JP2012227322A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mechanical strength of a semiconductor device and allow formation of a mark on a rear face of the semiconductor device.SOLUTION: A semiconductor device comprises a mark 6 formed on a rear face 1X of a semiconductor substrate by a polishing trace 4 and a fractured layer 5. Polishing traces 4 and fractured layers 5 are removed in the regions other than the portion where the mark 6 on the rear face 1X of the semiconductor substrate is formed.

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof.

  In recent years, semiconductor chips (semiconductor devices) are becoming thinner. Thinning of the semiconductor chip is performed by polishing the back surface of the semiconductor substrate. As the semiconductor chip becomes thinner, the mechanical strength of the semiconductor chip, that is, the chip bending strength is lowered. For this reason, in order to increase the mechanical strength of the semiconductor chip, after the back surface of the semiconductor substrate is polished, a mirror surface treatment is performed to mirror the back surface of the substrate. The mirror finishing process is also referred to as a flattening process for flattening the back surface of the substrate.

  On the other hand, in order to ensure high reliability of the semiconductor chip, marks such as letters, numbers, and symbols have been formed on the back surface of the semiconductor chip for traceability. For example, the back surface of a substrate substrate is irradiated with a laser to form identification data (ID: Identification Data) such as an identification number as a mark.

JP 2000-114129 A JP 2001-85285 A Japanese Patent No. 3789802

  By the way, when a mark is formed on the back surface of the substrate, the mark forming portion of the back surface of the substrate that has an uneven surface such as a polishing mark or a satin surface is irradiated with a laser, and a melt mark or a melt layer generated thereby. Is generally used as a mark. In this case, in order to ensure the visibility of the mark, the periphery of the mark needs to be an uneven surface, so that the majority of the back surface of the substrate is an uneven surface.

However, if the majority of the back surface of the substrate is an uneven surface, or if there are polishing marks or crushed layers on the majority of the back surface of the substrate, the mechanical strength of the semiconductor chip is lowered.
On the other hand, in order to perform a mirror surface treatment such as a treatment for flattening the uneven surface or a treatment for removing a polishing mark or a crushed layer on the back surface of the substrate and forming a mark having visibility, a mirror treatment treatment is performed. The back surface of the substrate is engraved with a laser, for example, and a mark is formed by a recess.

However, when the mark is formed by engraving the back surface of the substrate, fine cracks are generated in the substrate or a crushed layer is formed, so that the mechanical strength of the semiconductor chip is lowered.
Therefore, it is desired to form a mark on the back surface of the semiconductor chip while improving the mechanical strength of the semiconductor chip.

This semiconductor device is provided with a mark formed by a polishing mark and a crushed layer on the back surface of the semiconductor substrate, and the polishing mark and the crushed layer in a region other than a portion where the mark on the back surface of the semiconductor substrate is formed is removed. Is a requirement.
In this method of manufacturing a semiconductor device, the back surface of the semiconductor substrate is polished, the region other than the portion on the back surface of the semiconductor substrate where the mark is formed is irradiated with a laser to remove the polishing marks and the crushed layer, and the remaining polishing marks and It is a requirement to form a mark with a fractured layer.

  Therefore, according to the present semiconductor device and the manufacturing method thereof, there is an advantage that the mark can be formed on the back surface while improving the mechanical strength.

(A)-(D) are typical perspective views for demonstrating the manufacturing method of the semiconductor device of this embodiment. (A)-(D) are typical perspective views for demonstrating the manufacturing method of the semiconductor device of this embodiment. (A), (B) is a schematic diagram for demonstrating the laser processing process in the manufacturing method of the semiconductor device of this embodiment, Comprising: (A) irradiates the laser to one chip | tip contained in a wafer. It is a top view which shows the state which exists, (B) is sectional drawing which follows the AA 'line of (A). (A), (B) is a schematic diagram for demonstrating the laser processing process in the manufacturing method of the semiconductor device of this embodiment, Comprising: (A) is after irradiating the laser to one chip | tip contained in a wafer. It is a top view which shows the state of (A), (B) is sectional drawing which follows the AA 'line of (A). It is a typical top view which shows the area | region (mark area) which leaves a grinding | polishing trace and a crushing layer and forms a mark in the semiconductor device (semiconductor chip) of this embodiment. It is a typical perspective view which shows the structure of the laser irradiation apparatus used in the laser processing process of the manufacturing method of the semiconductor device of this embodiment. It is a schematic diagram for demonstrating the scanning method of the laser spot in the laser processing process of the manufacturing method of the semiconductor device of this embodiment. It is a typical perspective view for demonstrating the laser marking process of a 1st comparative example. (A), (B) is a schematic diagram for demonstrating the laser marking process of a 1st comparative example, Comprising: (A) is a plane which shows the state which has irradiated the laser to one chip | tip contained in a wafer. It is a figure and (B) is sectional drawing which follows the AA 'line of (A). (A), (B) is a schematic diagram for demonstrating the laser marking process of a 1st comparative example, Comprising: (A) is a plane which shows the state after irradiating the laser to one chip | tip contained in a wafer. It is a figure and (B) is sectional drawing which follows the AA 'line of (A). (A), (B) is a schematic diagram for demonstrating the laser marking process of a 2nd comparative example, Comprising: (A) is a plane which shows the state after irradiating the laser to one chip | tip contained in a wafer. It is a figure and (B) is sectional drawing which follows the AA 'line of (A). (A)-(C) are typical perspective views for demonstrating the mirror-finishing process process and laser marking process of a 3rd comparative example. (A), (B) is a schematic diagram for explaining the laser marking step of the third comparative example, and (A) irradiates the back surface of one chip included in a mirror-finished wafer with a laser. FIG. 6B is a cross-sectional view taken along the line AA ′ in FIG. (A), (B) is a schematic diagram for demonstrating the laser marking process of a 3rd comparative example, Comprising: (A) irradiated the laser on the back surface of one chip | tip contained in the mirror-finished wafer. It is a top view which shows a back state, (B) is sectional drawing which follows the AA 'line of (A). It is a typical perspective view which shows the structure of the other laser irradiation apparatus used in the laser processing process of the manufacturing method of the semiconductor device of this embodiment.

Hereinafter, a semiconductor device and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 4A and 4B, the semiconductor device according to the present embodiment is formed on the back surface thereof, that is, on the back surface (back surface) 1X of the semiconductor substrate by the polishing marks 4 and the crushed layer 5. A semiconductor chip 1 </ b> A provided with a mark 6. In this semiconductor chip 1A, the polishing marks 4 and the crushed layer 5 in the region other than the portion where the mark 6 on the back surface 1X of the semiconductor substrate is formed are removed.

  Here, the mark 6 is a mark such as a letter, a number, or a symbol. For example, identification data (ID) such as an identification number is provided as a mark 6 on the back surface 1X of the semiconductor substrate. Here, the polishing marks 4 are referred to as back-grind polishing marks because they are generated by back-grind polishing as will be described later. Moreover, the crushing layer 5 is also called a microcrack or a damage layer.

  Thus, the polishing marks 4 and the crushed layer 5 remain only in the mark 6 portion on the back surface 1X of the semiconductor substrate, and the polishing marks 4 and the crushed layer 5 in other regions are removed and flattened (mirrored). Therefore, the mechanical strength of the semiconductor chip 1A can be improved while ensuring the visibility of the mark 6. In particular, since the polishing mark 4 and the crushing layer 5 are left in the region where the polishing mark 4 and the crushing layer 5 are removed and flattened, and the mark 6 is formed by unevenness, the mark having high visibility and Become.

  In the semiconductor device as described above, after polishing the back surface 1X of the semiconductor substrate, as shown in FIGS. 3 and 4, the region other than the part where the mark 6 is formed on the back surface 1X of the semiconductor substrate is irradiated and polished. The mark 4 and the crushing layer 5 are removed, and the mark 6 is formed by the remaining polishing mark 4 and the crushing layer 5. That is, in the manufacturing method of the semiconductor device according to the present embodiment, the laser marking process for forming the mark 6 by irradiating the laser, and the process for removing the polishing mark 4 and the crushed layer 5 by irradiating the laser, At the same time, that is, in the same process.

  Thus, since the process which removes the grinding | polishing trace 4 and the crushing layer 5 is also performed by irradiating a laser using the laser marking method, cost can be suppressed and productivity can be improved. On the other hand, if the process for forming the mark 6 is performed by a method other than the laser marking method, the cost increases. Further, if the process of removing the polishing marks 4 and the crushing layer 5 is performed by another process such as a process using a chemical solution, the cost increases and the productivity decreases. Further, if the process for forming the mark 6 and the process for removing the polishing marks 4 and the crushing layer 5 are performed in different steps, the productivity is lowered.

Thus, by effectively irradiating the back surface 1X of the semiconductor substrate having the polishing marks 4 and the crushing layer 5, the mechanical strength of the semiconductor chip 1A is improved and the mark is formed on the back surface of the semiconductor chip 1A. Both can be realized.
The semiconductor device manufacturing method according to the present embodiment will be specifically described below with reference to FIGS.

First, as shown in FIGS. 1A to 1C, a back grind polishing is performed on a wafer 1 having a circuit formed on the surface through a wafer process in order to make the wafer 1 thinner. This process is called a back grinding process. Note that back grinding is also referred to as mechanical back surface polishing or back surface grinding.
Here, first, as shown in FIGS. 1A and 1B, a surface protection tape 2 is attached to a wafer 1 having a circuit formed on the surface. That is, the surface protection tape 2 is attached so as to cover the circuit formation surface of the wafer 1. Next, as shown in FIG. 1C, the wafer 1 is reversed and mounted on a table (not shown) of a back grinding apparatus, and the grindstone rotates on the back surface of the wafer 1, that is, the back surface 1X of the semiconductor substrate. 3, the back surface 1X of the semiconductor substrate is back-ground and the thickness of the wafer 1 is set to a predetermined thickness. The grindstone 3 is also referred to as a grindstone head for polishing.

By this back grinding process, polishing marks 4 and a crushing layer 5 are formed on the back surface 1X of the wafer 1. Here, the maximum depth of the crushing layer 5 from the top of the convex portion of the polishing mark 4 is about 1 μm.
Next, as shown in FIG. 1D, the wafer 1 is mounted on a table (not shown) of a laser irradiation apparatus, and laser is applied to the back surface 1X of the wafer 1 on which the polishing marks 4 and the crushing layer 5 are formed. Is subjected to laser treatment. This process is called a laser processing process or a laser irradiation process.

  Here, a laser marking process is performed in which the back surface 1X of the wafer 1 on which the polishing marks 4 and the crushing layer 5 are formed is irradiated with a laser to form marks 6 such as letters, numbers, and symbols, and the back surface 1X of the wafer 1 is engraved. The process of removing the polishing marks 4 and the crushed layer 5 is performed simultaneously. That is, the laser processing includes laser marking processing and processing for removing the polishing marks 4 and the crushing layer 5. For this reason, a laser processing process is a laser marking process, and is also a grinding | polishing trace and a crushing layer removal process.

  In particular, in this embodiment, as shown in FIGS. 3 and 4, a region other than the portion where the mark 6 is formed on the back surface 1 </ b> X of the wafer 1 is irradiated with a laser to remove the polishing marks 4 and the crushed layer 5, and the remaining A mark 6 is formed by the polished marks 4 and the crushed layer 5. In this case, in the laser processing step, a region where laser processing is performed, that is, a region where laser irradiation is performed is a region other than a portion where the mark 6 is formed. Here, as described later, since the wafer 1 is divided into a plurality of chips 1A, the mark 6 is formed on the back surface 1X of the wafer 1, that is, the back surface 1X of each chip 1A included in the wafer 1. Further, as shown in FIG. 5, the mark 6 is preferably formed in a central area A (area surrounded by a broken line in FIG. 5) excluding the outer peripheral area of the back surface 1X of each chip 1A. That is, it is preferable that the central area A excluding the outer peripheral area of the back surface 1X of each chip 1A be an area (mark area) where the mark 6 is formed. For example, the area where the mark 6 is formed, that is, the area where the polishing mark 4 and the crushing layer 5 are left, is preferably an area of about 70% of the chip size. That is, when the chip size is horizontal X and vertical Y, it is preferable that the area where the mark 6 is formed is a horizontal 0.7 X and vertical 0.7 Y area. In this case, since the mark 6 is not formed in the outer peripheral region of the back surface 1X of each chip 1A, that is, the polishing marks 4 and the crushed layer 5 in the outer peripheral region of the back surface 1X of each chip 1A are removed and mirror-finished. , Cracks and the like can be prevented, and the mechanical strength of the chip 1A can be prevented from being lowered.

  Further, in the process of removing the polishing marks 4 and the crushing layer 5, the polishing marks 4 and the crushing layer 5 are removed, and the surface without damage is exposed, flattened, and mirror-finished. It is also referred to as flattening processing or mirror surface processing. For this reason, a grinding | polishing trace and a crushing layer removal process are also called a surface treatment process, a planarization process process, or a mirror surface treatment process. Further, since the polishing marks 4 and the crushing layer 5 in the region other than the portion where the mark 6 on the back surface 1X of the semiconductor substrate is formed are melted and removed by laser irradiation, the polishing marks 4 and the crushing layer 5 are removed. The region thus formed is a region where the polishing marks 4 and the crushed layer 5 are melted (laser melted) by laser irradiation. On the other hand, the polishing marks 4 and the crushed layer 5 left without being melted by the laser irradiation become the marks 6.

  In this laser processing step, for example, a laser irradiation device 7 as shown in FIG. 6 may be used to irradiate the back surface 1X of the wafer 1 on which the polishing marks 4 and the fractured layer 5 are formed with a laser. In the present embodiment, the laser irradiation device 7 has a mechanism for scanning the laser spot LS, and can irradiate a desired portion of the back surface 1X of the wafer 1 with a laser. The laser irradiation device 7 is also referred to as a laser irradiation machine.

  Here, it is preferable to set the laser irradiation conditions so that the polishing marks 4 and the crushed layer 5 are removed while the back surface 1X of the wafer 1 is not engraved. For example, the laser wavelength is, for example, about 100 nm to about 1200 nm, the laser pulse width is, for example, about 100 fs to about 200 μs, the spot diameter φ of the laser spot LS is, for example, about 5 to about 100 μm, and the laser spots LS overlap each other. Irradiation is preferred.

  The laser irradiation device 7 including such a scanning mechanism includes a laser oscillator (laser generation device) 8, a shutter 9, an X-direction galvanometer mirror 10, a Y-direction galvanometer mirror 11, and a lens 12. Then, the laser (laser light) emitted from the laser oscillator 8 passes through the shutter 9, is reflected by the X direction galvano mirror 10 and the Y direction galvano mirror 11, passes through the lens 12, and is reflected on the back surface 1 </ b> X of the wafer 1. It comes to be irradiated.

  In particular, in the laser irradiation apparatus 7 of this embodiment, the X-direction galvanometer mirror 10 that scans the laser spot LS in the X direction on the back surface 1X of the wafer 1 and the laser spot LS in the Y direction on the back surface 1X of the wafer 1 are scanned. The laser irradiation position on the back surface 1X of the wafer 1 can be controlled using the Y-direction galvanometer mirror 11 to be operated. Here, the laser spot LS can be scanned in the X direction and the Y direction on the back surface 1X of the wafer 1 by independently rotating the X direction galvanometer mirror 10 and the Y direction galvanometer mirror 11. .

Further, in the present laser irradiation device 7, the presence or absence of laser irradiation on the back surface 1 </ b> X of the wafer 1 can be controlled by opening and closing the shutter 9.
Then, by using the laser irradiation apparatus 7 having such a configuration, as shown in FIG. 7, the portion where the mark 6 on the back surface 1X of the wafer 1 is not irradiated with the laser, but the portion where the mark 6 is formed The laser spot LS is scanned so that the region is irradiated with laser. Thereby, the mark 6 is formed without irradiating the portion where the mark 6 (character mark “F” in this case) on the back surface 1X of the wafer 1 is formed, that is, the portion where the polishing mark 4 and the crushed layer 5 are left. A region other than the portion can be irradiated with a laser. In FIG. 7, a solid arrow indicates that the laser is irradiated, and a broken arrow indicates that the laser is not irradiated.

  In this way, the laser irradiation apparatus 7 that scans the laser spot LS and irradiates the laser does not need a mask. However, since the processing time is longer than that using a mask, a small quantity of various types of chips are manufactured. Suitable for In addition, since only non-defective chips can be selected and irradiated with laser, after dicing, it is possible to select good / bad only by looking at the back surface of the chip 1A.

  Here, the case where the X-direction galvanometer mirror 10 and the Y-direction galvanometer mirror 11 are used as the scanning mechanism is described as an example. However, the present invention is not limited to this, and for example, in the X direction and the Y direction. An XY table to be scanned may be used. As the scanning mechanism, an X-direction galvanometer mirror and a Y-direction table that scans in the Y direction may be used, or a Y-direction galvanometer mirror and an X-direction table that scans in the X direction may be used. .

  On the other hand, as shown in FIGS. 8 to 10, a portion of the back surface 1 </ b> X of the wafer 1 where the mark 6 </ b> X is formed is irradiated with laser to remove the polishing marks 4 and the crushed layer 5, and polishing marks are left in other areas. If the mark 6X is formed while leaving 4 and the crushing layer 5, the polishing marks 4 and the crushing layer 5 remain in most of the back surface 1X of the substrate, so that the mechanical strength of the chip 1A is lowered. In addition, what is shown in FIGS. 8-10 is called a 1st comparative example.

Further, as shown in FIG. 11, not only removing the polishing marks 4 and the crushed layer 5 but also changing the laser irradiation condition to engrave the back surface 1X of the wafer 1 to form the mark 6Y as a recess, the substrate cracks. Or a new crushing layer 5 is formed, and the mechanical strength of the chip 1A is lowered.
Also, as shown in FIG. 12, a mirroring process for mirroring the back surface 1X of the wafer 1 between the back grinding process [see FIG. 12A] and the laser marking process [see FIG. 12C]. It is conceivable to insert [see FIG. The mirror finishing process is a stress relief process such as a polishing process using a grindstone 13 or an etching process using a chemical. In this case, as shown in FIGS. 13 and 14, the back surface 1X of the mirror-finished wafer 1 is irradiated with laser, and the back surface 1X of the wafer 1 is engraved to form a mark 6Z as a recess. However, since the substrate is cracked or a new crushed layer 5 is formed, the mechanical strength of the chip 1A is lowered. Further, the polishing process 4 for removing the polishing marks 4 and the crushing layer 5 generated in the back grinding process to make a mirror surface and the laser marking process become separate processes, so the productivity is lowered. Furthermore, in the mirror finishing process, for example, if a process using a chemical solution is performed, the cost increases. In addition, since the back surface 1X of the mirror-finished wafer 1 is not uneven, there is no marking method other than engraving the wafer 1.

  Next, as shown in FIG. 2A, a frame ring 14 is placed on the outer periphery of the wafer 1 and a dicing tape 15 is attached to the back surface 1X and the frame ring 14 of the wafer 1 to fix the wafer 1 to the frame ring 14. Then, as shown in FIG. 2B, these are reversed and mounted on a table (not shown) of the dicing apparatus, and the surface protection tape 2 is peeled off. This process is called a mounting process, a surface protective tape peeling process, and a surface protective tape peeling / mounting process.

Next, as shown in FIG. 2C, the wafer 1 is diced by a dicing blade 16. Thereby, the wafer 1 is separated into a plurality of chips 1A. This process is called a dicing process.
As shown in FIG. 2D, the plurality of separated chips 1A are conveyed to the mounting apparatus (die mounting apparatus) while being held by the frame ring 14 and the dicing tape 15, and are mounted on the mounting apparatus. To pick up each chip 1A. This process is called a chip pickup process. Then, each picked up chip 1A is transported to the mounting board and mounted on the mounting board. This process is called a chip mounting process.

Therefore, according to the semiconductor device and the manufacturing method thereof according to the present embodiment, there is an advantage that the mark 6 can be formed on the back surface while improving the mechanical strength.
Note that the present invention is not limited to the configurations described in the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the laser irradiation device 7 that scans the laser spot LS is used in the laser processing step. However, the present invention is not limited to this. For example, as shown in FIG. 15, a laser irradiation apparatus 7X that irradiates a laser using a mask 22 may be used. In this case, the laser irradiation device 7X includes a laser oscillator (laser generation device) 20, a mirror 21, a mask 22, and a lens 23. The laser emitted from the laser oscillator 20 is reflected by the mirror 21 and is masked. The back surface 1X of the wafer 1 may be irradiated through the lens 22 and the lens 23. In this case, since the laser is irradiated to the back surface 1X of the wafer 1 through the mask 22, the mark 6A formed on the mask 22 is transferred as the mark 6 to the back surface 1X of the wafer 1.

Here, the mask 22 is configured such that the mark 6A blocks the laser and the other regions allow the laser to pass. That is, in the mask 22, the mark 6A is a light shielding region, and the other region is a transmission region.
Then, using the laser irradiation apparatus 7X having such a configuration, the laser is irradiated to the region other than the portion where the mark 6 is formed without irradiating the portion where the mark 6 is formed on the back surface 1X of the wafer 1. As shown, the laser is irradiated through the mask 22. Thereby, the laser is irradiated to the area other than the part where the mark 6 is formed without irradiating the part where the mark 6 on the back surface 1X of the wafer 1 is formed, that is, the part where the polishing mark 4 and the crushing layer 5 are left. Can do.

Thus, in the laser irradiation apparatus 7X that irradiates the laser using the mask 22, the mask 22 is necessary. However, since the back surface 1X of the wafer 1 can be irradiated in a lump, the processing time is shortened. be able to.
In the above-described embodiment, the laser processing step is performed before the dicing step. However, the present invention is not limited to this. For example, a laser processing step may be performed after the dicing step. That is, the laser processing step may be performed after the dicing step and before the chip pickup step. In this case, a process of irradiating a laser to a plurality of chips 1A obtained by dividing a single wafer 1 into wafers is performed. Further, after the chip pick-up process, the laser processing process may be performed in the middle of transporting each chip 1A to the mounting substrate. In this case, a process of irradiating a laser to each chip, that is, each chip 1A is performed.

DESCRIPTION OF SYMBOLS 1 Wafer 1A Semiconductor chip 1X The back surface of a semiconductor substrate, the back surface of a wafer, the back surface of a chip 2 Surface protection tape 3 Grinding stone 4 Polishing mark 5 Shatter layer 6, 6A, 6X, 6Y, 6Z Mark 7, 7X Laser irradiation apparatus 8 Laser oscillator 9 Shutter 10 X direction galvanometer mirror 11 Y direction galvanometer mirror 12 Lens 13 Grinding wheel 14 Frame ring 15 Dicing tape 16 Dicing blade 20 Laser oscillator 21 Mirror 22 Mask 23 Lens A Central area (mark area)
LS laser spot

Claims (4)

Provided with marks formed by polishing marks and crushed layers on the backside of the semiconductor substrate,
A semiconductor device, wherein a polishing mark and a crushed layer in a region other than a portion where the mark is formed on the back surface of the semiconductor substrate are removed. Polish the backside of the semiconductor substrate,
A semiconductor device characterized in that a region other than a portion for forming a mark on the back surface of the semiconductor substrate is irradiated with a laser to remove a polishing mark and a crushed layer, and a mark is formed by the remaining polishing mark and a crushed layer. Production method.   The laser spot is scanned so that the laser is irradiated to a region other than the portion where the mark is formed without irradiating the portion where the mark on the back surface of the semiconductor substrate is formed with the laser. A method for manufacturing a semiconductor device according to claim 2.   Irradiating the laser through a mask so that the laser is irradiated to a region other than the portion where the mark is formed without irradiating the portion where the mark is formed on the back surface of the semiconductor substrate. The method for manufacturing a semiconductor device according to claim 2, wherein the method is characterized in that:

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