JP3179779B2 - Method for manufacturing nitride insulating film - Google Patents

Description

The present invention relates to a dielectric film for a capacitor of a semiconductor integrated circuit,
Alternatively, the present invention relates to a method for forming an insulating film such as an interlayer insulating film or a gate insulating film of an insulating gate field effect transistor of an active liquid crystal display by a sputtering method.

[Background Art] Active elements or semiconductor integrated circuits using an insulator film manufactured by a chemical vapor deposition method or the like, or capacitors using a dielectric film have been widely noted.

Conventionally, for example, when a silicon nitride film is formed, this insulating film (hereinafter simply referred to as an insulating film or an insulating film because the dielectric film of the capacitor is also insulating) is formed by a chemical vapor deposition method using a plasma reaction of silane and ammonia. Therefore, the number of charge trapping centers is large, and the unit density at the interface is as large as 10 ¹² cm ⁻² .

As another method of producing an insulator at such a low temperature, 10
A sputtering method using 0% to 80% of Ar atoms as a sputtering gas is known.

This is because the probability that an inert gas such as Ar or the like hits the target material (sputtering yield) is high.
The present inventors have conducted extensive studies on the characteristics of an insulating film formed by a sputtering method, and as a result, the lower formed surface showing the performance of the insulating film, that is, the lower electrode active layer and the formed insulating film interface It was found that the interface states varied greatly with the amount of argon. In particular, as an extreme example, when silicon nitride is used as a capacitor or a gate insulator, the silicon component (Si
Component) form clusters (groups of grains having a particle size of 5 to 50 °). The deviation (deterioration) of the flat band voltage from the ideal value, which reflects the number of fixed charges in the insulating film due to the damage of the cluster and the underlying surface, and the decrease in the withstand voltage largely depend on the ratio of Ar gas during sputtering. I found that.

Further, it has been attempted to form a dielectric film of a capacitor by a photo CVD method. Although there is no reaction damage with the underlying semiconductor or electrode material and an interface state density of about 2 × 10 ¹⁰ eV ⁻¹ cm ⁻² is obtained, the time required for film formation is long (deposition speed Was very slow) and was not suitable for industrial applications. Further, since hydrogen is used to induce a hot electron effect, there is a problem in long-term characteristics.

[Object of the present invention] The present invention is a method for solving the conventional problems, and it is possible to reduce the presence of metal or semiconductor clusters, pinholes and the like in a film of good characteristics such as titanium nitride and tantalum nitride. Another object of the present invention is to provide a method for manufacturing a nitride film formed without using hydrogen in a low-temperature process.

“Configuration of the Invention” The configuration of the present invention relates to a method for manufacturing a nitride film for forming a metal nitride film such as a resistor such as titanium nitride or tantalum nitride.

In the present invention, such an insulating film or a resistive film is formed by a sputtering method. The gas used for sputtering is nitride,
For example, nitrogen is 75% by volume or more with respect to an inert gas such as argon, more preferably a nitride gas which does not use any inert gas, in particular, a metal nitride or a metal target is sputtered under a condition of only nitrogen to obtain a nitride. It is characterized in that the film is produced by a lamination method.

In the sputtering, a gas containing a sputtering gas as a part of a component of the formed film, for example, in the case of a silicon nitride film, nitrogen is set to 100% or 75 to 100% by volume, and a target of silicon nitride is set to a high frequency (RF). This is performed using a sputtering method.
Then, the nitriding reaction with the sputtering gas, nitrogen, can be more completely performed while the target material is flying.

In order to further promote this, a gas containing a halogen element is added simultaneously to the nitride gas in an amount of 0.2 to 20% by volume at the same time, thereby neutralizing alkali ions which are simultaneously unintentionally introduced into silicide, It is also possible to neutralize unpaired bonds.

As the sputtering method used in the present invention, any method such as RF sputtering and DC sputtering can be used, but the sputtering target is a nitride having poor conductivity, such as Si
For ₃ N ₄ or the like of the metal nitride, it is preferable to use a 13.56MHz high-frequency RF magnetron sputtering to sustain stable discharge.

Nitrogen (N ₂ ), ammonia (N
H ₃ ) and the like. In particular, when high-purity nitrogen vaporized from liquid nitrogen is used, there is no unnecessary silicon or atoms taken into the nitride insulating film, so that there is no very good pinhole, little dielectric damage, and high withstand voltage. An insulating film with no large variation was obtained on the surface on which the film was formed.

Representative examples of the nitride insulating film include silicon nitride and aluminum nitride. As the resistor nitride, tantalum nitride and titanium nitride are mainly used. Nitrogen fluoride (NF ₃ , N ₂ F ₄ ), hydrogen fluoride (HF), fluorine (F ₂ ), or Freon gas can be used as the fluoride gas for the halogen element to be added to these. NF ₃ which is easily decomposed chemically and easy to handle is easy to use. As the chloride gas, carbon tetrachloride (CCl ₄ ), chlorine (Cl ₂ ), hydrogen chloride (HCl) or the like can be used.

The amount of these nitrogen fluorides is, for example, 0.2 to 20% by volume based on the nitride gas such as nitrogen. These halogen elements are effective in neutralizing alkali ions such as sodium in the nitride insulator and neutralizing unpaired metal bonds by heat treatment. It is not good because there is a possibility to do it. Generally, a halogen element of 0.01 to 5 atomic% of the total number of elements was mixed in the coating.

 Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 As shown in FIG. 1 (A), a silicon nitride film was formed on a silicon semiconductor (1) by the method of the present invention, and a 1 mmφ aluminum electrode was formed thereon by electron beam evaporation. FIG. 2 shows the results of the examination. FIG. 2 shows the flat band voltage deviation (ΔV _FB ) characteristic in the CV characteristic (FIG. 1 (B)) when the MIS (aluminum metal-silicon nitride insulating film-silicon semiconductor) structure is employed. .

An insulating film of silicon nitride was formed thereon by the method of the present invention. The conditions are shown below.

Target Si ₃ N ₄ 90% Reaction gas N ₂ 100% by volume to 0% by volume Ar 0% to 100% by volume Reaction pressure 0.05torr Rf power 500W Substrate temperature 200 ° C Distance between substrate targets 150mm Compared to 100% Ar gas It can be seen that the deviation from the ideal value of the flat band voltage, in which the amount of Ar gas is smaller than the amount of the nitriding gas and 25% by volume or less, is reduced.

As shown in FIG. 2, a BT (bias-temperature) treatment was performed, and a negative bias voltage of 2 × 10 ⁶ V / cm was applied to the gate electrode side.
The solution was added at 50 ° C. for 30 minutes, and a positive bias voltage was further applied under the same conditions. The difference between them, that is, the deviation of the flat band voltage (ΔVFB) was as high as 13 V when Ar was 100%. In addition, those produced by the plasma CVD method had 11.5 V (31) as shown in (31). However, when this film is formed with 100% nitrogen, the voltage is 0.5 V or less (3
4) There was only. Furthermore, when a small amount of a halogen element was added thereto, the value sharply decreased by a further factor.

From these facts, activated Ar atoms present in the reaction atmosphere at the time of film formation by sputtering affect the film quality of the insulating film, and it is desirable to perform sputtering film formation by reducing the presence of Ar atoms as much as possible. It has been found.

The reason is that Ar interferes with the reaction of one of the film components, metal and nitrogen, during sputtering due to Ar ions, and the stoichiometry is well matched (the ratio of Si ₃ to N ₄ Is satisfied even at the micro level).
It is also conceivable that Ar ions or activated Ar atoms collide with the interface, causing damage or defects at the interface and causing fixed charge generation.

When an insulating film is formed in an atmosphere in which Ar gas is mixed at a ratio of 25% or less, the distance between the target and the substrate is set longer than that in the case where the Ar gas is formed at 0%, so that the Ar gas is reduced to 0%.
It is possible to obtain an insulating film having substantially the same film quality as that of the case of manufacturing by (1). Further, the gate insulating film formed by mixing the Ar gas at a ratio of 25% or less is irradiated with excimer laser light, flash annealing is performed, and the halogen elements such as fluorine introduced into the film are activated, and the silicon is imperfect. It was also possible to neutralize the bond with the bond and remove the cause of the generation of fixed charges in the membrane.

Further, it is preferable that all materials used for sputtering have high purity. It is necessary to use not all metals or semiconductors such as silicon nitride, titanium nitride, aluminum nitride, and tantalum nitride, but all of which have undergone a nitridation reaction.
The sputtering target had a purity of 3N or more.

Embodiment 2 FIG. 3 shows another embodiment of the present invention.

1Tr / Cell DRAM (Dynamic Memory) of this embodiment
The present invention was used for the production of one cell. In the drawing, one gate type field effect transistor (20) is formed on a semiconductor substrate as a source or drain (8), a drain or source (9), a gain electrode (7), and a gate insulating film (6).

In addition, a lower electrode (10), a silicon nitride dielectric (11),
A capacitor (21) composed of an upper electrode (12) is provided in series. A buried insulating film (5)
I have. This structure shows the shape of the memory cell of the stacked DRAM.

In this drawing, a dielectric film (11) of a capacitor was formed by coating a silicon nitride target of the present invention by a nitrogen sputtering method. Since silicon nitride has a relative dielectric constant of 6 and has excellent frequency characteristics up to high frequencies, it is coated with silicon oxide (with a relative dielectric constant of 3.
Large storage capacity can be obtained compared to 8).

In addition, this insulation gain type field effect transistor (20)
Gain insulation film is silicon oxide or 100% by thermal oxidation
Silicon oxide of a sputtering method using oxygen was used. However, even if this protective film was made of silicon nitride, the interface state with the silicon semiconductor was only 3 × 10 ¹⁰ cm ⁻² , which was good.

The lower electrode (10) of this capacitor (21) was formed using a silicon semiconductor to which phosphorus was added. However, this electrode material may be metal tantalum, tungsten, titanium, molybdenum, or a silicide thereof.

In this example, as shown in Example 1, a silicon nitride film (11) was formed on the lower electrode (10) by the sputtering method of the present invention. Further, a capacitor (21) having an upper electrode (12) formed of aluminum or a multilayer film of tantalum metal and aluminum was formed thereon. The thickness of silicon nitride is
It was 300-3000Å. Typically 500-1500Å, for example 10
00 °. However, since the relative permittivity of silicon oxide or the like is small, the thickness of the memory cell must be reduced to about 30 °. However, since silicon nitride formed by the method of the present invention has a large relative dielectric constant, its thickness can be, for example, 1000 °. As a result, it is possible to excel in insulating properties and reduce the presence of pinholes.

For this reason, in FIG. 5, the channel length of the insulated gain field effect transistor may be set to 0.1 to 1 μm, for example, 0.5 μm.
One memory (1 bit) could be manufactured.

In addition, in forming this silicon nitride, the silicon nitride is formed by a sputtering method containing no hydrogen, and the upper and lower electrodes are also formed by a sputtering method containing no hydrogen. It is also possible to prevent drift (diffusion) to the gain insulating film and to become a hot carrier trap center.

Embodiment 3 FIG. 4 shows a configuration in which cells of a dynamic memory are provided in a pair (2 bits).

In the drawing, a semiconductor substrate (1), a buried field insulating film (5), a drain or source (9) formed in a convex shape on a semiconductor surface, and a conductor electrode / lead (19) thereon are provided. On this side, the silicon oxide film (6) was formed as a gain insulating film. A pair of gain electrodes (7) and (7 ') are provided by anisotropic etching, and sources or drains (8) and (8') are provided. The boron ions are implanted into the channel forming regions (15) and (15 ') by forming the convex regions (9) and (19') and the field insulating film before forming the gain electrodes (7) and (7 '). (5) was used as a mask to form a concentration of 1 × 10 ^{15 to} 5 × 10 ¹⁶ cm ⁻³ . Then, the source or drain (8), (8 ') is set to 1
It was manufactured by ion implantation at a concentration of × 10 ¹⁹ to 1 × 10 ²¹ cm ⁻³ . In the capacitor (21), a lower electrode (10), a silicon nitride dielectric (11), and an upper electrode (12) were formed in the same manner as in Example 3 according to Examples 1 and 2. A 1Tr / Cell consisting of two bits in a size of 10 to 20 μm □ was made.

Further, in order not to use hydrogen which causes a hot carrier trap center to be formed in the gate insulating film, 0.1 to 1
Even with a channel length of μm, stable transistor characteristics could be obtained.

[Effects] All of these experiments show that nitrogen or nitride gas can be sputtered to produce a good-quality insulating film by reducing argon to zero or 25% or less, which is the reverse of the conventionally known main gas of argon. Based on the facts found in

According to the method of the present invention, a capacitor or a thin film transistor having very good characteristics can be easily formed only by a low-temperature process.

In addition, since the occurrence of hot carriers and fixed charges in the gate insulating film can be reduced, it is possible to provide a highly reliable transistor and capacitor with little characteristic change in long-term use.

The shape of the capacitor or the insulated gate transistor used in the present invention does not need to be a staggered transistor, but may be an inverted staggered transistor or a vertical channel transistor. Further, an insulated gate field effect transistor used as a part of a monolithic IC using single crystal instead of non-single crystal for silicon of the transistor may be used.

In addition, the capacitor may be a multilayered multilayer structure instead of a single-layer dielectric capacitor, or may be a horizontal arrangement in which electrodes are sandwiched between left and right rather than vertically.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention and its characteristics. FIG. 2 shows the relationship between the ratio of nitrogen and Ar gas at the time of forming the insulating film and the electrical characteristics. 3 and 4 show an embodiment of a semiconductor device which is a dynamic memory cell using the method of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/318 C23C 14/00-14/58

Claims (2)

(57) [Claims] 1. A nitride film for forming a tantalum nitride or titanium nitride film by a sputtering method using tantalum, titanium or a nitride thereof as a target in an atmosphere composed of nitrogen or a nitride gas and an inert gas. In the manufacturing method, the atmosphere contains nitrogen or a nitride gas at 75% by volume or more. 2. A method for producing a nitride film, wherein a titanium nitride film is formed by a sputtering method in an atmosphere consisting of nitrogen and argon by using titanium as a target, wherein the atmosphere contains 75% by volume or more of nitrogen. Characteristic method for forming a nitride film.