Silicon light modulator, optical device and optical module

Abstract

The invention discloses a silicon light modulator which comprises a first flat plate area structure and a second flat plate area structure, and the second flat plate area structure is arranged on a ridge waveguide of the modulator and located above the first flat plate area structure. The invention also discloses an optical device. The invention also discloses an optical module. The silicon light modulator has the advantages that the second flat plate region structure is added, so that the series resistance of the modulation region is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a silicon photonic modulator, optical device, and optical module. Background Technology

[0002] Silicon photonics technology uses silicon and silicon-based substrates as optical media to fabricate corresponding photonic and optoelectronic devices through CMOS integrated circuit processes. This enables practical applications in optical communication, optical sensing, and optical computing, complementing existing semiconductor wafer manufacturing technologies. With the joint development of academia and industry, silicon photonics technology can now leverage the mature CMOS manufacturing and design ecosystem to build integrated photonic systems, achieving combined applications at different levels, from optical devices and chips to optical modules. Modulators are crucial optical devices. Commonly used silicon photonic modulators often utilize the free carrier dispersion effect. By doping a transmission waveguide with a specific optical structure, the waveguide becomes an active waveguide with a specific doped structure. Changing the voltage of the active waveguide alters the distribution of carriers within it, causing a change in the effective refractive index. Through specific optical structures, such as Mach-Zehnder interferometers, the output light intensity is varied, achieving optical modulation. Currently, there are three main types of modulator waveguide doping structures based on carrier dispersion effect: carrier injection PIN structure, carrier aggregation effect MOS capacitor structure, and carrier dissipation PN structure.

[0003] Figure 1 This is a schematic diagram of the cross-section of a common silicon photoelectric carrier dissipation PN-type modulator waveguide, including a silicon substrate A, a silicon dioxide buried layer B, a silicon dioxide capping layer C, a metal electrode 107, and a first N-type lightly doped region 101, a first N-type moderately doped region 102, a first N-type heavily doped region 103, a first P-type lightly doped region 104, a first P-type moderately doped region 105, and a first P-type heavily doped region 106. All doping is performed on the silicon waveguide.

[0004] Generally, the main ridge waveguide forms the first lightly doped P- and N-type region, and the light spot is mainly confined within it. Therefore, the doping concentration and carrier distribution of the first lightly doped P- and N-type region primarily determine the modulator's waveguide loss and modulation efficiency. Connected to the metal electrode 107 is the first heavily doped P- and N-type region. The doping concentration in these two regions is much higher than that in the first lightly doped P- and N-type region, aiming to reduce the contact resistance between the metal electrode 107 and the heavily doped P- and N-type region. The doping concentration of the medium-doped P- and N-type region falls between that of the lightly doped and heavily doped regions. By adjusting the doping concentration and length of the medium-doped P- and N-type region, the series resistance from the metal electrode 107 to the main modulation waveguide can be further reduced, while avoiding excessive waveguide light absorption loss due to doping.

[0005] As mentioned above, the modulation waveguide formed using the carrier dispersion effect has different resistances in different regions due to varying doping levels. Ultimately, the resistance of the entire waveguide is the sum of the equivalent resistances of these different regions, including the resistance of the first lightly doped P and N-type regions, the resistance of the first moderately doped P and N-type regions, the resistance of the first heavily doped P and N-type regions, and the contact resistance between the electrodes and the first heavily doped P and N-type regions, etc. The series resistance of the modulator has a significant impact on the electrical bandwidth of the modulator; the larger the series resistance, the greater the transmission loss of high-frequency signals, and the smaller the final bandwidth of the modulator.

[0006] Therefore, how to increase the modulation bandwidth by reducing the resistance value of the electro-optic modulator has become a problem.

[0007] In recent years, the rapidly developing data communication and AI cluster market has placed increasingly significant demands on high-speed, high-bandwidth transmission. Consequently, optical devices and modules are evolving towards single-wavelength speeds of 200Gbps and 400Gbps. Core optical modulators must possess sufficiently high bandwidth to meet these requirements. Summary of the Invention

[0008] The first objective of this invention is to provide a silicon photonic modulator that achieves the goals of reducing modulator resistance and increasing bandwidth, and by controlling structural parameters, improves the modulation efficiency of the modulator and reduces light absorption loss.

[0009] The technical solution adopted is as follows: A silicon photonic modulator includes a first planar region structure and a second planar region structure, wherein the second planar region structure is disposed on the ridge waveguide of the modulator and is located above the first planar region structure.

[0010] A further optimization of the technical solution of the present invention involves growing a silicide thin layer on the upper surface of the second plate region structure to further reduce the resistance of the modulation region.

[0011] A further preferred embodiment of the technical solution of the present invention is that the second plate region structure is an N-type doped region of the second plate region and a P-type doped region of the second plate region; The N-type doped region of the second plate region is composed of a second N-type lightly doped region, a second N-type moderately doped region, and a second N-type heavily doped region; wherein, the second N-type lightly doped region is connected to the second N-type lightly doped region within the structure of the first plate region, and the second N-type heavily doped region is connected to the first N-type heavily doped region within the structure of the first plate region. The P-type doped region of the second plate region consists of a second lightly doped P-type region, a second moderately doped P-type region, and a second heavily doped P-type region; wherein, the second lightly doped P-type region is connected to the first lightly doped P-type region within the structure of the first plate region, and the second heavily doped P-type region is connected to the first heavily doped P-type region within the structure of the first plate region.

[0012] A further optimization of the technical solution of the present invention involves growing a thin silicide layer I on the upper surface of the N-type doped region of the second planar region structure and a thin silicide layer II on the upper surface of the P-type doped region of the second planar region structure, thereby further reducing the modulation region resistance.

[0013] In a further preferred embodiment of the technical solution of the present invention, the parameters of the first and second planar region structures include height, width, and doping concentration. By controlling the parameters of the first and second planar region structures, not only can the resistance of the modulation region be reduced, but the modulation efficiency can also be improved and the light absorption loss reduced.

[0014] A second objective of this invention is to provide an optical device that employs the aforementioned silicon photonic modulator.

[0015] Further preferred, the optical device is a Mach-Zehnder modulator, a micro-ring modulator, or a combination of a Mach-Zehnder modulator and a micro-ring modulator.

[0016] A third objective of this invention is to provide an optical module that employs the aforementioned optical devices.

[0017] The advantages of this invention compared to the prior art are as follows: 1. The silicon photonic modulator of the present invention adds a second planar region structure, which greatly reduces the series resistance of the modulation region.

[0018] 2. The silicon photonic modulator of the present invention can reduce the resistance of the modulation region and improve the modulation efficiency and reduce the light absorption loss by controlling the parameters (height, width and doping concentration) of the first and second planar regions.

[0019] 3. The silicon photonic modulator of the present invention adds a silicide thin layer to the second planar region structure to further reduce the resistance of the modulation region. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the cross-section of an existing silicon photonic modulator carrier dissipation type PN-type doped structure; Figure 2 This is a schematic cross-sectional view of a PN-type doped structure of a silicon photonic modulator according to Embodiment 1 of the present invention; Figure 3 This is a simulation diagram showing the effect of changes in h2 and h3 on the modulation efficiency of the silicon photonic modulator in Embodiment 1 of the present invention. Figure 4 This is a simulation diagram showing the effect of changes in h2 and h3 on the optical absorption loss of the silicon photonic modulator in Embodiment 1 of the present invention. Figure 5 This is a schematic cross-sectional view of a PN-type doped structure of a silicon photonic modulator according to Embodiment 2 of the present invention; Wherein, A - silicon substrate, B - silicon dioxide buried layer, C - silicon dioxide capping layer, D - first planar region structure, E - second planar region structure, 101 - first N-type lightly doped region, 102 - first N-type medium doped region, 103 - first N-type heavily doped region, 104 - first P-type lightly doped region, 105 - first P-type medium doped region, 106 - first P-type heavily doped region, 107 - metal electrode, 201 - second N-type lightly doped region, 202 - second N-type medium doped region, 203 - second N-type heavily doped region, 204 - second P-type lightly doped region, 205 - second P-type medium doped region, 206 - second P-type heavily doped region, 301 - silicide thin layer I, 302 - silicide thin layer II. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-5 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Example 1

[0023] This embodiment describes a silicon photonic modulator, which reduces the modulator's resistance and increases the modulation bandwidth. Taking a silicon photonic carrier dissipation type PN modulator as an example... Figure 2 As shown. The modulator in this embodiment includes a first planar region structure D and a second planar region structure E.

[0024] like Figure 2 As shown, the modulator in this embodiment includes a silicon substrate A, a silicon dioxide buried layer B, a silicon dioxide capping layer C, a metal electrode 107, a first N-type lightly doped region 101, a first N-type moderately doped region 102, a first N-type heavily doped region 103, a first P-type lightly doped region 104, a first P-type moderately doped region 105, and a first P-type heavily doped region 106; all doping is performed on a silicon waveguide. The planar waveguide portions of the first N-type lightly doped region 101, the first N-type moderately doped region 102, and the first N-type heavily doped region 103 constitute the N-type doped region of the first planar region; the planar waveguide portions of the first P-type lightly doped region 104, the first P-type moderately doped region 105, and the first P-type heavily doped region 106 constitute the P-type doped region of the first planar region.

[0025] In this embodiment, the modulator has a second planar region structure E above the ridge waveguide. Specifically, the silicon waveguide above the ridge waveguide is doped. This doping process is the same as the doping process of the first planar region structure D, and both are known techniques to those skilled in the art.

[0026] Above the first planar region structure D, a second N-type lightly doped region 201, a second N-type moderately doped region 202, a second N-type heavily doped region 203, a second P-type lightly doped region 204, a second P-type moderately doped region 205, and a second P-type heavily doped region 206 are formed by doping.

[0027] The second N-type lightly doped region 201, the second N-type moderately doped region 202, and the second N-type heavily doped region 203 constitute the N-type doped region of the second planar region. The second N-type lightly doped region 201 needs to be connected to the first N-type lightly doped region 101, and the second N-type heavily doped region 203 needs to be connected to the first N-type heavily doped region 103. The second P-type lightly doped region 204, the second P-type moderately doped region 205, and the second P-type heavily doped region 206 constitute the P-type doped region of the second planar region. The second P-type lightly doped region 204 is connected to the first P-type lightly doped region 104, and the second P-type heavily doped region 206 is connected to the first P-type heavily doped region 106.

[0028] For the N-type doped region of the second planar region, the doping concentration needs to satisfy the following conditions: the doping concentration of the second heavily doped N-type region 203 is sufficiently large; the contact resistance between the second heavily doped N-type region 203 and the first heavily doped N-type region 103 is sufficiently small; the doping concentration of the second lightly doped N-type region 201 is constant, ensuring that the contact resistance between the second lightly doped N-type region 201 and the first lightly doped N-type region 101 is not large, while also not significantly increasing the optical transmission loss; the doping concentration of the second moderately doped N-type region 202 is between these two conditions. Therefore, in the silicon photonic modulator of this embodiment, the doping concentration of the N-type doped region of the second planar region is as follows: the doping concentration of the second heavily doped N-type region 203 is relatively large; the doping concentration of the second moderately doped N-type region 202 is between the doping concentration of the second heavily doped N-type region 203 and the doping concentration of the second lightly doped N-type region 201; and the doping concentration of the second lightly doped N-type region 201 is relatively low. The doping concentration of the second N-type heavily doped region 203 is close to that of the first N-type heavily doped region 103, and the doping concentration of the second N-type lightly doped region 201 is close to that of the first N-type lightly doped region 101.

[0029] Based on the same principle, the doping distribution of the P-type doped region is the same as that of the N-type: the doping concentration of the second heavily doped P-type region 206 is relatively high; the doping concentration of the second P-type doped region 205 is between that of the second heavily doped P-type region 206 and the second lightly doped P-type region 204; and the doping concentration of the second lightly doped P-type region 204 is relatively low. The doping concentration of the second heavily doped P-type region 206 is close to that of the first heavily doped P-type region 106, and the doping concentration of the second lightly doped P-type region 204 is close to that of the first lightly doped P-type region 104.

[0030] In existing silicon photonic modulators, the series resistance mainly originates from the first planar region structure. However, in this embodiment, the second planar region structure E is connected to the heavily doped portion of the first planar region structure D. The added second planar region structure E effectively adds a small parallel resistor to the first planar region structure D, significantly reducing the overall resistance of the modulation region. For example... Figure 2 As shown.

[0031] Introducing the second planar region structure E reduces the modulation efficiency and optical absorption loss of the silicon photonic modulator in this embodiment, thereby reducing the height h2 of the first planar region structure. It is known that in commonly used silicon photonic modulator waveguide structures in the prior art, the ridge waveguide height h1 is 220 nm, and the height h2 of the first planar region structure D is 90 nm.

[0032] like Figure 3 and Figure 4According to simulations, when the height h2 of the first planar region structure D is less than 70 nm and the height h3 of the second planar region structure E is less than 70 nm, the modulator structure of this embodiment has higher modulation efficiency and lower light absorption loss compared to conventional modulator structures.

[0033] The silicon optical modulator of this invention, with its added second planar region structure, is not limited to the doping structure of the modulator waveguide itself, except... Figure 2 The carrier dissipation PN doped structure, carrier injection PIN structure, and carrier aggregation effect MOS capacitor structure shown are also applicable.

[0034] Example 2

[0035] In this embodiment, a silicide thin layer is grown on the upper surface of the second plate region structure in Embodiment 1 to further reduce the overall resistance of the modulation region.

[0036] like Figure 5 As shown, a silicide thin layer I 301 is grown on the upper surface of the N-type doped region of the second planar region structure, and a silicide thin layer II 302 is grown on the upper surface of the P-type doped region of the second planar region structure. This further reduces the overall resistance of the modulation region. The principle behind this reduction is that both the first and second planar region structures are composed of N-type and P-type doped regions, which are equivalent to planar region resistance and constitute the main component of the modulator's series resistance. Silicide is a compound formed by silicon and metal or half-metal elements, commonly used to form low-resistance contacts between metals and semiconductors. The silicide thin layer has low resistance, and its contact with doped silicon reduces the overall resistance of the planar region and the silicide thin layer.

[0037] The thin-layer growth in this embodiment is also compatible with CMOS processes.

[0038] Example 3

[0039] An optical device employs a modulation structure with an added second planar region. The optical device can be a Mach-Zehnder modulator, a micro-ring modulator, or a combination of both. High-speed Mach-Zehnder modulators often use traveling-wave electrodes as the transmission lines for the modulation signal, with the optical wave and the electrical modulation signal propagating in the same direction within the modulator. Reducing the PN junction resistance of the modulator waveguide is equivalent to reducing the high-frequency electrical losses caused by the additional RC load on the transmission line, thus improving the overall electro-optic bandwidth characteristics of the modulator. For a micro-ring modulator, its equivalent circuit is similar to an RC load circuit. Reducing the PN junction resistance of the modulator waveguide increases the RC bandwidth of the device, thereby increasing the overall bandwidth of the modulator.

[0040] Example 4

[0041] An optical module, wherein the optical device of embodiment 3 is used.

[0042] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon photonic modulator, comprising a first planar region structure (D), characterized in that, The silicon photonic modulator also includes a second planar region structure (E), which is disposed on the ridge waveguide of the modulator and is located above the first planar region structure (D).

2. The silicon photonic modulator according to claim 1, characterized in that, A thin layer of silicide is grown on the upper surface of the second plate region structure (E).

3. The silicon photonic modulator according to claim 1, characterized in that, The second plate region structure (E) consists of the N-type doped region of the second plate region and the P-type doped region of the second plate region; The N-type doped region of the second plate region is composed of a second N-type lightly doped region (201), a second N-type mediumly doped region (202), and a second N-type heavily doped region (203); wherein, the second N-type lightly doped region (201) is connected to the first N-type lightly doped region (101) in the structure of the first plate region, and the second N-type heavily doped region (203) is connected to the first N-type heavily doped region (103) in the structure of the first plate region. The P-type doped region of the second plate region is composed of a second lightly doped P-type region (204), a second moderately doped P-type region (205), and a second heavily doped P-type region (206); wherein, the second lightly doped P-type region (204) is connected to the first lightly doped P-type region (104) in the structure of the first plate region, and the second heavily doped P-type region (206) is connected to the first heavily doped P-type region (106) in the structure of the first plate region.

4. The silicon photonic modulator according to claim 3, characterized in that, A thin layer of silicide I (301) is grown on the upper surface of the N-type doped region of the second plate region structure, and a thin layer of silicide II (302) is grown on the upper surface of the P-type doped region of the second plate region structure.

5. The silicon photonic modulator according to claim 1, characterized in that, The parameters of the first plate region structure (D) and the second plate region structure (E) include height, width, and doping concentration.

6. An optical device, characterized in that, The silicon photonic modulator described in any one of claims 1-5 is used.

7. The optical device according to claim 6, characterized in that, The optical device is a Mach-Zehnder modulator, a micro-ring modulator, or a combination of a Mach-Zehnder modulator and a micro-ring modulator.

8. An optical module, characterized in that, The optical module uses the optical device described in any one of claims 6 and 7.

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