JP6560153B2 - Optical module and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical module including an optical waveguide element and a photodiode used in the field of optical communication, and a method for manufacturing the same.

  With the recent widespread use of broadband access for the purpose of distributing large-capacity content and the like, there has been a demand for further increase in ultrahigh-speed and large-capacity signal transmission capability of optical fiber communication systems and further reduction in power consumption. In order to meet this demand, digital coherent optical communication that transmits light phase information as a signal is now widely used in addition to a light intensity transmission method that transmits light intensity as a signal. In these high-speed, large-capacity, low-power-consumption optical communication systems, it is indispensable to develop optoelectronic integration technology that integrates the functions of optical components and electrical components. For this reason, the development of compact optoelectronic integration technology using silicon photonics, which has good light-electron fusion and is advantageous for low power consumption, is in progress.

  The basic optical component of silicon photonics optoelectronic integration technology is composed of a silicon (Si) -based optical waveguide and a germanium (Ge) photodiode. So far, small optical modules have been developed in which a silicon-based optical waveguide and a silicon-rich quartz-based material, SiOx, and a germanium photodiode are monolithically integrated on the same substrate. Application to a communication system has begun.

Japanese Patent No. 576754

However, the integrated module of the SiO _x optical waveguide and the germanium photodiode has the following problems. First, since SiO _x is silicon-rich, the refractive index can be made higher than that of quartz (SiO 2), and an optical waveguide with strong optical confinement can be made, so that the module can be miniaturized. However, the control of the refractive index of SiO _x requires delicate control of the amount of silicon. Therefore, if SiO _x with a higher refractive index is applied to the optical waveguide in order to reduce the size, it is difficult to control because the refractive index changes due to a small change in the amount of silicon. Could cause problems.

There is a proposal to use silicon oxynitride (SiON) with good refractive index control instead of SiO _{x as} an optical waveguide core, but in the conventional manufacturing method, silicon oxynitride film containing N cannot be used for germanium selective growth in germanium growth There was a problem.

Further, when monolithically integrated with a germanium photodiode, it is necessary to form SiO _x at a low temperature that does not damage germanium. Since SiO _x formed at such a low temperature contains hydrogen (H), it is a film. There is a problem in that OH groups are present, light absorption is present in the vicinity of 1470 nm derived from the OH groups, and the bottom of this absorption is applied to the communication wavelength band, which affects propagation loss. Even when silicon oxynitride is used as the optical waveguide core instead of SiO _x , absorption derived from hydrogen cannot be solved.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to make it possible to monolithically integrate an optical waveguide having a core made of silicon oxynitride and a germanium photodiode on the same substrate. And

  An optical module manufacturing method according to the present invention is an optical module manufacturing method in which a germanium photodiode, a silicon optical waveguide made of a silicon core, and a silicon oxynitride optical waveguide made of a silicon oxynitride core are connected in this order, Forming a lower clad layer made of silicon oxide on the substrate; forming a silicon layer on the lower clad layer; patterning the silicon layer to form a lower silicon pattern in the first region; Forming a silicon core in a second region continuous with the one region; forming a first silicon oxynitride layer made of silicon oxynitride on the lower cladding layer so as to cover the lower silicon pattern and the silicon core; Forming a silicon oxide layer made of silicon oxide on the first silicon oxynitride layer; Forming an opening on the lower silicon pattern of the silicon oxide layer and the first silicon oxynitride layer, and selectively growing germanium on the lower silicon pattern at the bottom of the opening using the silicon oxide layer as a selective growth mask; Forming a germanium pattern, forming a germanium photodiode composed of the lower silicon pattern and the germanium pattern, removing the silicon oxide layer, removing the silicon oxide layer, and then removing the silicon oxide layer on the first silicon oxynitride layer. Forming a second silicon oxynitride layer made of silicon oxynitride on the substrate, and patterning the first silicon oxynitride layer and the second silicon oxynitride layer to form a second region continuous from the second region to the second region. Forming a silicon oxynitride core over three regions, a germanium photodiode, Rikonkoa, and and forming an upper clad layer made of silicon oxide on the silicon oxynitride core.

In the optical module manufacturing method, the first silicon oxynitride layer and the second silicon oxynitride layer may be formed by an ECR plasma CVD method using SiD ₄ , O ₂ , and N ₂ as source gases.

  In the method for manufacturing an optical module, the total thickness of the first silicon oxynitride layer and the silicon oxide layer on the lower silicon pattern is the same as the thickness of the germanium pattern, and the second silicon oxynitride layer is The second silicon oxynitride layer may be formed thicker than the silicon nitride layer, and the refractive index of the second silicon oxynitride layer may be equal to or lower than the refractive index of the first silicon oxynitride layer.

An optical module according to the present invention includes a silicon substrate, a lower cladding layer made of silicon oxide formed on the silicon substrate, a germanium photodiode formed in a first region on the lower cladding layer, and a lower cladding layer A silicon core formed in a second region continuous with the first region, a silicon oxynitride core formed from a part of the second region to a third region continuous with the second region, a germanium photodiode, The germanium photodiode includes a silicon core and an upper clad layer made of silicon oxide formed on the silicon oxynitride core. The germanium photodiode is formed on the lower silicon pattern and the lower silicon pattern continuously formed on the silicon core. Germanium photodiode, silicon composed of germanium pattern formed A silicon optical waveguide made of silicon and a silicon oxynitride optical waveguide made of a silicon oxynitride core are connected in this order. A silicon nitride layer and a second silicon oxynitride layer made of silicon oxynitride and stacked on the first silicon oxynitride layer.

In the optical module, the second silicon oxynitride layer is thicker than the first silicon oxynitride layer, the refractive index of the second silicon oxynitride layer, that is less than the refractive index of the first silicon oxynitride layer.

  In the above optical module, hydrogen contained in the first silicon oxynitride layer and the second silicon oxynitride layer may be deuterium.

  As described above, according to the present invention, it is possible to obtain an excellent effect that an optical waveguide having a core made of silicon oxynitride and a germanium photodiode can be monolithically integrated on the same substrate.

FIG. 1 is a cross-sectional view (a) and a plan view (b) showing a configuration of an optical module according to an embodiment of the present invention. FIG. 2A is a configuration diagram showing a state in each step for explaining the method of manufacturing an optical module in the embodiment of the present invention. FIG. 2B is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2C is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2D is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2E is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2F is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2G is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2H is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2I is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention. FIG. 2J is a configuration diagram showing a state in each step for explaining the method of manufacturing the optical module in the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view (a) and a plan view (b) showing a configuration of an optical module according to an embodiment of the present invention.

This optical module includes a silicon substrate 100, a lower cladding layer 101 made of silicon oxide (SiO ₂ ) formed on the silicon substrate 100, and a germanium photo formed in a first region 110 on the lower cladding layer 101. A diode 110a, a silicon core 121 formed in a second region 120 continuous with the first region 110 on the lower cladding layer 101, and a third region 130 continuous from the second region 120 to the second region 120. And a silicon oxynitride core 122 formed in the middle.

Further, an upper cladding layer 103 made of silicon oxide (SiO ₂ ) formed on the germanium photodiode 110 a, the silicon core 121, and the silicon oxynitride core 122 is provided. Further, an intermediate cladding layer 123 is provided which is continuous to the silicon oxynitride core 122 and is disposed below the upper cladding layer 103 in the silicon core 121 formation region.

  The germanium photodiode 110a includes a first conductivity type lower silicon pattern 111 formed continuously on the silicon core 121, a non-doped (i-type) germanium pattern 112 formed on the lower silicon pattern 111, and a germanium pattern. And an upper silicon pattern 113 of the second conductivity type formed on 112. For example, the first conductivity type may be p-type and the second conductivity type may be n-type.

  Here, the silicon oxynitride core 122 is characterized in that it includes a first silicon oxynitride layer 141 and a second silicon oxynitride layer 142. The intermediate cladding layer 123 is also composed of a first silicon oxynitride layer 141 and a second silicon oxynitride layer 142. Both the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 are made of silicon oxynitride, and the second silicon oxynitride layer 142 is stacked on and in contact with the first silicon oxynitride layer 141.

In the formation region (formation layer) of the second silicon oxynitride layer 142, the side surface of the germanium pattern 112 constituting the germanium photodiode 110a is covered with the side wall layer 124 made of silicon oxide (SiO ₂ ). Note that the first silicon oxynitride layer 141 is a layer formed by depositing silicon oxynitride before forming the germanium photodiode 110a. On the other hand, the second silicon oxynitride layer 142 is a layer formed by depositing silicon oxynitride after forming the germanium photodiode 110a.

  For example, the lower cladding layer 101 is formed with a thickness of about 3 μm, and the upper cladding layer 103 is formed with a thickness of about 5 μm. The silicon core 121 has a cross section with a width of about 300 to 600 nm and a height of about 200 to 300 nm. The silicon oxynitride core 122 has a cross section with a width of about 3 μm and a height of about 3 μm. The first silicon oxynitride layer 141 is formed to a thickness of about 200 to 500 nm, and the second silicon oxynitride layer 142 is formed to a thickness of about 2.5 to 2.8 μm. In addition, the silicon optical waveguide in the second region 120 by the silicon core 121 has an optical waveguide length of about 200 to 500 nm.

  The germanium pattern 112 has an overall thickness of about 1 μm. The germanium photodiode 110a is formed in a rectangular shape of about 10 × 50 μm in plan view. The germanium pattern 112 may be composed of, for example, an i-type lower germanium layer and a second conductivity type upper germanium layer.

  The optical module described above is monolithically formed on the silicon substrate 100 in a state where a germanium photodiode 110a, a silicon optical waveguide composed of a silicon core 121, and an optical waveguide composed of a silicon oxynitride core 122 are connected in this order. .

  Although not shown, a contact wiring that penetrates the upper cladding layer 103, the first silicon oxynitride layer 141, and the second silicon oxynitride layer 142 and is connected to the lower silicon pattern 111 is provided. Further, a contact wiring that penetrates through the second silicon oxynitride layer 142 and the upper cladding layer 103 on the upper silicon pattern 113 and is connected to the upper silicon pattern 113 is provided.

  In this optical module, first, the light guided through the optical waveguide in the third region 130 by the silicon oxynitride core 122 has a higher refractive index in the silicon core 121 in the region covered with the silicon oxynitride core 122. The silicon optical waveguide made of the silicon core 121 can be transferred. Next, the light guided through the silicon optical waveguide can be absorbed by the germanium pattern 112 having a higher refractive index on the lower silicon pattern 111 continuous to the silicon core 121.

  Thus, according to the embodiment, the light guided through the optical waveguide by the silicon oxynitride core 122 can be photoelectrically converted by the germanium photodiode 110a. Since germanium has high light receiving sensitivity in the communication wavelength band of 1.3 to 1.6 μm, monolithic integration of the optical waveguide device and germanium photodiode on the same substrate by the silicon oxynitride core 122 is small and highly functional. It is very effective for realizing the optical module for communication.

  Next, the manufacturing method of the optical module in embodiment of this invention is demonstrated using FIG. 2A-FIG. 2J. 2A to 2J are configuration diagrams showing states in respective steps for explaining a method of manufacturing an optical module according to an embodiment of the present invention. 2A to 2J schematically show cross sections.

First, as shown in FIG. 2A, a lower clad layer 101 made of SiO ₂ is formed on a silicon substrate 100, and a silicon layer 201 is formed on the lower clad layer 101. This can be obtained by using a well-known SOI (Silicon on Insulator) substrate. The SOI substrate is a substrate in which a surface silicon layer is formed on a silicon base via a buried insulating layer. The silicon base portion becomes the silicon substrate 100, the buried insulating layer becomes the lower cladding layer 101, and the surface silicon layer becomes the silicon layer 201.

  Next, the silicon layer 201 is patterned to form a lower silicon pattern 111 and a silicon core 121 as shown in FIG. 2B. The lower silicon pattern 111 and the silicon core 121 are continuously and integrally formed. For example, each of the above patterns can be formed by selectively etching with an etching technique using a mask pattern formed by well-known photolithography. Note that the mask pattern is removed after pattern formation. Further, impurities are introduced into the lower silicon pattern 111 by selective ion implantation or the like to obtain the first conductivity type. For example, it may be p-type.

  Next, as shown in FIG. 2C, a first silicon oxynitride layer 141 is formed on the lower cladding layer 101 so as to cover the lower silicon pattern 111 and the silicon core 121. For example, the first silicon oxynitride layer 141 may be formed by depositing silicon oxynitride by a plasma CVD method. Next, as shown in FIG. 2D, a silicon oxide layer 202 made of silicon oxide is formed on the first silicon oxynitride layer 141. For example, the silicon oxide layer 202 may be formed by depositing silicon oxide by a plasma CVD method. Here, the total thickness of the first silicon oxynitride layer 141 and the silicon oxide layer 202 on the lower silicon pattern 111 is preferably the same as the thickness of a germanium pattern described later. After the growth of the germanium pattern, the step structure is relaxed, and it becomes easy to form a silicon layer and an upper silicon pattern which will be described later.

  Next, as shown in FIG. 2E, an opening 202a and an opening 151a are formed in the silicon oxide layer 202 and the first silicon oxynitride layer 141 corresponding to the upper part of the lower silicon pattern 111. For example, the opening 202a and the opening 151a can be formed by selectively etching with an etching technique using a mask pattern formed by well-known photolithography. The opening 202a and the opening 151a are formed so that the upper surface of the lower silicon pattern 111 is exposed at the bottom of the opening 151a. Note that the mask pattern is removed after the opening 202a and the opening 151a are formed.

Next, as shown in FIG. 2F, germanium is selectively grown on the lower silicon pattern 111 at the bottom of the opening 151a using the silicon oxide layer 202 as a selective growth mask to form a germanium pattern 112. For example, germanium is selectively deposited on the upper surface of the lower silicon pattern 111 exposed at the bottom of the opening 151a by depositing germanium at a substrate temperature condition of 600 ° C. by a thermal CVD method using GeH ₄ as a source gas. Can be deposited. In this selective growth, germanium is not deposited on the silicon oxide layer 202. Further, as described above, since the total thickness of the first silicon oxynitride layer 141 and the silicon oxide layer 202 on the lower silicon pattern 111 is the same as the thickness of the germanium pattern 112, the silicon oxide layer 202 And the upper surface of the germanium pattern 112 is in a flat state.

  Next, as shown in FIG. 2G, a silicon layer 203 is formed on the silicon oxide layer 202 including the portion of the germanium pattern 112. Next, impurities are introduced into the silicon layer 203 by ion implantation to obtain the second conductivity type. For example, n-type. At this time, the impurity may be introduced into part of the germanium pattern 112, and the upper layer portion of the germanium pattern 112 may be n-type. For example, the thickness of the upper layer portion of the second conductivity type can be changed by controlling the ion energy in the ion implantation. As described above, the characteristics of the germanium photodiode 110a can be changed by changing the thickness of the upper layer portion of the germanium pattern 112 which is the second conductivity type.

  Next, the silicon layer 203 is patterned, and the silicon oxide layer 202 is removed to form a second conductivity type upper silicon pattern 113 on the germanium pattern 112 as shown in FIG. 2H. In the removal of the silicon oxide layer 202, the side wall layer 124 is formed on the side surface of the germanium pattern 112 by leaving the lower region of the upper silicon pattern 113 on the side of the germanium pattern 112.

  First, the silicon layer 203 is patterned by etching using a mask pattern (not shown) formed by a known lithography technique as a mask to form an upper silicon pattern 113. Etching may be performed, for example, by reactive ion etching (RIE). According to RIE capable of processing with high vertical anisotropy, the upper silicon pattern 113 can be formed in a desired size and shape. The upper silicon pattern 113 has a larger area than the germanium pattern 112 in plan view. Further, the germanium pattern 112 is arranged inside the upper silicon pattern 113 in plan view.

  Subsequently, the silicon oxide layer 202 is removed by dry etching (RIE). As described above, since the upper silicon pattern 113 is formed in an area larger than the germanium pattern 112 in plan view, the silicon oxide layer 202 remains around the germanium pattern 112, and this portion becomes the sidewall layer 124.

  As described above, by forming the upper silicon pattern 113, the germanium photodiode 110a including the lower silicon pattern 111, the germanium pattern 112, and the upper silicon pattern 113 is formed. If the upper layer portion of the germanium pattern 112 is of the second conductivity type, the upper silicon pattern 113 is not necessary. If the upper layer portion of the germanium pattern 112 is n-type, the lower silicon pattern 111 has a pin structure and functions as a photodiode. In this case, an electrode is connected to the upper layer portion of the germanium pattern 112.

  Next, as shown in FIG. 2I, a second silicon oxynitride layer 142 is formed on the first silicon oxynitride layer 141. For example, the second silicon oxynitride layer 142 may be formed by depositing silicon oxynitride by a plasma CVD method. In this case, the second silicon oxynitride layer 142 is also formed on the upper silicon pattern 113. According to the embodiment, since the side surface of the germanium pattern 112 is covered with the sidewall layer 124, hydrogen is suppressed from entering the germanium pattern 112 when the second silicon oxynitride layer 142 is formed.

  Next, by patterning the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142, the silicon oxynitride core 122 is formed from a part of the second region 120 to the third region 130 continuous to the second region 120. Form. For example, the silicon oxynitride core 122 is formed by selectively etching the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 by an etching technique using a mask pattern formed by well-known photolithography. do it.

Further, the upper clad layer 103 made of SiO ₂ is formed on the germanium photodiode 110a, the silicon core 121, and the silicon oxynitride core 122 (FIG. 2J). In forming the upper clad layer 103, it is important to set the film formation temperature to 300 ° C. or lower in order not to cause thermal damage to the already formed germanium photodiode 110a. For example, according to the CVD method using electron cyclotron resonance (ECR) plasma, the upper cladding layer 103 can be formed by depositing SiO ₂ while satisfying the above-described conditions.

  As described above, the germanium photodiode 110a, the silicon optical waveguide composed of the silicon core 121, and the optical waveguide composed of the silicon oxynitride core 122 are connected in this order. Thereafter, although not shown, a contact wiring that penetrates the upper cladding layer 103, the first silicon oxynitride layer 141, and the second silicon oxynitride layer 142 and connects to the lower silicon pattern 111, and the upper cladding layer 103 are formed. A contact wiring that penetrates and connects to the upper silicon pattern 113 is formed.

  Here, in the formation of the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 described above, the following is important.

  First, when hydrogen H is present in the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142, an NH group is generated, and the NH group has absorption in the 1.5 μm band which is a communication wavelength, so that an optical waveguide is formed. Disturb. Therefore, it is important that the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 do not contain H.

  Second, it is important to form the second silicon oxynitride layer 142 at a temperature condition of 300 ° C. or lower in order not to thermally damage the germanium photodiode 110a that has already been formed.

In order to satisfy the above two conditions, the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 include deuterium silane (SiD ₄ ), oxygen (O ₂ ), and nitrogen (N ₂ ) obtained by deuterating hydrogen. ) And a source gas, and a CVD method using ECR plasma is used. According to ECR plasma CVD, hydrogen H having a desired refractive index in a wide range of 1.45 to 2.0 in a gas system of SiD ₄ , O ₂ , and N ₂ due to high gas decomposition efficiency. A silicon oxynitride film which does not contain can be formed. In addition, since the ECR plasma CVD has high gas decomposition efficiency, a high-quality silicon oxynitride film can be formed on the substrate without heating the substrate.

By using SiD ₄ gas in the CVD method using ECR plasma, a silicon oxynitride film that does not contain hydrogen H can be formed even at a low temperature. Thus, the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 that do not provide the same can be formed. Since SiD ₄ gas is used, deuterium is included in the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142, but deuterium does not cause loss in light propagation in the communication wavelength band. It has the characteristic that there is no influence on.

  The first silicon oxynitride layer 141 has a thickness of about 0.3 μm, and the second silicon oxynitride layer 142 has a thickness of about 2.7 μm. However, the second silicon oxynitride layer 142 has a thickness of about 2.7 μm. It is desirable to make it thick enough. By sufficiently thickening the second silicon oxynitride layer 142 formed after the germanium growth, the characteristics of the optical waveguide by the silicon oxynitride core 122 are determined by the second silicon oxynitride layer 142 and are composed of two silicon oxynitride layers. The influence that was done can be eliminated.

  Further, by making the first silicon oxynitride layer 141 thinner, the surface step structure can be reduced to the germanium growth step, and thus there is a manufacturing advantage that the integrated fabrication is easy. Ideally, the first silicon oxynitride layer 141 and the second silicon oxynitride layer 142 have the same refractive index, but a layer having a refractive index lower than that of silicon is laminated to form a core, and low loss coupling of the optical waveguide is achieved. As long as the refractive index of the thicker second silicon oxynitride layer 142 is slightly lower than that of the first silicon oxynitride 141, both of them may not have the same refractive index.

  According to the present embodiment, since the photodiode is made of germanium, the optical waveguide device composed of the silicon oxynitride core 122 and the photodiode are monolithically formed on the same substrate without mounting the photodiode later. Can be accumulated.

  In this embodiment, the core of the optical waveguide is composed of two stacked silicon oxynitride layers, and the silicon oxynitride layer is formed by forming before and after the formation of the germanium pattern constituting the photodiode. As a result, selective growth of germanium was made possible on the fabricated substrate, and as a result, monolithic integration of the silicon optical waveguide, the silicon oxynitride optical waveguide, and the germanium photodiode was realized.

  In addition, the silicon oxynitride core is composed of two silicon oxynitride layers, and the second silicon oxynitride layer as the second layer (upper layer) is subjected to a layer thickness change such as germanium selective growth and removal of the selection mask. Since it can be formed later, by adjusting the formation thickness of the second silicon oxynitride layer, the thickness of the silicon oxynitride core can be set to a desired value in a later process, and the manufacturing margin can be increased. is there.

In this embodiment, since the silicon oxynitride layer is formed by the ECR plasma CVD method using SiD ₄ gas, O _2, and N ₂ gas, oxynitride formed at a low temperature that does not damage germanium. Monolithic integration of silicon oxynitride optical waveguide and germanium photodiode with low loss in the communication wavelength band because there is no NH or OH group causing loss in the communication wavelength band because the silicon layer does not contain H. Can now.

  As described above, according to the present invention, it is possible to monolithically integrate a silicon oxynitride optical waveguide and a germanium photodiode on the same substrate, thereby realizing a small and high-performance optical module with a photodiode. An excellent effect is obtained.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above description, the upper cladding layer is made of silicon oxide deposited by the CVD method, but the present invention is not limited to this. For example, the cladding layer may be formed by depositing by sputtering. Silicon oxide can also be deposited by sputtering.

  Further, the lower clad layer may be formed by depositing instead of using an SOI substrate. Needless to say, the silicon core is not limited to single crystal silicon, but may be polycrystalline silicon or amorphous silicon.

  DESCRIPTION OF SYMBOLS 100 ... Silicon substrate, 101 ... Lower clad layer, 103 ... Upper clad layer, 110 ... 1st area | region, 110a ... Germanium photodiode, 111 ... Lower silicon pattern, 112 ... Germanium pattern, 113 ... Upper silicon pattern, 120 ... 2nd Region 121, silicon core 122, silicon oxynitride core 123, intermediate cladding layer 124, side wall layer 130, third region 141, first silicon oxynitride layer 142, second silicon oxynitride layer

Claims (5)

Germanium photodiode, silicon optical waveguide made of silicon core, silicon oxynitride optical waveguide made of silicon oxynitride core is an optical module manufacturing method in which these are connected in this order,
Forming a lower clad layer made of silicon oxide on a silicon substrate;
Forming a silicon layer on the lower cladding layer;
Patterning the silicon layer to form a lower silicon pattern in a first region, and forming the silicon core in a second region continuous with the first region;
Forming a first silicon oxynitride layer made of silicon oxynitride on the lower cladding layer covering the lower silicon pattern and the silicon core;
Forming a silicon oxide layer made of silicon oxide on the first silicon oxynitride layer;
Forming an opening above the lower silicon pattern of the silicon oxide layer and the first silicon oxynitride layer;
Using the silicon oxide layer as a selective growth mask, germanium is selectively grown on the lower silicon pattern at the bottom of the opening to form a germanium pattern, and the germanium photodiode comprising the lower silicon pattern and the germanium pattern Forming a step;
Removing the silicon oxide layer;
Forming a second silicon oxynitride layer made of silicon oxynitride on the first silicon oxynitride layer after removing the silicon oxide layer;
Forming the silicon oxynitride core from a part of the second region to a third region continuous to the second region by patterning the first silicon oxynitride layer and the second silicon oxynitride layer;
And a step of forming an upper clad layer made of silicon oxide on the germanium photodiode, the silicon core, and the silicon oxynitride core. In the manufacturing method of the optical module of Claim 1,
The first silicon oxynitride layer and the second silicon oxynitride layer are formed by an ECR plasma CVD method using SiD ₄ , O ₂ , and N ₂ as source gases. In the manufacturing method of the optical module of Claim 1 or 2,
The total thickness of the first silicon oxynitride layer and the silicon oxide layer on the lower silicon pattern is the same as the thickness of the germanium pattern,
The second silicon oxynitride layer is formed thicker than the first silicon oxynitride layer,
The method of manufacturing an optical module, wherein a refractive index of the second silicon oxynitride layer is equal to or lower than a refractive index of the first silicon oxynitride layer. A silicon substrate;
A lower clad layer made of silicon oxide formed on the silicon substrate;
A germanium photodiode formed in a first region on the lower cladding layer;
A silicon core formed in a second region continuous with the first region on the lower cladding layer;
A silicon oxynitride core formed from a part of the second region to a third region continuous to the second region;
An upper cladding layer made of silicon oxide formed on the germanium photodiode, the silicon core, and the silicon oxynitride core;
The germanium photodiode is composed of a lower silicon pattern formed continuously on the silicon core, and a germanium pattern formed on the lower silicon pattern,
The germanium photodiode, the silicon optical waveguide made of the silicon core, and the silicon oxynitride optical waveguide made of the silicon oxynitride core are formed in a state of being connected in this order,
The silicon oxynitride core is disposed on the silicon substrate side and includes a first silicon oxynitride layer made of silicon oxynitride and a second silicon oxynitride layer stacked on the first silicon oxynitride layer. Composed of a silicon oxynitride layer ,
The second silicon oxynitride layer is thicker than the first silicon oxynitride layer;
The optical module , wherein a refractive index of the second silicon oxynitride layer is not more than a refractive index of the first silicon oxynitride layer . In the optical module according to claim 4 Symbol mounting,
The optical module, wherein hydrogen contained in the first silicon oxynitride layer and the second silicon oxynitride layer is deuterium.

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