JP2013251456A - Semiconductor device manufacturing method and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method and a semiconductor device, which can improve productivity without reduction in quality.SOLUTION: A present semiconductor device manufacturing method comprises: a modified region formation process of irradiating laser beams L in a thickness direction of a semiconductor substrate 10 by fixing a focal point P of the laser beams L at any one point inside the semiconductor substrate 10 to successively grow a modified region K; an etching process of removing the reformed region K only by etching the semiconductor substrate 10 which has been subjected to the modified layer formation process from one surface 10a side to form a through hole 14 or a recess 16 in the semiconductor substrate 10 thereby to manufacture the semiconductor device.

Description

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

  2. Description of the Related Art Conventionally, a semiconductor device is manufactured by forming a through hole, a recess, or the like in a semiconductor substrate. For example, as a method of processing a semiconductor substrate, a method of processing by plasma etching using a reactive gas is widely known. In recent years, a technique for processing a semiconductor substrate using a laser beam is being developed from the merits that a mask is not required and the processing time is relatively short.

Patent Document 1, by irradiating a laser beam to the sacrificial layer of the SOI substrate (10) (12) (SiO _2), after the sacrificial layer (12) made porous, the etching medium from the opening (15) , And a technique for removing the porous sacrificial layer (12) (modified region) by etching is disclosed. In Patent Document 1, when the sacrificial layer (12) is thicker than the spot diameter of the laser beam, the thickness of the sacrificial layer (12) is moved by moving the laser beam spot in the thickness direction of the sacrificial layer (12). Laser light is irradiated in the entire length direction.

JP 2010-164394 A

  By the way, when forming a through-hole and a recessed part in a semiconductor substrate, it is desirable to make the surface roughness of the processing surface (side wall surface in which the through-hole or the recessed part was formed) as small as possible (to make it smoother). For example, when a thin film is to be formed in a through hole or in a recess, the surface roughness may affect the characteristics (for example, conductivity) of the thin film.

  However, as in Patent Document 1, when the laser beam spot (condensing point) is irradiated while moving in the thickness direction of the sacrificial layer (12), the modified region tends to be discontinuous. Due to the influence of the discontinuous modified region, it was difficult to reduce the surface roughness of the processed surface. In addition, when the laser beam is focused on the surface of the semiconductor substrate, the surface of the semiconductor substrate is melted, debris and fumes are generated, and the quality of the semiconductor device is degraded.

  SUMMARY An advantage of some aspects of the invention is to provide a semiconductor device manufacturing method and a semiconductor device capable of improving productivity without degrading quality.

As a result of intensive research conducted by the present inventors, when a condensing point is fixed to an arbitrary point inside the semiconductor substrate and laser light irradiation is continued, the modified region emits the laser light from the condensing point as a starting point. It has been found that it grows toward the side (the reformed area widens).
That is, in the method for manufacturing a semiconductor device according to the present invention, a condensing point is fixed to an arbitrary point inside the semiconductor substrate, and laser light is directed in the thickness direction of the semiconductor substrate from one surface side of the semiconductor substrate. Irradiating and etching a modified region forming step of continuously growing a modified region in the thickness direction starting from the condensing point and the semiconductor substrate that has undergone the modified region forming step from the one surface side And removing the modified region to form a through hole or a recess in the semiconductor substrate.

  In the method for manufacturing a semiconductor device according to the present invention, a laser beam condensing point is fixed to an arbitrary point inside the semiconductor substrate and irradiated in the thickness direction of the semiconductor substrate, and the modified region in the thickness direction. I try to grow continuously. In this way, by continuously growing the modified region, the processed surface of the through hole and the recess obtained after etching can be made smoother. And since the condensing point is fixed inside the semiconductor substrate and the laser beam is irradiated, the energy density of the laser beam on the surface of the semiconductor substrate can be lowered, the generation of debris and fumes on the surface of the semiconductor substrate can be suppressed, and the semiconductor The quality of the apparatus can be improved. Further, since it is not necessary to form a plurality of modified regions by moving the condensing point of the laser light in the thickness direction of the semiconductor substrate, the processing time can be shortened and the productivity can be improved.

FIG. 1 is an explanatory diagram of a laser light irradiation apparatus that irradiates a semiconductor substrate with laser light. FIG. 2 is a view for explaining a modified region forming step in the method for manufacturing a semiconductor device according to the first embodiment, and FIG. 2 (A) shows a state in which laser light is irradiated on one side of the semiconductor substrate. FIG. 2B is an explanatory cross-sectional view illustrating a state in which the modified region is continuously grown inside the semiconductor substrate. FIG. 3 is a diagram illustrating an etching process in the method for manufacturing a semiconductor device according to the first embodiment, and FIG. 3A is a cross-sectional explanatory diagram illustrating a state in which a semiconductor substrate is immersed in an etching medium. FIG. 3B is an explanatory cross-sectional view illustrating a state in which a through hole is formed in the semiconductor substrate. FIG. 4 is a cross-sectional explanatory view for explaining a state in which the through hole is formed in the (110) plane silicon single crystal substrate in the semiconductor device according to the first embodiment. FIG. 5 is an explanatory view showing a semiconductor device according to a modification of the first embodiment, and shows a state in which a recess is formed in the semiconductor substrate.

[First Embodiment]
A method for manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings.
In the present invention, after the condensing point P is fixed to an arbitrary point inside the semiconductor substrate 10 and the modified region K is formed by irradiating the laser beam L from the one surface 10a side of the semiconductor substrate 10, By removing the modified region K by etching, the through holes 14 or the recesses 16 are formed.

First, the semiconductor substrate 10 used in the present invention will be described.
As the semiconductor substrate 10, for example, a silicon single crystal substrate having a (100) plane as a substrate surface (crystal plane orientation) configured in a thin disk shape (that is, a wafer shape) can be used. The semiconductor substrate 10 may have a thickness of about 100 μm, for example. The semiconductor substrate 10 is formed with an element (not shown) formed through a diffusion process or the like.

Next, the laser beam irradiation apparatus 30 that irradiates the laser beam L will be described with reference to FIG.
As shown in FIG. 1, the laser beam irradiation device 30 includes a laser light source 32, a beam expander 34, a beam splitter 36, a galvano scanner 38, a condenser lens 40, and a power meter 42. ing.

  As the laser light source 32, for example, a YAG laser having an oscillation wavelength of 1064 nm and an oscillation frequency of 100 kHz can be used. The wavelength of the laser light is preferably about 1000 to 1100 nm. This is because when the wavelength is shorter than 1000 nm, it is absorbed not on the inside of the semiconductor substrate 10 but on the surface side, and when it exceeds 1100 nm, it is difficult to be absorbed by the semiconductor substrate 10. The laser beam L can be irradiated with a nanosecond pulse of 50 ns, for example.

  The beam expander 34 is for expanding the diameter of the laser light L from the laser light source 32 and making the laser light L parallel light. Further, the beam splitter 36 splits a part of the beams for measurement and makes them enter the power meter 42 side, and makes the remaining beams enter the condenser lens 40 side via the galvano scanner 38.

  The galvano scanner 38 includes a pair of galvanometer mirrors 39 (only one galvanometer mirror 39 is shown in FIG. 1 for convenience of explanation), and the irradiation position of the laser beam L is determined by the galvanometer mirror 39 in the processing area. It can be moved to any position.

  The condensing lens 40 is configured to make the laser light L emitted from the laser light source 32 and reflected by the galvano mirror 39 incident and condensed. In the present invention, the condensing point P of the condensing lens 40 is fixed to an arbitrary point inside the semiconductor substrate 10 and the focusing point P is continuously focused. In particular, the condensing point P is preferably fixed at a position near the other surface 10b opposite to the one surface 10a inside the semiconductor substrate 10. Specifically, when the thickness α of the semiconductor substrate 10 is about 100 μm, the depth β from the one surface 10a is fixed at a position where the depth β is about 90 μm (that is, the depth from the other surface 10b is about 10 μm). It is good to be done.

  Here, the energy density of the laser beam L is inversely proportional to the square of the spot diameter. In the present embodiment, the laser beam L is collected by the condenser lens 40 at an angle of, for example, about 42 degrees. That is, by using the condensing lens 40 having a relatively large condensing angle, for example, the spot diameter of the laser light L on the one surface 10a of the semiconductor substrate 10 is relatively smaller than the spot diameter at the condensing point. The energy density on the one surface 10a (surface) of the semiconductor substrate 10 can be made relatively small, and the occurrence of debris and fumes on the substrate surface can be suppressed.

The energy density of the laser light L on the substrate surface is preferably 5 × 10 ⁸ (W / cm ² ) or less, and more preferably about 3 × 10 ⁸ (W / cm ² ). Further, the energy density of the laser light L at the condensing point P is preferably 5 × 10 ⁹ (W / cm ² ) or more, and more preferably about 1 × 10 ¹⁰ (W / cm ² ). Due to the difference in energy density, the modified region K can be reliably formed inside the substrate without causing any processing on the substrate surface.

  Next, the process of forming the through hole in the semiconductor substrate will be described with reference to FIGS. In addition, in FIG. 2, the laser beam irradiation apparatus 30 is simplified and shown. In the present embodiment, a modified region forming process for continuously growing the modified region K inside the semiconductor substrate and an etching process for removing the modified region K by etching will be mainly described. Further, a case where a silicon single crystal substrate having a substrate thickness α of 100 μm and a substrate surface (crystal plane orientation) of (100) plane is used as the semiconductor substrate 10 will be described as an example.

(Modified region forming process)
First, the modified region forming process will be described.
In the modified region forming step, first, as shown in FIG. 2A, the depth β from the one surface 10a of the semiconductor substrate 10 placed on the stage 50 is 90 μm (that is, the depth from the other surface 10b). Is irradiated with near infrared light having a wavelength of 1064 nm as a laser beam at a position of 10 μm with a 50 ns nanosecond pulse of 100 kHz without moving the condensing point P.

As described above, when the condensing point P is fixed to an arbitrary point inside the semiconductor substrate 10 and irradiation with the laser light L is continued, the modified region K emits the laser light from the condensing point P as a starting point. It grows toward the side (to the one surface 10a side) (FIG. 2B). In addition, the modified region K is formed on the back surface (the other surface 10b) directly below the condensing point P by several μm due to thermal influence. The modified region K may be formed so as to reach the back surface of the substrate. At this time, the spot diameter of the laser beam at the condensing point P is adjusted by the condenser lens so that the spot diameter on the substrate surface side (one surface 10a side) is about 30 μm. ing. The energy density of the laser light L at the condensing point P is about 1 × 10 ¹⁰ (W / cm ² ), and the energy density on the substrate surface side is about 1 × 10 ⁷ (W / cm ² ). In this way, by continuously irradiating with the laser beam condensing point P fixed to an arbitrary point inside the semiconductor substrate 10, as shown in FIG. A modified region K having a shape can be obtained.

(Etching process)
Next, the etching process will be described.
The modified region K formed by irradiating the laser beam as described above is solidified after being melted once due to optical damage and changed to polycrystalline silicon or amorphous silicon, and the bonding of the crystal becomes weak. Therefore, it is easier to etch than a single crystal portion. In the etching process of this embodiment, this property is utilized, and the through hole 14 is formed only by etching the modified portion of the semiconductor substrate 10 formed by the modified region forming process. Specifically, etching is performed starting from the modified region K to form the through hole 14. In this etching step, for example, the through hole 14 having a diameter of 20 μm can be formed (FIG. 3B) by immersing the semiconductor substrate 10 in KOH 48 wt% at 80 degrees for 10 minutes (FIG. 3A). .

  Note that the diameter of the through hole 14 can be controlled by changing the etching time, and the diameter of the through hole 14 can be increased by increasing the etching time. . The shape of the through hole 14 can also be controlled by the crystal plane orientation of the semiconductor substrate 10. For example, by using a silicon single crystal substrate having a substrate surface (crystal plane orientation) of (110) as the semiconductor substrate 10, the side wall 14a of the through hole 14 can be formed more perpendicular to the substrate surface ( FIG. 4). For example, a through-hole 14 having a diameter of 10 μm and a depth of 100 μm can be formed by using a (110) plane silicon single crystal substrate as the semiconductor substrate 10 and immersing in KOH 48 wt% (etching medium) at 80 degrees for 25 minutes. it can.

  The semiconductor device 1 can be manufactured by depositing a metal film such as an aluminum film in the through hole 14 thus obtained by a method such as sputtering to form a through electrode (not shown).

  As described above, according to the method for manufacturing the semiconductor device 1 according to the first embodiment, the condensing point P of the laser light L is fixed to any one point inside the semiconductor substrate 10, and the semiconductor substrate 10. The modified region K is continuously grown in the thickness direction by irradiation in the thickness direction. In this way, by continuously growing the modified region K, the processed surface of the through hole 14 obtained after etching can be made smoother. And since the condensing point P is fixed inside the semiconductor substrate 10 and the laser beam L is irradiated, the energy density of the laser beam L on the surface of the semiconductor substrate can be lowered, and debris and fumes are generated on the surface of the semiconductor substrate. The quality of the semiconductor device 1 can be improved. Moreover, since it is not necessary to form the plurality of modified regions K by moving the condensing point P of the laser light L in the thickness direction of the semiconductor substrate 10, the processing time can be shortened and the productivity can be improved.

  Further, the condensing point P is fixed to a position near the other surface 10b opposite to the one surface 10a inside the semiconductor substrate 10. Thus, by fixing the condensing point P, the modified region K can be more efficiently grown in the thickness direction of the semiconductor substrate 10.

  The etching process is performed using wet etching. Since wet etching does not require a large-scale apparatus and etching can be performed with a relatively inexpensive etching solution, manufacturing costs can be reduced.

  The semiconductor substrate 10 is mainly composed of silicon. Thus, the versatility of this manufacturing method can be further enhanced by using the semiconductor substrate 10 mainly composed of silicon widely used in the field of semiconductor devices.

  Further, the semiconductor device 1 manufactured by the manufacturing method of the first embodiment can exhibit the same effects as the effects described above.

  Next, a semiconductor device 101 according to a modification of the first embodiment of the present invention will be described with reference to FIG. The modification in the first embodiment is mainly different from the semiconductor device 1 described in the first embodiment in that a membrane-shaped recess 16 is formed in the semiconductor substrate 10 instead of the through hole 14. Therefore, substantially the same components as those of the semiconductor device 1 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In this modification, the membrane-shaped recess 16 shown in FIG. 5 is formed by processing the semiconductor substrate using conditions different from the conditions for forming the modified region K and the etching conditions of the first embodiment described above. Can do. Next, a process for forming the recess 16 will be described.

  In this modification, for example, a p-type silicon substrate in which an n-type semiconductor of 3 μm is formed on the other surface 10b is used as the semiconductor substrate 10, and the depth β from one surface 10a of the semiconductor substrate 10 is 80 μm (that is, the other surface). The focal point P is fixed at a position at a depth of 20 μm from 10b, and near infrared light having a wavelength of 1064 nm is irradiated as a laser beam with 10,000 pulses at a 50 ns nanosecond pulse of 100 kHz. To the surface of the substrate immediately above the condensing point P and the vicinity of the back surface of the substrate immediately below the condensing point P (to the extent that it does not reach the back surface of the substrate) (not shown). Note that the spot diameter and the energy density of the laser beam L are adjusted to be approximately the same as those in the first embodiment.

  Then, the semiconductor substrate 10 with the modified region K thus formed is immersed in KOH 32 wt% (etching medium) at 80 degrees for 30 minutes while applying a voltage of 5 V, so that the diameter is 100 μm and the depth is 100 μm. A recess 16 can be formed (FIG. 5). That is, the recess 16 can be formed by advancing the etching to some extent under a predetermined condition and stopping the etching in the depth direction in the vicinity of the pn interface. Further, the shape of the recess 16 can be controlled by changing the etching time as in the case of the through hole 14.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  In the above-described embodiment, the example in which the semiconductor substrate 10 is mainly composed of silicon has been shown. However, the present invention is not limited to this. For example, the semiconductor substrate 10 may be composed mainly of a compound semiconductor such as SiC, GaN, or GaAs.

  In the above embodiment, the case where wet etching is used in the etching process is illustrated, but the present invention is not limited to this, and dry etching can also be used. By using dry etching in the etching process, the time required for etching can be further shortened.

DESCRIPTION OF SYMBOLS 1, 101 ... Semiconductor device 10 ... Semiconductor substrate 10a ... One side 10b ... The other side 14 ... Through-hole 14a ... Side wall 16 ... Recess 30 ... Laser beam irradiation device 32 ... Laser light source 34 ... Beam expander 36 ... Beam splitter 38 ... Galvano Scanner 40 ... Condensing lens 42 ... Power meter 50 ... Stage 60 ... Etching medium K ... Modified region L ... Laser beam P ... Condensing point

Claims (6)

A condensing point (P) is fixed to an arbitrary point inside the semiconductor substrate (10), and laser light (L) is transmitted from one surface (10a) side of the semiconductor substrate (10) to the semiconductor substrate (10). A modified region forming step of continuously growing the modified region (K) in the thickness direction starting from the light condensing point (P),
The modified region (K) is removed only by etching the semiconductor substrate (10) that has undergone the modified region forming step from the one surface (10a) side, and through holes (14) are formed in the semiconductor substrate (10). ) Or an etching step for forming a recess (16);
A method for manufacturing a semiconductor device (1, 101), comprising:   The said condensing point (P) is fixed to the position close | similar to the other surface (10b) on the opposite side to the said one surface (10a) inside the said semiconductor substrate (10). A manufacturing method of the semiconductor device (1, 101) described.   The method of manufacturing a semiconductor device (1, 101) according to claim 1 or 2, wherein the etching step is performed using wet etching.     The method of manufacturing a semiconductor device (1, 101) according to claim 1 or 2, wherein the etching step is performed using dry etching.   The method for manufacturing a semiconductor device (1, 101) according to any one of claims 1 to 4, wherein the semiconductor substrate (10) is mainly composed of silicon.   A semiconductor device (1, 101) manufactured by the method for manufacturing a semiconductor device (1, 101) according to any one of claims 1 to 5.

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