Cooled optical transmission module device and method of manufacturing the same

Provided is a cooled optical transmission module device including a silicon wafer having a plurality of platform mounting grooves, each of which serves as a space for mounting in which an optical transmission platform therein, a thermoelectric cooler bonded to the platform mounting groove to transfer heat to outside, the optical transmission platform provided on the thermoelectric cooler and configured to output an optical signal by generating and reflecting the optical signal, a dielectric sub-mount bonded to the platform mounting groove of the silicon wafer and electrically connected to the mounted optical transmission platform, and a cover configured to cover the platform mounting groove of the silicon wafer and seal the platform mounting groove while providing an electric path.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Applications No. 2019-0134402, filed on Oct. 28, 2019, and No. 2020-0029886, filed on Mar. 10, 2020, the disclosures of which are incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to a cooled optical transmission module device and a method of manufacturing the same, and more particularly, to a cooled optical transmission module device, in which an optical transmission module that requires temperature control is manufactured by assembling photo/optical devices and then finally dicing, and a method of manufacturing the same.

2. Discussion of Related Art

Recently, as data traffic is increasing, an optical transmission/reception module capable of transmitting a large amount of data at a high speed without distortion of signals has been rapidly developing, and price competitiveness through mass production of the optical transmission/reception modules is becoming important.

In a cooled transmitter optical subassembly (TOSA) module of which optical wavelength stabilization is important in the conventional optical network, a package and an optical transmission platform are manufactured through separate manufacturing processes and individual packaging, which is not beneficial in mass production.

SUMMARY OF THE INVENTION

The present invention is directed to solving the existing problems by providing a cooled optical transmission module device that is beneficial in mass production by applying a wafer level packaging process to a manufacturing process of a cooled optical transmission module which prioritizes optical wavelength stabilization in the existing 5G and 6G local network wavelength division (LWDM), dense wavelength division multiplexing (DWDM), and optical networks having optical wavelength bands of 100 GHz and 50 GHz.

The technical objectives of the present invention are not limited to the above, and other objectives may become apparent to those of ordinary skill in the art on the basis of the following description.

According to an aspect of the present invention, there is provided a cooled optical transmission module device including a silicon wafer having a plurality of platform mounting grooves, each of which serves as a space for mounting an optical transmission platform therein, a thermoelectric cooler bonded to the platform mounting groove to transfer heat to outside, the optical transmission platform provided on the thermoelectric cooler and configured to output an optical signal by generating and reflecting the optical signal, a dielectric sub-mount bonded to the platform mounting groove of the silicon wafer and electrically connected to the mounted optical transmission platform, and a cover configured to cover the platform mounting groove of the silicon wafer and seal the platform mounting groove while providing an electric path.

In the silicon wafer, the platform mounting groove may be formed through a wet etching process, and the silicon wafer may include a silicon material having a thermal conductivity of 149 W/(m·k).

The silicon wafer may be coated with a solder material or an epoxy material for bonding the cover around a periphery of an upper portion of the platform mounting groove for a sealing process for an internal airtightness of the platform mounting groove.

The optical transmission platform may include: a photoelectric device configured to output an optical signal to a lens, the lens configured to collimate the optical signal output through the photoelectric device, an optical device configured to reflect the optical signal collimated through the lens at a certain angle, a monitoring photo diode configured to detect light transmitted without being reflected by the optical device, and a temperature detector configured to detect an operating temperature of the photoelectric device.

The cover may be provided with a light transmitting coating film formed on an upper surface and a lower surface of the cover corresponding to a position of the optical signal reflected through the optical device so as to correspond to optical wavelengths of the reflected optical signals.

The dielectric sub-mount may include a first flat portion formed with a metal pattern and disposed at a height equal to a height of the optical transmission platform mounted in the platform mounting groove when the dielectric sub-mount is mounted in the platform mounting groove, a second flat portion formed with a metal pattern to be in electrical contact with the cover while supporting the cover for sealing the platform mounting groove, and an inclined portion formed with a metal pattern and electrically connecting the first flat portion to the second flat portion.

The plurality of metal patterns of the dielectric sub-mount may include a radio frequency (RF) line for connection of a high-speed signal, a power supply line of the thermoelectric cooler, and a low frequency signal line connected to sense a monitoring photo diode and a temperature detector.

The dielectric sub-mount may be formed of a glass material.

The cover may include a sealing pad provided at a periphery of a lower surface of the cover and configured to be in contact with and then seal the platform mounting groove of the silicon wafer, a redistribution layer (RDL) formed at one side of an upper surface of the cover, a metal via path formed to pass through the cover while being connected to the RDL, and a metal pad connected to the metal via path so as to be in contact with the metal pattern of the dielectric sub-mount when the silicon wafer is sealed.

According to another aspect of the present invention, there is provided a method of manufacturing a cooled optical transmission module, the method including generating a silicon wafer formed with a platform mounting groove as a space for mounting an optical transmission platform in the silicon wafer, bonding a thermoelectric cooler to the platform mounting groove of the generated silicon wafer, bonding the optical transmission platform on the thermoelectric cooler bonded to the platform mounting groove, bonding a dielectric sub-mount having a solder bump to the platform mounting groove at a position in which the thermoelectric cooler is not bonded, electrically connecting the optical transmission platform to the dielectric sub-mount, and bonding a cover to the silicon wafer to seal the silicon wafer and electrically connecting the optical transmission platform.

The method may further include checking operating characteristics of the optical transmission module at a wafer level and performing dicing.

The performing of the dicing may use one of laser dicing, saw dicing, and scribing and breaking.

The generating of the silicon wafer may include forming the platform mounting groove through a wet etching process.

The generating of the silicon wafer may further include coating the silicon wafer with a material for bonding the cover around a periphery of an upper portion of the platform mounting groove for a sealing process to maintain an internal airtightness of the platform mounting groove.

The bonding of the cover to the silicon wafer to seal the silicon wafer and electrically connecting the optical transmission platform may include forming a light transmitting coating film on an upper surface and a lower surface of the cover corresponding to a position of an optical signal reflected through an optical device to correspond to optical wavelengths of the reflected optical signal

The above-described configurations and operations of the present invention will become more apparent from embodiments described in detail below with reference to the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Advantages and features of the present invention and methods for achieving them will be made clear from embodiments described in detail below with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the present invention to those of ordinary skill in the technical field to which the present invention pertains. The present invention is defined by the claims. Meanwhile, terms used herein are for the purpose of describing the embodiments and are not intended to limit the present invention. As used herein, the singular forms include the plural forms as well unless the context clearly indicates otherwise. The term “comprise” or “comprising” used herein does not preclude the presence or addition of one or more other elements, steps, operations, and/or devices other than stated elements, steps, operations, and/or devices.

FIG. 1is a cross-sectional view for describing a cooled optical transmission module device according to an embodiment of the present invention.

Referring toFIG. 1, the cooled optical transmission module device according to the embodiment of the present invention includes a silicon wafer100, a thermoelectric cooler200, an optical transmission platform300, a dielectric sub-mount400, and a cover500.

The silicon wafer100as an SI wafer is provided with a plurality of spaces in which an optical transmission platform is mounted. As shown inFIG. 3, the silicon wafer provides a platform mounting groove110, in which the thermoelectric cooler200, the optical transmission platform300, and the dielectric sub-mount400are mounted, through a simple wet etching process. The silicon wafer100is preferably formed of a silicon material having a thermal conductivity of 149 W/(m·k). Accordingly, the thermoelectric cooler200is beneficial in heat dissipation.

In addition, the silicon wafer100may be coated with a solder material or epoxy material, which is an adhesive material120for bonding the cover500having an interposer, on a periphery of an upper side of the platform mounting groove110for a sealing process for maintaining the internal airtightness of the platform mounting groove110.

The thermoelectric cooler200is inserted into the platform mounting groove110and operates in response to heat generated from the optical transmission platform300to transfer heat from the optical transmission platform300to the outside. The thermoelectric cooler200may be provided using a thermoelectric cooling device employing the Peltier effect that heat is absorbed when a current flows through a heterojunction of two metals, but the thermoelectric cooler is not limited thereto and various thermoelectric devices may be used without limitation.

The optical transmission platform300is provided on the thermoelectric cooler200and includes a photoelectric device310that outputs an optical signal, a lens320that determines an irradiation position of the optical signal output through the photoelectric device310, an optical device (a mirror)330that reflects the optical signal transmitted from the photoelectric device310through the lens320, a monitoring photodiode340that detects an optical signal, which passes through the optical device330without being reflected by the optical device330, among the optical signals output from the photoelectric device310, and a temperature measurer350for measuring the temperature of the photoelectric device310.

The photoelectric device310outputs an optical signal to the lens320.

The lens320collimates optical signals output through the photoelectric device310.

The optical device330reflects the optical signal collimated by the lens320at an arbitrary angle. In the present embodiment, the optical device330is a 45-degree mirror by which a path of the optical signal is changed by 90 degrees and the optical signal passes through the cover500formed with a light-transmitting coating film and finally precedes to the outside.

The monitoring photo diode (hereinafter, referred to as “mPD”,340) detects the light transmitted without being reflected by the optical device330at 45° such that the amount of light output from the photoelectric device310is measured.

The temperature detector350detects the operating temperature of the photoelectric device310. On the basis of the temperature of the photoelectric device310detected as such, the thermoelectric cooler200operates to transfer heat generated from the photoelectric device310to the outside. Such a configuration allows the operating temperature of the photoelectric device310to be kept constant so that the output optical wavelength of the photoelectric device310is stabilized.

The dielectric sub-mount400includes a first flat portion401disposed at the same height as the optical transmission platform300mounted in the platform mounting groove110of the silicon wafer100when the dielectric sub-mount400is mounted in the platform mounting groove110of the silicon wafer100; a second flat portion402configured to be in contact with a lower portion of the cover500that seals the platform mounting groove110in which the thermoelectric cooler200, the optical transmission platform300(a transmitter optical subassembly (TOSA) platform, and the dielectric sub-mount400formed with the metal pattern are mounted; and an inclined portion403connecting the first flat portion401to the second flat portion402.

The dielectric sub-mount400is provided with a plurality of metal patterns410. The plurality of metal patterns410include a radio frequency (RF) line411for high-speed signal connection, a thermoelectric cooler power supply line412, and low frequency signal lines413and414connected to sense the mPD340and the temperature detector350. Here, the signal lines413and414are preferably connected to an electrode of the cover500through a solder bump420as shown inFIG. 2.

Here, the dielectric sub-mount400is preferably formed of a material (e.g., glass) that does not easily transfer heat in order to minimize heat transfer to the photoelectric device310by a Au wire413.

Referring toFIGS. 4 and 5, the cover500is provided in a plate shape and formed of glass and covers and seals the platform mounting groove110of the silicon wafer100while providing an electrical path.

To this end, the cover500includes a body510, a sealing pad520, a redistribution layer (RDL)530, a metal via path540, and a metal pad550.

The body510is formed of a glass material and seals the platform mounting groove110of the silicon wafer100.

The sealing pad520is provided at a periphery of a lower surface of the cover500and serves to be in contact with and then seal an upper portion of the platform mounting groove110of the silicon wafer100.

The RDL530, the metal via path540, and the metal pad550are formed of metal so as to be electrically connected to the dielectric sub-mount400while enabling hermetic sealing.

The RDL530is formed at one side of an upper surface of the cover500, the metal via path540is formed to pass through the cover500while being connected to the RDL530, and the metal pad550, which is connected to the metal via path540, comes into contact with the metal pattern410of the dielectric sub-mount400when the silicon wafer100is sealed using the cover500.

Here, the electrical connection to the photoelectric device310in the optical transmission module is achieved in the order of the RDL530, the metal via path540, the metal pad550, the solder bump420, the dielectric sub-mount400, a gold (Au) wire413, the optical transmission platform300, and the thermoelectric cooler200.

In addition, the cover500is provided with an anti-reflection coating portion550formed at a bottom and a top of the cover500corresponding to an output area of optical signals reflected through the optical device330to correspond to optical wavelengths of the optical signals.

Accordingly, according to the embodiment of the present invention, the cover500is formed of a glass material that allows the inside of the optical transmission module to be visually observed so that alignment between the silicon wafer and the cover500and wafer bonding is easily performed using a vision device using light in a visible light band.

FIGS. 6A to 6Eare packaging process diagrams for describing a manufacturing process of a cooled optical transmission module device according to an embodiment of the present invention, andFIG. 7is a flowchart for describing a processing sequence of a cooled optical transmission module according to an embodiment of the present invention.

Hereinafter, a method of manufacturing a cooled optical transmission module according to an embodiment of the present invention, in detail, the entire process of manufacturing the cooled optical transmission module using a wafer level packaging process will be described with reference toFIGS. 3, 6A to 6E, and 7.

First, referring toFIG. 3, the silicon wafer100is a silicon wafer having the platform mounting groove110serving as a space for mounting the optical transmission platform300therein, wherein the platform mounting groove110is formed through a wet etching method (S100).

Thereafter, referring toFIG. 6A, the thermoelectric cooler200is bonded to the platform mounting groove110of the silicon wafer100using a die bonder or a flip chip bonder (S200). In this case, the bonding material may be provided as a product that performs thermal curing while facilitating heat transfer from a lower portion of the thermoelectric cooler200to silicon.

Subsequently, referring toFIG. 6B, the optical transmission platform300is bonded to the thermoelectric cooler200bonded to the platform mounting groove110of the silicon wafer100(S300). In this case, the bonding of the optical transmission platform300may be performed in two ways. One way is to bond the entire optical transmission platform300onto the thermoelectric cooler200, and the other way is to bond an aluminum nitride (AlN) substrate soldered with the photoelectric device310onto the thermoelectric cooler200and then mount the mPD340, the temperature detector350, the optical device (a 45-degree mirror)330, and a lens.

Thereafter, referring toFIG. 6C, the dielectric sub-mount400provided with the solder bump420is bonded to the platform mounting groove110of the platform mounting groove110at a position in which the thermoelectric cooler200is bonded (S400).

Subsequently, referring toFIG. 6D, the optical transmission platform300and the dielectric sub-mount400are bonded by the Au wire413therebetween so that the solder bump420is electrically connected to the optical transmission platform300(S500), and the cover500is bonded to the silicon wafer100(S600). Here, the hermetic sealing is achieved in two ways. One way is to overlap the lower metal pattern of the cover500and the solder of the silicon wafer100and melt the solder using a laser light having a wavelength that can transmit the cover500to achieve hermetic sealing, and the other way is to transfer heat to the cover500by applying heat to a chip tool of a flip chip bonder to melt the solder material of the silicon wafer100to achieve bonding.

According to the embodiment of the present invention, in order to overcome limitations in mass production of the existing cooled optical transmission module, a cooled optical module structure to which a wafer level packaging process is applicable and a method of manufacturing the same are proposed so that productivity is remarkably improved through mass production process and thus the price of the product is lowered.

Meanwhile, the dicing process may be performed after checking the operating characteristics of the optical transmission module at a wafer level. Here, the dicing processing may be achieved in various ways. For example, one of laser dicing, saw dicing, and scribing and breaking may be used.

After completing the dicing, referring toFIG. 6E, finally, an operating characteristic test is performed so that the optical transmission module is completed.

The cooled optical transmission module according to the embodiment of the present invention described above is a module having a single-channel, but the present invention is not limited thereto. For example, a cooled multi-channel optical transmission module may be manufactured by expanding the number of channels of the photoelectric device310.

As is apparent from the above, an assembly process is performed on a silicon wafer (silicon optical bench (SiOB)) having a space for mounting an optical transmission platform in the sequence of a photoelectric device (a laser diode: LD and an mPD), an optical device (a mirror and a lens), a thermoelectric device (a thermoelectric cooler), a glass interposer (a cover), and a thermal sensor (a temperature detector) so that the manufacturing process can be simplified and the productivity can be remarkably increased.

Although the present invention has been described in detail above with reference to the exemplary embodiments, those of ordinary skill in the technical field to which the present invention pertains should be able to understand that various modifications and alterations can be made without departing from the technical spirit or essential features of the present invention. Therefore, it should be understood that the disclosed embodiments are not limiting but illustrative in all aspects. The scope of the present invention is defined not by the above description but by the following claims, and it should be understood that all changes or modifications derived from the scope and equivalents of the claims fall within the scope of the present invention.