Adapter plate micro lens integrated CPO optical fiber vertical coupling architecture and technology

Abstract

The invention relates to the technical field of photoelectric co-packaging, in particular to an adapter plate micro lens integrated CPO optical fiber vertical coupling architecture and process. According to the invention, the micro-lens array is integrated on the adapter plate by innovatively utilizing a glue dripping tension principle, and the glue lens supports the coupling of inclined gratings with different curvature radiuses and different inclination angles, so that the preparation flexibility is higher. Compared with a traditional lens coupling scheme, no extra lens needs to be installed, the advantages of being low in cost, compact in structure, high in mechanical stability and more reasonable in stress distribution are achieved, and the characteristic of high channel density is achieved; the lens surface of the micro lens is formed by liquid tension, the lens surface is smoother, and the transmission efficiency is higher; in addition, due to integration on the adapter plate, the adapter plate has the optical interconnection function and the electric interconnection function at the same time, and the photoelectric transmission performance of the photoelectric co-packaging module can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of co-packaged photonics (CPO), and particularly to a CPO fiber vertical coupling architecture and process integrating a micro-lens on an interposer. Background Art

[0002] With the rapid development of technologies such as cloud computing, artificial intelligence, and big data, the traffic in data centers has increased sharply, requiring higher-bandwidth network connections. However, traditional electrical interconnection and communication technologies have reached a bottleneck. Therefore, the co-packaged photonics (CPO) technology has been proposed, aiming to use light instead of electricity as the information transmission medium to reduce power consumption and improve the performance and bandwidth density of the system.

[0003] In CPO technology, fiber coupling is a key technology for realizing the input and output of optical signals; in traditional fiber coupling technology, fiber vertical coupling is an important technology. However, due to limitations such as the small mode field size and small alignment tolerance of the grating coupler on the optical chip, it faces great challenges in large-scale mass production packaging.

[0004] Existing technical solutions for fiber vertical coupling are widely used in the fields of integrated optics and optical communication, especially in silicon photonics, because they can efficiently dock fibers with chips while saving lateral space. The current mainstream technical solution for fiber vertical coupling is direct alignment coupling between the fiber and the grating coupler. This coupling solution has a relatively low coupling efficiency, usually in the range of 30%-80%, and the grating template size of the optical chip is small, requiring active alignment, which is difficult to align, and the packaging efficiency is low. Or, a micro-lens is added to the fiber end face or the chip surface to focus or shape the light beam to improve the coupling efficiency, but this method has the problem of high lens manufacturing and alignment costs. In addition, there is a solution that combines a grating coupler and a micro-lens, but this solution has problems such as large packaging size, complex structure, and low reliability.

[0005] Optical micro-lenses have the advantages of expanding the spot size, increasing the alignment tolerance, and reducing the coupling and packaging difficulty; however, traditional lenses are usually large in size, and there are problems such as difficulty in fixing the package, low mechanical stability, and low packaging compactness; and there is a large gap from traditional electrical surface mount technology, with poor compatibility. The above problems limit the application of optical micro-lenses in CPO technology in different dimensions. Summary of the Invention

[0006] In view of the above problems or deficiencies, to solve the problems of alignment, size, packaging difficulty, etc. existing in fiber coupling in the existing CPO technology, the present invention provides a CPO fiber vertical coupling architecture and process integrating a micro-lens on an interposer.

[0007] A CPO fiber vertical coupling architecture integrating a micro-lens on an interposer includes: an interposer, a glue lens, an optical chip, an electrical chip, a packaging substrate, and a fiber.

[0008] The adapter board is provided with a circular lens through - hole, a circular conductive through - hole and a metal conductive post.

[0009] Among them, after the circular conductive through - hole is filled with a conductive material, it forms a metal conductive post, which is used as an electrical connection channel between the upper and lower layer chips on the adapter board and the packaging substrate.

[0010] The circular lens through - hole is arranged in the corresponding area of the adapter board above the grating coupling area. Glue is arranged in the circular lens through - hole. The glue forms a curved surface towards the lower surface of the adapter board under the action of liquid tension and gravity. After the glue is cured, a glue lens is obtained; the glue lens is divided into two surfaces, a convex surface and a concave surface. The convex surface protrudes beyond the surface of the adapter board, and the concave surface is recessed into the circular lens through - hole.

[0011] The optical fiber is aligned and fixed with its end face on the concave side of the glue lens in the circular lens through - hole. An equivalent single - convex lens is formed from the end face of the optical fiber to the lower surface of the glue lens on the adapter board.

[0012] After the optical fiber, the adapter board and the optical chip are all fixed, the gratings on the surfaces of the optical fiber - glue lens - optical chip are physically aligned; the gap height after the adapter board and the optical chip are fixed is higher than the height of the glue lens protruding beyond the adapter board, and the gap height matches the focal length of the lens, so that the focal point of the lens is on the chip grating surface; and it meets the requirement that the size of the converging light spot matches the mode spot size of the grating coupler. Because the glue lens is a curved - surface lens, it can convert the high - speed divergent grating emitted by the optical chip below the adapter board into a parallel beam with a larger mode diameter. While realizing the fiber - to - chip optical vertical coupling, it provides a larger alignment tolerance for fiber - optic coupling packaging.

[0013] Further, after the glue lens is formed, the optical fiber is dropped with glue again on the concave surface of the glue lens until the glue overflows the upper surface of the adapter board, and then the end face of the optical fiber is aligned with the circular lens through - hole and the glue is cured for the second time.

[0014] Further, the curing method of the glue is photo - curing, thermal - curing, moisture - curing, two - component curing or self - curing.

[0015] Further, the material of the glue is epoxy resin, acrylate, polyurethane or silica gel.

[0016] Further, the central axis of the curved surface of the glue lens is perpendicular to the plane of the adapter board at 90 degrees for coupling 90 - degree vertical - plane emission beams; or, the central axis of the curved surface is inclined to the plane of the adapter board and forms a non - 90 - degree vertical angle with the plane of the adapter board to be applicable to inclined grating coupling.

[0017] Further, the circular lens through - hole and the circular conductive through - hole are processed by wet etching, dry etching or laser - induced etching processes.

[0018] Furthermore, the material of the adapter board is glass, silicon or ceramic.

[0019] Furthermore, the circular lens through-holes are an array of through-holes to meet the application scenarios of the fiber array.

[0020] Furthermore, the adapter board and the optical chip are fixed by pads and solder balls; the material of the solder balls is gold-tin solder, tin-silver solder; the height after the solder balls are cured is the clearance height after the adapter board and the optical chip are fixed.

[0021] In summary, the present invention innovatively proposes to integrate a microlens array on the adapter board, set circular lens through-holes on the adapter board, and cure the glue after dripping it into the through-holes, and form a glue lens by gravity. It further proposes to integrate a focusing microlens array with an inclined angle on the adapter board, and prepare a microlens with an inclined curved surface axis by tilting the adapter board to be applicable to inclined grating coupling. Compared with the traditional lens coupling scheme, the glue lens scheme used in the present invention has the advantages of low cost, compact structure, high mechanical stability, more reasonable stress distribution because it does not require additional lens installation, and has the characteristic of high channel density. Compared with the microlenses prepared by the traditional CMOS process, the microlenses of the present invention form the lens surface by liquid tension, the lens surface is smoother, and the transmission efficiency is higher. Compared with the traditional microlens preparation processes such as traditional CMOS and nanoimprinting, the present invention can flexibly prepare microlens structures with different curvature radii and different inclined angles by adjusting the inclined angle and aperture size of the adapter board, and has higher preparation flexibility. Compared with the traditional lens coupling scheme, the present invention integrates microlenses on the adapter board, enabling the adapter board to have both optical interconnection and electrical interconnection functions, and can significantly improve the optical and electrical transmission performance of the optoelectronic co-packaging module. Description of the Drawings

[0022] Figure 1 is a schematic cross-sectional view of the glue lens fiber coupling and packaging structure of the present invention.

[0023] Figure 2 is a top view of the adapter board of the glue lens in the embodiment.

[0024] Figure 3 is a schematic diagram of the preparation and packaging process of the adapter board of the glue lens in the embodiment.

[0025] Figure 4 is a schematic cross-sectional view of the adapter board structure of the glue lens in Embodiment 2.

[0026] Figure 5 is a schematic cross-sectional view of the adapter board structure of the glue lens in Embodiment 3.

[0027] Figure numerals: (1) adapter plate, (2) circular lens through hole, (3) glue lens, (4) metal conductive column, (5) optical chip, (6) grating coupler, (7) solder ball, (8) optical fiber. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Basic principles of the present invention:

[0030] like Figure 3 FIG. 1 shows a process flow for preparing a microlens on an adapter plate according to an embodiment of the present invention.

[0031] First, two through holes are prepared on an adapter plate (such as glass or silicon): one is used to fill a metal conductive material to form a metal conductive column (4); and the other circular lens through hole (2) is used to fill an optically transparent UV curing adhesive.

[0032] As shown in step 2, a UV curing glue is dripped into the circular lens through hole (2), and a curved lens is formed under the action of liquid tension. The curvature of the lens is closely related to the aperture of the circular lens through hole. The larger the aperture, the weaker the glue tension constraint, the more severe the gravity stretching, the smaller the curvature radius, and the shorter the focal length. Therefore, by designing a suitable aperture, a microlens with a specific focal length can be prepared. After the glue curved surface is formed, the glue is irradiated with ultraviolet light to complete the curvature, forming a fixed lens shape. The lens includes two surfaces, a convex surface and a concave surface. The convex surface extends beyond the surface of the adapter plate, and the concave surface is sunken into the circular lens through hole (2).

[0033] After the adapter plate with the glue lens is packaged with the optical chip, the glue lens concave surface is dripped with glue for a second time until it overflows onto the upper surface of the adapter plate, and the optical fiber end face is aligned with the concave surface of the circular lens through hole (2) and immersed in liquid ultraviolet curing agent, and the glue is cured for a second time. At this point, the optical fiber end face is connected to the lower surface (convex surface) of the adapter plate lens to form an equivalent single convex lens, which can convert the high-speed divergent grating emitted by the optical chip below into a parallel beam with a larger pattern diameter (such as Figure 1 This design can provide greater alignment tolerance for fiber-coupled packages.

[0034] In addition, the grating coupler of the optical chip usually has a certain diffraction angle, which is not a 90-degree vertical coupling situation. In order to be applied to this scenario, the present invention is Figure 3 In the second step of the process, the plane of the adapter plate can be tilted appropriately to tilt the axis of the spherical surface of the glue, thereby achieving optical coupling at a specific angle (such as Figure 5 shown).

[0035] Example 1:

[0036] like Figure 1As shown, the adapter board (1) is made of glass with a thickness of 200 um. Conductive copper pillars (4) are provided on the adapter board. The diameter of the circular lens via is 11 um. There is an ultraviolet curable glue lens (3) inside the circular lens hole, and the focal length of the glue lens is 20 um. The optical chip (5) is arranged below the adapter board (1), and the grating coupler of the optical chip faces upward and is aligned with the center of the glue lens (3). The optical fiber (8) is a single-mode optical fiber with a wavelength of 1550 nm. The adapter board and the optical chip (5) are fixed with a gold-tin solder (7).

[0037] Example 2:

[0038] As Figure 4 shown, the adapter board (1) is made of glass with a thickness of 200 um. Conductive copper pillars (4) are provided on the adapter board. The diameter of the circular lens via is 20 um. There is an ultraviolet curable glue lens (3) inside the circular lens hole, and the focal length of the glue lens is 15 um. Other settings are the same as in Example 1: The optical chip (5) is arranged below the adapter board (1), and the grating coupler of the optical chip faces upward and is aligned with the center of the glue lens (3). The optical fiber (8) is a single-mode optical fiber with a wavelength of 1550 nm. The adapter board and the optical chip (5) are fixed with a gold-tin solder (7).

[0039] Example 3:

[0040] As Figure 5 shown, the adapter board (1) is made of glass with a thickness of 500 um. Conductive copper pillars (4) are provided on the adapter board. The diameter of the circular lens via is 11 um. There is an ultraviolet curable glue lens (3) inside the circular lens hole, and the focal length of the glue lens is 20 um. The central axis of this glue lens is inclined at an 8-degree angle to couple the tilted diffraction grating, so that the diffraction angle of the grating diffraction beam is parallel to the central axis of the lens. To prepare this glue lens, when performing Figure 3 process step 2, the adapter board is in an inclined state and the glue lens is cured with ultraviolet light. Other settings are the same as in Example 1: The optical chip (5) is arranged below the adapter board (1), and the grating coupler of the optical chip faces upward and is adapted to the glue lens (3) so that the central axis of the beam coincides with the central axis of the lens. The optical fiber (8) is a single-mode optical fiber with a wavelength of 1550 nm. The adapter board and the optical chip (5) are fixed with a gold-tin solder (7).

[0041] As can be seen from the above embodiments, the present invention innovatively integrates a microlens array on the adapter board by utilizing the principle of epoxy resin tension, and the glue lens supports tilted grating coupling with different curvature radii and different tilt angles, having higher preparation flexibility. Compared with the traditional lens coupling scheme, the present invention does not require additional installation of lenses, and has the advantages of low cost, compact structure, high mechanical stability, more reasonable stress distribution, and the characteristic of high channel density; the microlens forms a lens surface by liquid tension, the lens surface is smoother, and the transmission efficiency is higher; and because it is integrated on the adapter board, the adapter board simultaneously has the functions of optical interconnection and electrical interconnection, which can significantly improve the optical and electrical transmission performance of the optoelectronic co-packaging module.

Claims

1. A CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate, comprising: An adapter board, an optical chip, an electrical chip, a packaging substrate, and an optical fiber, characterized in that: it further includes a glue lens; The adapter board is provided with a circular lens through-hole, a circular conductive through-hole, and a metal conductive post; Among them, after the circular conductive through-hole is filled with a conductive material, a metal conductive post is formed, which is used as an electrical connection channel between the upper and lower layer chips on the adapter board and the packaging substrate; The circular lens through-hole is arranged in the corresponding area of the adapter board above the grating coupling area. There is glue in the circular lens through-hole. The glue forms a curved surface on the lower surface of the adapter board through the action of liquid tension and gravity. After the glue is cured, a glue lens is obtained; The glue lens is divided into a convex surface and a concave surface. The convex surface protrudes beyond the surface of the adapter board, and the concave surface is recessed into the circular lens through-hole; The optical fiber is aligned with and fixed to the concave side of the glue lens of the circular lens through-hole with its end face, and an equivalent single convex lens is formed from the end face of the optical fiber to the lower surface of the glue lens of the adapter board; After the optical fiber, the adapter board, and the optical chip are all fixed, the gratings on the surfaces of the optical fiber-glue lens-optical chip are physically aligned; the gap height after the adapter board and the optical chip are fixed is higher than the height of the glue lens protruding from the adapter board, and the gap height matches the focal length of the lens, so that the focal point of the lens is on the chip grating surface; and it satisfies that the size of the converging spot matches the mode spot size of the grating coupler, realizing the vertical coupling of the optical fiber and the optical chip.

2. The CPO optical fiber vertical coupling architecture integrated with the adapter board microlens according to claim 1, characterized in that: After the glue lens is formed, the optical fiber is drop-coated with glue on the concave surface of the glue lens until the glue overflows the upper surface of the adapter board, and then the end face of the optical fiber is aligned with the circular lens through-hole and the glue is cured for the second time.

3. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The curing method of the glue is photocuring, thermal curing, moisture curing, two-component curing or self-curing.

4. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The material of the glue is epoxy resin, acrylate, polyurethane or silica gel.

5. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The central axis of the curved surface of the glue lens is perpendicular to the plane of the adapter board by 90 degrees, and is used to couple the 90-degree vertical surface-emitting light beam; or, the central axis of the curved surface is inclined to the plane of the adapter board and forms a non-90-degree vertical angle with the plane of the adapter board.

6. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The circular lens through-hole and the circular conductive through-hole are processed by wet etching, dry etching or laser-induced etching process.

7. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The material of the adapter board is glass, silicon or ceramic.

8. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The circular lens through-hole is a through-hole array.

9. The CPO fiber vertical coupling architecture with integrated microlenses on an adapter plate as claimed in claim 1, characterized in that: The adapter board and the optical chip are fixed by pads and solder balls; the material of the solder balls is gold-tin solder, tin-silver solder; the height of the solder balls after curing is the gap height after the adapter board and the optical chip are fixed.

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