JP6808795B2 - Manufacturing method of optical device and optical device - Google Patents

Description

The present invention relates to a method for manufacturing an optical device and an optical device.

An optical device in which a waveguide and a laser diode are integrated on a substrate is known (see, for example, Non-Patent Document 1). The laser diode is mounted on a pedestal formed on a substrate in order to accurately match the height of the active layer with the height of the core layer of the waveguide.

Takanori Shimizu, 8 outsiders, "Multi-channel high-density hybrid integrated light source for inter-chip optical interconnection", IEICE Technical Report, December 16, 2011, Vol. 111, No. 359, p. 55-60

The optical axis of the waveguide may shift depending on the thickness of the upper clad layer of the waveguide. Even in such a case, it is required to optically couple the laser diode with the waveguide with high efficiency.

The present invention has been made in view of the above points, and one of the objects thereof is to provide an optical device capable of optically coupling a waveguide and an optical element (for example, a laser diode) with high efficiency. It is in.

In order to solve the above-mentioned problems, one aspect of the present invention includes a step of forming a waveguide on a substrate, a step of specifying the thickness of the upper clad layer of the formed waveguide, and optics on the substrate. In the step of forming the mounting surface, which includes a step of forming the mounting surface of the element and a step of mounting the optical element on the mounting surface, the mounting surface is adjusted to the thickness of the specified upper clad layer. It is a method for manufacturing an optical device, which is characterized in that it is formed at a height corresponding to the height.

In another aspect of the present invention, in the above aspect, in the step of forming the mounting surface, a predetermined relationship between the thickness of the upper clad layer and the height of the optical axis of the waveguide is used. , A method of manufacturing an optical device, characterized in that the mounting surface is formed at the height.

In another aspect of the present invention, in the above aspect, in the step of forming the mounting surface, the optical axis of the optical element is the light of the waveguide while the optical element is mounted on the mounting surface. This is a method for manufacturing an optical device, characterized in that the mounting surface is formed so as to be at the height of the shaft.

In another aspect of the present invention, in the above aspect, in the step of forming the mounting surface, the optical axis of the optical element is the light of the waveguide while the optical element is mounted on the mounting surface. A method for manufacturing an optical device, which comprises a step of adjusting the height of the mounting surface so as to be the height of the shaft.

In another aspect of the present invention, in the above aspect, the step of forming the mounting surface includes the step of etching the substrate, and the step of adjusting the height of the mounting surface is specified. A method for manufacturing an optical device, which comprises a step of adjusting the etching depth of the substrate according to the thickness of the upper clad layer.

In another aspect of the present invention, in the above aspect, the step of forming the mounting surface is interposed between the optical element and the substrate in a state where the optical element is mounted on the mounting surface. The step of adjusting the height of the mounting surface including the step of forming a film to be different on the substrate is a step of adjusting the film thickness according to the thickness of the specified upper clad layer. It is a method for manufacturing an optical device, which comprises.

In addition, another aspect of the present invention includes a substrate, a waveguide formed on the substrate, and an optical element mounted on a mounting surface formed on the substrate, and is provided with an upper cladding of the waveguide. The layer has a thickness such that the optical axis of the waveguide is located closer to the substrate side than the center of the core layer of the waveguide, and the mounting surface is such that the optical element is mounted on the mounting surface. The optical device is characterized in that the optical axis of the optical element is formed at a height such that it is located closer to the substrate side than the center of the core layer of the waveguide in the state.

According to the present invention, it is possible to optically couple the waveguide and the optical element with high efficiency.

It is a figure which showed the typical cross-sectional structure of the general optical device 100. It is a figure which showed the typical cross-sectional structure of the optical device 200 which concerns on one Embodiment of this invention. It is a figure which shows the field of light in the waveguide 202 of the optical device 200 which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the thickness of the upper clad layer 205 and the amount of decrease in the height of an effective optical axis of a waveguide 202. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a manufacturing process diagram of the optical device 200 which concerns on one Embodiment of this invention. It is a top view of the optical device 200 which shows the place where the height t ₁ and the film thickness t ₂ of a step are measured. It is a top view of the optical device 200 which shows the place where the monitor area 115 is provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a schematic cross-sectional configuration of a general optical device 100 having a waveguide and an optical element on a substrate. The optical device 100 includes a waveguide 102 formed on the substrate 101. The substrate 101 is a silicon (Si) substrate. The waveguide 102 includes a lower clad layer 103 formed on the silicon substrate 101, a core layer 104 formed on the lower clad layer 103, and an upper clad layer 105 formed on the core layer 104. .. The lower clad layer 103 is a SiO ₂ layer composed of an embedded oxide film layer (BOX layer). The core layer 104 is a silicon (Si) layer composed of an SOI (Silicon On Insulator). The waveguide 102 is formed by using an SOI substrate composed of a silicon substrate 101, a BOX layer, and an SOI layer. The upper clad layer 105 is composed of _two SiO layers.

The optical device 100 includes an optical element 106 mounted on a silicon substrate 101. The optical element 106 is mounted on a mounting surface formed by processing a part of the surface of the silicon substrate 101. The mounting surface is the upper surface of the pedestal 107 in which a part of the surface of the silicon substrate 101 is formed in a convex shape. A protective film 108 is formed on the upper surface of the pedestal 107. The protective film 108 is formed so as to cover the surface of the silicon substrate 101 including the upper surface of the pedestal 107, and the end surface and the upper surface of the waveguide 102. The optical element 106 is mounted on the pedestal 107 via a protective film 108, and is fixed to the silicon substrate 101 by a bonding agent 109 in a portion other than the pedestal 107.

The optical element 106 is a functional element that is optically coupled to the waveguide 102. An example of the optical element 106 is a light emitting element such as a laser diode. When the optical element 106 is a laser diode, the protective film 108 is an insulating film (for example, a SiO ₂ film) for insulating between the laser diode and the silicon substrate 101, and the bonding agent 109 is applied to the lower surface of the laser diode. It is a solder (for example, gold tin (AuSn) solder) for conducting the formed electrode (not shown) and the electrode (not shown) formed on the surface of the portion of the silicon substrate 101 other than the pedestal 107. When the protective film 108 is a SiO ₂ film, the protective film 108 has the effect of effectively thickening the upper clad layer 105 in the waveguide 102 portion. That is, the layer in which the upper clad layer 105 and the protective film 108 are combined functions as an effective upper clad layer. Hereinafter, the optical element 106 will be described as a laser diode.

The laser diode 106 has an active layer 106a. The laser diode 106 emits laser light from the active layer 106a. The laser beam emitted from the active layer 106a is incident on the core layer 104 of the waveguide 102. That is, the laser diode 106 and the waveguide 102 are optically coupled. The laser diode 106 is aligned so that the optical coupling efficiency between the laser diode 106 and the waveguide 102 is maximized. Specifically, the laser diode 106 is mounted on the silicon substrate 101 so that the height center of the active layer 106a coincides with the height center of the core layer 104 of the waveguide 102. In order to realize this, the height of the upper surface of the pedestal 107 is the height center of the active layer 106a of the laser diode 106 and the height center of the core layer 104 of the waveguide 102 in the state where the laser diode 106 is mounted. Is formed at a height that matches.

Here, for convenience, the height reference surface S is set at the boundary surface between the lower clad layer 103 and the silicon substrate 101 in the waveguide 102. The height difference between the upper surface of the reference plane S and the base 107 H, the thickness _{t LC} of the lower clad layer 103 of the waveguide 102, the thickness _{t C} of the core layer 104 of the waveguide 102, the laser diode 106 height _{h LD} from the bottom surface to the center of the active layer 106a, and the thickness of the protective film 108 and _{t SiO2,} the center of the core layer 104 of the waveguide 102 as measured from the reference plane S height _{H C,} a reference plane the height _{H LD} of the center of the active layer 106a of the laser diode 106 as measured from S, respectively,
_{H C = t LC + t C} / 2
H _LD = h _LD + t _SiO2- H
It is expressed as. The height H of the upper surface of the pedestal 107 that maximizes the optical coupling efficiency between the laser diode 106 and the waveguide 102 is determined from the condition of _HC = _HLD .
H = (h _LD + t _SiO2 )-(t _LC + t _C / 2) …… (1)
It is decided. Therefore, in the optical device 100 of FIG. 1, the height of the upper surface of the pedestal 107 is formed at the height H given by the equation (1).

<First Embodiment>
FIG. 2 is a diagram showing a schematic cross-sectional configuration of the optical device 200 according to the embodiment of the present invention. In the optical device 200, the thickness of the upper clad layer 205 is formed to be thinner than the thickness of the upper clad layer 105 in the optical device 100 of FIG. 1, and the height of the upper surface of the pedestal 207 is the height of the optical device 100 of FIG. It is different from the optical device 100 of FIG. 1 in that it is formed lower than the height of the upper surface of the pedestal 107 in FIG. Since the configurations of other parts of the optical device 200 are the same as those of the optical device 100 of FIG. 1, the description thereof will be omitted.

In the optical device 200, since the thickness of the upper clad layer 205 is formed to be thinner than the thickness of the upper clad layer 105 in the optical device 100 of FIG. 1, the effective optical axis of the waveguide 202 is the waveguide 202. It exists at a position lower than the height center of the core layer 104 of the above. In other words, the field of light propagating in the waveguide 202 of the optical device 200 is distributed offset to the lower clad layer 103 side, and the peak of the field is on the lower clad layer 103 side of the height center of the core layer 104. Is located in. This is because an air layer having a refractive index smaller than that of the upper clad layer 205 exists above the upper clad layer 205. That is, when the thickness of the upper clad layer 205 becomes thin, the refractive index above the core layer 104 is affected by the air layer. Then, as shown in FIG. 3, in the field of light, the spot size w ₂ on the upper clad layer 205 side becomes smaller than the spot size w ₁ on the lower clad layer 103 side, and the field distribution becomes asymmetric in the height direction. At the same time, the peak (optical axis) of the field shifts downward from the height center of the core layer 104.

In the optical device 200, the mounting height of the optical element (laser diode) 106 is adjusted so as to compensate for such a decrease in the height of the effective optical axis of the waveguide 202. Specifically, the laser diode 106 is mounted at a position lower than that of the laser diode 106 in the optical device 100 of FIG. 1 by the amount of decrease Δ of the effective optical axis height of the waveguide 202. In order to realize this, the height of the upper surface of the pedestal 207 of the optical device 200 is such that the height center of the active layer 106a of the laser diode 106 is the core layer 104 of the waveguide 102 in the state where the laser diode 106 is mounted. The height is formed so that it is lower than the center of the height by Δ. That is, the difference in height between the reference surface S in the optical device 200 of FIG. 2 and the upper surface of the pedestal 207 is H + Δ. The optical device 200 is configured so that the height of the upper surface of the pedestal 207 is formed to be lower than the reference surface S by H + Δ so that the optical coupling efficiency between the laser diode 106 and the waveguide 202 is maximized. There is.

The amount of decrease in the effective optical axis height of the waveguide 202 is the thickness t _UC of the upper clad layer 205 (or the thickness of the upper clad layer 205 and the protective film, which is the effective thickness of the upper clad layer. (SiO ₂ film) The sum of the thickness of 108 and t _UC + t _{SiO 2.} Hereinafter, the same shall apply when describing t _{UC in} relation to Δ). Specifically, as shown in FIG. 4, when the upper clad layer 205 is sufficiently thick, Δ is almost zero, but as the upper clad layer 205 becomes thinner, Δ becomes larger. The height of the upper surface of the base 207 of the optical device 200, by a height H + delta corresponding to the thickness t _UC of the upper cladding layer 205 is formed lower than the reference plane S. As a result, the optical coupling efficiency between the laser diode 106 and the waveguide 202 is maximized. Thus, in the optical device 200, the height of the upper surface of the base 207 is set to a height determined according to the thickness t _UC of the upper cladding layer 205.

The amount of decrease in the effective optical axis height Δ of the waveguide 202 may also change depending on the structure (type) of the waveguide 202. For example, in order to bring the shape of the light field in the active layer 106a of the laser diode 106 closer to the shape of the light field in the waveguide 202, the waveguide 202 is made into a spot size converter (SSC) type structure to expand the light field. and in the structure, dependence of Δ for the thickness t _UC of the upper cladding layer 205 becomes more pronounced.

5 to 16 are process diagrams showing a method of manufacturing the optical device 200 according to the embodiment of the present invention. Hereinafter, a method for manufacturing the optical device 200 will be described.

First, as shown in FIG. 5, a waveguide 202 is formed on the substrate. Specifically, an SOI substrate composed of a silicon substrate 101, a BOX layer 110, and an SOI layer 111 is prepared, and the SOI layer 111 is processed into a desired pattern by photolithography and etching to form a core layer 104. Further, the SiO ₂ layer 112 is formed on the core layer 104 and the BOX layer 110. The waveguide 202 is composed of the BOX layer 110, the core layer 104, and the SiO ₂ layer 112. The BOX layer 110 functions as a lower clad layer 103, and the SiO ₂ layer 112 functions as an upper clad layer 205.

Furthermore, to measure the thickness _{t UC} of the SiO ₂ layer 112 was formed (upper cladding layer 205). For example, the thickness of the BOX layer 110 before depositing the SiO ₂ layer 112 was measured by the interference type film thickness meter, and the BOX layer 110 in a portion away from the core layer 104 after forming the SiO ₂ layer 112 SiO the combined thickness of the _two layers 112 measured by the interference type film thickness meter, from the difference between them can be determined thickness _{t UC} of the SiO ₂ layer 112 (upper cladding layer 205). Alternatively, it may also be determined thickness _{t UC} of the SiO ₂ layer 112 (upper cladding layer 205) from the deposition rate and the deposition time when forming the SiO ₂ layer 112.

Next, as shown in FIG. 6, the resist layer 113 is formed on the upper part of the waveguide 202 by photolithography.

Next, as shown in FIG. 7, the resist layer 113 is used as a mask to etch the SiO ₂ layer 112 to the silicon substrate 101. The etching depth is such that the height from the boundary surface (reference surface S) between the lower clad layer 103 and the silicon substrate 101 to the etching surface is H given by the above equation (1). That is, the etching depth is controlled so that the silicon substrate 101 is etched by the depth H. For etching, anisotropic etching such as RIE (reactive ion etching) is applied so that the end face of the waveguide 202 exposed by etching becomes a vertical plane. Further, different etching gases may be applied to the etching of the SiO ₂ layer 112 and the BOX layer 110 and the etching of the silicon substrate 101. Instead of etching the silicon substrate 101 by the depth H, the etching surface is monitored by an interference type film thickness meter so that the BOX layer 110 does not remain after etching (that is, the surface of the silicon substrate 101 is just exposed). The etching depth may be controlled.

Next, as shown in FIG. 8, the resist layer 113 is removed. Further, the height of the step formed by etching (the height of the step between the upper surface of the upper clad layer 205 and the surface of the silicon substrate 101 after etching) t ₁ and the upper surface to the lower clad layer 205 of the upper clad layer 205. The film thickness t ₂ up to the lower surface of 103 is measured. The step height t ₁ can be measured using, for example, a stylus type step meter, and the film thickness t ₂ can be measured using, for example, an interference type film thickness meter. In FIG. 8, the height t ₁ and the film thickness t ₂ of the step are measured in the portion of the waveguide 202 including the core layer 104, but as shown in the top view of FIG. 17, the core The height t ₁ and the film thickness t ₂ of the step may be measured in the peripheral portion 171 of the waveguide 202 away from the layer 104. The difference t ₁ -t ₂ between the height and the thickness of the step, it is possible to silicon substrate 101 to confirm whether or not etched by the target value H in the etching process of FIG.

Next, as shown in FIG. 9, a resist layer 114 is formed by photolithography on the upper part of the waveguide 202 and a part 115 of the surface of the silicon substrate 101 exposed in the etching step of FIG. A part 115 of the surface of the silicon substrate 101 on which the resist layer 114 is formed can be used as a monitor region for monitoring the etching depth in the etching step of FIG. 10 below. The monitor region 115 may be provided anywhere on the surface of the exposed silicon substrate 101 as long as it does not come into contact with the laser diode 106 mounted in the following steps. For example, as shown in the top view of FIG. 18, the monitor area 115a may be provided at a position facing the waveguide 202 with the position where the laser diode 106 is mounted, or the side where the laser diode 106 is mounted. The monitor area 115b may be provided on the side. Only one of the monitor area 115a and the monitor area 115b may be provided, or both may be provided.

Next, as shown in FIG. 10, the silicon substrate 101 is additionally etched using the resist layer 114 as a mask. The depth to be additionally etched is the amount of decrease Δ in the height of the effective optical axis of the waveguide 202 described above. When etching is performed so that the surface of the silicon substrate 101 is just exposed in the process of FIG. 7, the depth of additional etching in the process of FIG. 10 is H + Δ. In either case, the height from the reference surface S to the etching surface becomes H + Δ due to this additional etching. Further, a step having a height Δ (or H + Δ) is formed in the monitor area 115. As described above, the silicon substrate 101 is etched so that the depth from the reference surface S becomes H + Δ by the two-step etching including the etching step of FIG. 7 and the additional etching step of FIG. The exposed surface of the silicon substrate 101 thus formed is a surface that constitutes the upper surface of the pedestal 207. Anisotropic etching such as RIE is applied to the etching as in the etching step of FIG.

Here, the depth Δ (or H + Δ) to be etched in the additional etching step of FIG. 10 is determined from the thickness t _UC of the upper clad layer 205 measured in the step of FIG. Specifically, the relationship between the thickness t _UC of the upper clad layer 205 shown in FIG. 4 and the effective reduction amount Δ of the height of the optical axis of the waveguide 202 is obtained in advance, and this relationship is used. , it is possible to determine the Δ corresponding to t _UC measured in the step of FIG. The relationship between t _UC and Δ can be obtained by calculation using, for example, the design parameters of the waveguide 202. The design parameters of the waveguide 202 include, for example, the refractive index of each of the lower clad layer 103, the core layer 104, the upper clad layer 205, and the protective film (SiO ₂ film) 108, the lower clad layer 103, and the upper clad layer 205. And the thickness of each layer of the protective film (SiO ₂ film) 108, and the thickness and width of the core layer 104. Alternatively, by separately preparing several evaluation waveguides 202 having different thicknesses of the upper clad layer 205 in advance and experimentally determining the actual position of the optical axis for each of the evaluation waveguides 202. , T _UC and Δ can also be obtained.

Next, as shown in FIG. 11, the resist layer 114 is removed. Furthermore, to measure the height t ₃ of steps formed by etching the monitor region 115. The step height t ₃ can be measured using, for example, a stylus type profilometer or a laser microscope. From the measured height t ₃ of the step, it is possible to silicon substrate 101 to confirm whether or not etched by the target value delta (or H + delta) in additional etch step of FIG. 10.

Next, as shown in FIG. 12, a resist layer 116 is formed by photolithography on the upper part of the waveguide 202 and a part 117 of the surface of the silicon substrate 101 formed in the additional etching step of FIG. A part 117 of the surface of the silicon substrate 101 on which the resist layer 116 is formed is a portion to be the upper surface of the pedestal 207 and the mounting mark 118.

Next, as shown in FIG. 13, the silicon substrate 101 is etched using the resist layer 116 as a mask. By this etching, a part of the surface of the silicon substrate 101 is processed into a convex shape to form the pedestal 207 and the mounting mark 118. The upper surfaces of the pedestal 207 and the mounting mark 118 are formed at positions lowered by H + Δ from the reference surface S. Anisotropic etching such as RIE is applied to the etching as in the etching steps of FIGS. 7 and 10.

Next, the resist layer 116 is removed, as shown in FIG.

Next, as shown in FIG. 15, a SiO ₂ film is formed as the protective film 108. The protective film 108 is formed so as to cover the entire surface of the silicon substrate 101 including the upper surface of the pedestal 207, and the end surface and the upper surface of the waveguide 202.

Next, as shown in FIG. 16, the laser diode 106 is mounted on the pedestal 207. Specifically, an electrode for conducting conduction with the laser diode 106 (non-existence) on the protective film 108 in the portion other than the pedestal 207, the mounting mark 118, and the monitor areas 115a and 115b dug in the etching process of FIG. (Shown) is formed, and a solder bump 109 for electrically connecting the laser diode 106 to the electrode and mechanically joining the silicon substrate 101 is formed on the electrode. Then, the laser diode 106 is mounted on the pedestal 207 by mounting the laser diode 106 on the pedestal 207 to heat-melt and cool-solidify the solder bump 109. At this time, by aligning the laser diode 106 with reference to the mounting mark 118, the horizontal position of the laser diode 106 can be accurately aligned.

The optical device 200 is completed by the above steps.

<Second embodiment>
In the optical device 200 of FIG. 2, the height of the upper surface of the pedestal 207 is formed to be lower than the reference surface S by H, and the thickness of the protective film 108 is t _SiO2- Δ (the protective film in the optical device 100 of FIG. 1). It is also possible to form a film having a thickness of 108 (thickness that is Δ thinner than the thickness t _SiO2 ). That is, in the first embodiment, the height of the upper surface of the pedestal 207 is formed to be lower than the height of the upper surface of the pedestal 107 in the optical device 100 of FIG. 1, but instead of forming the pedestal 207 lower by Δ In addition, the laser diode 106 may be mounted at a position lower by Δ by thinning the protective film 108 by Δ. Even with such a configuration, as in the first embodiment, the laser diode 106 is attached to the optical device 100 of FIG. 1 by the amount of reduction Δ of the effective optical axis height of the waveguide 202. It can be mounted at a position lower than the laser diode 106. The manufacturing method of the optical device 200 according to the present embodiment is as follows.

First, the silicon substrate 101 on which the waveguide 202 is formed is etched in the same manner as in the steps of FIGS. 5 to 8. The etching depth is the same as in the first embodiment, so that the height from the reference surface S to the etching surface is H.

Next, a part of the surface of the silicon substrate 101 is etched to form the pedestal 207 and the mounting mark 118 in the same manner as in the steps of FIGS. 12 to 14. The height of the upper surfaces of the formed pedestal 207 and the mounting mark 118 is different from that of the first embodiment, and is a position lowered by H from the reference surface S.

Next, the protective film 108 is formed in the same manner as in the process of FIG. However, the thickness of the protective film 108 to be formed is t _SiO2- Δ, unlike the first embodiment.

Further, in the same manner as in the process of FIG. 16, the laser diode 106 is mounted on the pedestal 207 to complete the optical device.

<Third embodiment>
In the optical device 200 of Figure 2, together with the formed lower by H + αΔ than the height reference surface S of the upper surface of the pedestal 207, the thickness of the protective film 108 _{t SiO2} - has been formed in (1-α) Δ It can also be configured. However, 0 <α <1. That is, in the first embodiment, the pedestal 207 is formed low, and in the second embodiment, the protective film 108 is formed thin, so that the laser diode 106 is mounted at a position lower by Δ. However, in the third embodiment, the laser diode 106 is mounted at a position lower by Δ as a whole by combining the formation of the pedestal 207 low and the formation of the protective film 108 thinly at an appropriate ratio. Is. The case of α = 1 corresponds to the first embodiment, and the case of α = 0 corresponds to the second embodiment. Even with such a configuration, the laser diode 106 is mounted on the laser diode 106 by the amount of decrease Δ of the effective optical axis height of the waveguide 202, as in the first and second embodiments. It can be mounted at a position lower than the laser diode 106 in the device 100. The manufacturing method of the optical device 200 according to the present embodiment is as follows.

First, the silicon substrate 101 on which the waveguide 202 is formed is etched in the same manner as in the steps of FIGS. 5 to 8. The etching depth is such that the height from the reference surface S to the etching surface is H, as in the first and second embodiments.

Next, the silicon substrate 101 is additionally etched in the same manner as in the steps of FIGS. 9 to 11. The additional etching depth is αΔ, unlike the first embodiment. As a result, the height from the reference surface S to the etching surface becomes H + αΔ.

Next, a part of the surface of the silicon substrate 101 is etched to form the pedestal 207 and the mounting mark 118 in the same manner as in the steps of FIGS. 12 to 14. The heights of the upper surfaces of the formed pedestal 207 and the mounting mark 118 are different from those of the first and second embodiments, and are located at positions lowered by H + αΔ from the reference surface S.

Next, the protective film 108 is formed in the same manner as in the process of FIG. However, unlike the first and second embodiments, the thickness of the protective film 108 to be formed is t _SiO2- (1-α) Δ.

Further, in the same manner as in the process of FIG. 16, the laser diode 106 is mounted on the pedestal 207 to complete the optical device.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof.

For example, the optical element 106 may be an element other than the laser diode. Further, the waveguide 202 is not limited to the one formed by using the SOI substrate, and for example, the lower clad layer, the core layer, and the upper clad layer are each made of a material containing SiO ₂ as a main component. It may be. Further, the waveguide 202 is a spot size converter in which the core layer is a silicon waveguide formed of silicon and the core layer is made of a silicon oxide-based material having a higher refractive index than a clad layer such as SiON or SiO _x . It may be a waveguide having a configuration in which the above is combined.

Further, in the first and third embodiments, the two-step etching steps of FIGS. 7 and 10 are carried out, but by one etching, the depth is H + Δ in the first embodiment, and the third embodiment. Then, the etching of the depth H + αΔ may be performed. Further, in the first-stage etching step of FIG. 7, over-etching is performed to a height slightly lower than the reference surface S in order to suppress in-plane variation, and then in the second-stage etching step of FIG. 10, the etching surface is formed from the reference surface S. Additional etching may be performed so that the height to (the upper surface of the pedestal 207) is H + Δ or H + αΔ.

Further, the thickness of the protective film 108 formed in the step of FIG. 15 may be adjusted so as to compensate for the process error of the etching depth in each of the etching steps of FIGS. 7 and 10. For example, the height t ₃ of the measured level difference in the step 11, if that amount of etching in the additional etching step of Figure 10 had exceeded the target value has been found, that over partial protective film 108 The film may be formed as thick as possible.

100 Optical device 101 Substrate 102 waveguide 103 Lower clad layer 104 Core layer 105 Upper clad layer 106 Optical element 107 Pedestal 108 Protective film 109 Bonding agent 110 BOX layer 111 SOI layer 112 SiO ₂ layer 113 Resist layer 114 Resist layer 115 Monitor area 116 Resist layer 118 Mount mark 200 Optical device 202 Waveguide 205 Upper clad layer 207 Pedestal

Claims (10)

The process of forming a waveguide on the substrate and
The step of specifying the thickness of the upper clad layer of the formed waveguide, and
The process of forming the mounting surface of the optical element on the substrate and
A method for manufacturing an optical device, which comprises a step of mounting the optical element on the mounting surface.
The upper clad layer of the waveguide has a thickness such that the optical axis of the waveguide is located on the substrate side of the center of the core layer of the waveguide.
The step of forming the mounting surface is
A first etching step of etching the substrate by the first etching depth, and
A step of forming a resist layer in a monitor region which is a part of the surface of the substrate after the first etching step, and a step of forming a resist layer.
A step of determining the second etching depth based on the thickness of the identified upper clad layer, and
This is a second etching step of additionally etching the substrate by the second etching depth using the resist layer as a mask, and the mounting surface is formed from the surface of the substrate after the second etching step. , The second etching process,
In order to confirm the etching depth by the second etching step, a step of measuring the height of the step formed in the monitor region after the second etching step and a step of measuring the height of the step formed in the monitor region.
Methods of manufacturing optical devices, including. In the step of determining the second etching depth, the thickness of the upper clad layer and the amount of displacement of the height of the optical axis of the waveguide from the center position in the height direction of the core layer are obtained in advance. The method for manufacturing an optical device according to claim 1, which is a step of determining the second etching depth using the above-mentioned relationship. The method for manufacturing an optical device according to claim 2, wherein the second etching depth is determined as the displacement amount corresponding to the specified thickness of the upper clad layer by using the above relationship. The method for manufacturing an optical device according to claim 2 or 3, wherein the relationship is obtained by calculation using the refractive index and dimensions of the lower clad layer, the upper clad layer, and the core layer of the waveguide. The method for manufacturing an optical device according to claim 2 or 3, wherein the relationship is obtained by experimentally determining the position of the optical axis for each of a plurality of evaluation waveguides having different thicknesses of the upper clad layer. .. The first etching depth is such that when the optical element is arranged on the substrate etched to the first etching depth, the height of the optical axis of the optical element is the core of the waveguide. The etching depth is such that it coincides with the center in the height direction of the layer.
The second etching depth is an etching depth corresponding to the difference in height between the center of the waveguide in the height direction of the core layer and the optical axis of the waveguide.
The method for manufacturing an optical device according to any one of claims 1 to 5. The mounting surface is such that the optical axis of the optical element is more than the height center of the core layer of the waveguide in a state where the optical element is mounted on the mounting surface by the first and second etching steps. The method for manufacturing an optical device according to any one of claims 1 to 5, which is formed at a height such that it is located on the substrate side. The process of forming a waveguide on the substrate and
The step of specifying the thickness of the upper clad layer of the formed waveguide, and
The process of forming the mounting surface of the optical element on the substrate and
A method for manufacturing an optical device, which comprises a step of mounting the optical element on the mounting surface.
The upper clad layer of the waveguide has a thickness such that the optical axis of the waveguide is located on the substrate side of the center of the core layer of the waveguide.
The step of forming the mounting surface is
A first etching step of etching the substrate by the first etching depth, and
A step of confirming the etching depth by the first etching step and a step of confirming the etching depth.
A step of forming a resist layer in a monitor region which is a part of the surface of the substrate after the first etching step, and a step of forming a resist layer.
A step of determining the second etching depth based on the thickness of the identified upper clad layer, and
This is a second etching step of additionally etching the substrate by the second etching depth using the resist layer as a mask, and the mounting surface is formed from the surface of the substrate after the second etching step. , The second etching process,
In order to confirm the etching depth by the second etching step, a step of measuring the height of the step formed in the monitor region after the second etching step and a step of measuring the height of the step formed in the monitor region.
Methods of manufacturing optical devices, including. The step of confirming the etching depth by the first etching step is
A step of measuring the height t ₁ of a step between the upper surface of the upper clad layer of the waveguide and the surface of the substrate after the first etching step.
A step of measuring the film thickness t ₂ from the upper surface of the upper clad layer of the waveguide to the lower surface of the lower clad layer of the waveguide.
The step of obtaining the difference between the height t _{1 of the} step and the film thickness t ₂
8. The method of manufacturing an optical device according to claim 8. A step of forming a protective film on the surface of the substrate after the second etching step is further included.
The thickness of the protective film is adjusted according to the height of the step formed in the monitor region.
The method for manufacturing an optical device according to any one of claims 1 to 9 .