Optical module
By setting stress-relieving grooves on the optical semiconductor chip and connecting them to electrodes, the stress problem during the electrical bonding of the chip and the subcarrier is alleviated, the laser oscillation wavelength shift and characteristic changes are solved, and the stability and high-frequency characteristics of the optical module are improved.
Patent Information
- Application Number
- CN202380099281.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-14
- Publication Date
- 2026-01-13
AI Technical Summary
When existing optical modules are electrically bonded to the chip and the subcarrier, the stress caused by the high-temperature bonding may lead to changes in chip characteristics, such as laser oscillation wavelength shift.
First and second stress-relieving grooves are disposed on the optical semiconductor chip, respectively, along the optical waveguide, and the electrode junction is connected to p-type and n-type electrodes. The stress-relieving grooves are deeper than the core of the optical waveguide to alleviate stress transmission.
It effectively suppresses characteristic variations during the electrical bonding of the chip and the subcarrier, especially the shift in laser oscillation wavelength, improves wavelength stability and high-frequency characteristics, and reduces the risk of breakage at the electrode joint.
Smart Images
Figure CN121336331A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an optical module. BACKGROUND
[0002] In Non-Patent Literature 1, a chip of a distributed feedback type (DFB) laser in which p-type and n-type electrodes are arranged on a surface of the chip is disclosed. The chip is mounted on a submount in a flip-chip manner, and a bottom-filling material is caused to flow into a gap between the submount and the chip to fix the chip, thereby forming an optical module. The bottom-filling material suppresses breakage of an electrode joint portion caused by stress due to a difference in thermal expansion coefficient between the chip and the submount.
[0003] Prior Art Documents
[0004] Non-Patent Literature
[0005] Non-Patent Literature 1: A. Marinins et. al., "Wafer-Scale Hybrid Integration of InP DFB Lasers on Si Photonics by Flip-Chip Bonding With sub-300nm Alignment Precision," J of Sel. In Quantum Electronics, vol. 29, no. 3, 8200311. SUMMARY
[0006] Problem to be Solved by the Invention
[0007] According to the optical module described in Non-Patent Literature 1, in order to electrically join the chip and the submount, a joining method such as soldering, conductive adhesive, ultrasonic joining, or the like is used. In these joining methods, joining is performed at a high temperature, and then the temperature is returned to room temperature, whereby the joint portion between the chip and the submount shrinks and stress can be generated. Due to the stress generated in the joint portion, there is a problem in that characteristics of the chip can change, such as a shift in the oscillation wavelength of the laser.
[0008] The present disclosure was made in view of the above problem. An object of the present invention is to provide an optical module in which a change in characteristics of a chip when the chip is electrically joined with a submount is suppressed.
[0009] Means for Solving the Problem
[0010] To solve the above-described problems, an optical module of one embodiment of the present disclosure includes a light semiconductor chip, a submount, and an electrode bonding portion that electrically connects the light semiconductor chip and the submount. The light semiconductor chip includes a light waveguide, a first stress relaxation groove and a second stress relaxation groove that are arranged along the light waveguide so as to be apart from the light waveguide when viewed from above the light semiconductor chip, and a p-type electrode and an n-type electrode that are arranged apart from the first stress relaxation groove and the second stress relaxation groove. The electrode bonding portion is connected to the p-type electrode and the n-type electrode, and the first stress relaxation groove and the second stress relaxation groove are deeper than a core portion of the light waveguide.
[0011] Effects of Invention
[0012] According to the present disclosure, an optical module in which variation in characteristics of a chip when the chip is electrically bonded to a submount is suppressed can be provided. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1 is a top view of a light semiconductor chip included in an optical module of the first embodiment of the present disclosure.
[0014] Figure 2 is a cross-sectional view taken along line A-A of the light semiconductor chip of Figure 1
[0015] Figure 3 is a configuration view of an electrode bonding portion with respect to the light semiconductor chip of Figure 1
[0016] Figure 4 is a side view of an optical module of the first embodiment of the present disclosure. The optical module includes a light semiconductor chip 10, a submount 20, and an electrode bonding portion.
[0017] Figure 5 is a top view of a light semiconductor chip included in an optical module of the second embodiment of the present disclosure. DETAILED DESCRIPTION
[0018] Embodiments of the present disclosure are described in detail below with reference to the drawings. In the description, the same portions are marked with the same reference numerals in different drawings and repetitive description is omitted.
[0019] [Explanation of the First Embodiment]
[0020] Figure 1 is a top view of a light semiconductor chip included in an optical module of the first embodiment of the present disclosure. Figure 2 is a cross-sectional view taken along line A-A of the light semiconductor chip of Figure 1 Figure 3 is a configuration view of an electrode bonding portion with respect to the light semiconductor chip of Figure 1 Figure 4 is a side view of an optical module of the first embodiment of the present disclosure. The optical module includes a light semiconductor chip 10, a submount 20, and an electrode bonding portion.
[0021] The optical semiconductor chip 10 is at least one of a direct-modulation DFB laser chip and an electric field absorption type optical modulator integrated laser chip. For example, the optical semiconductor chip 10 is a chip fabricated on an indium phosphide (InP) substrate. The light output from the optical semiconductor chip 10 (output light R1) is guided into an optical wave loop (not shown). The optical semiconductor chip 10 is not limited to the examples given herein.
[0022] Subcarrier 20 has built-in wiring for supplying power to the optical semiconductor chip 10, or for transmitting signals from the optical semiconductor chip 10. For example, subcarrier 20 is a subcarrier with aluminum nitride as the substrate and gold as the wiring pattern. Subcarrier 20 is not limited to the examples given herein.
[0023] Furthermore, the coefficient of thermal expansion of the subcarrier 20 can be made equal to that of the optical semiconductor chip 10. This can suppress the breakage of the electrode junction caused by stress resulting from the difference in the coefficients of thermal expansion between the optical semiconductor chip 10 and the subcarrier 20.
[0024] like Figure 1 and Figure 2 As shown, the optical semiconductor chip 10 includes an optical waveguide WG, a stress-relieving groove TP2 (first stress-relieving groove), a stress-relieving groove TN2 (second stress-relieving groove), p-type electrodes EP1 and EP2, and n-type electrodes EN1 and EN2. Here, the stress-relieving grooves TP2 and TN2 are arranged along the optical waveguide WG, separated from it when viewed from above. Figure 1 In the design, stress-relieving grooves TP2 and TN2 are configured along the direction of the optical waveguide WG. Stress-relieving groove TP2 can also function as the groove for leading out the p-type electrode EP2. Stress-relieving groove TN2 can also function as the groove for leading out the n-type electrode EN2.
[0025] The p-type electrode EP2 is disposed on the upper surface of the optical semiconductor chip 10, opposite to the optical waveguide WG, separated by a stress-relieving groove TP2. Similarly, the n-type electrode EN2 is disposed on the upper surface of the optical semiconductor chip 10, opposite to the optical waveguide WG, separated by a stress-relieving groove TN2.
[0026] like Figure 2 As shown, in the cross-section of the optical semiconductor chip 10 perpendicular to the extension direction of the optical waveguide WG, the components are arranged in the following order: n-type electrode EN2, stress relief groove TN2, optical waveguide WG, stress relief groove TP2, and p-type electrode EP2. Furthermore, the optical waveguide WG has a core CR, with a semi-insulating semiconductor SR embedded on both sides of the core CR.
[0027] p-type electrodes EP1 and EP2, and n-type electrodes EN1 and EN2 are electrically connected to the wiring built into the subcarrier 20 via electrode joints. Here, the electrode joints are at least one of solder, conductive adhesive, and metal.
[0028] For example, a conductive adhesive is applied to the electrodes of the optical semiconductor chip 10, and the optical semiconductor chip 10 is mounted on the subcarrier 20 in a flip-chip manner. The p-type electrodes EP1, EP2 and the n-type electrodes EN1, EN2 are electrically connected to the wiring built into the subcarrier 20. In addition to conductive adhesives, solder, metal, or ultrasonic bonding can also be used to obtain electrical connections.
[0029] Furthermore, the stress relief grooves TP2 and TN2 are formed deeper than the core CR of the optical waveguide WG. In addition, compared with the laser section (not shown) of the optical semiconductor chip 10, the stress relief grooves TP2 and TN2 are formed longer along the extension direction of the optical waveguide WG.
[0030] To confirm the effect of setting stress-relieving grooves TP2 and TN2, as a comparative example, a light semiconductor chip 10 without stress-relieving grooves TP2 and TN2 was prepared. Then, Figure 1 , 2 The optical semiconductor chip 10 shown is compared with a comparative example.
[0031] Furthermore, as a condition for comparison, the optical semiconductor chip 10 is an electric field absorption type optical modulator integrated laser chip, which is a chip fabricated on an InP substrate. Additionally, the subcarrier 20 uses aluminum nitride as its substrate. Furthermore, gold-tin solder is used as the electrode bonding portion.
[0032] The optical semiconductor chip 10 is mounted such that the upper surface of the electrode-equipped part of the chip is in contact with the wiring side of the subcarrier 20. The chip is heated to 320 degrees Celsius, which is above the melting point of the gold solder, and held for about 30 seconds. The chip is then cooled to room temperature, thereby assembling the optical module.
[0033] for Figure 1 and Figure 2 The optical semiconductor chip 10 shown, when measuring the oscillation wavelength before mounting the substrate 20, at a chip temperature of 25°C and a laser current of 100mA, exhibited an oscillation wavelength of 1308.1nm. Furthermore, when measuring the oscillation wavelength after mounting the substrate 20, under the same operating conditions, the oscillation wavelength was 1308.3nm. That is, the deviation in oscillation wavelength is 0.2nm.
[0034] On the other hand, for the comparative example, when measuring the oscillation wavelength before the implanter 20 was installed, the oscillation wavelength was 1306.5 nm at a chip temperature of 25°C and a laser current of 100 mA. Furthermore, when measuring the oscillation wavelength after the implanter 20 was installed, under the same operating conditions, the oscillation wavelength was 1305.0 nm. That is, the deviation in oscillation wavelength is 1.5 nm.
[0035] Based on the above results, it can be confirmed that, compared with the optical semiconductor chip of the comparative example, the optical semiconductor chip and optical module according to this embodiment can suppress the variation of oscillation wavelength caused by stress.
[0036] [Description of the Second Embodiment]
[0037] Figure 5 This is a top view of the optical semiconductor chip included in the optical module according to the second embodiment of this disclosure. Figure 1 In contrast, the optical semiconductor chip in the optical module of this embodiment also includes a stress-relieving groove TP1 (first stress-relieving groove) and a stress-relieving groove TN1 (second stress-relieving groove). The stress-relieving groove TP1 can also function as the groove for leading out the p-type electrode EP1. The stress-relieving groove TN1 can also function as the groove for leading out the n-type electrode EN1.
[0038] To confirm the effectiveness of setting stress-relieving grooves TP1 and TN1, as a comparative example, an optical semiconductor chip without stress-relieving grooves TP1 and TN1 was prepared. Then, Figure 5 The optical semiconductor chip 10 shown is compared with a comparative example.
[0039] Furthermore, as a condition for comparison, the optical semiconductor chip 10 is an electric field absorption type optical modulator integrated laser chip, which is a chip fabricated on an InP substrate. Additionally, the subcarrier 20 uses aluminum nitride as its substrate. Furthermore, gold bumps and a conductive adhesive are used as electrode bonding portions.
[0040] After applying a conductive adhesive to the wiring surface of the subcarrier 20, the optical semiconductor chip 10 is mounted so that the upper surface of the chip, on which electrodes are disposed, contacts the wiring side surface of the subcarrier 20. Then, after maintaining the conductive adhesive at its curing temperature of 150 degrees Celsius for about 20 minutes, it is cooled, thereby assembling the optical module.
[0041] for Figure 5 The optical semiconductor chip 10 shown, when measuring the oscillation wavelength before mounting the substrate 20, at a chip temperature of 25 degrees Celsius and a laser current of 120 mA, exhibited an oscillation wavelength of 1550.4 nm. Furthermore, when measuring the oscillation wavelength after mounting the substrate 20, under the same operating conditions, the oscillation wavelength was 1550.7 nm. That is, the deviation in oscillation wavelength is 0.3 nm.
[0042] On the other hand, regarding the comparative example, when measuring the oscillation wavelength before the implanter 20 was installed, at a chip temperature of 25°C and a laser current of 120 mA, the oscillation wavelength was 1545.5 nm. Furthermore, when measuring the oscillation wavelength after the implanter 20 was installed, under the same operating conditions, the oscillation wavelength was 1546.9 nm. That is, the deviation in oscillation wavelength was 1.4 nm.
[0043] Based on the above results, it can be confirmed that, compared with the optical semiconductor chip of the comparative example, the optical semiconductor chip and optical module according to this embodiment can suppress the variation of oscillation wavelength caused by stress.
[0044] The extinction characteristics of the EA modulator of the optical semiconductor chip 10, which is an integrated laser chip for electric field absorption optical modulator, were measured.
[0045] for Figure 5 The optical semiconductor chip 10 shown, before being installed on the subcarrier 20, at a chip temperature of 25 degrees Celsius and a laser current of 120 mA, showed a difference of 12.0 dB in optical output power when the bias voltage of the EA modulator was measured at 0 V and -2.5 V. After being installed on the subcarrier 20, under the same operating conditions, the difference in optical output power was 11.9 dB.
[0046] On the other hand, regarding the comparative example, in the stage before the subcarrier 20 is installed, at a chip temperature of 25 degrees Celsius and a laser current of 120 mA, the difference in optical output power was 13.0 dB when measuring the optical output power at bias voltages of 0 V and -2.5 V for the EA modulator. In the stage after the subcarrier 20 is installed, under the same operating conditions, the difference in optical output power was 14.0 dB.
[0047] Based on the above results, it can be confirmed that, compared with the optical semiconductor chip of the comparative example, the optical semiconductor chip and optical module according to this embodiment can suppress the changes in the extinction characteristics of the EA modulator caused by stress.
[0048] [Effects of the Implementation Method]
[0049] As detailed above, the optical module of this embodiment includes: an optical semiconductor chip, a subcarrier, and an electrode junction that electrically connects the optical semiconductor chip and the subcarrier. The optical semiconductor chip includes: an optical waveguide; a first stress-relieving groove and a second stress-relieving groove disposed along the optical waveguide in a manner that, when viewed from above, separates the optical semiconductor chip from the waveguide; a p-type electrode disposed on the upper surface of the optical semiconductor chip, on the opposite side of the optical waveguide separated by the first stress-relieving groove; and an n-type electrode disposed on the upper surface of the optical semiconductor chip, on the opposite side of the optical waveguide separated by the second stress-relieving groove. The electrode junction is connected to the p-type electrode and the n-type electrode, and the first stress-relieving groove and the second stress-relieving groove are each deeper than the core of the optical waveguide.
[0050] Therefore, an optical module can be provided that suppresses characteristic variations of the chip during electrical bonding with the subcarrier. Specifically, by making the first and second stress-relieving grooves deeper than the core of the optical waveguide, the transmission of stress generated at the electrode junction to the core of the optical waveguide can be suppressed. As a result, characteristic variations of the chip are suppressed.
[0051] Furthermore, in the optical module of this embodiment, the optical semiconductor chip may also include a laser section, with the first stress-relieving groove and the second stress-relieving groove being longer than the laser section. This suppresses the transmission of stress generated at the electrode junction to the laser section. Consequently, it suppresses the shift in the oscillation wavelength of the laser.
[0052] Furthermore, in the optical module of this embodiment, the optical semiconductor chip is at least one of a direct-modulation DFB laser chip and an electric field absorption type optical modulator integrated laser chip, thereby improving the high-frequency characteristics of the direct-modulation DFB laser chip and the electric field absorption type optical modulator integrated laser chip and increasing wavelength stability.
[0053] Furthermore, in the optical module of this embodiment, semi-insulating semiconductors can be embedded in both sides of the core. This insulates the core from the closely positioned p-type and n-type electrodes. As a result, variations in the core's characteristics can be suppressed.
[0054] Furthermore, in the optical module of this embodiment, the p-type electrode and the n-type electrode can be electrically connected to the wiring built into the subcarrier via an electrode bonding portion, which can be at least one of solder, conductive adhesive, or metal. This ensures the electrical connection between the electrodes of the optical semiconductor chip 10 and the wiring built into the subcarrier.
[0055] Furthermore, in the optical module of this embodiment, the coefficient of thermal expansion of the subcarrier can be made equal to that of the optical semiconductor chip. This suppresses stress caused by the difference in the coefficients of thermal expansion between the optical semiconductor chip and the subcarrier when the optical semiconductor chip is mounted on the subcarrier. As a result, breakage of the electrode joint between the optical semiconductor chip and the subcarrier is suppressed.
[0056] As described above, the present disclosure has been presented according to embodiments, but the present disclosure is not limited to these descriptions, and various modifications and alterations are possible, as will be apparent to those skilled in the art. The discussions and drawings that form part of this disclosure should not be construed as limiting the present disclosure. Based on this disclosure, those skilled in the art will recognize various alternative embodiments, examples, and techniques.
[0057] This disclosure naturally includes various embodiments not described herein. Therefore, based on the above description, the technical scope of this disclosure is determined only by the specific inventive matters covered by the appropriate patent protection scope.
[0058] Explanation of reference numerals in the attached figures
[0059] CR core
[0060] EN1, EN2 n-type electrodes
[0061] EP1, EP2 p-type electrodes
[0062] TP1, TP2, TN1, TN2 stress relief tanks
[0063] WG optical waveguide
[0064] 10 Optical Semiconductor Chips
[0065] 20 sub-carriers.
Claims
1. An optical module, comprising: Optical semiconductor chips; Sub-carrier; and An electrode junction electrically connects the optical semiconductor chip to the sub-carrier. Its features are, The optical semiconductor chip has the following features: Optical waveguide; The first stress relief groove and the second stress relief groove are arranged along the optical waveguide in such a way that they are separated from the optical waveguide when viewed from above the optical semiconductor chip; A p-type electrode is disposed on the opposite side of the optical waveguide, separated from the first stress-relieving groove, in the upper surface of the optical semiconductor chip. as well as An n-type electrode is disposed on the opposite side of the optical waveguide, separated from the optical semiconductor chip by the second stress-relieving groove. The electrode junction is connected to both the p-type electrode and the n-type electrode. The first stress relief groove and the second stress relief groove are both deeper than the core of the optical waveguide.
2. The optical module according to claim 1, characterized in that, The optical semiconductor chip also includes a laser unit. The first stress relief groove and the second stress relief groove are respectively longer than the laser.
3. The optical module according to claim 1, characterized in that, The optical semiconductor chip is at least one of a direct-modulation DFB laser chip and an electric field absorption type optical modulator integrated laser chip.
4. The optical module according to claim 1, characterized in that, The two sides of the core are embedded with semi-insulating semiconductors.
5. The optical module according to claim 1, characterized in that, The p-type electrode and the n-type electrode are electrically connected to the wiring built into the sub-carrier via the electrode junction. The electrode joint is at least one of solder, conductive adhesive, and metal.
6. The optical module according to any one of claims 1 to 5, characterized in that, The coefficient of thermal expansion of the subcarrier is equal to that of the optical semiconductor chip.