JPH06252274A - Formation of electronic circuit - Google Patents

Abstract

PURPOSE:To uniform the oxidation rate of a surface, and obtain an uniform oxide film of little unevenness, by performing anodizing oxidation in the state that the temperature around a metal wiring kept lower than or equal to 10 deg.C, preferably, 0 deg.C. CONSTITUTION:Wirings 14a, 14b are formed by patterning an aluminum film formed on a substrate 10. Tartanic acid is dissolved in ethylene glycol and neutralized by adding ammonia aqueous solution. The solution is cooled at -8-+2 deg.C, in which the wiring 14a, 14b are subjected to anodizing oxidation by passing currents through them. Thereby aluminum oxide films 16a, 16b of 1500-3000Angstrom in thickness are formed. After impurity regions 17a, 17b are formed by a plasma doping method, activation is performed by a laser annealing method. A silicon oxide film 18 of 3000Angstrom in thickness is formed as an layer insulating film by a plasma CVD method. After a contact hole is formed, wirings 19a, 19b are formed by using a mulitayered film of titanium nitride and aluminum. Since an uniform anodic oxide film can be obtained, electric characteristics are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to metal wiring for electronic circuits used in microelectronic products. The present invention particularly relates to metal wiring formed on a semiconductor region.

[0002]

2. Description of the Related Art Conventionally, in order to improve the insulation between metal wirings, a method of oxidizing the periphery (side surface and / or upper surface) of the metal wirings by an anodic oxidation method (see, for example, JP-A-55).
-18056) has been reported.

[0003]

Conventionally, as metal wiring, tantalum, aluminum, titanium, tungsten,
Molybdenum and their silicides were widely used. Generally, aluminum was used. Pure aluminum is easily recrystallized and grain grown by heat treatment at 250 ° C. or higher, the wiring structure is physically deformed (this phenomenon is called hillock), stress is applied to the wiring, and disconnection easily occurs. The addition of 5% or less of silicon or copper to aluminum prevented the formation of hillocks.

However, it has been found that a large number of pores are formed when anodizing aluminum having such an additive. The presence of such holes increases the irregularities on the surface of the metal wiring, increasing the possibility of causing pinholes in the interlayer insulating material thereabove. Further, in the step of introducing the high-speed impurity ions into the semiconductor region using such a metal wiring as a mask, there is a risk that the impurities may be implanted through the hole to the lower portion of the metal wiring.

Such a problem is not limited to aluminum to which silicon or copper is added, but there is a possibility that the metal wiring is generally a polycrystal. That is, since it is a polycrystalline body, a local difference occurs in the rate of anodic oxidation,
It was observed not a little that the difference was magnified by some factor, resulting in unevenness on the surface of the anodic oxide film. In particular, the change of the film thickness was large, such as a stepped portion, and it was remarkable in a portion where hillocks were likely to occur.

The present invention has been made in view of the above problems, and provides a method for uniformly promoting anodic oxidation of metal wiring, and a semiconductor integrated circuit using such a method. And a method of manufacturing an electronic circuit such as.

[0007]

The first structure of the present invention is as follows.
In the step of oxidizing the metal wiring used in the electronic circuit by the anodic oxidation method, the anodic oxidation is performed at a temperature of 10 ° C. or lower, preferably 0 ° C. or lower. As a result of consideration by the present inventors, the lower the temperature, the better the result. On the other hand, when the anodic oxidation is performed at such a low temperature, the solvent solidifies. For example, if the solvent is water, the freezing point is slightly lowered due to the presence of solute, but it is impossible to continue the anodization at a temperature of -5 ° C or lower.

With respect to this point, in the present invention, by using a material having a low freezing point due to the solvent, it was possible to perform anodic oxidation even at a lower temperature. For example, when the solvent contained 50% or more of ethylene glycol, the freezing point was lowered to -5 ° C or lower, and for example, anodic oxidation could be performed even at -11 ° C.

The present inventor considers that the effect can be obtained by performing anodic oxidation at a low temperature as follows. Usually in anodization,
Oxide has a high resistance, so even if non-uniformity occurs in anodic oxidation for some reason, the current concentrates where the oxidation is delayed (the oxide is thin and the resistance is small), eliminating the delay in oxidation. . As a result, ideally, anodic oxidation proceeds uniformly.

However, in practice there are non-uniformities in anodic oxidation. It is considered by the inventors to be temperature dependent. For some reason, the area where anodic oxidation is actively occurring generates heat due to a chemical reaction and the temperature rises. For this reason, the resistance of the oxide in this portion is lowered.
If the resistance of the oxide at the active anodization site is smaller than the resistance of the oxide at the non-active anodization site due to the heat generation of that site, the active site anodization is As it progresses further, the oxide in that part becomes thicker.

Further, in the anodic oxidation, as a result of excessive reaction, electrolysis may occur and oxygen bubbles may be generated on the oxide surface. However, such bubbles have poor heat conductivity, resulting in nonuniform reaction. It only promotes

If this hypothesis is correct, it is possible to obtain good results by carrying out the anodic oxidation extremely slowly to such an extent that the heat of reaction does not cause a temperature distribution. Then, it was shown that, by actually lowering the oxidation rate, a good anodic oxide with few irregularities can be obtained. However, reducing the oxidation rate means increasing the treatment time, which is unacceptable industrially.

Another solution according to the above hypothesis is to quickly remove the heat of reaction by lowering the temperature as in the present invention. Further, if the temperature of the solvent is low, oxygen and the like generated by the reaction are not dissolved in the solvent to form bubbles, so that the temperature can be further homogenized.

As described above, since the present invention attaches great importance to the spatial uniformity of temperature, it is desirable to avoid the temporal variation of temperature as much as possible in carrying out the present invention. It is desired to keep the temperature fluctuation at 5 ° C. or lower, preferably 1 ° C. or lower. In the present invention, as the electrolyte, weak organic acids represented by organic acids such as tartaric acid, citric acid, and oxalic acid are preferable to strong acids such as sulfuric acid and hydrochloric acid, and particularly, these acids are neutralized with a weak alkali. Good results can be obtained by using it.

A second structure of the present invention is a semiconductor circuit to which the above-mentioned first structure is applied, and a first step of forming a metal wiring on a semiconductor region through an insulating film and a step of forming the metal wiring. It has a second step of oxidizing the surroundings by an anodic oxidation method at a temperature of 10 ° C. or lower, preferably 0 ° C. or lower, and a third step of irradiating the semiconductor region with high-energy ions after the second step. It is characterized by It goes without saying that the technique shown in the first configuration may be used for this second step.

In the second structure, since the anodic oxide film has very few irregularities, even if fast ions are introduced, the probability that they are mistakenly introduced below the metal wiring is significantly reduced. Therefore, the second configuration of the present invention is effective in manufacturing a top gate type thin film transistor (TFT) or the like using a metal wiring as a gate electrode.

The third structure of the present invention is also an application of the above-mentioned first structure to an electronic circuit manufacturing technique, and includes a first step of forming metal wiring and a temperature of 250 ° C. or higher after the first step. And a third step of oxidizing the periphery of the metal wiring by an anodic oxidation method at a temperature of 10 ° C. or lower, preferably 0 ° C. or lower.

This technique is effective in a process in which some heat treatment is required before anodizing. For example, the steps of film formation and etching. Generally, when a temperature is applied, a pure metal material undergoes recrystallization and grain growth, and hillocks are generated, so that non-uniform anodic oxidation is likely to occur. Even if some impurities are added to avoid this, the anodic oxide film becomes uneven. Therefore, the effect of the present invention is great in such an environment that requires heat treatment.

[0019]

EXAMPLE This example relates to a method of manufacturing a semiconductor circuit including a TFT. FIG. 1 shows a cross-sectional view of the manufacturing process of this embodiment. First, a 2000 Å-thick silicon oxide base film 11 was formed on a substrate (Corning 7059) 10 by sputtering. Further, an amorphous silicon film having a thickness of 500 to 1500 Å, for example 1500 Å, was deposited by the plasma CVD method. Then, this was annealed at 600 ° C. for 48 hours in a reducing atmosphere to be crystallized. The crystallization step may be a method using strong light such as a laser. Then, the obtained crystalline silicon film was patterned to form island-shaped silicon regions 12a and 12b.

Next, a thickness of 10 is obtained by the sputtering method.
A silicon oxide film 13 of 00Å is deposited as a gate insulating film,
Subsequently, a thickness of 6000 was obtained by the sputtering method.
~ 8000Å, eg 6000Å aluminum film (2
% Silicon). It is desirable to add 0.5 to 5% of silicon or 0.2 to 2% of copper to aluminum. This is a later step, 250-35
Since the heat treatment is performed at 0 ° C., hillocks are generated unless these impurities are contained. It should be noted that it is desirable to continuously perform the film forming process of silicon oxide and aluminum. Then, the aluminum film was patterned to form the wirings 14a and 14b. The wiring 14b functions as a gate electrode.

Further, after applying photo-nice (photosensitive polyimide), this is patterned, and
Baking at 350 ° C., eg 300 ° C., selectively forms the polyimide mask 15 (against anodization). This mask may be provided in a place where a contact is formed later or a place where a wiring is divided. (Fig. 1 (A))

Subsequently, anodic oxidation is performed. Dissolve tartaric acid in ethylene glycol, 1-5%, for example 3%
PH of the solution prepared by adding ammonia solution.
Was set to about 7. Then, using a platinum mesh electrode as a cathode and the substrate 10 as an anode, the solution was cooled to −8 to + 2 ° C., for example −3 ° C., and an electric current was passed through the wirings 14a and 14b to start anodization.

Initially, the voltage is 3 to 6 V / min, for example 4 V / min.
The current is applied so that the voltage rises in
The voltage rise is stopped at a stage of up to 250 V, for example 220 V, and the voltage is maintained at a constant voltage, and the current is 20 μA / cm ^2.
I kept that state until. This results in a thickness of 1500
~ 3000Å, for example 2000Å aluminum oxide 1
6a and 16b were formed. The existing portion of the polyimide mask 15 was not anodized due to the masking effect. The time required for anodization was 40 to 70 minutes, typically 55 minutes. (Fig. 1 (B))

Next, impurities (phosphorus or boron) were implanted into the silicon region by plasma doping using the wiring 14b as a mask. When phosphorus is injected, phosphine (PH ₃ ) is used as the doping gas, and the acceleration voltage may be set to 60 to 90 kV, for example 80 kV. In the case of implanting boron, diborane (B ₂ H ₆ ) may be used as a doping gas and the acceleration voltage may be set to 40 to 70 kV, for example, 65 kV. Thus, the impurity regions 17a and 17b were formed. (Fig. 1 (C))

Further, the implanted impurities were activated by the laser annealing method. The laser used was a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec), and the energy density on the irradiation surface was 20.
It was set to 0 to 350 mJ / cm ² , for example, 300 mJ / cm ² . At the time of laser irradiation, the substrate is 200 to 400 ° C.,
For example, you may heat to 300 degreeC. The laser used is a XeF excimer laser (wavelength 353 nm),
A XeCl excimer laser (wavelength 308 nm) may be used.

The polyimide mask 15 was left until the laser annealing step. This is especially for two substrates
This is because when laser irradiation is performed in a state of being heated to 00 ° C. or higher, the exposed portion of aluminum is significantly damaged. To remove the polyimide mask, ashing may be performed in oxygen plasma.

Then, a silicon oxide film 18 having a thickness of 3000 Å is formed.
Is formed by plasma CVD as an interlayer insulator,
A contact hole is formed in this, and the wiring 1 is made of a metal material, for example, a multilayer film of titanium nitride and aluminum.
9a and 19b were formed. The wiring 19a is connected to the wiring 14a and T
One of the impurity regions 17a of the FT is connected. The semiconductor circuit is completed through the above steps.

The electrical characteristics of the obtained anodic oxide film 16 were good, and it was a film having a thickness of 2000 Å and a withstand voltage of 100 V or more. Also, almost no defects occurred. In the conventional method, when pure aluminum was used, uniform aluminum oxide could be obtained. However, since pure aluminum easily produces hillocks when heated to 100 ° C. or higher, it is particularly preferable as in this example. It was difficult to use when there was a heating step (photo nice baking).
On the other hand, in order to avoid hillocks, good anodic oxide could not be obtained by adding aluminum or silicon to copper. The present invention solves such a contradiction. The characteristics of the manufactured TFT were not inferior to the conventional one.

[0029]

According to the present invention, a uniform anodic oxide film can be obtained. As described in Examples, the electrical characteristics of the anodic oxide film thus obtained are extremely excellent. Although aluminum is used in the examples, it goes without saying that the same effect can be expected with other metal materials such as tantalum, titanium, tungsten, molybdenum, or their silicides or nitrides. Thus, the present invention is an industrially useful invention.

[Brief description of drawings]

1A to 1C show steps of manufacturing a semiconductor circuit in an example.

[Explanation of symbols]

 10 ... Substrate (Corning 7059) 11 ... Underlayer film (silicon oxide) 12 ... Island silicon region (crystalline silicon) 13 ... Gate insulating film (silicon oxide) 14 ... Metal wiring (aluminum) ) 15 ... Polyimide mask 16 ... Anodic oxide (aluminum oxide) 17 ... Impurity region 18 ... Interlayer insulator (silicon oxide) 19 ... Metal wiring (titanium nitride / aluminum)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Takemura 398 Hase, Atsugi, Kanagawa Prefecture Semiconductor Energy Research Institute Co., Ltd.

Claims (7)

[Claims] 1. A method of manufacturing an electronic circuit, wherein anodic oxidation is performed at a temperature of 10 ° C. or lower in a step of oxidizing the periphery of a metal wiring used in the electronic circuit by an anodic oxidation method. 2. The method for manufacturing an electronic circuit according to claim 1, wherein the metal wiring contains aluminum as a main component and contains 5% or less of silicon or copper. 3. The method for manufacturing an electronic circuit according to claim 1, wherein the solvent for anodic oxidation contains 50% or more of ethylene glycol. 4. The method for manufacturing an electronic circuit according to claim 1, wherein the metal wiring is provided across the island-shaped semiconductor region with an insulating film interposed therebetween. 5. A first step of forming a metal wiring on a semiconductor region via an insulating coating, and a step of surrounding a periphery of the metal wiring by 10 steps.
Fabrication of an electronic circuit comprising a second step of oxidizing by an anodic oxidation method at a temperature of ℃ or less, and a third step of irradiating a semiconductor region with high-energy ions after the second step. Method. 6. A first step of forming metal wiring, and a first step.
After the step of (2), there is provided a second step of applying a temperature of 250 ° C. or higher, and a third step of oxidizing the periphery of the metal wiring by an anodic oxidation method at a temperature of 10 ° C. or lower. Of manufacturing. 7. The method for manufacturing an electronic circuit according to claim 6, wherein the metal wiring contains aluminum as a main component and contains 5% or less of silicon or copper.