG. 1C is a diagram showing an apparatus for cutting the specimen of FIG. 1B along the direction of the crack 2.

The cutting device for cutting the specimen in the crack part direction shown in FIG. 1b includes a lower support 10 and a chamber 11 for mounting a wafer specimen 13 cut into an upper portion of the lower support. And a pressurizing portion 14 for cutting the specimen 13 by gradually applying pressure from the upper portion along the crack direction of the specimen 13 mounted in the chamber 11 and a support portion for supporting the pressing portion 14 from the side. It consists of 15 pieces.

At this time, the pressing portion 14 has a tip 7 having a sharp tip at the bottom thereof, the tip 7 is connected by a connecting member 8 and the connecting member 8 is a gear shifting means (not shown). It is provided to be moved up and down by hand by operating the rotary handle (9) by the time).

When the cutting of the approximate specimen 13 is completed by cutting around the wafer defects in FIG. 1B, the cutting is performed using the specimen cutting device of FIG. 1C, but the tip 7 of the cutting device pressing unit 14 is cut. Is applied to the cracks 1, 2 formed on the lower surface of the specimen 13, and is cut along the expected cutting plane 3 using crack generation and propagation mechanisms due to stress.

At this time, by filling the liquid nitrogen inside the chamber 11 in which the specimen 13 is placed to lower the temperature of the specimen 13, the brittleness is enhanced, the crack propagation speed is improved, and the material such as metal components in the circuit is improved. It reduces the mass effect and induces a clean surface.

2 is a cross-sectional view showing a second embodiment of the present invention.

In the second embodiment of the present invention, as shown in FIG. 2, the formation of the fine cracks 22 is first performed in the first embodiment using a reduce mode of a scanning mode. After forming the first thin and long under the same conditions as in the case of forming the microcracks 2, the specimens were removed from the FIB, and then subjected to the coarse cracks 21 using a suitable low magnification stereoscopic microscope and a diamond tip. To form.

3 is a cross-sectional view showing the third embodiment of the present invention.

In the third embodiment of the present invention, as shown in FIG. 3, first, the formation of the coarse crack 31 is performed by using the reduction mode of the scanning method to form the coarse crack 1 in the first embodiment. After forming a short time in the form of a rectangle under the same conditions as in the case, and again forming the micro scratches 32 under the same conditions as in the formation of the microcracks 2 in the first embodiment, and then taken out from the FIB The final scratch 43 is formed using a suitable low magnification stereoscopic microscope and a diamond tip.

Therefore, the crack part formation for smoothly obtaining the cutting surface passing through the defect portion on the wafer may be formed in various forms as described above, and in consideration of the characteristics of the specimen cutting device, it is possible to form fine cracks and coarse cracks of appropriate shapes.

As described above, in the wafer cutting method for forming the actual cross section of the wafer defect portion according to the present invention, the FIB is applied to the scratches and the cracks after the micron-scale scratches are generated at the desired positions from the secondary electron image of high magnification. Acceleration of crack propagation speed by creation, propagation mechanism and cooling is combined with cutting using fracture mechanics to solve the above-mentioned disadvantages of the conventional analytical cross-section. By satisfying the requirements, we can expand the scope of use of expensive equipment and provide specimen manufacturing methods that can quickly and accurately analyze various defects or desired analysis locations that may occur during manufacturing, thereby developing and yielding new semiconductor manufacturing technology through process development work. To improve the reliability of the product There.

Claims (14)

A wafer cutting method for forming a real cross section of a wafer defect portion, the method comprising: selecting a position of the defect portion at a necessary magnification by using a secondary electron image of the ion focusing device and a stage controller; and collecting the ion concentration around the wafer defect portion. Forming a rough crack to be the starting point of cracking under the first cutting condition using a predetermined scanning method of the apparatus, and performing a second cutting using a predetermined scanning method of the ion focusing device in the vicinity of the rough crack Forming a microcracks which will be the starting point of crack propagation under the conditions, cutting a predetermined size specimen including the defect portion and the track from the wafer, and applying an external load to the portion where the crack is formed to pass the defect portion. Wafer cutting method comprising the step of forming a cross section. The wafer cutting method according to claim 1, wherein a spot mode is used as a scanning method of an ion focusing device for forming the microcracks. The method of claim 1, wherein the primary cutting conditions of the ion connection device to form the microcracks have an acceleration voltage of 30 kV, an ion beam current of 3-5 nA, and no. Wafer cutting method characterized in that 0. The wafer cutting method according to claim 1, wherein a reduction mode is used as a scanning method of the ion connecting device for forming the rough cracks. The method of claim 1, wherein the secondary cutting conditions of the ion connection device to form the coarse crack is a wafer cutting, characterized in that the acceleration voltage is 30kV, the ion beam current is 500-800pA, the No. of the aperture is 1 or 2. Way. The method of claim 1, wherein when cutting the specimen including the defect and the crack from the wafer, the wafer has a short length on the specimen of the microcracks. The wafer cutting method according to claim 1, wherein the specimen including the wafer defect portion and the crack is cut using fracture mechanics by cooling when the specimen is cut along a predetermined cutting surface having the crack as a starting point. The apparatus of claim 1, wherein the crack size is in the micron range. The method of claim 1, wherein when the cracks are formed around the defects of the wafer, the fine cracks are first formed thinly and elongated under the first cutting condition by using a reduction mode in the scanning method of the ion implanter. Wafer cutting method characterized in that the specimen is removed from the ion focusing device and then formed a coarse crack. The method of claim 1, wherein when forming a crack in the defect portion of the wafer, first, after forming the coarse crack in a rectangular shape under a second cutting condition by using a reduction mode of the scanning method of the ion implanter, a short time is formed. And forming fine cracks under the first conditions at the time of forming the microcracks, removing the specimens from the ion concentrator, and forming final scratches. A wafer cutting device for cutting along an expected cutting surface having a crack as a starting point by applying a predetermined load to an upper portion of a specimen including a wafer defect and a crack, wherein the wafer is cut into the lower support and the upper portion of the lower support. And a chamber for mounting the specimen, a pressing portion for cutting the specimen by gradually applying pressure from an upper portion of the specimen mounted on the lower surface of the chamber, and a supporting portion for supporting the pressing portion from the side surface. According to claim 11, wherein the pressing portion has a sharp tip at the lower end, a connecting member which is integrally connected to the tip to the top of the tip, and is connected by the connecting member and the gear converting means is rotated by the tip up and down Wafer cutting device characterized in that consisting of a rotating means for transferring. 12. The wafer cutting device according to claim 11, wherein the tip attached to the lowermost part of the pressing unit is formed of diamond. 12. A wafer cutting device according to claim 11, wherein during wafer cutting by pressing the tip down to the upper surface, liquid wafer is filled into the chamber in which the wafer is mounted.