JPS5913608A - Manufacture of thin metallic nitride film - Google Patents

Abstract

PURPOSE:To obtain easily a thin metallic nitride film with small internal stress and low specific resistance by applying bias voltage having a wave-form repeating alternately a zero state and a negative state of the voltage to a substrate in reactive sputtering. CONSTITUTION:Nitrogen is introduced into a chamber up to a prescribed partial pressure, Ar is introduced up to a prescribed total pressure, and electric discharge is started. Bias voltage having a wave-form repeating alternately a zero state and a negative state is applied to a substrate from a bias power source, and a thin metallic nitride film is deposited by reactive sputtering. By this method a thin metallic nitride film with small internal stress and low specific resistance is easily obtd. The film is used as the material of electrodes of a semiconductor integrated circuit, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal nitride thin film with low internal stress and low specific resistance.

In general, nitrides of high-melting point metals such as titanium, molybdenum, and tantalum have extremely high melting points and high mechanical hardness, and are thermally and chemically stable. Recently, it has been put into practical use as one of the highly heat-resistant electrodes for integrated circuits.

When using a metal nitride thin film as an electrode material for a semi-dedicated integrated circuit, the first condition is that the specific resistance is low.

Generally, it is known that nitrides such as titanium and zirconium have a lower resistivity than the original metal element when compared in bulk. However, in thin films with a thickness of several 100 to several 100 X used as electrode materials, the resistivity generally tends to be high due to various scattering mechanisms, and reducing this is one of the advanced technologies. ing.

For example, when a titanium nitride thin film is obtained by reactive sputtering in a nitrogen/argon mixed gas, increasing the nitrogen partial pressure and the nitrogen/argon mixed gas pressure will reduce the effect of impurities in the elemental composition of the titanium nitride thin film. Since the specific resistance increases, the pressure is usually set to the minimum pressure that can sustain the discharge. Furthermore, it is effective to apply a negative DC bias voltage to the substrate in order to further lower the resistivity.

FIG. 1 shows a schematic diagram of a sputtering apparatus in which a negative bias voltage is applied to a substrate. In the figure, 1 is a vacuum chamber, 2 is an evacuation thread, and 3 is titanium.

4 is a metal target such as molybdenum or tantalum, 4 is a thin plate, 5 is a high frequency electric circuit, 6 is a substrate, 7 is a bias electrolytic corrosion, 8 is a gas inlet, and 9 is a flow rate control valve. FIGS. 2 and 3 are graphs showing the effect of substrate bias on the specific resistance of a titanium nitride thin film and the internal stress generated within the film, respectively. ρ indicates specific resistance, and σ indicates internal stress (shown as a solid line). This data indicates that the nitrogen partial pressure is 2.8
mTOrr.

Nitrogen/argon mixed gas pressure 16.8 m Torr
, in the case of high frequency power of 400W.

Thus, although application of substrate bias is extremely effective in reducing the resistivity ρ of titanium nitride thin films,
], significant internal stress σ occurs within the film, which makes it difficult to form fine patterns due to wafer (-) when manufacturing semiconducting integrated circuits, and cracks and peeling occur when the wafer is thick. This caused serious problems such as:

One way to solve this problem is to set the bias voltage in the transition region shown in Figure 2, that is, the point where resistivity and internal stress suddenly change, to obtain a film with intermediate resistivity and internal stress. In addition, the range of bias voltage that determines the transition region is extremely narrow, making it extremely difficult to obtain the desired value.

In order to solve the above-mentioned problems, the present invention aims to reduce the internal stress of a metal nitride thin film by applying a bias voltage that alternates between a zero state and a negative state as a substrate bias. Also, the purpose is to lower the specific resistance by 1 to a level that poses no problem in practice.

In order to achieve the above object, the present invention provides a method for manufacturing a metal nitride thin film having a folding property by reactive sputtering, in which a substrate bias is applied and the bias voltage is The situation was And a negative state! The gist of the invention is a method for manufacturing metal nitride 111iQ, which is characterized by using alternately repeated substrate biases.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments are merely illustrative, and that various changes and improvements may be made without departing from the spirit of the present invention.

The apparatus used to carry out the present invention is shown in FIG. 1, and the procedure is to first evacuate the inside of the chamber 1, and then pump nitrogen through the flow control valve provided at the gas inlet 8 until a predetermined partial pressure is reached. This is introduced by adjusting 9. Subsequently, argon is introduced until the total pressure reaches a predetermined pressure, and then discharge is started to deposit a metal nitride thin film. To the substrate bias power supply 7, a bias voltage is applied with a waveform that alternates between a low state, a negative fall, and a low state. FIG. 4 shows an example of the bias voltage wave tb, which is a rectangular wave with a duty of 1/2. The magnitude of the voltage is, for example, -50V,
The period T is, for example, 100 mB. FIG. 5 shows another example of the bias voltage waveform, which is a pulsating bias voltage waveform that can be easily obtained by simply half-wave rectifying the commercial power line. The magnitude of the voltage -V is given by v=iv, 6, where vrms is the effective value of the AC voltage before rectification. The period T is 20nI8 when the image frequency is 50 Hz.

As an example, a titanium nitride thin film with a nitrogen partial pressure of 2.8 m'ro
rr, nitrogen/argon mixed gas pressure 16.8 m
Torr.

The specific resistance and internal structure of the titanium nitride thin film deposited by applying a negative pulsating current bias voltage obtained by half-wave rectification of AC voltage with an effective value of 30 V, 40 V, and 50 V as a substrate bias voltage with a high frequency power of 400 W. Stresses are shown in dashed lines in FIGS. 2 and 3. However, the horizontal axis represents the effective value of the bias voltage. From the data shown by the broken lines in Figures 2 and 3, it is clear that the rapid change in resistivity observed when DC bias voltage is applied is relaxed, and that the region where internal stress begins to occur is located at high bias voltage. It can be seen that it is possible to easily obtain a film with small internal stress and low specific resistance to the extent that it does not pose a problem in practice.

As mentioned above, when considering the mechanism of growth of a titanium nitride thin film when applying a bias voltage that alternately repeats zero and negative values, the specific resistance obtained when the substrate pipe is zero is large. A film intermediate between the two is formed by alternately growing a film with small internal stress and a film with large internal stress but small resistivity obtained in the case of substrate bias or negative i'i. As a result, it can be considered as a membrane that combines the advantages of both.

As explained below, according to the present invention, the substrate bias voltage in reactive sputtering is a bias voltage IJE with a waveform in which the voltage alternates between positive and negative voltages.
By applying , a metal nitride # film with low internal stress and low resistivity can be easily obtained, and this thin film can be used as a part of the electrode of a semiconductor integrated circuit, for example, as a diffusion barrier layer. OJ', a semiconductor integrated circuit with excellent heat resistance and reliability has a sharp tip and a young fruit that can be realized in a k-adjacent manner.

4.1 Explanation of 111) Figure 1 is a schematic diagram of the sputtering equipment, and Figures 2 and 3 show the specific resistance and internal stress of a titanium nitride thin film formed by high-frequency reactive sputtering, respectively. The effect of applying a bias voltage with a waveform in which the voltage alternates between low and negative values as a substrate bias and the effects of applying a bias voltage (Hafuna)
4 and 5 show examples of the bias voltage waveforms that characterize the present invention, and are rectangular and pulsating bias voltages, respectively.

1... Vacuum chamber, 2... Exhaust system, 3... Metal target, 4... Shiyahei plate, 5... Cylindrical frequency %Vtx circuit, 6... Substrate, 7... Bias electrolytic erosion, 8...・Gas inlet, 9...Flow control valve Patent applicant Figure 1 Figure 2 Vs (V) Figure 3 Vs (V)

Claims (1)

[Claims] In a method for manufacturing a metal nitride thin film having electrical properties by a reactive sputtering method, a substrate bias is applied, and the bias voltage is alternately in a low state and a negative state. A method for producing a metal nitride thin film, characterized in that a substrate bias is used.