High speed germanium-silicon photodiode and method of manufacturing the same

Abstract

The embodiment of the present application provides a high-speed germanium-silicon photodiode and a manufacturing method thereof, and belongs to the technical field of photoelectric detection equipment. The high-speed germanium-silicon photodiode comprises a wafer, a silicon lens arranged on a first plane of the wafer, a germanium absorption layer arranged on a second plane of the wafer and the center of the germanium absorption layer is aligned with the center of the silicon lens, the surface of the germanium absorption layer opposite to the second plane is a photosensitive surface, a first electrode arranged on the second plane, a second electrode arranged on the photosensitive surface and covering the photosensitive surface, and a passivation layer arranged on the second plane and covering the germanium absorption layer, the first electrode and the second electrode. Incident light is converged by the silicon lens, enters the germanium absorption layer after the wafer, is absorbed, and the incident light which is not absorbed continues to pass through the germanium absorption layer and the passivation layer to the second electrode and is reflected back to the germanium absorption layer to be absorbed again. The high-speed germanium-silicon photodiode can match inverted packaging and has high responsivity and high effective aperture.

Description

Technical Field

[0001] This invention relates to the technical field of photoelectric detection equipment, and in particular to a high-speed germanium-silicon photodiode and its manufacturing method. Background Technology

[0002] A high-speed photodiode is a photoelectric detection device that converts optical signals into electrical signals at high frequencies. It features fast response, high sensitivity, and a wide wavelength range, and is widely used in optoelectronic fields such as communications, radar, and fiber optics. With the development of technologies such as 5G communications, computing networks, and high-speed fiber optics, the requirements for high bandwidth and high response speed of high-speed photodiodes are becoming increasingly stringent.

[0003] For surface-incidence high-speed photodiodes, in order to improve the operating bandwidth of their photoelectric conversion chips, common techniques include thinning the thickness of the light absorption region to increase the carrier drift bandwidth and reducing the area of ​​the light absorption region to increase the RC (resistance and capacitance) bandwidth.

[0004] However, reducing the thickness and area of ​​the light absorption region directly affects the response speed and equivalent aperture of the high-speed photodiode. Reducing the area of ​​the light absorption region also decreases the coupling tolerance and coupling efficiency between the optical fiber and the high-speed photodiode.

[0005] Meanwhile, as the operating frequency of high-speed photodiodes further increases, such as single-wave 112GBand photodiodes, their manufacturing processes also need to consider compatibility with inverted packaging processes to reduce the wiring between them and transimpedance amplifiers (TIAs). This avoids the adverse effects of parasitic inductance and capacitance caused by wire bonding on signal impedance matching and suppresses signal crosstalk between signal transmission channels. Therefore, further optimization is still needed in the structure and manufacturing process of high-speed photodiodes.

[0006] In view of this, the present invention proposes a novel high-speed germanium-silicon photodiode and its manufacturing method to solve all or part of the above problems. Summary of the Invention

[0007] To address at least one of the aforementioned problems and defects in the prior art, embodiments of the present invention provide a high-speed germanium-silicon photodiode and its manufacturing method. By respectively disposing a silicon lens and a germanium absorption layer on opposite surfaces of a wafer, the wafer can be used to increase the optical path and converge incident light to improve the equivalent aperture. Furthermore, the metal electrode covering the photosensitive surface of the germanium absorption layer allows incident light that was not absorbed during its first pass through the germanium absorption layer to be reflected back to the germanium absorption layer for re-absorption, thus improving response. Simultaneously, inverted packaging can be used to reduce parasitic capacitance and inductance. The technical solution is as follows:

[0008] According to one aspect of the present invention, a high-speed germanium-silicon photodiode is provided. The high-speed germanium-silicon photodiode comprises:

[0009] wafers;

[0010] A silicon lens is disposed on the first plane of the wafer;

[0011] A germanium absorption layer is disposed on a second plane opposite to a first plane of the wafer, and the center of the germanium absorption layer is aligned with the center of the silicon lens. The side of the germanium absorption layer opposite to the second plane is the photosensitive side.

[0012] The first electrode is disposed on the second plane of the wafer;

[0013] The second electrode is disposed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface.

[0014] A passivation layer is disposed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode.

[0015] The incident light is focused onto the wafer by a silicon lens and then enters the germanium absorption layer where it is absorbed. The unabsorbed incident light continues to pass through the germanium absorption layer and passivation layer in sequence, and after reaching the second electrode, it is reflected back to the germanium absorption layer where it is absorbed again.

[0016] In some embodiments, the wafer further includes a first ion-doped layer disposed on a second plane of the wafer, and the germanium absorber layer and the first electrode are in electrical contact with the first ion-doped layer.

[0017] In some embodiments, preferably, the germanium absorber layer includes a germanium structure, an amorphous silicon layer, and an antireflection film arranged sequentially in a direction away from the wafer.

[0018] In some embodiments, specifically, a germanium structure is disposed on a first ion-doped layer of the wafer, and the side of the germanium structure in contact with the first ion-doped layer is a light-absorbing surface.

[0019] In some embodiments, specifically, an amorphous silicon layer is disposed on a germanium structure and the side of the amorphous silicon layer opposite to the germanium structure is a photosensitive surface. The amorphous silicon layer also includes a second ion-doped layer disposed on the photosensitive surface, and the second electrode is in electrical contact with the second ion-doped layer.

[0020] In some embodiments, specifically, the antireflective film is disposed on the photosensitive surface of the amorphous silicon layer, and the material of the antireflective film is any one of silicon dioxide, aluminum oxide, titanium oxide, magnesium fluoride, and graphene.

[0021] In some embodiments, alternatively, when the first ion-doped layer is P-type ion implanted, the second ion-doped layer is N-type ion implanted. Alternatively, when the first ion-doped layer is N-type ion implanted, the second ion-doped layer is P-type ion implanted.

[0022] In some embodiments, the passivation layer may alternatively be made of any one of silicon dioxide, silicon oxide, or silicon nitride.

[0023] In some embodiments, preferably, the high-speed germanium-silicon photodiode further includes a metal bump structure for inverted packaging, the metal bump structure being exposed outside the passivation layer for soldering to a transimpedance amplifier or substrate. The metal bump structure includes a first metal bump structure connected to a first electrode and a second metal bump structure connected to a second electrode.

[0024] In some embodiments, the high-speed germanium-silicon photodiode may alternatively include a protective layer disposed on a first plane of the wafer around a silicon lens, the height of the protective layer being equal to the height of the silicon lens.

[0025] According to another aspect of the present invention, a method for manufacturing a high-speed germanium-silicon photodiode is provided for manufacturing the high-speed germanium-silicon photodiode described above. The manufacturing method includes:

[0026] Provide wafers;

[0027] A germanium absorption layer, a first electrode, a second electrode, and a passivation layer are fabricated sequentially. The germanium absorption layer and the first electrode are formed on the second plane of the wafer, the second electrode is formed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface, and the passivation layer is formed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode.

[0028] After exposing the first and second electrodes in the passivation layer through openings, metal bump structures are fabricated. Then, a first metal bump structure corresponding to the first electrode and a second metal bump structure corresponding to the second electrode are formed on the outside of the passivation layer through metal connection and metal epitaxial growth.

[0029] After the first bonding wafer is bonded to the outside of the passivation layer using the first bonding adhesive, it is flipped and inverted.

[0030] A silicon lens is formed on the first plane of the wafer, the center of which is aligned with the center of the germanium absorption layer;

[0031] High-speed germanium-silicon photodiodes are obtained by removing the first bonding wafer and the first bonding adhesive.

[0032] According to another aspect of the present invention, a method for manufacturing a high-speed germanium-silicon photodiode is provided for manufacturing the high-speed germanium-silicon photodiode described above. The manufacturing method includes:

[0033] Provide wafers;

[0034] A germanium absorption layer, a first electrode, a second electrode, and a passivation layer are fabricated sequentially. The germanium absorption layer and the first electrode are formed on the second plane of the wafer, the second electrode is formed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface, and the passivation layer is formed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode.

[0035] After bonding the second bonding wafer to the outside of the passivation layer with the second bonding adhesive, it is flipped and inverted.

[0036] A silicon lens is formed on the first plane of the wafer, the center of which is aligned with the center of the germanium absorption layer;

[0037] The third bonding wafer is bonded to the outside of the silicon lens using a third bonding adhesive, and the second bonding wafer and the second bonding adhesive are removed.

[0038] After exposing the first and second electrodes in the passivation layer through openings, metal bump structures are fabricated. Then, a first metal bump structure corresponding to the first electrode and a second metal bump structure corresponding to the second electrode are formed on the outside of the passivation layer through metal connection and metal epitaxial growth.

[0039] High-speed germanium-silicon photodiodes are obtained by removing the third bonding wafer and the third bonding adhesive.

[0040] In some embodiments, alternatively, after exposing the first and second electrodes through openings in the passivation layer, the step of fabricating the metal bump structure specifically includes:

[0041] A first metal connecting post and a second metal connecting post are grown on the first electrode and the second electrode, respectively.

[0042] Nickel-palladium-gold or silver-tin solder are grown on the first and second metal connecting pillars, respectively.

[0043] Nickel-palladium-gold or silver-tin solder is reflowed at high temperature to form a first metal bump structure and a second metal bump structure.

[0044] The high-speed germanium-silicon photodiode and its manufacturing method provided by the embodiments of the present invention have at least one or a portion of the following advantages:

[0045] (1) By setting the silicon lens and the germanium absorption layer on opposite surfaces of the wafer, the wafer can be used to increase the optical path and converge the incident light. On the other hand, the metal electrode covering the photosensitive surface of the germanium absorption layer can be used to reflect the incident light that was not absorbed when it first passed through the germanium absorption layer back to the germanium absorption layer and be absorbed again.

[0046] (2) By covering the outside of the photosensitive surface of the germanium absorption layer with the second electrode, the smooth metal surface of the second electrode can be used to reflect the incident light. The reflected light can pass through the photosensitive surface again and enter the germanium absorption layer to be absorbed, thereby reducing incident light loss and improving the photodiode responsivity.

[0047] (3) By placing the silicon lens on the opposite side of the germanium absorption layer on the wafer, the optical path of the incident light can be further increased, which helps to further increase the equivalent aperture and further improve the responsivity of the photodiode while ensuring high operating bandwidth.

[0048] (4) By forming a metal bump structure on the first and second electrodes to match the inverted package and directly solder it to the transimpedance amplifier or substrate, silicon through-hole is effectively avoided, the signal transmission path is shortened, and parasitic capacitance and parasitic inductance caused by the package are reduced.

[0049] (5) By setting a wafer protective layer of the same height around the silicon lens, the silicon lens can be effectively protected on the one hand, and the dicing process can be facilitated on the other hand to ensure the stability of the subsequent packaging and transportation process and the product quality.

[0050] (6) Functional layers are fabricated on opposite surfaces of a wafer by using bonding adhesive and bonding wafer respectively. The process is simple and the yield is high. Attached Figure Description

[0051] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0052] Figure 1 A schematic diagram of the cross-sectional structure of a high-speed germanium-silicon photodiode according to an embodiment of the present invention;

[0053] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the germanium absorption layer in a high-speed germanium-silicon photodiode;

[0054] Figure 3 This is a schematic diagram of the cross-sectional structure of a high-speed germanium-silicon photodiode according to yet another embodiment of the present invention;

[0055] Figure 4 This is a process flow diagram of the manufacturing method of a high-speed germanium-silicon photodiode according to Embodiment 1 of the present invention;

[0056] Figure 5 According to Figure 4 The diagram shows the cross-sectional structure obtained after completing steps S110-S130 of the process flow.

[0057] Figure 6 According to Figure 4A schematic diagram of the cross-sectional structure obtained after completing step S140 of the process flow shown;

[0058] Figure 7 According to Figure 4 A schematic diagram of the cross-sectional structure obtained after completing step S150 of the process flow shown;

[0059] Figure 8 This is a process flow diagram of the manufacturing method of a high-speed germanium-silicon photodiode according to Embodiment 2 of the present invention;

[0060] Figure 9 According to Figure 8 The diagram shows the cross-sectional structure obtained after completing steps S210-S220 of the process flow.

[0061] Figure 10 According to Figure 8 A schematic diagram of the cross-sectional structure obtained after completing step S230 of the process flow shown;

[0062] Figure 11 According to Figure 8 A schematic diagram of the cross-sectional structure obtained after completing step S240 of the process flow shown;

[0063] Figure 12 According to Figure 8 The diagram shows the cross-sectional structure obtained after completing step S250 of the process flow. Detailed Implementation

[0064] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof.

[0065] It should also be understood that although the terms "first," "second," "third," etc., may be used in the following embodiments of the present invention to describe a component comprising two or more of the same component, these components should not be limited to these terms, which are only used to distinguish each component from one another. Furthermore, descriptions indicating orientation such as "upper," "lower," "left," and "right" are merely illustrative of the relative positions of components and should not be construed as a limitation of the present invention.

[0066] Currently, most techniques for optimizing the structure of surface-incident high-speed photodiodes focus on improving the structure of the light absorption region, such as reducing the thickness and / or area of ​​the light absorption region. Reducing the thickness of the light absorption region helps to improve the drift bandwidth of photogenerated carriers to some extent, while reducing the area of ​​the light absorption region helps to improve the RC (resistance-capacitance) bandwidth to some extent, thereby achieving the goal of increasing the operating bandwidth of the photodiode's photoelectric conversion chip.

[0067] However, shrinking the light absorption region reduces the coupling tolerance and coupling efficiency between the optical fiber and the photodiode, thus affecting the photodiode's responsivity and equivalent aperture. Furthermore, as the operating frequency of the photodiode is further increased, the need for photodiode compatibility with inverted packaging processes necessitates through-silicon vias (TSVs) to reduce the impact of parasitic inductance and capacitance on signal impedance matching.

[0068] It is evident that simply changing the size of the light absorption region is no longer sufficient to meet the performance requirements of high-speed photodiodes in the ever-evolving optoelectronic technology.

[0069] Therefore, the embodiments of the present invention provide a novel high-speed germanium-silicon photodiode and its manufacturing method. The high-speed germanium-silicon photodiode, by respectively setting a silicon lens and a germanium absorption layer on opposite surfaces of a wafer, can increase the optical path and focus the incident light using the wafer. On the other hand, in conjunction with the metal electrode covering the photosensitive surface of the germanium absorption layer, the incident light that was not absorbed the first time it passed through the germanium absorption layer is reflected back to the germanium absorption layer and absorbed again. This effectively ensures the high responsivity and high equivalent aperture of the photodiode, thereby maintaining high bandwidth operating efficiency. At the same time, its overall structure can be directly compatible with the flip-chip packaging process.

[0070] See Figure 1 The image shows a cross-sectional structure of a high-speed germanium-silicon photodiode 100 according to an embodiment of the present invention. The high-speed germanium-silicon photodiode 100 includes six main parts: a wafer 110, a germanium absorption layer 120, a first electrode 131, a second electrode 132, a passivation layer 140, and a silicon lens 170, as well as metal bump structures (first metal bump structure 161 and second metal bump structure 162) for inverted packaging.

[0071] like Figure 1 As shown, in the high-speed germanium-silicon photodiode 100, the wafer 110 has two planes, so as to... Figure 1Taking a high-speed germanium-silicon photodiode 100 as an example, the upper surface of the wafer 110, i.e., the first plane, serves as the side where light is incident, while its lower surface, i.e., the second plane, serves as the side where light is absorbed. Further, a silicon lens 170 for converging the incident light is disposed on the first plane of the wafer 110, and a light absorption region for absorbing the incident light, i.e., a germanium absorption layer 120, is disposed on the second plane of the wafer 110. The center of the germanium absorption layer 120 is aligned with the center of the silicon lens 170. The side of the germanium absorption layer 120 opposite to the second plane of the wafer 110 is the photosensitive surface. Figure 1 (The surface below the germanium absorption layer 120 shown). The first electrode 131 is disposed on the second plane of the wafer 110, and the second electrode 132 is disposed on the photosensitive surface of the germanium absorption layer 120, and the second electrode 132 completely covers the photosensitive surface of the germanium absorption layer 120. The passivation layer 140 is disposed on the second plane of the wafer 110 and completely covers and encapsulates the germanium absorption layer 120, the first electrode 131, and the second electrode 132.

[0072] The high-speed germanium-silicon photodiode 100, configured as described above, forms a back-illuminated surface-incident photodiode structure because light incident and absorption occur on the two surfaces of the wafer 110, respectively. When the high-speed germanium-silicon photodiode 100 is in operation, the incident light is focused onto the wafer 110 by the silicon lens 170 and then enters the germanium absorption layer 120 where it is absorbed. The unabsorbed incident light continues to pass sequentially through the germanium absorption layer 120 and the passivation layer 140 to reach the second electrode 132, where it is reflected back to the germanium absorption layer 120 and absorbed again to improve its responsivity.

[0073] See Figure 2 The specific cross-sectional structure of the germanium absorber layer 120 is shown.

[0074] In one example, preferably, the germanium absorber layer 120 includes a germanium structure 121, an amorphous silicon layer 122, and an antireflection film 123 arranged sequentially in a direction away from the wafer 110.

[0075] In one example, specifically, a germanium structure 121 is epitaxially grown on the second plane of wafer 110. The germanium structure 121 is the main structure in the germanium absorption layer 120 used to absorb incident light. The thickness of the germanium structure 121 typically ranges from 0.5 to 2.0 μm. Next, an amorphous silicon layer 122 is epitaxially grown on the germanium structure 121. The thickness of the amorphous silicon layer 122 typically ranges from 0.05 to 0.2 μm. At this point, the top of the amorphous silicon layer 122 is the photosensitive surface of the germanium absorption layer 120. Finally, an antireflection film 123 is deposited on the photosensitive surface. The antireflection film 123 is essentially an anti-reflection structure layer or passivation layer, enabling the detection of the wavelength of the incident light. Alternatively, the material of the antireflection film 123 can be any one of silicon dioxide, aluminum oxide, titanium oxide, magnesium fluoride, or graphene.

[0076] In one example, the upper surface of the photosensitive surface covering the antireflective film 123 can be polished smooth using a chemical mechanical polishing (CMP) process, typically with a thickness of 1.0-3.0 μm.

[0077] Those skilled in the art will understand that the specific parameters of each layer in the germanium absorber layer 120 (e.g., the average planar area of ​​the germanium absorber layer 120, the thickness of the germanium structure 121 and the amorphous silicon layer 122, or the ratio of their thicknesses, the thickness of the antireflection film 123, etc.) and the specific materials used for each layer need to be specifically designed according to the actual performance requirements of the high-speed photodiode. The above examples are only illustrative examples and should not be construed as limiting the present invention.

[0078] In one example, specifically, combining Figure 1 and Figure 2 As shown, the wafer 110 also includes a first ion-doped layer 111, which is disposed on the second plane of the wafer 110. The germanium absorber layer 120 and the first electrode 131 are in electrical contact with the first ion-doped layer 111.

[0079] Corresponding to the electrical contact between the first electrode 131 and the first ion-doped layer 111, a second ion-doped layer (not shown) is formed on the amorphous silicon layer 122 of the germanium absorber layer 120, and the second electrode 132 is in electrical contact with the second ion-doped layer. The first electrode 131 and the second electrode 132 form a pair of anode and cathode electrodes.

[0080] In one example, preferably, such as Figure 1 As shown, a portion of the second electrode 132 needs to cover directly above the germanium absorber layer 120. Figure 1 (Directly below the germanium absorption layer 120). This arrangement effectively reflects a portion of the incident light that is not absorbed by the germanium absorption layer 120 through the second electrode 132 covering the germanium absorption layer 120, and the reflected incident light returns to the germanium absorption layer 120 to be absorbed again. Therefore, the high-speed germanium silicon photodiode 100 improves its light absorption rate without changing the volume of its germanium absorption layer 120 (reducing its thickness and / or area), thereby improving the photoresponsivity of the high-speed germanium silicon photodiode 100.

[0081] Those skilled in the art will understand that both the first electrode 131 and the second electrode 132 are metal electrodes, and their specific shapes and dimensions need to be designed according to the actual size requirements of the high-speed photodiode and the subsequent inverted packaging process requirements. Figure 1 The shapes of the first electrode 131 and the second electrode 132 shown are merely illustrative examples and should not be construed as a limitation of the present invention by those skilled in the art.

[0082] Meanwhile, a portion of the second electrode 132 needs to completely cover the top of the germanium absorber layer 120, and another portion needs to be reserved for the connection bumps (second metal bump structure 162) required for subsequent inverted packaging. The specific value of the distance between the first metal bump structure 161 connected to the first electrode 131 and the second metal bump structure 162 needs to be designed according to the actual substrate structure dimensions during inverted packaging. Figure 1 The shapes of the first electrode 131 and the second electrode 132 shown, as well as their relative positions, are merely illustrative examples and should not be construed as a limitation of the invention by those skilled in the art.

[0083] In one example, alternatively, P-type ions and N-type ions can be implanted into the wafer 110 and the germanium absorber layer 120 respectively by processes such as ion implantation, epitaxial growth, and dopant diffusion to form ion-doped layers of anode and cathode, and metal electrodes of corresponding polarities can be formed on the ion-doped layers of their respective polarities to form a pair of anode and cathode electrodes.

[0084] In one example, alternatively, when the first ion-doped layer 111 is P-type ion implanted, the second ion-doped layer is N-type ion implanted. Alternatively, when the first ion-doped layer 111 is N-type ion implanted, the second ion-doped layer is P-type ion implanted. That is, when the ion doping types are interchanged, the polarities of the electrodes formed on the two doped layers are also interchanged. For example, if a first electrode 131 is grown on wafer 110 using P-type ion implantation as a cathode, then a second electrode 132 is grown on germanium absorber layer 120 using N-type ion implantation as an anode. Conversely, the first electrode 131 is the anode, and the second electrode 132 is the cathode. However, for the subsequent connection of the two electrodes to the metal bump structure for inverted packaging, and because the second electrode 132 needs to cover the top surface of germanium absorber layer 120, the position, shape, and size of the two electrodes remain unchanged according to the actual design requirements.

[0085] In one example, preferably, a passivation layer 140 is formed by epitaxial growth on the second plane of wafer 110. More preferably, the passivation layer 140 completely covers the germanium absorber layer 120, the first electrode 131, and the second electrode 132.

[0086] In one example, alternatively, the material of the passivation layer 140 can be any one of silicon dioxide, silicon oxide, or silicon nitride.

[0087] In one example, alternatively, since the reflection of incident light by the second electrode 132 encased inside the passivation layer 140 causes the light to undergo multiple reflections within the passivation layer 140, the material selection and thickness of the passivation layer 140 need to be optimized according to the specific requirements of the photoelectric conversion of the actual photodiode in order to reduce light loss.

[0088] Those skilled in the art will understand that the above description of the structural parameters of the passivation layer 140 and the materials that can be used is merely an illustrative example and should not be construed as a limitation of the present invention.

[0089] In one example, preferably, such as Figure 1 As shown, in order to make the high-speed germanium silicon photodiode 100 compatible with the inverted packaging process, a metal bump structure for inverted packaging is provided below the high-speed germanium silicon photodiode 100 (on the side near the first electrode 131 and the second electrode 132), including a first metal bump structure 161 and a second metal bump structure 162. The metal bump structure is exposed on the outside of the passivation layer 140 for direct soldering to the transimpedance amplifier or the substrate.

[0090] In one example, the first metal bump structure 161 and the second metal bump structure 162 are metal-connected to the first electrode 131 and the second electrode 132, respectively. Alternatively, the first metal bump structure 161 and the second metal bump structure 162 can be metal bump structures that are easy to weld, such as spheres, ellipsoids, and hemispheres. This example is merely illustrative and should not be construed as a limitation of the invention by those skilled in the art.

[0091] Thus, the high-speed germanium-silicon photodiode 100 can bypass traditional wire bonding packaging and instead employ an inverted packaging process, directly soldering it to the transimpedance amplifier or substrate via the first metal bump structure 161 and the second metal bump structure 162. This shortens the signal transmission path and reduces parasitic inductance and capacitance. It effectively avoids metal vias in the silicon structure, minimizing the impact on the photoelectric conversion performance of the high-speed photodiode.

[0092] In one example, such as Figure 1 As shown, a lens structure (silicon lens 170) can be formed on the first plane of wafer 110 by etching. The silicon lens 170 itself has the function of converging incident light. By placing the silicon lens 170 on the side of wafer 110 opposite to germanium absorption layer 120, the incident light can be converged in wafer 110 first, which can increase the optical path of the incident light and thus obtain a very high equivalent aperture.

[0093] In one example, preferably, the lens structure is made of silicon. Since silicon has virtually no absorption of infrared light in the O-band (wavelength range 1260-1360nm), both the silicon lens 170 made of silicon and the wafer 110 made of silicon (e.g., high-resistivity silicon) are more suitable as a medium for transmitting and converging light in the O-band infrared signal.

[0094] See Figure 3 The cross-sectional structure of a high-speed germanium-silicon photodiode 200 according to another embodiment of the present invention is shown.

[0095] The overall structure of the high-speed germanium-silicon photodiode 200 is basically the same as that of the high-speed germanium-silicon photodiode 100 described above. It includes six main parts: wafer 210a, germanium absorption layer 220, first electrode 231, second electrode 232, passivation layer 240, and silicon lens 270, as well as metal bump structures (first metal bump structure 261 and second metal bump structure 262) for inverted packaging. The specific structural settings will not be described in detail here.

[0096] The difference between the high-speed germanium-silicon photodiode 200 and the high-speed germanium-silicon photodiode 100 is that a protective layer 210b is also provided around the silicon lens 270.

[0097] In one example, alternatively, the protective layer 210b is made of the same or similar silicon material as wafer 210a, preferably both the protective layer 210b and wafer 210a are made of high-resistivity silicon. The protective layer 210b is disposed on a first plane of wafer 210a around the silicon lens 270.

[0098] In one example, preferably, the height of the protective layer 210b is equal to the height of the silicon lens 270. The protective layer 210b protects the silicon lens 270 on the wafer 210a. It also facilitates the bonding and molding of the dicing film during the dicing process, and makes subsequent packaging and transportation of the finished product easier, thus improving the process stability and yield of the high-speed germanium-silicon photodiode 200.

[0099] To obtain the high-speed germanium-silicon photodiode of the present invention, embodiments of the present invention also provide manufacturing methods for the high-speed germanium-silicon photodiode 100 and high-speed germanium-silicon photodiode 200 described in the above embodiments, and the specific steps and processes of the manufacturing method are specifically illustrated through Embodiments 1 and 2. Embodiments 1 and 2 are both described using the manufacturing of the high-speed germanium-silicon photodiode 100 as an example.

[0100] Example 1

[0101] See Figure 4The diagram illustrates the process steps of a manufacturing method for a high-speed germanium-silicon photodiode 100 according to Example 1. The process steps specifically include:

[0102] Step S110: Provide wafer 110.

[0103] Step S120: A germanium absorption layer 120, a first electrode 131, a second electrode 132 and a passivation layer 140 are sequentially fabricated on one side of the second plane of the wafer 110.

[0104] In one example, such as Figure 1 As shown, preferably, the germanium absorption layer 120 and the first electrode 131 are formed on the second plane of the wafer 110, the second electrode 132 is formed on the photosensitive surface of the germanium absorption layer 120 and completely covers its photosensitive surface, and the passivation layer 140 is formed on the second plane of the wafer 110 and covers and encapsulates the germanium absorption layer 120, the first electrode 131 and the second electrode 132.

[0105] Step S130: Fabricate metal bump structures, namely the first metal bump structure 161 and the second metal bump structure 162.

[0106] See Figure 5 The diagram shows the cross-sectional structure obtained after steps S110-S130, with the wafer 110 at the bottom and the germanium absorption layer 120 at the top.

[0107] In one example, specifically, after exposing a portion of the first electrode 131 and the second electrode 132 by opening holes at preset positions on the passivation layer 140 (the size and distance of the two openings corresponding to the anode and cathode need to be specifically set according to the substrate structure when the actual inverted package is packaged), a first metal bump structure 161 corresponding to the first electrode 131 and a second metal bump structure 162 corresponding to the second electrode 132 are formed on the outside of the passivation layer 140 by metal connection and metal epitaxial growth.

[0108] In one example, after exposing a portion of the first electrode 131 and the second electrode 132 through openings in the passivation layer 140, alternatively, a first metal connection post 151 and a second metal connection post 152 are grown on the first electrode 131 and the second electrode 132, respectively. Then, nickel-palladium-gold or silver-tin solder is grown on the first metal connection post 151 and the second metal connection post 152, respectively. The nickel-palladium-gold or silver-tin solder is reflowed at high temperature to form a first metal bump structure 161 and a second metal bump structure 162. This example is merely illustrative and should not be construed as a limitation of the invention by those skilled in the art.

[0109] Step S140: As Figure 6As shown, the first bonding wafer 401 is bonded to the outside of the passivation layer 140 by the first bonding adhesive 301 and then flipped upside down.

[0110] Step S150: As Figure 7 As shown, a silicon lens 170 is formed on the first plane of the wafer 110, and the center of the silicon lens 170 is aligned with the center of the germanium absorption layer 120.

[0111] In one example, specifically taking a wafer 110 using a high-resistivity silicon material, one side of the first plane of the high-resistivity silicon wafer 110 is thinned to a suitable thickness, and then the developed photoresist is thermally melted after exposure to photoresist to form a raised lens structure. Then, a silicon lens 170 is formed by etching on the basis of the lens structure.

[0112] In one example, alternatively, the final thickness of wafer 110, the aperture of silicon lens 170, and the radius of curvature of silicon lens 170 need to be specifically optimized according to the performance requirements of the actual high-speed photodiode. This example is merely illustrative and should not be construed as a limitation of the invention by those skilled in the art.

[0113] Step S160: Remove the first bonding wafer 401 and the first bonding adhesive 301 to obtain the following: Figure 1 The high-speed germanium-silicon photodiode 100 shown is illustrated.

[0114] Example 2

[0115] See Figure 8 The diagram illustrates the process steps of a manufacturing method for a high-speed germanium-silicon photodiode 100 according to Example 2. These process steps specifically include:

[0116] Step S210: Provide wafer 110.

[0117] Step S220: As Figure 9 As shown, a germanium absorption layer 120, a first electrode 131, a second electrode 132, and a passivation layer 140 are sequentially fabricated on one side of the second plane of wafer 110. The specific fabrication process and procedures can be found in Example 1, and will not be repeated here. At this point, wafer 110 is at the bottom, and the germanium absorption layer 120 is at the top.

[0118] Step S230: As Figure 10 As shown, the second bonding wafer 402 is bonded to the outside of the passivation layer 140 by the second bonding adhesive 302 and then flipped upside down.

[0119] Step S240: As Figure 11 As shown, a silicon lens 170 is formed on the first plane of the wafer 110, and the center of the silicon lens 170 is aligned with the center of the germanium absorption layer 120.

[0120] Step S250: As Figure 12 As shown, after bonding the third bonding wafer 403 to the outside of the silicon lens 170 with the third bonding adhesive 303 and removing the second bonding wafer 402 and the second bonding adhesive 302, a metal bump structure is manufactured, namely the first metal bump structure 161 and the second metal bump structure 162.

[0121] Step S260: Remove the third bonding wafer 403 and the third bonding adhesive 303 to obtain the following: Figure 1 The high-speed germanium-silicon photodiode 100 shown is illustrated.

[0122] The processes, procedures and parameters that are the same as or similar to those in Example 1 can be referred to the description of Example 1, and will not be repeated here.

[0123] The high-speed germanium-silicon photodiode and its manufacturing method provided by the embodiments of the present invention have at least one or a portion of the following advantages:

[0124] (1) By setting the silicon lens and the germanium absorption layer on opposite surfaces of the wafer, the wafer can be used to increase the optical path and converge the incident light. On the other hand, the metal electrode covering the photosensitive surface of the germanium absorption layer can be used to reflect the incident light that was not absorbed when it first passed through the germanium absorption layer back to the germanium absorption layer and be absorbed again.

[0125] (2) By covering the outside of the photosensitive surface of the germanium absorption layer with the second electrode, the smooth metal surface of the second electrode can be used to reflect the incident light. The reflected light can pass through the photosensitive surface again and enter the germanium absorption layer to be absorbed, thereby reducing incident light loss and improving the photodiode responsivity.

[0126] (3) By placing the silicon lens on the opposite side of the germanium absorption layer on the wafer, the optical path of the incident light can be further increased, which helps to further increase the equivalent aperture and further improve the responsivity of the photodiode while ensuring high operating bandwidth.

[0127] (4) By forming a metal bump structure on the first and second electrodes to match the inverted package and directly solder it to the transimpedance amplifier or substrate, silicon through-hole is effectively avoided, the signal transmission path is shortened, and parasitic capacitance and parasitic inductance caused by the package are reduced.

[0128] (5) By setting a wafer protective layer of the same height around the silicon lens, the silicon lens can be effectively protected on the one hand, and the dicing process can be facilitated on the other hand to ensure the stability of the subsequent packaging and transportation process and the product quality.

[0129] (6) Functional layers are fabricated on opposite surfaces of a wafer by using bonding adhesive and bonding wafer respectively. The process is simple and the yield is high.

[0130] While some embodiments of the present general inventive concept have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A high-speed germanium-silicon photodiode, characterized in that, The high-speed germanium-silicon photodiode includes: wafers; A silicon lens is disposed on a first plane of the wafer; A germanium absorption layer is disposed on a second plane of the wafer opposite to the first plane, and the center of the germanium absorption layer is aligned with the center of the silicon lens. The side of the germanium absorption layer opposite to the second plane is the photosensitive side. The first electrode is disposed on the second plane of the wafer; The second electrode is disposed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface. A passivation layer is disposed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode; The incident light is focused by the silicon lens onto the wafer and then enters the germanium absorption layer where it is absorbed. The unabsorbed incident light continues to pass through the germanium absorption layer and the passivation layer in sequence, and after reaching the second electrode, it is reflected back to the germanium absorption layer where it is absorbed again. The germanium absorber layer comprises a germanium structure, an amorphous silicon layer, and an antireflection film arranged sequentially in a direction away from the wafer. The germanium structure is disposed on the first ion-doped layer of the wafer, and the side of the germanium structure in contact with the first ion-doped layer is a light-absorbing surface. The amorphous silicon layer is disposed on the germanium structure, with its side opposite to the germanium structure serving as a photosensitive surface. The amorphous silicon layer further includes a second ion-doped layer disposed on the photosensitive surface, and the second electrode is in electrical contact with the second ion-doped layer. The antireflective film is disposed on the photosensitive surface of the amorphous silicon layer, and the material of the antireflective film is any one of silicon dioxide, aluminum oxide, titanium oxide, magnesium fluoride, and graphene.

2. The high-speed germanium-silicon photodiode according to claim 1, characterized in that, The first ion-doped layer is disposed on the second plane of the wafer, and the germanium absorption layer and the first electrode are in electrical contact with the first ion-doped layer.

3. The high-speed germanium-silicon photodiode according to claim 2, characterized in that, When the first ion-doped layer is P-type ion implanted, the second ion-doped layer is N-type ion implanted; or When the first ion doping layer is N-type ion implanted, the second ion doping layer is P-type ion implanted.

4. The high-speed germanium-silicon photodiode according to claim 3, characterized in that, The passivation layer is made of silicon dioxide or silicon nitride.

5. The high-speed germanium-silicon photodiode according to claim 4, characterized in that, The high-speed germanium-silicon photodiode also includes a metal bump structure for inverted packaging, the metal bump structure being exposed on the outside of the passivation layer for soldering to a transimpedance amplifier or substrate, wherein... The metal bump structure includes a first metal bump structure connected to the first electrode and a second metal bump structure connected to the second electrode.

6. The high-speed germanium-silicon photodiode according to claim 5, characterized in that, The high-speed germanium-silicon photodiode also includes a protective layer disposed on a first plane of the wafer around the silicon lens, the height of the protective layer being equal to the height of the silicon lens.

7. A method for manufacturing a high-speed germanium-silicon photodiode, used to manufacture a high-speed germanium-silicon photodiode according to any one of claims 1-6, characterized in that, The manufacturing method includes: Provide wafers; A germanium absorption layer, a first electrode, a second electrode, and a passivation layer are sequentially fabricated, wherein the germanium absorption layer and the first electrode are formed on a second plane of the wafer, the second electrode is formed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface, and the passivation layer is formed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode; After exposing the first electrode and the second electrode through openings in the passivation layer, a first metal bump structure corresponding to the first electrode and a second metal bump structure corresponding to the second electrode are formed on the outside of the passivation layer by metal connection and metal epitaxial growth. After the first bonding wafer is bonded to the outside of the passivation layer using the first bonding adhesive, it is flipped and inverted. A silicon lens is formed on a first plane of the wafer, the center of the silicon lens being aligned with the center of the germanium absorption layer; The high-speed germanium-silicon photodiode is obtained by removing the first bonding wafer and the first bonding adhesive.

8. A method for manufacturing a high-speed germanium-silicon photodiode, used to manufacture a high-speed germanium-silicon photodiode according to any one of claims 1-6, characterized in that, The manufacturing method includes: Provide wafers; A germanium absorption layer, a first electrode, a second electrode, and a passivation layer are sequentially fabricated, wherein the germanium absorption layer and the first electrode are formed on a second plane of the wafer, the second electrode is formed on the photosensitive surface of the germanium absorption layer and completely covers the photosensitive surface, and the passivation layer is formed on the second plane of the wafer and covers and encapsulates the germanium absorption layer, the first electrode, and the second electrode; After the second bonding wafer is bonded to the outside of the passivation layer using a second bonding adhesive, it is flipped over and inverted. A silicon lens is formed on a first plane of the wafer, the center of the silicon lens being aligned with the center of the germanium absorption layer; The third bonding wafer is bonded to the outside of the silicon lens using a third bonding adhesive, and the second bonding wafer and the second bonding adhesive are removed. After exposing the first electrode and the second electrode through openings in the passivation layer, a first metal bump structure corresponding to the first electrode and a second metal bump structure corresponding to the second electrode are formed on the outside of the passivation layer by metal connection and metal epitaxial growth. The high-speed germanium-silicon photodiode is obtained by removing the third bonding wafer and the third bonding adhesive.

9. The manufacturing method according to claim 7 or 8, characterized in that, After exposing the first and second electrodes through openings in the passivation layer, the steps for fabricating the metal bump structure specifically include: A first metal connecting post and a second metal connecting post are grown on the first electrode and the second electrode, respectively; Nickel-palladium-gold or silver-tin solder is grown on the first metal connecting post and the second metal connecting post, respectively; The nickel-palladium-gold or silver-tin solder is reflowed at high temperature to form the first metal bump structure and the second metal bump structure.

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