KR20030090432A - Method of the consolidation of silica soots by excimer laser system - Google Patents

Abstract

PURPOSE: A method for solidifying silica soot using excimer laser is provided to reduce a time for a solidification process by performing a solidification process using the excimer laser beam. CONSTITUTION: A method for solidifying silica soot using excimer laser includes a scanning process, a heating process, and a projecting process. The scanning process is performed from one end of a layer to the opposite end of the layer by projecting the excimer laser line beam(S201). The heating process is to supply uniformly the heat to a bottom end of the silicon wafer after the scanning process is performed(S202). The projecting process is to project the excimer laser beam to a solidifying part by controlling an excimer laser beam source after the heating process is performed(S203).

Description

Method of solidification of silica soot using excimer laser {METHOD OF THE CONSOLIDATION OF SILICA SOOTS BY EXCIMER LASER SYSTEM}

The present invention relates to a method of solidifying a silica soot using an excimer laser, and more particularly, to a method of solidifying a silica soot using an excimer laser that can shorten the time in the solidification step and remove defects such as crystal phase holes and interfacial bonding defects. It is about.

Recently, due to mass production of planar optical integrated circuits, many applications are expected in the future, such as low cost of optical transmission terminal components, expansion of subscriber networks, and securing network flexibility to accommodate various services.

Integrated optical devices are electro-optical devices such as LiNbO ₃ using electro-optic effects, photoelectric integrated devices used in light-emitting driving using optical materials such as GaAs or InP, and light-receiving modules integrated with light-receiving functions. It can be largely divided into passive optical devices that form, control, and monitor a network by tapping, wavelength control, phase control, polarization control, and the like while dividing or combining optical signals while spatially transferring them.

In particular, the silica optical waveguide of the passive optical device is the same material as the optical fiber, the optical loss is 0.01 ㏈ / ㎝ or less, the optical properties of the material is very excellent, and stable to environmental changes such as temperature, humidity. In addition, mass production, general purpose, and low cost are possible by using an electronic device process, and the waveguide mode is similar to an optical fiber, and thus low loss connection is possible.

In addition, Si electronic circuits can be integrated on silicon substrates, and switching can be made using silicon V-grooves for optical fiber connections and thermo-optic effects, and large thermal conductivity in hydro-packages of semiconductor lasers. Si has the advantage that can be used as a heat sink (heat sink) has been a lot of research as a material of an integrated circuit for optical communication in recent years.

The silica passive optical waveguide device is FHD (Flame Hydrolysis Deposition), CVD (Chemical Vapor Deposition), ion exchange (Ion Exchange), Sol-Gel deposition, AFD (Aerdsol Flame Deposition), sputtering by sputtering, etc.

In the ion exchange method, a waveguide mask is formed on a glass substrate, and Na ions of the glass are exchanged with ions such as Li, K, and Ag in a molten salt bath to form a waveguide.

In addition, the FHD and the CVD method use a silica thin film using silicon as a substrate, and silicon processing methods such as photolithography and reactive ion etching (RIE), which are used for fabricating silicon electronic devices in the fabrication of optical circuits. Are the same in that they are used, but the silica thin film manufacturing method is very different.

The CVD method is mainly developed for application to electronic devices, and the deposition rate is about 0.01 to 0.05 μm / min, which is very low, the contamination of the reaction tube is severe, and the uniformity of the thin film is low. Therefore, plasma enhanced chemical vapor deposition (PAS) has been developed to make silica waveguides. However, due to the high deposition rate and the difference in thermal expansion coefficient between the silicon substrate and the deposited silica layer, the warpage of the wafer is reduced. It appears that the control of the refractive index by doping, such as Ge has a disadvantage compared to FHD.

The FHD method is a silica optical waveguide film manufacturing method developed based on OVD (Outer Vapor Deposition) technology, which has been mainly developed in the optical fiber manufacturing field, and used in a silicon substrate. In the FHD process, SiCl ₄ and GeCl ₄ are hydrolyzed in a steam flame of H ₂ and O ₂ to deposit a fine powder of SiO ₂ on a silicon substrate (melting point 1400 ° C.). The soot of the FHD is a fine particle of about 10 to 100 nm, and in order to make it into a dense transparent homogeneous silica thin film having excellent light transmissivity, the soot deposited on the substrate needs to be densified at a high temperature of 1350 ° C. or higher. .

In addition, the FHD method is known to be an efficient method for manufacturing a silica optical waveguide requiring a thickness of several tens of micrometers with a deposition rate of about 0.5 to 1 micrometer / min. In addition, doping of doping elements such as B, P, and Ge can be easily performed, so that the control of the refractive index according to the doping amount is more accurate than that of the CVD method.

Therefore, recently, a silica waveguide is manufactured using the FHD.

1A to 1E are flowcharts of a silica waveguide manufacturing method using a conventional FHD method. As shown in the drawing, the manufacturing process of the silica passive optical waveguide device by FHD is deposited on the Si substrate 101 in the order of the SiO ₂ layer 102 and the SiO ₂ -GeO ₂ layer 103 (S101). Subsequently, the core layer 104 and the cover layer 105 are deposited on the SiO ₂ -GeO ₂ layer 103, and a densification process is performed (S102).

Next, the core layer 104 of the stacked layer is patterned, and etching is performed (S103). In addition, after the SiO ₂ layer 106 is deposited on the patterned core layer 104, the cover layer 107 is deposited (S104). After the cover layer 107 is deposited, a solidification process is performed again (S105).

The densification process is a process that is always performed after soot deposition of the buffer layer, the core layer, and the cover layer. The porous silica particles formed in each layer are thermally treated at a suitable high temperature to remove small spaces between the silica particles to propagate an optical signal. It is a process of forming a dense film without loss due to scattering or absorption.

The above process is to reduce the surface energy of the silica particles to lower the energy, and the energy provided by the reduction of the interfacial energy according to the growth of the particles provides the energy necessary for the flow of the particles, thereby increasing the density.

However, the high-densification process as described above has a problem that most of the time is consumed in the high-densification process during manufacturing because it takes a lot of time to increase the reaction temperature, cooling time to lower to room temperature after the solidification reaction.

In addition, the densification process has a disadvantage that the deformation of the wafer due to the high temperature is large, the core layer collapses when the cover layer is stacked after the core layer is etched, thereby causing a problem of significantly lowering the production yield. .

The present invention has been made to solve the above problems, and in particular, by performing the solidification process of the silica waveguide manufacturing process by the FHD method using an excimer laser, the time can be shortened, and defects such as crystal phase holes, poor interface bonding, etc. It is an object of the present invention to provide a method for solidifying silica soot using an excimer laser capable of removing the back.

1a to 1e is a flow chart of a silica waveguide manufacturing method using a conventional FHD method.

2 is a view showing a solidification process of silica soot using an excimer laser according to the present invention.

3 illustrates scanning using a line beam of an excimer laser in accordance with the present invention.

In order to achieve the above object, a method of solidifying silica soot using an excimer laser according to the present invention,

A solidification process of manufacturing a silica waveguide by an FHD method, the method comprising: scanning an excimer laser line beam to scan the entirety from one end of the layer to the other;

After the scanning, uniformly supplying heat to the bottom of the silicon wafer;

After the above step, the excimer laser light source is characterized in that it comprises the step of controlling and projecting to the portion to be solidified.

Here, in particular, in the step of controlling and projecting the excimer laser light source to the portion to be solidified, by controlling the density of the light source energy, the temperature transmitted to the silica soot layer is controlled to remove defects of pores and interfacial bonding defects. Has its features.

According to the present invention as described above, it is possible to shorten the time in the solidification step and to eliminate defects such as crystalline pores and poor interfacial bonding.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating a solidification process of silica soot using an excimer laser according to the present invention. As shown in the figure, in the method of solidifying the silica waveguide manufacturing process by the FHD method, the excimer laser line beam is projected to perform a scan from one end of the layer to the other side (S201).

3 is a view illustrating scanning using a line beam of an excimer laser according to the present invention. As shown therein, the line beam of the excimer laser scans the heat transfer of the portion to be scanned uniformly. In addition, since the beam of the excimer laser (ExcimerLaser) uses a multi-beam in a multi-scan mode, the uniformity of crystallinity is required.

After the scanning step (S201), the heat is uniformly supplied to the lower end of the silicon wafer (S202). This is to prevent the deformation of the wafer by minimizing the temperature difference between the silica layer and other layers through which the line beam is transmitted and solidified. It also increases the bonding strength between the silica layer to be solidified and the layer immediately below it.

After the above step, the excimer laser beam is adjusted and projected onto a portion to be solidified (S203). At this time, the light source energy is supplied in consideration of the soot penetration depth of the line beam, in order to prevent damage to the etched core layer and the silicon wafer when the overcladding layer is solidified. In addition, by controlling the excimer laser beam, it is also possible to use a Si wafer thinner than the 1 mm Si wafer used when manufacturing the optical waveguide by the FHD method. In addition, the amount of impurities such as boron and phosphorus added to lower the solidification temperature may be reduced, thereby improving optical characteristics of the optical waveguide itself.

In addition, by controlling the light source energy of the excimer laser, the temperature delivered to the silica soot layer is controlled to remove defects such as pores and poor interfacial bonding. In general, the solidification temperature in the furnace (furnace) is 1100 ~ 1300 ℃. This temperature control can be controlled by adjusting the energy density of the laser. The excimer laser will be less sensitive to the energy density of the laser delivered than when the amorphous silicon is crystallized by annealing, but as the process proceeds in order of solidification of the lower cladding, solidification of the core layer, and solidification of the upper cladding, something to do. In addition, by transferring heat at an appropriate temperature, it is possible to prevent the formation of pores formed during solidification and the formation of impurities at the interface. In addition, the scan speed is controlled to prevent the formation of impurities.

In addition, when performing the solidification process using the excimer laser, the pressure in the chamber is maintained at atmospheric pressure or low vacuum to prevent soot blowing, and controls the formation of impurities formed on the surface of the layer to be solidified. This is because lowering the pressure so that the soot does not fly prevents dust or fine particles from adsorbing on the wafer surface.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the silica soot solidification method using the excimer laser according to the present invention can shorten the time, especially in the solidification step, and can eliminate defects such as crystal phase holes and poor interfacial bonding.

Claims (4)

A solidification process of manufacturing a silica waveguide by an FHD method, the method comprising: scanning an excimer laser line beam to scan the entirety from one end of the layer to the other; After the scanning, uniformly supplying heat to the bottom of the silicon wafer; After the step, the step of controlling the excimer laser light source and the step of solidifying the silica soot using an excimer laser, characterized in that it comprises the step of solidifying. The method of claim 1, In the step of controlling and projecting the excimer laser light source to a portion to be solidified, by controlling the density of the light source energy, the temperature transmitted to the silica soot layer is controlled to remove defects in pore and interfacial bonding failure. Solidification process of silica soot using excimer laser. The method of claim 1, In the step of uniformly supplying heat to the bottom of the silicon wafer, the line beam is transmitted to minimize the temperature difference between the solidified silica layer and another layer to prevent deformation of the wafer, and the bonding force between the solidified silica layer and the layer directly below The solidification process of the silica soot using an excimer laser, characterized in that to increase the. The method of claim 1, When performing the solidification process using the excimer laser, the excimer characterized in that the pressure in the chamber is maintained at atmospheric pressure or low vacuum, thereby preventing soot blowing and controlling the formation of impurities formed on the surface of the layer to be solidified. Solidification process of silica soot using laser.