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CN-122002967-A - Flip-chip photodiode and manufacturing method thereof

CN122002967ACN 122002967 ACN122002967 ACN 122002967ACN-122002967-A

Abstract

The invention relates to the technical field of chip manufacturing, in particular to a flip-chip photodiode and a manufacturing method thereof, wherein the flip-chip photodiode comprises an epitaxial wafer, a reflecting layer and a lens layer, and a P electrode and an N electrode are arranged on the epitaxial wafer; the lens layer receives the optical signal from the laser, the epitaxial wafer absorbs the optical signal to generate an electric signal, the electric signal is transmitted through the P electrode and the N electrode, the reflecting layer reflects the optical signal to enable the epitaxial wafer to absorb the optical signal repeatedly, the optical signal enters from the back of the photodiode through corrosion of the lens layer on the back of the epitaxial wafer, the problem of coupling of the photodiode with the laser due to back light entering is solved, on the other hand, the reflecting layer is arranged on the front of the photodiode, after the optical signal transmitted from the lens layer is absorbed by the epitaxial wafer, the residual optical signal can be reflected by the reflecting layer to be absorbed continuously, the thickness of the absorbing layer in the epitaxial wafer is reduced, and the response speed is improved under the condition that the responsivity of the photodiode is not affected.

Inventors

  • HUO PANJIE
  • HU YAN

Assignees

  • 武汉光迅科技股份有限公司

Dates

Publication Date
20260508
Application Date
20241104

Claims (10)

  1. 1. The flip-chip photodiode is characterized by comprising an epitaxial wafer (1), a reflecting layer (2) and a lens layer (3), wherein the reflecting layer (2) is arranged above the epitaxial wafer (1), and the lens layer (3) is arranged at the bottom of the epitaxial wafer (1); The lens layer (3) is used for being coupled with a laser, the lens layer (3) is used for receiving an optical signal from the laser, the epitaxial wafer (1) is used for absorbing the optical signal to generate an electric signal and transmitting the electric signal through the P electrode and the N electrode, and the reflecting layer (2) is used for reflecting the optical signal so that the epitaxial wafer (1) repeatedly absorbs the optical signal.
  2. 2. Flip-chip photodiode according to claim 1, characterized in that the epitaxial wafer (1) comprises a substrate layer (10), a buffer layer (11), an absorption layer (12), a cap layer (13) and a contact layer (14) which are arranged in sequence, wherein the contact layer (14) covers part of the cap layer (13); The protective cover is characterized in that an insulating layer (4) is further arranged on the cap layer (13), the lens layer (3) is arranged at the bottom of the substrate layer (10), one part of the reflecting layer (2) is arranged on the insulating layer (4), and the other part of the reflecting layer (2) is arranged on the cap layer (13).
  3. 3. The flip-chip photodiode according to claim 2, characterized in that a first opening is formed in the insulating layer (4), and a part of the cap layer (13), a part of the absorption layer (12) and a part of the buffer layer (11) are etched in sequence through the first opening to obtain an etched hole (5), wherein the insulating layer (4) is arranged on the outer ring of the etched hole (5) and on the surface of the cap layer (13), and the etched hole (5) is cut off from the buffer layer (11); an N metal contact layer (6) is arranged on the corrosion hole (5), and the N metal contact layer (6) and the corrosion hole (5) form ohmic contact so as to obtain the N electrode.
  4. 4. Flip-chip photodiode according to claim 2, characterized in that a second opening is formed in the insulating layer (4), the contact layer (14) being arranged on the cap layer (13) corresponding to the second opening, the diffusion material being diffused from the second opening towards part of the cap layer (13) to form diffusion holes (7); And a P metal contact layer (8) is further arranged on the contact layer (14), and the P metal contact layer (8), the contact layer (14) and the diffusion holes (7) form ohmic contact so as to obtain the P electrode.
  5. 5. Flip-chip photodiode according to claim 2, characterized in that the contact layer (14) is a contact ring, and that the other part of the reflective layer (2) is arranged in an inner ring of the contact layer (14) and in the same plane as the contact ring.
  6. 6. The flip-chip photodiode of claim 1 wherein the material of the P-electrode and the N-electrode is one or more of Ti, pt, and Au.
  7. 7. A method of fabricating a flip-chip photodiode, wherein the method of fabricating is used to fabricate a flip-chip photodiode as claimed in any one of claims 1-6, comprising: Manufacturing an epitaxial wafer (1), manufacturing a reflecting layer (2) above the epitaxial wafer (1), and manufacturing a lens layer (3) at the bottom of the epitaxial wafer (1); Manufacturing a P electrode and an N electrode on the epitaxial wafer (1); The lens layer (3) is used for being coupled with a laser, the lens layer (3) is used for receiving an optical signal from the laser, the epitaxial wafer (1) is used for absorbing the optical signal to generate an electric signal and transmitting the electric signal through the P electrode and the N electrode, and the reflecting layer (2) is used for reflecting the optical signal so that the epitaxial wafer (1) repeatedly absorbs the optical signal.
  8. 8. The method of fabricating a flip-chip photodiode according to claim 7, wherein fabricating the epitaxial wafer (1) and fabricating the reflective layer (2) over the epitaxial wafer (1) and fabricating the lens layer (3) on the bottom of the epitaxial wafer (1) comprises: Sequentially growing a buffer layer (11), an absorption layer (12), a cap layer (13) and a contact layer (14) on a substrate layer (10) to obtain the epitaxial wafer (1); Manufacturing an insulating layer (4) on the cap layer (13), and arranging the reflecting layer (2) on the insulating layer (4); Etching out lenses at the bottom of the substrate layer (10) to obtain the lens layer (3).
  9. 9. The method of fabricating a flip-chip photodiode according to claim 8, wherein fabricating P-electrodes and N-electrodes on the epitaxial wafer (1) comprises: Forming a first opening on the insulating layer (4), and sequentially corroding part of the cap layer (13), part of the absorption layer (12) and part of the buffer layer (11) through the first opening to obtain corrosion holes (5) so as to form an N-type contact layer; Forming a second opening on the insulating layer (4), and diffusing a diffusion material from the second opening to part of the cap layer (13) to form a diffusion hole (7) so as to form a P-type contact layer; Depositing a reflecting layer (2) on the insulating layer (4), the first opening and the second opening; Removing the reflecting layer (2) at the first opening to expose the N-type contact layer, and removing part of the reflecting layer (2) at the second opening to expose the P-type contact layer; And forming an N metal contact layer (6) on the area corresponding to the first opening, and forming a P metal contact layer (8) on the area corresponding to the second opening so as to obtain the P electrode and the N electrode respectively.
  10. 10. The method of fabricating a flip-chip photodiode according to claim 8, wherein fabricating P-electrodes and N-electrodes on the epitaxial wafer (1) further comprises: Forming a second opening on the insulating layer (4), and diffusing a diffusion material from the second opening to part of the cap layer (13) to form a diffusion hole (7) so as to form a P-type contact layer; depositing a reflecting layer (2) on the insulating layer (4) and the area corresponding to the second opening; Removing part of the reflecting layer (2) at the second opening to expose the P-type contact layer; forming a P metal contact layer (8) in the region corresponding to the second opening to obtain the P electrode; And an N metal contact layer (6) is arranged at the bottom of the substrate layer (10) at a position avoiding the lens layer (3) so as to obtain the N electrode.

Description

Flip-chip photodiode and manufacturing method thereof Technical Field The invention relates to the technical field of chip manufacturing, in particular to a flip photodiode and a manufacturing method thereof. Background Currently, in long-distance optical fiber communication, dispersion loss and chirp phenomenon have become important factors restricting technical development, so that an electroabsorption modulated laser (Electlro-absorption Modulated Laser, abbreviated as EML) is receiving attention, and different from the traditional TO, a horizontal patch is required between a photodiode for backlight detection and the EML, so that the EML is monitored mainly by using Side-illuminated ESPD (english: edge-Side-Ported Diode). With the development of 400G, 800G and higher, EML made of lithium niobate as a photoelectric material has been rapidly developed, and this type of EML cannot be monitored by using ESPD with side-view. Currently, this type of EML is monitored using a front side light entry monitor photodiode (Monitor Photo Diode, abbreviated MPD). In order to maintain the responsivity R, the absorption layer of the MPD is thicker, the photosensitive surface is larger, and the f 3db is only about 500M because of the vertical incidence of light and inconsistent light paths, so that the speed of 1-2G is difficult to realize, therefore, the conventional photodiode cannot meet the requirement of monitoring the light path of a high-speed modulation laser. In view of this, overcoming the drawbacks of the prior art is a problem to be solved in the art. Disclosure of Invention The invention aims to solve the technical problem of low responsivity of the existing front-side light-entering photodiode. The invention adopts the following technical scheme: in a first aspect, a flip-chip photodiode is provided, comprising an epitaxial wafer 1, a reflecting layer 2 and a lens layer 3, wherein the reflecting layer 2 is arranged above the epitaxial wafer 1, and the lens layer 3 is arranged at the bottom of the epitaxial wafer 1; The lens layer 3 is used for coupling with a laser, the lens layer 3 is used for receiving an optical signal from the laser, the epitaxial wafer 1 is used for absorbing the optical signal to generate an electric signal and transmitting the electric signal through the P electrode and the N electrode, and the reflecting layer 2 is used for reflecting the optical signal so that the epitaxial wafer 1 repeatedly absorbs the optical signal. Preferably, the epitaxial wafer 1 includes a substrate layer 10, a buffer layer 11, an absorption layer 12, a cap layer 13, and a contact layer 14, which are sequentially stacked, wherein the contact layer 14 covers a part of the cap layer 13; The cap layer 13 is further provided with an insulating layer 4, the lens layer 3 is arranged at the bottom of the substrate layer 10, one part of the reflecting layer 2 is arranged on the insulating layer 4, and the other part of the reflecting layer 2 is arranged on the cap layer 13. Preferably, a first opening is formed on the insulating layer 4, and part of the cap layer 13, part of the absorption layer 12 and part of the buffer layer 11 are sequentially corroded through the first opening to obtain corrosion holes 5, wherein the insulating layer 4 is arranged on the outer ring of the corrosion holes 5 and positioned on the surface of the cap layer 13, and the corrosion holes 5 are cut off from the buffer layer 11; An N metal contact layer 6 is disposed on the etching hole 5, and the N metal contact layer 6 and the etching hole 5 form ohmic contact to obtain the N electrode. Preferably, a second opening is formed on the insulating layer 4, and the contact layer 14 is arranged on the cap layer 13 corresponding to the second opening, and diffusion is carried out from the second opening to part of the cap layer 13 through a diffusion material so as to form diffusion holes 7; And a P metal contact layer 8 is further arranged on the contact layer 14, and the P metal contact layer 8, the contact layer 14 and the diffusion holes 7 form ohmic contact so as to obtain the P electrode. Preferably, the contact layer 14 is a contact ring, and the other part of the reflective layer 2 is disposed in the inner ring of the contact layer 14 and is in the same plane as the contact ring. Preferably, the materials of the P electrode and the N electrode are one or more of Ti, pt and Au. In a second aspect, a method for fabricating a flip-chip photodiode according to the first aspect is provided, including: Manufacturing an epitaxial wafer 1, manufacturing a reflecting layer 2 above the epitaxial wafer 1, and manufacturing a lens layer 3 at the bottom of the epitaxial wafer 1; manufacturing a P electrode and an N electrode on the epitaxial wafer 1; The lens layer 3 is used for coupling with a laser, the lens layer 3 is used for receiving an optical signal from the laser, the epitaxial wafer 1 is used for absorbing the optical signal to generate a