TWI848382B - Processing method for flip-chip VCSEL structure with high refractive index contrast DBR - Google Patents

Abstract

The present invention relates to a process method for a flip-chip VCSEL structure of a high refractive index contrast DBR, in which part of Al ₂ O ₃ is replaced by ohmic metal, and a high thermal conductivity and low resistance conduction path formed by a heat dissipation substrate and AlGaAs/ohmic metal is used to separate the optical path from the electrical path. The stacked structure formed by Al ₂ O ₃ / _{AlyGa1 -yAs} DBR can reduce the number of DBR layer logarithms, changing the practice of using the highest Al component as the current aperture limiting layer, so that the electrical and optical performances are significantly improved, and the conversion efficiency and total output power are improved.

Description

Process method for flip-chip VCSEL structure with high refractive index contrast DBR

The present invention relates to the field of VCSEL technology, and in particular to a process method for a flip-chip VCSEL structure with a high refractive index contrast DBR.

The current mainstream GaAs-based VCSEL structure has the following characteristics:

1. Current confinement AlGaAs is converted into Al ₂ O ₃ by oxidation process. The oxidized part forms the current confinement layer, and the unoxidized part forms the current channel. The overall current channel is small, and AlGaAs itself is a semiconductor material that is difficult to dope, and has a higher resistance than metal.

_{2. Al2O3} formed after AlGaAs is oxidized is an insulator, which plays the role of current limitation and optical limitation (destroying the resonant cavity).

3. Even the flip-chip structure is limited to the chip surface and does not reach deep into the DBR.

In view of the above situation, it is necessary to propose a process method for a flip-chip VCSEL structure with a high refractive index contrast DBR.

y<1)中高Al%組分Al_xGa_1-xAs的部分進行完全氧化，使其轉變成Al₂O₃，在所需的光學路徑上形成Al₂O₃/Al_yGa_1-yAs DBR堆疊結構，並以結構中最臨近有源區的至少一層中Al%組分Al_zGa_1-zAs形成 一電流孔徑，且層間以Al_yGa_1-yAs作為一間隔層，並通過控制其氧化速率控制該電流孔徑的大小，其中Al%組分滿足x>z>y；將週邊部分完全氧化所形成的Al₂O₃以化學蝕刻方式去除，保留光學路徑的Al₂O₃/Al_yGa_1-yAs DBR堆疊結構；及去除週邊部分的Al₂O₃所形成的空間以原子層沉積、濺鍍、蒸鍍及電鍍中的一種或多種組合方式填充歐姆金屬，以形成低電阻的電學導通路徑。 In order to solve the above technical problems, the technical solution adopted by the present invention is: a process method for a flip-chip VCSEL structure with a high refractive index contrast DBR, comprising the following steps: a main DBR _{AlxGa1 -xAs} / _{AlyGa1-yAs (} x>y, 0

y<1) is completely oxidized to convert the high Al% component _{AlxGa1 -xAs} into _Al2O3 , forming _{an Al2O3} / _{AlyGa1 -yAs} DBR stacking structure on the desired optical path, and forming a current aperture with at least one layer of Al% component _{AlzGa1 -zAs} closest to the active region in the structure, and _{AlyGa1 -yAs is} used as a spacer between the layers, and the size of the current aperture is controlled by controlling its oxidation rate, wherein the Al% component satisfies x>z>y; removing _{the Al2O3 formed} by the complete oxidation of the peripheral part by chemical etching, retaining the _Al2O3 / _{AlyGa1 -yAs DBR} stacking structure of the optical path; and removing the _Al2O3 in the peripheral part The space formed by ₃ is filled with ohmic metal by one or a combination of atomic layer deposition, sputtering, evaporation and electroplating to form a low-resistance electrical conduction path.

Furthermore, it also includes: epitaxial structure growth, forming a GaAs substrate, a first DBR region, an active region, and a second DBR region from bottom to top; platform etching, that is, etching the second DBR region to form a primary etching platform; first electrode manufacturing, forming the first electrode on the primary etching platform.

Furthermore, it also includes heat sink substrate bonding, that is, bonding the heat sink substrate at one end of the second DBR region away from the active region.

Furthermore, the heat sink includes one or more of Mo, Si, Cu, and CuW.

Furthermore, it also includes GaAs substrate removal, second electrode fabrication, passivation protection/substrate cutting, and second electrode electroplating connection.

The beneficial effect of the present invention is that part of Al ₂ O ₃ is replaced by ohmic metal, and the high thermal conductivity and low resistance conduction path formed by the heat sink, AlGaAs/ohmic metal separates the optical path from the electrical path. The stacked structure formed by Al ₂ O ₃ / _{AlyGa1 -yAs} DBR can reduce the number of DBR layers, changing the practice of using the highest Al component as the current aperture limiting layer, so that the electrical and optical performances are significantly improved, and the conversion efficiency and total output power are improved.

100: First DBR Zone

110: Stack structure

120: Ohm metal

130: Current aperture

140:Al ₂ O ₃ layers

150: Interlayer

200: Active area

300: Second DBR Zone

400: Heat dissipation lining

500: First electrode

600: Second electrode

700: Passivation layer

800:GaAs substrate

(a)~(f): Method steps

FIG1 is a schematic diagram of a flip-chip VCSEL structure of a high refractive index contrast DBR in an embodiment of the present invention; FIG2 is a schematic diagram of another embodiment of a flip-chip VCSEL structure of a high refractive index contrast DBR in an embodiment of the present invention; FIG3 is a schematic diagram of a flip-chip VCSEL structure of a high refractive index contrast DBR and its process method in an embodiment of the present invention.

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following is a further detailed description of the flip-chip VCSEL structure and process method of a high refractive index contrast DBR of the present invention in combination with the attached figures and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

Referring to FIG. 1 to FIG. 3 , a flip-chip VCSEL structure with a high refractive index contrast DBR includes, from top to bottom, a first DBR region 100, an active region 200, a second DBR region 300, and a heat sink 400. In the second DBR region 300, the x of the high aluminum content Al _x Ga _1-x As gradually decreases from the active region 200 to the surface, and a stacking structure 110 is composed of Al ₂ O ₃ / _Aly Ga _1-y As and the y of the stacking structure 110 gradually increases from the active region 200 to the surface. The stacking structure 110 has Al ₂ O 3 on both sides. ₃ layers 140, the stacked structure 110 is filled with ohmic metal 120, and a current aperture 130 is formed in at least one layer of Al% component _{AlzGa1 -zAs} below the active area 200 and closest to the active area 200, and _{AlyGa1 -yAs} is used as a spacer 150 between the layers as a means to adjust the device series resistance and light type, where x>z>y.

The ohm metal 120 replaces part of Al ₂ O ₃ , and the high thermal conductivity and low resistance conduction path formed by the heat sink 400 and AlGaAs/ohm metal 120 separates the optical path from the electrical path. The stacked structure 110 formed by Al ₂ O ₃ / _{AlyGa1 -yAs} DBR can reduce the number of DBR layers, changing the practice of using the highest Al component as the current aperture 130 limiting layer, so that the electrical and optical performances are significantly improved, and the conversion efficiency and power are high.

Preferably, the diameter of the current aperture 130 is smaller than the diameter of the stacked structure 110.

Please refer to FIG. 1 and FIG. 2 , in particular, the first DBR region 100 is a p-DBR, and a p-electrode is provided on the p-DBR; the second DBR region 300 is an n-DBR, and an n-electrode is connected to the n-DBR.

Furthermore, the heat sink substrate 400 includes a metal substrate or a highly impurity-doped Si substrate.

Furthermore, the heat sink 400 includes one or more of Mo, Si, Cu, and CuW.

y<1)中高Al%組分Al_xGa_1-xAs的部分進行完全氧化，使其轉變成Al₂O₃，在所需的光學路徑上形成Al₂O₃/Al_yGa_1-yAs DBR堆疊結構110，並以結構中最臨近該有源區200的至少一層中Al%組分Al_zGa_1-zAs形成該電流孔徑130，且層間以Al_yGa_1-yAs作為該間隔層150，並通過控制其氧化速率控制該電流孔徑130的大小，其中Al%組分滿足x>z>y；將週邊部分完全氧化所形成的Al₂O₃以化學蝕刻方式去除，保留光學路徑的Al₂O₃/Al_yGa_1-yAs DBR堆疊結構110；去除週邊部分的Al₂O₃所形成的空間以原子層沉積、濺鍍、蒸鍍及電鍍中的一種或多種組合方式填充歐姆金屬120，以形成低電阻的電學導通路徑。 3, the present invention also provides a method for manufacturing _a flip-chip VCSEL structure with _a high refractive index contrast _DBR , comprising the following steps _:

y<1) is completely oxidized to convert the _{Al2O3 / AlyGa1-yAs DBR stack structure 110 on the desired optical path, and the current aperture 130 is formed by using the Al% component AlzGa1-zAs in at least one} layer closest to the active region 200 in the structure, and the spacer 150 is used as _{AlyGa1 -yAs} between the layers, and the size of the current aperture 130 is controlled by controlling the oxidation rate thereof, wherein _{the Al} % component satisfies x>z>y; _{the Al2O3} formed by the complete oxidation of the peripheral part is removed by chemical etching, _{and the Al2O3} / _{AlyGa1 -yAs} in the optical path is retained. The DBR stack structure 110 is formed by removing the peripheral Al ₂ O ₃ and then filling the space with ohmic metal 120 by one or more combinations of atomic layer deposition, sputtering, evaporation and electroplating to form a low-resistance electrical conduction path.

Please refer to Figure 3, which also includes: epitaxial structure growth, forming a GaAs substrate 800, the first DBR region 100, the active region 200, and the second DBR region 300 from bottom to top; platform etching, that is, etching the second DBR region 300 to form a primary etching platform; and the first electrode 500 is manufactured, forming the first electrode 500 on the primary etching platform.

Please refer to FIG. 3 , which also includes heat sink substrate bonding, that is, the heat sink substrate 400 is bonded at one end of the second DBR region 300 away from the active region 200.

Furthermore, the heat sink 400 includes one or more of Mo, Si, Cu, and CuW.

Please refer to Figure 3, which also includes the removal of GaAs substrate 800, the production of the second electrode 600, passivation protection/substrate cutting, and electroplating connection of the second electrode 600.

In particular, please refer to FIG. 3 , between the second electrode 600 and the heat sink 400 , a passivation layer 700 is provided outside the first DBR region 100 , the active region 200 , and the second DBR region 300 .

y<1)中高Al%組分Al_xGa_1-xAs的部分進行完全氧化，使其轉變成Al₂O₃，在所需的光學路徑上形成Al₂O₃/Al_yGa_1-yAs DBR堆疊結構110，並以結構中最臨近該有源區200的至少一層中Al%組分Al_zGa_1-zAs形成該電流孔徑130，且層間以Al_yGa_1-yAs作為該間隔層150，並通過控制其氧化速率控制該電流孔徑130的大小，其中Al%組分滿足x>z>y；(d)二次平臺蝕刻，形成該二次蝕刻平面，並且通過蝕刻將該第二DBR區300內的週邊部分完全氧化所形成的Al₂O₃以去除；(e)歐姆金屬120填充，去除週邊部分的Al₂O₃所形成的空間以原子層沉積、濺鍍、蒸鍍及電鍍中的一種或多種組合方式填充歐姆金屬120，以形成低電阻的電學導通路徑；(f)散熱襯底400鍵合，在該第二DBR區300上鍵合連接該散熱襯底400；(g)GaAs襯底800去除，將外延結構倒置，去除外延成長形成的該GaAs襯底800；(h)第二電極600製作，在該第一DBR區100上製作第二電極600；(i)鈍化保護/襯底切割，鈍化保護即在該散熱襯底400上方的該第一DBR區100、該有源區200和該第二DBR區300外形成該鈍化層700，襯底切割即根據需要切割該散熱襯底400；(j)第二電極600電鍍連接。 As can be understood, the whole process forms a flip-chip VCSEL. Specifically, please refer to FIG. 3. First, (a) epitaxial structure growth is performed to sequentially form the GaAs substrate 800, the first DBR region 100, the active region 200, and the second DBR region 300; (b) platform etching/first electrode 500 manufacturing is then performed; (c) an oxidation method is used to form a light window, and a light window is formed in the second DBR region 300, and the x in the high aluminum content _{AlxGa1 -xAs} is gradually decreased from the active region 200 to the surface, and the main DBR _{AlxGa1 -xAs} /AlyGa1 _{-yAs (} x>y, 0

(d) performing secondary platform etching to form the secondary etching plane, and completely oxidizing the _{Al2O3 / AlyGa1-yAs DBR stack structure 110 on the desired optical path, and forming the current aperture 130 with the Al% component of AlzGa1-zAs in at least} one layer closest to the active region 200 in the structure, and using _{the AlyGa1 - yAs} as _the spacer layer ₁₅₀ between the layers, and controlling the size of the current aperture 130 by controlling the oxidation rate thereof, wherein the Al% component satisfies x>z>y; and (e) performing secondary platform etching to form the secondary etching plane, and completely oxidizing the peripheral portion in the second DBR region 300 by etching to form the _Al2O3/ AlyGa1-yAs DBR stack structure 110. ₃ is removed; (e) Ohm metal 120 filling, the space formed by removing the peripheral Al ₂ O ₃ is filled with Ohm metal 120 by one or more combinations of atomic layer deposition, sputtering, evaporation and electroplating to form a low-resistance electrical conduction path; (f) heat sink substrate 400 bonding, the heat sink substrate 400 is bonded and connected to the second DBR region 300; (g) GaAs substrate 800 removal, the epitaxial structure is inverted, and the GaAs substrate 800 formed by epitaxial growth is removed; ( h) Fabrication of the second electrode 600: fabricating the second electrode 600 on the first DBR region 100; (i) passivation protection/substrate cutting: passivation protection is forming the passivation layer 700 outside the first DBR region 100, the active region 200 and the second DBR region 300 above the heat sink substrate 400; substrate cutting is cutting the heat sink substrate 400 as needed; (j) electroplating connection of the second electrode 600.

It can be understood that Al ₂ O ₃ or aluminum oxide generally refers to a mixture of Al ₂ O ₃ as a main component and a small amount of Ga ₂ O ₃ , GaAs or AlAs, which is obtained by oxidation of AlGaAs in the VCSEL structure.

It should be noted that if there are directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement of the components in a certain posture (as shown in the attached figure). If the specific posture changes, the directional indication will also change accordingly. In general, the direction of the mouthpiece relative to the base is up or top.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

In summary, the present invention provides a flip-chip VCSEL structure with a high refractive index contrast DBR and a process method thereof, in which part of Al ₂ O ₃ is replaced by ohmic metal, and the heat dissipation substrate, AlGaAs/ohmic metal form a high thermal conductivity and low resistance conduction path, so that the optical path and the electrical path are separated. The stacked structure formed by Al ₂ O ₃ / _{AlyGa1 -yAs} DBR can reduce the number of DBR layers, change the practice of using the highest Al component as the current aperture limiting layer, so that the electrical and optical performances are significantly improved, and the conversion efficiency and total output power are improved.

The above is only the preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as the preferred embodiment, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the above disclosed technical contents within the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

(a)~(f): Method steps

Claims (5)

A method for manufacturing a flip-chip VCSEL structure with a high refractive index contrast DBR is characterized by comprising the following steps: forming a main DBR _{AlxGa1 -xAs} /AlyGa1 _{-yAs (} x>y, 0

y<1) is completely oxidized to convert the high Al% component _{AlxGa1 -xAs} into _Al2O3 , forming _{an Al2O3} / _{AlyGa1 -yAs} DBR stacking structure on the desired optical path, and forming a current aperture with at least one layer of Al% component _{AlzGa1 -zAs} closest to the active region in the structure, and _{AlyGa1 -yAs is} used as a spacer between the layers, and the size of the current aperture is controlled by controlling its oxidation rate, wherein the Al% component satisfies x>z>y; removing _{the Al2O3 formed} by the complete oxidation of the peripheral part by chemical etching, retaining the _Al2O3 / _{AlyGa1 -yAs DBR} stacking structure of the optical path; and removing the _Al2O3 in the peripheral part The space formed by ₃ is filled with ohmic metal by one or a combination of atomic layer deposition, sputtering, evaporation and electroplating to form a low-resistance electrical conduction path. The process method of the flip-chip VCSEL structure of the high refractive index contrast DBR as described in claim 1, further comprising: epitaxial structure growth, forming a GaAs substrate, a first DBR region, an active region, and a second DBR region from bottom to top; platform etching, that is, etching the second DBR region to form a primary etching platform; and first electrode manufacturing, forming the first electrode on the primary etching platform. The process method of the flip-chip VCSEL structure of the high refractive index contrast DBR as described in claim 1 further includes bonding of a heat sink substrate, that is, bonding a heat sink substrate at one end of the second DBR region away from the active region. The process method of the flip-chip VCSEL structure of the high refractive index contrast DBR as described in claim 3, wherein the heat sink includes one or more of Mo, Si, Cu, and CuW. The process method of the flip-chip VCSEL structure of the high refractive index contrast DBR as described in claim 1, which also includes GaAs substrate removal, second electrode fabrication, passivation protection/substrate cutting, and second electrode electroplating connection.