An electro-optic modulator
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI INTEGRATED CIRCUIT RESEARCH & DEVELOPMENT CENTER CO LTD
- Filing Date
- 2024-12-23
- Publication Date
- 2026-08-07
AI Technical Summary
然而，由于最内侧的空穴型注入的部分（即第一P型掺杂区）载流子浓度最小，且该区域非脊形区的厚度较薄，导致该区域的电阻最大，而较大的电阻会降低电光调制器的带宽
[0016] As can be seen, this utility model includes: a substrate; a photodiode disposed on the surface of the substrate; the photodiode includes an epitaxial layer, a P-type doped region, and an N-type doped region connected in sequence; the lattice constant of the epitaxial layer is greater than the lattice constant of the P-type doped region. This utility model provides an epitaxial layer with a lattice constant greater than that of the P-type doped region at one end. Due to the difference in lattice constant between the epitaxial layer and the P-type doped region, compressive stress is generated, which can improve the hole mobility in the P-type doped region, reduce the resistance, and thus increase the bandwidth of the electro-optic modulator.
Smart Images
Figure CN224609360U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of semiconductor technology, and in particular to an electro-optic modulator. Background Technology
[0002] An electro-optic modulator is a high-speed modulator based on silicon photonics technology, widely used in data centers and optical communications. An electro-optic modulator is a lateral diode that modulates light through carrier dispersion. The bandwidth of an electro-optic modulator is related to the link resistance and capacitance. The basic unit of an electro-optic modulator is as follows: Figure 1 As shown, this structure is a traditional Mach-Zehnder electro-optic modulator. To reduce the optical loss of the electro-optic modulator, traditional electro-optic modulators typically have three doped regions with doping concentrations increasing sequentially from the inside out, ensuring that the carrier concentration increases from the inside out. However, since the innermost hole-injected region (i.e., the first P-type doped region) has the lowest carrier concentration and the non-ridge region in this area is relatively thin, the resistance in this region is the highest. A higher resistance will reduce the bandwidth of the electro-optic modulator. Utility Model Content
[0003] In view of this, the purpose of this utility model is to provide an electro-optic modulator to solve the problem of narrow bandwidth of electro-optic modulators.
[0004] To solve the above-mentioned technical problems, this utility model provides an electro-optic modulator, comprising: a substrate; a photodiode disposed on the surface of the substrate; the photodiode comprising an epitaxial layer, a P-type doped region, and an N-type doped region connected in sequence; the lattice constant of the epitaxial layer is greater than the lattice constant of the P-type doped region.
[0005] Optionally, the N-type doped region includes a first N-type doped region, a second N-type doped region, and a third N-type doped region connected sequentially along a first direction; the first N-type doped region and the P-type doped region are connected; the doping concentration of the first N-type doped region, the second N-type doped region, and the third N-type doped region increases sequentially; the first direction is parallel to the substrate surface.
[0006] Optionally, the P-type doped region has a first ridge region at the end near the N-type doped region; the N-type doped region has a second ridge region at the end near the P-type doped region.
[0007] Optionally, the P-type doped region includes a P-type doped silicon layer; the lattice constant of the epitaxial layer is greater than the lattice constant of silicon.
[0008] Optionally, the epitaxial layer is a germanium layer or a germanium-silicon layer.
[0009] Optionally, the substrate includes a first silicon layer and a silicon dioxide layer disposed sequentially along the thickness direction; the photodiode is disposed on the surface of the silicon dioxide layer opposite to the first silicon layer.
[0010] Optionally, an isolation layer is further provided on the surface of the substrate; the isolation layer encapsulates the photodiode.
[0011] Optionally, a first electrode is further disposed on the surface of the epitaxial layer; the first electrode penetrates the isolation layer along the thickness direction and is connected to the epitaxial layer; a second electrode is further disposed on the surface of the N-type doped region; the second electrode penetrates the isolation layer along the thickness direction and is connected to the N-type doped region.
[0012] Optionally, the P-type doped region includes a second P-type doped region and a first P-type doped region connected sequentially along a first direction; the first P-type doped region and the N-type doped region are connected; the doping concentration of the second P-type doped region is greater than the doping concentration of the first P-type doped region; the second P-type doped region and the first P-type doped region have the same lattice constant; the first direction is parallel to the substrate surface.
[0013] The epitaxial layer is connected to the surface of the second P-type doped region that is away from the first P-type doped region.
[0014] Optionally, the P-type doped region includes a third P-type doped region, a second P-type doped region, and a first P-type doped region connected sequentially along a first direction; the first P-type doped region is connected to the N-type doped region; the doping concentration of the third P-type doped region, the second P-type doped region, and the first P-type doped region decreases sequentially; the lattice constants of the third P-type doped region, the second P-type doped region, and the first P-type doped region are the same; the first direction is parallel to the substrate surface.
[0015] The epitaxial layer is connected to the surface of the third P-type doped region away from the substrate.
[0016] As can be seen, this utility model includes: a substrate; a photodiode disposed on the surface of the substrate; the photodiode includes an epitaxial layer, a P-type doped region, and an N-type doped region connected in sequence; the lattice constant of the epitaxial layer is greater than the lattice constant of the P-type doped region. This utility model provides an epitaxial layer with a lattice constant greater than that of the P-type doped region at one end. Due to the difference in lattice constant between the epitaxial layer and the P-type doped region, compressive stress is generated, which can improve the hole mobility in the P-type doped region, reduce the resistance, and thus increase the bandwidth of the electro-optic modulator. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0018] Figure 1 This is a cross-sectional view of a traditional electro-optic modulator;
[0019] Figure 2 A cross-sectional view of an electro-optic modulator provided in an embodiment of this utility model;
[0020] Figures 3 to 9 This is a schematic flowchart illustrating a method for fabricating an electro-optic modulator according to an embodiment of the present invention.
[0021] The annotations in the attached figures are explained as follows:
[0022] 1-Substrate; 11-First silicon layer; 12-Silicon dioxide layer; 20-Second silicon layer; 211-First P-type doped region; 212-Second P-type doped region; 213-Third P-type doped region; 214-Epipolar layer; 221-First N-type doped region; 222-Second N-type doped region; 223-Third N-type doped region; 3-Isolation layer; 41-First electrode; 42-Second electrode. Detailed Implementation
[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0024] Please refer to Figure 2 , Figure 2 The present invention provides a cross-sectional view of an electro-optic modulator, which may include: a substrate 1; a photodiode disposed on the surface of the substrate 1; the photodiode includes an epitaxial layer 214, a P-type doped region and an N-type doped region connected in sequence; the lattice constant of the epitaxial layer 214 is greater than the lattice constant of the P-type doped region.
[0025] This embodiment does not limit the specific type of substrate 1. Substrate 1 may include, but is not limited to, a first silicon layer 11 and a silicon dioxide layer 12 arranged sequentially along the thickness direction; a photodiode is disposed on the surface of silicon dioxide layer 12 opposite to the first silicon layer 11. It should be noted that silicon and silicon dioxide are common materials in the prior art. This embodiment does not limit the internal composition of substrate 1, but directly uses a structure formed by stacking film layers made of existing materials along the thickness direction as substrate 1.
[0026] This embodiment does not limit the specific type of P-type doped region; the P-type doped region may include, but is not limited to, a P-type doped silicon layer. The lattice constant of the P-type doped silicon layer is the same as the lattice constant of silicon. Accordingly, in this embodiment, the lattice constant of the epitaxial layer 214 may be greater than the lattice constant of silicon. It should be noted that silicon and P-type ions are common materials in the prior art. The P-type doped silicon layer is formed by implanting P-type ions into a silicon layer, which is also a common material in the prior art. This embodiment does not limit the internal composition of the P-type doped region, but directly uses a P-type doped silicon layer made of existing materials.
[0027] This embodiment does not limit the specific type of epitaxial layer 214. It can be determined based on the specific type of the P-type doped region. For example, when the P-type doped region includes a P-type doped silicon layer, the epitaxial layer 214 can be a germanium layer or a germanium-silicon layer. It should be noted that germanium and germanium-silicon are common materials in the prior art. This embodiment does not limit the internal composition of the epitaxial layer 214, but directly uses a film layer made of existing materials as the epitaxial layer 214. Furthermore, it should be noted that when this embodiment uses a germanium layer or a germanium-silicon layer, its fabrication process is compatible with silicon photonics processes and does not require additional processes.
[0028] This embodiment does not limit the specific structure of the P-type doped region, and may include the following two structures:
[0029] (1) The P-type doped region includes a second P-type doped region 212 and a first P-type doped region 211 connected sequentially along a first direction; the first P-type doped region 211 is connected to the N-type doped region; the doping concentration of the second P-type doped region 212 is greater than the doping concentration of the first P-type doped region 211; the lattice constants of the second P-type doped region 212 and the first P-type doped region 211 are the same; the first direction is parallel to the surface of the substrate 1. Accordingly, the epitaxial layer 214 can be connected to the surface of the second P-type doped region 212 away from the surface of the first P-type doped region 211.
[0030] This embodiment does not limit the specific thickness of the epitaxial layer 214. For example, the thickness of the epitaxial layer 214 can be no less than the thickness of the second P-type doped region 212; the thickness of the epitaxial layer 214 can be less than the thickness of the second P-type doped region 212. Among them, when the thickness of the epitaxial layer 214 is no less than the thickness of the second P-type doped region 212, the effect of improving hole mobility is better.
[0031] This embodiment does not limit the specific position of the epitaxial layer 214 relative to the second P-type doped region 212. For example, the surface of the epitaxial layer 214 near the substrate 1 may not be higher than the surface of the second P-type doped region 212 near the substrate 1; the surface of the epitaxial layer 214 near the substrate 1 may be higher than the surface of the second P-type doped region 212 near the substrate 1. When the surface of the epitaxial layer 214 near the substrate 1 is not higher than the surface of the second P-type doped region 212 near the substrate 1, the effect of improving hole mobility is better.
[0032] (2) The P-type doped region includes a third P-type doped region 213, a second P-type doped region 212, and a first P-type doped region 211 connected sequentially along a first direction; the first P-type doped region 211 is connected to the N-type doped region; the doping concentrations of the third P-type doped region 213, the second P-type doped region 212, and the first P-type doped region 211 decrease sequentially; the lattice constants of the third P-type doped region 213, the second P-type doped region 212, and the first P-type doped region 211 are the same; the first direction is parallel to the surface of the substrate 1. Correspondingly, the epitaxial layer 214 can be connected to the surface of the third P-type doped region 213 away from the substrate 1.
[0033] It should be noted that the third P-type doped region 213, the second P-type doped region 212, and the first P-type doped region 211 can all be P-type doped silicon layers.
[0034] Furthermore, in this embodiment, the end of the P-type doped region near the N-type doped region may have a first ridge region. Specifically, the first P-type doped region 211 may have a first ridge region at the end near the N-type doped region. In this structure, the first P-type doped region 211 includes a first ridge region and a first non-ridge region, wherein the thickness of the first non-ridge region is less than the thickness of the first ridge region; the thickness of the second P-type doped region 212 may be, but is not limited to, equal to the thickness of the first non-ridge region; and the thickness of the third P-type doped region 213 may be, but is not limited to, greater than the thickness of the second P-type doped region 212.
[0035] This embodiment does not limit the specific type of N-type doped region. The N-type doped region may include, but is not limited to, an N-type doped silicon layer. It should be noted that silicon and N-type ions are common materials in the prior art. The N-type doped silicon layer is formed by implanting N-type ions into a silicon layer, which is also a common material in the prior art. This embodiment does not limit the internal composition of the N-type doped region, but directly uses an N-type doped silicon layer made of existing materials.
[0036] This embodiment does not limit the specific structure of the N-type doped region, and may include, but is not limited to, the following structure: the N-type doped region includes a first N-type doped region 221, a second N-type doped region 222, and a third N-type doped region 223 connected sequentially along a first direction; the first N-type doped region 221 is connected to a P-type doped region; the doping concentration of the first N-type doped region 221, the second N-type doped region 222, and the third N-type doped region 223 increases sequentially; the first direction is parallel to the surface of the substrate 1. It should be noted that the first N-type doped region 221, the second N-type doped region 222, and the third N-type doped region 223 can all be N-type doped silicon layers.
[0037] Furthermore, in this embodiment, the end of the N-type doped region near the P-type doped region may have a second ridge region. Specifically, the first N-type doped region 221 may have a second ridge region at the end near the P-type doped region. In this structure, the first N-type doped region 221 includes a second ridge region and a second non-ridge region, wherein the thickness of the second non-ridge region is less than the thickness of the second ridge region; the thickness of the second N-type doped region 222 may be, but is not limited to, equal to the thickness of the second non-ridge region; and the thickness of the third N-type doped region 223 may be, but is not limited to, greater than the thickness of the second N-type doped region 222.
[0038] Furthermore, in this embodiment, an isolation layer 3 may also be disposed on the surface of the substrate 1; the isolation layer 3 may encapsulate the photodiode. This embodiment does not limit the specific type of the isolation layer 3; the isolation layer 3 may be, but is not limited to, a silicon dioxide layer. It should be noted that silicon dioxide is a common material in the prior art, and this embodiment does not limit the internal composition of the isolation layer 3, but directly uses a film layer made of existing materials as the isolation layer 3.
[0039] Furthermore, in this embodiment, a first electrode 41 may be disposed on the surface of the epitaxial layer 214; the first electrode 41 penetrates the isolation layer 3 along the thickness direction and is connected to the epitaxial layer 214; a second electrode 42 may be disposed on the surface of the N-type doped region; the second electrode 42 penetrates the isolation layer 3 along the thickness direction and is connected to the N-type doped region. Specifically, the second electrode 42 may be disposed on the surface of the third N-type doped region 223.
[0040] This embodiment does not limit the specific type of the first electrode 41. For example, the first electrode 41 can be a tungsten electrode, a copper electrode, or an aluminum electrode. Similarly, this embodiment does not limit the specific type of the second electrode 42. For example, the second electrode 42 can be a tungsten electrode, a copper electrode, or an aluminum electrode. It should be noted that tungsten, copper, and aluminum are common materials in the prior art. This embodiment does not limit the internal composition of the first electrode 41 and the second electrode 42, but directly uses tungsten, copper, and aluminum electrodes made from existing materials.
[0041] Based on the above embodiments, the present invention provides an epitaxial layer with a lattice constant greater than that of the P-type doped region at one end. Due to the difference in lattice constant between the epitaxial layer and the P-type doped region, compressive stress will be generated, which can improve the hole mobility in the P-type doped region, reduce the resistance, and thus increase the bandwidth of the electro-optic modulator.
[0042] To make this utility model easier to understand, please refer to... Figures 3 to 9 , Figures 3 to 9 This is a schematic flowchart illustrating a method for fabricating an electro-optic modulator according to an embodiment of the present invention. The process includes:
[0043] 1. For example Figure 3 As shown, the silicon-based optoelectronic process starts with silicon-on-insulator (SOI), and the resulting SOI wafer includes a first silicon layer 11, a silicon dioxide layer 12, and a second silicon layer 20 sequentially disposed along the thickness direction; wherein, the first silicon layer 11 and the silicon dioxide layer 12 constitute the substrate 1;
[0044] 2. For example Figure 4 As shown, the morphology of the electro-optic modulator is first etched into the second silicon layer 20 using a photolithography etching process, forming three ridge regions;
[0045] 3. For example Figure 5 As shown, P-type ions and N-type ions are doped into the etched second silicon layer 20 through photolithography and ion implantation processes to fabricate a diode structure. The diode structure includes a third P-type doped region 213, a second P-type doped region 212, a first P-type doped region 211, a first N-type doped region 221, a second N-type doped region 222, and a third N-type doped region 223 connected sequentially along a first direction. The doping concentrations of the third P-type doped region 213, the second P-type doped region 212, and the first P-type doped region 211 decrease sequentially, while the doping concentrations of the first N-type doped region 221, the second N-type doped region 222, and the third N-type doped region 223 increase sequentially.
[0046] 4. For example Figure 6 As shown, silicon dioxide is filled as the isolation layer 3, so that the isolation layer 3 encapsulates the diode structure;
[0047] 5. For example Figure 7 As shown, the isolation layer 3 and the third P-type doped region 213 on the surface are removed by etching the opening;
[0048] 6. For example Figure 8 As shown, in the area of the opening, germanium or germanium-silicon epitaxy is performed to form an epitaxial layer 214. In this embodiment, the epitaxial layer 214 can be a germanium layer or a germanium-silicon layer.
[0049] 7. For example Figure 9As shown, the open area is filled with silicon dioxide as an isolation layer 3;
[0050] 8. By using metal processing techniques such as tungsten, copper, or aluminum to bring out the electrodes of the photodiode, as shown in the figure. Figure 2 The electro-optic modulator shown has a first electrode 41 led out from the surface of the epitaxial layer 214 and a second electrode 42 led out from the surface of the third N-type doped region 223.
[0051] The electro-optic modulator provided in this embodiment of the present invention uses an epitaxial layer 214 with a lattice constant greater than that of the P-type doped region to be set at one end of the P-type doped region. Due to the difference in lattice constant between the epitaxial layer 214 and the P-type doped region, compressive stress is generated, which can improve the hole mobility in the P-type doped region, reduce the resistance, and thus increase the bandwidth of the electro-optic modulator.
[0052] The above provides a detailed description of an electro-optic modulator provided by this utility model. For those skilled in the art, based on the ideas of the embodiments of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.
Claims
1. An electro-optic modulator, characterized in that, include: A substrate; a photodiode is disposed on the surface of the substrate; the photodiode includes an epitaxial layer, a P-type doped region, and an N-type doped region connected in sequence; The lattice constant of the epitaxial layer is greater than the lattice constant of the P-type doped region.
2. The electro-optic modulator according to claim 1, characterized in that, The N-type doped region includes a first N-type doped region, a second N-type doped region, and a third N-type doped region connected sequentially along a first direction; the first N-type doped region and the P-type doped region are connected; the doping concentration of the first N-type doped region, the second N-type doped region, and the third N-type doped region increases sequentially; the first direction is parallel to the substrate surface.
3. The electro-optic modulator according to claim 1, characterized in that, The P-type doped region has a first ridge region at the end near the N-type doped region; the N-type doped region has a second ridge region at the end near the P-type doped region.
4. The electro-optic modulator according to claim 1, characterized in that, The P-type doped region includes a P-type doped silicon layer; the lattice constant of the epitaxial layer is greater than the lattice constant of silicon.
5. The electro-optic modulator according to claim 4, characterized in that, The epitaxial layer is a germanium layer or a germanium-silicon layer.
6. The electro-optic modulator according to claim 1, characterized in that, The substrate includes a first silicon layer and a silicon dioxide layer disposed sequentially along the thickness direction; the photodiode is disposed on the surface of the silicon dioxide layer opposite to the first silicon layer.
7. The electro-optic modulator according to claim 1, characterized in that, An isolation layer is also provided on the surface of the substrate; the isolation layer encapsulates the photodiode.
8. The electro-optic modulator according to claim 7, characterized in that, The surface of the epitaxial layer is further provided with a first electrode; the first electrode penetrates the isolation layer along the thickness direction and is connected to the epitaxial layer; the surface of the N-type doped region is further provided with a second electrode; the second electrode penetrates the isolation layer along the thickness direction and is connected to the N-type doped region.
9. The electro-optic modulator according to any one of claims 1 to 8, characterized in that, The P-type doped region includes a second P-type doped region and a first P-type doped region connected sequentially along a first direction; the first P-type doped region and the N-type doped region are connected; the doping concentration of the second P-type doped region is greater than the doping concentration of the first P-type doped region; the second P-type doped region and the first P-type doped region have the same lattice constant; the first direction is parallel to the substrate surface. The epitaxial layer is connected to the surface of the second P-type doped region that is away from the first P-type doped region.
10. The electro-optic modulator according to any one of claims 1 to 8, characterized in that, The P-type doped region includes a third P-type doped region, a second P-type doped region, and a first P-type doped region connected sequentially along a first direction; the first P-type doped region is connected to the N-type doped region; the doping concentration of the third P-type doped region, the second P-type doped region, and the first P-type doped region decreases sequentially; the lattice constants of the third P-type doped region, the second P-type doped region, and the first P-type doped region are the same; the first direction is parallel to the substrate surface. The epitaxial layer is connected to the surface of the third P-type doped region away from the substrate.