Laser marking device and laser marking method

A laser marking device includes a laser emission unit configured to emit a laser beam to a first surface of an object to be processed, and a pressing unit configured to press a second surface that is opposite to the first surface of the object to be processed to make the first surface of the object to be flat. The pressing unit includes a first pressing portion configured to press an edge area of the second surface in a contact manner, and at least one second pressing portion configured to press a middle area of the second surface in a non-contact manner to maintain a separation distance from the second surface within a certain distance.

TECHNICAL FIELD

The present disclosure relates to a laser marking device and a laser marking method.

BACKGROUND ART

Many semiconductor chips are formed on a wafer in a manufacturing process of semiconductor devices. To distinguish the semiconductor chips by production lots, characters and/or numbers are marked at a position corresponding to each semiconductor chip. A laser marking device using a laser beam is used for this purpose. In the past, a lot number is marked on each chip after dicing. With the development of advanced technologies, integrated circuits (IC) are become compact and lightweight. Accordingly, to increase work efficiency and enable mass production, dicing is carried out after each semiconductor chip is marked on a wafer. However, while the wafer size increases, the thickness of the wafer decreases, and thus warpage of the wafer becomes problematic.

A wafer on which many semiconductor chips are formed may be warped in a certain direction due to self-weight, coating of a wafer surface, and other processing. Such a warpage phenomenon occurs more as the size of a wafer increases, the thickness of a wafer decreases, and an amount of contraction during curing of a coating material increases. In this state, when a deviation in the height of a processed surface of a wafer due to the warpage phenomenon is greater than a focal depth of a laser beam, the beam density of a laser output and the size of a laser beam vary according to the position of the processed surface. Thus, marking quality may deteriorate, a line width may be irregular, and a marking position may be inconstant.

DESCRIPTION OF EMBODIMENTS

Technical Problem

Provided are laser marking devices and laser marking methods.

Solution to Problem

According to an aspect of the present disclosure, a laser marking device includes a laser emission unit configured to emit a laser beam to a first surface of an object to be processed, and a pressing unit configured to press a second surface that is opposite to the first surface of the object to be processed to make the first surface of the object to be flat, in which the pressing unit includes a first pressing portion configured to press an edge area of the second surface in a contact manner, and at least one second pressing portion configured to press a middle area of the second surface in a non-contact manner to maintain a separation distance from the second surface within a certain distance.

The at least one second pressing portion may maintain a separation distance between the second pressing portion and the second surface within about 50 μm.

The at least one second pressing portion may include at least one ejection hole through which a gas is ejected toward the second surface of the object to be processed.

A pressure applied by the at least one second pressing portion to the object to be processed may be about 0.01 MPa to about 0.5 MPa.

The first pressing portion may have a ring shape and press the edge area of the second surface due to a weight thereof.

A semiconductor pattern may be arranged in the middle area of the second surface, and the semiconductor pattern may not be arranged in the edge area of the second surface.

The laser marking device may further include a work table on which the object to be processed is placed, and having an opening through which a part of the first surface of the object to be processed is exposed.

The laser marking device may further include a support unit configured to support the pressing unit and transfer the pressing unit to the second surface of the object to be processed.

The support unit may include a suction unit configured to suction and support the pressing unit and a driving unit configured to transfer the pressing unit in a vertical direction.

The support unit may further include a falling prevention unit configured to move between a first position overlapping the pressing unit and a second position that does not overlap the pressing unit to prevent falling of the pressing unit.

According to another aspect of the present disclosure, a laser marking method includes placing an object to be processed on a work table, the object to be processed including a first surface and a second surface that is opposite to the first surface, pressing the second surface of the object to be processed to compensate for a height deviation of the object to be processed, which is performed by a pressing unit, and performing marking by emitting a laser beam to the first surface of the object to be processed, wherein, in the pressing of the second surface, an edge area of the second surface is pressed by a first pressing portion, and a middle area of the second surface is pressed by at least one second pressing portion in a non-contact manner.

A separation distance between the second pressing portion and the second surface may be maintained by the second pressing portion within about 50 μm.

The second pressing portion may eject a gas toward the second surface of the object to be processed.

A pressure applied by the second pressing portion to the object to be processed may be about 0.01 MPa to about 0.5 MPa.

The first pressing portion may have a ring shape, and the edge area of the second surface may be pressed by a weight of the first pressing portion.

A semiconductor pattern may be arranged in the middle area of the second surface, and the semiconductor pattern may not be arranged in the edge area of the second surface.

The laser marking method may further include, before the pressing of the second surface, transferring the pressing unit to the second surface of the object to be processed, which is performed by a support unit.

Advantageous Effects of Disclosure

In a laser marking device and a laser marking method according to the present disclosure, even when an object to be processed is warped and is not flat before laser marking work begins, marking work is performed in a state in which an edge portion of the object to be processed where a semiconductor pattern is not formed is contacted and pressed and a middle portion of the object to be processed where a semiconductor pattern is formed is pressed in a non-contact manner, thereby providing reliable marking quality.

BEST MODE

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The thickness or size of each layer illustrated in the drawings may be exaggerated for convenience of explanation and clarity.

Terms such as “first” and “second” are used herein merely to describe a variety of constituent elements, but the constituent elements are not limited by the terms. Such terms are used only for the purpose of distinguishing one constituent element from another constituent element. For example, without departing from the right scope of the present disclosure, a first constituent element may be referred to as a second constituent element, and vice versa. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

FIG. 1is a schematic cross-sectional view of a laser marking device according to an embodiment.FIGS. 2A and 2Billustrate an example of an object T to be processed that is subject to laser processing by a laser marking device according to an embodiment.FIGS. 3A and 3Billustrate a state in which the object T to be processed is warped.

Referring toFIG. 1, the laser marking device according to the present embodiment may include a laser emission unit20, a work table10on which the object T to be processed is placed, and a pressing unit30pressing the object T to be processed. The laser marking device may further include a vision camera40.

The laser emission unit20emits a laser beam to the object T to be processed. The laser emission unit20is arranged under the object T to be processed and emits a laser beam to a lower surface of the object T to be processed, thereby performing marking work on the object T to be processed.

The work table10may include an opening H that exposes a part of the lower surface of the object T to be processed. The laser beam emitted by the laser emission unit20passes through the opening H and is irradiated to the lower surface of the object T to be processed.

The vision camera40takes an image of a semiconductor pattern P (seeFIG. 2A) provided on the object T to be processed, thereby identifying a processing position of the object T to be processed. Accordingly, precise processing work may be performed by the laser emission unit20.

Referring toFIGS. 1, 2A, and 2B, the object T to be processed may include a first surface110and a second surface120that is opposite to the first surface110. The first surface110may be a lower surface, and the second surface120may be an upper surface.

The semiconductor pattern P is arranged in a middle area122of the second surface120of the object T to be processed. The semiconductor pattern P may not be arranged in an edge area121arranged at an outer side of the middle area122of the second surface120.

For example, the object T to be processed may be a wafer, and the semiconductor pattern P may be a plurality of semiconductor chips arranged on a wafer. In this case, while a plurality of semiconductor chips are arranged on the second surface120, a plurality of semiconductor chips are not arranged on the first surface110. A plurality of semiconductor chips are arranged in the middle area122of the second surface120, but not in the edge area121of the second surface120.

A laser marking device performs a laser marking work by irradiating a laser beam to the first surface110of the object T to be processed on which the semiconductor pattern P is not arranged.

However, the object T to be processed may be warped to be convex as illustrated inFIG. 3Aor warped to be concave as illustrated inFIG. 3Bfor various reasons. For example, the object T to be processed may be warped due to the weight thereof or in a surface coating process of the object T to be processed, a heat treatment process, or other processes. Accordingly, the object T to be processed may have a height deviation Δh.

The height deviation Δh of the object T to be processed may occur by as much as the size of the object T to be processed increases, the thickness thereof decreases, and an amount of contraction of a coating material during curing increases. The height deviation Δh of the object T to be processed may be 4 mm to 10 mm.

When a laser beam is focused out of the object T to be processed due to the height deviation Δh of the object T to be processed, marking may not be performed. Even when a laser beam is focused on the object T to be processed, but the position of a focus varies, marking quality may deteriorate. For example, a line width may not be constant or a marking position may be changed.

FIGS. 4 and 5illustrate the pressing unit30of a laser marking device, according to an embodiment, in whichFIG. 4is a plan view of the pressing unit30andFIG. 5is a cross-sectional view ofFIG. 4.

Referring toFIGS. 1 and 4, the laser marking device according to an embodiment may include the pressing unit30pressing the object T to be processed to supplement or compensate for the height deviation Δh of the object T to be processed. Before or simultaneously with marking work being performed on the first surface110of the object T to be processed, the pressing unit30may press the second surface120of the object T to be processed.

The pressing unit30may include a first pressing portion310pressing the edge area121of the second surface120.

The first pressing portion310presses the edge area121of the second surface120in a contact manner.

For example, the first pressing portion310may have a ring shape. The first pressing portion310may be arranged above the object T to be processed, and may press the edge area121of the object T to be processed due to the weight thereof. In this state, since the semiconductor pattern P is not formed at the edge area121of the second surface120, even when the first pressing portion310presses the edge area121of the object T to be processed in a contact manner, the semiconductor pattern P of the object T to be processed may not be damaged.

When a height deviation of the object T to be processed is within a certain range, the height deviation of the object T to be processed may be reduced or removed by the first pressing portion310. For example, when the height deviation of the object T to be processed is less than 4 mm, the first pressing portion310may reduce the height deviation of the object T to be processed to a range in which marking quality does not deteriorate.

However, when the height deviation of the object T to be processed deviates by a certain range, for example, by about 4 mm or more, there may be a limitation in reducing the height deviation of the object T to be processed only by pressing the edge portion of the object T to be processed in a contact manner. For example, when only the edge portion of the object T to be processed is pressed by the first pressing portion310, a middle portion of the object T to be processed may warp to be convex or concave. Furthermore, when the size of the object T to be processed increases, a height deviation by the middle portion of the object T to be processed may be difficult to compensate for only by the edge portion of the object T to be processed.

Considering the above, the laser marking device according to an embodiment may further include a second pressing portion320pressing the middle area122of the second surface120.

Referring toFIGS. 4 and 5, the second pressing portion320presses the middle area122of the second surface120in a non-contact manner. A pressure applied to the object T to be processed by the second pressing portion320may be about 0.01 MPa to about 0.5 MPa. In this regard, pressing the middle area122of the second surface120in a non-contact manner may include pressing the middle area122of the second surface120in a downward direction and also pulling the middle area122of the second surface120in an upward direction.

The second pressing portion320may provide a suction force or a repulsive force according to the Bernoulli's principle to the object T to be processed. The second pressing portion320may be a Bernoulli chuck. Accordingly, the second pressing portion320may maintain a separation distance G from the second surface120within a certain distance. For example, the separation distance G between the second pressing portion320and the second surface120of the object T to be processed may be maintained within about 50 μm by the second pressing portion320.

The second pressing portion320may include at least one ejection hole321through which a high-pressure gas may be ejected toward the second surface120. The second pressing portion320is supported by a support bar323arranged across the first pressing portion310of a ring shape. The support bar323may be pneumatically connected by an articulated structure325. The gas supplied through the support bar323may be ejected toward the object T to be processed through the ejection hole321.

The high-pressure gas ejected by the second pressing portion320is discharged between the second pressing portion320and the object T to be processed. Accordingly, the Bernoulli effect is generated and thus a suction force may be generated. In contrast, when a distance between the second pressing portion320and the object T to be processed is shorter than a certain distance, a repulsive force may be applied to the object T to be processed by the high-pressure gas ejected by the second pressing portion320.

For example, when the distance between the second pressing portion320and the object T to be processed is about 50 μm to about 10 mm, a suction force is generated by the second pressing portion320, and thus the suction force may act on the object T to be processed in an upward direction. Accordingly, when the object T to be processed warps to be downwardly concave as illustrated inFIG. 3B, the object T to be processed may be made flat by the second pressing portion320.

For example, when the distance between the second pressing portion320and the object T to be processed is about 10 μm or less, a repulsive force is generated by the second pressing portion320, and thus the repulsive force may act on the object T to be processed in a downward direction. Accordingly, when the object T to be processed warps to be upwardly convex as illustrated inFIG. 3A, the object T to be processed may be made flat by the second pressing portion320.

As described above, since the second pressing portion320applies a suction force or a repulsive force to the middle portion of the object T to be processed in a non-contact manner, the middle portion of the object T to be processed may be made flat. Accordingly, when the height deviation of the object T to be processed is about 4 mm or more, the first pressing portion310and the second pressing portion320may reduce the height deviation of the object T to be processed to a range in which marking quality does not deteriorate.

FIG. 6is a perspective view of a support unit50of a laser marking device, according to an embodiment.

Referring toFIG. 6, the laser marking device according to the present embodiment may further include the support unit50that supports the pressing unit30and transfers the pressing unit30over the second surface120of the object T to be processed.

The support unit50may include a suction unit520suctioning and supporting the pressing unit30and a driving unit510transferring the suctioned pressing unit30in a vertical direction (Z1direction).

The suction unit520provides a negative (−) pressure to the upper surface of the first pressing portion310, thereby vacuum-suctioning the first pressing portion310. Accordingly, the pressing unit30is supported by the support unit50.

The driving unit510may be a motor or a cylinder. As the driving unit510operates, a transfer frame550on which the suction unit520is provided may be moved in the vertical direction (Z1direction). Accordingly, the pressing unit30may be transferred over the second surface120of the object T to be processed.

For example, the driving unit510lowers the transfer frame550until the pressing unit30approaches or contacts the second surface120of the object T to be processed. In this state, the pressing unit30is placed on the second surface120of the object T to be processed by removing the suction by the suction unit520, and thus the transfer frame550is raised by the driving unit510.

FIG. 7is a partially enlarged perspective view ofFIG. 6, describing a falling prevention unit530of the support unit50. Referring toFIGS. 6 and 7, the support unit50may further include the falling prevention unit530that prevents the pressing unit30from undesirably falling.

The falling prevention unit530may move between a first position531overlapping the pressing unit30and a second position532that does not overlap the pressing unit30. The falling prevention unit530has a “⊏” shape, and may move in a direction crossing the gravity direction of the pressing unit30. For example, the falling prevention unit530may move in a horizontal direction, for example, an X1direction.

In a state in which the falling prevention unit530is located at the first position531, even when the pressing unit30is unintentionally separated from the suction unit520, the pressing unit30is supported by the falling prevention unit530, and thus the pressing unit30may be prevented from unintentional falling.

In the above-described embodiments, an example in which the second pressing portion320of the pressing unit30includes on second pressing portion is described. However, the number of the second pressing portion320of the pressing unit30is not limited to one, and the second pressing portion320may include a plurality of second pressing portions, if necessary. For example, as illustrated inFIG. 8AorFIG. 8B, the second pressing portion320may include a plurality of second pressing portions.

FIGS. 9A to 9Dillustrate operations of a laser marking method according to an embodiment laser marking method according to an embodiment.

Referring toFIG. 9A, the object T to be processed may be placed on the work table10. The object T to be processed may include the first surface110where the semiconductor pattern P is not formed and the second surface120where the semiconductor pattern P is formed. A part of the first surface110of the object T to be processed may be exposed to the laser emission unit20through the opening H of the work table10.

The support unit50suctions and supports the pressing unit30. The pressing unit30is arranged above the object T to be processed to be spaced apart therefrom.

Referring toFIG. 9B, the pressing unit30is lowered by the support unit50toward the object T to be processed placed on the work table10. The pressing unit30is transferred by the support unit50and contacts the second surface120of the object T to be processed.

When the pressing unit30contacts the object T to be processed, the support unit50is raised after the suction to the pressing unit30is removed.

Referring toFIG. 9C, the first pressing portion310of the pressing unit30contacts the edge area121of the second surface120, and the second pressing portion320is spaced apart from the middle area122of the second surface120.

In this state, the first pressing portion310contacts and presses the edge portion of the object T to be processed due to the weight thereof, and the second pressing portion320presses the middle portion of the object T to be processed middle portion in a non-contact manner by ejecting a high-pressure gas. Accordingly, the height deviation of the object T to be processed may be compensated for by the pressing unit30including the first pressing portion310and the second pressing portion320. For example, the height deviation of the object T to be processed compensated for by the pressing unit30may be about 4 mm to about 10 mm.

Referring toFIG. 9D, the vision camera40takes an image of the semiconductor pattern P of the object T to be processed with a compensated height deviation and identifies the position of the semiconductor pattern P. A marking work is performed on the first surface110of the object T to be processed by identifying a processing position from information about the identified position of the semiconductor pattern P.