JPH0756036A - Optical waveguide device and its production - Google Patents

Abstract

PURPOSE:To provide the optical waveguide device which lessens the influence of cutting from a substrate at the time of device production so as to omit a polishing stage and to lessen thermal damage at the time of fixing by forming a metallic film and metallic plate on the rear surface of the substrate. CONSTITUTION:The metallic film 16 is formed on the rear surface of the waveguide substrate 12 and further, the metallic plate 17 is formed thereon. The metallic plate 16 releases the stress at the time of production and releases the thermal strain by the thermal expansion, etc., of a signal electrode 14a and a grounding 14b. The metallic plate 17 lessens the damage on the waveguide substrate 12 by heat in the case of welding of the optical waveguide device 11 to a module body. Further, blocks 18a, 18b protect the end faces of the guides 13c of the respective waveguides 13a and prevent the generation of cracking and chipping in the case of separating by cutting the waveguide substrate 12 to a chip shape. The polishing stage after cutting is saved by the blocks 18a, 18b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device having an optical waveguide formed on a chip.

In recent years, with the progress of information-oriented society, there is an increasing need to transmit large amounts of data, and optical integrated circuits and optical waveguide devices have been used in the fields of optical communication and information processing.

With the miniaturization and integration of optical integrated circuits, more reliable optical waveguide devices are required. Therefore, it is necessary to reduce the influence of the cutting process during device manufacturing and the influence of heat during fixing.

[0004]

2. Description of the Related Art A conventional optical waveguide device has L _i
N _b O ₃ optical waveguide by diffusion or the like on a substrate (lithium niobate) or the like is formed at a predetermined chip unit is a chip by forming after cutting. This chip is UV (ultraviolet)
It is generally formed by being fixed to a metallic module housing such as stainless steel with an adhesive such as a cured resin.

By the way, the fixing method using an adhesive causes irregular movement depending on the temperature, which is peculiar to the resin, and the difference in thermal expansion coefficient and Young's modulus between the metallic module housing and the waveguide substrate. Due to the heat distortion, the optical axis shifts, and the stress applied to the chip changes the optical characteristics.

Therefore, it is known to form a metal film on the back surface of the chip and fix it to the metallic module housing by welding (for example, Japanese Patent Laid-Open No. 4-436923).
That is, a metal film is formed on the back surface of the substrate on which the optical waveguide is formed, and after cutting in chip units, the cut surface of the optical waveguide is polished and each chip is fixed to the metallic module housing by welding.

On the other hand, in the case of an optical waveguide device such as quartz,
After forming an optical waveguide by diffusion etc. in chip units, it is mechanically cut out by a dicing saw or the like. And
At least the end face of the optical waveguide of the cut surface is polished, and the fixing method is the same as described above.

[0008]

However, in the fixing method described in the above publication, the waveguide substrate is damaged by heat during welding. Further, since it takes an extremely long time to polish the optical waveguide surfaces one by one after the chip is cut, if the polishing process is omitted, the optical characteristics may change due to cracks or chipping on the optical waveguide surface caused by cutting. become. This crack or chipping cannot be visually recognized when the metal film is formed on the back surface of the substrate as described above, and there is a problem that the yield is reduced.

Therefore, the present invention has been made in view of the above problems, and provides an optical waveguide device that reduces the influence of cutting from the substrate during device manufacturing, omits the polishing step, and reduces thermal damage during fixing. The purpose is to do.

[0010]

Means for Solving the Problems The above-mentioned problems are solved by a chip-shaped waveguide substrate having an optical waveguide formed on one surface, a predetermined metal film formed on the other surface of the waveguide substrate, and the metal film. This is solved by adopting a configuration having a predetermined metal plate formed on the surface. Then, a protective member is appropriately formed on the optical waveguide of the optical waveguide substrate of the waveguide substrate at the position of the end face of the optical waveguide by chip formation. Alternatively, the end portion of the optical waveguide is smoothed by forming a groove by etching.

[0011]

As described above, the optical waveguide device of the present invention is
A metal film is formed on the back surface of the surface of the waveguide substrate on which the optical waveguide is formed, and a predetermined metal plate is formed on the metal film. That is, when the optical waveguide device is fixed to the module main body, the above-mentioned metal film and metal plate cancel out thermal strain due to thermal expansion or the like generated between the module main body and the waveguide substrate. This makes it possible to reduce heat damage during fixing.

Further, by forming the protective member at the position of the end face of the optical waveguide on the optical waveguide, it is possible to reduce the influence of cutting into chips on the waveguide substrate and to omit the polishing process of the end face. It will be possible. Alternatively, the position of the end face of the optical waveguide is smoothed by forming a groove by etching, so that the step of polishing the end face can be omitted.

[0013]

FIG. 1 is a block diagram of the first embodiment of the present invention. 1A is a schematic side view, FIG. 1B is a schematic plan view, and FIG. 1C is a schematic view of the back surface of the substrate.

The optical waveguide device 11 shown in FIGS. 1A to 1C is a Mach-Zehnder type optical modulator, and has L _i N _b.
The waveguide substrate 12 made of an electro-optic effect crystal such as O ₃ (lithium niobate) or Si (silicon) is shown in FIG.
As shown in (B), input (output) waveguide 13a, branch waveguides 13b ₁ and 13b ₂ , output (input) waveguide 13c
Is formed in a predetermined number, and the signal electrode 14a and the ground electrode 14b are formed on the respective branch waveguides 13b ₁ and 13b ₂ .

The signal electrode 14a is formed in a traveling wave type. That is, when it is used as a constituent element of the electrode distributed constant circuit, it is formed so that the propagation direction of the drive potential signal, for example, in the microwave region propagating through the signal electrode 14a and the direction of the propagating light in the branch waveguide 13b ₁ coincide with each other. It is a thing.

Also, on the back surface of the waveguide substrate 12, as shown in FIG.
As shown in (C), a predetermined number of linear determination waveguides 15 are formed. A metal film 16 of gold or the like is formed on the back surface of the waveguide substrate 12, and the waveguide substrate (L _i N _b O ₃ ) 12 and stainless steel (SUS304) having a thermal expansion coefficient close to that of the waveguide substrate (L _i N _b O ₃ ) 12 are formed on the metal film 16. The weldable metal plate 17 is formed.

Then, the optical waveguide 13a of the waveguide substrate 12
.About.13c on the formation surface, and the optical waveguides 13a to 13c.
Blocks 18a, 18b which are protective members at the positions of the end faces of the
Is formed.

In the optical waveguide device 11 of such a Manzender type optical modulator, the optical signal input to the input waveguide 13a is branched into the branch waveguides 13b ₁ and 13b ₂ and proceeds.
Therefore, when an electric field is applied to the signal electrode 14a, the substrate 12 bends in accordance with the strength of the electric field and the branch waveguide 13b.
The refractive index of the optical signal traveling in ₁ is changed.

That is, the phase of the optical signal traveling in the branch waveguide 13b ₁ changes with respect to the optical signal traveling in the branch waveguide 13b ₂ . Then, the optical signal having the phase changed in the branch waveguide 13b ₁ and the optical signal propagating in the branch waveguide 13b ₂ are combined by the output waveguide 13c, and the optical intensity is changed with respect to the input optical signal. It is output as an optical signal.

In this case, the metal film 16 serves to relieve the stress at the time of manufacturing and to relieve the thermal strain due to the thermal expansion of the signal electrode 14a and the ground electrode 14b. Further, the metal plate 17 plays a role of reducing damage to the waveguide substrate 12 due to heat when the optical waveguide device 11 is welded to the module body (made of stainless steel). further,
The blocks 18a and 18b protect the end faces of the respective waveguides 13a to 13c and prevent the occurrence of cracks and chippings when the waveguide substrate 12 is cut into chips (for each waveguide) and separated. In this block 18
With a and 18b, the polishing step after cutting can be omitted.

Therefore, FIGS. 2 and 3 show the manufacturing process chart of FIG. FIG. 2 is a process diagram in the case of manufacturing the optical waveguide device group, and FIG. 3 is a process diagram in the case of being made into chips and fixed to the module body.

In FIG. 2, first, as a premise, L _i N _b
As shown in FIG. 1 on the upper surface and the back surface of the waveguide substrate 12 formed of O ₃ .
The waveguides 13a and 13b and the determination waveguide 15 as shown in FIGS. 9B and 9C are formed by selectively diffusing a metal such as T _i (titanium).

The upper surface of the waveguide substrate 12 (waveguide 13a
~13c on the face) which is formed, S _i O ₂ film, for example, 5000Å as a buffer layer (insulating film) 21 is formed (FIG. 2 (A)). Similarly, S _i O ₂ film 22 on the back surface as a buffer layer (a surface determination waveguide 15 is formed) e.g. 5000Å of the waveguide substrate 12 is formed (FIG. 2 (B)).

[0024] On S _i O ₂ film 21, together are formed by depositing the signal electrodes 14a and ground electrodes 14b, as shown in FIG. 1 (B) such as gold and gold plated (10 [mu] m),
S _i O ₂ film 22 on FIG. 1 metal as shown in (A) layer 1
6 is formed by evaporating gold and gold plating (10 μm), for example (FIG. 2C). Original device 1 in this state
It is called 1a.

Then, a stainless steel (SUS304) metal plate 17 is brazed to the original device 11a with, for example, a paste 23 of AuSn (gold tin) (FIG. 2).
(D)).

Further, FIG. 3A shows a case where the metal plate 17 is brazed to the original device 11a shown in FIG. 2D via the paste 23. And the original device 11
Blocks 18a and 18b are attached to the portions located on the end faces of the waveguides 13a to 13c on a by an adhesive or the like,
The portion is cut by a blade or the like and separated into chips (FIG. 3 (B)). As a result, a chip-shaped optical waveguide device (chip) 11 is manufactured.

At this time, light is coupled to the determination waveguide 15 on the back surface of the chip after cutting and the coupling loss is measured, whereby the progress of cracks and chippings generated between the waveguide substrate 12 and the metal film 16 is advanced. Can be measured. For example, if the coupling loss of the determination waveguide 15 is 10 dB or more, it is determined that the back surface is cracked.

Then, the formed chip-shaped optical waveguide device 11 is fixed to the module body 24 made of stainless steel by welding (FIG. 3C).

As a result, a more reliable optical waveguide device is constructed, the influence of cutting in manufacturing can be reduced, the polishing step can be omitted, and the manufacturing time can be greatly shortened. Further, the metal plate 17 can reduce heat damage to the waveguide substrate 12 when it is fixed to the module body 24.

Next, FIG. 4 shows a manufacturing process diagram of the second embodiment of the present invention. In the second embodiment of the present invention shows a case where an optical waveguide is formed on a wafer of S _i (silicon), cut into chip-like, it separated.

In FIG. 4, first, optical waveguides 33 having a predetermined pattern are formed in a plurality of regions 32 on the wafer 31 to be made into chips by diffusion or the like. (Fig. 4
(A)). The optical waveguide 33 is formed by depositing a S _i layer 34 is formed over the entire surface (FIG. 4 (B)). Then, etching is performed by multiple exposure or the like so as to expose the separation line 35 of the cut portion (FIG. 4C).

Subsequently, although not shown, the exposed separation line 35 is subjected to RIE (reactive ion etching) or the like.
A groove is formed in the chip region 32 at a depth where the end face of the optical waveguide 33 is exposed. In this case, the RIE method is dry etching, but wet etching with hydrofluoric acid may be performed.

Then, the blade is cut along the groove of the separation line 35. That is, the cutting with the blade can be omitted from the conventional polishing step after cutting by using a blade having a width that does not affect the end face of the optical waveguide 33.

FIG. 5 shows an explanatory view of the optical waveguide device manufactured by FIG. In the step shown in FIG. 4, a plurality of chip regions 32 having optical waveguides 33 are formed on the wafer 31 as shown in FIG. 5A, and the state after chip formation by separation is shown in FIG. It is shown in (C).

[0035] That is, the optical waveguide 33 formed on the wafer 31, at the time of its formation (when diffusion), is divided into areas of two layers of S _i O _2, as shown in FIG. 5 (C), S _i O It becomes a core region in which the optical waveguide 33 is formed in the _two regions 32a.
Then, in which grooves formed by etching the above-described separation line 35 is carried out to a depth of the S _i O ₂ region 32a, is cut by a blade of the underlying S _i O ₂ region 32b.

Generally, dry etching and wet etching can improve the surface accuracy more than dicing with a blade, and can suppress the surface accuracy to, for example, 1/4 or less of the wavelength λ used in optical communication systems. . That is, if it is λ / 4 or less, the diffusion of light can be suppressed. Therefore, by etching, the optical waveguide 3
If the end face 3 is formed, it is not necessary to perform polishing after cutting with a blade.

Next, although not particularly shown, a third embodiment of the present invention will be described. This third embodiment will be described with reference to FIG. 5. As in the conventional case, an optical waveguide (33) having a predetermined pattern is formed on a wafer 31, and a chip area (32) is formed along a dividing line (35). It is mechanically cut and separated by a dicing saw (blade). The separated chip (32) is immersed in S _i O ₂ etchant solution is to smooth the end face of the optical waveguide.

According to this method, the surface can be smoothed just by immersing it in the etchant solution, and the polishing step can be omitted to greatly reduce the manufacturing time.

[0039]

As described above, according to the present invention, a metal film is formed on the back surface of the surface of the waveguide substrate on which the optical waveguide is formed,
By forming a metal plate on this metal film and forming a protective member at a position on the end face of the optical waveguide, it is possible to reduce the influence of cutting from the substrate in device manufacturing and to omit the polishing step, and to fix it. The heat damage at the time can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram (1) of FIG.

FIG. 3 is a manufacturing process diagram (2) of FIG. 1.

FIG. 4 is a manufacturing process drawing of the second embodiment of the present invention.

FIG. 5 is an explanatory view of the optical waveguide device manufactured by FIG.

[Explanation of symbols]

11 Optical Waveguide Device 12 Waveguide Substrate 13a Input Waveguide 13b ₁ and 13b ₂ Branch Waveguide 13c Output Waveguide 14a Signal Electrode 14b Grounding Electrode 15 Judgment Waveguide 16 Metal Film 17 Metal Plate 18a, 18b Block 21, 22 S _i O ₂ film 23 Paste 24 Module body 31 Wafer 32 Chip area 33 Optical waveguide 34 _Si film 35 Separation line

Claims (7)

[Claims] 1. A chip-shaped waveguide substrate (12) having optical waveguides (13a to 13c) formed on one surface, and a predetermined metal film (16) formed on the other surface of the waveguide substrate (12). ) And a predetermined metal plate (17) formed on the surface of the metal film (16)
An optical waveguide device comprising: 2. The optical waveguide (1) of the waveguide substrate (12)
3a to 13c) and at positions of the end faces of the optical waveguides (13a to 13c) formed into chips, the protective member (18a, 1a).
8b) is formed, the optical waveguide device according to claim 1. 3. The optical waveguide device according to claim 1, wherein an optical waveguide (15) is formed on a surface of the waveguide substrate (12) on which the metal film (16) is formed. 4. A chip-shaped waveguide substrate (12) on which optical waveguides (13a to 13c) are formed is attached to a module body (2).
4) In the method for manufacturing an optical waveguide device fixed to the optical waveguide device, the optical waveguide (13) is provided on one surface of the waveguide substrate (12).
a to 13c) and a step of forming a predetermined electrode, a step of forming a predetermined metal film (16) having the same or similar thermal characteristics as the electrode on the other surface of the waveguide substrate (12), A step of forming a predetermined metal plate (17) on the surface of the film (16) with a predetermined adhesive member (23); a step of separating the waveguide substrate (2) into chips; A step of fixing the surface of the metal plate (17) of the substrate (12) to the module main body (24), and a method for manufacturing an optical waveguide device. 5. The optical waveguide (1) before the chip separation.
3a to 13c) and at positions of the end faces of the optical waveguides (13a to 13c) formed into chips, the protective member (18a, 1a).
8b) is formed, The manufacturing method of the optical waveguide device of Claim 4 characterized by the above-mentioned. 6. An optical waveguide (3) having a predetermined pattern is formed in each of a plurality of regions (32) to be made into chips on a wafer (31).
3), a step of applying a predetermined member (33) on the optical waveguide (33) to expose only the separation line (35) for chip formation, and the exposed separation line (35) ) By etching
Forming a groove at least to the depth of the end face portion of the optical waveguide (33), and mechanically cutting the groove along the groove formed in the wafer (31) to form the optical waveguide (33) And a step of separating the formed chips, and a method for manufacturing an optical waveguide device, comprising: 7. A step of forming an optical waveguide (33) having a predetermined pattern in each of a plurality of regions to be made into chips on a wafer (31), and the optical waveguide is formed along a separation line (35). An optical waveguide comprising: a step of mechanically cutting the chip region to separate it; and a step of immersing the chip in a predetermined etching solution to smooth the end face of the optical waveguide (33). Device manufacturing method.