JP2002158228A - Gate array and method for forming logic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that manufacturing steps are complicated and a high cost and a wiring pattern formed once cannot be easily changed because the pattern is removed by etching, by using a mask combined with the pattern after a metal layer is formed in a wiring method between transistors in a conventional gate array. SOLUTION: An optically induced phase change substance is used for wiring. An initial state is formed in an insulating state, light is emitted along the wiring patter, and the pattern is formed as a conductor to constitute conductive wiring. In order to return to the initial state, the wiring is heated, and a conductor state is insulated. Thus, the optically induced phase change substance is used for wiring, an etching step is not required. A process does not use the mask, and hence a mass productivity is remarkably improved. Since the pattern can be easily changed or corrected even after the pattern is once formed, resources can be effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a gate array structure formed by connecting a plurality of transistors formed on a substrate such as a silicon wafer and a logic circuit forming method using the same.

[0002]

2. Description of the Related Art Conventionally, a custom I
In the case of manufacturing C, a metal wiring process such as aluminum (Al) or copper (Cu) is used to perform wiring between some transistors in a process of forming a logic circuit.

[0003]

In order to perform wiring between transistors, it is necessary to form a metal layer by sputtering or the like and then to etch the metal layer through an exposure process using a mask corresponding to the wiring pattern. However, there is a problem that these steps are complicated. Except in some special cases,
One of the disadvantages of the related art is that the wiring pattern once formed cannot be changed.

The present invention solves these problems,
By providing a process in which an etching step is not required at the time of wiring between transistors and a mask is not used in some cases, a method capable of dramatically reducing the number of manufacturing steps as compared with the conventional method is provided. Further, the present invention is an invention that facilitates these changes and corrections even after a wiring pattern is formed once.

[0005]

This and other objects are achieved by the present invention described below. That is, in the gate array of the present invention, in a gate array in which a plurality of transistors formed on a substrate are connected, the connection portion may be any one of an insulated state in a stable state and a conductor state in a metastable state. It is characterized by being constituted by a conductor state of a photo-induced phase change substance that can exist even in a state. Further, in the gate array of the present invention, the conductor state of the photoinduced phase change material is:
It is characterized in that a phase transition can be caused by heating to be in an insulating state. Further, in the gate array of the present invention, the insulating state and the conductive state of the photoexcited phase transition material are a stable state and a metastable state having a long lifetime of one year or more, respectively, and take a reversible state by light or heat. It is characterized by obtaining. In the gate array according to the present invention, the light has energy in a visible or infrared region.

Further, the method of forming a logic circuit of a gate array according to the present invention comprises: (1) a step of opening the basic cells, which are units of the gate array, in an insulated state of the photoinduced phase transition material; and (2) Irradiating light using a mask having a wiring pattern only at a portion requiring connection. The method of forming a logic circuit in a gate array according to the present invention requires (1) a step of opening the basic cells, which are units of the gate array, in an insulated state of the photo-induced phase transition material, and (2) connection. Irradiating a laser beam along a wiring pattern only at a portion.

[0007]

The following is a description of a photo-induced phase change material used in a connection portion between transistors in a gate array, which is a feature of the present invention.

The material used for the wiring portion of the gate array according to the present invention is mainly composed of a transition metal or an oxide thereof, which undergoes a phase transition when irradiated with light or heated. As the transition metal oxide, a general formula Ax
By Oz (where x, y, and z are each 1 ≦ x ≦ 1
4, 1 ≦ y ≦ 24, 1 ≦ z ≦ 41, and A and B may be the same element or different elements). It is considered that the energy state of the atomic system of such a transition metal oxide is changed by light irradiation, the crystal lattice is displaced, and a phase transition phenomenon is caused based on the displacement.

[0009] Such transition metal oxide, the crystal structure is not particularly limited, and a A ions with a + charge on the crystal structure -X - ^{-A +} -X - ^(X
= O, BOx), and a low-dimensional oxide which has a linear one-dimensional structure and is characterized by physical properties is preferable.
This is because it is preferable that the displaced lattice atoms are softly bonded to the lattice, that is, the energy of the lattice strain due to the displacement is smaller, and it is generally considered that a low-dimensional substance has a soft lattice.

An example of such a low-dimensional substance is a delafossite-type oxide represented by the general formula ABO ₂ . In the delafossite-type oxide, the above-mentioned low-dimensional structure has a simple chain-order structure represented by-(BO ₂ ) ^-- A ⁺ -(BO ₂ ) ^-- . Such a simple structure is considered to have an effect of further enhancing the softness of the lattice, which is a characteristic of a low-dimensional substance, and has a characteristic that the response speed of light-induced phase transition is extremely high. Furthermore, the delafossite-type oxide has an advantage that its simple low-dimensional structure can reduce the band gap that determines the energy required for photoinduced phase transition. The band gap is the lowest photon energy at which a light-induced phase transition occurs. If the band gap is small, it is possible to cause a phase transition with lower energy light, and by adjusting this, a laser beam having a wavelength in the visible or infrared region or a general-purpose lamp can be used. The width of dramatically expands. Light in the visible or infrared region should be actively used from the viewpoint of process safety, energy saving, and the like, except for patterning applications having high accuracy such as dimensional accuracy of 1 μm or less. of course,
In a process requiring dimensional accuracy of 1 μm or less, a light source having a short wavelength may be used, and a photo-induced phase change material having a band gap corresponding to the wavelength may be used.

[0011] The light-induced phase transition means that the system is excited by light energy incident on a solid to change an electronic state, thereby causing a lattice displacement. Among the changes in the physical properties of the substance caused by such lattice displacement, the gate array wiring portion of the present invention utilizes the property that the electric conductivity changes dramatically. Incidentally, the physical properties of the solid crystal that change reversibly include an absorption spectrum, a refractive index, and magnetic properties, in addition to the electric conductivity.

By utilizing the change in electric conductivity due to light, it is possible to control reversible phase transition between each other, such as converting an insulator into a conductor or returning the conductor to an insulator. Here, “conducting” means closing a band gap between a valence band and a conduction band filled with an insulator by photoexcitation. In other words, the size of the Brillouin region is doubled by light, and the valence band and the conduction band are coupled. For this purpose, it is only required that the length of the repetition period of the insulator lattice can be reduced to half by light. That is, at a certain temperature or lower, a conductor in which electrons are occupied in half of the band becomes a Peierls insulator because the lattice period a of the conductor becomes 2a due to the lattice displacement and the localization of electrons, and therefore the wave number π / 2a This is because there is a gap in The reverse process is performed by irradiating light, halving the lattice period of the Peierls insulator, and spreading localized electrons uniformly in the crystal, the band gap of the insulator becomes a closed conductor. be able to. Further, the direction of the phase change can be reversed depending on the material design. That is,
The conductor can be insulated by irradiating the conductor with light. Such bidirectional phase transition is possible only by light irradiation, but the effect of heat may be used together. When a laser is used as a light source, attention is paid to the wavelength (energy) of the laser when the insulator is made into a conductor, and the power (heat) of the laser is used when the conductor is returned to the insulator.

The band gap of the transition metal oxide is 1.1.
When it is 5 to 4.05 eV, it is very easy to handle in terms of process. This is because the band gap in this range enables response even when the irradiation light (excitation light) is near the visible region.

Finally, a supplementary note is made on bistability. The term “bistability” as used herein refers to the time required for a transition from a stable state to a metastable state based on a change in the lattice due to light irradiation or the like, and for returning to the original stable state even if the light is extinguished here. (Relaxation time) means very long (for example, one year or more). The time during which the metastable state is maintained, that is, the life can be freely controlled depending on the material design.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on some embodiments.

Example 1 One of the photo-induced phase change materials is CuAlO ₂ belonging to delafossite. CuAlO ₂
Is a perfect insulator near room temperature in its stable state. ,
When this is irradiated with light having a wavelength of 750 nm, the atoms in the crystal lattice move instantaneously only in the irradiated part, thereby expanding the Brillouin region and becoming a metallic state, that is, a good conductor. In this embodiment,
An experiment for confirming such properties of the photo-induced phase change material was performed, and will be described below.

On a 5 mm × 8 mm glass substrate, 1 μm thick
m CuAlO ₂ film was formed by spin coating. Cu
After confirming that the AlO ₂ film was in an insulated state, light having a wavelength of 750 nm was irradiated using a mask in a crank pattern along 102 parts of 1 mm width shown in FIG.

When the electrical characteristics of the sample were examined, only the 102 parts irradiated with light showed conductivity, and the other parts (101
Part) was confirmed to be an insulator as before the irradiation.

Example 2 One of the photo-induced phase transition materials is CuFeO ₂ belonging to delafossite. CuFeO ₂
Is a perfect insulator near room temperature in its stable state. When strong light having a wavelength of 1078 nm is applied to this, the atoms in the crystal lattice move instantaneously only in the irradiated portion, so that the Brillouin region is expanded and the metal state, that is, a good conductor is obtained. In the present embodiment, an experiment for confirming such properties of the photo-induced phase change material was performed, and will be described below.

A 1 μm thick glass substrate of 5 mm × 8 mm
m CuFeO ₂ film was formed by spin coating. Cu
After confirming that the FeO ₂ film was in an insulating state, light irradiation was performed using a laser beam having a spot diameter of 1 mm and a wavelength of 1078 nm in accordance with the crank pattern of 102 parts shown in FIG.

When the electrical characteristics of the sample were examined, it was confirmed that only 102 parts irradiated with the laser beam showed conductivity, and the other parts (101 parts) were insulators as before the irradiation.

(Embodiment 3) FIG. 2 shows a circuit composed of two basic cells formed on a gate array of this embodiment. In FIG. 2, a desired logic circuit is formed by providing a conductor wiring according to the purpose between the four MOS transistors. In the present invention, the cross section of the gate contact portion 203 in FIG. 2 has the structure shown in FIG. FIG. 4 shows the gate insulating layer 403.
The light-induced phase change material layer 401 is provided on the entire surface of the upper layer, and the initial state is an insulating state. In this example, CuAlO ₂ used in Example 1 was used as the photo-induced phase change material. When a wiring is to be drawn from the gate electrode 402, the light-induced phase change material layer 401 on the layout may be irradiated with light along the wiring pattern with the starting point as a starting point to be converted into a conductor. In this example, an attempt was made to fabricate a NAND circuit by performing wiring between the four transistors in the circuit diagram of FIG. 2 by the method described below and newly connecting conductors to the thick line portion shown in FIG.

First, a mask having a newly connected pattern is manufactured. That is, one sheet glass was prepared, and Cr was vapor-deposited on the entire area in the surface of the sheet glass except for the pattern on the layout corresponding to the thick line portion in the circuit diagram of FIG. 3 to obtain an optical mask. After accurately aligning the mask on the gate array, the mask was exposed from above with a lamp having a wavelength of 750 nm. By this step, FIG.
Layer 40 corresponding to the region indicated by the bold line
1 is converted into a conductor, and a desired conductor connection is made.

The operation of the thus-obtained gate array after the wiring processing of the present invention was confirmed. Table 1 shows the results. . Table 1 clearly shows that a NAND circuit was formed. In Table 1, input A, input B and output Z
Are the respective terminals shown in the circuit diagram of FIG.

[0025]

[Table 1]

(Embodiment 4) FIG. 2 shows a circuit composed of two basic cells formed on a gate array according to the present embodiment. In FIG. 2, a desired logic circuit is formed by providing a conductor wiring according to the purpose between the four MOS transistors. In the present invention, the cross section of the gate contact portion 203 in FIG. 2 has the structure shown in FIG. FIG. 4 shows the gate insulating layer 403.
The light-induced phase change material layer 401 is provided on the entire surface of the upper layer, and the initial state is an insulating state. In this example, CuFeO ₂ used in Example 2 was employed as a photo-induced phase change material. When a wiring is to be drawn from the gate electrode 402, the light-induced phase change material layer 401 on the layout may be irradiated with light along the wiring pattern with the starting point as a starting point to be converted into a conductor. In this example, an attempt was made to fabricate a NAND circuit by performing wiring between the four transistors in the circuit diagram of FIG. 2 by the method described below and newly connecting conductors to the thick line portion shown in FIG.

In the circuit diagram of FIG. 3, a spot diameter of 1 is formed by an optical lens along a layout pattern corresponding to a thick line portion.
This was irradiated with a laser having a wavelength of 1078 nm narrowed down to μm. By this processing, the photoinduced phase change material layer 401 corresponding to the region shown by the thick line in FIG. 3 is converted into a conductor, and a desired conductor connection is made.

The operation of the thus-obtained gate array after the wiring processing of the present invention was confirmed. Table 2 shows the results. Table 2 clearly shows that a NAND circuit was formed. In Table 2, input A, input B and output Z
Are the respective terminals shown in the circuit diagram of FIG.

[0029]

[Table 2]

(Embodiment 5) The gate arrays having the NAND circuits manufactured in Embodiments 3 and 4 were placed on a hot plate, heated at 200 ° C. for 1 minute, and then returned to room temperature. When the operation of the logic circuit was examined, it was confirmed that the function as the NAND circuit was lost. In addition, when conduction between terminals such as a gate electrode was examined, FIG.
It was confirmed that the state was as shown in the circuit diagram of FIG. In other words, the wiring portion converted into a conductor by light irradiation is insulated by applying heat and returns to the initial state. Note that the heating conditions (200 ° C. for 1 minute) of the present embodiment are not the optimal conditions, and the temperature conditions required for the insulation treatment are not limited to these conditions.

(Embodiment 6) After performing the insulation treatment (initialization treatment) of the photo-induced phase change material layer 401 of FIG. 4 described in Embodiment 5, CuAlO ₂ is used as the photo-induced phase change material layer 401. The same light irradiation wiring processing as in the process described in Example 3 was performed on the used gate array.

When the operation of the gate array after the wiring processing was confirmed, the operation shown in Table 3 was confirmed. From Table 3, it was confirmed that a NAND circuit was formed.
In Table 3, input A, input B, and output Z are the respective terminals shown in the circuit diagram of FIG.

[0033]

[Table 3] From the facts of this embodiment, the third embodiment and the fifth embodiment, it was found that the gate array of the present invention can repeatedly produce a desired logic circuit by repeating the wiring.

(Embodiment 7) After performing the insulation treatment (initialization treatment) of the photo-induced phase change material layer 401 of FIG. 4 described in Embodiment 5, CuFeO ₂ is used as the photo-induced phase change material layer 401. The same light irradiation wiring processing as in the process described in Example 4 was performed on the used gate array.

When the operation of the gate array after the wiring processing was confirmed, the operation shown in Table 4 was confirmed. Table 4 clearly shows that a NAND circuit was formed.
In Table 4, input A, input B and output Z are the respective terminals shown in the circuit diagram of FIG.

[0036]

[Table 4] From the facts of this embodiment, the fourth embodiment, and the fifth embodiment, it was found that the gate array of the present invention can repeatedly produce a desired logic circuit by repeating wiring.

[0037]

According to the conventional methods described above, in order to perform wiring between transistors in a gate array, a metal layer such as Al is formed by sputtering or the like, and then exposure using a mask corresponding to the wiring pattern is performed. Although it is necessary to etch this through a step and the like, and these steps are complicated, the etching step and the like can be omitted by using a photo-induced phase change material for the wiring member as in the present invention. You can also choose a simpler process that does not require a mask,
It is possible to greatly improve the production cost and delivery time in mass production. In addition to the conventional disadvantage that once formed wiring patterns cannot be changed, except for some special cases, these changes and corrections can be easily performed even after once forming wiring patterns as described in the embodiment. The present invention that can be made makes a great contribution to the effective use of resources that has been required in recent years.

[Brief description of the drawings]

FIG. 1 is a view showing formation of a conductive path by a photoinduced phase change substance.

FIG. 2 is a diagram showing a basic circuit composed of basic cells on a gate array.

FIG. 3 illustrates a NAND circuit.

FIG. 4 shows one MOS constituting the gate array of the present invention.
FIG. 4 is a diagram illustrating a cross-sectional structure of a transistor.

[Explanation of symbols]

101. Insulated state part of photoinduced phase change material 102. Light-irradiated part of photo-induced phase change material and conductive part after light irradiation 201. PMOS 202. NMOS 203. Gate electrode terminal section 301. Conductor wiring section 401. Photoinduced phase change material layer 402. Gate electrode 403. Insulating layer 404. Drain 405. Source

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/88 Z (72) Inventor Masato Kakihana 6-1 Enogaoka, Aoba-ku, Aoba-ku, Yokohama, Kanagawa Prefecture 603 F term (reference) 4G002 AA06 AE05 5F033 GG04 HH31 HH35 PP26 QQ54 QQ73 VV17 XX33 XX36 5F064 AA03 BB07 CC12 EE31 FF05 FF29 FF42

Claims (7)

[Claims] In a gate array formed by connecting a plurality of transistors formed on a substrate, the connection portion can exist in any of a stable insulating state and a metastable conductor state. A gate array comprising a conductive state of a light-induced phase change material. 2. The gate array according to claim 1, wherein the conductor state of the photo-induced phase change material is capable of undergoing a phase transition by heating to become an insulating state. 3. The photo-induced phase change material according to claim 1, wherein the insulated state, which is a stable state, and the conductor state, which is a metastable state, can be reversibly phase-changed by light or heat to be in a mutual state. The gate array according to claim 1. 4. The method according to claim 1, wherein the life of the conductor state in the metastable state, that is, the time required for the electric conductivity of the conductor state to become half the initial value, is one year or more. Item 4. The gate array according to Item 3. 5. The gate array according to claim 4, wherein the light has energy in a visible or infrared region. 6. A method for forming a logic circuit of a gate array in which a plurality of transistors formed on a substrate are connected, wherein the connection is made of a conductive state of the photo-induced phase transition material. 1) a step of opening the basic cells, which are the units of the gate array, in an insulated state of the photo-induced phase change material; and (2) a step of irradiating light using a mask having a wiring pattern only at a portion requiring connection. And a method for forming a gate array logic circuit. 7. A method of forming a logic circuit in a gate array, comprising a plurality of transistors formed on a substrate connected to each other, wherein the connection is made of a conductive state of the photo-induced phase transition material. 1) a step of opening the basic cells, which are the units of the gate array, in an insulated state of the photo-induced phase change material, and (2) a step of irradiating laser light along a wiring pattern only at a portion requiring connection. A method for forming a gate array logic circuit, comprising: