JP2541440B2 - Laser process equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus, and more particularly to a laser processing apparatus for finely processing a semiconductor element, a mounting substrate for the semiconductor element or the like by laser light.

[0002]

2. Description of the Related Art An example of a conventional laser process apparatus for irradiating a processing object with a processing laser beam through an objective lens of a microscopic optical system for observing a processing object such as a substrate for fine processing is known. It is disclosed as a light irradiation device in JP-A-1-210186.

As shown in FIG. 3, this light irradiation device 20
Has a light irradiation optical system 21 and an observation optical system 22.
In the light irradiation optical system 21, the irradiation light source light LA11 of the processing laser light emitted from the illumination light source 25 is sequentially transmitted through the lens 26 and the dichroic mirror 27, and the scanning mirror 28.
The reflected light is incident on the irradiated surface 30A of the light irradiation target 30 as the irradiation light beam LA12 through the objective lens 29. Further, in the observation optical system 22, for example, the illumination light source light LA21 emitted from the observation illumination light source 31 of an incandescent lamp passes through the lens 32 and enters the half mirror 27, and is reflected by the half mirror 33 to be folded back and dichroic mirror 27. Be led to.

The dichroic mirror 27 is an illumination light source light L.
The reflected light A21 is reflected, while the irradiation light source light LA11 is transmitted. As a result, the illumination light source light LA21 enters the scanning mirror 28 through almost the same optical path as the principal ray of the irradiation light source light LA11 passing through the dichroic mirror 27, is reflected by the scanning mirror 28, and passes through the objective lens 29.
The illumination light beam LA22 is incident on the irradiation target surface 30A of the light irradiation target 30.

Here, the scanning mirror 28 is an objective lens 29.
The objective lens 29 is telecentric. Therefore, the irradiation light beam LA12 and the illumination light beam LA22 reflected by the scanning mirror 28 and incident on the irradiated surface 30A based on the irradiation light source light LA11 and the illumination light source light LA21 are such that the scanning mirror 28 rotates in the direction of the arrow b. Thus, even when the irradiation surface 30A is scanned, the light always enters almost perpendicularly to the irradiation surface 30A.

The image of the illumination light beam LA22 reflected by the illuminated surface 30A returns to the dichroic mirror 27 through the objective lens 29 and the scanning mirror 28 in sequence, is bent by the dichroic mirror 27, and is observed light beam L.
It is returned to the half mirror 33 as A23. as a result,
The observation light beam LA23 transmitted through the half mirror 33 enters the observation image sensor 35 through the lens 34, and an image of the illuminated surface 30A is formed on the observation image sensor 35.

In the above structure, the irradiation light beam LA22
When the scanning mirror 28 rotates in the direction of arrow b, the scanning mirror 28 is sequentially moved and scanned to a predetermined processing position on the irradiated surface 30A.

Since the illumination light source light LA21 is set so as to pass through the same optical path as the principal ray of the illumination light source light LA11 when it is returned from the dichroic mirror 27 to the scanning mirror 28, the scanning mirror 28 is rotated. If the irradiation light beam LA12 moves due to the movement, the irradiation light beam LA12 also moves in the same direction and with the same amount.

In this case, as for the processing accuracy, a method of reducing the condensing size of the laser light by increasing the magnification of the objective lens 29 has been adopted. According to this method, by using a high-magnification lens having a numerical aperture of about 0.5 as the objective lens 29, a fine condensed spot of about 1 μm can be obtained.

[0010]

In the conventional laser processing apparatus, when performing microfabrication on the order of 1 μm, a high-magnification lens with a numerical aperture of about 0.5 is used as an objective lens in order to reduce the size of the condensed laser light. It becomes indispensable to use, and as a result, the working distance, which is the distance between the objective lens and the object to be processed, becomes very short, about 1 mm or less, and in order to avoid contact between the objective lens and the object to be processed,
There is a problem in that it becomes difficult to process an object to be processed having large irregularities, and the shape of the object to be processed is largely restricted.

Further, by using a high-magnification lens having a numerical aperture of about 0.5 for the objective lens, the working distance of the objective lens from the object to be processed is about 1 mm or less, and the depth of focus of the objective lens is about 1 μm. Since the depth becomes extremely shallow, it is necessary to control the focal position of the focused spot with high accuracy, which causes a problem that the device becomes expensive.

[0012]

[Means for Solving the Problems] Two-dimensional orientation of a workpiece
First moving means for roughly moving to
The object to be processed placed on the means is passed through an objective lens.
And an objective of the observation optical system
The object to be processed having an optical axis in a direction different from the optical axis of the lens
Emitting incident laser light as a Bessel beam
Bessel beam optical system and this Bessel beam optical system
Second moving means for moving in a direction perpendicular to the optical axis
And the Bessel beam optics is
The first laser beam for processing the object to be processed
A first laser light source for supplying laser light and
A second laser beam for instructing the processing position of the workpiece
A second laser light source for supplying the incident laser light;
Combining the first laser light and the second laser light
With the dichroic mirror and this dichroic mirror
Processing by combining the combined light into a Bessel beam
A lens for projecting onto an object.
User process equipment.

To roughly move a workpiece in a two-dimensional direction
Of the first moving means of and arranged on the first moving means of
Observation of observing the processed object through the objective lens
The optical system differs from the optical axis of the objective lens of this manufacturing optical system.
Has an optical axis in the direction
Bessel beam light that emits the light as a Bessel beam
Science system and this Bessel beam optical system with respect to its optical axis
Second moving means for moving in the vertical direction,
The Russell beam optical system is for processing the workpiece.
A first laser beam is supplied as the incident laser beam.
The laser light source and the processing position of the object to be processed
A second laser beam for supplying the incident laser beam as the incident laser beam.
A second laser light source, the first laser light and the second laser light source,
And a dichroic mirror that combines the laser light of
The combined light combined by the dichroic mirror is
And a conical lens that is formed into a frame and is emitted to the object to be processed.
And the second moving means has the light of the Bessel beam.
First and second orthogonal to each other on a virtual plane perpendicular to the axis
Of the Bessel beam with a piezo actuator
A laser printer characterized by moving the optical axis two-dimensionally.
Process equipment.

[0014]

In the laser processing apparatus of the present invention, the processing laser light and the processing position indicating laser light are processed through the Bessel beam optical system having an optical axis different from the optical axis of the observation optical system. The point that the object is irradiated is different from the conventional device. The Bessel beam is a kind of plane wave and has a beam intensity distribution in which the light intensity at the center of the optical axis is about 10 times stronger than that at the peripheral portion, but does not cause diffraction along the optical axis, that is, the intensity distribution is It has the feature that it does not change significantly in the optical axis direction.

The nature of this beam is described in the 1987 Journal of Optical Society of
America (JOURNAL OF OPTICAL
SOCIETY OF AMERICA ), Volume 4, 4
No., pages 651 to 654, there is detailed description. In particular, it is described in this document that the Bessel beam has a feature that the focal length can be made much longer with the same beam size than the conventional Gaussian beam.

In the laser processing apparatus of the present invention,
Utilizing the characteristics of this Bessel beam, a Bessel beam optical system for processing is provided separately from the observation optical system. As a result, it is possible to make the focal length and working distance in processing much larger than those in the conventional apparatus, and it is possible to perform fine processing of 1 μm size even on a substrate having large unevenness.

Further, in the present invention, the processing laser light source and the processing position indicating laser light source are moved in the direction perpendicular to the optical axis of the Bessel beam while the positions of the observation optical system and the processing object are fixed. Since the processing position can be scanned while viewing the processing position within the field of view of the observation optical system, the processing progress can be observed in real time, unlike the conventional case.

[0018]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a schematic view showing an example of the structure of a Bessel beam optical system and an actuator in this embodiment. This embodiment is an example applied to the case where a large number of via holes having a diameter of about 1 μm are formed in a polyimide film on a multilayer wiring substrate by an application process using ultraviolet pulsed light.

Referring to FIG. 1, in the present embodiment, an XY stage 15 for roughly moving a substrate 14 of an object to be processed in a two-dimensional direction and a substrate 14 placed on the XY stage 15 are provided. Observation optical system 13 for observation and this observation optical system 1
Bessel beam optical system 12 which has an optical axis in a direction different from the optical axis of the objective lens 9 of 3 and emits incident laser light to the substrate 14 as a Bessel beam, and this Bessel beam optical system 12 is perpendicular to the optical axis. And an actuator 6 for moving in the direction.

The Bessel beam optical system 12 has a first laser light source 4 for supplying incident laser light from a fourth harmonic source of an Nd: YAG solid-state laser for processing the substrate 14 on the incident side thereof, and the substrate. The second laser light source 5 supplies He-Ne laser light as an incident laser light for instructing the processing position of No. 14, and synthesizes the first laser light and the second laser light on the emission side. The dichroic mirror 2 and the conical lens 1 and the conical lens 1 that compose the combined light combined by the dichroic mirror 2 into a Bessel beam and emit it to the substrate 14, the dichroic mirror 2, and the first and second laser light sources 4, 5 Housing 3 with built-in
And a support body 31 for finely moving the accommodating portion 3 via the actuator 6.

The observation optical system 13 includes an illumination 8 for illuminating the substrate 14, a camera 10 for picking up an image of the substrate 14, an objective lens 9 located at a distance of about 10 mm from the substrate 14,
Illumination light from the illumination 8 to the substrate 14 and the substrate 14 to the camera 1
Half mirror 7 that synthesizes the optical path of the incident light to 0, and monitor TV (TV) 1 that displays an observation image from camera 10.
It is composed of 1.

In FIG. 2, the actuator 6 is constituted by stacking type piezoelectric actuators 61 and 62 which are orthogonal to each other on an imaginary plane perpendicular to the optical axis of the Bessel beam optical system 12. The optical system 12 applies a predetermined voltage to the piezo actuators 61 and 62, where the optical axis of the Bessel beam is the z-axis and two axes of a virtual plane perpendicular to the z-axis are orthogonal to each other. Thus, the optical axes of the Bessel beam can be adjusted to 20 for both the x-axis and the y-axis by moving the housing 3 and the support 31.
It is configured so that it can be moved by 0 μm.

Next, the operation of this embodiment will be described.

First, the XY stage 15 is moved and stopped so that the entire field of view on the screen of the monitor TV 11 is the polyimide film portion (not shown) on the surface of the substrate 14.

Next, the actuator 6 is arranged so that the focused spot of the He-Ne laser light from the second laser light source 5 for instructing the processing position on the surface of the substrate 14 is at the right end center on the screen of the monitor TV 12. Positioning is performed by applying a required voltage to.

At this time, He-
The moving direction of the Ne laser light is moved in the direction in which the distance between the conical lens 1 and the Bessel beam irradiation point on the surface of the substrate 14 changes.

Next, the polyimide film on the surface of the substrate 14 is shot and irradiated with an optical pulse of the laser light from the first laser light source 4 to form a via hole, and the irradiation of the optical pulse is stopped.

In this embodiment, with respect to the unevenness of the substrate 14, the distance between the substrate 14 and the objective lens 9 and the conical lens 1 is 4 mm, and even if there is a step of less than 4 mm on the surface of the substrate 14. The substrate 14 can be easily moved without the risk of hitting the objective lens 9 and the conical lens 1.

Further, in this embodiment, it was confirmed that the processing beam diameter of 1.2 μm was stably obtained even when the height of the surface of the substrate 14 went up and down by 1 mm, and the XY stage was used. 15
Is used for the coarse movement of the substrate 14 and the actuator 6 is used for the fine adjustment of the processing position, it is confirmed that the via holes are formed with a high positioning accuracy of 0.2 μm and a high throughput of 60 holes per minute. ing.

Further, in this embodiment, the XY stage 15 is used.
Since the Bessel beam can be moved by the actuator 6 in the state where the monitor TV 11 is stopped,
Processing is sequentially performed within the same field of view on the screen, and at the same time, it is possible to visually check the processing.

In the above-described embodiment of the present invention, the case where the conical lens 1 is used in the Bessel beam optical system has been described, but a hologram lens may be used instead of the conical lens 1. In that case, there are advantages that the weight of the optical system can be reduced and the cost can be kept low.

Although one embodiment of the present invention has been described above, the following embodiment is also possible.

First, the substrate 14 is placed in a chamber of a CVD (chemical vapor deposition device) having a window for introducing and observing a laser beam, and an organometallic gas is introduced into the chamber.
By irradiating the laser beam for processing and moving the actuator 6 at the same time, a thin metal wiring can be drawn by laser CVD. In this application, it has been very difficult to perform minute processing because the working distance between the lens and the substrate cannot be kept high due to the thickness of the window, etc. Alive,
It becomes extremely easy to draw a fine metal line having a width of 1 μm.

Further, a plurality of Bessel beam optical systems 12
Is arranged around the observation optical system 13 and is processed through the Bessel beam optical system 12 in an appropriate direction according to the inclination on the substrate 14, it is possible to process even a shadowed part from one direction. And the advantage that it is possible to perform processing at a plurality of locations at the same time.

[0036]

As described above, according to the present invention, the first moving means for roughly moving the workpiece in the two-dimensional direction,
An observation optical system for observing an object to be processed arranged on the first moving means via an objective lens, and an object to be processed having an optical axis in a direction different from the optical axis of the objective lens of the observation optical system. By providing a Bessel beam optical system that emits an incident laser beam with respect to the Bessel beam as a Bessel beam and a second moving unit that moves the Bessel beam optical system in a direction perpendicular to the optical axis thereof, an object to be processed having a large unevenness is formed. However, there is no risk of damaging the optical system due to contact with it, and microscopic laser processing on the order of microns is possible with a deep focal depth on the order of millimeters.

Further, at the same time as the processing, it is possible to easily visually determine whether or not there is a defect in the processing point in the visual field of the observation optical system.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of structures of a Bessel beam optical system and an actuator in this embodiment.

FIG. 3 is a configuration diagram showing an example of a conventional laser process apparatus.

[Explanation of symbols]

 1 Conical Lens 2 Dichroic Mirror 3 Housing 4 First Laser Light Source 5 Second Laser Light Source 6 Actuator 7 Half Mirror 8 Illumination 9 Objective Lens 10 Camera 11 Monitor TV (TV) 12 Bessel Beam Optical System 13 Observation Optical System 14 Substrate 15 XY stage 31 Support 61, 62 Piezo actuator

Claims (2)

(57) [Claims] 1. An object to be roughly moved in a two-dimensional direction
A first moving means for arranging and arranged on the first moving means
Of observing the processed object through an objective lens
Observation optical system and the optical axis of the objective lens of the observation optical system
The incident laser beam has different optical axes in different directions and is incident on the workpiece.
Bessel beam that emits laser light as a Bessel beam
Optical system and this Bessel beam optical system with respect to its optical axis
And second moving means for vertically moving the
The Bessel beam optical system has the object to be processed on its incident side.
The first laser light for processing is the incident laser light
And a first laser light source to be supplied by
A second laser beam for indicating a position is used as the incident laser beam.
A second laser light source for supplying light, and the first laser light source.
Dichroic for combining the light and the second laser light
Mirror and composite created with this dichroic mirror
Light is formed into a Bessel beam and emitted to the workpiece.
Laser process equipment characterized by having a lens
Place. 2. An object to be machined is roughly moved in a two-dimensional direction.
A first moving means for arranging and arranged on the first moving means
Of observing the processed object through an objective lens
Observation optical system and the optical axis of the objective lens of the observation optical system
The incident laser beam has different optical axes in different directions and is incident on the workpiece.
Bessel beam that emits laser light as a Bessel beam
Optical system and this Bessel beam optical system with respect to its optical axis
And second moving means for vertically moving the
The Bessel beam optical system is for processing the object to be processed.
For supplying the first laser light as the incident laser light
1 laser light source and indicates the processing position of the processing object
Supply a second laser beam for the incident laser beam
A second laser light source, the first laser light and the first laser light
A dichroic mirror that combines the laser light of 2
Vessels the combined light combined by the dichroic mirror of
A conical lens that is formed into a beam and is emitted to the object to be processed
And the second moving means of the Bessel beam
The first and the first that are orthogonal to each other on a virtual plane perpendicular to the optical axis
The Bessel beam having two piezo actuators
Characterized by two-dimensionally moving the optical axis of the laser
Process equipment.