JP3949205B2 - Metal wiring sputtering equipment with magnetron cathode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal wiring sputtering apparatus including an inductively coupled RF plasma assisted magnetron cathode suitable for filling a high aspect ratio hole in a metal wiring sputtering process technology such as a highly integrated silicon semiconductor device.
[0002]
[Prior art]
To enable high-aspect-ratio hole filling in highly integrated silicon semiconductor devices, (1) simple planar magnetron sputtering (FIGS. 1 and 2), (2) cathode target and silicon substrate Collimation sputter with a collimator in between (Fig. 3), (3) Long throw spatter with a planar magnetron cathode capable of discharging even at a low pressure of ^10-2 Pa, and widening the gap between the silicon substrate and the target (Fig. 4) , (4) ionized metal plasma sputtering with an RF coil placed between the cathode target and the silicon substrate (FIG. 5; SM Rossnagel et.al .: Appl. Phys. Lett. 63 (1993) 3285 and J. Vac. Sci Technol. B 12 (1994)
449) have been used.
[0003]
In the simple planar magnetron sputtering (normal sputtering) of (1) above, sputtering is performed on the order of 10 ⁻¹ Pa. In this case, the sputtered particles are scattered by the atmospheric gas as indicated by arrow A, and the substrate 3 is incident at a random angle and deposited (FIG. 1). As a result, a large amount of the sputtered film 4 is deposited near the entrance of the high aspect ratio hole, the film cannot be deposited into the hole, and the hole remains hollow (FIG. 2). In FIG. 1, 1 is a substrate holder, and 2 is a target.
[0004]
In the collimation sputtering of (2) above, only the sputtered particles B that form a high angle with respect to the substrate 13 are selected by the collimator 12 placed between the cathode target 10 and the silicon substrate 13, and these particles are selected to have a high aspect ratio. Used to fill ratio holes (FIG. 3). In this case, it is possible to embed holes, but if used for a long time, the thick film attached to the collimator peels off and falls on the substrate 13, so that defects such as disconnection of metal wiring due to particles are likely to occur. Problems occur. In FIG. 3, reference numeral 11 denotes a substrate holder.
[0005]
In the long throw sputtering of the above (3), the planar magnetron cathode 27 that can be discharged even at a low pressure of 10 ⁻² Pa is used, so that the number of sputtered particles C scattered by the atmospheric gas is reduced, and the distance between the silicon substrate 20 and the target 21 is reduced. Can be expanded. As a result, only high-angle particles can fly to the substrate 20 (FIG. 4), and high-aspect-ratio filling is possible. This method is simple in structure and has few problems such as particle formation. However, as the aspect ratio increases, the influence of obliquely incident particles cannot be ignored, and problems such as lower bottom coverage occur. In FIG. 4, 22 is an electrostatic chuck hot plate, 23a and 23b are gas inlets, 24 is an exhaust port, 25 is a low-pressure sputtering magnet, and 26 is a DC power source.
[0006]
In the ionized metal plasma sputtering of (4) above, an RF coil 32 is inserted between the cathode target 30 and the silicon substrate 34 placed on the substrate holder 31, and sputtering is performed by inductively coupled plasma generated by the RF coil 32. The particles are ionized, and further, DC or RF bias 33 is applied to the silicon substrate 34 to introduce the sputtered particles into the high aspect ratio hole, thereby filling the hole (FIG. 5). In this case, the ionization rate can surely be increased (FIG. 6), and it is possible to embed holes with a high aspect ratio. However, since ionization occurs due to gas collision in the reaction chamber, ionization is performed at 10 ⁻¹ Pa level or less. The rate drops sharply (FIG. 6) and the method cannot be applied.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a sputtering apparatus that can solve the problems that have been difficult to achieve with the above-described conventional sputtering method, and that can efficiently fill holes with a high aspect ratio in an ultra-highly integrated silicon semiconductor device.
[0009]
[Means for Solving the Problems]
The metal wiring sputtering apparatus of the present invention is a metal wiring sputtering apparatus that embeds a hole with a high aspect ratio in a silicon semiconductor metal wiring process. The metal wiring sputtering apparatus includes an inductively coupled RF plasma assisted magnetron cathode in a vacuum chamber, and sputters particles with a high ionization rate. Further, the sputtered directional neutral particles and ionized particles by applying a DC or RF bias to a substrate that is generated and applied to a substrate disposed to face a target provided on the front surface of the cathode Is introduced into a hole having a high aspect ratio, and the hole is embedded.
[0012]
When a high aspect ratio hole in a silicon substrate is embedded using a sputtering apparatus with an inductively coupled RF plasma assisted magnetron cathode , the non-ionized neutral particles remain with the characteristics of long low sputtering, and Since the ionized sputtered particles can be perpendicularly incident on the substrate by a DC or RF bias applied to the substrate, it is possible to embed very efficiently even in a high aspect ratio hole. In addition, the ionized particles moderately accelerated by the bias accelerate the migration on the deposited film on the inner surface of the hole by the kinetic energy, and as a result, a film having a fine crystallinity can be deposited.
[0013]
【Example】
Next, examples of the present invention will be described with reference to the drawings. However, these are merely illustrative and do not limit the present invention in any way.
[0014]
FIG. 7 shows the configuration of an inductively coupled RF plasma assisted magnetron cathode provided in the sputtering apparatus of the present invention, and FIG. 8 shows the sputtering shown in FIG. 7 which can efficiently embed high aspect ratio holes in a silicon substrate. The structure of an apparatus is shown. The cathode diameter was 2 inches.
[0016]
As shown in FIG. 8, the sputtering apparatus including the cathode includes a gas introduction port 51 and a vacuum exhaust port 52 for introducing an inert gas such as Ar gas into the vacuum chamber 50. Inside, a target 41 provided on the front surface of the cathode and a silicon substrate 54 held by a substrate holder 53 are provided facing each other. The substrate holder 53 was connected to a DC or RF bias source 55 and further connected to ground so as to be an anode.
[0017]
Next, the ionization rate by the cathode shown in FIG. 7 and the filling of holes with a high aspect ratio performed using the sputtering apparatus shown in FIG. 8 will be described.
[0018]
First, the ionization rate of the sputtered Al particles when the Al target 41 is sputtered using the inductively coupled RF plasma assisted magnetron cathode shown in FIG. 7 will be described. 9 to 10 show the energy distribution measurement results of Al ions. The number of ionized particles is proportional to the area enclosed by the curve and the base. In this measurement, a quadrupole mass spectrometer with a cylindrical mirror type ion energy filter installed at a position of about 130 mm in front of the cathode is used, and the RF power is supplied to the RF coil as shown in FIG. Either inductive coupling or (b) capacitive coupling was performed. 9A shows the case of inductive coupling, and FIG. 9B shows the case of capacitive coupling.
[0019]
In the case of FIG. 9, sputtering was performed with an Ar sputtering gas pressure of 0.13 Pa, a target input power of constant DC 60 W, and an RF coil input power varied. 9 corresponds to the conventional planar magnetron sputtering. On the other hand, it can be seen from FIG. 9 that the number of Al particles ionized can be increased rapidly when high-frequency power is supplied to the RF coil. As for the method of supplying high-frequency power, inductively coupled plasma is more efficient, as can be seen from the comparison between FIG. 9A and FIG. 9B. In addition, since the ionization rate of the conventional planar magnetron sputtering is 0.1% to several percent, the ionization rate by this method is one digit or more larger than that.
[0020]
In the case of FIG. 10, sputtering was performed by changing the Ar sputtering gas pressure while setting the target input power to DC 60 W, the input power to be constant 40 W by the RF coil capacitive coupling connection. From FIG. 10, it can be seen that in this sputtering method, the ionization rate of the sputtered particles can be kept high even at a low pressure of 10 ⁻² Pa. This is a fundamental difference from the ionized metal plasma sputtering (FIG. 6) in which the ionization rate rapidly decreases below 10 ⁻¹ Pa.
[0021]
Next, using the apparatus shown in FIG. 8, high-aspect-ratio holes in a silicon substrate were filled using Ti as a wiring material.
[0022]
After the silicon substrate 54 is set on the substrate holder 53 at a position of about 220 mm below the target 41, the chamber is evacuated to a high vacuum of about 10 ⁻⁶ Pa by a vacuum exhaust system. Thereafter, the substrate 54 is heated from the back to a desired temperature of 250 ° C. by a heater (not shown). After reaching this temperature, Ar gas is introduced into the room through the gas inlet 51 and the sputtering gas pressure is adjusted to 0.065 Pa. Next, plasma is generated by applying power of 30 W to an RF coil having DC 60 W as a target and inductively coupled connection (the end of the RF coil is grounded). In this state, the substrate applied voltage is adjusted so that the substrate bias is constant at DC 20 W, and sputtering film formation is started. The film formation time is calculated from the film formation speed measured in advance, and the film formation is terminated when the desired film thickness reaches about 0.2 μm.
[0023]
In the case of this method, as described above, as a mechanism for embedding Ti in a high aspect ratio hole on the surface of the silicon substrate, an action of attracting a high ionization rate Ti ion vertically to the substrate with a DC bias applied to the substrate, There is an effect that neutral Ti particles that are not ionized by long throw sputtering are incident on the substrate at a high angle. Furthermore, since the ionization rate of Ar, which is a sputtering gas, is high, Ar ions are also drawn perpendicularly to the substrate, but the Ti film deposited near the entrance of the hole and on the wall surface as shown in FIG. Since it is shaved (sputtered), this action also contributes to reduction of Ti film adhesion to the side wall and improvement of film deposition on the hole bottom.
[0024]
The substrate thus formed was taken out of the chamber, and was then broken and observed and measured with a scanning electron microscope in order to examine the degree of hole filling. The measurement results are shown in FIG. In the figure, the bottom coverage is obtained by dividing the thickness of the film deposited on the bottom of the hole by the thickness of the film deposited on the substrate surface. The higher this value, the better the hole filling performance. The figure also shows the results of long throw sputtering as a comparative example with the conventional method. The long throw sputtering here is a result when the power supplied to the RF coil is set to 0 W. From FIG. 12, it can be seen that the hole filling performance of the present invention is superior to that of long throw sputtering.
[0025]
In the above embodiment, Ti is used as the wiring material. However, other metal such as Al, Cu, and W, compound wiring material such as TiN, and high dielectric material such as (BaSr) TiO _3. It is possible to apply to thin films using various materials.
[0026]
Although the silicon substrate metal wiring process has been described in the above embodiment, it is needless to say that the present invention can be applied to various electronic device device thin film manufacturing processes including flat panel displays and thin film magnetic heads.
[0027]
【The invention's effect】
The sputtering apparatus of the present invention equipped with an inductively coupled RF plasma assisted magnetron cathode has made it possible to embed high aspect ratio holes in increasingly more integrated substrates.
[Brief description of the drawings]
FIG. 1 is a schematic side view for explaining conventional planar magnetron sputtering.
FIG. 2 is a schematic cross-sectional view for explaining a state of hole filling by the conventional magnetron sputtering of FIG.
FIG. 3 is a schematic side view for explaining conventional collimation sputtering.
FIG. 4 is a schematic side view for explaining conventional long throw sputtering.
FIG. 5 is a schematic side view for explaining conventional ionized metal plasma sputtering.
6 is a graph showing the relationship between sputtering pressure and ionization rate when the conventional ionized metal plasma sputtering shown in FIG. 5 is used.
FIG. 7 is a schematic side view showing an embodiment of a cathode provided in the sputtering apparatus of the present invention.
FIG. 8 is a schematic side view showing an embodiment of the sputtering apparatus of the present invention.
FIG. 9A is a graph showing the energy distribution of A1 ions sputtered at the cathode provided in the sputtering apparatus of the present invention (high-frequency power supply by inductively coupled plasma).
(B) The graph which shows the energy distribution of A1 ion sputtered with the cathode with which the sputtering device of the present invention is provided (high-frequency power supply by capacitively coupled plasma).
FIG. 10 is a graph (capacitive coupling plasma) showing the sputtering pressure dependence of the A1 ion energy distribution when sputtering is performed using the sputtering apparatus of the present invention.
FIG. 11A is a diagram for explaining a method of supplying high-frequency power to an RF coil by inductively coupled plasma.
(B) The diagram for demonstrating the high frequency electric power supply method to RF coil by capacitive coupling plasma.
FIG. 12 is a graph showing the relationship between the hole aspect ratio and the bottom coverage (%) in comparison with the conventional long throw sputtering method when the sputtering apparatus of the present invention is used.
[Explanation of symbols]
1, 11, 31, 53 Substrate holder 2, 10, 21, 30 Target 3, 13, 20, 34 Substrate 4 Sputtered film 12 Collimator 22 Electrostatic chuck hot plate 23a, 23b Gas inlet 24 Exhaust 25 For low-pressure sputtering Magnet 26 DC power supply 27 Planar magnetron cathode 32 RF coil 33 DC or RF bias 40 Cathode electrode 41 Target 42 RF coil 43 Cathode cover 44 Gas introduction nozzle 45 High frequency power supply 46 Matching box 47 Permanent magnet 48 DC power supply 49 Magnetic field 50 Vacuum chamber 51 Gas inlet 52 Exhaust outlet 54 Silicon substrate 55 DC or RF bias source 56 High aspect ratio hole

Claims (1)

In a metal wiring sputtering apparatus for filling a high aspect ratio hole in a silicon semiconductor metal wiring process, an inductively coupled RF plasma assisted magnetron cathode is provided in a vacuum chamber, and the cathode is attached to an RF coil in front of a planar magnetron target. The periphery of the target and the coil was covered with a cover, and the gas pressure in the vicinity of the target and the coil in the cover was made higher than the pressure in the vacuum chamber outside the cover, and was provided inside the cover and in the vicinity of the target. By spraying a sputtering gas from the gas introduction nozzle onto the target surface, the ionization rate of the sputtered particles can be increased at a low pressure of 10 ⁻² Pa , and the target provided on the front surface of the cathode The base installed to face DC sputtered directional neutral particles and ionized particles are introduced into the high aspect ratio hole by applying a DC or RF bias to the hole, and the hole is embedded. Metal wiring sputtering equipment.

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