JPH05119221A - Production of optical waveguide - Google Patents

Abstract

PURPOSE:To enable three-dimensional wiring of optical waveguides within a device or chip by forming an optical waveguide down to the position of an arbitrary depth in a dielectric layer. CONSTITUTION:Impurity ions 14 for increasing the refractive index of the dielectric substance of the dielectric layer 11 formed on the surface of a substrate 10 are implanted with high energy into the dielectric layer. The optical waveguide (core) 15 constituted of the high-concn. region of the impurity element is formed not on the surface but in the inside of the dielectric layer 11. The depth of the high-concn. region (core) 15 can be controlled by changing the implantation energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide formed inside a device or chip such as information processing, communication and sensor.

[0002]

2. Description of the Related Art An optical fiber is one in which light is confined in the core and transmitted by making the refractive index of the central portion (core) of the fiber larger than that of the peripheral portion. Due to its strength, it can be used not only for long-distance communications such as telephone networks, but also for in-building communications and inter-device communications. In addition, since the amount of information transmission per unit time can be dramatically increased in optical communication, the inside of the device can be further Has attempted communication using light even inside one device (or chip).

However, when optical communication is performed inside a single device or chip, the fiber type is inconvenient to handle and has a limit to integration. Therefore, a thin film type optical waveguide formed on a substrate is mainstream. Becomes Heretofore, thin-film type optical waveguides are: (a) a stack of different types of dielectric thin films having different refractive indexes (step index type optical waveguide), (b) ion exchange or metal diffusion on the surface of the dielectric thin film. It is considered that impurities are introduced by the above method to change the dielectric constant of the surface portion, and (c) an unevenness or a buried layer is formed on the surface of the dielectric and an optical waveguide is constituted by the surface shape. There is.

[0004]

All of the above-mentioned conventional thin film type optical waveguides are formed on the surface of a dielectric thin film, and are therefore limited to two-dimensional wiring on the surface. On the other hand, the number of elements to be mounted on a data processing device or a chip has increased dramatically in recent years with the increase in capacity of handled data and the sophistication of processing contents. In order to cope with such an increase in the number of elements and an improvement in the degree of integration, designs for arranging elements and wirings in a three-dimensional manner are beginning to be performed. In order to perform the above, it is necessary to enable three-dimensional wiring of the optical waveguide.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a thin film type optical waveguide formed on a dielectric layer on the surface of a substrate. It is an object of the present invention to provide a method for manufacturing an optical waveguide, which enables formation at an arbitrary depth position inside a substrate, thereby enabling three-dimensional wiring of the optical waveguide in a device or a chip.

[0006]

In order to solve the above-mentioned problems, an optical waveguide manufacturing method according to the present invention comprises a dielectric layer with a high energy of impurity ions for increasing the refractive index of the dielectric. An optical waveguide composed of a high-concentration region of impurity ions is formed inside the dielectric layer.

[0007]

When the impurity ions are injected from the surface of the dielectric layer on the substrate with high energy, the impurity ions still have a very large energy just below the surface of the dielectric layer, so that the molecules or molecules forming the dielectric layer are It does not stop even if it collides with an atom, and stops only when it reaches a certain depth (internally). That is, the portion where the concentration of impurity ions is high is formed not inside the surface of the dielectric layer but inside. Therefore, by performing the high-energy ion implantation linearly from the surface of the dielectric layer, a portion having a high impurity concentration inside the dielectric layer can be formed in a tunnel shape. Since the impurity ions are selected so as to increase the refractive index of the dielectric layer, this high concentration portion becomes an optical waveguide in the dielectric layer. Since the depth from the surface of the optical waveguide can be controlled by changing the implantation energy of the impurity ions, the optical waveguide can be formed at an arbitrary depth position inside the dielectric layer. ..

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing an optical waveguide according to an embodiment of the present invention will be described with reference to FIGS. In the manufacturing method of the present embodiment, first, a silicon oxide film (SiO 2) which is a dielectric thin film is formed on the silicon (Si) substrate 10 by thermal oxidation or CVD.
₂ ) 11 is formed (FIG. 1A). Next, a photoresist 12 is applied on the silicon oxide film 11 and a portion (linear shape) where an optical waveguide is to be formed by photolithography
An opening 13 is provided in the (FIG. 1 (b)).

Then, phosphorus ions (P ⁺ ) 14 which are impurity ions are implanted from above the photoresist 12 at a high energy of about 1 MeV (FIG. 2C). The phosphorus ions are blocked by the photoresist 12 in the portion where the photoresist 12 remains, and do not reach the silicon oxide film 11. Phosphorus ions 14 are implanted into the silicon oxide film 11 at the opening 13 of the photoresist 12, but the energy thereof is so high that it does not stop immediately below the surface.
It is not trapped in the crystal lattice of the silicon oxide (silicon oxide film) 11 until it reaches a certain depth.
Therefore, the cross-sectional shape of the concentration distribution of phosphorus ions in the silicon oxide film 11 by this high energy ion implantation is shown in FIG.
As shown in (c), the high-concentration portion is the silicon oxide film 11
Formed inside. When viewed three-dimensionally, the phosphorus ion high concentration portion has a tunnel shape in the silicon oxide film 11. Hereafter, this high-concentration part is referred to as the core 15
Call.

Since the phosphorus ion (P ⁺ ) has a function of increasing the refractive index of silicon oxide (SiO ₂ ), the core 15 becomes an optical waveguide in the silicon oxide film 11. That is, when light passes through the core 15, the light is reflected at the boundary with the peripheral low-concentration portion (silicon oxide film 11) and returned to the core 15, so that the light is transmitted to the core 15.
Go through. In addition to phosphorus ions, ions of various elements such as trivalent boron (B) and pentavalent arsenic (As) can be used as impurities for increasing the refractive index of the silicon oxide 11.

Next, the photoresist 12 having the wiring pattern is removed, and a photoresist 16 having another opening pattern is formed on the silicon oxide film 11 (FIG. 2).
(D)). From above the wiring pattern, phosphorus ions 17 are implanted into the silicon oxide film 11 with higher energy (for example, about 3 MeV). Therefore, the phosphorus ion high-concentration portion (core) 18 formed by the ion implantation this time is formed at a deeper position than that formed previously, and as shown in FIG. 18 will cross over.

As described above, according to the manufacturing method of the present embodiment, the high refractive index cores 15 and 18 are formed at arbitrary depths inside the dielectric thin film (silicon oxide film) 11 on the substrate 10. Can be formed. Therefore, various three-dimensional wiring can be performed in addition to the three-dimensional cross wiring as shown in FIG. For example, as shown in FIG. 3B, high density wiring can be performed by alternately arranging adjacent parallel optical waveguides at deep positions and shallow positions. The narrow pitch wiring as shown in FIG. 3B is particularly effective for high integration of a device formed by arraying a large number of elements.

In the above embodiment, the photoresist 1 is used.
The wiring pattern of the optical waveguide was formed by 2 and 16,
By moving the thinly focused ion beam linearly (vector scan), or conversely, by moving the substrate 10 (and the dielectric layer 11) while keeping the ion beam narrowly focused and fixed, the photoresist Mask 12,
It is also possible to form a core wiring of any pattern without using 16. Further, as the dielectric layer, it is possible to use silicon nitride or the like other than silicon oxide as in the above embodiment.

[0014]

According to the present invention, since the impurity ions are implanted with high energy, the high concentration region of the impurity ions, that is, the optical waveguide is formed inside the dielectric layer. The depth from the surface of the optical waveguide can be changed by changing the implantation energy of impurity ions. Therefore, by forming two or more optical waveguides inside the dielectric layer with different implantation energies, it is possible to wire these optical waveguides in a vertically crossed manner without crossing each other inside the dielectric layer. it can. In the case of parallel wiring,
The wiring pitch can be narrowed by alternately changing the depths of adjacent wirings. By such three-dimensional wiring of the optical waveguide (that is, three-dimensional cross wiring or fine pitch wiring), it becomes possible to perform on-chip optical communication even in a three-dimensional device. Further, even in an ordinary two-dimensional device, by using such a three-dimensional wiring, the degree of integration can be increased, and the communication time within the device (chip) can be shortened and the processing speed can be improved. You can Further, since the degree of freedom in wiring design is improved by the three-dimensional wiring, the design load is greatly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing each step of a manufacturing process of a thin film type optical waveguide which is an embodiment of the present invention, (a) is a perspective view of a chip having a dielectric layer provided on a substrate, and (b) is a diagram. FIG. 3 is a perspective view of a chip in which a photoresist is provided on a dielectric layer.

FIG. 2 is an explanatory view showing each step of the manufacturing process after FIG. 1 of the embodiment, and FIG. 2 (c) is a perspective view of the chip in a state where high-energy ion implantation is performed from above the photoresist,
FIG. 3D is a perspective view of another photoresist pattern and a chip in a state where ion implantation is performed with another high energy.

FIG. 3A is a perspective view of a chip in which optical waveguides are three-dimensionally crossed in a dielectric layer, and FIG. 3B is a perspective view of a chip in which high-density parallel wiring is performed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Silicon substrate 11 ... Dielectric layer (silicon oxide film) 12, 16 ... Photoresist mask 13 ... Openings 14, 17 ... High energy ions 15, 18 ... High impurity concentration portions (core, optical waveguide)

Claims (1)

[Claims] 1. An optical waveguide, which is composed of a high concentration region of impurity ions, is formed in the dielectric layer by injecting into the dielectric layer with high energy impurity ions for increasing the refractive index of the dielectric material. And a method for manufacturing an optical waveguide.