Rapid-heating wavelength-adjustable laser chip integrated with heat insulation pad and preparation method of rapid-heating wavelength-adjustable laser chip

Abstract

The invention discloses a rapid heating wavelength-adjustable laser chip integrated with a heat insulation pad and a preparation method, the rapid heating wavelength-adjustable laser chip comprises an epitaxial structure, a passivation layer, P-surface metal and N-surface metal, and the epitaxial structure comprises a substrate layer, a lower limiting layer, an active layer and an upper limiting layer from bottom to top in sequence; the active layer is set to be a passive area and an active area along the cavity length direction, a grating structure is arranged in the upper limiting layer, and the grating structure is arranged corresponding to the passive area and avoids the active area; the part, corresponding to the passive area, in the lower limiting layer is sacrificed to form a cavity, and a heat insulation material grows and is filled in the cavity to form a heat resistance cushion layer; and a ridge waveguide is formed on the front surface of the epitaxial structure. The heating efficiency of the chip is improved, the heating temperature can be accurately adjusted, and the overall structural strength of the chip is high.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor lasers, and in particular relates to a fast-heating wavelength-tunable laser chip with an integrated thermal insulation pad and a preparation method thereof. Background Art

[0002] Semiconductor lasers are widely used in many fields due to their small size, high efficiency and good reliability. The performance of this type of laser is closely related to its temperature, and using temperature changes to achieve wavelength tuning is one of the ways to use the heat of the laser chip.

[0003] At present, there are two main temperature control schemes for laser chips: one is to control the temperature of the device through TEC cooler and NTC thermistor, for example, patent CN115693356A discloses a laser, a laser temperature control method and a gas detection device, the thermistor material has temperature sensitivity, when the current passes through the thermistor, it will generate heat to heat the chip to the required temperature, this heating chip is often used in temperature control, temperature measurement and constant temperature heating and other applications; the other is to set a heating resistor on the heat sink or packaging structure, and control the chip temperature through the heating resistor and NTC, for example, patent CN118352882A discloses a laser, a laser wide temperature control method and a laser gas detection device, the resistance heating chip integrates a resistance element, when the current passes through the resistor, it will generate heat to heat the chip to the required temperature, this heating chip is often used in microfluid control, biological experiments and temperature control and other applications. In addition to these two chip heating methods, there are also heating methods that use the magnetization and hysteresis effect of magnetic materials to achieve heating. This scheme mainly uses an external magnetic field or magnet to magnetize the magnetic material in the chip, thereby generating heat and heating the chip to the ideal temperature.

[0004] The heating components used in the above-mentioned chip heating solutions do not directly contact the chip. Among them, the TEC and NTC temperature control solutions have high device costs due to the high price of TEC itself; while the temperature control solution using heating resistors and NTC and the method of heating using magnetic fields have low heating efficiency and high power consumption.

[0005] In addition, there are also solutions in the prior art that use air grooves for heat insulation by taking advantage of the low thermal conductivity of air, such as a waveguide structure disclosed in patent CN109804513A. Although the thermal conductivity of the air groove is very low, there is a risk of collapse. In order to solve the risk of collapse, CN114764163B in the prior art discloses a suspended waveguide support structure and a method for making it. The structure is relatively complex, with many manufacturing steps, which increases the process cost. Moreover, the structural design of the suspended waveguide and the air groove is only optimized in terms of chip heat transfer, and no fundamental improvement is made to the heating efficiency of the chip itself.

[0006] Therefore, it is necessary to provide a new fast heating wavelength tunable laser chip with integrated thermal insulation pad and a preparation method to solve the above technical problems. Summary of the invention

[0007] One of the main purposes of the present invention is to provide a fast heating wavelength tunable laser chip with an integrated thermal insulation pad, which improves the heating efficiency of the chip and can achieve precise adjustment of the heating temperature. The overall chip structure has high strength and low manufacturing cost.

[0008] The present invention achieves the above-mentioned purpose through the following technical scheme: a fast heating wavelength tunable laser chip with integrated thermal insulation pad, which includes an epitaxial structure, a passivation layer, a P-side metal and an N-side metal, wherein the epitaxial structure includes a substrate layer, a lower confinement layer, an active layer and an upper confinement layer in order from bottom to top; the active layer is set as a passive area and an active area along the cavity length direction, and a grating structure is arranged in the upper confinement layer, and the grating structure is arranged corresponding to the passive area and avoids the active area; the part of the lower confinement layer corresponding to the passive area is sacrificed to form a cavity, and the cavity is filled with thermal insulation material to form a thermal insulation pad layer; a ridge waveguide is formed on the front side of the epitaxial structure.

[0009] Furthermore, the thermal insulation material includes one or more combinations of silicon dioxide, silicon nitride, silicon carbide or silicate materials with thermal insulation effect.

[0010] Furthermore, the active area is located in the middle section, and two passive areas are provided, respectively located on both sides of the active area.

[0011] Furthermore, the ridge waveguide extends through the cavity length direction; two grooves are etched on the front side of the epitaxial structure, the ridge waveguide is formed between the two grooves, and the bottom of the groove extends to within the height range of the upper confinement layer.

[0012] Furthermore, the passivation layer covers the surface of the epitaxial structure and is provided with an opening corresponding to the ridge waveguide region. The P-surface metal is arranged on the ridge waveguide and is located within the active region.

[0013] Furthermore, a heating resistor is grown on the ridge waveguide corresponding to the passive area, and a second metal electrode connected to the heating resistor is provided on the passivation layer corresponding to the passive area; the second metal electrode is electrically connected to an external current control circuit to regulate the heating resistor.

[0014] Furthermore, a first metal electrode connected to the P-surface metal is provided on the passivation layer in a range corresponding to the active area.

[0015] Furthermore, a temperature measuring resistor for monitoring the temperature of the laser chip is grown on the passivation layer corresponding to the passive area. The temperature measuring resistor is electrically connected to an external temperature measurement circuit. The resistance value of the temperature measuring resistor is measured by the temperature measurement circuit to confirm the actual temperature of the chip, thereby providing a basis for the current control circuit to regulate the heating of the heating resistor.

[0016] Another object of the present invention is to provide a method for preparing the laser chip as described above, comprising the following steps: S1. Epitaxial structure growth: S11, growing an epitaxial material on the substrate layer to obtain a lower confinement layer; S12, removing the area required for the growth of the heat insulation material on the lower limiting layer to obtain the cavity; S13, growing a heat-insulating material in the region of the cavity to obtain a heat-insulating cushion layer; S14, continuing to grow the active region of the active layer on the lower limiting layer, and then butt-etching and growing the passive region of the active layer to complete the production of the active layer; S15, continuing to grow and fabricate a grating structure on the active layer within the range corresponding to the passive region to obtain an upper confinement layer, thereby completing the fabrication of the epitaxial structure; S2, ridge waveguide fabrication: performing secondary epitaxial material growth through epitaxial equipment to complete the growth of all epitaxial layers; then forming the ridge waveguide through photolithography, mask etching and semiconductor etching; S3, growing a passivation layer: growing a passivation layer on the epitaxial structure; S4, ridge waveguide windowing: removing the passivation layer on the ridge waveguide by photolithography and etching; S5, growing P-surface metal and heating resistors: growing the P-surface metal of the laser chip on the ridge waveguide corresponding to the active area; and growing the heating resistor on the ridge waveguide corresponding to the passive area; S6, manufacturing a temperature measuring resistor: preparing a first metal electrode connected to the P-side metal on the passivation layer corresponding to the active area, preparing a temperature measuring resistor for temperature monitoring and a second metal electrode connected to the heating resistor on the passivation layer corresponding to the passive area; S7. Grow N-side metal.

[0017] Compared with the prior art, the invention provides a fast-heating wavelength-tunable laser chip with an integrated thermal insulation pad and a preparation method thereof, which has the advantages of improving the heating efficiency of the chip, achieving accurate adjustment of the heating temperature, high overall chip structural strength and low manufacturing cost. (1) A heating resistor is directly integrated on the laser chip, and the heat generated by the heating resistor is used to heat the grating structure and ridge waveguide structure on the chip. The heating source is directly in contact with the waveguide structure on the laser chip, which greatly improves the heating efficiency. (2) A cavity is formed in the lower confinement layer corresponding to the passive region, and a heat-insulating material is grown in the cavity to form a heat-insulating cushion layer. On the one hand, this is beneficial for isolating the heat generated by the heating resistor, preventing the heat from continuing to be transferred downward to the substrate, and reducing the ineffective heat dissipation. At the same time, the heat is retained in the active layer and the upper confinement layer, effectively heating the ridge waveguide structure and the grating structure. On the other hand, compared with the original air cushion structure, the heat-insulating cushion layer retains the heat isolation effect and ensures the overall structural integrity of the laser chip, effectively solving the problem of air cushion cavity collapse. (3) A temperature measuring resistor is directly integrated on the laser chip and used in conjunction with a heating resistor. The heating resistor is electrically connected to an external current control circuit, and the temperature measuring resistor is electrically connected to an external temperature measurement circuit. The resistance value of the temperature measuring resistor is measured by the temperature measurement circuit, and the actual temperature of the laser chip is converted. Then, according to the chip temperature required by the process, the current flowing through the heating resistor is controlled by the circuit control circuit, thereby controlling the heating of the heating resistor, achieving accurate and effective control of the laser chip temperature, and realizing the adjustable function of the laser chip emission wavelength; (4) The heating resistor and the temperature measuring resistor are directly grown during the chip manufacturing process, which is low in cost; (5) The chip structure of this scheme can achieve higher heating efficiency, solving the problems of high cost and high power consumption of current chip heating schemes. The chip grating area can be heated to the target temperature in a shorter time, thereby achieving tuning of the target wavelength. The process is simple and low cost, and will not increase the overall difficulty and cost of chip manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a cross-sectional structure of an embodiment of the present invention; Figure 2 It is a schematic diagram of a top view of the structure of an embodiment of the present invention; The numbers in the figure represent: 100- Rapid heating wavelength tunable laser chip with integrated thermal insulation pad; 1-epitaxial structure, 11-substrate layer, 12-lower confinement layer, 121-thermal barrier layer, 13-active layer, 131-active region, 132-passive region, 14-upper confinement layer, 141-grating structure, 15-ridge waveguide, 16-groove; 2-passivation layer; 3-P-side metal; 4-N-side metal; 5-heating resistor; 6-temperature measuring resistor; 7-first metal electrode; 8-second metal electrode. DETAILED DESCRIPTION

[0019] Embodiment 1: Please refer to Figure 1-Figure 2 The present embodiment is a fast-heating wavelength-tunable laser chip 100 with an integrated thermal insulation pad, which includes an epitaxial structure 1, a passivation layer 2, a P-side metal 3, and an N-side metal 4.

[0020] The epitaxial structure 1 includes a substrate layer 11, a lower confinement layer 12, an active layer 13 and an upper confinement layer 14 from bottom to top. The active layer 13 is set to an inactive region 132 and an active region 131 along the cavity length direction (marked as the X direction in the figure). In this embodiment, the active region 131 is located in the middle section, and two inactive regions 132 are provided, respectively located on both sides of the active region 131; in other embodiments, only one active region 131 and one inactive region 132 may also be provided. A grating structure 141 is provided in the upper confinement layer 14, and the grating structure 141 is provided corresponding to the inactive region 132 and avoids the active region 131. A cavity is formed by sacrificing the inactive region 132 in the lower confinement layer 12, and a heat insulation material is grown and filled in the cavity to form a heat-resistant pad layer 121; the heat insulation material includes but is not limited to silicon dioxide, silicon nitride, silicon carbide or other silicate materials. A ridge waveguide 15 is formed on the front of the epitaxial structure 1, and the ridge waveguide 15 extends through the cavity length direction. Two grooves 16 are etched on the front of the epitaxial structure, and a ridge waveguide 15 is formed between the two grooves 16. The bottom of the groove 16 extends to the height range of the upper confinement layer 14, and its depth is set according to design requirements.

[0021] The passivation layer 2 covers the surface of the epitaxial structure 1, and an opening is provided in the area corresponding to the ridge waveguide 15. The P-face metal 3 is arranged on the ridge waveguide 15 and is located within the range of the active area 131. A heating resistor 5 is grown and formed on the ridge waveguide 15 corresponding to the range of the passive area 132. A first metal electrode 7 connected to the P-face metal 3 is also provided on the passivation layer 2 in the range corresponding to the active area 131, which is used for welding of gold wires or piercing of probes; a second metal electrode 8 connected to the heating resistor 5 is provided on the passivation layer 2 in the range corresponding to the passive area 132. The P-face metal 3 is the electrode of the laser chip, and its main function is to power the laser and provide sufficient excitation for the chip, so that the laser is lased and generates laser. In this process, the laser itself will also generate a certain amount of heat, which also has a certain heating effect on the laser. The heating resistor 5 is directly located on the ridge waveguide 15 to achieve thermal tuning of the wavelength. The second metal electrode 8 is electrically connected to an external current control circuit, and the input current of the current control circuit is controlled to adjust the heating resistor 5, thereby directly, accurately and efficiently heating the chip.

[0022] A temperature measuring resistor 6 for monitoring the temperature of the laser chip is grown on the passivation layer 2 in the range corresponding to the passive area 132. The temperature measuring resistor 6 is mainly used to detect the actual temperature of the chip. The actual temperature of the chip can be obtained by detecting the resistance value of the temperature measuring resistor 6, which provides a basis for regulating the heating resistor 5. The temperature measuring resistor 6 is electrically connected to an external temperature measurement circuit, and the resistance value of the temperature measuring resistor 6 is measured according to the temperature measurement circuit, thereby confirming the actual temperature of the chip, providing a basis for further precise regulation of the heating of the heating resistor 5.

[0023] The specific depth of the waveguide layer is determined according to design requirements; the period and depth of the grating structure 141 are also determined according to design requirements.

[0024] In this embodiment, a heating resistor 5 is directly grown on the surface of the chip, and its main material includes Pt, TaN (tantalum nitride), polysilicon or other heating resistor materials. The heating resistor 5 is powered to generate heat, and the grating structure 141 in the chip is heated to a preset temperature. Since the heating resistor 5 is directly integrated on the chip, compared with the original heating method through thermistors or heating resistors on the chip substrate or packaging components, its heating efficiency is higher, and the heating resistor 5 can be grown directly on the chip, which is lower in cost.

[0025] The presence of the passivation layer 2 is used to isolate the heating resistor 5 from the contact with the semiconductor material below; the material in a certain area below the chip active layer is replaced with a material with better thermal insulation performance through a semiconductor process to form a thermal insulation pad 121. Compared with semiconductor materials, the thermal conductivity of thermal insulation materials is very small and the thermal conductivity is poor. Therefore, the heat generated by the heating resistor 5 and the chip itself during operation is difficult to be conducted away due to the presence of the thermal insulation pad 121. This heat will be more concentrated near the chip active layer, so that more heat can be used to increase the temperature of the grating area, thereby achieving higher heating efficiency and obtaining faster wavelength tuning; compared with the structure of an air pad, the risk of possible structural collapse is avoided.

[0026] This embodiment also provides a method for preparing a fast heating wavelength tunable laser chip with an integrated thermal insulation pad, which comprises the following steps: S1. Epitaxial structure 1 growth: S11, growing an epitaxial material on the substrate layer 11 to obtain a lower confinement layer 12; S12, removing the area required for the growth of the heat insulating material on the lower limiting layer 12 to obtain the cavity; the cavity can be made by photolithography and / or etching, and the etching method can be wet etching or dry etching, or a combination of the two; S13, growing a heat-insulating material in the region of the cavity to obtain a heat-insulating pad layer 121; the heat-insulating material includes but is not limited to silicon dioxide, silicon nitride, silicon carbide or other silicate materials; S14, continuing to grow on the lower limiting layer 12 to obtain the active region 131 of the active layer 13, and then performing butt etching and growth to obtain the inactive region 132 of the active layer 13, thereby completing the production of the active layer 13; S15, continuing to grow and manufacture the upper limiting layer 14 on the active layer 13 corresponding to the range of the passive area 132, during the manufacturing process, manufacturing the grating pattern by electron beam exposure or full system exposure, forming the grating structure 141 by etching the grating formation layer, and then growing the cover layer material to obtain the upper limiting layer 14, completing the manufacturing of the epitaxial structure 1; except for the grating structure 141 area, the active area 131 is still in contact with the substrate 1 material, which is beneficial to the temperature control of these areas and prevents the laser from generating a mode hopping phenomenon; S2, ridge waveguide production: After the grating structure 141 is produced, secondary epitaxial material growth is performed through epitaxial equipment to complete the growth of all epitaxial layers, including epitaxial layer growth, including lower confinement layer, quantum well, upper confinement layer, grating layer and cap layer; then, ridge waveguide 15 is formed through photolithography, mask etching and semiconductor etching; the epitaxial layer growth is to grow N-type, P-type or undoped semiconductor material through MOCVD; S3, growing a passivation layer 2: growing silicon dioxide, silicon nitride or silicon oxynitride as a passivation layer material; S4, ridge waveguide windowing: remove the passivation layer on the ridge waveguide 15 by photolithography and etching, but note that the passivation layer under the heating resistor 5 area needs to be retained; S5, growing P-surface metal and heating resistor 5: growing P-surface metal 3 of the laser chip on the ridge waveguide 15 in the range corresponding to the active area 131 by photolithography and magnetron sputtering (or electron beam evaporation), forming an electrode pattern after metal stripping process, and then forming an ohmic contact with the wafer surface by rapid thermal annealing; at the same time, obtaining a heating resistor 5 in the range corresponding to the passive area 132 on the ridge waveguide 15 by photolithography, electron beam evaporation or magnetron sputtering, and metal stripping, the material of the heating resistor 5 includes but is not limited to Pt, TaN (tantalum nitride) or polysilicon; S6, manufacturing the temperature measuring resistor 6: through photolithography, electron beam evaporation or magnetron sputtering, metal stripping process, prepare a first metal electrode 7 connected to the P-surface metal 3 on the passivation layer 2 corresponding to the active area 131, prepare a temperature measuring resistor 6 for temperature monitoring and a second metal electrode 8 connected to the heating resistor 5 on the passivation layer 2 corresponding to the passive area 132; the material of the temperature measuring resistor 6 includes but is not limited to Pt, TaN (tantalum nitride) or polysilicon; S7. Grow N-side metal 4.

[0027] The shape of the heating resistor 5 includes but is not limited to rectangle, circle, triangle, thin strip, polygon or other combined shapes.

[0028] The laser chip structure in this embodiment can be applied to, for example, DFB, DBR, EML, Tunable chips, and can also be applied to other passive chips.

[0029] For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, all of which fall within the protection scope of the present invention.

Claims

1. A fast-heating wavelength-tunable laser chip with an integrated thermal insulation pad, comprising an epitaxial structure, a passivation layer, a P-side metal, and an N-side metal, wherein the epitaxial structure comprises a substrate layer, a lower confinement layer, an active layer, and an upper confinement layer in order from bottom to top; characterized in that: The active layer is set to be a passive area and an active area along the cavity length direction; a grating structure is arranged in the upper confinement layer, and the grating structure is arranged corresponding to the passive area and avoids the active area; a portion of the lower confinement layer corresponding to the passive area is sacrificed to form a cavity, and a heat-insulating material is grown and filled in the cavity to form a heat-resistant pad layer; a ridge waveguide is formed on the front side of the epitaxial structure.

2. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1, characterized in that: The thermal insulation material includes one or more combinations of silicon dioxide, silicon nitride, silicon carbide or silicate materials with thermal insulation effect.

3. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1, characterized in that: The active area is located in the middle section, and two passive areas are provided, which are respectively located at two sides of the active area.

4. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1, characterized in that: The ridge waveguide extends and penetrates along the cavity length direction; two grooves are etched on the front side of the epitaxial structure, the ridge waveguide is formed between the two grooves, and the bottom of the groove extends to the height range of the upper confinement layer.

5. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1, characterized in that: The passivation layer covers the surface of the epitaxial structure and is provided with an opening corresponding to the ridge waveguide region. The P-surface metal is arranged on the ridge waveguide and is located within the active region.

6. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1 or 5, characterized in that: A heating resistor is grown on the ridge waveguide within a range corresponding to the passive area, and a second metal electrode connected to the heating resistor is arranged on the passivation layer within a range corresponding to the passive area; the second metal electrode is electrically connected to an external current control circuit to regulate the heating resistor.

7. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 1 or 5, characterized in that: A first metal electrode connected to the P-surface metal is arranged on the passivation layer in a range corresponding to the active area.

8. The fast heating wavelength tunable laser chip with integrated thermal insulation pad as claimed in claim 6, characterized in that: A temperature measuring resistor for monitoring the temperature of the laser chip is grown on the passivation layer corresponding to the passive area. The temperature measuring resistor is electrically connected to an external temperature measurement circuit. The resistance value of the temperature measuring resistor is measured by the temperature measurement circuit to confirm the actual temperature of the chip, thereby providing a basis for the current control circuit to regulate the heating of the heating resistor.

9. A method for preparing a laser chip as claimed in claim 1, characterized in that: The following steps are involved: S1. Epitaxial structure growth: S11, growing an epitaxial material on the substrate layer to obtain a lower confinement layer; S12, removing the area required for the growth of the heat insulation material on the lower limiting layer to obtain the cavity; S13, growing a heat-insulating material in the region of the cavity to obtain a heat-insulating cushion layer; S14, continuing to grow the active region of the active layer on the lower limiting layer, and then butt-etching and growing the passive region of the active layer to complete the production of the active layer; S15, continuing to grow and fabricate a grating structure on the active layer within the range corresponding to the passive region to obtain an upper confinement layer, thereby completing the fabrication of the epitaxial structure; S2, ridge waveguide fabrication: performing secondary epitaxial material growth through epitaxial equipment to complete the growth of all epitaxial layers; then forming the ridge waveguide through photolithography, mask etching and semiconductor etching; S3, growing a passivation layer: growing a passivation layer on the epitaxial structure; S4, ridge waveguide windowing: removing the passivation layer on the ridge waveguide by photolithography and etching; S5, growing P-surface metal and heating resistors: growing the P-surface metal of the laser chip on the ridge waveguide corresponding to the active area; and growing the heating resistor on the ridge waveguide corresponding to the passive area; S6, manufacturing a temperature measuring resistor: preparing a first metal electrode connected to the P-side metal on the passivation layer corresponding to the active area, preparing a temperature measuring resistor for temperature monitoring and a second metal electrode connected to the heating resistor on the passivation layer corresponding to the passive area; S7. Grow N-side metal.

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