JP2852078B2 - Focused energy beam irradiation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a laser beam, an ion beam,
The present invention relates to a method and an apparatus for irradiating a focused energy beam such as an electron beam.

[Conventional technology]

Semiconductor integrated circuits (LSIs) are being miniaturized and highly integrated in order to achieve higher performance and higher speed. However, this has made LSI development more difficult, and the development period has been prolonged. Has been invited. Under these circumstances, a prototype was
An LSI in which a defective part on an LSI chip is specified, the wiring existing in the part is cut, or the wiring is formed in an arbitrary part and the defective wiring is repaired.
If it is manufactured, subsequent characteristic evaluation and design change can be performed quickly.

Conventional techniques for repairing LSIs include, for example, X-Extended Abstracts of the Seventeens Conference on Solid State Devices and Materials, Tokyo, 1985, 193rd.
Page to page 196 (Extended Abstracts of the 17th Conf
erence on Solid State Devices and Materials, Tokyo,
1985, pp. 193 to 196) discusses a method of connecting arbitrary points described in the literature. To this end, Mo (CO) ₆ vapor is introduced into an LSI chip placed on an XY stage, a Mo film is deposited by a photochemical reaction by laser light irradiation, and the Mo film is moved by moving the XY stage. A laser CVD (Chemical Vapor Deposition) technique for forming wiring is disclosed.

Further, for example, Japanese Patent Application Laid-Open No.
A technique of filling a through hole with a conductive material using the D technique is shown.

If under the protective film or multilayer wiring is formed,
By opening a window in the interlayer insulating film, burying a conductive material in a hole (a window opening portion) using the laser CVD technique, and then forming a wiring, an arbitrary portion can be connected.

Laser CVD is a local thermochemical reaction at a laser irradiation location, and has been attracting attention because it can shorten the time required for repairing LSIs in particular because the deposition rate is high. The formed film (conductive film) is required to have low resistance from the viewpoint of signal transmission, and is required to be able to withstand use during the LSI debugging period, and it is required that breaks and cracks do not peel off. . To improve the reliability of these film properties,
While optimizing the film formation process conditions (stage feed speed, laser power, base film formation conditions, etc.),
From the device side, an autofocus function is required to efficiently irradiate the laser to the LSI surface.

As a conventional technique relating to autofocus, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-53923, an automatic focusing device for a microscope is known.

[Problems to be solved by the invention]

In the above-described conventional technology (automatic focusing device of a microscope), in a photomask or wafer inspection process in an LSI manufacturing process, a sample is illuminated with illumination light (laser light), and the sample is placed by detecting a defocus from reflected light. The height of the stage is adjusted to match the focus position.

The focusing procedure is as follows. The sample is irradiated with illumination light, and the reflected light is divided into two systems by a prism and guided to two light receiving units. When defocusing occurs, imbalance occurs in the amounts of light reflected by the two light receiving units, and the direction of defocusing can be detected from the degree of change. The stage is controlled by a servomotor, and by inputting the difference of the electric signal of the defocus at the light receiving section to the servomotor, the stage moves minutely in the height direction and is always kept in focus. .

In this way, the microscope's autofocus device can move the stage by a small distance in the XY direction and stop it, as is used in the inspection process, to achieve very accurate and good tracking. it can. On the other hand, laser CV
In D, the XY stage is driven at a predetermined speed (for example, 20 μm / s) while irradiating the laser to the sample surface to form wiring.
To move the long distance (up to 10mm). In this case, X-
Because the method of holding the sample on the Y stage varies, X-
The Y stage surface and the sample surface are not parallel. So XY
An auto-focus function is indispensable when focusing on the sample surface when moving the stage. When a conventional microscope autofocus device is applied to the laser CVD wiring formation, X
Since the target is a sample that is constantly moving in the -Y direction, there is a problem in its followability. That is, if the focus shifts during the wiring formation and the moving direction and the moving amount of the Z stage are erroneous, the focusing operation cannot be performed thereafter, so that the laser surface is not efficiently irradiated with the laser beam on the LSI surface. There is a problem that disconnection occurs in the inner wiring. That is, in the laser CVD, it has been a problem to always focus on the sample surface with good followability during wiring formation.

An object of the present invention is to provide a focused energy beam irradiation method and apparatus capable of focusing on a sample surface with good tracking during wiring formation using an energy beam such as laser CVD or ion beam CVD. It is in.

[Means for solving the problem]

The above-mentioned object is to provide an in-focus detection means capable of detecting that an arbitrary point on the surface of a sample (LSI chip) mounted on a stationary stage is in focus, and a Z for adjusting the height of the sample.
For a stage and a point on the chip surface, three linear scales of X, Y, Z that read the stage coordinates of this point,
A computer that calculates the inclination between the chip surface and the XY stage surface by receiving the input of the value of the linear scale, and when an arbitrary point on the chip is given, the computer calculates the XYZ coordinates of this point. To the coordinate values of
This is achieved by an XY stage and a Z stage configured to drive and control the XY and Z stages according to this value.

[Action]

In the above configuration, before irradiating the laser, the surface is focused on three different points on the sample (chip), and the coordinates on the X, Y, and Z stages are read into the computer at each of these points. In the computer, based on the coordinates of the three points on the stage (three-dimensional coordinates), the chip surface and the X-
The inclination of the surface of the Y stage is calculated. When irradiating a laser to form wiring between arbitrary points on the chip, the XY stage and the Z stage are drive-controlled based on the calculation result of the inclination. Thus, when wiring is formed at an arbitrary point on the chip by laser CVD, the focus can always be focused on the chip surface, and a highly reliable wiring can be formed.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6 by taking a case of repairing wiring of an LSI as an example.

FIG. 1 is a block diagram of an embodiment of a focusing apparatus for a sample surface according to the present invention, FIG. 2 is a surface view of an LSI chip, and FIG. 3 is a view of an LSI chip mounted on an XY stage. FIG. 4 is a diagram showing the relationship between the chip surface and the XY stage surface, FIG. 5 is a diagram showing the processing flow of the computer 15 in FIG. 1, and FIG. 6 is a diagram shown in FIG. FIG. 2 is a configuration diagram of an LSI wiring forming apparatus to which a focusing device for a sample surface is applied. FIG. 7 is an explanatory view of a connection hole opened in the Al wiring of the LSI, and FIG. 8 is a flowchart of position correction.

First, the configuration and operation of one embodiment of the present invention will be described with reference to FIGS. In FIG. 1, an LSI chip 3 is mounted on an XY stage 1. The illumination light from the illumination lamp 10 is transmitted through a lens 9, a half mirror 5, and an objective lens 4.
Irradiates the surface of the LSI chip 3 through the objective lens 4 and forms an image on the TV camera 6 through the objective lens 4.
The image signal from the imaging device 6 is displayed on the monitor device 8 through the image processing device 7, and the image processing device 7 outputs the reference mark C on the monitor device 8. It is also connected to a computer 15. By moving the Z stage 2 up and down, the LSI chip 3
Is configured to focus on the surface. Also, 11,1
Numerals 2 and 13 denote displacement detectors for reading the positions of the XY stage 1 and the Z stage 2. The computer 15 reads a value in the XYZ coordinate system at an arbitrary position on the LSI chip 3 through the interface circuit 14 by the computer. The XY stage 1 and Z are controlled by a command from the computer 15 through the interface circuit 14.
The stage 2 is configured to be controlled.

As shown in FIG. 2, it was placed on the XY stage 1.
The LSI chip 3 can be used to hold the chip when
-Fixed in a state of being tilted or floated due to foreign matter 19 (for example, a piece at the time of chip dicing) existing on the Y stage 1. The chip itself has uneven thickness and warpage, and the accuracy of flatness and orthogonality is also required on the XY stage side, but these are about 1/1000 to 1 / 10,000, and their influence is negligibly small. Also, the maximum step on the chip surface is 10
μm, small. On the other hand, the foreign matter 19 has a diameter of 50 μm,
In both ends of the chip Assuming ^{that □} is the the center of the chip
A difference of 100 μm occurs, and the chip surface and the XY stage surface have an inclination of 0.6 °. When wiring is formed by laser CVD by irradiating a laser beam in such a state, it is necessary to control in the height direction (Z direction) in order to focus on the chip surface.

Assuming that the coordinate system on the chip 3 is represented by lowercase letters x and y and the coordinate system on the stage 2 is represented by uppercase letters X, Y and Z, as shown in FIG. Consider 22. 20 is the reference point of the chip, 21 and 22 are the alignment marks and the LSI
These coordinates are determined at the time of design. For the following description, the values of the O-x, y coordinates of 20, 21, and 22 are (x ₀ , y ₀ ), (x _f , y
_f), and (x _s, y _s).

In FIG. 1, first, the XY stage 1 is moved to be aligned with the reference mark C of the monitor device 8 at the reference point 20, and the Z stage 2 is adjusted so that the chip surface is focused. The stage coordinates (X ₀ , Y ₀ , Z ₀ ) at this time are determined by displacement detectors 11, 1
Read at 2 and 13 and input to computer 15 through interface device 14. This is the step in the processing flow of FIG.
See Figure 31. Then Similarly alignment marks 21 (the chip coordinates _{(x f, y f))} , and 22 (chip coordinates (x _s, y _s)) to move the X-Y stage 1 to the position of the reference mark C of the monitor 8
, The Z stage 2 is adjusted so that the chip surface is in focus, and the stage coordinates (X _f , Y _f , Z _f ) and (X _s , Y _s , Z _s ) at that time are read into the computer 15. .
(Steps 32 and 33 in FIG. 5) If three points in the space are given, the plane including the three points is uniquely determined, and the computer 15 calculates (X ₀ , Y ₀ , Z ₀ ), (X _f , Y _f , Z _f ), (X _s , Y _s ,
From the three points of Z _s ), it is possible to determine the equation AX + BY + CZ + D = 0 (1) of the plane representing the chip surface in the XYZ coordinate system as follows.

That is, A ² + B ² + C ² = 1 (3) AX _f + BY _f + CZ _f + D = 0 (4) holds, and A, B, C, and D are determined from this. A, B, and C represent the direction vectors of the surface 3a of the LSI chip 3 as shown in FIG. 4, and when the angles between the chip surface and the X, Y, and Z axes are α, β, and γ, B and C are the direction cosine. Ie In this way, the computer 15 is (2), (3),
A, B, C and α, β, γ are calculated by equation (5).
(Step 15a in FIG. 5) When an arbitrary point (x, y) on the LSI chip 3 is given (Step 34 in FIG. 5), the computer 15 calculates the X, Y, and Z coordinates of this point. (Step 15b in FIG. 5) XY stage 1, Z
By assigning to the stage 2, any point of the chip 3 can be focused on its surface.

In the above description, (x _f , y _f ) and (x _s , y _s ) are the coordinates of the alignment mark. However, the coordinates are not limited to these, and the chip including the reference point (x ₀ , y ₀ ) may be used. It is only necessary that the above coordinate values are clear. Needless to say, the greater the distance between these three points, the better the calculation accuracy.

If the above embodiment is applied to the formation of wiring in laser CVD, the focus position of the laser can always be adjusted to the chip surface even for the formation of long-distance wiring, thereby improving the reliability of the formed wiring. Can be. This will be described below.

FIG. 6 is a diagram showing an overall configuration of an LSI wiring forming apparatus including the apparatus for focusing on a sample surface according to the above embodiment.
In the figure, the components denoted by the same reference numerals as those in FIG. 1 indicate the same or equivalent components as those already described, and the description thereof will be omitted.

First, wiring formation will be described. In FIG.
The load lock chamber 41 is connected to the main chamber 43 via a gate valve 42, and can be evacuated by vacuum pumps 44, 44 'through pipes 45, 45' and valves 46, 46 ', respectively. A sample table 47 is provided in the main chamber 43.
A sample (which may be an LSI chip or a wafer in some cases) 3 is mounted thereon, and is configured to be movable by an XY stage 1 and a driving device 1a. The chip (or wafer) 3 is supplied into the main chamber 43 by the transport mechanism 51 together with the sample table 47. Also, the main chamber 43
, A CVD material gas cylinder 54 via a pipe 52 and a valve 53
Are combined. The laser light 56 output from the laser oscillator 55 is bent by a mirror 59 via a shutter mechanism 57 and an output adjustment mechanism 58, and then is irradiated onto the wafer 3 via a window 61 while being focused by the objective lens 4. You. The illumination light 63 from the illumination light source 10 is bent by the mirror 5 via the filter 64, and then is passed through the objective lens 4 and the window 61 through the LSI.
Illuminate the chip 3. The surface of the LSI chip 3 is mirror 6
6. Observation is possible by the eyepiece 67, and also by the imaging device 6 and the image processing device 7 and the monitor device 8 connected thereto. Here, it is assumed that the chip surface is optically adjusted so that the image of the chip surface is formed on the image pickup device 6 at the position of the objective lens 4 where the laser beam 56 is focused on the chip surface. In addition, a shutter mechanism is provided by the computer 15.
57, an output adjustment mechanism 58, a filter 64 and the like can be controlled.

Next, the function of each part and the procedure of wiring formation will be described.

An LSI chip (or wafer) 3 on which wiring is to be formed is fixed on a sample table 47, and these are mounted on an XY stage 1 in a main chamber 43 by a transfer mechanism 51. After the inside of the main chamber 43 is sufficiently evacuated by the vacuum pump 44 ',
Close valve 46 'and open valve 54 to close cylinder
The gas in 54, for example, Mo (CO) ₆ is introduced into the main chamber 43 through the pipe 52. When the gas pressure of Mo (CO) ₆ reaches a predetermined pressure, for example, 0.1 Torr, the valve 53 is closed.

Then, the reference point C (for example, the center of the field of view) on the monitor device 8 is adjusted in advance so as to coincide with the center of the laser spot, and the output adjustment mechanism 58 is set to an appropriate value by a command from the computer 15. Thereafter, the shutter mechanism 57 is driven to irradiate the chip (or wafer) 3 with the laser light 56 output from the laser oscillator 55. The irradiation position (that is, the wiring formation position on the LSI chip) is determined by inputting coordinate data from the host computer 16 to the computer 15 and moving the XY stage 1 according to the coordinate data. The irradiated portion is heated by the laser light 56, and Mo (CO) ₆ is decomposed to deposit Mo. At this time, when the XY stage 1 is moved according to the coordinate data,
The deposited Mo adheres to the surface of the wafer (or chip) 3 to form a wiring. By the above procedure, LSI
Repairs (connects) defective parts in the chip.

The above is the description of the wiring formation. To focus on the LSI surface during the wiring formation, the above-described device for focusing on the sample surface is applied, and the operation is as follows.

In other words, in FIG. 6, three points on the chip 3 before the laser irradiation (provided that the coordinate values of the three points are known, for example, given by the host computer 16). ), The XY stage 1 and the Z stage 2 are moved while observing with the monitor device 8, and are aligned with the reference mark C, and the image is focused.
The XYZ coordinates are read by the computer 15. Computer 15
Then, as shown in the processing flow of FIG.
Parameters for calculating the inclination from the stage surface and converting the LSI chip coordinates to the XYZ coordinates (α,
β, γ). Thus, when an arbitrary point on the LSI chip is input from the upper computer 16 to the computer 15, the computer 15 obtains the XYZ coordinates of the point, and issues a command to the XY stage 1 and Z stage 2 through the driving device 1a. give. Thus, the wiring can be formed while always focusing on the chip surface.

Next, the correction of the wiring formation position will be described with reference to FIGS. 7 and 8. FIG. In FIG. 7, a hole 3a opened in the Al wiring of the LSI is about 5 μm ^square . Assuming that the chip coordinates of the hole position (hole center) are (x ₁ , y ₁ ), it is converted into an XYZ coordinate system by the apparatus for focusing on the sample surface of the present invention (step 71 in FIG. 8), and the XY stage, Consider the case where the Z stage is driven. (Step 72 in FIG. 8) At this time, the monitor device 8 is controlled with respect to the stage coordinates (X ₁ , Y ₁ , Z ₁ ).
It is assumed that the reference mark C, that is, the laser irradiation position is shifted by ΔX and ΔY as shown in FIG. ΔX, Δ
Y is caused by multiplying factors such as the XY stage drive-in accuracy, the calculation rounding error in coordinate transformation, and the deviation at the time of opening the window of the LSI, and the deviation is as large as 1 μm at the maximum. In this state, when a connection (filling of a hole) with an Al wiring is made by irradiating a laser, a connection failure is caused. If such a deviation is detected, ΔX and ΔY are visually determined while looking at the monitor device 8 (step 73 in FIG. 8), and the XY stage 1 is moved (step 74 in FIG. 8). The center of the hole 3a is aligned with the reference mark C as shown in FIG. In the process of step 73, ΔX and ΔY may be calculated by using a technique of image processing such as pattern recognition instead of visual observation. After that, irradiate the laser,
Fill in the holes (step 75 in FIG. 8) is performed. In the Z direction, since ΔX and ΔY are small values of 1 μm or less, there is no need for correction. Next, as for wiring formation, for example, as shown in FIG. 7 (c), the chip coordinates (x ₁ , y ₁ ) to (x
₂ , y ₂ ), the point (x ₂ , y ₂ ) is also corrected after the coordinate transformation based on the correction values ΔX, ΔY obtained in step 73 in FIG. 8, and (X ₁ + ΔX , Y ₁ + ΔY, Z ₁ ) to (X ₂ +
By controlling the driving of the XY stage 1 and the Z stage 2 to ΔX, Y ₂ + ΔY, Z ₂ ), it is possible to form the wiring 3b free from the connection failure from the hole 3a.

Although the wiring forming apparatus using laser CVD has been described as an application example of the present invention, the present invention can also be applied to wiring formation using ion beam CVD, an apparatus for cutting wiring using ion beam, and a processing apparatus using electron beam.
It goes without saying that the apparatus for focusing on a sample surface according to the present invention is applicable.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform focusing at an arbitrary point on the chip based on the results of focusing at three points on the chip before processing, so that an LSI chip having a defective portion is repaired. In this case, highly reliable wiring formation can be achieved. As a result, debugging in LSI development can be performed quickly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a focusing apparatus for a sample surface according to the present invention, FIG. 2 is a schematic view of an LSI chip mounted on an XY stage, FIG. 3 is a surface view of the LSI chip, FIG. 4 is a diagram showing the relationship between the chip surface and the XY stage surface;
FIG. 5 is a diagram showing a processing flow of the computer in FIG. 1, FIG. 6 is a block diagram of an LSI wiring forming apparatus to which the apparatus for focusing on the sample surface shown in FIG. 1 is applied, and FIG. of
FIG. 8 is an explanatory view of a connection hole opened in an Al wiring, and FIG. 8 is a flowchart of position correction. DESCRIPTION OF SYMBOLS 1 ... XY stage, 2 ... Z stage 3 ... Sample (LSI chip or wafer) 4 ... Objective lens 6 ... Imaging device 8 ... Monitor device 11,12,13 ... Displacement detector 15 ... Computer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidezo Sano 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Yokohama, Japan Inside the Manufacturing Research Laboratory, Hitachi, Ltd. (56) References JP-A-64-13723 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 7/11

Claims (6)

(57) [Claims] A stage mounted on the stage and movable in three-dimensional directions of XYZ; a height detector for detecting a height of a surface of the sample mounted on the stage; Position detecting means for detecting a position in a three-dimensional direction, focused energy beam irradiating means for irradiating the surface of the sample mounted on the stage means with an energy beam focused via an optical system, and detection by the height detecting means The position of the stage means in the Z direction is controlled in accordance with the position of the stage means which continuously moves in the XY plane detected by the position detection means based on the height of a plurality of points on the sample surface. Control means for adjusting the height of the sample surface to the height of the focal point of the focused energy beam irradiated by the focused energy beam irradiation means. . 2. The apparatus according to claim 1, wherein said height detecting means irradiates said sample surface with light in the same optical axis direction as said focused energy beam irradiating means, and detects reflected light to detect the height of said sample surface. The focused energy beam irradiation apparatus according to claim 1, wherein: 3. The focused energy beam irradiation apparatus according to claim 1, wherein the energy beam emitted by said focused energy beam irradiation means is a laser beam. 4. A method for detecting a height of a plurality of points on a surface of a sample mounted on a movable stage, calculating an inclination of the sample surface from the detected heights of the plurality of points, and mounting the sample. The position of the stage in the XY direction is measured while continuously moving the stage in the XY plane, and the calculated inclination of the sample surface and the information of the measured position of the continuously moving stage in the XY direction are measured. Controlling the stage to adjust the height of the surface of the sample to the focal point of the focused energy beam irradiating the sample. 5. The method according to claim 1, wherein the detection of the height of the surface of the sample is performed by irradiating light from a direction coaxial with an optical axis of the focused energy beam irradiating the surface of the sample and detecting the reflected light. The focused energy beam irradiation method according to claim 4. 6. The method according to claim 4, wherein said focused energy beam is a laser beam.