JPH11156563A - Laser beam micro marking device and marking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dot marking device and a marking method therefor which enables to obtain a down mark shape which is minute but excellent in its visibility and correctly forms such a minute dot. SOLUTION: This device is equipped with a laser oscillator (10), a beam homonizer (20) to smoothen an energy distribution of a laser beam irradiated from the laser oscillator (10), a liquid crystal mask (30) to make the laser beam into a transmittal/non-transmittal status by a control driving of the laser beam compliance with a displayed pattern, a beam profile changing means (40) to transform an energy density distribution of the laser beam into a given distribution shape form corresponding to one dot of the liquid crystal mask (30), and a lens unit (50) to form an image of a beam transmitted through the crystal mark (30) onto a semi-conductor wafer surface by a dot unit. The maximum length of one liquid crystal mask dot is 50-2,000 μm and the maximum length of one dot by the lens unit is 1-10 μm. A peripheral wall of a hole opening of the dot mark formed by the device is cut in a sharply slanted shape like, for example, a barnacle shape and a difference of contrast between inside and outside of the hole is made extremely large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standard position on a semiconductor wafer surface, a glass substrate such as a liquid crystal substrate, an electrode (pad) such as a bare chip, an IC surface, various ceramic products, and an article to be marked such as a lead portion of an IC. The present invention relates to a dot marking device and a marking method for minimizing the dot shape of a dot mark for product management or various security markings on the surface of the device and improving the optical visibility thereof.

[0002]

2. Description of the Related Art For example, in a semiconductor manufacturing process, it is necessary to set various and strict manufacturing conditions for each process. Alternatively, a marking made of a bar code or the like is displayed as dots. Thus, the number of semiconductor manufacturing steps is over 100, and many element forming processes and flattening processes are performed in each process. These treatments include, for example, resist coating, flattening of various patterns such as an insulating film and a metal film to fill gaps generated by copper wiring and the like, or to reduce and project a pattern onto the resist and develop the resist. is there.

[0003] On the other hand, the marking by dots is usually performed by irradiating a continuous pulse laser beam to a partial surface of a semiconductor wafer via an optical system. In addition, this marking is not limited to one time, and in order to know the history characteristics of each manufacturing process, the minimum necessary history data is often marked in each manufacturing process. However, since marking on a semiconductor wafer is limited to an extremely narrow area, the size and number of dots to be marked are also limited, and the marking area, dot size, and number of dots are defined by SEMI standards and the like. ing.

[0004] A semiconductor wafer on which dot marking has been performed, for example, as disclosed in Japanese Patent Application Laid-Open No. 2-299216, changes in reflectivity due to irradiation of a laser beam of a He-Ne laser, or heat waves of a normal laser beam. Is read as a change in the vibration, and various manufacturing conditions in subsequent manufacturing steps are set based on the read information. Therefore, when the above-mentioned reading is not accurately performed and the information is read as erroneous information, all of them are defective unless accidental. Most of the causes of the reading failure are based on unclear marks due to dot marking. One cause of this blur is that when the depth of the dots forming the mark is small, the dots are buried by the above-described film formation. Therefore, it is necessary to increase the depth of the dots to some extent. .

Therefore, in order to obtain a required dot depth, a portion of the semiconductor wafer is usually melted and removed in a spot shape by one irradiation of a high-energy laser beam to form dots. The molten material that has been melted and removed is highly deposited or scattered around the dot, and the scattered material adheres to the peripheral portion of the dot, making it impossible to form an element, which greatly affects the quality. Furthermore, in the case of dot marking with a YAG laser, the laser output is likely to fluctuate due to the special characteristics of the YAG laser or the Q switch operation thereof, causing variations in dot depth and size.

In order to solve this problem, for example, JP-A-59-84515 and JP-A-2-205281 disclose a method in which a pulsed laser beam having relatively small energy is applied to the same point repeatedly. . In the former, when forming one dot, the dot diameter is reduced sequentially for each pulse, and the same point is irradiated several times repeatedly to form a deep dot while sequentially reducing the hole diameter of the dot. and, in the latter, the laser pulse irradiation of the first and frequencies below 1 kH _Z, the frequency of the subsequently irradiated laser pulse as a high repetition frequency 2~5KH _Z, 0.5~1.0μm Or 1.0-
Dots having a depth of 1.5 μm are formed.

[0007]

However, the unclear reading of the dots (hereinafter referred to as "visibility").
It is certain that one of the causes is the above-mentioned depth, but even if the depth of the dot is deep, if the diameter of the opening is large, for example, it is difficult to obtain the required depth. When irradiating a sufficient laser beam, the energy density is generally a Gaussian distribution, so that the surface becomes a smooth curved surface as a whole, and there is a case where it is difficult for the reading means as described above to determine the difference from the surroundings. .

On the other hand, JP-A-2-205281 discloses a dot depth of 0.5 to 1.0 μm as described above.
Alternatively, it is specifically described that the diameter is 1.0 to 1.5 μm, but there is no description about the diameter, and the dot shape is merely introduced as a Gaussian shape.

According to the disclosure of Japanese Patent Application Laid-Open No. S59-84515, the opening diameter of the first dot is 100 to 100.
Since the depth is 200 μm and the depth is 1 μm or less, specifically, four laser light irradiations are described, the dot depth in this case is 3 to 4 μm at most.
It is. Further, from the drawings in the publication, the dot shape formed at one time is also close to the Gaussian shape.

[0010] Therefore, according to the marking method disclosed in these publications, it is considered that a dot having a required dot depth and a certain uniform size is formed, but the formed dot shape is a conventional dot shape. It must be said that the shape is close to the shape, and thus the visibility is still lacking in certainty. Also, regarding the size (diameter) of the formed dots, since no particular disclosure has been made regarding miniaturization, the conventional size is not changed.
It merely follows the values specified by the I standard, and a substantial increase in the number of dots and the dot formation area cannot be expected substantially.

The present invention has been made to solve such a conventional problem, and a specific object of the present invention is to provide an article to be marked which enables formation of dots having excellent visibility even though they are minute. An object of the present invention is to provide a dot marking device and a method thereof.

[0012]

The above objects are achieved by the inventions set forth in claims 1 to 19 of the present application. The present inventors have conducted a detailed study and analysis of this kind of conventional dot marking apparatus, method and formed dot shape anew, and the factors that ensure visibility despite being minute are mainly dot It has been found that it is impossible to achieve the ideal shape by using the conventional marking device and method.

That is, for example, as shown in FIG. 18 and disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2-205281,
According to the conventional marking device, first, a character input and a marking mode for printing on a semiconductor wafer are set in the input unit 18.
Is set by The marker controller 16 marks the dots having a predetermined depth on the wafer 15 in accordance with the set marking mode, so that the ultrasonic Q switch element 2, the internal shutter 5, the external shutter 7, the attenuator (optical attenuator) 12, and the galvanometer Controls the mirror 13 and
Marking is performed on one dot by one Q switch pulse. 1, reference numeral 1 denotes a total reflection mirror, 3 denotes an internal aperture (mode selector), 4 denotes a lamp house, 6 denotes an output mirror, 8 denotes an aperture, 9 denotes a leveling mirror, 10
Is a Galileo expander, 11 is an aperture, 14 is an f-θ lens, and 17 is a YAG laser oscillator.

According to such a general marking method,
As described above, since the energy density distribution of the laser beam applied to the semiconductor wafer surface has a Gaussian shape, the dots formed on the wafer surface are also affected by the energy density distribution, and the dot inner surface has a gentle curved surface. . These marking methods are disclosed in U.S. Pat. No. 4,522,522.
656. The feature of this patent is that the surface of the wafer is irradiated with a laser beam diameter that is 1.5 to 6.5 times the diameter of the dot to be marked, thereby preventing heat conduction to the surroundings and effectively using energy. Then, the central part of the irradiation point is melted to form a hole. In other words, this is a method of effectively utilizing the energy density distributed in the Gaussian shape of the laser light, by irradiating the energy of the low laser intensity portion corresponding to the foot of the energy density distribution shape to the periphery of the hole processing portion. The purpose of the present invention is to warm the periphery of the hole, prevent loss of heat energy due to heat conduction from the center of the hole, and effectively realize the drilling of the center. However, part of the laser energy is not directly used for drilling, but is consumed, which is not only inefficient, but also irradiates the laser around the hole, leaving a thermal history around the hole, which results in product It can have a bad effect.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and more specifically, a first object of the present invention is to obtain a dot shape having excellent visibility even for a fine dot mark. A second object is to provide a dot marking device and a marking method for accurately forming such minute dots. The other purpose is
This will be further clarified by the following description.

[0016]

The object of the present invention is to provide a marking device for marking characters, barcodes, etc. on the surface of an article to be marked by using a laser as a light source, which constitutes the invention according to claim 1 of the present invention. A laser oscillator, a beam homogenizer for smoothing an energy distribution of a laser beam emitted from the laser oscillator, a liquid crystal mask for transmitting / non-transmitting the laser beam in accordance with a pattern display, and a liquid crystal mask for the liquid crystal mask. Beam profile conversion means for forming and converting the energy density distribution of the laser beam into a required distribution shape corresponding to one dot, and a lens unit for forming an image of the transmission beam of the liquid crystal mask on a semiconductor wafer surface in dot units. The maximum length of one dot of the liquid crystal mask is 50 to 2
000 μm, and the maximum length of one dot by the lens unit is 1 to 15 μm.

Here, the articles to be marked as objects to be processed in the present invention include semiconductor wafers, glass substrates such as liquid crystal substrates, electrodes (pads) such as bare chips, IC surfaces, various ceramic products, and IC leads. There is. The semiconductor wafer is typically a silicon wafer itself, but in addition, a wafer having an oxide film (SiO ₂ ) or a nitride film (SiN) formed on the wafer surface, and furthermore, an epitaxial growth. It also includes a wafer, a wafer having a gallium arsenide or indium phosphide compound formed on its surface.

Regarding the visibility with respect to the hole, it can be understood that the visibility increases when there is a large difference between the light reflection direction and the amount of reflection in the hole and its periphery. Therefore, as described above, when the hole is relatively deep in relation to the opening diameter, the visibility becomes high, because the reflected light inside the hole incident at a fixed incident angle is not uniform in the reflection direction. Due to the irregular reflection, the amount of reflected light coming out from the opening of the hole is reduced, while the reflected light in the periphery is reflected in a certain direction, assuming that the periphery of the hole is a smooth surface. Increases the brightness. It can be said that the visibility is high when the difference between the light and dark is large.

FIG. 16A shows the direction of light reflected from a conventional hole having a dot shape having a relatively shallow depth with respect to the hole diameter and having a portion deposited by melting and surrounding the hole as described above. And the visibility of the hole. As can be understood from this drawing, there is reflected light reflected in the same direction as the hole peripheral portion on the deposition portion and the hole bottom surface. For this reason, there is not much difference in brightness between the reflected light from the hole and the reflected light in the peripheral portion, and the visibility is reduced. On the other hand, FIG.
As is clear from (b), in the case of a dot-shaped hole having a relatively large depth with respect to the hole diameter, and at the same time, as described above, in the dot-shaped hole formed of a smooth surface having no molten deposit around the hole, Despite the fact that the reflected light from the hole has almost no reflected light from the inside of the hole, the difference in brightness between the hole and the surrounding area is large, the visibility is high, and the reading of dots is difficult. It will surely be done.

A more detailed study of the shape of the hole that enhances visibility has been made in detail. As the inner wall surface at the opening in the vertical cross section of the hole is inclined at a steep angle, the difference in brightness between the hole and its peripheral portion increases. It turned out to be. Most preferably, a typical hole shape is a wisteria pot-shaped and has a deep shape.

In order to form a minute dot having such a shape, it is necessary to control the quality and quantity of the laser beam irradiated for each dot with high precision. In order to obtain a laser beam having a small diameter as referred to in the present invention from a laser beam having a large beam diameter, a high-quality and high-output laser beam is required. Is difficult, and even if the aperture is narrowed down, it is difficult to imagine that the actual processing can be performed because the exit angle of the lens becomes large and the depth of focus becomes extremely small. Also, an ultra-precision lens system is required in terms of resolution and the like. When such a lens system is provided, the equipment cost is further increased, and it is impossible to apply the system from the viewpoint of economy.

Therefore, as a result of further studies, the present inventors have found that in order to realize the miniaturization of dot marks with an ordinary lens system, the laser light itself emitted from the laser oscillator is required for marking one dot. It has been found that it is necessary to divide and convert the laser beam into a small diameter laser beam having sufficient energy and to convert the energy density distribution of the laser beam for each dot into a profile suitable for processing into the aforementioned hole shape. It has also been found that in order to form such a suitable and uniform profile, it is necessary to smooth the energy density distribution in the laser beam of each dot before the conversion in the previous stage.

In order to obtain a light source for miniaturization, a liquid crystal capable of driving and controlling light transmission / non-transmission arbitrarily in each liquid crystal unit of the liquid crystal mask based on various data written in the central control unit is formed in a matrix. It is rational to employ a liquid crystal mask arranged in a matrix.

In order to convert the energy density distribution of laser light emitted from a laser oscillator having a Gaussian energy density distribution into a smoothed shape similar to, for example, a top hat shape, a fly-eye lens, Use a beam homogenizer equipped with a method that collectively illuminates the mask surface using binary optics and cylindrical lenses, and a method that operates a mirror on the mask surface by driving a mirror with an actuator such as a polygon mirror or mirror scanner. Can be.

Further, a beam profile converter for re-converting the laser beam whose energy density distribution has been smoothed by the above-mentioned beam homogenizer into an energy density distribution profile capable of obtaining the above-mentioned preferred hole shape will be described later, for example. As described above, a diffraction optical element, a holographic optical element, an aperture mask or a liquid crystal mask having an absorption / transmission region, a concave or convex microlens array, and the like can be given.

That is, in the present invention, FIG. 3 shows the energy density distribution of a beam emitted from a laser oscillator as described above and whose energy density distribution has been smoothed by a beam homogenizer. 4 schematically illustrates a process of forming various holes obtained when the profile is converted into a profile of an energy density distribution corresponding to hole processing of a shape.

The point to be noted in this figure is that a hole shape having a steep inclination angle on the inner wall surface can be obtained by reducing or eliminating the energy density near the optical axis of the laser beam. Of course, since these figures are schematic, they are drawn to the extreme, but if the above-mentioned energy density distribution shape is selected appropriately, holes of various shapes can be obtained. Proven by

The minute dots of the present invention formed on the surface of a semiconductor wafer are defined as having a maximum length of one dot of 50 to 20.
A reduced image in which a laser beam transmitted through a liquid crystal mask of 00 μm is obtained through a lens system, that is, one side length of one dot of laser light transmitted through the liquid crystal mask is reduced to 1/50 to 1/200 through a lens unit, This is the size of a dot mark formed by irradiating the wafer surface with the maximum length of one dot being 1 to 15 μm.

These values are, for example, 100 μm, which is the maximum value of the dot mark size allowed by the SEMI standard.
Compared with, it is 3/20 to 1/100, and it can be understood how small the size is.

On the other hand, as described above, in a plurality of manufacturing steps of a semiconductor substrate, film formation and etching are repeated on a marking portion in each of the steps, so that the surface is gradually roughened or There is a high possibility that the mark hole becomes shallow. In particular, dot marks having a small diameter as described above are susceptible to the influence and significantly reduce the visibility described above.

Therefore, in the invention according to claim 2 of the present application, in addition to the above configuration, the processing depth for each dot is defined as 0.5 to 10 μm. By defining the processing depth in the range of 0.5 to 10 μm in addition to the hole shape described above, even if processing such as film formation or etching is repeatedly performed on the marking portion, the difference in brightness between the dot mark and the periphery is obtained. Is maintained, and visibility is ensured.

Generally, in this type of dot marking using a laser beam, in order to prevent particles from scattering and adhering to the wafer surface, a hole is formed mainly using a melting phenomenon called a soft mark. A raised portion is formed in the periphery, and the shape becomes different from the energy density distribution shape of the laser beam. FIG. 4A shows a hole shape formed by a general laser beam having a conventional Gaussian energy density distribution, and FIG. 4B shows a hole shape formed by the present invention. . FIG.
(A) and (b) show the difference in brightness between the hole and its peripheral portion when each dot mark having the hole shape is read by an optical reading device.

As can be understood from these figures, in the conventional soft mark, since the hole is shallow and the vertical cross-sectional shape merely forms a gentle curved surface, the difference in brightness between the hole and the periphery is originally small. In addition, the surface of the hole is shaved by a process such as chemical mechanical polishing (hereinafter, referred to as CMP) or a thick film is formed in the hole, and the depth of the hole is further reduced. The difference in lightness and darkness between the hole and the periphery thereof is further reduced.

On the other hand, according to the present invention, the laser beam is formed by converting the energy density distribution shape of the laser beam into a shape having a steep inclination angle and a shape suitable for obtaining a deep hole shape by the beam profile converter. According to the hole shape, even if a plurality of film forming processes, etching, and the like are performed after the marking, the decrease in the brightness difference is small, and the visibility is maintained for a long time.

The invention according to claim 3 specifies that the beam profile conversion means may be arranged before or after the liquid crystal mask. That is, a laser beam emitted from a laser oscillator is once formed into a profile having an energy density distribution with a uniform peak value through a beam homogenizer, and then divided into each dot unit through a liquid crystal mask or a beam profile converter. Then, as described above, each dot is converted into an energy density distribution having a desired shape and a profile of the same shape.

Thus, the invention according to claim 4 defines the arrangement interval between the liquid crystal mask and the beam profile converter. This is an important factor in that the image formed on the wafer surface does not collapse. That is, the maximum length of one dot of the liquid crystal mask is set to 0.1 to 10 times the arrangement interval between the beam profile conversion means and the liquid crystal mask. By defining the arrangement interval in such a range, the image formed on the wafer surface does not collapse.

Further, in the invention according to claim 5, in order to apply laser light energy necessary and sufficient to perform hole processing for dot marking on the wafer surface, for example, the driving voltage of a liquid crystal mask is controlled to control the driving voltage. The energy of the laser beam and / or the shape of its peak value is controlled by controlling the transmittance of the liquid crystal mask or changing the energy density distribution shape by the beam profile conversion means at the same time.

As the beam profile converting means, an optical member utilizing a diffraction phenomenon, an optical member utilizing a reflection phenomenon, an optical member utilizing a refraction phenomenon, etc. Can be adopted. The most desirable dot shape is a wisteria pot type, and the energy density distribution shape of the laser beam in this case is shown in FIG.
As shown in (b), the point of the Gaussian shape is designed to have a concave shape. Needless to say, in the present invention, the dot shape is not limited to the above-mentioned wisteria pot type. For example, as shown in FIG. In some cases, a divided energy density distribution shape is adopted.

The minute marking method of the present invention is carried out using the above minute marking device. A typical method is the invention according to claim 9, wherein the beam homogenizer equalizes the energy distribution of the laser beam emitted from the laser oscillator, and the maximum length of one dot is 50 to 2000 μm. Driving and controlling the liquid crystal mask to form a desired pattern, and irradiating the liquid crystal mask with a laser beam equalized by the beam homogenizer; A dot matrix having a size, forming an energy density distribution of a laser beam passing through the beam profile conversion unit into a desired shape in dot units, and forming the laser beam into a desired shape by the beam profile conversion unit. Each laser beam for each dot is applied to the laser The's unit maximum length of one dot to 10
It is characterized in that it is reduced to a size of μm and is imaged on the surface of the semiconductor wafer. Further, as in the invention of claim 13, the processing depth of each dot is 1.5 to 10
μm is desirable for the reasons described above.

The method of irradiating the liquid crystal mask with a laser beam employs a method of irradiating the liquid crystal mask by batch irradiation or by scanning the liquid crystal mask with a laser beam. In the case of batch irradiation, it is desirable to divide the marks and display the pattern on the liquid crystal mask. In the case of irradiating all the marks collectively, it is easy to increase the size of the device, which increases the cost and the space occupied by equipment. However, it is difficult to employ the scanning method unless there is a special situation. However, when the scanning method is adopted, these problems are almost eliminated, and thus the scanning method is generally employed. In the case of employing the division method or the scanning method, one irradiation range is about 100 pixels of the liquid crystal mask in the top hat type energy density distribution laser beam converted through the homogenizer in the present invention. The range of the number of dots can be grasped at one time. Of course, the above numerical range varies depending on the laser output and its cross-sectional shape.

[0041] The conversion of the energy density distribution of the laser beam by the beam profile conversion means may be performed as follows.
In this case, the conversion may be performed before or after the transmission of the liquid crystal mask. In this case, the arrangement interval between the beam profile conversion unit and the liquid crystal mask is set to one dot of the liquid crystal mask. Maximum length of 0
It is desirable to set it to 10 times. Further, preferably, the transmittance of the liquid crystal mask is controlled by controlling a driving voltage, and the energy and / or the peak shape of the transmitted beam is controlled.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is an explanatory view schematically showing a marking device for forming fine dot markings of the present invention and the marking principle, and FIG. 2 is a schematic diagram showing the principle of forming fine markings according to a liquid crystal pattern. FIG.

In FIG. 1, reference numeral 10 denotes a laser oscillator,
20 is a beam homogenizer, 30 is a liquid crystal mask, 40 is a beam profile converter, 50 is an imaging lens unit, and W is a semiconductor wafer. Here, in this embodiment, a semiconductor wafer is illustrated as the article to be marked. In the present embodiment, the semiconductor wafer is not only a silicon wafer but also a wafer having an oxide film or a nitride film formed on the surface of the wafer, or a semiconductor wafer grown epitaxially, gallium arsenide, indium phosphide compound, etc. Is a generic name for general semiconductor wafers formed by the above method.

In the present embodiment, a laser beam having a Gaussian-shaped energy density distribution emitted from the laser oscillator 10 is first passed through a beam homogenizer 20 to form a top-hat type energy density distribution having a substantially uniform peak value. Form into shape (B).

The laser beam having a uniform energy density distribution is applied to the surface of the liquid crystal mask 30. At this time, the liquid crystal mask 30 can drive and display a required marking pattern on the mask as is widely known, and as shown in FIG. 2, the laser light can transmit light in the pattern display area. The dot portion in the state is transmitted. The energy density distribution of each transmitted light after being divided for each dot and transmitted is the same as the shape (B) formed by the beam homogenizer 20, and is uniformly distributed.

In this embodiment, the area irradiated to the liquid crystal mask 30 at one time is 5 × 10 to 10 × 1 in terms of the number of dots.
It is 0, and this is irradiated collectively with laser light.
In many cases, the required number of dot marks cannot be satisfied with such a number of dots. Therefore, the mark pattern is divided into several sections, sequentially displayed on a liquid crystal mask, and the entire mark pattern is combined by switching the patterns to the wafer. It is formed on the surface. In this case, when an image is formed on the wafer surface, the wafer or the irradiation position must be controlled and moved. As such a control method, various methods known in the art can be adopted.

In this embodiment, the liquid crystal mask 30
Then, the laser light of the dot unit that has passed through is irradiated on the beam profile converter 40. The beam profile converters 40 are similarly arranged in a matrix corresponding to the individual liquid crystals arranged in a matrix of the liquid crystal mask 30. Therefore, the laser light transmitted through the liquid crystal mask 30 passes through the beam profile converter 40 for each dot in a one-to-one correspondence, and the laser light having the energy density distribution smoothed by the beam homogenizer 20 is obtained. This is converted into an energy density distribution shape necessary for forming a minute hole shape unique to the present invention. In this embodiment, the laser beam after passing through the liquid crystal mask 30 is passed through the beam profile converter 40 to convert the energy density distribution shape as described above. Profile converter 40
And the profile may be converted.

The laser beam that has passed through the beam profile converter 40 is converged by the lens unit 50 and is applied to a predetermined position on the surface of the semiconductor wafer W, and required dot marking is performed on the surface. Here, when it is intended to form micron-level markings uniformly on a plurality of wafer surfaces, it is necessary to adjust the distance between the marking surface and the condenser lens and the optical axis alignment in micron units.
According to the present embodiment, focus detection measures height by a confocal method generally used in laser microscopes and the like, and feeds back this value to a fine positioning mechanism in the vertical direction of the lens to automatically focus. Positioning is performed. Also,
For the alignment of the optical axis and the positioning and adjustment of the optical components, generally known methods are employed. For example, a screw adjustment mechanism or the like is used to adapt to a preset reference spot through guide light such as a He-Ne laser. Adjust by This adjustment need only be performed once during assembly.

The beam homogenizer 20 emits a laser beam having, for example, a Gaussian energy density distribution.
Optical components for shaping into a smoothed energy density distribution shape. As the optical component, for example, a fly-eye lens, binary optics, or a cylindrical lens is used to irradiate the mask surface at once, or scan the mask surface by driving a mirror such as a polygon mirror or a mirror scanner. There is.

The beam profile converter 40 is an optical component for converting the energy density distribution smoothed by the beam homogenizer 20 into an optimum energy density distribution shape to obtain a dot shape unique to the present invention. In addition, the profile of the energy density distribution of incident laser light is converted into an arbitrary shape by arbitrarily changing the light transmittance at a laser irradiation point, such as a diffraction phenomenon, a refraction phenomenon, or the like.

FIGS. 3A to 3C show typical examples of the shape of a dot mark formed based on the shape of the energy density distribution converted by the beam profile converter 40 according to the present invention. FIG. 4 shows a process for forming dot marking in units of one dot by using a laser beam, and as shown in FIG.
The laser beam having the energy density distribution smoothed by the beam profile converter 40 shown in FIG.
1) to the energy distribution shape (B) shown in (c-1). In FIG. 7A, the light beam has a Gaussian shape having a large peak value. When the light beam passes through the imaging lens unit 50 and irradiates the reduced image to the irradiation point of the semiconductor wafer W, the wafer surface becomes A dot mark having a large dot depth is formed.

In FIG. 5B, the beam homogenizer 20
Is converted into an energy density distribution shape (B) in which the vicinity of the top of the Gaussian shape is concavely depressed. This is reduced by the imaging lens unit 50 and the semiconductor wafer W
(B-1), the dot depth is deep on the wafer surface, and the inner wall surface is formed into a shape that falls at a steep inclination angle toward the bottom surface. When the laser light having the energy density distribution smoothed by the beam homogenizer 20 is converted into a plurality of Gaussian energy densities by the beam profile converter 40 as shown in FIG.
The dot shape formed as described above is shown in FIG.
As shown in 2), a dot shape is obtained in which the inner peripheral wall surface of the dot drops sharply and the bottom has an uneven surface.

The dot mark formed by the apparatus of the present invention having such a shape is different from the shape of the conventional dot mark shown in FIG. 4A, for example, and has a large contrast between the dot and its surroundings as shown in FIG. Is obtained,
No error occurs in mark reading even if various processing is performed thereafter. In other words, as described above, in a dot mark having a relatively large depth relative to the dot diameter, and at the same time, in a dot mark having a smooth surface in which no molten deposit exists around the dot, the reflected light around the hole has a directionality. Obtained, the reflected light from the inside of the hole is scattered inside and almost disappears, so the difference in brightness between the hole and its surroundings increases, and the visibility increases,
Dots can be read reliably. Furthermore,
As the inner wall surface of the opening in the vertical cross section of the dot inclines downward at a steep angle, the difference in brightness between the hole and its peripheral portion increases even for a dot mark having a minute dimension, further securing visibility. Is done.

In the present invention, the minute dot mark has a maximum length in a size range of 1 to 15 μm and a hole depth of 0.5 to 10 μm. In order to form dot marks of such dimensions, one dot per dot of the liquid crystal mask is used in order to prevent image formation at an irradiation point on the surface of the semiconductor wafer W due to the resolution of the reduction lens unit or the like. The side length needs to be 50 to 2000 μm. Furthermore, even if the arrangement interval between the beam profile conversion means and the liquid crystal mask is too large or too small, the semiconductor wafer is affected by peripheral light rays or by the instability of the optical axis. Disturbance is likely to occur in surface imaging. Therefore, in the present invention,
In FIG. 17, the arrangement interval X between the beam profile converting means 40 and the liquid crystal mask 30 is set to
It is necessary to set the maximum length Y of one dot of 0 to 0 to 10 times. By defining the arrangement interval in such a range, the image formed on the wafer surface becomes clear.

Next, a method of converting the energy density distribution of the laser beam by the beam profile converter 40 of the present invention will be described based on a specific example. FIGS. 6 and 7 are diagrams for explaining the conversion of the energy density distribution by the beam profile converter utilizing the diffraction phenomenon. In this embodiment, a diffractive optical element (Diffractive O-ptical Element) is used. In FIG. 6B, a 5 × 5 dot liquid crystal mask 30 and a corresponding 5 × 5 dot beam profile conversion mask 40-1 made of a diffraction optical element are arranged in parallel. It is a schematic diagram. FIG. 6A shows the beam profile conversion mask 4 via the liquid crystal mask 30.
It shows a conversion state of the energy density distribution of the laser beam when passing through 0-1. FIG. 7 is a plan view schematically showing the structure of the diffraction optical element. As shown in FIG. 7, a rectangular outer peripheral portion of the laser beam transmitted through the diffraction optical element is transmitted as it is, and is incident on the central portion. Laser light is diffracted in the outer peripheral direction.

That is, the laser beam whose peak value has been smoothed by the beam homogenizer 10 is incident on one element of the beam profile conversion mask 40-1.
The incident light at the outer peripheral portion is transmitted linearly, the incident light at the central portion is diffracted toward the outer peripheral side, and the energy density increases toward the outer peripheral portion as shown in FIG. A density distribution shape in which the energy density gradually decreases. The angle and interval of the diffraction are calculated by determining the diffraction conditions of the laser beam. When a reduced image of the laser light converted into such an energy density distribution is applied to an irradiation point on the surface of the semiconductor wafer, the dot mark formed has a large amount of energy in the peripheral portion, so that the peripheral wall of the hole is quickly melted without energy loss. As well as being processed, it melts similarly in the center of the hole due to the strong heat conduction around,
As shown in FIG. 4B, the hole is formed in a deep shape with a vertical cross section that is almost rectangular.

FIG. 8 shows a manufacturing method of another embodiment of the beam profile converter utilizing the diffraction phenomenon as in the above embodiment. A holographic optical element is used as the beam profile converter shown in FIG. Have been. The manufacturing method is as shown in FIG.
Through a relay lens 42 and a half mirror 43 to transmit a film type transmission hologram 44
An interference fringe is recorded on the hologram 44 by forming an image on the hologram 44 and making it interfere with a uniform reference light as object light. By causing reproduction light (for example, laser light transmitted through the liquid crystal mask 30) having the same uniform profile as the reference light to enter the hologram 44, the beam profile existing on the aperture mask 41 on the hologram 44 is reproduced. You. The holographic optical element thus manufactured can be handled as an optical element similar to the beam profile conversion mask 40-1 in the above embodiment.

The opening mask 41 is formed, for example, as shown in FIG.
As schematically shown, a rectangular outer peripheral region is configured as a light shielding portion 41a, a central region is configured as a rectangular diffraction grating semi-transmitting portion 41b, and an intermediate region is configured as a transmitting portion 41c. According to the present invention, as shown in FIG.
It is also possible to configure the semi-transmissive portion 41b as a simple semi-transmissive portion and to use this as it is as a beam profile converter.

FIG. 11 shows a beam profile converter in which the aperture masks 41 are arranged in a matrix and the aperture mask 4.
1 shows an energy density distribution of a laser beam transmitted through No. 1. As can be understood from the figure, when the smoothed laser light passes through the aperture mask 41, the amount of light transmitted through the semi-transmissive portion is the largest and uniform, and the amount of semi-transmitted light transmitted through the central portion is rectangular. It has a reduced energy density by half. When the surface of the semiconductor wafer W is irradiated with the laser beam having the energy density distribution thus converted, dot marking having an initial hole shape is efficiently performed without heat dissipation as in the above embodiment. .

FIG. 12 shows an embodiment of a beam profile converter using a light transmission type liquid crystal mask. According to the drawing, a 3 × 3 dot liquid crystal mask 45 is used for 1 dot marking. And this liquid crystal mask 4
The liquid crystal at the center of No. 5 is set in a non-driving state to be a non-transmitting state.
On the other hand, the other liquid crystal is driven to be in the transmission state. With this configuration, when a smoothed laser beam is incident on the liquid crystal mask 45, it is converted into a laser beam having an energy density distribution shown in FIG. Liquid crystal mask 4
By increasing the number of dots of 5, a pattern consisting of an arbitrary transparent portion and a non-transparent portion can be formed.

FIG. 13 shows an embodiment of a beam profile converter utilizing the refraction phenomenon and a conversion state of its energy density distribution. In the example shown in the figure, a convex microlens array is arranged in a matrix as a beam profile converter 47, and the energy density distribution of laser light passing through the beam profile converter 47 in dot units is shown in FIG. As shown in FIG. 7A, a dot marking having an elongated Gaussian shape is formed. If the shape is arbitrarily reduced, dot marking having a larger hole depth than the opening size is formed.

FIG. 14 shows a beam profile converter 48 in which an aperture mask in which a large number of apertures are simply formed in a matrix is used.
An example is shown in which the information is used as "." According to this example, the beam profile, that is, the beam shape itself can be arbitrarily controlled by changing the size and shape of the aperture using the diffraction phenomenon. For example, when the shape of the opening is rectangular as shown in FIG. 15A, the laser light whose energy density distribution has been smoothed by the beam homogenizer 10 passing through the rectangular opening is converted into a substantially circular laser light. In the case where the laser beam is converted and adopts an opening shape in which each side of the square is confined inside as shown in FIG. 7B, the laser beam after passing through the opening has a substantially square cross section.

As is clear from the above description, according to the dot marking apparatus and the marking method according to the present invention, the conventional semiconductor wafer surface has a thickness of 3/20 to 1/100 of the conventional size.
In addition to being able to form minute dot markings of a size, the dot shape is deeper than the hole diameter, and the peripheral wall of the hole is inclined downward at a steep angle. Even if various coating processes are performed on the wafer surface after marking and a coating is formed on each dot after marking, the difference in brightness between the inside of the hole and the periphery is ensured, and the subsequent reading is accurate. Done. In addition,
The present invention is not limited to the above-described embodiments, but naturally includes technical ranges that can be easily changed by those skilled in the art from those embodiments.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a process of converting a small dot marking apparatus of the present invention and an energy density distribution (beam profile) of a laser beam.

FIG. 2 is an explanatory view schematically showing a process of converting an energy density distribution of a dot mark and a laser beam formed according to a display pattern of a liquid crystal mask in the device of the present invention.

FIG. 3 is an explanatory diagram of a dot shape example formed based on a beam profile conversion shape by a beam profile converter in the apparatus of the present invention.

FIG. 4 is a comparison diagram of a conventional dot mark, a dot mark according to the present invention, and the reflected light path.

FIG. 5 is a comparison diagram schematically showing a difference in brightness between a conventional dot mark and a dot mark according to the present invention.

FIG. 6 is an explanatory diagram schematically showing an example of a beam profile conversion shape when the beam profile converter utilizing the diffraction phenomenon is employed.

FIG. 7 is a plan view of a diffraction optical element used in the beam profile converter.

FIG. 8 is an explanatory view showing a method of manufacturing a holographic optical element utilizing a diffraction phenomenon.

FIG. 9 is an explanatory diagram showing an example of a beam profile converter using the holographic optical element and a beam profile conversion shape using the converter.

FIG. 10 is a plan view of an aperture mask having an absorption / transmission region.

FIG. 11 is an explanatory diagram schematically illustrating an example of a beam profile conversion shape by a beam profile converter including the aperture mask.

FIG. 12 is a plan view showing an example of a beam profile converter using a liquid crystal mask.

FIG. 13 is an explanatory diagram of a beam profile converter using a convex lens array utilizing a refraction phenomenon and an example of a converted shape of a beam profile.

FIG. 14 is a schematic configuration diagram of a dot marking device employing a beam profile converter using a simple aperture mask.

FIG. 15 is a comparison diagram of an opening shape of a simple opening mask and a dot mark corresponding to the shape.

FIG. 16 is an explanatory diagram of visibility by a hole shape.

FIG. 17 is an explanatory diagram showing an arrangement relationship between a liquid crystal mask and a beam profile converter.

FIG. 18 is an overall configuration diagram showing an example of a general dot marking device using a laser beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Laser oscillator 20 Beam homogenizer 30 Liquid crystal mask 40 Beam profile converter 40-1 Beam profile conversion mask 41 Opening mask 41a Shielding part 41b Semi-transmission part 41c Transmission part 45 Liquid crystal mask 46-48 Beam profile converter 50 Reduction lens unit

Claims (19)

[Claims] 1. A marking device for marking characters, bar codes, etc. on the surface of an article to be marked using a laser as a light source, comprising: a laser oscillator; and a beam for smoothing an energy distribution of a laser beam emitted from the laser oscillator. A homogenizer, a liquid crystal mask that transmits / non-transmits the laser beam in accordance with the pattern display, and a shape conversion of the energy density distribution of the laser beam into a required distribution shape corresponding to one dot of the liquid crystal mask. And a lens unit for imaging the transmitted beam of the liquid crystal mask in dot units on the surface of the semiconductor wafer, wherein the maximum length of one dot of the liquid crystal mask is 50 to 2,000.
μm, and the maximum length of one dot by the lens unit is 1-1.
A minute marking device using a laser beam, which is 5 μm. 2. The processing depth of each dot is 0.5 to 0.5.
2. The micro-marking device according to claim 1, which is 10 [mu] m. 3. The micro-marking apparatus according to claim 1, wherein said beam profile conversion means is arranged before or after said liquid crystal mask. 4. The micro-marking device according to claim 3, wherein the maximum length of one dot of the liquid crystal mask is 0.1 to 10 times the arrangement interval between the beam profile conversion means and the liquid crystal mask. 5. The micro-marking apparatus according to claim 1, further comprising control means for controlling energy and / or peak value of a transmitted beam of the liquid crystal mask. 6. The micro-marking apparatus according to claim 1, wherein said beam profile converting means comprises an optical member utilizing a diffraction phenomenon. 7. The micro-marking apparatus according to claim 1, wherein said beam profile converting means comprises an optical member utilizing a reflection phenomenon. 8. The micro-marking apparatus according to claim 1, wherein said beam profile conversion means comprises an optical member utilizing a refraction phenomenon. 9. The micro-marking apparatus according to claim 5, wherein a conversion density distribution of the laser beam by the beam profile conversion means has a Fujitsubo-shaped dot shape. 10. A method for forming fine markings using the apparatus according to claim 1, wherein the beam homogenizer equalizes an energy distribution of a laser beam emitted from the laser oscillator. Driving and controlling the liquid crystal mask having a length of 50 to 2000 μm to form a desired pattern, and irradiating the liquid crystal mask with a laser beam uniformed by the beam homogenizer; Forming a dot matrix of the same size corresponding to the dot matrix of the mask, shaping the energy density distribution of the laser beam passing through the beam profile conversion unit into a desired shape in dot units, and the beam profile conversion unit 1 shaped into the desired shape Each laser beam for each laser beam is reduced by the lens unit so that the maximum length of one dot is 1 to 10 μm, and is imaged on the surface of the article to be marked. Method. 11. The method according to claim 10, wherein the liquid crystal mask is irradiated with a laser beam at a time. 12. The micro-marking method according to claim 10, wherein the laser beam is scanned and irradiated on the liquid crystal mask. 13. The processing depth of each dot is 0.5 to 0.5.
The fine marking method according to claim 11, wherein the thickness is 10 μm. 14. The micro-marking method according to claim 10, wherein the conversion of the energy density distribution of the laser beam by the beam profile conversion means is performed before or after transmission through the liquid crystal mask. 15. The micro-marking method according to claim 14, wherein an arrangement interval between the beam profile conversion means and the liquid crystal mask is set to 0 to 10 times a maximum length of one dot of the liquid crystal mask. 16. The method according to claim 10, wherein energy or a peak value of a transmitted beam of the liquid crystal mask is controlled. 17. The micro-marking method according to claim 10, wherein said beam profile conversion means comprises an optical member utilizing a diffraction phenomenon, and converts the energy density distribution of said laser beam utilizing said diffraction phenomenon. 18. The micro-marking method according to claim 10, wherein said beam profile conversion means comprises an optical member utilizing a reflection phenomenon, and converts the energy density distribution of said laser beam utilizing said reflection phenomenon. 19. The micro-marking method according to claim 10, wherein said beam profile converting means comprises an optical member using a refraction phenomenon, and converts the energy density distribution of said laser beam using said refraction phenomenon.