CN101271927A - HfO2 high dielectric constant thin-film capacitor and method for producing the same - Google Patents

Abstract

The invention proposes a _HfO2 gate dielectric thin film with low surface roughness, high dielectric constant, low leakage current and high interface quality and a preparation method for a MOS capacitor device thereof. It uses a silicon wafer as a substrate, and is characterized in that a layer of HfO ₂ film is deposited on it by pulse laser deposition technology, and then magnetron sputtering equipment is used to prepare the lower electrode and the upper pattern electrode. The invention obtains the _HfO2 gate dielectric thin film and its MOS capacitor with low surface roughness, high dielectric constant, low leakage current and high interface quality by using relatively low-cost pulse laser deposition equipment and post-nitrogen treatment.

Description

A kind of HfO2 high dielectric constant film capacitor and preparation method thereof

technical field

The invention relates to a capacitor with high dielectric constant (HfO ₂ ) and a preparation method thereof, belonging to the fields of microelectronics, dielectric material science and nanometer science and technology.

technical background

The increasing demand of information technology for higher integration (large capacity), high speed, and low power consumption integrated circuits makes the feature size of transistors smaller and smaller, but the physical limit of traditional _SiO2 gate thickness thinning hinders the device further miniaturization. At present, it is considered that a more feasible solution is to use high dielectric constant (k) materials (such as HfO ₂ ) to replace SiO ₂ . Replacing _SiO2 with an equivalent thickness of high-k material not only eliminates tunneling leakage, but also reduces power consumption by a factor of 10,000. In order to obtain high-quality gate dielectric films and their devices with high dielectric constant, a lot of research has been carried out internationally. However, most of the researches are focused on atomic layer deposition and chemical vapor phase methods, but there are few researches on the preparation of high-quality gate dielectric films with high dielectric constant and their devices by pulsed laser deposition.

Contents of the invention

The object of the present invention is to propose a gate dielectric with high dielectric constant, low surface roughness and low leakage current and a preparation method thereof for a MOS capacitor device.

The present invention is achieved like this. It uses a silicon wafer as a substrate, and deposits a layer of HfO ₂ film on it with pulsed laser deposition equipment. The HfO ₂ film is divided into two groups, one group is used for surface roughness detection, and the other group is used for MOS capacitor devices. The capacitor electrodes are deposited using magnetron sputtering equipment.

The preparation method of the present invention is:

1. Select the _HfO2 target with a purity of 99.99% as the deposition target material, place the _HfO2 target on the rotating target holder in the deposition chamber of the pulsed laser deposition equipment, adjust the target base distance to 4-5cm, and place the cleaned Si sheet ( P type, resistivity 8-13Ω·cm) placed on the substrate holder in the deposition chamber.

2. Pump the background vacuum of the deposition chamber to 2.0-2.5×10 ^-4 Pa, feed high-purity protective gas, adjust the rotation speed of the target platform and substrate support to 5-8 revolutions per minute, and control the laser frequency during the deposition process 4-5Hz, the energy density of each laser pulse is 3-4J/cm ² , and the deposition time is 10-30 minutes.

3. Select a Pt target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a Pt bottom electrode with a thickness of 100 nm on the back of the sample prepared in step 2.

4. Select the Pt target (or Ag target) with a purity of 99.99% as the sputtering target, and use the magnetron sputtering equipment to sputter 100nm thick Pt, Ag electrode patterns, and finally form a MOS capacitor as shown in Figure 1.

The high-purity gas is fed with high-purity oxygen to ensure that the oxygen bias in the deposition chamber is 2.0×10 ^-1 Pa. After the deposition is completed, the prepared film is annealed in a tube furnace at 500°C for 30 minutes in a nitrogen atmosphere. .

The high-purity gas may be fed with high-purity nitrogen to ionize the nitrogen, and at the same time ensure that the nitrogen bias in the deposition chamber is at 6 Pa. When the high-purity nitrogen is fed, annealing may not be required after the deposition is completed.

Compared with the prior art, the present invention has obvious advantages. We adopt the high-quality high dielectric constant gate dielectric thin film obtained by pulsed laser deposition equipment, and atomic layer deposition (ALD), chemical vapor deposition (CVD), metal organic Compared with chemical vapor deposition (MOCVD) and magnetron sputtering, the cost of pulsed laser deposition equipment is lower, and the chemical composition of the obtained film can be kept highly consistent with the target material.

Drawings and Description

Fig. 1 is the structural representation of the MOS capacitor prepared by the present invention

Fig. 2 is HfO prepared by the present invention _Thin film root mean square roughness of surface under electron microscope

Fig. 3, 4 are the capacitance test result of embodiment 1 and 2

Detailed ways

In conjunction with content of the present invention, provide following embodiment:

Example 1:

1. Select the HfO ₂ target with a purity of 99.99% as the deposition target, place the HfO ₂ target on the rotating target holder in the deposition chamber of the pulsed laser deposition equipment, adjust the base distance of the target to 4 cm, place the cleaned Si sheet (P type , resistivity 8-13Ω·cm) placed on the substrate holder in the deposition chamber. Pump the background vacuum of the deposition chamber to 2.0-2.5×10 ^-4 Pa, feed high-purity oxygen to ensure that the oxygen bias of the deposition chamber is at 2.0×10 ^-1 Pa, and adjust the rotation speed of the target stage and substrate holder to 8 rpm During the deposition process, the frequency of the laser was controlled to be 5 Hz, and the energy density of each pulse of the laser was 4 J/cm ² . The deposition was performed for 30 min, and the prepared film was annealed in a tube furnace at 500° C. for 30 min in a nitrogen atmosphere.

2. Select a Pt target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a 100 nm thick Pt bottom electrode on the back of the sample prepared in step 1.

3. Select a Pt target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a Pt electrode pattern with a thickness of 100 nm on the front side of the sample prepared in step 2 by covering the mask plate.

The test shows that the root mean square roughness of the surface of the HfO ₂ film prepared by pulsed laser deposition equipment is only 0.446nm, and the band gap is 5.3 eV. The dielectric constant of the MOS capacitor composed of the HfO ₂ film is as high as 29.3, the maximum capacitance is 784PF, The current is 4.32×10 ^-8 A/cm ² when the gate voltage is -1.5 volts. At the same time, nitrogen annealing effectively eliminates the interface layer between the HfO ₂ film and the Si substrate, so that the capacitor has a better interface quality.

Example 2:

1. Select the HfO ₂ target with a purity of 99.99% as the deposition target, place the HfO ₂ target on the rotating target holder in the deposition chamber of the pulsed laser deposition equipment, adjust the target base distance to 5 cm, and place the cleaned Si sheet (P type , resistivity 8-13Ω·cm) placed on the substrate holder in the deposition chamber. Pump the background vacuum of the deposition chamber to 2.0-2.5×10 ^-4 Pa, feed high-purity nitrogen gas to ionize the nitrogen gas, and at the same time ensure that the nitrogen bias in the deposition chamber is at 6 Pa, adjust the rotation speed of the target stage and the substrate holder to 5 rpm Minutes, the frequency of the laser is controlled at 4 Hz during the deposition process, the energy density of each pulse of the laser is 4 J/cm ² , and the deposition is 30 min.

2. Select a Pt target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a 100 nm thick Pt bottom electrode on the back of the sample prepared in step 1.

3. Select an Ag target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a 100nm-thick Ag electrode pattern on the front of the sample prepared in step 2 by covering the mask.

The test shows that the root mean square roughness of the surface of the HfO ₂ film prepared by the pulsed laser deposition equipment is only 0.203nm, as shown in Figure 2, the dielectric constant of the MOS capacitor composed of the HfO ₂ film is as high as 40.3, the maximum capacitance is 2158PF, and the leakage current is at the gate The pole voltage is 3.73×10 ^-8 A/cm ² at -1.5 volts.

Claims (4)

1, a kind of HfO _High dielectric constant film capacitor, it is substrate with silicon chip, it is characterized in that with pulsed laser deposition technology deposits one _deck HfO on it Thin film, prepare low electrode and with magnetron sputtering equipment again The upper pattern electrode. 2, a kind of HfO _High dielectric constant film capacitor preparation method, it is characterized in that the steps are: a. Select the HfO ₂ target with a purity of 99.99% as the deposition target material, place the HfO ₂ target on the rotating target holder in the deposition chamber of the pulsed laser deposition equipment, adjust the target base distance to 4-5cm, and place the cleaned Si sheet on the substrate holder in the deposition chamber; b. Pump the background vacuum of the deposition chamber to 2.0-2.5×10 ^-4 Pa, feed high-purity protective gas, adjust the rotation speed of the target platform and substrate support to 5-8 revolutions per minute, and control the laser frequency during the deposition process 4-5Hz, the energy density of each laser pulse is 3-4J/cm ² , and the deposition time is 10-30 minutes; c. Select a Pt target with a purity of 99.99% as the sputtering target, and use a magnetron sputtering device to sputter a 100nm thick Pt bottom electrode on the back of the sample prepared in step 2; d. Selecting a Pt target with a purity of 99.99% as the sputtering target, or selecting an Ag target with a purity of 99.99% as the sputtering target, using the magnetron sputtering equipment to cover the front of the sample prepared in step 3 by covering the mask The plate method sputters 100nm thick Pt or Ag electrode patterns, and finally forms a MOS capacitor. 3. The preparation method of a _HfO2 high dielectric constant film capacitor according to claim 1 or 2, characterized in that the high-purity protective gas is fed high-purity oxygen to ensure that the oxygen bias in the deposition chamber is at 2.0 ×10 ^-1 Pa, after the deposition is completed, the prepared film is annealed in a tube furnace at 500°C in a nitrogen atmosphere for 30 minutes. 4. A method for preparing a _HfO2 high dielectric constant film capacitor according to claim 1 or 2, characterized in that the high-purity protective gas is fed with high-purity nitrogen to ionize the nitrogen while ensuring that the deposition chamber Nitrogen bias at 6Pa.

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