The present invention relates to an apparatus for ion beam fabrication and observation used in a process for inspection of a semiconductor device and more particularly, to an ion beam apparatus adapted to bore a hole for observation and form or deposit a deposition pile used to fill the hole and an ion beam analysis method.
In manufacturing semiconductor devices such as microprocessors or memories, reducing the number of defective devices and obtaining a high yield are required. This leads to significant issues in assuring early finding of defects such as defective continuity or short-circuit and foreign matters responsible for degradation of the yield and early countermeasures as well.
In order to detect defective devices, it has hitherto been practice to conduct an electrical inspection with, for example, an LSI tester using a probe in the phase of completion of the function of devices. Today, however, an inspection has been conducted midway in a process to aim at early detection and early taking of countermeasures. In such a case, a semiconductor device is returned to the manufacture process after completion of its inspection.
To analyze causes of a defect, a sectional geometry of a portion determined as being defective through inspection is observed. In preparation for the observation of the sectional geometry, a cross section is created by irradiating an ion beam on a specimen such as a wafer to cut off or shave the surface of the specimen on the basis of a sputtering phenomenon. This cross section is observed with a scanning electron microscope (SEM) to analyze causes of the defect.
However, as the degree of integration of a semiconductor device and minuteness of the process advances, the resolution of the normal SEM is not enough to observe the cross section of a specimen.
To cope with this problem, a method is available in which a part of a specimen is cut off through fabrication using an ion beam and the cut-off piece of specimen is observed and analyzed by using an SEM or transmission electron microscope having high resolution.
In the method of sectioning the specimen surface or partly cutting off the specimen, a hole is bored in the specimen. When the specimen with the remaining hole is returned to a semiconductor manufacture process, there is a possibility that the specimen will be recognized as a defective device. Under the circumstances, a method is employed according to which the hole is filled with a deposition pile and thereafter a resultant specimen is returned to the semiconductor manufacture process. As an example to this effect, one may refer to JP-A-2003-311435 entitled “A hole filling method based on an ion beam, an ion beam fabrication and observation apparatus and a method for manufacture of electronic parts”.
In the prior art, the thickness or height of a deposition pile for filling a hole cannot be controlled precisely, with the result that the peripheral edge of the hole cannot be flush with the deposition pile filling the hole, forming an uneven site in the surface of a semiconductor device. For example, in case the thickness of a deposition pile is small, a hole cannot be filled thoroughly to form a concave site whereas in the event that the thickness of a deposition pile is large, a deposition pile filling a hole results in a convex site.
In a general semiconductor process, if a concave or convex site having a depth or height of 50 nm or more is present on the surface of a semiconductor device, the convex site is cut off or shaved through CMP (chemical mechanical polishing) process. Disadvantageously, a cut-off piece of specimen causes the specimen to be scratched or gives rise to non-uniformity of coating of a resist agent applied by means of a spin coater in a photo-resist process.
An object of this invention is to provide a technique capable of precisely forming a deposition pile in a hole bored in the specimen surface.
According to the present invention, in an ion beam apparatus adapted to bore a hole in the surface of a specimen or form a deposition pile in the hole bored in the specimen surface, a measuring instrument is provided which measures the depth of the hole bored in the specimen surface or the height of the deposition pile filled in the hole.
During fabrication of boring a hole in the specimen surface or fabrication of filling the hole bored in the specimen surface, an image of an area encompassing the hole and the depth of the hole or the height of a deposition pile are displayed.
The measuring instrument includes a laser beam source for emitting or irradiating a laser beam into a hole or onto a deposition pile and a laser beam detector for detecting a laser beam from an irradiation area. The measuring instrument may be a scanning electron microscope.
According to the present invention, a deposition pile can be formed precisely in a hole bored in the specimen surface.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
The present invention will now be described by way of example with reference to the accompanying drawings.
Referring first to
The ion beam apparatus further comprises an FIB column controller 18, an overall controller 19, a stage controller 34, a deposition gas controller 53, a height measurement controller 63, a signal processor 42 and a display unit 4.
The FIB column controller 18 controls voltages applied to the ion source 11, extraction electrode 13, condenser lens 14, aperture 15, deflector 16 and objective lens 17.
The stage controller 34 controls the stage 31 adapted to hold a specimen 32 such as a wafer so as to move the stage 31 in three-dimensional direction and in rotary direction.
The deposition gas controller 53 controls start and stop of the supply of a deposition gas 52 confined in the deposition gas source 51. Used as the deposition gas 52 is, for example, W(CO)6. The height measurement controller 63 controls the height measurer (on laser beam source side) 61 and height measurer (on laser beam detector side) 62. The height measurer 61 has a laser beam source to emit or irradiate a laser beam onto a measuring position on the specimen 32. The height measurer 62 has an element, such as for example a photodiode, for detecting a laser beam and converting it into an electrical signal. Operation of the height measurers 61 and 62 will be described later.
The ion source 11 contains a liquid metal such as Ga. When a high voltage is applied to the ion source 11 and a voltage lower than the high voltage applied to the ion source 11 is applied to the extraction electrode 13, an ion beam 12 is emitted from the ion source 11. The ion beam 12 is focused by the condenser lens 14, so that the amount of ion beam passing through the aperture 15 can be adjusted. The ion beam 12 having passed through the aperture 15 is deflected by the deflector 16 and focused by means of the objective lens 17. The focused ion beam 12 is scanned on the specimen 32.
Under irradiation of the ion beam 12 on the specimen 32, constituent atoms in the surface of specimen 32 are discharged through a sputtering phenomenon. As a result, the surface of specimen 32 is cut off or shaved, boring a hole. The hole is bored such that a sectional geometry of specimen 32 can be observed, that is, a cross section of specimen 32 is exposed on the inner wall of the hole. With the hole bored, the cross section of specimen 32 can be observed by tilting the stage 31.
When the ion beam 12 is irradiated while supplying the deposition gas 52, the composition of the deposition gas is changed so that a deposition pile 33 of W (tungsten) may be formed on the specimen 32. Normally, the deposition pile is used to protect the specimen surface at the peripheral edge of a hole for cross section observation or to correct or modify wiring but in the present invention, it is used to fill the hole for cross section observation as will be described hereinafter.
The secondary electron detector 41 detects secondary electrons generated from the specimen 32 irradiated with the ion beam 12. The signal processor 42 processes a secondary electron detection signal from the secondary electron detector 41 in synchronism with a scanning signal for beam deflection and outputs a resultant signal to the overall controller 19. The overall controller 19 displays an SIM (scanning ion beam microscope) image on the screen of display unit 4.
Turning to
Illustrated in
Illustrated in
An operation screen 700 displayed on the display unit 4 during hole boring fabrication will be described with reference to
Turning to
A process of hole filling fabrication will be described with reference to
In this example, the hole filling proceeds while the height of the deposition pile being measured. In other words, the height of the deposition pile is measured and on the basis of a result of the height measurement, formation of the deposition pile is stopped. For example, at the time that the height of the deposition pile substantially equals the height of the peripheral edge of the hole, formation of the deposition pile is stopped. Alternatively, when the unevenness of specimen surface comes to 50 nm or less, formation of the deposition pile is stopped. In this manner, the filled deposition pile can be substantially flush with the hole. Alternatively, the unevenness of specimen surface can be 50 nm or less. Accordingly, even a wafer having gone through the hole filling with the deposition pile is returned to the process line, a problem of generation of a defective device can be avoided. In addition, the wafer need not be discarded and an economical advantage can be attained.
Referring to
In the present embodiment, the height measurer 67 emits a laser beam 64 having a beam spot smaller than a diameter of hole. In the height measurer 68, a CCD (charge coupled device), for example, is used to detect positions of detection of a laser beam 65. When the position of emission of the laser beam from the height measurer 67 is fixed, the position of incidence of the laser beam on the height measurer 68, that is, the beam detection position of the measurer changes with the height of a laser beam irradiation area. Accordingly, on the basis of the position at which the height measurer 68 detects the laser beam, the height of the deposition pile can be measured.
Illustrated in
Illustrated in
Illustrated in
In the present embodiment, by using the laser beam 64 of a reduced beam spot, the height of the recess or raised site can be measured locally. Accordingly, this makes it possible to fill up a recess partially or locally formed in a deposition pile 33 which is lower than the peripheral edge of a hole and to remove a raised site partially or locally formed on a deposition pile which is higher than the peripheral edge of a hole.
Reference is now made to
A process of hole filling fabrication will be described with reference to
In the present example, the hole filling proceeds meanwhile the height of the deposition pile being measured. In other words, the height of the deposition pile is measured and on the basis of a measurement result, formation of the deposition pile is stopped. At the time that the height of the deposition pile substantially equals the height of the peripheral edge of the hole, the formation of the deposition pile is stopped. Alternatively, when the unevenness on the specimen surface comes to 50 nm or less, the formation of the deposition pile is stopped. In this manner, the deposition pile filling the hole can be substantially flush with the peripheral edge of the hole. Alternatively, the unevenness on the specimen surface can be 50 nm or less. Accordingly, even the wafer undergoing hole filling with the deposition pile is returned to the process line, a problem of generation of a defective device can be avoided. In addition, the wafer need not be discarded, having an economical advantage.
Turning now to
In the present embodiment, the height measurer 90 includes a laser beam source 92 such as a semiconductor laser, a lens 93 and a lens 94. The height measurer 91 includes a laser beam detector 95 such as a CCD adapted to detect the intensity of the laser beam two-dimensionally and a signal processor 96. The height measurer 90 can change the beam spot of a laser beam 64 by changing distance L between the two lenses 93 and 94. The height measurer 91 measures both the quantity of detected laser beam and the beam detection position.
Illustrated in
Illustrated in
A fourth embodiment of the ion beam apparatus and analysis method according to the invention will be described with reference to
The SEM column 2 includes an electron source 21, an extraction electrode 23, a condenser lens 24, an aperture 25, a deflector 26, an objective lens 27 and a backscatter electron detector 28, having its interior maintained at high vacuum. Like the FIB column controller 18, an SEM column controller is provided for controlling the electron source 21, extraction electrode 23, condenser lens 24, aperture 25, deflector 26 and objective lens 27 but it is not illustrated herein.
In the present embodiment, an SIM image under irradiation of an ion beam 12 and an SEM (scanning electron microscope) image under irradiation of an electron beam 22 can both be obtained. Of these images, the SIM image can be obtained through the method which has already been described with reference to
When a high voltage is applied to the electron source 21 and a voltage lower than the high voltage applied to the electron source 21 is applied to the extraction electrode 23, an electron beam 22 is emitted from the electron source 21. The electron beam 22 is converged by the condenser lens 24 so that the amount of electron beam passing through the aperture 25 may be adjusted. The electron beam 22 having passed through the aperture 25 is deflected by means of the deflector 26 and is then focused by means of the objective lens. The thus focused electron beam 22 is scanned on a specimen 32.
The backscatter electron detector 28 detects backscatter electrons generated from the specimen 32 irradiated with the electron beam 22. The signal processor 42 processes a backscatter electron detection signal from the backscatter electron detector 28 in synchronism with a scanning signal for electron beam deflection and delivers a resultant signal to the overall controller 19. The overall controller 19 displays an SEM image on the screen of display unit 4.
In the ion beam apparatus according to the present embodiment, an SEM image of the specimen 32 can be observed on real time base meanwhile the surface of specimen 32 being fabricated for boring or a deposition pile being formed by using an ion beam 12.
By changing the objective lens 27, the focal position of electron beam 22 is changed and differently focused SEM images can be obtained. When the scanning range of electron beam 22 is so set as to cover a position at which hole boring by the ion beam 12 proceeds and the objective lens 27 is controlled such that the SEM image is focused on the hole bottom, a depth of the hole can be determined from a focal distance at that time. Further, during hole filling after hole boring, too, information about the hole filling height can be monitored.
Turning to
The selection button 76 is adapted to select either FIB or SEM. When the selection button 76 is clicked to select FIB and the hole boring button 77 is clicked, an SIM image of specimen 32 around a hole boring area is displayed together with a rubber band 74 for designating the hole boring area are displayed. Circular contact holes have already been formed in the specimen surface. The rubber band 74 is so set as to form a cross section of a contact hole. With the start button 80 clicked, the ion beam 12 is irradiated on an area on the surface of specimen 32 defined by the rubber band 74 and hole boring fabrication is started. Indicated in the condition display area 75 are a fabrication size, a material of the specimen and a depth. The fabrication size represents a geometrical dimension of the hole. The depth is one the hole has at present.
During hole boring fabrication, the electron beam 22 is irradiated onto a hole and the backscatter electron detector 28 detects a backscatter electron beam 22 from the hole. The position of objective lens 27 is controlled such that an SEM image of the hole can be in focus. In accordance with a controlled position of the objective lens 27, a depth of the hole, that is, a height of the deposition pile is measured. It is to be noted that the SEM image is not displayed on the operation screen 703. When the height of the deposition pile coincides with the height of peripheral edge of the hole, the hole filling fabrication ends.
Illustrated in
Illustrated in
Indicated in the condition display area 75 are a fabrication size, a material of the specimen and a depth. The fabrication size represents a geometrical dimension of the deposition pile and the depth is one the hole has at present. As the height of the hole coincides with that of the peripheral edge of the hole, the hole filling fabrication ends.
Referring to
A height measurer 69 is arranged above a specimen 32. The height measure 69 has a laser beam source and a laser beam detector. Accordingly, in the height measurer 69 of the present embodiment, the height measurer (on laser beam source side) and height measurer (on laser beam detector side) which have been set forth so far are integrated and a single connection port to the specimen chamber suffices. With the height measurer 69 arranged above the specimen 32, a depth of the hole tilted in depth direction can be measured and a height of a deposition pile for filling the hole tilted in depth direction can be measured.
In
According to the present invention, since precise deposition can be performed while measuring the height of the deposition pile, not only hole filling but also correction of wiring for connecting circuits with a conductive deposition pile in a semiconductor device can be carried out. Namely, in the wiring correction or modification of circuits in the semiconductor device, the present invention can also be applied to utilization of wiring with correct resistance values.
While the present invention has been described by way of example, the invention is by no means limited to the foregoing embodiments and persons skilled in the art should understand that various changes, alterations and modifications can be made within the framework of the invention recited in the appended scope of claim for a patent.
Number | Date | Country | Kind |
---|---|---|---|
2005-153660 | May 2005 | JP | national |