JP6757953B2 - Surface processing method, structure manufacturing method - Google Patents

Description

The present invention relates to a surface processing method for an object to be processed and a method for producing a structure.

Conventionally, by heating the semiconductor wafer after ion implantation into the entire semiconductor wafer, blistering, that is, a hollow portion is formed inside the semiconductor wafer, and the surface layer portion of the semiconductor wafer is peeled off in layers (registered). A trademark) technique is proposed, for example, in Non-Patent Document 1.

This smart cut (registered trademark) technology is used, for example, in the manufacture of an SOI substrate (Silicon on Insulator; SOI). Specifically, first, a silicon wafer A is prepared, and the entire surface of the silicon wafer A is thermally oxidized to form a SiO ₂ insulating layer. Further, hydrogen ions are ion-implanted into the silicon layer of the silicon wafer A through the SiO ₂ insulating layer.

Next, the surface of the SiO ₂ insulating layer is cleaned with a chemical such as acid and pure water. Further, a silicon wafer B is prepared. Then, each of the silicon wafers A and B is subjected to a hydrophilic treatment, and the SiO ₂ insulating layer is superposed so as to be sandwiched between the silicon layer of the silicon wafer A and the silicon wafer B, and bonded at room temperature.

Subsequently, the laminated wafer is heat-treated at 400 ° C. to 600 ° C. As a result, blistering is generated on the silicon wafer A to break the bonds of the silicon crystals, and the silicon layer having a thickness of several μm is peeled off from the silicon wafer A.

After that, the interface between the silicon wafers A and B is heat-treated at 1000 ° C. or higher. Finally, the surface of the peeled silicon wafer A is polished. In this way, the SOI substrate is completed. The above is the process using the smart cut (registered trademark) technology.

M. Bruel, Electronics Letters, Volume 31, Issue 14, 6 July 1995, p.1201-1202

The above-mentioned conventional technique is a technique for peeling the surface layer portion of the semiconductor wafer as a thin layer, but since ion implantation is performed on the entire silicon wafer A, the entire peeled surface becomes a flat surface. Therefore, it is difficult to form a fine structure such as unevenness on the peeled surface by using the above-mentioned conventional technique.

Here, it is known that when ions are implanted into a semiconductor wafer and the semiconductor wafer is heated, a cavity called "blistering" is generated in the ion-implanted portion. It is possible to form a fine structure on the surface of the semiconductor wafer by causing bulging on the surface of the semiconductor wafer due to this cavity.

However, although the above phenomenon itself is known, the swelling of the surface of the semiconductor wafer due to blistering, that is, the height of the structure is at the nano level and is extremely small. In addition, the current situation is that there is no controllability in the formation of fine structures. Therefore, a method of forming a fine structure by efficiently processing the surface of a semiconductor wafer by utilizing blister ring is desired.

In the above, the semiconductor wafer is described as an example of the processing target, but the material to be processed is not limited to the semiconductor material.

In view of the above points, a first object of the present invention is to provide a surface processing method capable of efficiently processing the surface of an object to be processed by using blister ring. A second object of the present invention is to provide a method for manufacturing a structure using the surface processing method.

In order to achieve the above object, the invention according to claim 1 is a surface processing method for forming a fine structure (260) on the surface (210) of the object to be processed (200), and is characterized by the following points. It is said.

First, an ion implantation step of forming an ion implantation layer (230) on the object to be processed (200) is performed by implanting ions into the object to be processed (200).

After the ion implantation step, the processed object (200) is irradiated with a laser beam, and the irradiated portion of the processed object (200) is locally heated to blister the processed object (200) (200). By generating 250), a laser beam irradiation step is performed on the surface (210) of the object to be processed (200) as a structure (260) to form a raised structure in which a part of the surface (210) is raised . The laser beam irradiation step is characterized in that the structure (260) forms a raised structure on the order of microns having a thickness of 7 μm or less in the thickness direction perpendicular to the surface (210) of the object to be processed (200) .

According to this, the inside of the object to be processed (200) can be locally rapidly and easily heated by implanting ions and irradiating the object to be processed (200) with a laser beam. This makes it possible to improve the size and controllability of the blister ring (250). Therefore, in the invention according to claim 2, in which the surface (210) of the object to be processed (200) can be efficiently processed by using the blister ring (250), the laser light is continuously generated in the laser light irradiation step. The object to be processed (200) is irradiated with an oscillating laser beam. By using the continuously oscillating laser beam, a fine structure (260) can be reliably formed.

Further, the invention according to claim 3 is characterized in that, in the laser light irradiation step, the processed object (200) is irradiated with an infrared laser beam as the laser beam. By using the laser beam of infrared light, a fine structure (260) can be reliably formed.

Further, the invention according to claim 4 is characterized in that, in the laser light irradiation step, the object to be processed (200) is made of a semiconductor material. By using a work object (200) made of a semiconductor material, a fine structure (260) can be reliably formed.

In the above, the surface processing method for forming a fine structure (260) on the object to be processed (200) has been described, but it can also be used as a method for manufacturing a structure for forming a structure (260) on the object to be processed (200). It has similar characteristics and effects.

In addition, the reference numerals in parentheses of each means described in this column and the scope of claims indicate the correspondence with the specific means described in the embodiment described later.

It is a figure which showed the whole structure of the laser light irradiation apparatus used in the laser light irradiation process in one Embodiment of this invention. (A) is a cross-sectional view of the Si wafer after the ion implantation step, and (b) is a cross-sectional view of the Si wafer after the laser beam irradiation step. It is a figure which showed the dislocation of the crystal which occurred on the Si wafer. It is a figure which showed the cavity, the crack, and the dislocation part generated in the Si wafer. It is a top view which observed the surface of the Si wafer by the white light interference type non-contact three-dimensional surface property measuring machine (CCI). It is a perspective view which observed the surface of a Si wafer by CCI. It is sectional drawing of the structure shown in FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The surface processing method and the structure manufacturing method according to the present embodiment are methods for forming a fine structure on the surface of the object to be processed. In the following, an example of forming a fine structure on the surface of a Si wafer made of a semiconductor material as a processing object will be described. The "surface of the Si wafer" includes not only the surface of the Si wafer but also the surface layer portion including the surface.

First, the ion implantation apparatus used in the ion implantation step will be described. Ion implantation devices are well known devices in semiconductor processes. Although detailed description is omitted, the ion implanter generally has a configuration in which an ion beam is irradiated from an ion source, the ion beam is accelerated by an acceleration tube, and the ion beam is driven into the Si wafer 200. In this embodiment, hydrogen ions and helium ions are driven into the Si wafer 200.

Subsequently, the laser light irradiation device used in the laser light irradiation step will be described. As shown in FIG. 1, the laser light irradiation device 100 includes a laser light source 110, a condensing lens 120, and a stage 130.

The laser light source 110 generates laser light on the Si wafer 200. As the laser light source 110, one having a laser light wavelength of, for example, 1064 nm and emitting a continuously oscillating laser light is used. Note that this condition is an example, and the laser light source 110 may be driven under other conditions.

Here, the Si wafer 200 absorbs a part of the laser beam. In other words, the laser beam passes through the Si wafer 200 while a part of the energy is absorbed by the Si wafer 200. That is, in the wavelength range of the above laser beam, the Si wafer 200 is configured to be translucent.

The condensing lens 120 incidents the laser beam emitted from the laser light source 110 and condenses it inside the Si wafer 200. That is, the condensing lens 120 is arranged with respect to the Si wafer 200 so that the focal point 140 of the laser beam is located inside the Si wafer 200.

The condenser lens 120 is packaged together with the laser light source 110. As such, for example, an LD irradiation light source device manufactured by Hamamatsu Photonics Co., Ltd. can be used. On the other hand, since the laser beam irradiation device 100 only needs to be configured to sufficiently heat the vicinity of the surface 210 of the Si wafer 200, the condensing lens 120 is not an essential configuration for the laser beam irradiation device 100. That is, the laser light irradiation device 100 may be set under conditions that allow the vicinity of the surface 210 of the Si wafer 200 to be sufficiently heated by the laser light emitted from the laser light source 110.

The stage 130 has an installation surface 131 on which the Si wafer 200 is placed. The stage 130 is made of a metal plate such as a quartz glass plate or an Al plate. In the present embodiment, the Si wafer 200 is installed on the installation surface 131 of the stage 130 so that the front surface 210 side of the Si wafer 200 is directed toward the condensing lens 120 and the back surface 220 of the Si wafer 200 is in contact with the installation surface 131. To. The above is the configuration of the laser beam irradiation device 100.

Subsequently, a method of forming a structure on the Si wafer 200 using each of the above devices will be described. First, in the ion implantation step, ions are implanted from the surface 210 side of the Si wafer 200 into the inside of the Si wafer 200 from above the surface 210 of the Si wafer 200. As a result, as shown in FIG. 2A, the ion implantation layer 230 is formed on the Si wafer 200.

As specific conditions, when helium ions or hydrogen ions are implanted, the dose amount is 8 × 10 ¹⁶ / cm ² , and the ion energy is 40 keV to ² MeV. Since the ion energy is relatively small under this condition, the ion implantation layer 230 is formed at a depth of about 100 nm to 20 μm from the surface 210 of the Si wafer 200.

After that, a laser beam irradiation step is performed. The irradiation environment of the laser beam does not have to be in a vacuum or a specific gas. The Si wafer 200 is irradiated with a laser beam in the air.

Specifically, the focal point 140 of the laser beam is aligned with the inside of the Si wafer 200, and the laser beam is irradiated from above the surface 210 to the inside to locally heat the irradiated portion of the Si wafer 200 with the laser beam. The diameter of the laser beam applied to the surface 210 of the Si wafer 200 is, for example, about 400 μm.

In this laser light irradiation step, the Si wafer 200 is irradiated with continuously oscillating laser light as the laser light. Further, the Si wafer 200 is irradiated with an infrared laser beam having a wavelength of 915 nm as the laser beam. The irradiation output of the laser beam is, for example, 10 W to 18 W. The irradiation time of the laser beam on the Si wafer 200 is, for example, about several seconds or about ten and several seconds. The Si wafer 200 can be locally heated faster than lamp annealing. Further, since the continuously oscillating laser beam is used, the surface layer portion of the Si wafer 200 can be heated without making a hole in the surface 210 of the Si wafer 200.

As a result, as shown in FIG. 2B, a cavity 240 is formed inside the Si wafer 200, and blistering 250 is generated. The cavity 240 constitutes, for example, an egg-shaped or capsule-shaped space. By forming the blister ring 250, a raised structure in which a part of the surface 210 is raised is formed as a structure 260 on the surface 210 of the Si wafer 200.

3 to 7 show a structure 260 formed by setting the irradiation time of the laser beam to 5 seconds with respect to the crystal plane of the surface 210 of the Si wafer 200 having the (100) plane.

As shown in the TEM image of FIG. 3, a white region is formed inside the Si wafer 200. This white area is the cavity 240. Therefore, the portion of the Si wafer 200 raised by the cavity 240 is the blister ring 250.

A large number of black streaks are formed in the portion of the Si wafer 200 corresponding to the blister ring 250, that is, in the region between the surface 210 and the cavity 240. This black streak indicates that there was a crystal rearrangement. It is considered that the crystal dislocation was caused by the thermal stress caused by heating the Si wafer 200 by the laser beam. Further, the black streaks visible in the lower part of the cavity 240 are considered to be crystal dislocations or bend contours.

The layer located on the surface 210 of the Si wafer 200 is the SiO ₂ layer 270. The layer located above the SiO ₂ layer 270 is the tungsten guard layer 280. These are for pretreatment in Focused Ion Beam Processing (FIB) to allow cross-sectional observation.

FIG. 4 is a TEM diagram having a wider area than that of FIG. As shown in FIG. 4, the circular white portion is the cavity 240. The elongated white portion between the cavities 240 is the crack 241 generated between the cavities 240. Further, a plurality of white dot portions and a plurality of black dot portions located above and below a linear line in which a plurality of cavities 240 are arranged are dislocation portions 242 in which crystal dislocation has occurred. Note that FIG. 4 shows an example of the cavity 240, the crack 241 and the dislocation portion 242.

Then, the portion where a part of the surface 210 of the Si wafer 200 is raised by the blister ring 250 is a fine structure 260. Specifically, as shown in the CCI images of FIGS. 5 to 7, the structure 260 has a structure in which a part of the surface 210 of the Si wafer 200 is raised like a pyramid in a triangular pyramid shape. For the observation, Taylor Hobbson's Talysurf was used as the CCI.

In particular, as shown in the cross-sectional profile of FIG. 7, the structure 260 had a height of about 7 μm and a plane size of about 0.2 mm. This is a very large size as compared with the conventional fine structure of several nm to at most several hundred nm. As described above, the reason why it is possible to form the structure 260 at the micron level larger than the conventional one is that the cavity 240 larger than the conventional one can be formed inside the Si wafer 200 by the irradiation of the laser beam. It is thought that this is because it has become. Since the cavity 240 becomes large, the volume of the portion of the surface layer portion of the Si wafer 200 that is raised by the cavity 240 becomes large. Therefore, it has become possible to form a structure 260 having a size larger than that of the conventional one.

Here, as shown in the plan view of FIG. 5 and the perspective view of FIG. 6, a plurality of recesses are formed on the surface 210 of the Si wafer 200. This recess is a portion where a part of the Si wafer 200 is peeled off by ion implantation and laser light irradiation on the Si wafer 200.

The cavity 240 forming the structure 260, the dislocation portion 242 around the cavity 240, and the fine cracks 241 have a light-shielding effect of blocking light incident on the Si wafer 200 from the outside. Further, since the cavity 240 is filled with gas, heat is not easily transferred and has a heat shielding effect. Due to the light-shielding effect and the heat-shielding effect, the temperature rise effect of the surface layer portion of the Si wafer 200 can be obtained more easily.

As described above, the present embodiment is characterized by a method of irradiating a laser beam after ion implantation into a Si wafer 200, which is a processing target. By this method, a structure 260 having a raised structure in which a part of the surface 210 is raised can be formed on the surface 210 of the Si wafer 200. It is considered that the cause of the formation of the structure 260 is that the irradiated portion is heated to near the melting point by irradiating the Si wafer 200 with the laser beam, the cavity 240 is formed, and the cavity 240 is enlarged. ..

Further, although it is necessary to implant the Si wafer 200 with ions, the structure 260 can be formed in the irradiation range of the laser beam on the surface 210 by irradiating the Si wafer 200 with the laser beam for a predetermined time. The equipment that irradiates the laser beam can be realized with a simple configuration. Therefore, the fine structure 260 can be easily formed on the surface 210 of the Si wafer 200.

In particular, conventionally, the structure 260 could be formed only with a thickness on the order of nanometers, but by the above method, the structure 260 having a thickness about 1000 times, that is, on the order of microns can be formed. More specifically, conventionally, only structures having a size in the plane direction of several μm and a size in the thickness direction of several nm could be formed, but by the above method, the size in the plane direction is several tens of μm. It has become possible to form a structure 260 having a size in the thickness direction on the order of several μm. Further, the size of the structure 260 can be adjusted by adjusting the irradiation time of the laser beam. Furthermore, the controllability of the size of the structure 260 has also been improved.

The above-mentioned method for forming the structure 260 can be applied in various forms as an element method of microfabrication characterized by non-contact, dust-free, and no cutting margin. For example, as an application example of the structure 260, it may be useful for improving the amount of light of a light emitting device, manufacturing a nanoimprint mold, or manufacturing a diffraction grating / scattering target. Further, application to MEMS element parts is also conceivable.

Regarding the correspondence between the description of the present embodiment and the description of the claims, the Si wafer 200 corresponds to the "processed object" in the claims.

(Other embodiments)
The method for forming the structure 260 shown in each of the above embodiments is an example, and the present invention is not limited to the above-described configuration, and other configurations that can realize the present invention can be used. For example, a semiconductor material such as SiC or GaN, or a material capable of ion implantation and laser beam irradiation such as diamond, LiTaO ₃ or LiNbO ₃ may be processed.

Further, the laser beam irradiation in the laser beam irradiation step may be performed by scanning the surface 210 as well as irradiating one place of the object to be processed. When scanning the laser beam, the focal point 140 of the laser beam and the object to be processed may be relatively moved. Therefore, the stage 130 may be moved with the positions of the laser light source 110 and the condensing lens 120 fixed, or the positions of the laser light source 110 and the condensing lens 120 may be moved with the positions of the stage 130 fixed. Is also good.

Further, in the above laser beam irradiation step, the focus 140 of the laser beam is aligned with the inside of the Si wafer 200, and the laser beam is irradiated from above the surface 210 to the inside, which is an example of laser beam irradiation. The focal point 140 of the laser beam does not have to be located inside the Si wafer 200. Therefore, the Si wafer 200 may be irradiated with the laser beam from above the surface 210 without focusing the laser beam 140 on the inside of the Si wafer 200.

110 Laser light source 120 Condensing lens 140 Focus 200 Si wafer (object to be processed)
210 Surface 230 Ion Implanted Layer 250 Blistering 260 Structure

Claims (8)

A surface processing method for forming a fine structure (260) on the surface (210) of the object to be processed (200).
An ion implantation step of forming an ion implantation layer (230) in the processing object (200) by performing ion implantation into the processing object (200).
After the ion implantation step, the processed object (200) is irradiated with a laser beam, and the irradiated portion of the processed object (200) is locally heated to be processed locally (200). ) By generating blister ring (250), a raised structure in which a part of the surface (210) is raised is formed as the structure (260) on the surface (210) of the processed object (200). Laser beam irradiation process and
Only including,
In the laser beam irradiation step, the structure (260) is formed with a micron-order raised structure having a thickness of 7 μm or less in the thickness direction perpendicular to the surface (210) of the object to be processed (200). A characteristic surface processing method. The surface processing method according to claim 1, wherein in the laser light irradiation step, a continuously oscillating laser beam is irradiated to the processing object (200) as the laser light. The surface processing method according to claim 1 or 2, wherein in the laser light irradiation step, the laser light of infrared light is irradiated to the processing object (200) as the laser light. The surface processing method according to any one of claims 1 to 3, wherein in the laser light irradiation step, the object to be processed (200) is made of a semiconductor material. A method for manufacturing a structure that forms a fine structure (260) on the surface (210) of the object to be processed (200).
An ion implantation step of forming an ion implantation layer (230) in the processing object (200) by performing ion implantation into the processing object (200).
After the ion implantation step, the processed object (200) is irradiated with a laser beam, and the irradiated portion of the processed object (200) is locally heated to be processed locally (200). ) By generating blister ring (250), a raised structure in which a part of the surface (210) is raised is formed as the structure (260) on the surface (210) of the processed object (200). Laser beam irradiation process and
Only including,
In the laser beam irradiation step, the structure (260) is formed with a micron-order raised structure having a thickness of 7 μm or less in the thickness direction perpendicular to the surface (210) of the work object (200). A method for manufacturing a characteristic structure. The method for manufacturing a structure according to claim 5, wherein in the laser light irradiation step, the laser light of continuous oscillation is irradiated to the processed object (200) as the laser light. The method for manufacturing a structure according to claim 5 or 6, wherein in the laser light irradiation step, an infrared laser beam is irradiated to the processed object (200) as the laser light. The method for manufacturing a structure according to any one of claims 5 to 7, wherein in the laser light irradiation step, the object to be processed (200) is made of a semiconductor material.