KR20050015517A - V-groove strutcure for silica hybrid platform - Google Patents

Abstract

PURPOSE: A V-shaped groove structure of a silica hybrid platform is provided to remove an undercut phenomenon which obstructs an optical fiber packaging by separating an etching mask based on a minimum line width between the V-shaped groove and an auxiliary V-shaped groove. CONSTITUTION: A hybrid platform(10) includes a V-shaped groove(20) for connecting an optical waveguide(11) to an optical fiber. The V-shaped groove corresponds to the optical waveguide. An auxiliary V-shaped grooves(30,31) are formed in a predetermined interval on both sides of the V-shaped groove. An etching mask is easily separated in a final process by a minimum line width between the V-shaped groove and the auxiliary V-shaped grooves. A depth and a line width of the auxiliary V-shaped grooves are smaller than a depth and a line width of the V-shaped groove.

Description

V groove structure for silica hybrid platform {V-GROOVE STRUTCURE FOR SILICA HYBRID PLATFORM}

The present invention relates to a V groove structure for manually aligning optical fibers, and more particularly, to a V groove structure for a silica hybrid platform configured to easily remove an etch mask after etching and to prevent a fiber from being caught in the etch mask. It is about.

In general, optical communication has an advantage that can quickly transfer a large amount of information, but also has a disadvantage due to its unique physical characteristics. The most vulnerable of these is the interconnection between optical fibers and optical devices (optical components), which, unlike copper wire, can only be achieved by precise contact between optical fibers and optical devices. Skill is needed. In addition, the loss due to the interconnection between the optical fiber and the optical element varies greatly depending on the cross-sectional state of the optical fiber, the equilibrium state of the optical fiber, and the angles of the axes of the optical fiber and the core. The most important of these is the fiber alignment. In single-mode fiber, the diameter of the fiber core is about 8 micrometers, and an alignment error of less than 1 micrometer is necessary to have a loss of 0.5 dB.

Platforms in which fiber-optic interconnects have been used have been used in various materials and forms. Materials and structures that can be precisely aligned with various material factors such as workability, durability, environment of use, and economics of the material and the optical fiber are in the form of v grooves using the anisotropic etching property of silicon (Si). . Here, the anisotropic etching of silicon is a representative technique of the micro-processing method to form a fine structure in the bulk (bulk) by using the difference in the etching rate according to the crystal direction. Research on wet etching of silicon has already begun in the 1950s, and by the 1970s, V grooves formed by silicon anisotropic etching by C. M. Miller of AT & T BELL Laboratories began to support and align optical fibers. The bulk silicon exhibits different etching rates depending on the crystal direction because the degree of atomic density varies depending on the crystal direction, and the etching rate in the direction having the lowest activation energy is the highest. Using this principle, a silicon wafer whose surface is a crystal plane is used, and lithography is performed in parallel with the flat zone direction of the silicon wafer. When only a desired portion is exposed to the etching solution, the surface having the highest etching rate is obtained. The difference between the etch rate and the slowest surface reveals a crystal plane with a slope of 54.7 °. In addition, in the crystal planes exposed by etching, the etching stops automatically at the point where they meet each other. Therefore, if the surface of the exposed bulk silicon is square, a pyramidal structure is formed, and if it is rectangular, a long V groove is formed. In this case, the part that is not exposed to the etching solution is protected by an etching-resistant material, which is called an etching mask, and a silicon oxide film (SiO 2) or a silicon nitride film (Si 3 N 4) is usually used. Meanwhile, as anisotropic etching solution of silicon, KOH (Potassium Hydroxide) aqueous solution is widely used. The silicon etching reaction in the aqueous KOH solution reacts with hydroxyl ions to release four electrons, and part of the water is reduced to generate hydrogen gas, which is then combined with silicon ions to dissolve again. The depth of the formed V groove is determined by the width of the opening exposed to the etching solution. When the outer diameter of the optical fiber is determined, the width of the V groove suitable for supporting the optical fiber is determined. Undercut is an important consideration in determining the width of the V groove. The undercut formed by digging between the etching mask and the silicon creates an V-groove larger than the calculated value. Therefore, when the undercut is not uniform, the alignment accuracy of the optical fiber is degraded.

The above describes a technique of simply making a platform having a V groove. In the past, the V groove platform, an optical fiber, and an optical device were manufactured, and a single module was manufactured by using a polymer adhesive, but recently, a light source, Attempts have been made to reduce the manufacturing costs by making optical devices consisting of optical waveguides and V groove platforms on a single substrate to reduce size and simplify the process. Such a platform is called a hybrid platform.

In the past, the process of making the V groove did not affect other parts because each part was made together and manufactured together. However, in the hybrid platform of FIG. That is, the etching mask of the V groove should use a silicon oxide film (hereinafter referred to as silica) used as an undercladding layer of the silica PLC (planar lightwave circuit). Silica has a higher atomic density than silicon nitride, so the etching rate is high for the etching solution, and much more undercut occurs.

1 is a diagram illustrating a structure of a hybrid platform 200 according to the prior art, and FIG. 2 is a process diagram illustrating an etching process for forming a V groove of a general hybrid platform.

As shown in FIG. 1, an undercut is shown by an etching mask 211 at both ends of one V groove 210.

Referring to the above-described manufacturing process of the V groove, first, an under cladding layer, which is a low refractive index silica film, and a core layer, which is a high refractive index silica film, are manufactured on a silicon wafer by FHD, and the core layer is selectively etched using lithography. After forming the optical waveguide through the FHD method, the overcladding layer, which is a low refractive index silica film, is covered again. (A) The silica layer of the part where the V groove is to be formed is etched to an appropriate thickness with an etching mask. (B of FIG. 2) Then, the silica film is subjected to selective etching using a lithography to create an opening in which the V groove is to be formed. When it is immersed in the KOH etching solution for a suitable time, the anisotropic etching proceeds to form a V groove. (C of FIG. 2) When the unnecessary surface is cut by using a saw (FIG. 2D), it is formed in the state of FIG. 1. .

However, as shown in FIG. 3, when the silica is used as an etch mask, undercut occurs severely, but only the etch mask cannot be replaced with silicon nitride due to the process characteristics of the hybrid platform. In general, undercut acts as a factor that causes optical loss by decreasing the alignment accuracy of the optical fiber, but through experiments, the degree of undercut was uniform even regardless of the wafer position. Therefore, if a small opening is made in consideration of the undercut, a V groove having an appropriate width can be manufactured to support the optical fiber. You may not be able to enter. Therefore, selective etching using hydrofluoric acid (HF) etching and lithography is considered to remove the etching mask. However, both processes are inferior in terms of additional processes. The sacrificial film process is required, and in the selective etching process, incorrect etching due to a step is likely to deform the shape of the V groove.

SUMMARY OF THE INVENTION An object of the present invention is to provide a V-groove structure for a silica hybrid platform configured to easily remove an etch mask at the same time as V-groove is formed.

Another object of the present invention is to provide a v groove structure for a silica hybrid platform configured to easily perform alignment of optical fibers only by the number of processes as in the prior art.

In order to solve the above object, the present invention provides a hybrid platform in which a V groove for connecting the optical waveguide and the optical fiber together with the optical waveguide, the auxiliary groove having a predetermined interval on both sides of the V groove. By forming a V groove, the etching mask is easily separated in the final process by the minimum line width between the V groove and the auxiliary V groove.

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

4 is a view illustrating a structure of a hybrid platform according to the present invention, and FIG. 5 is a cross-sectional view and a plan view of a V groove fabricated as compared with the related art according to the present invention, and one side of the optical waveguide 11 of the hybrid platform 10 is illustrated. The V groove 20 having a predetermined line width and a predetermined depth is formed in the. On both sides of the V groove 20, auxiliary V grooves 30 and 31 having at least a line width and a depth smaller than those of the V groove 20 are formed. The auxiliary V grooves 30 and 31 have an etch mask having a predetermined line width with the V groove 20 so that the auxiliary V grooves 30 and 31 can be easily detached (removed).

6A and 6B are cross-sectional views illustrating a manufacturing process of a V groove according to the present invention, and FIG. 6C is a cross-sectional view illustrating a state in which optical fibers are manually aligned in a V groove according to the present invention. When etching occurs, the V groove shape is formed and undercut occurs at the same time. Undercuts develop as secondary V-grooves are formed even in small openings on both sides (FIG. 6A). The undercut of these two portions gradually causes the etching mask to lose the supporting silicon on the lower surface. In the selective etching using lithography, the width Y of the etching mask is determined so that the length of the silicon supported by the etching mask is very small. After a certain period of time, the etch mask is barely supported by the silicon, so it will fall off on its own by a small amount of pressing force or during the sawing process (Fig. 6b). There is no etch mask that prevents the insertion of (Fig. 6c).

Meanwhile, referring to FIG. 6A, the minimum line width Y of the etching mask between the V groove and the auxiliary V groove may be determined by the following equation.

First, the initial line width of the opening for mounting the optical fiber is W ₀ , the depth of the V groove when there is no undercut is D ₀ , the etching time at this time is T ₀ , and the etching speed with respect to the (100) plane is R (100). Assuming that the etching speed at the surface of (111) and (111) is R (111), the minimum line width Y can be achieved by the following Equations 1 to 8.

_{D 0 = W 0/2 /} tanθ

T ₀ = D ₀ / R (100)

W ₁ = W ₀ + 2 × T ₀ × R (111) = W ₀ [1 + 1 / tanθ × (R (111) / R (100))]

_{D 1 = W 1/2 /} tanθ

T ₁ = D ₁ / R (100)

W ₂ = W ₁ + 2 × (T ₁ -T ₀ ) × R (111)

= W ₀ [1 + 1 / tanθ × (R (111) / R (100))] + (W ₁ -W ₀ ) / tanθ × (R (111) / R (100))

= W ₀ [1 + tanθ × (R (111) / R (100)) + (R (111) / R (100)) ² ]

W ₂ '= W ₁ ' + 2 × (T ₁ '-T ₀ ') × R (111)

= W ₀ '[1 + 1 / tanθ × (R (111) / R (100))] + (W ₁ ' -W ₀ ') / tanθ × (R (111) / R (100))

= W ₀ '[1 + tanθ × (R (111) / R (100)) + (R (111) / R (100)) ² ]

Y = [(W ₂ -W ₀ ) + (W ₂ '-W ₀ ')] / 2

= (W ₀ {tanθ × (R (111) / R (100)) + (R (111) R (100)) ² } W ₀ '{tanθ ×

(R (11) / R (100)) + (R (111) / R (100)) ² }] / 2

Apparently, there are many ways to modify these embodiments while remaining within the scope of the claims. In other words, there may be many other ways in which the invention may be practiced without departing from the scope of the following claims.

The V groove of the hybrid platform according to the present invention has an auxiliary V groove formed by an etching mask having a predetermined line width on both sides, and finally forms the etching mask having the minimum line width between the V groove and the auxiliary V groove. By easily removing the etching mask having a has an effect that does not occur undercut phenomenon that inhibits the optical fiber mounting.

1 is a view showing the structure of a hybrid platform according to the prior art.

2 is a process diagram illustrating an etching process for forming a V groove of a general hybrid platform.

Figure 3 is a view of the undercut phenomenon that the undercut according to the prior art is badly generated at the end of the V groove.

4 shows the structure of a hybrid platform according to the invention;

Figure 5 is a cross-sectional view and plan view of the V groove fabrication compared to the prior art according to the present invention.

6a and 6b are sectional views showing the manufacturing process of the V groove according to the present invention.

Figure 6c is a cross-sectional view showing a state in which the optical fiber is manually aligned in the V groove according to the present invention.

Claims (2)

A hybrid platform in which a V groove for connecting an optical waveguide and an optical fiber together is formed to correspond to the optical waveguide. V grooves for the silica hybrid platform may be formed on the both sides of the V grooves by forming auxiliary V grooves having a predetermined interval so that the etching mask is easily separated in the final process by the minimum line width between the V grooves and the auxiliary V grooves. rescue. The method of claim 1, The depth and line width of the auxiliary V groove is smaller than the depth and line width of the V groove V groove structure for a hybrid hybrid platform.